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.

Read the article in full here.

Structure equation modeling examining the direct and indirect effects on carbon turnover times in vegetation (left) and soils (right). Image provided by authors.