长江经济带水分利用效率变化及与温度和降水的关系

通过水分利用效率(Water Use Efficiency, WUE)深入理解生态系统水碳循环的相互关系,可以较好地评估生态系统对气候变化的响应。长江经济带自然资源丰富、生态系统格局复杂,是中国重要的经济发展区,同时也是响应气候变化的重要区域。基于生态系统过程模型CEVSA2(Carbon Exchange between Vegetation, Soil and Atmosphere),估算了1981—2010年长江经济带WUE的时空动态变化,并分析其与温度和降水之间的关系。结果表明:(1)长江经济带1981—2010年WUE均值为1.14 g C mm~(-1 )m~(-2),WUE的空间分布与降水量呈显著正相关关系(r=0.571,P0.01),而与温度呈显著负相关(r=-0.740,P0.01);(2)长江经济带1981—2010年WUE变动区间为1.04—1.19 g C mm~(-1) m~(-2),WUE总体呈减少趋势,平均每年降低0.0030 g C mm~(-1) m~(-2);(3)研究区域内四种主要植被类型常绿针叶林、常绿阔叶林、草地和常绿灌丛的水分利用效率均呈下降趋势,下降速率分别为-3.29×10~(-3)、-2.99×10~(-3)、-3.30×10~(-3)、-2.65×10~(-3) g C mm~(-1) m~(-2) a~(-1)。研究区域内各植被类型的WUE与降水量的相关性不如温度显著,温度对WUE的影响要大于降水对WUE的影响。今后在提高时空分辨率的基础上,更精确地模拟和预测未来温度、降水等气候因子变化下长江经济带WUE变化趋势及分析该地区水碳耦合关系。

Changes of water use efficiency in the Yangtze River Economic Zone and its relationship with temperature and precipitation

Through water use efficiency (WUE), we can have a deep understanding of the relationship between water and carbon cycles in ecosystems and better assess the responses of ecosystems to climate change. The Yangtze River Economic Zone, with rich natural resources and complex ecosystem patterns, is an important area for economic development and responding to climate change in China. In order to study the changes of WUE and its relationship with temperature and precipitation, an ecosystem process model, Carbon Exchange between Vegetation, Soil and Atmosphere (CEVSA2), was used to estimate the temporal and spatial variation of WUE in the Yangtze River Economic Zone from 1981 to 2010. The evapotranspiration (ET) and net primary productivity (NPP) were obtained by CEVSA2 and the correlation coefficients between annual mean WUE and annual precipitation and mean temperature were calculated. SPSS19, ArcGIS10.2 and Envi 5.3 were used in the analysis. The results showed that: (1) the mean WUE of the Yangtze River Economic Zone from 1981 to 2010 was 1.14 g C mm^-1 m^-2. In spatial distribution, WUE was significantly positive correlated with annual precipitation (r=0.571, P < 0.01), while significantly negative correlated with annual temperature (r=-0.740, P < 0.01). (2) The WUE variation range of the Yangtze River Economic Zone was 1.04-1.19 g C mm^-1 m^-2 during 1981-2010, and the WUE showed a decreasing trend by 0.0030 g C mm^-1 m^-2 a^-1. (3) The WUE of four main vegetation types, including evergreen needle-leaved tree cover, evergreen broadleaved tree cover, herbaceous cover, and evergreen shrub cover, showed a downward trend with rate -3.29×10^-3, -2.99×10^-3, -3.30×10^-3 and -2.65×10^-3 g C mm^-1 m^-2 a^-1, respectively. In 81.58% of the study area (P < 0.05), the WUE was negatively correlated with annual mean temperature between 1981 and 2010, while positively correlated with annual precipitation in 85.92% of the study area (P < 0.05) during the same period. The correlation between WUE and precipitation of all vegetation types was not as significant as that between WUE and temperature. Therefore, the impact of temperature on WUE is greater than precipitation in this study area. In the future, higher spatial resolution and longer time series observation data are needed to simulate the water and carbon cycle and analyze its coupling relationship.