The Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.
University of the Chinese Academy of Sciences, Beijing, China.
Glob Chang Biol. 2019 Jun;25(6):2174-2188. doi: 10.1111/gcb.14627. Epub 2019 Apr 10.
Climate change has substantial influences on autumn leaf senescence, that is, the end of the growing season (EOS). Relative to the impacts of temperature and precipitation on EOS, the influence of drought is not well understood, especially considering that there are apparent cumulative and lagged effects of drought on plant growth. Here, we investigated the cumulative and lagged effects of drought (in terms of the Standardized Precipitation-Evapotranspiration Index, SPEI) on EOS derived from the normalized difference vegetation index (NDVI3g) data over the Northern Hemisphere extra-tropical ecosystems (>30°N) during 1982-2015. The cumulative effect was determined by the number of antecedent months at which SPEI showed the maximum correlation with EOS (i.e., R ) while the lag effect was determined by a month during which the maximum correlation between 1-month SPEI and EOS occurred (i.e., R ). We found cumulative effect of drought on EOS for 27.2% and lagged effect for 46.2% of the vegetated land area. For the dominant time scales where the R and R occurred, we observed 1-4 accumulated months for the cumulative effect and 2-6 lagged months for the lagged effect. At the biome level, drought had stronger impacts on EOS in grasslands, savannas, and shrubs than in forests, which may be related to the different root functional traits among vegetation types. Considering hydrological conditions, the mean values of both R and R decreased along the gradients of annual SPEI and its slope, suggesting stronger cumulative and lagged effects in drier regions as well as in areas with decreasing water availability. Furthermore, the average accumulated and lagged months tended to decline along the annual SPEI gradient but increase with increasing annual SPEI. Our results revealed that drought has strong cumulative and lagged effects on autumn phenology, and considering these effects could provide valuable information on the vegetation response to a changing climate.
气候变化对秋季叶片衰老（即生长季末期 EOS）有显著影响。相较于温度和降水对 EOS 的影响，干旱的影响尚未得到充分理解，特别是考虑到干旱对植物生长存在明显的累积和滞后效应。在这里，我们研究了干旱（以标准化降水蒸散指数 SPEI 表示）对 1982-2015 年北半球（>30°N）温带生态系统归一化差异植被指数（NDVI3g）EOS 的累积和滞后效应。累积效应由 SPEI 与 EOS 相关性最大的前几个月的数量决定（即 R），而滞后效应由 SPEI 与 EOS 相关性最大的月份决定（即 R）。我们发现，干旱对 EOS 的累积效应影响了 27.2%的植被面积，滞后效应影响了 46.2%的植被面积。对于 R 和 R 发生的主要时间尺度，我们观察到累积效应有 1-4 个累积月，滞后效应有 2-6 个滞后月。在生物群落水平上，与森林相比，干旱对草原、热带稀树草原和灌丛 EOS 的影响更大，这可能与植被类型间不同的根系功能特性有关。考虑到水文条件，R 和 R 的平均值随年 SPEI 及其斜率的梯度而降低，表明在较干旱地区以及水资源可用性降低的地区，累积和滞后效应更强。此外，平均累积和滞后月数随年 SPEI 梯度的增加而减少，但随年 SPEI 的增加而增加。我们的结果表明，干旱对秋季物候有很强的累积和滞后效应，考虑到这些效应可以为植被对气候变化的响应提供有价值的信息。
