2001—2018年中国⁃老挝交通走廊核心区植被稳定性对极端干旱的响应

Vegetation stability in response to extreme droughts from 2001 to 2018 in the core area of China⁃Laos transportation corridors

中国⁃老挝交通走廊核心区干旱事件的频繁发生威胁着该区域生态系统的稳定性。基于Palmer干旱指数(PDSI)和增强型植被指数(EVI)数据量化了中老交通走廊核心区不同植被类型的稳定性(年均EVI与其标准差之比)及其对干旱的抵抗力(干旱期间植被结构和功能保持其原始水平的能力)和恢复力(植被恢复到干旱前水平的速度)。结果表明:(1)2001—2018年间,中老交通走廊核心区共发生5次极端干旱事件,出现极端干旱的年份有2005年、2010年、2015年、2016年和2017年,以上年份极端干旱面积占总面积的比例分别为13.37%、47.46%、10.41%、12.00%和3.05%;(2)不同植被类型对极端干旱的响应不同,中老交通走廊核心区内常绿阔叶林的稳定性显著高于其他植被类型,和其他植被类型相比,常绿阔叶林虽然暴露在干旱环境中的时间更长,但其具有更高的稳定性,在维持中老交通走廊核心区的生态系统稳定性上发挥着重要作用;(3)常绿阔叶林和木本稀树草原对极端干旱的抵抗力和恢复力显著高于混交林、草地和农田,研究区内各植被类型对极端干旱的抵抗力与温度和降水呈显著正相关关系。

The core area of China⁃Laos transportation corridors have been frequently affected by drought events,which threatened the stability of terrestrial ecosystem functioning.Based on the Palmer Drought Severity Index(PDSI)data and enhanced vegetation index(EVI)products,we quantified the temporal stability(ratio of mean annual EVI to its SD),resistance(ability to maintain its original levels during droughts),and resilience(rate of EVI recovering to pre⁃drought levels)in the core area of China⁃Laos transportation corridors.The results showed that:(1)there were 5 extreme drought events in the core area of China⁃Laos transportation corridors from 2001 to 2018,appearing in 2005,2010,2015,2016 and 2017.The area of extreme drought accounted for 13.37%,47.46%,10.41%,12.00%and 3.05%,respectively.(2)Different vegetation types had different responses to droughts.The temporal stability of evergreen broadleaf forests was significantly higher than that of other vegetation types.Evergreen broadleaf forests had higher stability than other vegetation types despite the greater drought exposure,which played an important role in maintaining the ecosystem stability of the corridor core area.(3)The evergreen broadleaf forests and savannas illustrated significantly higher resistance and resilience of EVI than other vegetation types.The resistance of various vegetation types to extreme drought in the study area was positively associated with temperature and precipitation.