LAUSR

AimsSoil hydrolysable P can be a main P source for biota in P-limited tropical rain forests. Soil hydrolysable P occurs in various chemical fractions, including, monoester P, diester P, pyrophosphate and phytate, which need enzymatic hydrolysis into orthophosphate before their assimilation into biota. We examined whether P-limited plants and microbes preferentially hydrolyzed specific fraction of soil hydrolysable P and whether those in different successional stages had different abilities to hydrolyze various soil hydrolysable P.MethodsWe measured four classes of phosphatase (phosphomonoesterase, PME; phosphodiesterase, PDE; pyrophosphatase, PyP; and phytase, PhT) activities for fine-roots and soils in nitrogen (N) and P fertilized primary and secondary tropical rain forests in Sabah, Malaysia.ResultsP fertilization reduced PME, PyP and PhT activities for fine-roots and PME and PyP activities for soils. Fine-roots in primary forests had higher PME and PyP activities whereas those in secondary forests had higher PhT activities.ConclusionsWe suggest that P-limited trees and microbes depend more on hydrolysable P degraded by one step of enzymatic reaction (monoester P, pyrophosphate, and phytate) as a P source. We also suggest that trees have different soil-organic-P acquisition strategies in association with their life history strategies.