气候变化下中国不同植被区总初级生产力对干旱的响应

Response of gross primary production to drought under climate change in different vegetation regions of China

干旱变化具有明显的空间分异,不同植被类型对干旱的响应亦有差别。开展气候变化下不同植被覆盖类型对干旱响应的差异分析,厘清温升干旱化进程对植被的影响,对了解植被发展动态及预测未来格局有着非常重要的意义。基于1982—2017年的总初级生产力(GPP)数据和同时期东安格利亚大学气候研究中心(CRU)时间序列(TS)气候数据,分析了中国8个植被区GPP和干旱的变化趋势,通过对比标准化降水指数(SPI)和标准化降水蒸散指数(SPEI)的趋势差异识别了典型的温升干旱化区域,在此基础上研究气温上升如何影响GPP对干旱的响应,进一步讨论了不同植被类型对干旱的敏感性差异。结果表明:(1) 36年来8个植被区除青藏高原高寒植被区呈湿润化,其他植被区均呈现变干趋势;(2)气温上升大面积加剧了温带荒漠区和温带草原区的变干趋势;(3)亚热带常绿阔叶林区和热带季风雨林、雨林区的GPP受温度和干旱影响相当,青藏高原高寒植被区和针叶、落叶林混交林区的GPP受温度主导,其他植被区GPP均受干旱主导。

Variations of drought have obviously spatial differentiation, and different vegetation types have different responses to drought. However, few studies have been conducted to distinguish the contribution of temperature increase to the variations of drought and to investigate the differences in the responses of different vegetation types to warming aridification on a large scale. Analyzing differences in the response of different vegetation cover types to drought under climate change and clarifying the impact of warming aridification on vegetation in China are of great importance for understanding the development dynamics of vegetation and predicting future patterns. In this study, based on climatic data from the University of East Anglia Climatic Research Unit(CRU) Time-series(TS) version 4.04 dataset, the standardized precipitation index(SPI) and standardized precipitation evapotranspiration index(SPEI) were calculated in 1982—2017. Using Theil-Sen median trend analysis and the Mann-Kendall test, we analyzed trends in gross primary production(GPP) and drought in the eight vegetation regions of China. By comparing the trend differences between SPI and SPEI, typical warming aridification areas were identified under three scenarios([SPI not significantly drier+SPEI significantly drier], [SPI wetter+SPEI not significantly drier], and [SPI wetter+SPEI significantly drier]). Finally, after detrending GPP and temperature, the correlation analysis and multiple regression were used to investigate how temperature increase affected the response of GPP to drought and further discuss the differences in sensitivity of different vegetation regions to drought. The results showed that all eight vegetation regions showed a drying trend over past 36 years, except for Qinghai-Tibet plateau high cold vegetation region, which was getting wet. The GPP of each vegetation region mainly increased, among which the Qinghai-Tibet plateau high cold vegetation region showed the most significant increase in GPP, which might be related to the warming and wetting trend in this region. The temperature increase had the strongest exacerbating effect on drying in temperate desert region and temperate steppe region, and the weakest exacerbating effect on drying in temperate needleleaf and broadleaf forest region and cold temperate needleleaf forest region, while it significantly increased the sensitivity of GPP to drought in the latter. There was variability in the response of GPP to temperature and drought conditions in different vegetation regions: the GPP of the subtropical evergreen broad-leaved forest region and the tropical monsoon forest and rain forest region was comparably affected by both temperature and drought, the GPP of the Qinghai-Tibet plateau high cold vegetation region and temperate needleleaf and broadleaf forest region was dominantly affected by temperature, and the GPP in all other vegetation regions was mainly affected by drought.