Volume 24 Nos. 1 & 2

Biomass and carbon sequestration of Jatropha curcas L. plantation


One of the most pressing problems nowadays is global warming brought about by the increasing levels of greenhouse gases, particularly carbon dioxide (CO2), in the atmosphere. Plants take up CO2 from the atmosphere and store the carbon in their biomass (roots, stems and foliage) through the process of photosynthesis.

This study was conducted to provide basic information for accurate and reliable estimations of the biomass and amount of carbon being sequestered by Jatropha curcas L. plants.

Aboveground and belowground biomass were determined for 127 J. curcas plants with ages 5-42 months from the provinces of Nueva Ecija, Laguna, Quezon, Camarines Sur, and North and South Cotobato. The total green biomass of a J. curcas plant ranged from 0.06 to 42.2 kg. The average plant contained 11% of the total dry weight in the leaves, 51% in the stem (branches and twigs) and 38% in the roots. On the average, 62% of the plant dry weight was the biomass aboveground and 30% was the biomass belowground.

Regardless of age and size, approximately 76% of the green biomass of the plants was water, or equivalently, 24% dry matter.

Prediction equations using allometric models were developed for estimating the fresh and ovendry weights of the whole plant and its components using easily measured variables such as basal diameter and total height.

Based on the carbon analyses done on the plant samples, the oven-dried leaves, stems (branches/twigs) and roots have 43.2%, 44.5%, and 42.7% total carbon, respectively. On the average, a J. curcas plant has 43.5% stored carbon in its dry mass.



Vulnerability assessment of the Naguilian River Watershed to landslide and forest/grass fire


The Naguilian River Watershed is one of the important sources of water in the Cordillera Administrative Region that covers an approximate area of 18,524.09 hectares. It includes portion of Baguio City, the municipalities of Kapangan, Tublay, La Trinidad and Sablan in the Province of Benguet. This is where the study on vulnerability assessment to landslide and fire was conducted.

Vegetation analyses were conducted within the different landuses/ecosystems of the Naguilian Watershed adopting different methods of analyses. The dominat species in the different ecosystems/landuses within the watershed were determined. Benguet pine (Pinus kesiya) and Tuai (Bishchofia javanica) were the dominant species in natural forests and riparian area, respectively. In open/grassland area, Mischantus sinensis, Pennisetum polystachion, Tithonia diversifolia, Chromolaena odorata and Musa sp. were the dominant species. Using ethnobotanical survey/interview and secondary data collection, 17 different bird species were listed. Three mammals, three reptiles, six fishes and aquatic species were also identified.

The socio-cultural characterization in the area revealed a high level of awareness of the people on the presence of forestry agency and issues/concerns on watershed. Solid waste was not given much attention by the residents although IEC on this matter had been conducted by Local Government Unit (LGU)local officials and the Department of Environment and Natural Resources (DENR). They are very willing to work for to work for the preservation and management of their environment and natural resources. Majority of them agreed that there is a need to conserve their forest. Result of the Focus Group Discussion (FGD) showed that the watershed is vulnerable to landslide could be attributed to the steep slope of the area/watershed and other livelihood options which utilize resources in the area like charcoal production, kaingin making, and to some extent the small scale mining. To solve the problem, the community leaders proposed for strict implementation of forestry rules and encourage the people to plant more trees.

The watershed attributes based on characterization activities were analyzed especially those contributing to landslides and fire occurence. Results were used as inputs to the GIS-based spatial analyses. Slope was considered to be the most important factor. Rainfall, landuse/land cover, faultline, geology and soil attributes were the other important factors.

The simple overlaying technique in GIS was employed to evaluate the vulnerability of the watershed to landslide. The thematic maps were prepared and rated/scored by the multidisciplinary team. The higher the contribution of the parameter to landslide, the higher is the rating. The results showed that the watershed has high vulnerability to landslide.

Result of the study also showed that the watershed is moderately vulnerable to forest/grassfire. Simple rating of both the biophysical and socio-cultural-institutional factors was employed. The occurence of fire is generally considered to be governed by anthropogenic factors.



Geospatial modeling of soil erosion in Buhisan Watershed Forest Reserve, Cebu City, Philippines: Model application and validation


Buhisan Watershed Forest Reserve (BWFR) is an important watershed in Metro Cebu because it is one of the major sources of potable water. However, it is faced by soil degradation due to natural and human-related activities. Thus, this research aimed to assess the soil erosion vulnerability; determine and map-out the vulnerability levels; design specific mitigating measures; and propose policy recommendations.

The GIS-assisted model on soil erosion integrating USLE was applied in Buhisan Watershed. It was predicted that about 60.20% or about 369.22 hectares have very high potential for soil erosion under existing condition. On the average, the predicted soil erosion is about 160.23 tons/ha/yr. Among the barangays, Buhisan has the largest area with very high potential soil erosion.

Mitigating measures were formulated to address the excessive soil erosion in the watershed. This comprises the enhancement of vegetative cover through saturation planting of indigenous and deep-rooted species, construction of gabions and check dams in waterways, and planting of bamboo in riparian zones. It was predicted that ther was a significant decrease in soil erosion. The predicted average potential soil loss is about 8.92 tons/ha/yr. The proposed mitigating measures resulted in a decrease of 356.53 hectares from the original soil loss of 421.23 hectares under existing condition categorized as high to very high soil erosion.

The model was validated using the actual soil erosion data gathered from 28 established monitoring stations. No significant differences were noted between the observed and predicted soil loss which implies that the model could estimate the potential soil loss. Moreover, a highly significant positive correlation was noted. Furthermore, regression analysis was also highly significant. Therefore, the GIS-assisted model can be used as an alternative tool in soil erosion prediction.



Research Note: Water pricing for domestic purpose at Caniaw Watershed in Bantay, Ilocos Sur: A Contingent Study


The study was conducted to determine the value of the improved water supply that could improve the management of Caniaw Watershed. Specifically, it aimed to 1) evaluate the level of awareness of residents about the importance of watersheds in ensuring sustainable water supply; 2) determine the residents' willingness to pay for for the improved management of watershed; 3) identify the factors that affect the resident's willingness to pay; 4) identify the reasons why water users may not be willing to pay for the improved management of watersheds; 5) provide costyestimates of providing water through improved watershed management and through conventional means; and lastly, 6) develop a mechanism by which the fund for improved watershed management will be collected and utilized.

The results of the study suggested the low awareness of the respondents about the watershed however, many of them knew that the forest serves as a source of water. Residents within the Metro Vigan area are willing to pay as much as P24.43 per month for improved management of Caniaw which is about 6% of the average monthly water bill of P402.74.

The Mean Williness to Pay (MWTP) was affected by factors such as bid amount, water supply problem, familiarity/awareness with Caniaw watershed, average water consumption, water pump as other source of water supply, annual income, household size, age, civil status, income group, level of education and respondents' knowledge about other user groups being made to pay for watershed services. The residents are willing to pay mainly because they want a sustainable water supply for both present and future generations. The respondents preferred a water users' fee to be added to their monthly water bill.

Some respondents expressed unwillingness to pay because they cannot afford the additional amount on their bill and believed that the government should be the one financing watershed management.

The potential revenue based on the willingness to pay of P24.43 of the water users would be P164,072 monthly or P1,968,864 annually. This amount could be used to rehabilitate and protect the open and degraded areas of Caniaw including the employment of additional Forest Guards and provision of alternative livelihood of the charcoal makers.