SOIL SURVEY OF GUINABASAN WATERSHED IN ASTURIAS, CEBU

SOIL SURVEY OF GUINABASAN WATERSHED IN ASTURIAS, CEBU
AND HILABANGAN WATERSHED IN AYUNGON AND TAYASAN,
NEGROS ORIENTAL, PHILIPPINES



Jade P. Mesias
Assisting Professional on Soil Survey

and


Reynaldo L. Lanuza
Supervising Science Research Specialist



ABSTRACT


Few researches have been conducted dealing with the nature and characteristics of soils in Philippine watersheds despite of their ecological role and importance in watershed ecosystems. This survey characterized the soils of Guinabasan Watershed in Asturias, Cebu and Hilabangan Watershed in Ayungon and Tayasan, Negros Oriental of Central Visayas, Philippines through biophysical assessment, detailed soil profile description and bulk density determination following the standard and modern soil survey methods.

Results revealed that the geology of the sites of Guinabasan Watershed and Hilabangan Watershed are characterized by limestone/karst rock formation and andesitic (volcanic) pyroclastic rocks with alluvial landscapes in the lower elevation. The sloping (steep) or rugged topography of the two watersheds and the high elevation coupled with the abundant rainfall promotes very fast rock weathering and soil formation due to rapid leaching. Unsuitable land use systems and improper soil management strategies, conversion of forests land to agricultural lands, deforestation of sloping lands, quarrying and natural geologic processes make the two watersheds vulnerable to soil erosion, landslides and flooding.

The soils of Guinabasan Watershed and Hilabangan Watershed that are derived from andesitic pyroclastic rocks are very strongly weathered, generally red and deep and at the advanced stage of pedogenesis as evidenced of the presence of argillic and spodic subsurface diagnostic horizons (Bt and Bs), residual accumulation of sesquioxides and occurrence of saprolite layers (Cr). Soils of Guinabasan Watershed that are derived from limestones or karst rocks have cambic subsurface diagnostic horizon (Bw), have thin solum and relatively shallow and have high rock fragments content in the profile. Alluvial soils of the two watersheds have buried genetic horizons (2Ab) and transition horizons, generally deep and have mottles and gleying in the profile. The soil texture of the two watersheds is generally clayey which turn firm when moist and sticky and plastic when wet. Soil color is generally darker in the surface horizons due to organic matter accumulation thus generally making the soil structure granular, friable consistency when moist and as well as generally causing the abundance and dominance of soil pores and roots in these horizons. Soil structure is generally strong and blocky in the subsurface horizons. Degraded sites generally obtained weak grade of soil structure.

The bulk density values of soils of Guinabasan Watershed and Hilabangan Watershed ranges from 1.29 g\cm3 to 1.59 g\cm3 .Bulk density of soils of the two watersheds are generally affected by the soil organic matter content and aggregation, soil texture, surface cover and the land use of the site.

The overall soil survey results indicate that slope position, geochemical characteristic of the andesitic pyroclastic rocks, limestone rocks and alluvium and land-use seem to be the major factors that contributed to the characteristics and pedogenesis of soils in the two watersheds.










INTRODUCTION

Soils are the critical component of landscapes and terrestrial ecosystems. The interaction between the abiotic (geosystem) and the biotic (biosystem) components of ecosystems coupled with human influence (anthropogenic/socio-economic system) produce a soil in an ecosystem. Because soil formation is very slow process (Jenny, 1941), the soil is deemed as a non-renewable natural resource and a fragile component of a certain ecosystems such as watersheds.

Watersheds play a crucial role in providing water sources as well as in mitigating climate change as a result of global warming (O’riordan, 2000). In relation to that role, soil component in a watershed functions as an ecological filter hence cleaning and purifying water and detoxifying environmental pollutants. The problem of climate change is closely linked to the soil. Soil is a significant sink and source of carbon pools in the forest (Lugo and Brown, 1993) and the soil component can also contain as much as carbon as vegetation (Watson et al., 2000).

Watershed areas in the Philippines are heavily exploited for traditional shifting cultivation (swidden system/kaingin), logging, grazing and mining/quarrying activities without considering its effect on the soil resource, thus soil erosion and soil degradation are widespread in the Philippine watersheds (Asio, 1998). These serious environmental problems can be minimized through the employment of soil survey.

Soil survey information has been and well continues to be a broadly applied information source for environmental conservation planning (Tomer and James, 2004). Soil survey is an aid to the conservation of soil. It enables one to identify and determine the characteristics of the soil of a given area, make predictions about the behavior of soils, and recommend appropriate and sustainable soil management and suitable land-use system specific to the prevailing environment.

Thus, there is a need for soil survey to determine the nature and characteristics of soil resource in watersheds particularly in Guinabasan Watershed in Asturias,Cebu and Hilabangan Watershed in Ayungon and Tayasan, Negros Oriental for sustainable watershed management planning and protection. Such survey will also contribute to our better understanding of soils in watershed ecosystems. Currently, no soil survey has been conducted in the mountainous upland landscapes of Negros Oriental province in general and Hilabangan Watershed in particular. In addition, we are not aware of any published soil surveys/researches dealing with the characteristics of soils of the two mentioned watersheds in Central Visayas. The objectives of this survey were to conduct biophysical assessment and determine the characteristics of soils of Guinabasan Watershed and Hilabangan Watershed through detailed soil profile description and bulk density determination.

MATERIALS AND METHODS

A. Pre-Survey of the Target Watersheds

Gathering of Secondary Information

Secondary information such as spatial and temporal data of the target watersheds such as topographic map, slope map, climate map, geologic map, geologic age map, land use and land classification map, and old soil map of Guinabasan Watershed in Asturias, Cebu were secured using ArcView GIS from the Ecosystems Research and Development Service of the Department of Environment and Natural Resources of Region 7 (ERDS-DENR Region 7). The secondary maps were studied thoroughly as a basis in deciding the soil sampling unit in the watershed.

For the Hilabangan Watershed, secondary maps and data were provided by the CENRO Ayungon with the used also of GIS.

Soil Survey Sites

The soil survey sites covered the different barangays of Asturias, Cebu and Ayungon and Tayasan, Negros Oriental within the catchment area of the Guinabasan Watershed and Hilabangan Watershed, respectively (Figure 1 and Figure 2).

B. Conduct of Survey Proper

Field Methods

Location of Soil Profiles (Sampling Unit) as well as Site Assessment and Soil
Profile Description

The Dokuchaev-Jenny model of soil formation, that is soil property/characteristic is a function of climate, parent material, time, organism (vegetation/landuse) and relief (elevation/topography/slope position) expressed as Sc=f(cl,pm,tm,or,rf). It was used as the theoretical basis in deciding the sampling unit and positioning soil profile within the Guinabasan Watershed. This was mainly based on the detailed examination and analysis of the gathered secondary data and maps.

The GIS-based soil map showing the different soil types provide a good basis in deciding the sampling unit and for the Dokuchaev-Jenny Model of Soil Formation to be applied in the landscape since this combined the five factors of soil formation upon classifying the soil in into different soil series, soil type and soil phase. Thus, five soil profiles were selected and positioned in the GIS-based soil map of Guinabasan Watershed and were located on the field using Global Positioning System (GPS). However, according to the method of Rosario (1987), soil moisture, fertility and erodibility on watersheds are generally affected by elevation, vegetation and physiographic\slope position. Thus, two soil profiles of the same soil series were sited on different elevation (Soil Profile 2 and 5), vegetation (Soil Profile 5) and physiographic\slope position (Soil Profile 2).



































Since mountain soils of Negros Oriental province in which the watershed was located were not yet surveyed (Barrera and Jaug,1960), location of soil profiles in the Hilabangan Watershed were based on the major land uses or vegatation and physiographic\slope position under different elevations according to the method of Rosario,1987.

The sites and soil profiles were fully characterized and described in the field (Figure 3) following the standard and modern soil survey methods according to the National Soil Survey Center of the Natural Resources Conservation Service of the United States Department of Agriculture (Schoeneberger et al., 1998).

Soil Sampling and Preparation of Characterization Samples

With the aid of soil auger, borings were made on the proposed soil sampling unit (Figure 4). Morphological characteristic specifically soil texture (by feel method) on each auger sample was determined (Mesias, 2007).

Soil pits with a surface area measuring 1m x 1m and having a depth of at least 1m were dug manually at representative sites. Each profile was dug in such a way that one of the sides of the pit faces the sun for proper ocular characterization (Mesias, 2007). Boundaries between soil horizons were marked for proper characterization and then photographed.

Since this is a pedological field survey, the horizon is the basic sampling unit. Thus, 1 kg soil sample was collected from each genetic horizon from excavations for sufficient physical and chemical soil analyses. Sampling was done with the use of a knife starting from the lowest layer going up to avoid contamination (Mesias, 2007). Samples were placed separately in properly-labeled plastic bags. Undisturbed clods were collected in the surface horizons (A) for bulk density determination. The clods were placed in properly labeled plastic bags and transported carefully to the laboratory. In addition, rock samples were collected in each soil characterization site for identification in the Mines and Geosciences Bureau of the DENR-7.











Figure 3. Photograph showing the soil surveyor conducting detailed characterization
of the exposed soil profile in Hilabangan Watershed




















Laboratory Methods

The bulk soil samples collected in each genetic horizon (excluding the samples\clods for bulk density determination) were brought to the Regional Soils Laboratory of the Department of Agriculture Region 7 in Mandaue City for air drying and analysis for the following soil parameters:

1. Particle Size Distribution
2. Soil pH
3. Soil Organic Matter
4. Cation Exchange Capacity(CEC)
5. Exchangeable Acidity
6. Electrical Conductivity
7. Total Nitrogen(N)
8. Available Phosphorus(P)


For Guinabasan Watershed clod samples, bulk density determination was conducted by the author in the Environmental Management Bureau Laboratory (EMB Laboratory) of the Department of Environment and Natural Resources Region 7 and for Hilabangan Watershed clod samples the author conducted it in the Regional Soils Laboratory of the Department of Agriculture Region 7.

