Global sensitivities of forest carbon changes to environmental conditions 

Abstract

<p>Quantifying the responses of forest dynamics to fluctuations in the atmosphere, hydrosphere and land surface conditions at global scales have been rather challenging. Despite the understanding that favourable environmental conditions promote forest growth, the effects have been challenging to observe across different ecosystems and climate gradients. Based on a global annual time series of aboveground biomass (AGB) from 1992 to 2018, we present forest carbon changes and provide insights on the controls of atmospheric (e.g., climate), hydrosphere (e.g., soil water availability) and land surface (e.g., changes in forest cover) conditions on forest carbon changes from local to global scales. Our findings indicate a gradient of forest gains and losses across AGB classes, with regions with carbon stocks of 50-100 MgC ha<sup>-1</sup> depicting both the highest forest gains and losses. Furthermore, we observe that changes in forest carbon stocks were systematically positively correlated with changes in forest cover, while it was not necessarily the case with other environmental variables, such as air temperature and water availability at the uni-variate level. We also used a gradient boosted decision tree model and a variable importance metric (i.e., SHAP values) to demonstrate that atmospheric conditions largely dictate forest carbon changes followed by land surface and hydrosphere conditions. Interestingly, the observed functional relationships indicate a strong sensitivity of forest carbon changes to recent-past carbon stocks and both recent-past and concurrent atmospheric water demand. Regionally, we find evidence that carbon gains from long-term forest growth covary with long-term carbon sink inferred from atmospheric inversions at the ecosystem level. Our study quantifies the contributions from the atmosphere, hydrosphere, and land surface conditions to forest carbon changes and provides new insights into the underlying mechanisms of forest growth on the global carbon cycle.</p>

Plant diversity drives soil carbon sequestration: evidence from 150 years of vegetation restoration in the temperate zone

“…However, it is important to note that soil carbon sequestration was mainly driven by woody plant diversity during the 150 years of natural recovery of temperate vegetation. This indicated the significant role of forests in carbon sequestration, not only in the ground but also in carbon input to the soil, a view that is widely shared (Besnard et al, 2021;Ding et al, 2021). As shown by the direct relationship in PLS-PM (Figure 6A), SOC accumulation was mediated by woody plant diversity through increased proportions of large soil aggregates and other hitherto unidentified mechanisms.…”

“…Carbon sequestration is a key ecosystem function influenced by plant diversity (Bartelt-Ryser et al, 2005;Isbell et al, 2018). Forests are an important component of the global carbon cycle as they store 70-90% of terrestrial above and belowground biomass and are a major carbon sink, which is strongly linked to the diversity of plants in different forest types (Aponte et al, 2020;Besnard et al, 2021). There is much uncertainty about whether tropical forests are carbon sinks or sources, while temperate forests are known to play a significant role as terrestrial carbon sinks (Clark, 2004;Yang et al, 2022).…”

Effects of climate change and land use/cover changes on carbon sequestration in forest ecosystems in the coastal area of China

“…Therefore, accurately quantifying the carbon sequestration of forest ecosystems is critical to enact effective measures to mitigate global warming. Climate change strongly regulates the carbon sequestration of terrestrial ecosystems by affecting photosynthesis and respiration processes (Besnard et al, 2021). Previous studies have found that increasing temperatures extend the vegetation growth period, promote vegetation productivity, and strengthen carbon sequestration (Post et al, 2018;Cheng et al, 2021).…”