Species-specific coupling of tree-ring width and litter production in a temperate mixed forest

Abstract

Tree growth is delineated into multiple processes, such as foliar growth, stem growth, and reproductive growth; however, only stem growth can store carbon in forests at a relatively long time scale. Understanding how these processes interact in response to climate change is of utmost importance for predicting the future carbon fixation ability of forests. However, it largely remains an unresolved question. To bridge this knowledge gap, we collected litter and tree-ring samples of two deciduous tree species, i.e. Larix principis-rupprechtii and Quercus liaotungensis, in a temperate mixed forest on Dongling Mountain in northern China. The influence of climate and the coupling characteristics between leaf/needle litter, fruit/cone litter, and tree-ring width (TRW) were analysed. The results highlighted that leaf/needle production was significantly and positively coupled with TRW for both species, but with one-year time lag for larch. Path analysis revealed that climate changes directly and significantly affected fruit production, which in turn indirectly affected TRW for oak trees, but such effect of cone production on TRW was not significant for larch trees. Additionally, we found that the radial growth of oak trees is more sensitive to drought stress than larch, possibly due to the close coupling between leaf biomass and TRW. Our results demonstrated that the coupling characteristics between different components of tree growth are species-specific, and understanding these relationships is of great significance for improving the tree growth model of forest ecosystems.