Temperature dependence of ecosystem carbon, nitrogen and phosphorus residence times differs between subtropical and temperate forests in China
2022
Chen, Yang | Wang, Yingbing | YuanyuanHuang, | Tang, Xuli | Zhou, Guoyi | Wang, Chen | Chang, Zhongbing | Yan, Junhua
Residence times of ecosystem carbon (τₑ,C), nitrogen (τₑ,N) and phosphorus (τₑ,P) are closely related to efficacies of carbon and nutrients conservation within an ecosystem. However, estimates of τₑ,C, τₑ,N and τₑ,P together are very limited for forest ecosystems, and little is known about the environmental controls. Here we estimated τₑ,C, τₑ,N and τₑ,P of 127 undisturbed forests based on observed carbon, nitrogen and phosphorus stocks and compiled 30 key variables related to climate, vegetation, soil and terrain for the sites. We then performed a variation partitioning analysis to identify dominant controls on τₑ,C, τₑ,N and τₑ,P, and used segmented regression to identify possible thresholds in the dependence of τₑ,C, τₑ,N and τₑ,P on temperature. Climate, particularly average minimum temperature of the coldest month of a year (Tₘᵢₙ), was the main driver of τₑ,C, τₑ,N and τₑ,P. In regions with Tₘᵢₙ < 0 °C, τₑ,C and τₑ,P decreased with increasing Tₘᵢₙ; and in regions with Tₘᵢₙ > 0 °C, both τₑ,C and τₑ,P increased with increasing Tₘᵢₙ, as a result of a significant increase in total ecosystem carbon pool and a decrease in external phosphorus input, respectively. Our results challenge the use of a single temperature-dependent function of ecosystem carbon or nutrient turnover rate in global land models, and highlight the importance of other factors, such as soil weathering stage, clay content, in influencing the responses of carbon and nutrients cycles in subtropical forests to global warming.
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