EFFECTS OF LOGGING ON PHOSPHORUS POOLS IN A TROPICAL RAINFOREST OF BORNEO

Abstract

Imai N, Kitayama K & Titin J. 2012. Effects of logging on phosphorus pools in a tropical rainforest of Borneo. We quantified the amount of various phosphorus (P) fractions in a tropical lowland rainforest of Borneo and estimated the potential effects of selective logging on the P availability during the following regrowth period through the export of P as timber. Ecosystem pools of P (sum of aboveground vegetation, standing litter, roots and soils to 1 m deep) and of simultaneously quantified nitrogen (N) and carbon (C) were 3.4, 11.5 and 365 Mg ha^-1 respectively. Only 2.6% of the total ecosystem P was in the aboveground vegetation, unlike C (61%) and N (16%). Soil P largely consisted of recalcitrant occluded fractions (78–91%) and only 4% was labile (bicarbonate-extractable). The concentration of labile organic P, acid phosphatase activity and fine root biomass were greatest in the topsoil (top 5 cm) and decreased with depth, suggesting that the supply of P to plants took place mainly in the topsoil. The amount of total P which was exported out as timber from the ecosystem by heavy selective logging was estimated at 24.0 kg ha^-1, while the amount of labile P in the topsoil was 12.8 kg ha^-1, indicating that the labile P might become deficient by more than
12 kg ha^-1 for biomass recovery. Our results imply that excessive logging can induce P-limitation of post-logging biomass recovery.