Bulk Density

This was determined by the paraffin clod method (Black, 1965 and USDA-NRCS, 1996). The samples were replicated three times for the Guinabasan Watershed due to limited clods and Hilabangan Watershed samples were replicated five times. Briefly, undisturbed air dried soil clod about 2 inches in diameter was tied securely and weighed in air. Then the soil clod was dipped in melted (hot) paraffin. The coated paraffin clod was weighed in air and then weighed in water. The gravimetric moisture content of the clod was also determined. The bulk density (BD) was then computed using Equation 1:


Ms
Bulk Density = -------------- (1)
Vt
where :
Ms = Mass of solids or the oven-dry weight of clod (g)
Vt = Total volume of clod



RESULTS AND DISCUSSION

A. Biophysical Assessment and Soil Profile Description
Guinabasan Watershed Soils

Soil Profile 1 (Baguio Series-Middleslope/Backslope)

Geomorphology and Site Characteristics of Soil Landscapes. The geographical location of the characterization site is in Brgy. Baye, Asturias, Cebu at approximately 590166 E and 1170180 N at an elevation of 319 m above sea level. Its geomorphic position is in the backslope of the mountainous area of Guinabasan Watershed (Figure 5). The geology of the site is characterized by volcanic (igneous) rock formation specifically andesite. The topography of the site ranges from moderately sloping (moderately steep) to rolling with a linear concave slope. This explains the well drained condition of the soils in the site. The vegetative cover of the site is composed of grass fallow, herbaceous, shrubs, coconut cover and secondary forest.. The site is slightly eroded due to the mentioned vegetative cover which lessens the impact of rainfall. Climatic type of the site is Type IV implying that there is no maximum rain period and no distinct dry season, also rainfall is more or less evenly distributed throughout the year (Coronas, 1920). Soil moisture and temperature regimes are udic and isohyperthermic, respectively (Soil Survey Staff, 1992).
Soil Morphological Characteristics. The soil in middleslope/backslope of the mountainous area of Guinabasan Watershed that was derived from andesite is characterized by a horizon sequence of Ap-Bt-Cr1-Cr2-Cr3 profiles (Figure 6). This indicates that the soil is strongly weathered as evidenced of the presence of argillic subsurface diagnostic horizon (Bt). The presence of thick saprolite layer (Cr) implies weathered parent rock material. The soil is moderately deep and thick with a depth ranging from 0-58 cm+, this is a typical characteristic of a very old and strongly weathered soil. Soil color is dark brown (7.5YR 3/3) on the Ap horizon probably due to accumulation of organic matter in this horizon and becomes reddish brown (5YR 5/3) to brown (10YR 4/3) on the subsurface horizons due to iron oxide coatings and decrease amount of organic matter content with depth. It has a strong fine angular blocky soil structure in the Ap and Bt horizons due to humus and silicate clay accumulation as well as due to the clayey soil texture. Soil structure becomes weak fine angular blocky in Cr horizons due to the presence of strongly weathered andesite. The consistencies of the soils in Ap and Bt horizons are slightly hard to hard when dry, friable and firm when moist and very sticky and very plastic when wet because of the high clay content and due to the contribution of soil organic matter. The decrease of clay content and organic matter with depth and the presence of saprolite are probably the reasons for the soil consistency to become extremely hard when dry, firm when moist and slightly sticky to moderately plastic when wet in Cr horizons. Root distribution decrease with depth and is limited only in upper 24 cm of the profile due to the presence of saprolite in lower horizons which reduces root proliferation. Soil pores are characterized as many fine to very coarse tubular pores in first two horizons since these were the root zones and also it is in these horizons where soil flora and fauna are active. It becomes very few to very fine irregular pores in the saprolite layer. Common rock fragments are observed in the Cr horizons since these horizons are closer to its parent material, implying unconsolidated earthly material and soft bedrock. Horizon boundaries are characterized by gradual and smooth which suggest a well developed soil profile, an indication that the soil is very strongly weathered.






















Soil Profile 2 (Baguio Series-Upperslope/Shoulder)

Geomorphology and Site Characteristics of Soil Landscapes. The site is geographically located in Brgy. Baye, Asturias, Cebu at approximately 590913 E and 1170777 N at an elevation of 131 m above sea level. Its geomorphic position is in the upperslope/shoulder of the upland area of Guinabasan Watershed (Figure 7). Baguio clay loam is the soil type of the site according to Barrera et al. (1954). The geology of the site is characterized by volcanic rock (andesite). The topography of the site ranges from moderately sloping (moderately steep) to rolling with a linear convex slope. The rugged topography of the site explains the well drained condition of the soils. The vegetative cover includes grasses, herbaceous, broadleaf weeds and trees in a secondary forest. Soil erosion in the site is slight due to the mentioned vegetative cover which lessens the impact of rainfall. Coronas (1920) characterized the climate as Type IV that implies that there is no maximum rain period and no distinct dry season, also rainfall is more or less evenly distributed throughout the year. Soil moisture and temperature regimes are udic and isohyperthermic, respectively (Soil Survey Staff, 1992).

Soil Morphological Characteristics .The soil in the upperslope/shoulder of the andesite hill and mountainous upland of Guinabasan Watershed has the following horizon sequence: Ap-Bt-Cr-R profiles (Figure 8). Same with soil profile 1, the presence of argillic subsurface diagnostic horizon (Bt) and saprolite layer (Cr) suggests that the soil is strongly weathered. The exposure of bedrock layer (R) and the depth of soil which is relatively shallow as compared to soil profile 1, is largely the influence of slope position .In other words, the observed differences in profile development and morphological characteristic in spite of the uniformity of parent material and climate between soil profile 1 and soil profile 2 is largely the effect of the differences in elevation and slope position as a factor of soil formation. For instance, the relatively shallow soils in the shoulder slope position (Soil Profile 2) reflects the influence of slope on water movement, which in turn determines the rates of weathering, soil erosion and soil formation (Gerrard, 1992; Daniels and Hammers, 1992; Hall, 1983).Thus, soils on the shoulder position produced moderately shallow (Jahn et al., 2002) soil ranging from 0-48 cm. The soil color is brown (10YR 4/3) in the Ap horizon due to accumulation of organic matter in this layer and dark reddish brown (2.5YR 3/3) in Bt horizon and dark red (2.5YR 3/6) in Cr horizon due to iron oxide coatings in the soil matrix .Soil structure is characterized as strong fine sub-angular blocky in surface horizon (Ap) and strong fine angular blocky in subsurface horizons (Bt and Cr) suggesting the decrease of soil organic matter content indicating the very important role of soil organic matter in soil structure formation and aggregation. Soil consistency is characterized by a slightly hard consistence when dry, friable when moist and sticky and plastic when wet probably to the contribution of clay. Root is characterized as many to very fine in surface horizons and distribution decreases in subsurface horizons suggesting increasing limitation to root penetration. Soil pores are characterized as very fine tubular and many in Ap horizon and few medium tubular pores in Bt horizon since these are the rooting layers. Rock fragments are common in Cr horizons due to the presence of weathered parent rock material; this might also be the reason for the soil pores to become very few to very fine irregular pores. Horizon boundary is wavy abrupt in Ap horizon and smooth clear in Bt and Cr horizons suggesting weak profile development due to the influence of slope characteristics in soil profile development.
































Soil Profile 3 (Faraon Series-Crest/Summit)

Geomorphology and Site Characteristics of Soil Landscapes. The soil characterization site is geographically located in Brgy. Sta. Rita, Asturias, Cebu at approximately 586051 E and 1173101 N at an elevation of 150 m above sea level. Its geomorphic position is in the crest/summit of the sedimentary hill of a karst landscape (Figure 9). The soil type of the site is Faraon clay steep phase according to Barrera et al. (1954). Soil formation in the site is at very young stage, apparently to due youthfulness of the limestone and instability of geomorphic surfaces (Mesias, 2007) .The topography of the site ranges from moderately sloping (moderately steep) to rolling with a linear convex slope. The drainage of the soils in the site is well drained due to its underground drainage systems or solutional cave systems in this karst landscape. The vegetative cover of the site is grassland with cogon (Imperata cylindrica), broadleaf weeds and a secondary forest. The sight is slightly eroded due to the mentioned vegetative cover which lessens the impact of rainfall. Climate is characterized as Type IV (Coronas, 1920) implying that there is no maximum rain period and no distinct dry season, and rainfall is more or less evenly distributed throughout the year. Soil moisture and temperature regimes are udic and isohyperthermic, respectively (Soil Survey Staff, 1992). Surface rock fragments are characterized as Class 4 suggesting that it is extremely rocky and stony with sufficient stone and rock outcrops which covers 15% to 90% of the site.

Soil Morphological Characteristics. Soil is described as poorly developed and relatively young as indicated by the Ap-Bw-C-R profiles (Figure 10). The results concur with the literature stating that that soils from limestone vary from poorly to well developed (Buol et al., 1997; Mesias, 2007). The soil has also cambic subsurface diagnostic horizon (Bw) suggesting young and weak development as evidenced of the color and structural development. This clearly implies that the soil is at the early stage of pedogenesis. Based on the rating of scale for ecological evaluation of the soils, it appears that the soil depth is very shallow ranging from 1 - 30 cm (Jahn et al. 2002). In addition, the solum is very thin (13 cm). The Ap horizon is dark brown (10YR 3/3) due to high accumulation of organic matter from the decaying roots of grasses that grows in the site. It becomes dark yellowish brown (10YR 4/4) in Bw horizon implying weak development of color and probably due to the decrease of soil organic matter content with depth. The C horizon has yellowish brown color (10YR 5/4) reflecting the nature of the weathered parent material. Soil structure in Ap horizon is strong medium granular due to the high organic matter. This suggests the very important contribution of organic matter in soil structure formation and aggregation. In addition, the strong medium granular structure is due to the formation of stable complexes between calcium and humus. It becomes moderate fine angular blocky in Bw horizon suggesting soil structure development. The high clay content of this relatively young soil makes the consistency of this soil slightly hard when dry, friable and firm when moist and sticky and plastic when wet. Additionally, the friable consistency when moist is due to the high organic matter content in the surface horizon (Ap). Many and fine roots were noted in Ap and Bw horizons due to the presence of grasses. Roots are few in the C horizon suggesting that root penetration is restricted due to the abundance of rock fragments. Thus, many fine tubular pores are common in the surface horizons (Ap and Bw) and few coarse tubular in C horizon. Soil horizon boundary characteristics are smooth abrupt in Ap, clear gradual in Bw and clear smooth in C horizon implying that this soil has very little profile development due to its young in nature (Mesias, 2007).















































Soil Profile 4 (Mandaue Series-Toeslope)

Geomorphology and Site Characteristics of Soil Landscapes. The geographical location of the soil characterization site is in Brgy. Sta. Lucia, Asturias, Cebu at approximately 582367 E and 1175837 N at an elevation of 20 m above sea level. The geomorphic position is in the toeslope of the floodplain of the Guinabasan Watershed fluvial landform (Figure 11). Mandaue clay loam is the soil type of the site (Barrera et al., 1954).The geologic parent material of the soils in the site is river alluvium from the Guinabasan River. Its topography is almost flat. This explains the poorly drained condition of the soils in the site as evidenced of the presence of mottles in the soil profile. The site is utilized for agricultural \crop production and previously planted with corn and cassava. Presently the site is dominated with grasses, coconut and banana. Since the site is in the floodplain, deposition of sediments is observed in the area. Hence, soil erosion is only slight. Same with other characterization site, climate is characterized as Type IV (Coronas, 1920) implying that there is no maximum rain period and no distinct dry season, and rainfall is more or less evenly distributed throughout the year. Soil climate are characterized as udic soil moisture regime and isohyperthermic soil temperature regime (Soil Survey Staff, 1992). Stones and rock outcrops are not observed in the site.

Soil Morphological Characteristics. The sequence of horizons which is Ap-AC-C-2Ab profiles of the soil in the floodplain of Guinabasan River suggests that the pedogenesis is inhibited due to recent alluvium deposits (Figure 12). Hence, the soil was not able to develop a B horizon. In other words, pedogenesis is greatly inhibited due to disturbance of the natural geologic processes specifically floods thus preventing horizon development. The presence of the buried genetic horizon (2Ab) suggests that the uppermost horizons of the soil profile are alluvial deposits. Transition horizon (AC) occurrence in the profile means that this horizon has dominantly A horizon characteristic but also contains some characteristics of C horizons implying that probably organic matter has accumulated in this sediment layer. Mottles are observed in the profile suggesting that there is a fluctuation of water table during the rainy season. It has a reddish brown color (2.5YR 5/4) and characterized as many and prominent. Soil color is very dark gray (10YR 3/1) in the Ap horizon due to the accumulation and deposition of organic matter from the sediments. It becomes grayish brown (10YR 5/2) to reddish brown (5YR 4\4) in subsurface horizons due to the decrease of organic matter content with depth. Soil structure in this soil is generally blocky due to the clay sediments and humus complexes that cement particles together into blocky structure. Consistency of the soil is generally slightly hard when dry, friable when moist and slightly sticky to slightly plastic when wet probably because of the coarser texture or sandy texture, which is a typical characteristic of an alluvial soil. Root distribution decreases with depth suggesting that only in Ap and AC horizons plant roots can extract soil nutrients. Soil pores can be characterized as medium to coarse tubular and abundant in the Ap and AC horizons since these were the root zones. Boundary characteristic of the horizon is smooth diffuse in Ap and AC horizons which reflect both the influence of cultivation and sedimentation process in alluvial floodplain of the Guinabasan River. It becomes smooth abrupt in the buried horizon due to the occurrence of lithologic discontinuity.

















































Soil Profile 5 (Mandaue Series-Toeslope)

Geomorphology and Site Characteristics of Soil Landscapes. The geographical location of the soil characterization site is in Brgy. Old Bago, Asturias, Cebu at approximately 585415 E and 1174785 N at an elevation of 51 m above sea level. Same with Site 4, it is geomorphologically positioned in the floodplain of the fluvial landform of Guinabasan Watershed with flat topography (Figure 13). The soil type of the site is Mandaue clay loam according to Barrera et al. (1954). It was derived from recently deposited alluvium from the Guinabasan River. Soils in the site are poorly drained as evidenced of the presence of mottles in the exposed soil profile. The site is utilized as a coconut plantation with banana and cassava as intercrops with dominant grasses infesting the mentioned crops (Figure 13). Erosion and deposition of sediments from the swelling river are evident in the exposed profile. Climate is characterized as Type IV (Coronas, 1920) implying that there is no maximum rain period and no distinct dry season, and rainfall is more or less evenly distributed throughout the year. Soil climate are characterized as udic soil moisture regime and isohyperthermic soil temperature regime (Soil Survey Staff, 1992).

