1981-2010年中国散射光合有效辐射的估算及时空特征分析

Assessment of the spatiotemporal variations of diffusephotosynthetic active radiation in China from 1981 to 2010

光合有效辐射（Photosyntheticallyactiveradiation，eAR）是植物光合作用的主要能量来源，其散射组分能够增强植被冠层光能利用率，从而增加碳吸收。因此，散射PAR是生态系统生产力模型的重要驱动因子。本文尝试估算我国1981-2010年的散射PAR，通过空间化得到近30年月尺度10km分辨率的散射PAR空间数据集，并分析了其空间分布特征和时间变化趋势。结果表明：（1）1981-2010年散射PAR多年平均值的空间分布具有明显的空间异质性，总体上东北部较低，南部和西部较高。全国范围内的多年平均值在6．66~15．27molm^-2d^-1之间，且夏季散射PAR最大，冬季最小。（2）1981．2010年全国所有像素散射PAR年平均值表现出明显的上升趋势，上升幅度为0．03molm^-2d^-1／10a；但前10年下降趋势明显，且1982、1983、1991和1992年存在明显异常。春季的散射PAR呈现微弱的下降趋势，其他季节均呈上升趋势。（3）1981．2010年散射PAR时间变化率的空间分布具有明显的季节变化和区域差异，我国大体呈现南部区域上升，北部区域下降。

Photosynthetically active radiation is the energy source of plant photosynthesis, and the diffuse component can enhance canopy light use efficiency, thereby increasing the carbon uptake. Therefore, diffuse PAR is an important driving factor of ecosystem productivity models. In this study, we estimated the diffuse PAR of over 700 meteorological sites in China from 1981 to 2010 using an empirical model based on observational data from Chinese Ecosystem Research Network （CERN） and China Meteorological Administration. Then we derived the spatial data set of 10 km monthly diffuse PAR using ANUSPLIN software, and analyzed the spatiotemporal variation of diffuse PAR through GIS and trend analysis. The results showed that： （1） the spatial patterns of annual average diffuse PAR during 1981-2010 are heterogeneous across China, lower in the northeast and higher in the west and south. The nationwide average value for the 30 years ranges from 6.66 molm^-2d^-1to 15.27 molm^-2d^-1, and the value in summer is the biggest while the value in winter is the smallest. （2） There is an evident increasing trend of annual diffuse PAR during recent 30 years, with increasing amplitude at 0.03 molm^-2d^-1/10a. But a significant declining trend is observed in the first 10 years, and obvious anomalies can be seen in 1982, 1983, 1991 and 1992. And there is a downward trend in spring and an upward one in all other seasons. （3） The spatial distribution of temporal variation rates of diffuse PAR is inhomogeneous across the whole country, generally decreasing in the north and increasing in the south.