SYLVATROP Volume 9 No. 2 – July to December 1999 Contents:
Bani [Pongamia pinnata (L.) Merr.] anthracnose in the Philippines
by Jing Yuebo and Ernesto Militante
A new anthracnose disease of bani (Pongamia pinnata (L.L Merr.), an indigenous species of the Philippines, was first observed in the nursery of the Institute of Renewable Natural Resources (IRNR), College of Forestry and Natural Resources (CFNR) of the University of the Philippines Los Baños (UPLB). The causal agent of the disease was identified as Rhizoctonia hiemalis sp. Nov. (Saksena and Vaartaja 1960). Infected seedlings exhibited the typical symptoms, such as irregular light to dark brown dead blotches on the leaves that merge together to cause death often resulting in premature defoliation, blight, and retarded growth. The incidence of the disease was 100% with the presence of high moisture in the area.
The result of the pathogenicity test using the clip method indicated that the pathogen causing anthracnose disease of bani infected seven other species of hardwood seedlings after 3-7 days from contact with the infected leaf. These species were: mahogany (Swietenia macrophylla King), narra (Pterocarpus indicus Willd.), yemane (Gmelina arborea Juss.), bangkoro (Morinda citrifolia L.), and banaba [Lagerstroemia speciosa (L.) Pers. J. However, ipil [Intsia bijuga (Colebr.) O. Ktze], subiang (Bridelia penangiana Hook), and marang [Litsea perrottetii (Blume) F. Vill.] were not infected.
Histological examination of the bani leaf infected by R. hiemalis using the clip method revealed that the spongy layer of tissues was first attacked by the pathogen. Hyphae were found intra and intercellularly.
Phenology of selected mangrove plants under four climatic types
by Honorato G. Palis
The phenology of selected mangrove plants was monitored to determine their reproductive cycles under four climatic types. Results revealed that there were differences in the phenological dynamics, i.e., bud, flower, and fruiting stages, of the common mangrove species under investigation. Physiological adaptations and reactions to sudden weather disturbances, among others, were some of the factors responsible for variations in their reproductive cycle. Meanwhile, T-test revealed that there were significant differences on the abundance of bud, flower, and fruit as influenced by phenophases and regional climatic patterns.
Hydrologic impact of forest canopy in a secondary dipterocarp forest watershed in Norzagaray, Bulacan
by Imelda Mendoza-Diaz
The hydrology of a secondary dipterocarp forest watershed in Norzagaray, Bulacan, Philippines was investigated to determine the effects of forest canopy on the hydrological processes within a watershed. Monitoring of rainfall, streamflow, throughfall, stemflow, and some climatological elements such as temperature, relative humidity, evaporation, and wind speed was carried out from October 1, 1998 to January 31, 1999.
The study revealed that water loss through interception was influenced by the amount of rainfall and the density of the crown area. As observed, the average monthly rainfall interception in the secondary dipterocarp forest is 58.9%.
Forest canopy affected the distribution of rainfall as it moved down to the ground. Gross rainfall was redistributed in three major ways: interception of the raindrops by leaves and branches, rain falling unhindered through and dripping from crowns as throughfall, and water concentrated by stems and branches flowing down the trunks as stemflow.
Positive linear relationship was observed between rainfall and throughfall with r2 = 0.86 and rainfall against stemflow with r2 = 0.62. This means that increase in the amount of rainfall will result in increased throughfall and stemflow values.
Two watersheds, a secondary dipterocarp forest and a grassland area, with similar cimatic conditions but with different vegetative cover, were compared in terms of rainfall-streamflow relationship.
For grassland, the mean monthly values for streamflow, actual evapotranspiration, change in soil moisture storage, and change in groundwater recharge were 41.6%, 40.6%, -0.2%, and 18.0%, respectively. Canopy interception was not considered. For dipterocarp forest, the following values in percent were obtained: 31.88, 58.34, 41.17, -0.10, and -31.31 for streamflow, canopy interception, actual evapotranspiration, change in soil moisture storage, and change in groundwater recharge, respectively.
The overall results illustrated that the important role of the forest canopy was to prolong the material time over which rain reaches the soil, thus, lessening surface runoff and flash flood.
Likewise, the study proved that forest canopy, an inherent characteristic of dipterocarp forest, influenced the hydrologic response of a watershed through its modifying effect in the storage and utilization of rainfall and its role in regulating the flow of regime. This made the forest a more suitable watershed cover than grassland.
Incidence of new seed-borne disease of kamagong [Diospyros philippinensis Des. (Gurke)] seeds
by Maria P. Dayan
Preliminary study on the cause of a new seed-borne disease of kamagong or mabolo (D. philippinensis) was conducted. The disease was found to be seed-borne causing the rupture of the seed coat once the “basidiocarp” emerges. A reduction in percent germination of the seeds from 98% to 68% was observed.
Based on the morphological and anatomical structures, the corraloid and club-shaped basidiocarps pathogen belong to Clavaria sp. Pure culture isolation of the pathogen showed similar fruiting structures with the observed from affected kamagong seeds.
Estimating the proportion of spring- and autumn-spawned herring using otolith microstructure
by Bileynnie R. Ponce-Encarnacion
Otolith microstucture can now be used as a tool in ageing, growth rate study, life history, and behavioral pattern of fishes. The difference in increment width of the examined sagittae was the basis in separation. The results indicated the presence of only one stock of herring using the average increment width value of 1.4 Ã?Âµm as separation criterion. High consistency of readings was observed when read by two readers and by one reader at two different times.