云南人工林和天然林对短期与持续干旱响应的差异性

Different responses of planted and natural forests to short-term and prolonged droughts in Yunnan

全球气候变化导致干旱发生的频率,持续时间以及强度不断增加,严重影响森林的正常生长.受人类活动影响,人工林的面积逐渐增大,其对不同强度干旱胁迫的响应是否与天然林存在显著差异,目前仍存在争议.本文以云南省为研究区域,分析了不同时间尺度的气象干旱指数(SPEI)与反映植被生长状态的遥感监测植被指数(MODIS EVI)之间的关系,获得了反映该地区最佳时间尺度SPEI和对水分最敏感月份的EVI指标,进而基于省级尺度和基于气象站点的泰森多边形2个尺度上比较了人工林和天然林的生长状态对短期干旱(2001—2008年)与持续干旱(2009—2014年)的响应差异.结果表明:1)无论是人工林还是天然林,持续干旱对其的生长状态的影响均大于短期干旱;2)天然林的生长状态受持续干旱的影响程度大于人工林,且生长状态比人工林差.气候变化将导致更多极端的持续干旱事件发生,在未来气候变化进程中应多关注极端干旱对天然林的影响以及天然林的可恢复性问题.

Global warming leads to more frequent, durative and intensive drought events, with severe impact on forests. The area of plantation forests has gradually increased due to human efforts, but whether there are any significant differences in response to drought of plantation and natural forests is still disputed. In this study, we choose Yunnan province as the research region. Multiple-time-scale meteorological drought index （SPEI） was used to reflect strength of drought, MODIS remote sensing monitoring information of enhanced vegetation index （EVI） was used to characterize forest growth state, best time-scale of SPEI and month of EVI sensitive to water were acquired by analyzing relationship between SPEI and EVI, then difference in growth state response of planted and natural forests to short-term （2001-2008） and prolonged drought （2009- 2014） was compared on provincial and Thiessen polygon scale. It was found that whether it was planted forests or natural forests, the impact of prolonged drought was greater than short-term drought. Natural forest growth state was influenced more by prolonged drought than planted forests, growth state of natural forests was worse than planted forests. Extreme droughts are likely to increase in the future, therefore more attention should be paid to their impact on natural forests and recoverability of natural forests.