黄土高原粮草复合生态系统蒸散发变化动态及其与干旱的关系

Dynamics of evapotranspiration and its relationship with drought in a grain-forage compound ecosystem on the Loess Plateau

蒸散发是生态系统水循环的重要环节,直接或间接影响土壤水分、植物生长和生态系统碳循环等过程。蒸散发也极易受极端气候的影响,了解气候变化情景下生态系统蒸散发变化动态及其调控机制,对于区域水资源管理和生态恢复至关重要。本研究以黄土高原典型粮草复合生态系统为研究对象,采用涡度相关连续监测法,分析了粮草复合生态系统蒸散发季节变化动态及其与夏季干旱的响应关系,结果表明:1)蒸散发和环境因子呈现明显的季节变化动态,在整个生长季呈现单峰曲线,约88.5%的蒸散发量主要集中在生长季(4月-10月)。2)日最大蒸散发量为6.3 mm,年累积蒸散发量为471.5 mm,累积降水量远大于累积蒸散发量,蒸散发量和降水之间的差值为226.3 mm。3)夏季干旱通过诱导气孔闭合引起蒸散发出现一定程度的下降趋势,但对年蒸散发影响较小。4)空气温度、净辐射、土壤含水量和饱和水气压差均对粮草复合生态系统蒸散发季节变异存在一定的调控作用,但主要受净辐射和饱和水汽压差的调控。研究结果将为黄土高原粮草复合生态系统管理和气候变化下水分高效利用提供理论依据。

Evapotranspiration plays a critical role in the water cycles of ecosystems,directly or indirectly impacting soil moisture and processes including plant growth and carbon cycling.It is influenced by extreme climate.Understanding the dynamics and regulatory mechanisms of evapotranspiration in ecosystems under climate change scenarios is thus crucial for regional water resource management and ecological restoration.A typical grain-forage complex ecosystem in the Loess Plateau serves as the research object in this study,and seasonal variation in evapotranspiration within this grain-forage complex ecosystem and its response to summer drought have been analyzed using eddy covariance continuous monitoring.The results show that:1)evapotranspiration and environmental factors experience noticeable seasonal oscillations,following a unimodal curve throughout the growing season.Approximately 88.5%of total evapotranspiration occurs within the period spanning April to October;2)the daily maximum evapotranspiration is 6.3 mm,and the annual cumulative evapotranspiration amounts to 471.5 mm.Cumulative rainfall surpasses cumulative evapotranspiration,resulting in a difference of 226.3 mm between evapotranspiration and precipitation;3)summer drought causes a certain degree of decline in evapotranspiration by inducing stomatal closure,but has little effect on annual evapotranspiration;4)air temperature,net radiation,soil moisture,and saturation vapor pressure deficit are identified as factors contributing to the seasonal variability in evapotranspiration in this grain-forage combined ecological system,but the most prominent effectors are net radiation and saturated vapor pressure difference.These findings offer a theoretical basis for the management of grain-forage combined ecological systems and efficient water utilization in the Loess Plateau.