Jinsong Wang, Jian Sun, Jianyang Xia, Nianpeng He, Meiling Li and Shuli Niu
Part of an upcoming Special Feature on Functional Traits Along a Transect!
Carbon (C) storage in terrestrial ecosystems is the balance between photosynthetic inputs and C losses by respiration. However, the large variations in the time that C stays in different ecosystem compartments (e.g. vegetation, soils) have challenged our ability to model the terrestrial C cycle and evaluate the potential of different compartments as C sinks. C turnover time , which refers to the ratio of total C stock in a reservoir to total input or output flux, is one of the most significant uncertainties in C cycle models. Therefore, estimations of vegetation and soil C turnover times are crucial to provide constraints on models of the global carbon cycle.
Forests are one of the most important ecosystems and play a critical role in the terrestrial C cycle. To evaluate how long C can be stored in soils and vegetation and what control their spatial variations at large scales, we used the data of C stocks and C influx from 2753 vegetation plots and 1087 soil plots from tropical to boreal forests in eastern China.
The results showed the shortest turnover times in the low-latitude zones and the longest values in the high-latitude zones. Soil C turnover times were mainly controlled by mean annual temperature and mean annual precipitation, while forest age was responsible for the majority of the variations in vegetation C turnover times.
Our study suggests that different mechanisms underlie above- and below-ground C turnover. The findings will be useful to inform and parameterize C cycle models and are essential to provide an insight into the sensitivity and potential response of forest C cycling to future climate change.
Structure equation modeling examining the direct and indirect effects on carbon turnover times in vegetation (left) and soils (right). Image provided by authors.