Relationship of Soil Fertility to Aboveground Biomass of Rain Forest Trees at Puerto Princesa Subterranean River National Park.

Abstract

The relationship between biomass soil fertility and aboveground is an important but poorly understood component of a tropical rain forest. No consistent trend connecting the two has been established in past studies (Castilho et al., 2006; Oren et al., 2001; Ashton and Hall, 1992; van Schaik and Mirmanto, 1985). To elucidate relationship between aboveground biomass and soil fertility, bivariate Spearman correlation analyses were done between aboveground biomass and each of the 11 soil fertility parameters (N, P, K, Ca, and Mg nutrients; %clay, %sand, and %silt texture components; pH; organic matter; water holding capacity) from 17 sampling plots located along the trail of Puerto Princesa Subterranean River National Park. Aboveground biomass was estimated using Brown’s moist forest allometric equat ion (1997). Sampled soils were sent to Bureau of Soil and Water Management for evaluation of soil fertility parameters. Across all plots, 89% of the total aboveground biomass was observed from 7 of 170 trees. Soil nutrients were low (N=0.11±0.04%, P=0.43±0.78 ppm, K=0.19±0.10 meg/100g soil, Ca=6.74±7.03 meg/100g soil, Mg=1.25±0.75 meg/100g soil), while organic matter content (7.48±4.99%) and water holding capacity (52.46±6.33%) were high. The soil was acidic (pH 5.25) and was clayish (40.19%). The results obtained typify a lowland moist tropical rain forest that is already at climax ecological succession. No sufficient evidence shows the correlation between aboveground biomass and every soil fertility parameter in the study site. Biomass accumulation in climax forest is not affected by the fertility of the soil.