气候变化领域集成服务门户(CCPortal): When savannas recover from overgrazing, ecohydrological connectivity collapses

CCPortal

DOI	10.1088/1748-9326/ab71a1
	When savannas recover from overgrazing, ecohydrological connectivity collapses
	Basant S.; Wilcox B.P.; Leite P.M.; Morgan C.L.
发表日期	2020
ISSN	17489318
卷号	15 期号:5
英文摘要	Grasslands and savannas across the globe have undergone a dramatic transition over the past century. Historical overgrazing has set in motion a cascade of events ranging from desertification in arid climates to woody plant encroachment (WPE) in semiarid and subhumid climates. In recent decades, grazing pressure on many of these landscapes has declined significantly, and where rainfall is sufficient (as in most semiarid and subhumid settings), herbaceous vegetation in intercanopy areas will recover. An important question is, how has this transition altered ecohydrological connectivity (overland flow and runoff-runon dynamics)? A woody-plant-encroached, subhumid savanna site in South Texas with a history of heavy grazing (but ungrazed since 1981) was used as a model landscape to address this question. Overland flow, soil moisture, and field saturated hydraulic conductivity (K fs) were measured along a catena extending from the upland savanna-parkland areas to the downslope, more densely wooded areas. For comparison, K fs and infiltrability were also measured at a moderately grazed upland site 14 km east of our study site, selected as a surrogate for past conditions at our site. In contrast to the prevailing hypothesis that the downslope areas ('drainage-woodlands') at our study site have continued to be supported by runoff generated from the upland areas, our measurements yielded no evidence for the redistribution of water from the uplands to the drainage areas under the current ungrazed conditions. Further, K fs at the ungrazed study site was two orders of magnitude higher than that at the grazed site and infiltrability was twice as high at the ungrazed site than the grazed site. These findings, coupled with historical information from the site, strongly suggest that historical overgrazing amplified the runoff-runon process, resulting in significant subsidies of water from the uplands to the drainage areas. Then, with the relaxation of grazing pressure and subsequent landscape recovery, redistribution of water via surface runoff was relatively rare. We believe that our results are generalizable for savannas that have recovered from overgrazing. When these savannas are heavily grazed, ecohydrological connectivity is greatly increased; but if grazing pressure relaxes, ecohydrological connectivity will collapse. These changes in ecohydrological connectivity have important, but not always well understood, ecological consequences. © 2020 The Author(s). Published by IOP Publishing Ltd.
语种	英语
scopus关键词	Ecology; Hydraulic conductivity; Landforms; Plants (botany); Recovery; Soil moisture; Ecological consequences; Field-saturated hydraulic conductivity; Herbaceous vegetation; Historical information; Landscape recovery; Orders of magnitude; Sub-humid climate; Woody-plant encroachments; Runoff; connectivity; ecohydrology; environmental management; grazing management; grazing pressure; habitat restoration; regeneration; savanna
来源期刊	Environmental Research Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/154041
作者单位	Department of Ecosystem Science and Management, Texas AandM University, College Station, TX, United States; Department of Soil and Crop Sciences, Texas AandM University, College Station, TX, United States
推荐引用方式 GB/T 7714	Basant S.,Wilcox B.P.,Leite P.M.,et al. When savannas recover from overgrazing, ecohydrological connectivity collapses[J],2020,15(5).
APA	Basant S.,Wilcox B.P.,Leite P.M.,&Morgan C.L..(2020).When savannas recover from overgrazing, ecohydrological connectivity collapses.Environmental Research Letters,15(5).
MLA	Basant S.,et al."When savannas recover from overgrazing, ecohydrological connectivity collapses".Environmental Research Letters 15.5(2020).