植被恢复与气候变化影响下的鄱阳湖流域蒸散时空特征

Spatiotemporal pattern of evapotranspiration in Poyang Lake Basin under the joint influences of vegetation restoration and climate change

蒸散是地球表层物质循环与能量交换过程的重要组成部分，了解其时空特征和影响因素具有重要的科学意义。以鄱阳湖流域为研究区，基于 Wa SSI-C 生态水文模型，利用气象数据、叶面积指数数据和土壤数据等估算1983-2011年鄱阳湖流域蒸散，分析其时空特征，并通过情景模拟定量分析植被恢复和气候变化对蒸散的影响。研究表明：鄱阳湖流域蒸散多年均值变化范围为741~914 mm/a，植被和降水量分布是造成流域蒸散空间差异的主要原因；近三十年来鄱阳湖流域蒸散呈阶段性增长趋势，增长率为 1.495 mm/a；植被、气温和降水对鄱阳湖流域蒸散的单独影响均为正向，但气温和降水的联合效应会导致蒸散下降；鄱阳湖流域蒸散变化的主导因素具有空间差异性，从整体上看，植被恢复是驱动蒸散呈增加趋势的主要原因，而气候变化是导致蒸散年际波动的主要原因。

Evapotranspiration （ET） plays a critical role in the cycles of matter and energy on the land surface. Understanding its spatiotemporal pattern and control factors is of great scientific importance. Intensive climate change in the past decades has been modifying the hydrological and heat fluxes profoundly. At the same time, the vegetation change will further complicates the dynamics of ET. Located at the middle reaches and southern bank of the Yangtze River, the Poyang Lake Basin experienced remarkable vegetation restoration and climate change during the past three decades, thus providing a valuable opportunity for us to evaluate the joint and respective effects from them. The main objective of the study is to estimate spatiotemporal patterns of ET in the Poyang Lake Basin and quantitatively evaluates the impacts from different environmental factors. We producted a long-term （1983-2011） ET record and investigated multidecadal changes in evapotranspiration and underlying causes in the Poyang Lake Basin with the application of WaSSI-C ecosystem model, which was driven by meteorological data, leaf area index data and basic soil parameter data. The modeled ET results were validated at different spatial scales and exhibited overall reasonable accuracies. According to the modeling results, substantial variations were detected in the spatial patterns of multi-year mean ET value across the Poyang Lake Basin （741-914 mm/a）, which can be largely explained by the distributions of vegetation and precipitation. Over the past 29-year study period, ET record in the Poyang Lake Basin showed an upward global trend of 1.495 mm/a with large inter-annual fluctuatation. Based on the scenario design, our factor analysis further indicated that all changes of vegetation, precipitation and air temperature will lead to the positive ET reponses, while the joint effect of precipitation and air temperature will lead to a negative ET response. The overall upward trend of ET was largely derived from the contribution of vegetation restoration. Climate change, on the other hand, primarily explained its inter-annual variation.