The roots of the drought: hydrology and water uptake strategies mediate forest-wide demographic response to precipitation

Drought-induced tree mortality is expected to increase globally due to climate change, with profound implications for forest composition, function and global climate feedbacks. How drought is experienced by different species is thought to depend fundamentally on where they access water vertically below ground, but this remains untracked so far due to the difficulty of measuring water availability at depths at which plants access water (few to several tens of meters), the broad temporal scales at which droughts at those depths unfold (seasonal to decadal), and the difficulty in linking these patterns to forest-wide species-specific demographic responses. We address this problem through a new eco-hydrological framework: we used a hydrological model to estimate belowground water availability by depth over a period of two decades that included a multi-year drought. Given this water availability scenario and 20yr long-records of species-specific growth patterns, we inversely estimated the re...受气候变化影响，全球范围内干旱诱导的树木死亡率预计将上升，这对森林群落组成、生态系统功能以及全球气候反馈均具有深远影响。学界普遍认为，不同物种所经历的干旱胁迫本质上取决于其在地下垂直方向获取水分的深度，但目前这一机制仍未被探明，原因在于：难以测定植物获取水分的土层深度（数米至数十米）中的土壤水分可利用性，难以监测该深度土层干旱发生的时间尺度（季节至十年尺度），同时难以将这些水文格局与森林内各物种的特异性种群动态响应关联起来。本研究通过构建全新的生态水文框架解决这一难题：我们利用水文模型，在包含多年干旱事件的20年时间序列中，按土层深度估算地下土壤水分可利用性。基于该水分可利用性情景与20年的物种特异性生长记录，我们通过反推方法估算了re...