Soil Morphological Characteristics. This soil is characterized by Ap-AC-CA-2Ahb soil horizonation (Figure 14).The presence of A master horizon in all layers suggests that sediments from the alluvial deposits carry sufficient amount of organic matter that is probably coated in the particles and aggregates of the alluvium. Transition horizons (AC and CA) and the buried genetic horizon with alluvial accumulation of organic matter (2Ahb) imply that the pedogenesis of the soil is really affected by the natural geologic processes such as flooding and river swelling. The mentioned natural geologic processes enhanced the sedimentation process in the alluvial floodplain of the Guinabasan River, thus preventing horizon development. Soil depth is relatively deep, a typical characteristic of an alluvial soil. The coloration of the soil which is very dark gray (10YR 3/1) to dark gray (10YR 4/1)in the horizons above the buried genetic horizon imply deposition and accumulation of organic matter rich sediments deposited from the upper slopes and again from the river sediments that carry humic particles. Soil structure is strong fine sub-angular blocky in the Ap horizon and strong fine angular blocky in the subsurface horizon. This is probably due to the strong aggregation of the soil particles. Soil consistency is friable in Ap and 2Ahb due to the contribution of organic matter in these horizons. It is firm when moist and slightly sticky to sticky and slightly plastic to plastic when wet probably because of the clay texture of this soil. Mottles were observed in the profiles suggesting that water table is high during rainy season. Roots are generally abundant in the surface horizons and become very few in the subsurface horizons. The same with roots, soil pores are characterized as many fine tubular in the surface horizons due to the abundance also of roots in this layer. Horizon boundary is characterized as smooth diffuse in the first two horizons and becomes smooth abrupt in the CA horizon due to sedimentation process and abrupt change of the geologic parent material.














































Hilabangan Watershed Soils

Soil Profile 1 (Grassland/Pastureland-Lower Backslope)

Geomorphology and Site Characteristics of Soil Landscapes. The site is geographically located in Brgy. Linao, Tayasan, Negros Oriental at approximately 504574 E and 1094709 N at an elevation of 503 meters above sea level. It is geomorphologically positioned in the lower backslope of the andesitic hill of the mountainous upland landscape of Hilabangan Watershed (Figure 15). The soils in the site are still unclassified (Barrera and Jaug, 1960: as cited by Fernandez and de Jesus, 1980). But these soils are clearly developed from the residual material derived from extrusive igneous\volcanic rock specifically andesite as manifested in its profile characteristics. Grasses particularly carabao grass, cogon (Imperata cylindrica), hagonoy (Chromolaena odorata) and few Mangium tree are the vegetative cover of the site. The dominance of cogon and hagonoy in the site is an indicator that the area is degraded. The topography\slope of the site is steep with a linear convex slope shape and despite of that it is still utilized for grazing, thus contributing to the severe erosion of the area as evidenced by the exposure of bedrock as well as on the very thin solum of the profile due to the poorly drained condition and excessive surface runoff enhancing the removal of the surface soils. Soil moisture and temperature regimes are udic and isohyperthermic, respectively (Soil Survey Staff, 1992).

Soil Morphological Characteristics. Pedogenesis of this soil is inhibited due to the conversion of the area from forestland to grassland/pastureland thus interrupting the pedogenic processes resulting to Ap-Cr-R profiles (Figure 16). Based on the rating scale use for the ecological evaluation of soils, the solum is extremely shallow (Jahn et al., 2002) ranging from 0-6 cm and at 6-60 cm depth saprolite and bedrock are expose. This is probably the effect of severe erosion in the site due to the mentioned land-use system and the absence of tree vegetation in the area. Soil color is black (10YR 2/1) in Ap horizon due to the coatings of humified organic matter from the decaying roots of grasses. It becomes dark brown (10YR 3/1) in the saprolite layer due to the decrease of organic matter content with depth. Soil structure grade was characterized as weak both in Ap and Cr horizons suggesting weak structure formation due to the compact condition of the soil as the result of trampling. The compact soil condition of the site greatly affect soil water and air movement hence affecting soil microorganisms activity that are responsible for structure and aggregate formation. Granular structure and friable consistence in the surface horizon can be attributed to organic matter accumulation. Soil structure becomes angular blocky and consistence becomes firm in subsurface horizon due to clay accumulation from the residue of weathering. The sticky and plastic consistency of this soil when wet is probably due to the clay content of this soil. Obviously, roots were many and fine in the Ap horizon since this is the root zone and becomes very few to very fine in the Cr horizon due to saprolite suggesting limitation to root penetration. Soil pores are characterized as many fine tubular in the surface horizon probably because of the high biologic activity in this layer. It becomes very few to very fine irregular in the Cr horizon due to the presence of the weathered parent material. Rock fragments are observable both in Ap and Cr horizons and the abundance increase as it is closer to the parent rock suggesting that those rock fragments are remnants of the weathered parent rock. Soil horizon boundary is characterized as clear and broken due to the influence of severe erosion in the site that inhibits profile development.
















































Soil Profile 2 (Dipterocarps Forest-Upper Backslope)

Geomorphology and Site Characteristics of Soil Landscapes. The site is geographically located in Brgy. Mabato, Ayungon, Negros Oriental at coordinates 9°50’31.14” and 123°2’31.23” at an elevation of 652 masl. The landuse is natural forest dominated by dipterocarps (Figure 17). Its geomorphic position is in the upper backslope of the andesitic mountainous landscape of Hilabangan Watershed. Soils are derived from andesite, an extrusive igneous rock. The topography of the site is steep with 30°-40° slope gradient and a curvilinear slope shape. The degree of erosion is very slight suggesting that almost no evidence of accelerated soil erosion is recognized due to the undisturbed nature of the dipterocarps forest. This implies the very important role of undisturbed forest in minimizing accelerated and geologic soil erosion. The site is well drained as indicated by the absence of mottling in the profile. Soil moisture and temperature regimes are udic and isohyperthermic, respectively (Soil Survey Staff, 1992), a typical characteristic of soils in the humid tropical forests.

Soil Morphological Characteristics. Soils in the dipterocarp forest of the Hilabangan Watershed are characterized by a soil horizonation of Oe-Ah-Bs1-Bs2-Cr profiles (Figure 18). The undisturbed nature of dipterocarp forests enable to develop organic material of intermediate decomposition (Oe) which comes from the leaf litters in the forest floor. It also enable to form an A horizon with illuvial accumulation of organic matter (Ah) being undisturbed nature. Probably, the high accumulation of humified organic matter in Oe and Ah horizons tend to form humic and organic acids which are responsible for the bleaching of the two upper mineral horizons (Oe and Ah) as reflected in the color of the soil matrix. The occurrence of spodic subsurface diagnostic horizons (Bs1 and Bs2) is due to leaching and illuviation of organic acids and sesquioxides out of the surface horizons and translocated downward and accumulated in the B horizon. This suggests that soils of the undisturbed dipterocarp forest of Hilabangan Watershed undergo podzolization. Solum depth is relatively thick as shown in Figure 18. Even though organic matter accumulation is high, soil color is not blackish and its value and chroma increases with depth (10YR 3/4 to 10YR 6/8). It also fades with increasing depth in the profiles because of the decrease of organic matter content and rapid process of podzolization and weathering. Soil structure formation in Oe and Ah horizons is characterized as strong medium granular due to high accumulation of organic matter and high microbial activity specifically soil fungi that are dominant in forest soils contributing to strong structure and aggregate formation. It becomes moderate to strong, medium angular blocky in Bs horizons due to podzolization. Structure in the saprolite becomes massive due to partly weathered parent rock under intermediate weathering. The soil consistence when moist is friable and firm to extremely firm in subsurface horizons due to clay accumulation and the presence of saprolite. The soil consistence when wet is slightly sticky to slightly plastic and becomes very sticky to very plastic with increasing depth probably due to increase clay content except in Cr horizon which is slightly sticky and slightly plastic due to saprolite. Soil pores are many (abundant), fine, tubular and vesicular in Oe and Ah horizon suggesting high biologic activity due to abundant humus and it becomes very few, fine to medium tubular due to decrease of biologic activity. Roots are few to very few and fine to medium in the profile probably because dipterocarp species are deep rooted concentrating their root systems below the profile. Horizon boundaries are characterized as clear to gradual smooth in the first three horizons and become wavy abrupt due to enhanced pedogenesis as a result of undisturbance.














































Soil Profile 3 (Mangium Tree Plantation-Shoulder)

Geomorphology and Site Characteristics of Soil Landscapes. The site is geographically located in Sitio Ilaya, Brgy. Tambo, Ayungon, Negros Oriental at approximately 506891 E, 1092731 N at an elevation of 507 meters above sea level. It is utilized for Mangium tree plantation The geomorphic position of the site is in the shoulder of the andesitic hill of the mountainous landscape of Hilabangan Watershed (Figure 19). The geology of the site is characterized by andesite rock formation. Hence, this also serves as the parent rock of the soils in the site. Due to the moderately steep topography of the site with convex linear slope shape, the drainage of the soils in the site is well drained. The mentioned topography also explains the occurrence of slight erosion in the area. Same with other sites, soil moisture and temperature regimes are udic and isohyperthermic (Soil Survey Staff, 1992).

