黄土高原地区气象干旱动态格局演变及其对植被的影响

Impacts of meteorological drought on vegetation and their dynamic pattern evolutions on the Loess Plateau

本文以黄土高原为研究区域,通过识别气象干旱的三维连续时空体,剖析了1982—2018年夏秋季节气象干旱(SPEI)事件发生发展过程与区域植被覆盖(NDVI)之间的响应关系。结果表明:①基于空间聚类识别的黄土高原三维气象干旱事件与历史真实干旱事件的发展演变过程基本吻合;②从时间和空间维度综合来看,黄土高原气象干旱发生区域NDVI往往会比同区域非干旱时期减少,且NDVI减少程度与气象干旱强度显著相关(R2=0.4389,P<0.05);③从黄土高原不同土地利用类型(耕地、草地和林地)对干旱事件响应关系来看,草地最易受干旱胁迫且对干旱强度的变化最敏感,抗旱性最差;而耕地在干旱强度较大的干旱事件中更易受到影响。本研究对科学合理地理解区域干旱的动态格局演变及阐明其对植被生态系统的影响机制均具有重要参考意义。

The study of impacts of drought on vegetation is one of the important ways to assess the impact of extreme climate on ecosystems.The dynamic pattern evolutions of drought has spatial and temporal character-istics.It is of great significance to analyze the impact of dynamic development of drought event on vegetation ecosystem in order to deeply understand the mechanism of drought and vegetation interaction.Based on a 3-di-mensional drought clustering algorithm,we proposed a new method for quantitatively analyzing the vegetation response mechanism to droughts by accurately describing temporal continuity and dynamic extensibility of drought events.We investigated the temporal and spatial evolution characteristics of meteorological drought events and vegetation response to meteorological drought events on the Loess Plateau from 1982 to 2018 by identifying the 3-dimensional continuum of meteorological drought events.Results showed that:1)The 3D drought events identified by the clustering algorithm on the Loess Plateau were convincible and reliable by the comparation with documented historical drought events.2)We found that the NDVI value of drought affected area during drought period tended to be lower than that during pre-drought period by comparing the NDVI value in two periods and a good correlation was found between the NDVI reduction and meteorological drought events severity(R2=0.4389,P<0.05).3)Further study showed that the NDVI cumulative reductions re-sponse quickly to SPEI cumulative reductions on the Loess Plateau.Grassland was the most sensitive and vul-nerable to drought events which had the worst drought resistance by comparing the response characteristics of different land use types(cropland,grassland and forest)to drought events;However,cropland had suffered worst during severe drought events.Our findings provide crucial insights into scientific and reasonable under-standing of the dynamic pattern evolution of 3D drought events and its influence mechanism on vegetation eco-system.