Vegetation and soil fertility analyses of six- and thirteen-year old fallow areas in the Mt. Makiling Forest Reserve, Calamba City[Philippines].

Two sites undergoing Kaingin[swidden system] fallow period for 13 and 6 years, respectively, in Mt. Makiling Forest Reserve in Puting Lupa, Calamba City[Philippines] were selected for this study. Using the line transect method, vegetation analysis was done for plants with heights 2 m and below. Actual counting of individuals of species was done for plants with heights greater than 2 m. Line transect method was done twice with an 11 month interval while tree count was done only once. Soil nutrient analyses and monitoring of physical factors of the environment were also done during the two sampling periods. Samplings were done in May 2002 and April 2003. The two sites have a 54% index of similarity of species. This was due to the presence of similar species like Leucaena leucocephala (Lam) de Wit, Gliricidia sepium (Jacq.) Walp, Ervatamia pandacaqui (Poir) Mich., Ficus septica Burm. F., Acalypha amentacea Roxb., Arenga pinnata (Wumb) Merr. and Cargutta cumingii Lodd. Also most of the species located in both sites belong to the Moraceae, Euphorbiaceae and Arecaceae. A total of 88 species belonging to 80 genera under 44 families were identified. The similarity of the two sites indicates that the 6-year fallow area is a younger stage of the 13-year fallow area. The two sites have a 55% similarity to that of the secondary forest in Buot, College of Forestry, UPLB located on the eastern side of Mt. Makiling. The soil samples were analyzed for pH, % soil organic matter, % soil moisture, % total nitrogen, available phosphorus, and exchangeable potassium. Physical factors of the environment monitored include light intensity, soil and air temperature and relative humidity. Results of the soil analyses showed that soil pH and phosphorus were significantly higher in the 13-year fallow than in the 6-year fallow area. The % soil organic matter content, available phosphorus and exchangeable potassium were also higher in the 13-year fallow than in the 6-year fallow area though the differences were not significant. The 6-year fallow area had a higher species richness and indices of diversity compared with the 13-year fallow area. The 6-year fallow has thinner canopy and is more open thus ample amount of light penetrated the under story, allowing new species to enter.