Soil Morphological Characteristics. Soils in the Mangium tree plantation of Hilabangan Watershed that was derived from volcanic rock (andesite) are characterized by a soil horizonation of Ap-AB-Bto-BCto-Croc profiles (Figure 20). Such horizonation suggests that these soils are in a more advanced stage of pedogenesis as evidenced of the thick B master horizons with illuvial accumulation of silicate clay and residual accumulation of sesquioxides (Bto and BCto) and as well as of the presence of moderately weathered saprolite with residual accumulation of sesquioxides and black iron stone nodules (Croc). In other words, such profile characteristics suggests that these soils are very old and strongly weathered. Interestingly, clay skins or cutans were observed in Bto and BCto subsurface horizons implying that these thin clay skins particle coatings are probably of clay minerals with iron oxides and hydroxides on ped faces. The soil is very deep, a typical characteristic of soil in a highly weathered soil landscape. Soil color is obviously darker in Ap and AB horizons (10YR 3/2 to 10YR 4/4) due to high organic matter accumulation in these horizons. Reddish coloration of soils (10YR 4\6 -7.5YR 4\4 -5YR 4/6) suggests that these soils undergo laterization, thus forming laterites (red soil). As can be seen in the profile (Figure 20), sesquioxides are evident in the profile (orange like coloration) probably these are coatings of iron oxides and hydroxides on the mineral grains. Those black colors that appear in the lower portion of the profile are black iron stone nodules. The high clay content or clayey soil texture of this soil makes the soil structure moderate to strong, medium to coarse and blocky in all horizons. Illuvial accumulation of silicate clay and residual accumulation of sesquioxides makes the consistence of soil to be firm when moist and sticky to very sticky and plastic to very plastic when wet. The friable consistence when moist in Ap and AB horizons is due to the contribution of organic matter. Distribution of roots and pores in the profile are characterized as few to very few and fine to very fine probably because of the decrease pedoturbation and biological activity due to the acidic condition and aluminum toxicity (Sparks, 2003). Soil horizon boundary is clear smooth due to obvious change in coloration because of organic matter accumulation and becomes abrupt smooth in second horizon due to the presence of AB transition horizon and gradual to diffuse wavy in the Bto and BCto horizons suggesting advance stage of pedogenesis.


















































Soil Profile 4 (Rice Paddy field/Pastureland-Terrace)

Geomorphology and Site Characteristics of Soil Landscapes. The site is geographically located in Brgy. Bago, Tayasan, Negros, Oriental at bearing S40°W of about 100 meters from the steel bridge of the mentioned barangay (9°55’10.59”,123°0’50.18” at an elevation of 258 meters above sea level. Its geomorphic position is in the andesitic terrace of the fluvial landform of Hilabangan Watershed of flat\almost flat topography (Figure 21). The soils in the site are derived from the andesitic terrace (old alluvial) deposits with rice and grasses (weeds) as the land cover. The drainage of the soils in the site is characterized as poorly drained as indicated by the presence of mottles and gleying in the profile. Degree of erosion in the area is severe due to floods from the swelling Hilabangan River eroding the original surface soils. Such flooding contributes to the deposition of sediments in the landscape. Soil climate are characterized as udic soil moisture regime and isohyperthermic soil temperature regime (Soil Survey Staff, 1992).

Soil Morphological Characteristics. Soils in the terrace of the fluvial landform of Hilabangan Watershed that are utilized for rice farming and grazing are characterized by Ap- Bw- Cg- 2Bgb- 2Crgb profiles (Figure 22). Natural geologic processes such as seasonal flooding and swelling of Hilabangan River are the probable reasons for the occurrence of lithologic discontinuity and buried genetic horizons (2Bgb and 2Crgb) suggesting that the overlying horizons are sediments from old alluvial deposits. Compared with the soils in the floodplain, soils in the terrace are not frequently disturbed by frequent flooding. Thus, these soils are at the beginning stage of pedogenesis as evidenced of the presence of cambic subsurface diagnostic horizon (Bw). The poorly drained condition of the soils in the site is the main reason for the occurrence of mottling and gleying (g) implying oxidation-reduction chemical process is occurring in these soils. The depth of soil is thick of about 66 cm+, a typical characteristic of alluvial soil. As can be seen in the profile (Figure 22), the coloration of soil in the profile is very distinct. Soil color from Ap to Bw is 10YR 2/1 to 10YR 3/2 implying that that there is a weak development of color in the profile. Soils in the Cg to 2Bgb have blackish coloration (10Y 2.5/1).Such coloration, is an indicator of wetness because of the reduction chemical process. Since there is gleying, organic matter break downs slowly and the extra organic matter accumulated darkens the soil. While in the buried saprolite layer soil color is 10YR 4/3, although reduction process\gleying occur it is not enough to make this layer totally a gleyed horizon. The weak grade of soil structure in Ap horizon is due to the effect of continuous grazing. It becomes moderate to massive in the Bw to 2Crgb due to weak profile development and of the saprolite layer. The high clay content of the soils (clay texture) makes the soil structure angular blocky and medium in all horizons as well as make the consistence of soils to be slightly sticky and slightly plastic to very sticky and very plastic when wet and firm to extremely firm when moist. Friable consistency when moist in Ap horizon is due to the accumulation of organic matter from the decaying roots of the grasses. Roots observed are many to few and of very fine size suggesting decrease of root distribution with depth. Soil pores are generally tubular and characterized as many and very fine both in Ap and Bw implying that biologic activity and pedogenic processes are active in these horizons. It becomes few and very fine in horizons with enough gleying. Soil horizon boundaries are characterized as diffuse to gradual smooth from Ap to Bw due to weak profile development and becomes abrupt wavy in the last two horizons because of sedimentation and lithologic discontinuity.















































Soil Profile 5 ( Sugarcane Plantation-Summit)

Geomorphology and Site Characteristics of Soil Landscapes. The site is geographically located in Brgy. Hilabangan, Tayasan, Negros Oriental at approximately 9°56’46.28”, 123°4’26.81” at an elevation of 491 meters above sea level. Its geomorphic position of the site is in the summit of the andesitic hill landform of the mountainous landscape of Hilabangan Watershed. The topography of the site is sloping with 10°-15° slope gradient having a convex linear slope shape making the drainage of the soils in the site as well drained. Soils in the site are residual material derived from andesite with sugarcane plantation as the land use and vegetative cover (Figure 23).Conversion of forest land to agricultural land such as a sugarcane plantation of continuous cultivation make the soils in the area susceptible to erosion. Thus, the site is severely eroded as evidenced of the andesite rock outcrops in the site. Soil moisture and temperature regimes are udic and isohyperthermic,respectively (Soil Survey Staff, 1992).

Soil Morphological Characteristics. The soils in the sugarcane plantation of Hilabangan Watershed are characterized by Ap-Bhs-Bto-Cro profiles. This implies that these soils undergo advance stage of pedogenesis. The soil is able to develop an illuvial accumulation of organic matter (h) in the B horizon since the pit is located in the undisturbed portion of the sugarcane plantation. Sesquioxide coatings are evident in all horizons of the exposed profile but it is dominantly accumulated in the Bhs and Bto horizons. Clay skins (cutans) are observed in the Bto horizon suggesting that these soils undergo extensive pedogenic processes. The soil is moderately deep an indication that this soil is strongly weathered. Soil color is generally reddish (Figure 24) implying that this coloration is due to the product of laterization, thus producing laterites (red soils). The high clay content of the soil might be the probable reason for the formation of angular blocky soil structure.

It might also be the reason for the weak structure grade formation in the upper two horizons since it slow down water movement thus affecting soil microbial activity. Soil structure grade becomes strong in Bto and Cro horizons due to illuvial accumulation of silicate clay and residual accumulation of sesquioxides; it becomes moderate in Cr due to the presence of moderately weathered saprolite. The consistencies of the soil are friable when moist in Ap horizon due to organic matter accumulation and firm to extremely firm in subsurface horizons due to clay accumulation. The sticky to very sticky and plastic to very plastic consistencies of the soil when wet are a clear indication of the high clay content of these soils. Roots and tubular pores are dominant in Ap horizon and the distribution and dominance decrease with depth implying that biological activities are concentrated in the surface horizons with organic matter and humus accumulation. Soil horizon boundaries are characterized as clear smooth to diffuse wavy suggesting that these soils are highly weathered and of advanced stage of pedogenesis and profile development.















































B. Bulk Density

Bulk density is defined as the mass o f a unit volume of a dry soil (105°C). This volume includes both solids and pores and thus, bulk density reflects the total soil porosity. Bulk density is an important parameter for the description of soil quality and ecosystem function.

Guinabasan Watershed Soils

The soils of Guinabasan Watershed have bulk density values ranging from 1.29 g/cm3 to 1.59 g/cm3 (Table 1).

Soils in the backslope of the mountainous upland landscape (Pedon 1-Baguio Series) that was previously under traditional shifting cultivation (kaingin) obtained the highest bulk density value (1.59g/cm3) in spite of its clayey texture. Even though the site is recently fallowed, accumulation of organic matter is not enough to rehabilitate the destruction of soil aggregates as the result of the mentioned land use system, hence bulk density is relatively high and can be considered as compact (Jury and Horton, 2004; Arshad et al., 1996).

In contrast with Pedon 1, soils in the shoulder of the mountainous upland landscape of the same soil type (Pedon 2) obtained a bulk density value of 1.48g/cm3. This can be attributed to the surface cover of the site which is dominantly occupied by grasses and broadleaf weed species. The accumulation of organic matter from the decaying roots of the mentioned surface cover enhanced soil aggregation, thus lowering the bulk density of this soil.

Soils of the karst landscape of Guinabasan Watershed that was derived from coralline limestone (Pedon 3-Faraon Series) obtained the lowest bulk density value (1.29 g/cm3), suggesting that this soil is very porous and not compact and can be considered as favorable value or condition since it does not exceed the threshold value of 1.45 g/cm3 according to Arshad et al., 1996. The very high clay content of this relatively young soil which is possibly derived from the limestone parent rock and the very high accumulation of organic matter from the decomposition of the decaying roots of grasses explain the low bulk density. Clayey soils have high amount of pore space and high specific surface area due to its fine texture (Hillel, 1982).The high accumulation of organic matter causes aggregation and structure formation (Tisdale and Oades, 1980) thereby increasing the amount of pore space in the soil volume considered and decreasing the bulk density.

Alluvial soils (Mandaue Series) have bulk density values of 1.57 g/cm3 (Pedon 4) and 1.55g/cm3 (Pedon 5) suggesting that these soils are in compact condition possibly due to frequent deposition of sediments and the influence of cultivation.

Hilabangan Watershed Soils

Results revealed that soils in Hilabangan Watershed exhibit variations in bulk density according to the land use system and surface cover of the site (Table 1).


Table 1. Gravimetric moisture contents and bulk density of Guinabasan and Hilabangan Soils

Site Soil Pit Gravimetric Moisture Contents (g/g) Bulk Density
(g/cc)
Guinabasan Watershed Pedon 1
Pedon 2
Pedon 3
Pedon 4
Pedon 5 0.15
0.15
0.22
0.08
0.16 1.59
1.48
1.29
1.57
1.55
Hilabangan Watershed Pedon 1
Pedon 2
Pedon 3
Pedon 4
Pedon 5 0.05
0.07
0.07
0.11
0.05 1.36
1.29
1.29
1.59
1.44

Soils in the pastureland/grazing area (Pedon 1) obtained a bulk density value of 1.36 g/cm3 despite of the effect of trampling, implying the very important role of soil organic matter in altering the mentioned soil disturbance. Soil organic matter tends to stabilize soil aggregates, hence improving soil aggregation and decreasing bulk density (Tisdale and Oades, 1980).

Dipterocarp forest soils (Pedon 2) obtained a bulk density value of 1.29g/cm3, which can be considered as favorable value (Arshad et al., 1996). The undisturbed nature of the site enhances good aggregation since soil microbes specifically soil fungi that are responsible for structure and aggregate formation have abundant food substrates from the decomposition of leaf litters in the forest floor. These substrates coupled with sufficient soil moisture and soil air serve as their energy source, hence producing high amount of organic matter resulting to the formation of stable aggregates and porous condition thus decreasing bulk density. In addition, since the site is undisturbed organic matter inside stable aggregates is protected from the decomposition hence promoting good aggregation and consequently decreasing bulk density.

Interestingly, soils in the Mangium tree plantation of Hilabangan Watershed (Pedon 3) obtained a similar bulk density value (1.29g/cm3) with Pedon 2.This is probably due to the dominance of clay in the soil as a result of extensive weathering that is possibly a characteristic of an ultisol or oxisol. Clay soils are fine textured and have very high specific surface area resulting to the increase of pore spaces in the soil.

On the other hand, alluvial soils (Pedon 4) which have flat or almost flat topography that are extensively utilized for grazing and previously cultivated for rice obtained a bulk density value of 1.59g/cm3, the highest bulk density value. This is probably due to soil compaction as the result of frequent trampling because of its flat topography that provides favorable grazing area unlike in first site (Pedon1-steep topography). Also the high bulk density value of this soil which indicates a compact condition might be possibly due to frequent disturbance of the previous tillage practices which readily destroy soil structure and soil aggregates.

