中国不同植被类型归一化植被指数对气候变化和人类活动的响应

不同植被类型对外界干扰和环境变化的敏感性不同。为厘清中国不同类型植被的动态变化特征及其对外界环境变化的响应,综合利用趋势分析、残差分析和情景模拟方法,在明确2000-2015年间我国不同植被类型归一化植被指数(NDVI)时空变化基础上,对气候变化和人类活动两大驱动要素在不同植被类型NDVI变化中的相对贡献进行了定量评估和归因。研究结果表明:(1)2000-2015年,我国植被NDVI整体呈增加趋势,且其空间占比高达84.1%。其中,森林植被的改善状况最佳,显著增加的面积占到了森林总面积的82.4%;而荒漠植被的改善状况相对较差,仅有22.3%的区域呈显著增加趋势。(2)人类活动在我国植被变化中占主导地位。植被改善区和植被退化区人类活动的相对贡献分别为76.4%和60.0%,且人类活动对植被的影响更多与管理方式而非土地利用类型转变有关。(3)不同类型植被对气候变化和人类活动的响应差异显著。对于植被改善区,除沼泽外,人类活动对各类型植被NDVI变化的贡献率均在70%以上,尤其是对农作物的贡献率最高,达到80.7%;对于植被退化区,人类活动影响较大的植被类型为沼泽和农作物,表明2000-2015年间我国沼泽受到了更强烈人类活动的负面影响。研究有助于增强对不同植被类型对全球变化响应机制的理解,并为促进生态建设和植被恢复工作的有效实施提供科学参考。

Vegetation dynamics and its response to climate change and human activities based on different vegetation types in China

Climate change and human activities are the main driving forces of vegetation dynamics. However, sensitivity to external disturbance and environment is different among different vegetation types. Knowledge of dynamics of different vegetation types in related to climatic changes and anthropogenic activities is thus critical for understanding the driving mechanism of vegetation changes and developing ecological protection strategies. During the past decades, China has experienced dramatic climate and land use/land cover changes, and the vegetation cover has changed significantly. However, most studies focused on the attribution of vegetation change in a single vegetation type. Vegetation dynamics and its response to climate change and human activities based on different vegetation types remains unknown in China. Therefore, it is necessary to enhance an understanding of contributions of climate change and human activities among different vegetation types in China. Based on the trend analysis, residual analysis and scenario simulation methods, this paper investigated the spatial and temporal changes of different vegetation types in China using the Normalized Difference Vegetation Index (NDVI) during 2000-2015, and distinguished the relative role of climatic change and human activities. Results indicated that: (1) vegetation NDVI showed an increasing trend in China during 2000-2015, with a proportion of 84.1%. Moreover, the increasing trend can be divided into two stages: the rapid rise stage during 2000-2005 (with a rate of 0.0074/a) and the slow rise stage during 2000-2015 (with a rate of 0.0024/a). Among various vegetation types, the forest vegetation showed the best improvement tendency with significantly increased area accounting for 82.4% of total forest area, while desert vegetation improved relatively poor, with only 22.3% of the area where vegetation increased significantly. (2) Vegetation changes in China were mainly affected by human activities. The relative roles of human activities in vegetation improvement areas and in vegetation degradation areas were 76.4% and 60.0%, respectively. Moreover, its impact was more related to management methods than the change of land use types. (3) The responses of different vegetation types to climate change and human activities varied greatly. In vegetation improvement areas, with the exception of marshes vegetation, the contributions of human activities to vegetation changes were more than 70%, especially to crops with 80.7%. In vegetation degradation areas, marshes and crops vegetation were most affected by human activities, indicating that marshes in China suffered the negative effects of more intensive human interference in 2000-2015. Therefore, regional governments should strive to improve ecological quality of various vegetation types, especially dominant vegetation, to promote the local ecological construction.