The effects of temperature on soil phosphorus availability and phosphatase enzyme activities: a cross-ecosystem study from the tropics to the Arctic

摘要

Earth system models predict large increases in global terrestrial net primary productivity (NPP) over the next century, largely reflecting positive effects of climate change and increasing atmospheric carbon dioxide concentrations on plant growth. However, while theory predicts that soil phosphorus (P) availability may keep pace with P demand as the climate warms, we lack experimental evidence to support this prediction. Here, using a set of laboratory experiments and incubations, we measured both the effect of temperature on the mechanism of biochemical P mineralization-phosphatase (Ptase) enzyme activities-and on rates of soil P mineralization in soils from a range of ecosystem types from the tropics to the Arctic. Consistent with temperature effects on soil nitrogen (N) mineralization, we found that both Ptase activities and P availability in soil increased with temperature following macromolecular rate theory (MMRT) based kinetics. However, across all sites and temperatures, there was no relationship between Ptase activity and mineralized P, indicating that the potential responses of P mineralization with warming vary among ecosystems. The lack of relationship between Ptase and P availability with increasing temperature is consistent with previous work showing that P mineralization rates are also strongly affected by other biotic and abiotic factors, including organic P substrate availability and the geochemical properties of soil. However, our results indicate that the use of Ptase temperature kinetics alone as a proxy for soil P mineralization in terrestrial ecosystems is insufficient to predict future P availability accurately, and modeling efforts that do so will likely overestimate the effects of temperature on soil P availability.