Soil moisture has a direct influence on biomass production, food security, and ecosystem functioning, thus resources management in water‐limited environments could be improved if feedbacks between water and vegetation were fully understood. This study tries to define the sensitivity of annual pastures under the influence of different vegetation covers to soil water availability during two contrasting growing seasons, dry and wet. For this reason, soil water content was continuously monitored during two complete hydrological years using capacitance sensors, which were gathered in soil moisture stations located in open grasslands and beneath tree canopies. Pasture growth was recorded by measurements of its height and by biomass cuts. The study was conducted on three private farms located in savanna‐like ecosystems of Spain (dehesa) with Mediterranean climate. Results highlighted the importance of the topsoil (first 15 cm) as the main layer for water supply of natural grasses. Soils below canopies registered longer and more intense water deficits than those located in grasslands. This was reflected in biomass growth, given that when growing conditions were dry, pasture yield decreased more than 40% in grasslands and more than 50% below tree canopies. The studied ecosystems occupy millions of hectares in Spain and Portugal and present a canopy cover up to 40%. If dry episodes become more frequent in the present century due to climate change, important surface, especially under trees, could become drier, less productive, and therefore more prone to land degradation.

中文翻译：

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水分受限环境下土壤水分和植被覆盖对生物量生长的影响

土壤水分直接影响生物量生产，粮食安全和生态系统功能，因此，如果充分了解水和植被之间的反馈，则可以改善水有限环境中的资源管理。这项研究试图定义在两个相反的生长季节（干燥和潮湿）下，不同植被覆盖对一年生牧场的敏感性对土壤水分的利用。因此，在两个完整的水文年中，使用电容传感器连续监测土壤含水量，这些电容传感器收集在位于开阔草原和树冠下的土壤水分站中。通过测量牧场的高度和减少生物量来记录牧场的生长。这项研究是在西班牙（Savanna-like）生态系统中的三个私人农场上进行的（dehesa），地中海气候。结果强调了表层土壤（前15厘米）作为天然草供水的主要层的重要性。与位于草原的土壤相比，冠层下的土壤缺水时间更长，强度更大。鉴于在干燥的生长条件下，草地的牧草产量下降了40％以上，在树冠下下降了50％以上，这反映在生物量的增长上。所研究的生态系统在西班牙和葡萄牙占据了数百万公顷的土地，其冠层覆盖率高达40％。如果本世纪由于气候变化而导致干旱发作更加频繁，那么重要的表面（尤其是树木下的表面）可能会变得更干燥，生产力更低，因此更容易发生土地退化。