Sylvatrop Volume 11 Nos. 1 & 2 – January to December 2001
SYLVATROP Volume 11 Nos. 1 & 2 – January to December 2001 Contents:
Forest resources monitoring using spaceborne Synthetic Aperture RADAR (SAR) in Aurora Province, Philippines
by Jose C. Cabanayan Jr., Peter H. Crown, and Benoit Rivard
Forest monitoring using optical instruments such as aerial photographs and LANDSAT/SPOT data is difficult to implement in the Philippines due to the presence of clouds and haze that are prevalent in the tropics. Aurora province was chosen as the typical area of this nature with the presence of illegal harvesting of trees under the canopy and some clearings of small patches of forest. The use of spaceborne Synthetic Aperture RADAR (SAR) like Japanese Earth Resources-1 or JERS-1 that is independent of these natural occurrences in forested areas could provide immediate information on the forest disturbances. Six different forest types and two agricultural land use classes were subjected to this study occurring in 48 combinations of aspect and slope magnitudes. Backscattered energies were measured on each combination and compared to determine the relationship and difference in discriminating the old-growth forest from the residual forest, yet small clearings like slash-and-burn agriculture were easily detected. The use of the RADAR data alone for forest monitoring is difficult to implement, thus, care should be taken into consideration on these terrain features.
Jackknifing in estimating species diversity of a logged-over dipterocarp forest in Surigao del Sur
by Marilyn N. Piñol
The impact of the jackknifing procedure as a tool to correct the bias of the usual estimation procedure for species diversity was studied through simulation. A test population using available data on relative abundance of the different species observed in four forest stands, under the seed tree method in the logged-over dipterocarp forest was used to draw samples through simulation for the comparison of the relative reduction in bias of the jackknifed estimates from sample-based estimates of the three diversity indices, namely, species richness, Shannon’s index, and Simpson’s index.
Jackknifing resulted in the substantial reduction in the bias, which may exceed 50% for n > 20, with the relative bias < 0.10. On the other hand, jackknifing has led to an increase in the variance of the estimates. This, however, did not diminish the advantage of the jackknifing procedure over the usual sample-based procedure, since the mean square error of the sample-based estimates were considerably reduced when jackknifed.
Analysis of two-year data on Laguna de Bay water quality at the offshores of Pililla, Rizal
by Leo L. Pagdingalan, Angelita C. Rivera, and Jocelyn G. Sta. Ana
Data from monthly monitoring of the Laguna de Bay at the offshore of Pililla, Rizal were analyzed to evaluate water quality and determine the extent of pollution in the area. Results showed that majority of the parameters complied with the Class C water quality criteria. With only oil and grease, total suspended solids, and inorganic phosphate exceeding the criteria, water quality in the region is still suitable for fishery development.
Global Positioning System station velocity variations in the Philippines attributed to seismic charging and intra-measurement deformation near active tectonic structures
by Mario A. Aurelio and Christophe Vigny
In recognition of the complex tectonic setting of the Philippines, a Global Positioning System (GPS) network was established in 1994. The exercise was aimed primarily to provide quantitative data on how active tectonic blocks of the archipelago move relative to each other. This paper presents GPS data sets from three campaigns in the GEODYSSEA, analyzed in terms of the present-day tectonic setting of the Philippines.
Velocity vectors in stations close to major structures such as those in Surigao (station SURI), Iloilo (ILOI), Virac (VIRA), or Zamboanga (ZAMB) showed significant variations within separate time intervals. The strong easterly component observed in SURI may be due to intra-measurement extensional tectonics along the Lake Mainit segment of the Philippine Fault while the westerly deviation in ILOI appears to be due to extensional seismic strain affecting the Eastern Visayas. On the other hand, compressional intra-measurement tectonics and subduction-related seismic strain appear to affect ZAMB and VIRA, respectively.
Empowerment of Kanan River stakeholders towards sustainable watershed management
by Marcial C. Amaro Jr.
The study attempted to provide an alternative institutional mechanism which calls for the active participation of stakeholders in the planning and management of watersheds according to their needs and aspirations. This alternative required the harmonization of the stakeholders’ roles, resources, capabilities and interventions, and their empowerment towards sustainable watershed management through the operationalization of a multisectoral watershed management council (MSWMC). The results shall be used as basis in policy formulation and issuance.
The 35,500-ha Kanan River Watershed located in the Municipality of General Nakar, Quezon Province was chosen as the study site.
Focus group discussions (FGDs) constituted the basic research methodology adopted for the study. Four FGDs were held after the stakeholder analysis to seek data on (a) concept/importance of watershed, (b) perceptions and problems on the role of own organizations as stakeholders, (c) perceptions on the roles of other organizations/stakeholders, and (d) the relevance of MSWMC. The results were validated in an integrating workshop where the stakeholders agreed to create a MSWMC.
The study substantially answered the problem on harmonizing the stakeholders and empowering them. However, it failed to come up with the draft guidelines on the operationalization of MSWMCs nationwide. The experience was still inadequate to form the basis for a new administrative issuance. A much longer period is needed to prove if the interventions introduced are effective and replicable. The study also failed to generate an authoritative assessment of the changes in the role of the DENR in the light of the empowerment of other stakeholders.
Multivariate predictive empirical modelling on forest fire occurrence and development of forest fire hazard rating system for Central Luzon using a posteriori probability approach
by Vicente B. Tuddao Jr.
An in-depth study on the occurrence of forest fire in Central Luzon, Philippines was conducted to evaluate the significant influencing biophysical environmental factors that cause fire initiation and spread. Specifically, this study aimed to establish the best fitted predictive empirical model to estimate forest fire occurrence and spread. It was found out that the best relationship is a multivariate linear model which is a function of wind speed (in meter per second) and the availablity of dry fuel load (in centimeter depth). This model clearly indicated that the variables could already explain 54.7% of the variability in forest fire occurrence and spread. The established model was tested to be adequate and with statistically significant goodness of fit based on its high correlation coefficient value (r = 0.75) with respect to an independent data set used in the same study site. On the other hand, a simple exponential relationship was obtained for maximum air temperature and total global radiation which explains the relationship of the two variables with forest fire spread in a non-linear function.
Forest fire hazard rating system based on a system of probability of fire occurrence in Central Luzon was generated. The system classified forest areas into three categories relative to its “A Posteriori” propensity to occur forest fire based on forest cover type. These classifications were: high risk areas (Pr = 1.0 – 0.60), moderate risk ares (Pr = 0.59 – 0.20), and low risk areas (Pr = 0.00 – 0.19).
Qualitative analysis of change and related post-eruption geologic processes in Southwest Zambales, Philippines
by Jerry Hervacio G. Salvador
This paper documented and analyzed the land cover changes in southwest Zambales using three multitemporal high-resolution optical satellite data from February 1988 to April 1993. The analysis determined qualitatively what had changed, where change occurred, and where the direction or the trend of the change component was. The satellite images used were the 1988 SPOT pre-eruption image (path 302, row 320) and the 1992 and the 1993 LANDSAT Thematic Mapper (TM) post-eruption images (path 116, row 50). These images provided the basic data for the change analysis until the beginning of the 1993 rainy season.