Volume 12 Nos. 1 & 2
Diagnosis, identification, and control of malapapaya [Polyscias nodosa (Blume) Seem] seedling diseases in the Teraoka Farm nursery
Diseases attacking malapapaya (P. nodosa) seedlings in the Teraoka Farm nursery were studied. Three important diseases and the associated organisms were identified, namely: leaf spot and stem lesion with the associated fungus Colletorichum gloeosporioides and root rot with the associated fungi Fusarium solani and Rhizoctonia solani. Fungicidal treatment using Benlate and Captan at the rate of 3 g/L of water at weekly interval totally eradicated leaf spot and stem lesion. Sterilization of potting medium for 4 hrs completely controlled the root rot disease.
Comparison of the mass loss rates and nutrient dynamics of decaying Acacia mangium, A. auriculiformis, and Samanea saman leaf litter
The mass loss rates and nutrient dynamics of decaying Acacia mangium, A. auriculiformis, and Samanea saman leaf litter were monitored for 12 months using the litterbag method. The study aimed to: (1) determine the influence of initial substrate quality on the mass loss rates of forest leaf litter and (2) to describe the behavioral movements of nutrient elements of decomposing litter. Results showed that different litter types have different decay rates (p < 0.001) because they have different initial substrate qualities. Samanea saman decomposed faster than A. auriculiformis (p < 0.001) while A. auriculiformis and A. mangium are comparable (p > 0.05). The three leaf litter had different decay rate constants (0.91, 0.81, and 0.73, for Samanea saman, A. auriculiformis and A. mangium, respectively). Mass losses were high during the first three months of incubation, which coincided with the rainy season and losses were attributed to leaching of labile and water soluble materials brought about by rainfall as mass loss was very highly correlated with the cumulative amount of rainfall (r = 0.99). Total nitrogen concentration of the leaf litter was the best predictor of mass loss (p < 0.001), better than other litter qualities that were tested. Among the species studied, Samanea saman appeared to have the best initial leaf litter quality, having the highest concentrations of N and least C-N ratio, followed by A. auriculiformis and A. mangium. Nutrient mobility in decomposing litter differs among species and elements. Concentrations of some elements had increased but their masses had decreased with the exception of phosphorus, manganese, and most micronutrients. The decrease in nutrient masses is attributed to the loss in litter mass. When the increase in concentration is more than the decrease in litter mass, there is a tendency for such element to increase its nutrient mass in spite of a decrease in litter mass. The concentrations of all elements had almost increased and/or fluctuated except for K, which decreased through time. The trends of both mass losses and nutrient mobility are in agreement with previous studies. Results of this study may enhance the understanding of the nutrient cycling of some of the reforestation species in the Philippines. An understanding of the nutrient dynamics of important reforestation species would provide a good management tool in the nutrient management of a plantation. This is also important in agroforestry systems particularly in the synchrony of nutrient release and plant demand.
Underplanting guijo (Shorea guiso) and yakal (S. astylosa) wildlings in three different forest covers at Tadao Experimental Forest
The growth and survival of guijo (Shorea guiso) and yakal (Shorea astylosa planted under three different forest covers in Tadao, Pasuquin Experimental Forest were assessed over a three-year period.
The survival rate of S. guiso and S. astylosa was significantly better in Acacia mangium and A. auriculiformis plantations than in a secondary forest.
A significant effect of forest covers was also noted on the height/diameter growth and increment of S. guiso and S. astylosa.
Light intensity was significantly correlated to the survival, height, and diameter of the two dipterocarp species.
Coral reef mapping by remote sensing techniques in Bolinao, Pangasinan, Philippines
Mapping of the fringing reef of Bolinao, Pangasinan, Philippines was conducted using remote sensing techniques and data, particularly the Landsat TM data. The mapping classes used include reef slope, reef flat, sea grass, and seaweed. The image was classified by visual interpretation and by automated classification using the maximum likelihood classifier. Both techniques are useful for mapping information classes that are relatively homogenous and are widely distributed.
The classification estimates of the major information classes using the maximum likelihood classifier are reef slope (232 km2) and reef flats (202 km2). The reef flats include sea grasses (60 km2) and seaweeds (24 km2). Sea truth survey verified the identity and general distribution of these mapped features. The results of this study contributed to the baseline mapping of coral reef areas in the Philippines using remote sensing techniques. In the future, when more remotely sensed data become available for analysis, changes in the distribution of the bottom covers and mangroves can be determined and compared.
Status of coral reefs of selected marine sanctuaries in Central Visayas, Philippines
Ten marine sanctuaries were monitored by the Coastal Environment Program (CEP) of the Department of Environment and Natural Resources (DENR), Region 7 from 1996 to 2001, using Line Intercept Transect method to assess the status and trend of coral reefs and generate information for coastal resources management. In 1997, there was a slight increase of live hard coral cover ranging from 0.26% to 17.41% in terms of percentage cover. However, most of the live hard coral cover had declined drastically in 1998 ranging from 1.11% to 100%. The highest decline among the ten marine sanctuaries was observed in Sulungan Marine Sanctuary in Bantayan, Cebu registering 100% in 1998. Other sanctuaries like Apo Island in Dauin, Negros Oriental, and Lomboy in Calape, Bohol, have declining % live coral cover from 1997 to 1999. The decrease of live coral cover in 1998 was attributed to the El Niño phenomenon. Coral reefs exposed to warm water or sea-surface temperature experienced moderate to severe coral bleaching.
Effects of hedgerows on surface runoff, soil erosion, and food crop production
The study determined the effect of different vegetative hedges on surface runoff, soil erosion, and vegetable crop yield; the effect of established hedgerows on air and soil temperature, pH, nitrogen, phosphorus, and potassium; the survival and mortality of the experimental hedgerows; and litterfall production and decomposition rate. The study site is within the degraded upland farms of Taloy Norte, Tuba, Benguet with a mean elevation of 860 meters above sea level (m asl) and a slope gradient ranging from 30% to 40%.
The different hedgerows planted in the study area were lantana (Lantana camara), trunpet flower (Datura arborea), sunflower (Tithonia diversifolia), and binataang hambog (Malvaviscus arborea).
In 1993, effecting the highest surface runoff and soil erosion was binatang hambog, the highest vegetable crop yield was trumpet flower, and the highest litterfall was sunflower.
In 1994, the treatment with the highest surface runoff and soil erosion was binatang hambog; the highest crop yield, decomposition rate, and sprout production was trumpet flower; and the highest litterfall was sunflower. The effect of different hedgerows planted was effective as vegetative measures for degraded upland farms. After one year or more, soil movement/loss was reduced.