Wang Yue, Gao Guangyao, Huang Yanzhang, Wang Zhuangzhuang, Fu Bojie
State Key Laboratory for Ecological Security of Regions and Cities, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory for Ecological Security of Regions and Cities, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China; Shaanxi Yan'an Forest Ecosystem Observation and Research Station, Beijing 100085, China; National Observation and Research Station of Earth Critical Zone on the Loess Plateau in Shaanxi, Xi'an 710061, China.
Sci Total Environ. 2025 Feb 10;964:178575. doi: 10.1016/j.scitotenv.2025.178575. Epub 2025 Jan 22.
Ecosystem water use efficiency (WUE) and carbon use efficiency (CUE) are critical parameters to determine the trade-off between water consumption and carbon sequestration in drylands. However, the roles of vegetation cover, climate factors and soil moisture in affecting the coupling of WUE and CUE were still poorly understood. This study combined the spatial random forest model and structural equation model to detect the drivers of WUE and CUE variations in China's Loess Plateau during 2001-2020, a typical water-limited region with about 87 % of area experiencing significant vegetation greening. The WUE increased significantly (P < 0.05) in 92.7 % of the greening area (0.024 ± 0.020 gC kgHO yr), and CUE decreased (-0.0011 ± 0.0011 yr) and increased (0.0010 ± 0.0012 yr) slightly in half and half of the greening area. The vegetation greening trend was a dominant factor positively influencing the variation of WUE (with 42.0 % explanation), whereas CUE exhibited a negative response to the greening trend (with 25.0 % explanation). However, the regions with dense vegetation cover (NDVI >0.5) were unfavourable for the increase of WUE but favourable for the increase of CUE. Vegetation greening exerted effect on WUE mainly via the path of gross primary productivity and ratio of transpiration to evapotranspiration (path coefficient: 0.83), whereas it had direct effect on CUE (path coefficient: 0.48). An increase in VPD facilitated the enhancement of both WUE and CUE. There was an optimal annual precipitation range (400-600 mm) that maximized WUE enhancement, and annual temperature (∼10 °C) optimized CUE increase. The findings indicate that despite the improvement in WUE, the vegetation greening may not necessarily enhance carbon sequestration potential in drylands. This study enhances the knowledge of the interaction between vegetation dynamics and water‑carbon coupling in drylands, contributing to ecological restoration practices and sustainable ecosystem management.
生态系统水分利用效率（WUE）和碳利用效率（CUE）是确定干旱地区水分消耗与碳固存之间权衡关系的关键参数。然而，植被覆盖、气候因素和土壤湿度对WUE和CUE耦合的影响作用仍知之甚少。本研究结合空间随机森林模型和结构方程模型，以检测2001 - 2020年中国黄土高原地区WUE和CUE变化的驱动因素，该地区是典型的水分受限区域，约87%的面积经历了显著的植被绿化。在92.7%的绿化区域（0.024±0.020 gC kgH₂O yr），WUE显著增加（P < 0.05），而在绿化区域的一半中CUE略有下降（-0.0011±0.0011 yr），在另一半中略有增加（0.0010±0.0012 yr）。植被绿化趋势是对WUE变化产生积极影响的主导因素（解释率为42.0%），而CUE对绿化趋势表现出负面响应（解释率为25.0%）。然而，植被覆盖密集（归一化植被指数>0.5）的地区不利于WUE的增加，但有利于CUE的增加。植被绿化主要通过总初级生产力和蒸腾与蒸散比的路径对WUE产生影响（路径系数：0.83），而对CUE有直接影响（路径系数：0.48）。水汽压差（VPD）的增加促进了WUE和CUE的提高。存在一个最佳年降水量范围（400 - 600毫米），可使WUE的提高最大化，年平均温度（约10°C）使CUE的增加最优化。研究结果表明，尽管WUE有所改善，但植被绿化不一定能增强干旱地区的碳固存潜力。本研究增进了对干旱地区植被动态与水 - 碳耦合相互作用的认识，有助于生态恢复实践和可持续生态系统管理。
