近40年中国干旱特征及其对植被变化的影响

全球变暖影响下,中国干旱事件发生愈加频繁。过去半个世纪里,中国半干旱和半湿润地区的分界线总体南移,干旱面积呈增加趋势,因此了解中国干旱变化趋势对区域生态环境保护具有重要意义。基于GLASS数据产品、ERA5-Land数据,采用游程理论和多元线性回归等方法,探究1982—2018年间多尺度干旱事件基本特征(干旱持续时间、干旱严重度、干旱强度等),并分析植被生产力变化趋势,揭示干旱对植被变化的累积影响。结果表明：(1)新疆、青藏高原以及东南地区干旱较为严峻,而华中、华东大部分区域处于轻旱或无旱状态;(2)1982—2018年间,中国植被生产力整体呈改善态势,显著改善区集中在中国中部,而退化区集中在东南部、内蒙古和西藏南部;(3)中国大部分区域干旱与植被呈正相关,且干旱对植被多为累积影响,在干旱区和半干旱区尤为明显;(4)随着植被覆盖度的增加,植被与近短期尺度干旱的相关性也逐渐增加,由干旱区到湿润区,近短尺度干旱对植被变化的影响逐步增大。其中,SPEI-6(标准化降水蒸散发指数—中期尺度)对植被轻微变化累积影响最显著,而SPEI-12(标准化降水蒸散发指数—长期尺度)对植被显著变化累积影响更...

Characteristics of drought in China and its effect on vegetation change in recent 40 years

Under the influence of global warming, drought events are becoming more frequent in China. Moreover, the dividing line between China''s semi-arid and semi-humid areas has generally moved southward in the past half-century, and the arid area had an increasing trend. Thus, understanding the trend of drought change in China is of great significance for protection of the regionally ecological environment. Based on the GLASS dataset and ERA5-Land data, the characteristics of drought events (drought duration, drought severity, drought intensity, etc.) were explored from 1982 to 2018 at different timescales (SPEI-1, SPEI-3, SPEI-6 and SPEI-12) using run theory and multiple linear regression model. Then, the changing trend of vegetation productivity was investigated in the study. Further study revealed the cumulative effect of drought on vegetation change. The results showed that severe drought was observed in Xinjiang, the Qinghai-Tibet Plateau and southeast China based on drought indicators at multiple timescales, while mild drought or no drought was identified in most of central and eastern China. Drought events with high severity and long duration have occurred in Xinjiang; The drought intensity in the Qinghai-Tibet Plateau is relatively high; In southeast China, there are fewer drought events, but their severity and intensity are higher. The overall vegetation productivity of China improved from 1982 to 2018. The areas with significant improvement were mainly distributed in the central China, while the areas with significant degradation were concentrated in the southeastern China, the Inner Mongolia and southern Tibet. A positive correlation between vegetation and drought was investigated in most areas of China, especially in the arid and semi-arid zones. With the increase in vegetation coverage, the correlation between vegetation and short-term drought increased. The correlation between vegetation and drought at the short-term timescale increased gradually from the arid area to the humid area. Drought at the medium timescale of SPEI-6 had the significantly cumulative impact on vegetation with slight changes, whereas drought at the long-term timescale of SPEI-12 had the strongest cumulative impact on vegetation with significant changes. Most of the impacts of drought on vegetation in China are cumulative. For example, Inner Mongolia, located in the northeastern part of the semi-arid region, has a close relationship between vegetation degradation and medium-term drought. Vegetation in the Qinghai-Tibet Plateau is sensitive to long-term drought, which is not only affected by precipitation, but also by ice and snow melt water in the early stage and frozen soil freezing and thawing. This study will help to deeply understand the cumulative impact of drought on vegetation and improve the effectiveness of vegetation degradation prevention and control measures. This paper can provide the scientific basis for achieving the land degradation neutrality initiative.