Groundwater subsidizes tree growth and transpiration in sandy humid forests
Groundwater subsidizes tree growth and transpiration in sandy humid forests
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DOI：
10.1002/eco.2294
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发表时间：
2021-04
期刊：
影响因子：
2.6
通讯作者：
D. Ciruzzi;S. Loheide
中科院分区：
文献类型：
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作者：
D. Ciruzzi;S. Loheide
随着地球仪森林干旱变异性的增加，评估和了解减轻干旱影响的生态系统属性至关重要。干旱和半干旱生态系统中的树木可以通过获取浅层地下水来维持干旱期间的树木生长和蒸腾，但地下水对潮湿环境中森林生长和蒸腾的影响程度在很大程度上尚未被探索。我们量化了地下水对北方湿润森林和桑迪土壤中树木生长和蒸腾的影响。我们假设，即使在潮湿的地区，土壤干旱发生相对频繁的森林与桑迪土壤，并导致水分胁迫和树木生长减少。此外，我们假设，如果森林在干旱条件下可以获得浅层地下水，这些生产力的降低会得到改善。我们使用树脂松树木的树芯评估了树木的生长反应，并根据覆盖1至9 m深度地下水（DTG）梯度的地点的昼夜地下水位波动估计了森林地下水的使用。在地下水较浅的地区（DTG < 2.5 m），我们观察到树木的生长速度是原来的两倍，而且地下水的使用频率很高（在夏季非雨天中高达81%）。地下水对树木生长和蒸腾作用的影响随地下水沿着DTG梯度的加深而减小，地下水深度在地表以下1-5 m范围内。这些研究结果表明，水提供了一个浅的地下水位补贴在潮湿的森林蒸散，提高树木生长的结果。我们的研究为理解地下水在潮湿森林中赋予抗旱性的作用提供了基础，以帮助指导可持续的水和森林管理决策。
As drought variability increases in forests around the globe, it is critical to evaluate and understand ecosystem attributes that ameliorate drought impacts. Trees in arid and semi‐arid ecosystems can sustain tree growth and transpiration during drought by accessing shallow groundwater, yet the extent to which groundwater influences forest growth and transpiration in humid environments has largely been unexplored. We quantified groundwater's influence on tree growth and transpiration in northern humid forests with sandy soils. We hypothesized that even in wet regions, soil droughts occur relatively frequently in forests with sandy soils and result in water stress and reduced tree growth. Further, we hypothesized these reductions in productivity are ameliorated if the forest can access shallow groundwater during dry conditions. We evaluated tree growth responses using tree cores in Pinus resinosa trees and estimated forest groundwater use from diel water table fluctuations across sites covering a 1‐ to 9‐m depth‐to‐groundwater (DTG) gradient. In areas of shallow groundwater (DTG < 2.5 m), we observed twice as much tree growth and high, frequent groundwater use (up to 81% of non‐rainy summer days). Groundwater's influence on tree growth and transpiration declined as groundwater deepened along the DTG gradient in the range 1–5 m below land surface. These findings suggest that water provided by a shallow water table subsidizes evapotranspiration in humid forests and results in enhanced tree growth. Our research provides a basis for understanding the role of groundwater in conferring drought resistance in humid forests to help guide sustainable water and forest management decisions.