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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Rangeland Resources & Systems Research » Research » Publications at this Location » Publication #311594
Title: Fenceline contrasts: Grazing increases wetland surface

Author
item BOOTH, D - Retired ARS Employee
item COX, SAMUEL - Bureau Of Land Management
item LIKENS, J - Retired Non ARS Employee

Submitted to: Wetlands Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2014
Publication Date: 8/22/2014
Publication URL: http://handle.nal.usda.gov/10113/60991
Citation: Booth, D.T., Cox, S.E., Likens, J.C. 2014. Fenceline contrasts: Grazing increases wetland surface. Wetlands Ecology and Management. 23:183-194.

Interpretive Summary: Fresh water stored on the earth’s mountains as ice and snow is being lost to global warming, resulting in changing streamflows and rising concern for irrigators and fisheries. A potential mitigation strategy is to increase liquid-water storage capacity of high-elevation wetlands through management that reduces the channels that increase drainage and rapid runoff. We compared surface roughness resulting from wetland hummocks and inter-hummock channels at six fencelines on four high-elevation meadow and wetland complexes using both photogrammetric (photo) and erosion bridge (EB) methods. Surface roughness was 1.7 (EB) and 1.5 (photo) times greater on wetlands where grazing removed most of the annual growth compared to wetlands where that grow was allowed to accumulate as water-storing organic matter; historical aerial photography provided supporting evidence for our findings. We conclude that wetland hummocks and inter-hummock channels result primarily from in-the-wetland grazing by domestic livestock and that reducing wetland surface roughness will increase liquid-water storage capacity.

Technical Abstract: A warming earth has lost substantial mountain-stored frozen fresh water, thus generating a pressing need for greater liquid–water storage within upperelevation riparian systems. Liquid–water storage can be enhanced by avoiding microtopographic channels that facilitate land drainage and rapid runoff. A number of authors have attributed certain forms of wetland hummocks and inter-hummock channels to grazing livestock but there is little evidence in the scientific literature for a cause and effectmechanism.We used comparisons at six fencelines on four meadow and wetland complexes to test the null hypothesis that grazing management makes no difference in hummocks and inter-hummock channels measured as surface roughness. Surface roughness was measured both photogrammetrically (photo) and with an erosion bridge (EB), and the measurements expressed as surface roughness indices (SRIs). Wetland surface roughness inside fenced areas was 44 (EB) and 41 (photo). Wetland surface roughness outside fenced areas was more than 50 % higher (p\0.0001), measuring 76 (EB, n = 6) and 62 (photo, n = 4). The site with the longest period of conservation management (50? years) had the lowest inside EB SRI at 27. The two independent measurement methods, EB and photo, yielded similar, correlated results (R = 0.71, n = 8). Historical aerial photography provides supporting evidence for our findings. We reject the null hypothesis and while we suspect macrotopography, hydrology, soil type, and climate are factors in hummock formation, our evidence supports the thesis that hummocks formed surface-down by inter-hummock channels result primarily from grazing by domestic livestock.