Soils in the sugarcane plantation (Pedon 5) obtained a bulk density value of 1.44 g/cm3. Such value can be attributed also to the dominance of clay in this soil and frequent disturbance due to the closeness of the pit in the passage way to the plantation.

C. Ecological Implications

Biophysical Assessment

The present characterization\soil survey has clearly shown that the mountainous upland landscapes of Guinabasan and Hilabangan Watersheds that are characterized by andesitic (volcanic) rock formation are very susceptible to soil erosion and other geologic hazards due to the instability of geomorphic surfaces and unsuitable land use systems and poor soil management strategies as observed in the field. The steep slopes of the watershed coupled with erosivity factor enhance very high run-off and erosion. Unsustainable human activities such as deforestation of sloping lands, overgrazing, mining and quarrying activities(for siliceous clay in Hilabangan Watershed), conversion of forest lands to agricultural lands and traditional shifting cultivation (kaingin) in the Hilabangan and Guinabasan Watersheds causes widespread degradation of the two watersheds. The fluvial landforms of Guinabasan and Hilabangan Watersheds that are subjected to seasonal flooding and river swelling are considered as flood prone areas. Lastly, the weak geologic formation of the karst landscapes of Guinabasan make the watershed prone to erosion and degradation. This is due to the carbonate rock type from which karst landscape is formed. It makes the watershed susceptible to erosion because the hard, non-porous karst rocks composed of relatively pure calcium carbonate, such as coralline limestone has greater solubility and therefore dissolved more easily in rains and rivers (SWCF-CFTU-IGCI, 2005) and also when subjected to weathering it produced a very thin solum and shallow karst soil that is susceptible to erosion when the natural vegetation is destroyed.

Soil Profile Description

The accumulation of organic matter in the surface horizons (Ap and Ah), formation of argillic (Bt).spodic (Bs) and cambic (Bw) subsurface diagnostic horizons and the residual and illuvial accumulation of sesquioxides in the profile of the soils of Guinabasan and Hilabangan Watersheds imply that the soils undergo extensive soil processes. Such soil processes have important ecological implications since biodiversity is greatly related to soil processes (Heembersgen et al., 2004).

Organic matter accumulation in the surface horizons enhance the development of a diverse group of soil microorganisms which are responsible for transforming various organic materials (leaves, twigs, branches, decaying to roots) to organic matter or humus through soil enzymatic processes.

The formation of various subsurface diagnostic horizons imply that the soil undergo translocation process specifically leaching because of the abundant rainfall throughout the year. Thus resulting to soil acidification, thereby affecting the diversity of the natural vegetation species and soil fauna. Such acidification enhance the growth of some vegetation species that can thrive acidic soil conditions e.g. Dipterocarps and Mangium that vigorously grow in the Hilabangan Watershed.

The relatively shallow solum depth of soils developed from limestone in Guinabasan Watershed (Soil Profile 3) has important implication to watershed management and protection. The general shallowness of this soil means that erosion is particularly critical as what remains with removal of A horizon is not subsoil but bedrock

In terms of soil coloration, dark or blackish soil color implies high organic matter accumulation while the reddish coloration of soils in the watersheds suggests that the soil is well-aerated and well-drained. That means that the air and water moves freely into and out of the pore spaces of the soil. Such condition enhanced the diversity of the vegetation species and of the soil flora and fauna in the watershed ecosystems.

Weak soil structure grade of the soils of Hilabangan and Guinabasan Watershed has important ecological implications to the function of soils in the watersheds. Weak soil structures slow down water movement into and within the soil thus increasing erosion hazard and landslides.

Bulk Density

The high bulk density values of soils in Guinabasan and Hilabangan Watersheds have very important ecological implications to the functions of soils in watershed ecosystems. High bulk density values indicate a poorer environment for root growth, reduced aeration, compaction and undesirable changes in hydrologic function such as reduced water infiltration. Thus, making the soils vulnerable to erosion and consequently to landslides.

In contrast, the low bulk density values indicate that aggregates have higher stability due to good aggregation hence, such soils are able to resist the disrupting effect of raindrop impact which is the first step in soil erosion. Lastly, organic matter inside stable aggregates is protected from decomposition thus reducing the release of carbon in the atmosphere, hence minimizing the problem of climate change or global warming.


CONCLUSIONS

From the results of the soil survey, the following conclusions may be drawn:

1. The geology of the sites of the Guinabasan Watershed are characterized by volcanic\andesitic and limestone\karst rock formation with alluvial landscapes in the lower elevation while the Hilabangan Watershed are dominated by volcanic/andesitic rock formation specifically andesitic pyroclastic rocks as well as alluvial landscapes. The sloping (steep) or rugged topography of the two watersheds and the high elevation coupled with the abundant rainfall promotes very fast rock weathering and soil formation due to rapid leaching. Unsuitable land use systems and improper soil management strategies, conversion of forests land to agricultural lands, deforestation of sloping lands, mining and natural geologic processes make the two watersheds vulnerable to soil erosion, landslides and flooding.

2. The soils of Guinabasan Watershed and Hilabangan Watershed that are derived from andesitic pyroclastic rocks are strongly weathered, generally red and deep and at the advanced stage of pedogenesis as evidenced of the presence of argillic and spodic subsurface diagnostic horizons (Bt and Bs), residual accumulation of sesquioxides and occurrence of saprolite layers (Cr). While soils of Guinabasan Watershed that are derived from limestones or karst rocks have cambic subsurface diagnostic horizon (Bw),have thin solum and relatively shallow. Alluvial soils of the two watersheds have buried genetic horizons (2Ab) and transition horizons, generally deep and have mottles and gleying in the profile. The soil texture of the two watersheds is generally clayey which turn firm when moist and sticky and plastic when wet. Soil color is generally darker in the surface horizons due to organic matter accumulation thus generally making the soil structure granular, friable consistency when moist and as well as generally causing the abundance and dominance of soil pores and roots in this layer. Soil structure is generally strong and blocky in the subsurface horizons. Degraded sites generally obtained weak grade of soil structure. The karst soils from Guinabasan Watershed have high rock fragments content in the profile.

3. The bulk density values of the soils of Guinabasan Watershed and Hilabangan Watershed ranges from 1.29 g/cm3 to 1.59 g/cm3 and are generally affected by soil organic matter content and aggregation, soil texture ,surface cover and the land use of the site.

4. Slope position, geochemical characteristic of the andesitic pyroclastic, limestone rocks and alluvium and land-use seem to be the major factors that contributed to the characteristics and pedogenesis of soils in the two watersheds.


ACKNOWLEDGMENTS

The author would like to express his sincere thanks and gratitude to the DENR-7 through RTD of ERDS For. Emma E. Melana,RTD of FMS Dr. Isabelo R. Montejo and Chief, TTD Reynaldo L. Lanuza for allowing and contracting the author as an Assisting Professional on Soil Survey and to be part of the watershed characterization project, DENR 7 EMB Laboratory through Maam Ester and Maam Jing and the Regional Soils Laboratory of DA-7 headed by Chief Tita Poyaoan and Maam Helen Acuna for allowing the author to conduct the physical analysis (bulk density) of the sample in their respective laboratories. The author also wish to acknowledge the help provided by the forest rangers of CENRO Toledo and CENRO Ayungon for digging of the soil pits and Kuya Gerry Lanuza for his help in assisting the author in his computer works.

Above all, the Almighty Lord God for all his boundless blessings, guidance and protection that inspired the whole team (for soil component) to continue in spite of the rolling terrain and the “rain or shine” condition in the field.


LITERATURE CITED

ARSHAD, M.A., B. LOWERY, and B.GROSSMAN. 1996.Physical test for monitoring soil
Quality. In: J.W. DORAN and A.J. JONES (eds.) Methods for Assessing Soil
Quality.SSSA Special Publ.No.49,Madison,WI.pp. 123-141

ASIO, V.B. 1998.A review of upland agriculture, population pressure, and environmental
Degradation in the Philippines.Ann.Trop.Res (Phil.)19:1-18.

BARRERA, A., I. J. ARISTORENAS, S.C. HERNANDEZ .Soil Survey of Cebu
Province. Philippine Soil Report No. 17. Bureau of Printing Manila

BARRERA, A., and L.R. JAUG. 1960. Soil Survey of Negros Oriental Province.
Philippine Soil Report No. 17. Bureau of Printing Manila

BLACK, C. A. 1965. Methods of Soil Analysis: Part I. Physical and Mineralogical Properties. American Society of Agronomy, Madison, Wisconsin, USA.

BUOL, S.W., F.D. HOLE, R.J. MCCRAKEN, and R.J. SOUTHARD. 1997. Soil Genesis and Classification, 4th Ed. Iowa State University Press, Ames, IA.

CORONAS,J. 1920. The Climate and Weather of the Philippines. Bureau of Print Manila, Philippines.

DANIELS, R.B. and R. D. HAMMER. 1992. Soil Geomorphology. John Wiley and Sons New York.

FERNANDEZ, N.C. and J.C. de JESUS. 1980. Philippine Soils: Their Distribution, General Land Use and Parent Materials. UPLB, Los Baños Laguna. pp. 229.

GERRARD, J. 1992. Soil Geomorphology: An Integration of Pedology and Geomorphology.
Chapman and Hall. London .

HALL, G. F. 1983. Pedology and Geomorphology. In: Pedogenesis and Soil Taxonomy. Elsevier New York.

HEEMSBERGEN,DA.M.P.BERG,M.LOREAU.J.R. VAN HAL,J.H.FABER and H.A. VERHOEF. 2004. Biodiversity Effects on Soil Processes explained by Interspecific Functional Dissimilarty.Science 306:1019-1020.

HILLEL, D. 1982. Soil Physics. Academic Press, Inc. New York. USA.

JAHN, R. H., H.P. BLUME and V.B. ASIO. 2002. Guide for Soil Description, Site Classification and Site Evaluation. Polish German Soil Societies, Halle/Saale,pp 200

JENNY, H. 1941. Factors of Soil Formation. McGraw Hill Book Company. Inc, New York and London.

JURY, W.A.A and R. HORTON. 2004. Soil Physics. 6th ed. John Wiley and Son, Inc., New Jersey, USA.

LUGO, A. E. and S. BROWN. 1993. ”Management of Tropical Soils as Sinks or Sources of Atmosphere Carbon.” Plant and Soil 149:27-41

MESIAS, J. P. 2007. Soil Survey of Rootcrop Producing Areas in Pilar, Camotes Islands,Cebu. In: Field Methods for Soil Survey and Morphophysical Characteristics of Soils Developed From Quaternary Limestone. Bachelor of Science Thesis Research. Leyte State University, ViSCA, Baybay, Leyte,.Philippines.pp 99

SWCF-CFTU-IGCI.2005.Karst Information Kit For Environmental Management Decision Makers. Soil and Water Conservation Foundation(SWCF),Cebu City, Philippines, Conservation Farming in the Tropical Uplands(CFTU) and International Global Change Institute(IGCI), Hamilton, New Zealand.


O’ RIORDAN, T. 2000. Environmental Science for Environmental Management. Pearson Education Limited. Prentice Hall. United Kingdom. 520 pp.

ROSARIO,E.1987. Soil Sampling Methods In A Watershed.UPLB,Los Baños Laguna.

SCHOENEBERGER, P.J., WYSOCKI, D.A., BENHAM, E.C. and BRODERSON, W.D. 1998. Field Book for describing and sampling soils. Natural Resources Conservation Service, USDA, National Soil Survey Center, Lincoln, N.E.




SOIL SURVEY STAF, 1992. Keys to Soil Taxonomy. A basic system of soil classification
for making and interpreting soil surveys. USDA-NRCS.Gov. Print Office
Washington,D.C.

