鄱阳湖流域蒸散发对植被恢复的动态响应过程研究

Evapotranspiration plays a key role in basin hydrological cycle, which is closely related to vegetation coverage. Variabilities in vegetation coverage can cause inter- and intra-annual changes of evapotranspiration through altering canopy conductive, solar radiation allocation, precipitation interception, and so on. Hydrological response to vegetation restoration is being one of the hot scientific issues on ecohydrology, but there is a lack of awareness of response mechanisms of evapotranspiration to variability in vegetation coverage during a process of vegetation restoration. Taking the Poyang Lake basin as the study area, this program will produce a long time serial dataset of ET and vegetation coverage based on remote sensing data and hydrological observations. Based on this dataset, we will detect the inter- and intra-annual variabilities of ET in response to the vegetation coverage change during the past 30 years. Then, the variation and difference in the evapotranspiration sensitivities with the vegetation restoration process will be investigated. Moreover, we will quantitatively investigate the relative contribution of the vegetation coverage change to the evapotranspiration responses and its effective thresholds. This program additionally aims to identify the effect of the evapotranspiration response to the vegetation restoration on water balance regimes in the basin. Our study is able to deepen the understanding of biological regulation of hydrological cycle in the basin scale. The outcomes of this program are expected to provide the theoretical and technological support for better detections of regional hydrological dynamic, as well as the scientific basis for ecological restoration and utilization.

蒸散发是流域水循环的重要组成部分，与植被密切相关。植被覆盖度变化通过改变冠层导度、辐射能量分配、降水截留等方面影响蒸散发的年际与年内特征。植被恢复的水文响应是生态水文学研究的关键科学问题之一，然而，关于植被恢复过程中蒸散发对植被覆盖度变化的响应过程与机制仍缺乏认识。针对当前不足，拟以鄱阳湖流域为研究区，利用遥感、水文观测等多源数据，构建长时序蒸散发及植被覆盖度数据集，厘清近30年蒸散发对植被覆盖度变化的年际与年内响应，明晰植被恢复过程中蒸散发响应的动态特征和敏感性差异，量化气候变化胁迫下植被覆盖度变化在蒸散发响应中的相对贡献及其效应阈值，阐明流域植被恢复过程的蒸散发响应对水量平衡状态的影响。项目实现有助于加深对流域水循环生物调控作用的认识，提高水文动态监测与分析的能力，同时为流域生态修复与利用提供科学依据。

蒸散发（ET）是流域水循环的重要组成部分，与植被密切相关。本研究以鄱阳湖流域为研究区，构建长时序蒸散发及植被覆盖度数据集，分析近30年流域ET对植被恢复的年际与年内响应。主要研究结论如下：（1）遥感植被覆盖度数据能够较好的表现鄱阳湖流域植被恢复过程，结果显示人类活动造成的植被覆盖度增加主要集中在人类活动密集的中下游区域。（2）在鄱阳湖流域植被恢复的不同阶段，植被覆盖变化对ET年均值的影响有所差异：在植被覆盖度较低的早期阶段（约41%），植被覆盖度变化对ET整体为负向影响；随着植被恢复的发展，植被的快速恢复（0.23%/年）造成了这一影响由负变正；在植被恢复后期覆盖度较高的时段（约55%），覆盖度变化对ET保持为正向影响。（3）1983-2014年间，鄱阳湖流域ET年内变化（即年内ET标准差）呈先下降后上升的变化趋势，且在1999年前后发生转折。ET年内变化主要与气候变量和植被覆盖有关。总体而言，蒸散发年内变化的主控因子为太阳辐射的年内变化（代表能量限制）和气温的年内变化（代表水分限制），其主控面积分别为77.82%和35.14%。同时，植被覆盖度的快速恢复导致了蒸散发年内变化的下降，其主控面积为35%。以上结论将有助于深入理解植被恢复过程的水文响应机制，提高流域水资源变化的预测能力，同时也为流域生态修复与利用提供科学依据。