Salomón Roberto L, Camarero J Julio
Departamento de Sistemas y Recursos Naturales, Research Group FORESCENT, Universidad Politécnica de Madrid, Madrid, Spain.
Instituto Pirenaico de Ecología (IPE-CSIC), Zaragoza, Spain.
Plant Cell Environ. 2025 Jan;48(1):866-881. doi: 10.1111/pce.15177. Epub 2024 Oct 3.
Stem growth responses to soil and atmospheric drought are critical to forecasting the tree carbon sink strength. Yet, responses of drought-prone forests remain uncertain despite global aridification trends. Stem diameter variations at an hourly resolution were monitored in five Mediterranean tree species from a mesic and a xeric site for 6 and 12 years. Stem growth and dehydration responses to soil (REW) and atmospheric (VPD) drought were explored at different timescales. Annually, growth was determined by the number of growing days and hours. Seasonally, growth was bimodal (autumn growth ≈ 8%-18% of annual growth), varying among species and sites across the hydrometeorological space, while dehydration consistently responded to REW. Sub-daily, substantial growth occurred during daytime, with nighttime-to-daytime ratios ranging between 1.2 and 3.5 (Arbutus unedo ≈ Quercus faginea < Quercus ilex < Pinus halepensis in the mesic site, and Juniperus thurifera < P. halepensis in the xeric site). Overall, time windows favourable for growth were limited by soil (rather than atmospheric) drought, modulating annual and seasonal growth in Mediterranean species, and stems maintained non-negligible growth during daytime. These patterns contrast with observations from wetter or cooler biomes, demonstrating the growth plasticity of drought-prone species to more arid climate conditions.
茎干对土壤和大气干旱的生长响应对于预测树木碳汇强度至关重要。然而，尽管全球干旱化趋势明显，但易干旱森林的响应仍不确定。在一个湿润和一个干旱地点，对五种地中海树种的茎干直径变化进行了每小时分辨率的监测，持续了6年和12年。在不同时间尺度上探讨了茎干生长和对土壤（有效水含量）及大气（水汽压亏缺）干旱的脱水响应。每年，生长由生长天数和小时数决定。季节性上，生长呈双峰模式（秋季生长约占年生长的8%-18%），在水文气象空间中的不同物种和地点有所变化，而脱水始终对有效水含量作出响应。在亚日尺度上，白天有大量生长，夜间与白天的比率在1.2至3.5之间（在湿润地点，草莓树≈欧洲水青冈<冬青栎<阿勒颇松，在干旱地点，刺柏<阿勒颇松）。总体而言，有利于生长的时间窗口受土壤（而非大气）干旱限制，调节着地中海物种的年生长和季节生长，并且茎干在白天保持着不可忽视的生长。这些模式与来自更湿润或更凉爽生物群落的观察结果形成对比，表明易干旱物种对更干旱气候条件的生长可塑性。
