2003—2017年植被变化对全球陆面蒸散发的影响

Impacts of vegetation changes on global evapotranspiration in the period 2003-2017

蒸散发是陆面水循环的关键环节和过程,是研究水循环对人类活动和气候变化响应的关键要素。过去十几年,全球下垫面的植被变化剧烈,但如何影响全球陆面蒸散发仍未得到清晰的揭示。本文采用500 m分辨率MODIS数据驱动PML-V2模型,定量解析了2003—2017年植被变化对全球陆面蒸散发的影响。结果显示:在全球尺度上,植被变绿使得全球蒸散发呈现显著的增加趋势,使陆地水循环加快;区域尺度上,植被变化对蒸散发的影响则存在明显的地带性和非地带性特征,如在北美洲中北部、欧洲、中国东部、非洲南部和澳大利亚东北部等地区,蒸散发总量的增加主要是由植被蒸腾增加而引起的。分析不同植被功能类型区的贡献显示,下垫面变化对灌木和耕地影响尤为明显,并在2012年以后呈现增强趋势;这2个植被类型区的全球年总蒸散发累积增加量为0.41×10^(3)km^(3)a^(-1),约为黄河流域多年平均径流量的8倍。该研究结果有助于进一步加强关于下垫面变化对陆地水循环的影响及其可能带来的局部气候变化的认识。

Evapotranspiration is a key variable and key process in global water cycle, and it is crucial for understanding how anthropogenic and climate changes have impacts on terrestrial water cycle. In the last decade, global vegetation changes are dramatic, reflected by land use and land cover changes and increase in leaf area index. It remains unclear how these changes influence terrestrial evapotranspiration processes. This study uses a coupled evapotranspiration and gross primary product model(PML-V2) that is run at 500 m and 8-day resolutions across the globe to investigate the impacts of vegetation changes on spatial pattern and dynamics of evapotranspiration in the period of 2003-2017. We found that evapotranspiration across the globe has increased noticeably because of vegetation changes, which is characterized by clear regional and non-regional patterns. Transpiration has strongly increased in the central and northern parts of North America, Europe, eastern China, southern Africa, and eastern and northern Australia. Under different land cover types, shrubs and cropland have been influenced strongly, and their impact is stronger in the post-2012 period than that in the pre-2012 period.The recent total increase from these two land cover types amounts to about 0.41 ×10^(3) km^(3) a^(-1),which is about 8 times of natural annual runoff from the Yellow River Basin. The results from this study can help improve the understanding of how vegetation changes caused by recent land use and land cover changes influence terrestrial water cycle and the potential local and regional climate change.