Volume 9 No. 1

Climate variability in the Angat watershed, Bulacan, Philippines (1970-1997)
by Santiago R. Baconguis and Liza I. Cañete-Ranes
Analysis was made for the daily rainfall (1970-1997) and air temperature (1974-1997) records at the dipterocarp forest catchment of the Angat watershed in San Lorenzo, Norzagaray, Bulacan. The area is considered a representative of the elevation of dipterocarp forests in the country and belongs to Climatic Type I based on the Coronas' (1920) system of classification.
Data showed that there was an increasing trend in temperature, an evidence of warming during the recent years. The mean annual temperature during the intervening years (70s, 80s, 90s) was 26.9oC, 27.1oC and 27.5oC, respectively, with 1997 being the hottest with an annual mean temperature of 28.2oC. The 1997 value was 1.0oC higher than the mean annual temperature and 0.7oC higher than the mean annual temperature in the 90s.
Annual rainfall varied from year to year with an annual average of 3,198.0 mm. The 1997 rainfall was about 32% below the annual average. During the study period, there were twice as many El Niño years than La Niña.
Fungi associated with Anisoptera thurifera (palosapis) seeds and their control
by Maria P. Dayan
Fungi associated with A. thurifera (palosapis) seeds and the effect of fungicides, storage temperature and length of storage on fungal infection, germination and MC of the seeds were studied. Seven fungal species namely: Lasiodiplodia theobromae, Macrophomina phaseolina, Fusarium oxysporum, F. Moniliforme, F. semitectum, Phoma sp. and Colletotrichum gloesporioides were identified. Captan fungicide at the rate of 2.5 a.i./kg of seeds reduced infection from 21-4%, when seeds were stored at 29oC but germination decreased as storage period increased to 42 days. Zero germination was observed for all treatments after one week of storage at 10oC. The MC of the seeds differed only during the first week of storage at both storage temperatures. Beyond seven days, changes in the MC were insignificant.
Field performance of Eucalyptus urophylla inoculated with introduced and indigenous strains of ectomycorrhizal fungus Pisolithus
by Nelly S. Aggangan, Bernie Dell, Nicholas Malajczuk, and Reynaldo E. de la Cruz
The effectiveness of an isolate of Pisolithus from Australia was compared with a Philippine Pisolithus isolate in promoting the growth of Eucalyptus urophylla on three acid (pH ranged from 4.1 to 5.9, 0005 M CaCI2) sites in the Philippines (Pangasinan, Bukidnon and Surigao). Isolates of Pisolithus were taken from basidiocarps collected under eucalypts growing in Western Australia and from the Philippines.
Generally, the introduced Pisolithus promoted greater wood volume of E. urophylla planted in dry marginal land (Pangasinan) and in moist logged-over area (Surigao) in the Philippines than the Philippine Pisolithus isolate. Root colonization by the two fungi did not vary but there was a difference in the root colonization levels between sites implying that the prevailing microclimatic conditions on each site had affected the performance of the ECM inoculants. In this study, the number of isolates tested was limited, thus, future field trials should include a wider range of ectomycorrhizal fungi. Further work is required to determine whether the growth responses measured in the two sites (Pangasinan and Surigao) is maintained until the trees are harvested and to monitor the persistence of the introduced mycorrhizal fungi in the field.
The effects of hydrogen peroxide in the cyanide leaching of gold
by Glenn Marcelo C. Noble
Electrochemical studies and leaching of gold particles were employed to evaluate the effectiveness of the peroxides in increasing the leaching rate and the extent of gold dissolution. A rotating disc electrode system was used for electrochemical measurements where scanning voltammetry was applied to study the different factors which influence the two half-cell reactions involved in the process: the oxidation of gold and the reduction of hydrogen peroxide. The effects of variables such as cyanide concentration, pH, amount of hydrogen peroxide addition, temperature and stirring rate were determined.
Leaching of gold particles in a diluted cyanide solution was conducted to determine and compare the effect of hydrogen and calcium peroxide addition on the dissolution of gold. Evans diagrams constructed from electrochemical studies indicate that dissolution of gold in cyanide solution with hydrogen peroxide was controlled by a kinetic step. The equilibrium potential difference between the oxidation of gold and reduction of hydrogen peroxide was less than 0.36V. A value greater than this was recognized by Power and Ritchie (1979) as a useful criterion for diffusion control. Increasing the hydrogen peroxide and cyanide condentration shifted the intersection of the anodic and cathodic curves to a higher current density which in turn increased the dissolution rate. At a pH range of 9.00 to 11.00 and constant concentration of cyanide, the reduction of hydrogen peroxide is not greatly affected while the oxidation of gold increases accordingly with increasing pH. The effect of the change in pH is very evident from pH 9.00 to pH 10.00 - most likely due to increase in stability of free CN-ions above a pH of 9.21. The effect of temperature variation was more pronounced with the oxidation reaction than with the reduction reaction. Increase in temperature also resulted in the increase in the dissolution reaction. Results also show that dissolution rate of gold in cyanide solution increased with increasing hydrogen peroxide concentration. This can be accounted for by the increase in dissolved oxygen levels in the solution which in turn accelerated the dissolution reaction.
Survey and identification of mangrove diseases
by Veronica O. Sinohin
Field survey and identification of mangrove diseases were conducted at the Mangrove Reforestation Project at the Manila-Cavite Coastal Road. Five foliar diseases were identified namely; brown leaf spot on Rhizophora styloza (bakawan bato) caused by Pestalotia sp.; leaf spot caused by Colletotrichum sp. on R. apiculata (bakauan lalake) and Sonneratia caseolaris (pagatpat); tip blight on R. mucronata caused by Colletotrichum sp. and mosaic disease on R. styloza, possibly caused by a virus. Pathogenicity tests for Pestalotia sp. and Colletotrichum sp. were positive. Symptomatology og the diseases are presented.