Precipitation has dominant influences on the variation of plant hydraulics of the native Castanopsis fargesii (Fagaceae) in subtropical China

Abstract

Understanding the roles of climate and intraspecific phylogeny in affecting the variation of plant hydraulics can provide insights into species distribution in different habitats. In the present study, we quantified ten functional traits characterizing branch and leaf hydraulic architecture of Castanopsis fargesii from 12 populations along a precipitation gradient (1120–1690 mm y−1), covering an 1800-km-long west-center-east transect in the subtropical region of China. We also conducted phylogenetic analyses to test the role of intraspecific phylogeny in affecting the variation of hydraulic architecture. We found that, with decreasing precipitation, branch vessel density remained unchanged while hydraulically weighted vessel diameter (Dh) declined by 31.9%, leading to a 74.3% reduction in theoretical hydraulic conductance (Kth). In parallel, leaf vein density (VD) and stomatal pore area index (SPI) declined by 14.6% and 29.9%, respectively. Leaf turgor loss point also declined significantly from −1.51 to −2.29 MPa along the precipitation gradient. In addition, functional traits related to hydraulic efficiency (i.e. Kth, Dh, VD and SPI) were positively correlated, whereas both trait variation and trait-trait correlations were not significantly affected by intraspecific phylogeny, as indicated by the values of Blomberg’s K < 1 and the consistency between principle component analysis and phylogenetic principle component analysis. We conclude that, hydraulic architectures of branch and leaf in C. fargesii varied remarkably under the primary influence of precipitation, suggesting that this subtropical tree species has a high degree of plasticity in terms of hydraulic adjustment, allowing it to cope with shifts in precipitation under future climate change.