了解干旱内陆河流域生态系统中碳和水汽通量的动态对于预测和评估气候变化中的区域碳水收支至关重要。然而,旨在揭示干旱地区不断变化的环境中驱动区域碳水收支变化和耦合过程的机制的研究是有限的。这里,我们使用涡流协方差技术分析了上游三个典型生态系统中CO2和H2O通量之间的关系,中间,和中国西北部干旱内陆河流域的下游。我们的结果表明,所有的生态系统都是碳汇,在高山沼泽草地上,农田,和沙漠灌丛分别为-300.2±0.01、-644.8±2.9和-203.7±22.5gCm-2yr-1。在生长季节,空气温度(Ta)主要控制灌溉农田的每日总初级生产力(3GPP)和净生态系统CO2交换(NEE),而土壤温度(Ts)和蒸汽压赤字(VPD)调节了高山沼泽草甸和沙漠灌木丛中的这些参数。此外,Ta和净辐射(Rn)控制了农田的日蒸散量(ET),而Ts和Rn在其他位点调节ET。因此,在生长季节,所有三个生态系统的碳和水蒸气通量往往受到能量限制。上部碳和水蒸气通量的差异响应,中间,这些生态系统的下游与生物物理因素决定了它们在水分利用效率上的不同耦合和变化。值得注意的是,流域下游的荒漠灌木生态系统在碳增益和水损失之间保持了稳定的平衡,表明适应干旱。这项研究为干旱流域生态系统中碳和水蒸气通量变化以及水利用效率变化背后的潜在机制提供了宝贵的见解。
Understanding the dynamics of carbon and water vapor fluxes in arid inland river basin ecosystems is essential for predicting and assessing the regional carbon-water budget amid climate change. However, studies aiming to unravel the mechanisms driving the variations and
coupling process of regional carbon-water budget in a changing environment in arid regions are limited. Here, we used the eddy covariance technique to analyze the relationship between CO2 and H2O fluxes in three typical ecosystems across the upper, middle, and lower reaches of an arid inland river basin in Northwestern
China. Our results showed that all ecosystems acted as carbon sinks, with the alpine swamp meadow, cropland, and desert shrubland sequestrating -300.2 ± 0.01, -644.8 ± 2.9, and - 203.7 ± 22.5 g C m-2 yr-1, respectively. Air temperature (Ta) primarily controlled daily gross primary productivity (GPP) and net ecosystem CO2 exchange (NEE) in the irrigated cropland during the growing season, while soil temperature (Ts) and vapor pressure deficit (VPD) regulated these parameters in the alpine swamp meadow and desert shrubland. Additionally, Ta and net radiation (Rn) controlled daily evapotranspiration (ET) in cropland, while Ts and Rn regulated ET at other sites. Consequently, carbon and water vapor fluxes of all three ecosystems tended to be energy-limited during the growing season. The differential responses of carbon and water vapor fluxes in the upper, middle, and lower reaches of these ecosystems to biophysical factors determined their distinct
coupling and variations in water use efficiency. Notably, the desert shrub ecosystem in the lower reach of the basin maintained a stable balance between carbon gain and water loss, indicating adaptation to aridity. This study provides valuable insights into the underlying mechanisms behind the changes in carbon and water vapor fluxes and water-use efficiency in arid river basin ecosystems.