鄱阳湖流域不同土地覆被碳水利用效率时空变化及其与气候因子的相关性

鄱阳湖流域作为较突出的碳汇功能区，深入掌握不同土地覆被碳素利用率（CUE）和水分利用效率（WUE）的时空分异规律及其对气候因子的响应，对明确气候变化背景下该流域生态功能和碳水循环有重要意义。利用MODIS数据产品，结合流域土地利用和气象监测数据，辅以趋势分析和相关分析等方法研究了2000-2014年鄱阳湖流域不同土地利用类型CUE和WUE的时空变化特征，并探讨了其与降水、气温和日照时数的相关性。结果表明：1）鄱阳湖流域CUE和WUE多年平均值分别为0.458和0.682 gC/kgH₂O，不同土地利用类型的CUE大小依次为草地 > 水田 > 其他林地 > 旱地 > 疏林地 > 灌木林 > 有林地，WUE大小依次为有林地 > 灌木林 > 旱地 > 疏林地 > 水田 > 其他林地 > 草地；2）鄱阳湖流域CUE、WUE在研究时段内均呈微弱下降趋势，各土地利用类型CUE和WUE则表现出较大的年际波动，且年际变化趋势率具有高度的相似性，其中林地各类型下降趋势最大，其次是旱地和水田，草地最小；3）降水是影响鄱阳湖流域土地覆被碳水利用效率变化的关键因素，其他因子与CUE和WUE的相关性均不显著，不同覆被CUE和WUE对气温、降水和日照时数的响应程度存在较大差异。

Spatio-temporal variation of carbon and water use efficiency of different land cover in the Poyang Lake Basin and their correlations with climate factors

The Poyang Lake Basin is a prominent carbon sink functional area in China. Understanding the spatio-temporal differentiation of different land covers ecosystem carbon use efficiency (CUE) and water use efficiency (WUE) in the Poyang Lake Basin and their responses to meteorological factors is of great significance to clarify regional ecological functions and carbon-water cycle under the context of climate change. Based on the latest MODIS products, land cover data and meteorological observations during 2000-2014, the spatio-temporal variations of CUE and WUE of different land covers in the Poyang Lake Basin and their correlations with precipitation, temperature and sunshine duration were investigated by using the methods of trend analysis and correlation analysis. Results of this research show that: 1) the average annual CUE and WUE in the Poyang Lake Basin were 0.458 and 0.682 gC/kgH₂O, respectively. For different land cover types, the values of CUE descended in the order of grassland > paddy field > other woodland > dry land > sparse forest > shrub forest > forest land; whereas the values of WUE descended in the order of forest land > shrub forest > dry land > sparse forest > paddy field > other woodland > grassland. 2) During the study period, both CUE and WUE showed a slight decreasing trend. Both the CUE and WUE of different land covers in the Poyang Lake Basin showed large inter-annual fluctuations, while their linear change rate was highly consistent. The different types of forest showed the largest decreasing rate, followed by dry land, paddy field and grassland. 3) Generally, precipitation is the key meteorological factor affecting the change of CUE and WUE in the Poyang Lake Basin, while the other meteorological factors are not significantly correlated with CUE and WUE. Moreover, the responses of CUE and WUE to temperature, precipitation and sunshine duration varied significantly among different land covers.