水热条件分别控制了中国温带草地NDVI的年际变化和增长趋势

Abstract

温带草地区是我国植被对气候变化响应的敏感区和陆地生态系统的生态脆弱区, 是组成草地资源的重要部分。由于全球变暖, 气候变化带来的极端气候影响越来越大, 探究我国温带草地植被覆盖时空变化规律和水热条件变化对其生长的影响, 对区域生态的环境保护, 实现畜牧业的可持续发展和更加合理有效地利用草地资源具有重要的现实意义。基于1982—2015年长时间序列的气象(降水、温度、太阳辐射)数据和GIMMS NDVI 3g数据, 采用去趋势分析法和相关性分析法, 探究近34年中国温带地区生长季草地归一化植被指数(Normalized difference vegetation index, NDVI)和气候因子变化格局, 以及水热条件对NDVI的同步影响和滞后影响。研究结果表明：(1)1982—2015年中国温带草地生长季平均温度和月平均太阳辐射呈增长趋势, 降水量为下降趋势, 温带草地气候逐渐呈现“暖干化”；(2)1982—2015年中国温带草地生长季NDVI的年际变化由降水因子主导, 特别是在1999年之后, 降水的对于中国温带草地生长季NDVI年际变化的影响更为显著; (3)1982—2015年中国温带草地生长季NDVI为增长趋势, 生长季热条件(温度和太阳辐射)的显著上升控制着NDVI的增长趋势; (4)1982—2015年中国温带草地生长季NDVI对水热因子在年际变化上存在明显的滞后响应, 生长季前期NDVI对温度滞后响应最明显, 生长季中后期降水则成为植被生长滞后影响的主要控制因子。;The temperate grassland is the sensitive to climate change and is the ecologically fragile area of the terrestrial ecosystem in China, and it is an important part of the grassland resources. Due to global warming, the extreme climate impact brought by climate change is getting bigger, so exploring the temporal and spatial changes of vegetation coverage in the temperate grasslands in China and the effects of changes in water and heat conditions on vegetation growth are of greatly practical significance to the environmental protection of regional ecology, the sustainable development of animal husbandry, and more rational and effective use of grassland resources. Based on the long-term meteorological data (precipitation, temperature and radiation) and GIMMS NDVI 3g data from 1982—2015, this study used trend analysis and correlation analysis to explore the changes of grassland NDVI (Normalized difference vegetation index) in the growing season in the temperate regions of China, and the pattern of climate change, as well as the simultaneous and lagging effects of hydrothermal conditions on the NDVI. The results showed that: (1) From 1982 to 2015, the average temperature and total solar radiation in China's temperate grassland growing season showed an increasing trend, the total amount of precipitation was a downward trend, and the temperate grassland climate gradually became warm and dry. (2) From 1982 to 2015, the inter-annual variation of NDVI in the growing season of temperate grassland in China was dominated by precipitation factors. Especially after 1999, the influence of precipitation on the inter-annual variation of NDVI in the growing season of temperate grassland in China was more significant. (3) From 1982 to 2015, the NDVI of China's temperate grassland growing season was with an increasing trend, and it was positively correlated with water and heat factors. The significant increase in thermal conditions (temperature and solar radiation) during the growing season controlled the growth trend of the NDVI. (4) From 1982 to 2015, the NDVI of China's temperate grassland growing season had an obvious lagging response to the inter-annual variation of water and heat factor. The NDVI responded most obviously to the temperature lag in the early stage of the growing season, and precipitation became the main controlling factor for the lagging influence on vegetation growth in the middle and late growing seasons.