Queally Natalie, Zheng Ting, Ye Zhiwei, Kovach Kyle R, Pavlick Ryan, Shafron Ethan, Schneider Fabian D, Townsend Philip A
Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, Wisconsin, USA.
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA.
Glob Chang Biol. 2025 May;31(5):e70246. doi: 10.1111/gcb.70246.
California's 2012-2016 megadrought led to the mortality of over 100 million trees. In the context of extreme drought and insect outbreaks, a holistic view of plant functional traits can provide further insight into underlying physiological and abiotic drivers of the patterns of mortality. We used new maps of early-drought (pre-mortality) foliar functional traits derived from the NASA AVIRIS-Classic imaging spectrometer, along with open-access climate, topography, canopy structure, and mortality data, to assess competing influences on drought mortality at the Soaproot Saddle and Lower Teakettle NEON sites in the southern Sierra Nevada Mountains. We aimed to (1) compare mortality trends across two independently derived mortality datasets, (2) assess trait-mortality relationships across diverse sites and species, and (3) link these relationships to mechanisms of tree-level drought response. We used random forests to assess the relative importance of mortality drivers and the trends of mortality across each predictor gradient. For the lower elevation, more water-limited Soaproot Saddle site, conifer mortality was linked to taller, drier canopies while broadleaf mortality was linked to foliar traits (lower cellulose, higher sugars, and higher leaf mass per area). For the higher elevation, more energy-limited Lower Teakettle site, mortality was more strongly linked to elevation and climate, with little influence from foliar traits.
加利福尼亚州2012 - 2016年的特大干旱导致超过1亿棵树木死亡。在极端干旱和虫害爆发的背景下，对植物功能性状的整体看法可以进一步洞察树木死亡模式背后的生理和非生物驱动因素。我们利用来自美国国家航空航天局（NASA）的AVIRIS - Classic成像光谱仪获取的早期干旱（死亡前）叶片功能性状新地图，以及开放获取的气候、地形、冠层结构和死亡率数据，来评估内华达山脉南部Soaproot Saddle和Lower Teakettle NEON站点干旱死亡率的竞争影响因素。我们旨在（1）比较两个独立得出的死亡率数据集中的死亡率趋势，（2）评估不同站点和物种间性状与死亡率的关系，以及（3）将这些关系与树木水平的干旱响应机制联系起来。我们使用随机森林来评估死亡率驱动因素的相对重要性以及每个预测变量梯度上的死亡率趋势。对于海拔较低、水分限制更大的Soaproot Saddle站点，针叶树死亡率与更高、更干燥的冠层有关，而阔叶树死亡率与叶片性状（较低的纤维素、较高的糖分和较高的单位面积叶质量）有关。对于海拔较高、能量限制更大的Lower Teakettle站点，死亡率与海拔和气候的联系更为紧密，叶片性状的影响较小。
