2000-2013年中国植被碳利用效率(CUE)时空变化及其与气象因素的关系

植被碳利用效率（CUE）是评估陆地碳循环的重要指标，探讨其动态特征对气候变化的响应对于陆地生态系统碳循环研究具有重要的指示意义。基于MOD17数据计算中国植被CUE，辅以地统计学理论，利用趋势分析、变异系数及相关性分析等方法，研究了2000—2013年中国植被CUE的时空变化特征，并结合气象要素数据剖析植被CUE对气候变化的响应。结果表明:全国植被年CUE在研究年限内总体上表现为轻微的增长趋势，具体表现为在2000—2007年以0.000 6的变化率呈现波动下降的趋势，而2007—2013年植被CUE呈现显著上升的变化趋势，该变化特征可归因于2007年气温及降水格局的改变；植被CUE空间分布具有明显的空间异质性，大体呈现西部高东部低的状态。CUE增加较明显的区域主要分布在内蒙古呼伦贝尔地区，青藏高原大部分地区，东部沿海地区以及台湾岛。而CUE呈减少趋势的区域分布范围较广，其中减少趋势较为明显的地区主要包括东北平原及华北华中的大部分地区，另江南地区及新疆部分地区也有零星分布。草地及森林区域植被CUE波动变化较小，表明该部分地区生态系统处于良性循环。不同植被类型的CUE均值表现为:草地（0.21） > 农田（0.14） > 森林（0.09） > 灌丛（0.06）。全国大多数地区植被CUE与降水呈正相关，而与气温则呈负相关，而这种相关性会随着区域气候格局及植被类型的变化而变化。总体上，全国植被CUE的增加主要归因于降水量的增加，而气温的升高则造成植被CUE的降低。

Spatiotemporal Dynamic of Vegetation Carbon Use Efficiency and Its Relationship with Climate Factors in China During the Period 2000-2013

Carbon use efficiency (CUE) is an important indicator to evaluate the carbon cycle of terrestrial ecosystem. Assessing the responses of CUE to climate change is of great significance to the study of terrestrial ecosystem carbon cycle. In this study, the vegetation CUE was calculated based on the MOD17 dataset, and the temporal and spatial dynamics of vegetation CUE in response to climate change in China during 2000-2013 were also analyzed. The results showed that the vegetation CUE presented a slightly increasing trend during the study period overall. Specifically, the vegetation CUE showed a decreasing trend during the period 2000-2007 with the change rate of 0.000 6, but presented a significant increasing trend from 2007 to 2013, which could be attributable to the change of climate pattern in 2007. The spatial distribution of vegetation CUE had obvious spatial heterogeneity. The vegetation CUE was generally high in the west and low in the east. The regions where vegetation CUE showed an obviously increasing trend were mainly located in the Hulun Buir region of Inner Mongolia, most of parts of the Qinghai Tibet Plateau, the eastern coastal area and the Taiwan Island. However, the regions where vegetation CUE showed an obviously decreasing trend mainly distributed in the Northeast Plain and most areas of central China, while the other areas in the south of the Yangtze River and some parts of Xinjiang also had sporadic distribution. The fluctuation of vegetation CUE in grassland and forest area was relatively small, which indicated that the ecosystem in these areas was in a virtuous circle. The mean CUE values of different vegetation types follow an order of:grassland (0.21) > farmland (0.14) > forest (0.09) > shrub (0.06). The vegetation CUE in most areas was positively correlated with precipitation, but was negatively correlated with the temperature, and this correlation variation with the change of regional climate patterns and vegetation types. In general, the increase of CUE in China was mainly attributed to the increase of precipitation, while the increase of temperature induced the decrease of vegetation CUE.