The high temperatures and drought conditions associated with global climate change have led to the widespread death of trees and forests, which has generated research interest in the impact of non-structural carbohydrates (NSC) reserves on woody plant survival in changing environments. The anatomical characteristics of plants can affect the scale and variability of NSC reserves, and linking the anatomical characteristics of trees to NSC concentration can help answer questions about the potential role of NSC in the repair of xylem embolism during drought.

The anatomical characteristics, NSC concentrations and gas exchange parameters were determined in 16 common afforestation tree species in typical arid limestone habitats in rocky mountain regions. We found that the anatomical structures varied greatly among the tree species studied, and a branch xylem hydraulic efficiency–safety tradeoff was not observed. NSC concentration was significantly and positively correlated with variables including mean vessel diameter (MVD), maximum vessel diameter (XVD), potential hydraulic conductivity (K_p), vessel wall thickness (VWT), ratio of palisade tissue thickness to sponge tissue thickness (PT/ST), net photosynthetic rate (P_n), water use efficiency (WUE) and axial parenchyma cell area, and negatively with sponge tissue thickness (ST) and lower epidermis thickness (LET) of leaves. Among the four latent variables, mechanical strength was inversely related to NSC concentration, whilst hydraulic efficiency, leaf carbon fixation, and the embolism repair and storage capacity all had a positive effect.

Our study revealed that tree species with larger vessel diameters, thicker vessel walls, more abundant axial parenchyma, and higher PT/ST have higher NSC storage in arid habitats in northern China. Varying xylem anatomical characteristics and leaf anatomical characteristics among different tree species lead to differentiated water transport and photosynthetic processes, thereby regulating the NSC concentrations. A higher NSC concentration may enhance the embolism repair capacity of plants and play an important role in maintaining hydraulic integrity in arid habitats.

Global climate change, characterized by changes in precipitation, prolonged growing seasons, and warming-induced water deficits, is putting increased pressure on forest ecosystems globally. Understanding the impact of climate change on drought-prone forests is a key objective in assessing forest responses to climate change.

In this study, we assessed tree growth trends and changes in physiological activity under climate change based on measurements of tree ring and stable isotopes. Additionally, structural equation models were used to identify the climate drivers influencing tree growth for the period 1957–2016.

We found that the mean basal area increment decreased first and then increased, while the water use efficiency showed a steady increase. The effects of climate warming on tree growth switched from negative to positive in the period 1957–2016. Adequate water supply, especially snowmelt water available in the early critical period, combined with an earlier arrival of the growing season, allowed to be the key to the reversal of the effects of warming on temperature forests. The analysis of structural equation models (SEM) also demonstrated that the growth response of Pinus tabuliformis to the observed temperature increase was closely related to the increase in water availability.

Our study indicates that warming is not the direct cause of forest decline, but does indeed exacerbate droughts, which generally cause forest declines. Water availability at the beginning of the growing season might be critical in the adaptation to rising temperatures in Asia. Temperate forests may be better able to withstand rising temperatures if they have sufficient water, with boosted growth even possible during periods of rising temperatures, thus forming stronger carbon sinks.