USDA-NRCS,1996. Soil survey Laboratory Methods Manual. Soil Survey Investigations
Rep. 42 V. 30. USDA-NRCS. Gov. Print. Office Washington D.C.

SPARKS, D.L. 2003. Environmental Soil Chemistry. Academic Press. Elsevier Science. U.S.A.

TISDALE, J.M. and J. M. OADES, 1980. Organic Matter and water-stable aggregates.
J. Soil Sci. 33:141-163.

TOMER, M. and D. JAMES. 2004. Do Soil Surveys and Terrain Analyses Identify Similar Priority Sites For Conservation. Soil Sci. Soc. Am. J.68:1905-1915.

WATSON,R.T.,I.R. NOBLE,B.BOLIN,W.H. RAVINDRANATH,D.J.VERADO and D.J. DOKKEN.2000.Land Use, Land-Use Change and Forestry. Published for the Intergovernmental Panel for Climate Change. Cambridge University Press.







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Appendix I. Biophysical Assessment and Profile Description of Soils in
Guinabasan Watershed

Information on the Characterization Site (Environmental Characteristics)

Profile number: 1
Authors Name: Reynaldo L. Lanuza and Jade P. Mesias
Date:04\23\2008
Climate: Type IV
Weather Condition-Rain\Partly Cloudy
Soil Temperature Regime- Isohyperthermic
Soil Moisture Regime-Udic
Location: Brgy. Baye,Asturias,Cebu
5-90-166 E
11-70-180 N
Soil Series\Type: Baguio Series\Baguio Clay loam
Geomorphic Information:
Geomorphic Description\Component
Landscape- Mountainous Upland
Landform- Volcanic Hill\Steep land
Anthropogenic Feature: Under Fallow(Previously Cropland)
Surface Morphometry:
Elevation- 319 m above sea level
Hill slope-Profile Position-Middle Slope\Back slope
Slope\Topography- Class 4(Moderately steep)
Slope Shape-Linear Concave
Slope Complexity-Complex
Slope Aspect- 10-15 W
Water Status:
Drainage- Well Drained
Soil Water State- Moist
Depth to Water Table- Not Reach
Vegetation\Landcover:Grasses\Herbaceous,Shrubs,Coconut
Parent Material: Andesite
Soil Erosion:
Kind- Sheet
Degree- Class 1(Slightly Eroded)
Surface Fragments: Class 0








SOIL PROFILE DESCRIPTION FOR PEDON 1
(Baguio Series-Middleslope/Backslope)

Ap 0-8 cm Dark brown(7.5YR 3\3) moist;clay;strong fine angular blocky;
friable moist, sticky and plastic wet; many fine roots; many
fine tubular pores; gradual smooth boundary.

Bt 8-24 cm Reddish brown(5YR 5\3)moist;clay;strong fine angular blocky;
firm moist, very sticky and very plastic wet; few very coarse roots;
few very coarse pores; gradual smooth boundary.

Cr1 24-43 cm Dark reddish brown(5YR 3\4)moist; clay; weak fine angular
blocky; firm moist, slightly sticky and very plastic; few fine roots
; very few very fine irregular pores; common rock fragments;
clear smooth boundary.

Cr2 43-58 cm Brown(10YR 4\3)moist; clay; weak fine angular blocky; firm moist
,slightly sticky and moderately plastic; no roots; very few very fine
irregular pores; common rock fragments; clear smooth boundary.

Cr3 58 cm+ Strong brown(7.5YR 4\6)moist; silt loam; weak fine blocky angular;
extremely hard,firm,slighty sticky and slightly plastic; no roots; very
few very fine irregular pores; many rock fragments.

















Information on the Characterization Site (Environmental Characteristics)

Profile number: 2
Authors Name Reynaldo L. Lanuza and Jade P. Mesias
Date:04\24\2008
Climate: Type IV
Weather Condition-Sunny
Soil Temperature Regime- Isohyperthermic
Soil Moisture Regime-Udic
Location: Brgy. Baye,Asturias,Cebu
5-90-913 E
11-70-777 N
Soil Series\Type: Baguio Series\Baguio Clay Loam
Geomorphic Information:
Geomorphic Description\Component
Landscape- Mountainous Upland
Landform- Volcanic Hill\Steep land
Anthropogenic Feature: Previously Cropland
Surface Morphometry:
Elevation- 131 m above sea level
Hill slope-Profile Position-Upper Slope\Shoulder
Slope\Topography- Class 4(Moderately Steep)
Slope Shape-Linear Convex
Slope Complexity-Complex
Water Status:
Drainage- Well Drained
Soil Water State- Moist
Depth to Water Table- Not Reach
Vegetation\Landcover:Grasses\Herbaceous,Brodleaf weeds, Trees,Secondary Forest
Parent Material: Andesite
Soil Erosion:
Kind- Sheet
Degree- Class 1(Slightly Eroded)
Surface Fragments: Class 0











SOIL PROFILE DESCRIPTION FOR PEDON 2 (Guinabasan Watershed)
(Baguio Series-Upperslope\Shoulder)


Ap 0-11 cm Brown (10YR 4\3)moist; sandy loam; strong fine sub-angular blocky;
friable moist, sticky and plastic wet; many very fine roots; many
very fine tubular pores; wavy abrupt boundary.

Bt 11-24 cm Dark reddish brown(2.5YR 3\3)moist;clay;strong fine angular blocky;
friable moist, sticky and plastic wet; few medium roots; few medium
tubular pores; smooth clear boundary.

Cr 24-48 cm Dark red(2.5YR 3\6)moist;loam;strong fine angular blocky; firm
moist, slightly sticky and slightly plastic wet; very few very fine roots;
very few very fine irregular pores; common rock fragments; smooth
clear boundary.

R 48 cm+ Slightly weathered bedrock (andesite)




















Information on the Characterization Site (Environmental Characteristics)

Profile number: 3
Author(s) Name: Reynaldo L. Lanuza and Jade P. Mesias
Date:04\24\2008
Climate: Type IV
Weather Condition-Sunny
Soil Temperature Regime- Isohyperthermic
Soil Moisture Regime-Udic
Location: Brgy. Sta. Rita,Asturias,Cebu
1173101 N
586051 E
Soil Series\Type: Faraon Series\Faraon Clay Steep Phase
Geomorphic Information:
Geomorphic Description\Component
Landscape- Karst land
Landform- Sedimentary Hill
Anthropogenic Feature: Previously Cropland
Surface Morphometry:
Elevation- 150 m above sea level
Hill slope-Profile Position- Crest\Summit
Slope\Topography-Class 4(Moderately Steep)
Slope Shape-Linear Convex
Slope Complexity-Simple
Water Status:
Drainage- Well Drained
Soil Water State- Dry
Depth to Water Table- Not Reach
Vegetation\Landcover:Grassland-Grasses(Cogon),Broadleaf
Parent Material: Limestone
Soil Erosion:
Kind- Sheet
Degree- Class 1(Slightly Eroded)
Surface Fragments: Class 4 (Abundant Stone and Rock Fragments)










SOIL PROFILE DESCRIPTION FOR PEDON 3 (Guinabasan Watershed)
(Faraon Series-Summit)


Ah 0-4 cm Dark brown(10YR 3\3)dry;clay;strong medium granular; friable moist,
sticky and plastic wet; many fine roots; many very fine tubular pores;
common rock fragments; abrupt smooth boundary.

Bw 4-13 cm Dark yellowish brown(10YR 4\4)dry;clay;moderate fine angular blocky
;friable moist, slightly sticky and slightly plastic wet; many fine roots;
many fine tubular pores; many rock fragments; clear gradual boundary

C 13-30 cm Yellowish brown(10YR 5\4)dry;clay;strong fine angular blocky; firm
moist, slightly sticky and slightly plastic wet; few coarse roots; few
coarse tubular pores; abundant rock fragments; clear smooth
boundary

R 30 cm+ Bedrock(Limestone)





















Information on the Characterization Site (Environmental Characteristics)

Profile number: 4
Author(s) Name: Reynaldo L. Lanuza and Jade P. Mesias
Date:04\24\2008
Climate: Type IV
Weather Condition-Partly Cloudy
Soil Temperature Regime- Isohyperthermic
Soil Moisture Regime-Udic
Location: Brgy. Sta. Lucia,Asturias,Cebu
582367 E
1175837 N
Soil Series\Type: Mandaue Series\ Mandaue Silt Loam
Geomorphic Information:
Geomorphic Description\Component
Landscape- Floodplain
Landform- Fluvial
Anthropogenic Feature: Cropland (Cultivated)
Surface Morphometry:
Elevation- 20 m above sea level
Slope-Profile Position- Toeslope
Slope\Topography- Class 1 (Flat or almost flat)
Slope Shape-None
Slope Complexity-None
Water Status:
Drainage- Poorly Drained
Soil Water State- Moist
Depth to Water Table- 47-100 cm+
Vegetation\Land cover:Crop Cover ( Cassava,Corn,Coconut and Banana)
Parent Material: River Alluvium
Soil Erosion\Deposition:
Kind- Sheet
Degree- Class 1(Recent Deposition)
Surface Fragments: Class 0









SOIL PROFILE DESCRIPTION FOR PEDON 4 (Guinabasan Watershed)
(Mandaue Series-Floodplain)

Ap 0-13 cm Very dark gray(10YR 3\1)moist;loam;strong medium sub-angular
blocky; friable moist, slightly sticky and plastic wet; many medium
roots; many medium tubular pores; smooth diffuse boundary

AC 13-33 cm Grayish brown(10YR 5\2)moist; clay loam; strong fine angular blocky;
friable moist, slightly sticky and slightly plastic wet; many coarse roots
;many coarse tubular pores; smooth diffuse boundary.

C 33-51 cm Dark grayish brown(10YR 4\2)moist; reddish brown(2.5YR 5\4)
mottles, many medium prominent mottles; clay loam; strong medium
angular blocky; firm moist, slightly sticky and plastic wet; few fine
roots; few fine tubular pores; smooth abrupt boundary.

2Ab 51 cm+ Reddish brown(5YR 4\4) moist; sandy clay loam; strong coarse sub-
angular blocky; friable moist, sticky and plastic wet; very few very
fine roots; very few very fine tubular pores.




















Information on the Characterization Site (Environmental Characteristics)

Profile number: 5
Authors Name: Reynaldo L. Lanuza and Jade P. Mesias
Date:04\24\2008
Climate: Type IV
Weather Condition-Partly Cloudy
Soil Temperature Regime- Isohyperthermic
Soil Moisture Regime-Udic
Location: Brgy. Old Bago, Asturias,Cebu
585415 E
1174785 N
Soil Series\Type: Mandaue Series\ Mandaue Silt Loam
Geomorphic Information:
Geomorphic Description\Component
Landscape- Floodplain
Landform- Fluvial
Anthropogenic Feature: Cropland
Surface Morphometry:
Elevation- 51 m above sea level
Hill slope-Profile Position- Toeslope
Slope\Topography- Class 1 (Flat or almost flat)
Slope Shape-None
Slope Complexity-None
Slope Aspect- None
Water Status:
Drainage- Poorly Drained
Soil Water State- Moist
Depth to Water Table- Not Reach
Vegetation\Land cover: Crop Cover ( Coconut and Banana) and Grass Cover
Parent Material: River Alluvium
Soil Erosion\Deposition:
Kind- Sheet
Degree- Class 1(Recent Deposition)
Surface Fragments: Class 0








SOIL PROFILE DESCRIPTION FOR PEDON 5 (Guinabasan Watershed)
(Mandaue Series-Floodplain)


Ap 0-11 cm Very dark gray(10YR 3\1)moist;clay;strong fine sub-angular blocky;
friable moist, sticky and plastic wet; many fine roots; many fine
tubular pores; smooth diffuse boundary.

