Drier streams despite a wetter climate in woody-encroached grasslands
Drier streams despite a wetter climate in woody-encroached grasslands
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DOI：
10.1016/j.jhydrol.2023.130388
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发表时间：
2023-11
影响因子：
6.4
通讯作者：
K. Sadayappan;R. Keen;K. M. Jarecke;Victoria Moreno;J. Nippert;Matthew F. Kirk;Pamela L. Sullivan;Li Li-Li
中科院分区：
文献类型：
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作者：
K. Sadayappan;R. Keen;K. M. Jarecke;Victoria Moreno;J. Nippert;Matthew F. Kirk;Pamela L. Sullivan;Li Li-Li
在全球范围内，覆盖无冰地球表面40%的草原正在遭受树木的侵蚀。森林侵蚀的水文影响是高度不确定的，因为它们被气候变化的同步影响复杂化了。在这里，我们提出了以下问题：1)在森林侵占的草原上，水平衡（蒸散与径流）和径流分配（地表径流和地下径流）是如何随着时间的推移而演变的？2)气候变化与森林侵蚀的相对影响是什么？我们使用了HBV-light水文模型和几十年的水文气象和河流数据，这些数据来自美国堪萨斯州康扎草原两个不同程度的树木侵蚀的间歇溪流。结果表明，随着时间的推移，两条河流都变得更加干燥，并且经历了更多的水文干旱，特别是在被侵占的地点，尽管气候更加湿润，但蒸散量增加。相比之下，一个没有树木侵蚀的“仅气候”情景模型表明，仅在气候变化的情况下，河流流量就会增加。此外，研究结果表明，在被侵占的场地，随着深层地下水流量的增加，流道也会加深。这些发现提出了关于这些变化的机制以及在森林侵占地区和其他地区潮湿气候下干燥溪流的共性的问题。这些问题的答案可能对干旱的发生、水的可用性、水质和生态系统健康产生深远的影响。
Grasslands, covering 40% of ice-free Earth surface, are experiencing woody encroachment globally. The hydrological impacts of woody encroachment are highly uncertain because they are compounded by the concurrent influence of climate change. Here we ask the questions 1)How water balance (evapotranspirationversusstreamflow) and streamflow partitioning (into surface runoff and subsurface flows) evolve over time in woody-encroached grasslands?2)What is the relative influence of climate change and woody encroachment?We used the hydrology model HBV-light and decades of hydrometeorological and streamflow data from two intermittent streams draining catchments with different degrees of woody encroachment at the Konza Prairie, Kansas, US. Results indicate that both streams have become drier and have experienced more hydrological droughts over time, more so in the substantially encroached site, with increasing evapotranspiration despite a wetter climate. In contrast, a modelled hypothetical “Climate Only” scenario without woody encroachment suggests streamflow would have increased under climate change alone. Moreover, results suggest that flow paths have deepened with increasing fractions of deeper groundwater flow in the substantially encroached site. These findings raise questions about mechanisms of these changes and commonality of drier streams in a wetter climate in woody-encroached areas and beyond. Answers to these questions can have far-reaching implications for the occurrence of droughts, water availability, water quality, and ecosystem health.