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Biotic and abiotic controls on diurnal fluctuations in labile soil phosphorus of a wet tropical forest
Author(s) -
Vandecar Karen L.,
Lawrence Deborah,
Wood Tana,
Oberbauer Steven F.,
Das Rishiraj,
Tully Katherine,
Schwendenmann Luitgard
Publication year - 2009
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/08-1516.1
Subject(s) - abiotic component , environmental science , ecosystem , ecology , nutrient , organic matter , nutrient cycle , mineralization (soil science) , oxisol , soil organic matter , environmental chemistry , soil water , soil science , chemistry , biology
The productivity of many tropical wet forests is generally limited by bioavailable phosphorus (P). Microbial activity is a key regulator of P availability in that it determines both the supply of P through organic matter decomposition and the depletion of bioavailable P through microbial uptake. Both microbial uptake and mineralization occur rapidly, and their net effect on P availability varies with soil moisture, temperature, and soil organic matter quantity and quality. Exploring the mechanisms driving P availability at fine temporal scales can provide insight into the coupling of carbon, water, and nutrient cycles, and ultimately, the response of tropical forests to climate change. Despite the recognized importance of P cycling to the dynamics of wet tropical forests and their potential sensitivity to short‐term fluctuations in bioavailable P, the diurnal pattern of P remains poorly understood. This study quantifies diurnal fluctuations in labile soil P and evaluates the importance of biotic and abiotic factors in driving these patterns. To this end, measurements of labile P were made every other hour in a Costa Rican wet tropical forest oxisol. Spatial and temporal variation in Bray‐extractable P were investigated in relation to ecosystem carbon flux, soil CO 2 efflux, soil moisture, soil temperature, solar radiation, and sap‐flow velocity. Spatially averaged bi‐hourly (every two hours) labile P ranged from 0.88 to 2.48 μg/g across days. The amplitude in labile P throughout the day was 0.61–0.82 μg/g (41–54% of mean P concentrations) and was characterized by a bimodal pattern with a decrease at midday. Labile P increased with soil CO 2 efflux and soil temperature and declined with increasing sap flow and solar radiation. Together, soil CO 2 efflux, soil temperature, and sap flow explained 86% of variation in labile P.