AC 11-31cm Dark gray(10YR 4\1)moist;clay;strong fine angular blocky; firm moist,
slightly sticky and slightly plastic wet; many fine roots; many fine
tubular pores; smooth diffuse boundary.

CA 33-47 cm Dark gray (10YR 4\1)moist; reddish brown(2.5YR 5\4)mottles;
common medium distinct mottles;clay;strong fine angular blocky;firm
moist, slightly sticky and slightly plastic wet; few very fine roots; few
very fine tubular pores; smooth abrupt boundary.

2Ahb 47 cm+ Yellowish brown(10YR 5\6) moist;clay;strong fine angular blocky;
friable moist, sticky and plastic wet; very few fine roots; very few fine
tubular pores.

















Appendix II. Biophysical Assessment and Profile Description of Soils in
Hilabangan Watershed

Information on the Characterization Site (Environmental Characteristics)

Profile number: 1
Author(s) Name: Reynaldo L. Lanuza and Jade P. Mesias
Date:05\22\2008
Climate: Type IV
Weather Condition-Partly Cloudy
Soil Temperature Regime- Isohyperthermic
Soil Moisture Regime-Udic
Location: Brgy.Linao,Tayasan, Negros Oriental
504574 1094709
Soil Series\Type: Unclassified Mountain Soils(Barrera and Jaug,1960)
Geomorphic Information:
Geomorphic Description\Component
Landscape- Mountainous Upland
Landform- Volcanic\Andesitic Hill
Anthropogenic Feature: Grazing
Surface Morphometry:
Elevation-503 meters above sea level
Hill Slope-Profile Position- Lower Backslope
Slope\Topography-Class 5(Steep)
Slope Gradient-30°-50°
Slope Shape-Linear Convex
Slope Complexity-Simple
Water Status:
Drainage- Well Drained
Soil Water State- Moist
Depth to Water Table- None
Vegetation\Landcover: Grasses (Cogon) Imperata cylindrica
Broadleaf (Hagonoy) Chromolaena odorata and few Mangium
Parent Material: Residual material derived from andesite
Soil Erosion:
Kind- Sheet
Degree- Severely Eroded
Surface Fragments: Class 3 (Sufficient Bedrock Exposures)








SOIL PROFILE DESCRIPTION FOR PEDON 1
(Grassland\Pastureland-Lower Backslope)


Ap 0-6 cm Black (10YR 2\1)moist; clay loam; weak fine granular; friable
moist sticky and plastic wet; many fine roots; many fine tubular
pores; common rock fragments; clear broken boundary.

Cr 6-60 cm Very dark gray(10YR 3\1)moist; clay; weak fine angular blocky;
firm moist, sticky and plastic wet; very few very fine roots; very
few very fine irregular pores; abundant rock fragments; clear
broken boundary.

R 60 cm+ Slightly weathered andesite





Information on the Characterization Site (Environmental Characteristics)

Profile number: 2
Author(s) Name: Reynaldo L. Lanuza and Jade P. Mesias
Date:05\22\2008
Climate: Type IV
Weather Condition-Partly Cloudy
Soil Temperature Regime- Isohyperthermic
Soil Moisture Regime-Udic
Location: Brgy. Banban,Ayungon, Negros Oriental
9°50’31.14” 123°2’31.23”
Soil Series\Type: Unclassified Mountain Soils(Barrera and Jaug,1960)
Geomorphic Information:
Geomorphic Description\Component
Landscape- Mountainous Upland
Landform- Volcanic\Andesitic Hill
Anthropogenic Feature: None(Undisturbed Dipterocarp Forest)
Surface Morphometry:
Elevation-652 meters above sea level
Hill Slope-Profile Position- Upper Backslope
Slope\Topography-Class 4(Moderately Steep)
Slope Gradient-30°-40°
Slope Shape-Linear Convex
Slope Complexity-Complex
Water Status:
Drainage- Well Drained
Soil Water State- Moist
Depth to Water Table- None
Vegetation\Landcover: Dipterocarp Forest
Parent Material: Residual material derived from andesite
Soil Erosion:
Kind- Sheet
Degree- Very Slight
Surface Fragments: None












SOIL PROFILE DESCRIPTION FOR PEDON 2
(Dipterocarps-Upper Backslope)


Oe 0-3 cm Dark yellowish brown(10YR 3\4)moist; clay loam; strong medium
granular friable moist, slightly sticky and slightly plastic wet; no roots;
many fine tubular pores; clear smooth boundary.

Ah 3-15 cm Dark yellowish brown(10YR 4\6)moist; clay; strong medium granular;
friable moist, sticky and plastic wet; few fine roots; many fine vesicular
pores; gradual smooth boundary

Bs1 15-33 cm Yellowish brown(10YR 5\6)moist;clay;moderate medium angular
blocky; firm moist, very sticky and very plastic wet; very few coarse
roots; very few fine tubular pores; gradual smooth boundary.

Bs2 33-62 cm Yellowish brown(10YR 5\6)moist;clay;moderate medium angular
blocky; firm moist, very sticky and very plastic wet; very few medium
roots; very few medium tubular pores; wavy abrupt boundary.

Cr 62 cm+ Brownish yellow(10YR 6\8)moist; sandy clay; massive structure;
extremely firm moist, slightly sticky and slightly plastic wet; no roots;
no pores.























Information on the Characterization Site (Environmental Characteristics)

Profile number: 3
Author(s) Name: Reynaldo L. Lanuza and Jade P. Mesias
Date:05\22\2008
Climate: Type IV
Weather Condition-Partly Cloudy
Soil Temperature Regime- Isohyperthermic
Soil Moisture Regime-Udic
Location: Sitio Ilaya,Brgy.Tambo,Ayungon, Negros Oriental
506891 1092731
Soil Series\Type: Unclassified Mountain Soils(Barrera and Jaug,1960)
Geomorphic Information:
Geomorphic Description\Component
Landscape- Mountainous Upland
Landform- Volcanic\Andesitic Hill
Anthropogenic Feature: Plantation
Surface Morphometry:
Elevation-507 meters above sea level
Hill Slope-Profile Position- Shoulder
Slope\Topography-Class 4( Moderately Steep)
Slope Gradient-15°-20°
Slope Shape-Linear Convex
Slope Complexity-Complex
Water Status:
Drainage- Well Drained
Soil Water State- Moist
Depth to Water Table- None
Vegetation\Landcover: Mangium Tree Plantation
Parent Material: Residual material derived from volcanic rock (andesite)
Soil Erosion:
Kind- Sheet
Degree- Slightly Eroded
Surface Fragments: None












SOIL PROFILE DESCRIPTION FOR PEDON 3
(Mangium Tree Plantation-Shoulder)


Ap 0-15 cm Very dark grayish brown(10YR 3\2)moist; clay; moderate medium
angular blocky; friable moist, sticky and plastic wet; few very fine roots;
few very fine tubular pores; clear smooth boundary.

AB 15-23 cm Dark yellowish brown(10YR 4\4)moist;clay;moderate coarse angular
blocky; friable moist ,very sticky and very plastic wet; few fine roots;
few fine vesicular pores ;abrupt smooth boundary.

Bto 23-35 cm Dark yellowish brown(10YR 4\6)moist; clay; weak coarse sub-angular
blocky; firm moist, very sticky and very plastic wet; patchy thin clay
skins and sesquioxides,probably of clay minerals with iron oxides and
hydroxides on ped faces; few moderate roots; few moderate dendritic
tubular pores; gradual smooth boundary.

BCto 35-62 cm Strong brown(7.5YR 4\6)moist; clay; strong course angular blocky;firm
moist, sticky and plastic wet; patchy thin clay skins and sesquioxides
,probably of clay minerals with iron oxides and hydroxides on ped
faces; few fine roots; many fine vesicular pores; diffuse smooth wavy
boundary.

Croc 62 cm+ Yellowish red(5YR 4\6)moist; clay; strong very coarse sub-angular
blocky; extremely firm moist; very sticky and very plastic wet; with
sesquioxides and black ironstone nodules on ped faces; very few
fine roots; few fine tubular pores.


















Information on the Characterization Site (Environmental Characteristics)

Profile number: 4
Author(s) Name: Reynaldo L. Lanuza and Jade P. Mesias
Date:05\28\2008
Climate: Type IV
Weather Condition-Partly Cloudy
Soil Temperature Regime- Isohyperthermic
Soil Moisture Regime-Udic
Location: Approximately 100 meters (S40°W) from the steel bridge of
Brgy. Bago,Tayasan, Negros Oriental
9°55’10.59” 123°0’50.18”
Soil Series\Type: Unclassified Mountain Soils(Barrera and Jaug,1960)
Geomorphic Information:
Geomorphic Description\Component
Landscape- Andesitic Terrace
Landform- Fluvial
Anthropogenic Feature: Grazing and cultivation (Rice paddies)
Surface Morphometry:
Elevation-258 meters above sea level
Hill Slope-Profile Position- Terrace (Tread)
Slope\Topography-Class 1 (Flat or almost flat)
Slope Gradient-3°-5°
Slope Shape-NA
Slope Complexity-NA
Water Status:
Drainage- Poorly Drained
Soil Water State- Moist
Depth to Water Table-Below profile
Vegetation\Landcover: Grasses(Pasture) and Rice crop
Parent Material: Andesitic Terrace(old alluvial) deposit-Alluvium
Soil Erosion\Deposition:
Kind- Sheet\ Old alluvial deposits
Degree-Eroded by swelling Hilabangan River
Surface Fragments: None











SOIL PROFILE DESCRIPTION FOR PEDON 4
(Rice Paddy\Pastureland-Terrace)


Ap 0-12 cm Black (10YR 2\1)moist; dark red (2.5YR 3\6) mottles, few fine distinct
mottles;clay;weak medium angular blocky; friable moist, sticky and
plastic wet ;many very fine roots; many very fine dendritic tubular
pores; clear smooth boundary

Bw 12-28 cm Very dark grayish brown(10YR 3\2)moist; dark red(2.5YR 3\6) mottles
,common fine distinct mottles;clay;moderate medium angular blocky;
firm moist, sticky and plastic wet; few very fine roots; many very fine
tubular pores; gradual smooth boundary.

Cg 28-49 cm Greenish black(10Y 2.5\1)moist; dark red (2.5YR 3\6) mottles, common
medium distinct mottles;clay;moderate medium angular blocky; firm
moist, sticky and plastic wet; few very fine roots; few very fine tubular
;diffuse smooth boundary.

2Bgb 49-66 cm Greenish black(10Y 2.5\1)moist; dark red (2.5YR 3\6) mottles, very
few coarse distinct mottles;clay;strong medium angular blocky
extremely firm moist, very sticky and very plastic wet; few very fine
roots; few very fine tubular pores; abrupt wavy boundary

2Crgb 66 cm+ Brown(10YR 4\3)moist; dark red(2.5YR 3\6) mottles, few coarse
distinct mottles; sandy clay; massive(structureless); extremely firm
moist, slightly sticky and slightly plastic wet; no roots; no pores.



















Information on the Characterization Site (Environmental Characteristics)

Profile number: 5
Author(s) Name: Reynaldo L. Lanuza and Jade P. Mesias
Date:05\22\2008
Climate: Type IV
Weather Condition-Rainy
Soil Temperature Regime- Isohyperthermic
Soil Moisture Regime-Udic
Location: Brgy.Hilabangan,Tayasan, Negros Oriental
9°56’46.28” 123°4’26.81”
Soil Series\Type: Unclassified Mountain Soils(Barrera and Jaug,1960)
Geomorphic Information:
Geomorphic Description\Component
Landscape- Mountainous Upland
Landform- Volcanic\Andesitic Hill
Anthropogenic Feature: Cultivated
Surface Morphometry:
Elevation-491 meters above sea level
Hill Slope-Profile Position- Summit
Slope\Topography-Sloping
Slope Gradient-10°-15°
Slope Shape-Linear Convex
Slope Complexity-Complex
Water Status:
Drainage- Well Drained
Soil Water State- Moist and Wet
Depth to Water Table- None
Vegetation\Landcover: Sugarcane and few grasses
Parent Material: Residual material derived from extrusive volcanic rock (andesite)
Soil Erosion:
Kind- Sheet
Degree- Severely Eroded (Rock exposure)
Surface Fragments: Class 1 (Sufficient rock exposures)









SOIL PROFILE DESCRIPTION FOR PEDON 5
(Sugarcane Plantation-Summit)


Ap 0-18 cm Very dark grayish brown(10YR 3\2)moist; clay; weak fine angular
blocky; friable moist, sticky and plastic wet; with sesquioxides;many
fine roots; many fine tubular pores; clear smooth boundary.

Bhs 18-24 cm Dark yellowish brown(10YR 3\4)moist;clay;weak medium angular
blocky; firm moist, very sticky and very plastic wet; with sesquioxides;
few fine roots; few fine tubular pores; gradual smooth boundary

Bto 23-35 cm Red (2.5YR 4\6)moist; clay; strong medium angular blocky;firm
moist, very sticky and very plastic wet; patchy thin clay skins and
sesquioxides,probably of clay minerals with iron oxides and
hydroxides on ped faces; very few fine roots; very few fine tubular
;diffuse wavy boundary.

Cro 62cm + Red (2.5YR 4\6)moist; clay; moderate medium angular blocky
;firm moist, sticky and plastic wet; with sesquioxides;very few
very fine roots; very few very fine tubular pores.


























Appendix III. Raw Data for Bulk Density of Guinabasan Watershed Soils





Bulk Density(Paraffin Clod Method) of the Soils of Guinabasan Watershed in Asturias,Cebu
CLOD VOLUME DETERMINATION
Sample FWc FWpcc(a) FWpcc(w) Vpcc Wp Vp Vc
P1R1 39.28 47.84 30.54 30.54 8.56 9.511111 21.02889
P1R2 49.30 58.11 37.09 37.09 8.81 9.788889 27.30111
P1R3 24.29 28.53 17.95 17.95 4.24 4.711111 13.23889
P2R1 20.58 25.45 17.40 17.4 4.87 5.411111 11.98889
P2R2 20.64 27.12 19.58 19.58 6.48 7.2 12.38
P2R3 23.78 28.43 18.90 18.9 4.65 5.166667 13.73333
P3R1 15.18 18.69 13.43 13.43 3.51 3.9 9.53
P3R2 23.98 29.32 21.10 21.1 5.34 5.933333 15.16667
P3R3 17.48 21.99 16.14 16.14 4.51 5.011111 11.12889
P4R1 28.00 34.43 24.45 24.45 6.43 7.144444 17.30556
P4R2 38.27 43.87 28.72 28.72 5.6 6.222222 22.49778
P4R3 30.36 35.43 22.30 22.3 5.07 5.633333 16.66667
P5R1 49.77 57.03 37.59 37.59 7.26 8.066667 29.52333
P5R2 63.67 73.72 46.28 46.28 10.05 11.16667 35.11333
P5R3 38.30 43.10 25.41 25.41 4.8 5.333333 20.07667












































Bulk Density(Paraffin Clod Method) of the Soils of Guinabasan Watershed in Asturias,Cebu
SOIL SOLID MASS DETERMINATION
Sample Wtc FW(tc+s) ODW(tc+s) FWs(g) Ww ODW(s) GMC FW(bd) ODW(s-b) Vc Bulk Density
P1R1 2.66 41.94 36.66 39.28 5.28 34.00 0.155294 39.28 34.00 21.02889 1.62
P1R2 2.64 51.94 46.28 49.3 5.66 43.64 0.129698 49.30 43.64 27.30111 1.60
P1R3 2.64 26.93 23.4 24.29 3.53 20.76 0.170039 24.29 20.76 13.23889 1.57
AVERAGE 1.59
P2R1 2.6 23.18 20.24 20.58 2.94 17.64 0.166667 20.58 17.64 11.98889 1.47
P2R2 2.64 23.28 20.71 20.64 2.57 18.07 0.142225 20.64 18.07 12.38 1.46
P2R3 2.6 26.38 23.24 23.78 3.14 20.64 0.152132 23.78 20.64 13.73333 1.50
AVERAGE 1.48
P3R1 2.65 17.83 15.03 15.18 2.8 12.38 0.226171 15.18 12.38 9.53 1.30
P3R2 2.66 26.64 22.13 23.98 4.51 19.47 0.231638 23.98 19.47 15.16667 1.28
P3R3 2.64 20.12 17.13 17.48 2.99 14.49 0.206349 17.48 14.49 11.12889 1.30
AVERAGE 1.29
P4R1 2.62 30.62 28.25 28 2.37 25.63 0.09247 28.00 25.63 17.30556 1.48
P4R2 2.62 40.89 37.58 38.27 3.31 34.96 0.09468 38.27 34.96 22.49778 1.55
P4R3 2.64 33 30.59 30.36 2.41 27.95 0.086225 30.36 27.95 16.66667 1.68
AVERAGE 1.57
P5R1 2.64 52.41 45.36 49.77 7.05 42.72 0.165028 49.77 42.72 29.52333 1.45
P5R2 2.64 66.31 57.42 63.67 8.89 54.78 0.162286 63.67 54.78 35.11333 1.56
P5R3 2.63 40.93 35.55 38.3 5.38 32.92 0.163426 38.30 32.92 20.07667 1.64
AVERAGE 1.55









CLOD VOLUME DETERMINATION
Sample FWc FWpcc(a) FWpcc(w) Vpcc Wp Vp Vc
P1R1 13.70 18.63 15.29 15.29 4.93 5.477778 9.812222
P1R2 28.70 36.56 27.67 27.67 7.86 8.733333 18.93667
P1R3 22.93 29.37 24.31 24.31 6.44 7.155556 17.15444
P1R4 20.70 27.18 21.43 21.43 6.48 7.2 14.23
P1R5 17.22 22.84 18.31 18.31 5.62 6.244444 12.06556
P2R1 28.95 34.92 28.58 28.58 5.97 6.633333 21.94667
P2R2 11.29 16.17 13.77 13.77 4.88 5.422222 8.347778
P2R3 23.85 32.71 26.88 26.88 8.86 9.844444 17.03556
P2R4 14.75 19.28 15.44 15.44 4.53 5.033333 10.40667
P2R5 16.35 24.22 20.42 20.42 7.87 8.744444 11.67556
P3R1 24.76 37.47 32.01 32.01 12.71 14.12222 17.88778
P3R2 39.96 51.41 39.67 39.67 11.45 12.72222 26.94778
P3R3 22.56 30.76 25.79 25.79 8.2 9.111111 16.67889
P3R4 24.36 35.41 30.75 30.75 11.05 12.27778 18.47222
P3R5 28.79 41.41 34.90 34.9 12.62 14.02222 20.87778
P4R1 17.34 24.37 17.57 17.57 7.03 7.811111 9.758889
P4R2 37.30 45.75 29.36 29.36 8.45 9.388889 19.97111
P4R3 31.98 44.89 32.84 32.84 12.91 14.34444 18.49556
P4R4 46.05 57.05 37.82 37.82 11 12.22222 25.59778
P4R5 19.70 25.23 18.17 18.17 5.53 6.144444 12.02556
P5R1 25.97 34.96 26.34 26.34 8.99 9.988889 16.35111
P5R2 20.55 27.00 21.53 21.53 6.45 7.166667 14.36333
P5R3 31.56 37.94 28.19 28.19 6.38 7.088889 21.10111
P5R4 40.23 50.59 36.97 36.97 10.36 11.51111 25.45889
P5R5 20.62 26.63 20.46 20.46 6.01 6.677778 13.78222
Appendix IV. Raw Data for Bulk Density of Hilabangan Watershed Soils

Bulk Density(Paraffin Clod Method) of the Soils of Hilabangan Watershed in Ayungon and Tayasan, Negros Oriental

































Bulk Density(Paraffin Clod Method) of the Soils of Hilabangan Watershed
SOIL SOLID MASS DETERMINATION
Sample Wtc FW(tc+s) ODW(tc+s) FWs(g) Ww ODW(s) GMC FW(bd) ODW(s-b) Vc Bulk Density
P1R1 16.57 35.72 34.85 19.15 0.87 18.28 0.047593 13.70 13.08 9.812222 1.33
P1R2 17.11 36.81 35.92 19.7 0.89 18.81 0.047315 28.70 27.40 18.93667 1.45
P1R3 15.21 37.22 36.26 22.01 0.96 21.05 0.045606 22.93 21.93 17.15444 1.28
P1R4 15.05 44.25 42.91 29.2 1.34 27.86 0.048098 20.70 19.75 14.23 1.39
P1R5 15.37 41.72 40.5 26.35 1.22 25.13 0.048548 17.22 16.42 12.06556 1.36
AVERAGE 1.36
P2R1 15.21 41.19 39.43 25.98 1.76 24.22 0.072667 28.95 26.99 21.94667 1.23
P2R2 15.19 26.7 25.94 11.51 0.76 10.75 0.070698 11.29 10.54 8.347778 1.26
P2R3 15.41 38.57 36.94 23.16 1.63 21.53 0.075708 23.85 22.17 17.03556 1.30
P2R4 18.25 33.48 32.46 15.23 1.02 14.21 0.07178 14.75 13.76 10.40667 1.32
P2R5 13.95 29.79 28.83 15.84 0.96 14.88 0.064516 23.85 22.40 17.03556 1.32
AVERAGE 1.29
P3R1 15.27 50.67 48.21 35.4 2.46 32.94 0.074681 24.76 23.04 17.88778 1.29
P3R2 17.08 57.74 54.87 40.66 2.87 37.79 0.075946 39.96 37.14 26.94778 1.38
P3R3 16.22 47.74 45.61 31.52 2.13 29.39 0.072474 22.56 21.04 16.67889 1.26
P3R4 14.68 42.6 40.58 27.92 2.02 25.90 0.077992 24.36 22.60 18.47222 1.22
P3R5 16.28 45.29 43.36 29.01 1.93 27.08 0.07127 28.79 26.87 20.87778 1.29
AVERAGE 1.29
P4R1 14.11 37 34.55 22.89 2.45 20.44 0.119863 17.34 15.48 9.758889 1.59
P4R2 17.1 56.1 51.89 39 4.21 34.79 0.121012 37.30 33.27 19.97111 1.67
P4R3 15.29 36.68 34.41 21.39 2.27 19.12 0.118724 31.98 28.59 18.49556 1.55
P4R4 17.08 38.89 36.72 21.81 2.17 19.64 0.110489 46.05 41.47 25.59778 1.62
P4R5 18.27 33.76 32.17 15.49 1.59 13.90 0.114388 31.98 28.70 18.49556 1.55
AVERAGE 1.59
P5R1 15.93 58.38 56.31 42.45 2.07 40.38 0.051263 25.97 24.70 16.35111 1.51
P5R2 15.64 41.24 40.02 25.6 1.22 24.38 0.050041 20.55 19.57 14.36333 1.36
P5R3 17.05 62.95 60.61 45.9 2.34 43.56 0.053719 31.56 29.95 21.10111 1.42
P5R4 15.15 44.72 43.31 29.57 1.41 28.16 0.050071 40.23 38.31 25.45889 1.50
P5R5 17.06 50.86 49.22 33.8 1.64 32.16 0.050995 20.62 19.62 13.78222 1.42
AVERAGE 1.44