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ARS Home » Pacific West Area » Burns, Oregon » Range and Meadow Forage Management Research » Research » Publications at this Location » Publication #305259
Title: Effects of feral free-roaming horses on semi-arid rangeland ecosystems: an example from the sagebrush steppe

Author
item Davies, Kirk
item COLLINS, GAIL - Us Fish And Wildlife Service
item Boyd, Chad

Submitted to: Ecosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2014
Publication Date: 10/22/2014
Publication URL: http://handle.nal.usda.gov/10113/60032
Citation: Davies, K.W., Collins, G., Boyd, C.S. 2014. Effects of feral free-roaming horses on semi-arid rangeland ecosystems: an example from the sagebrush steppe. Ecosphere. 5(10):127. doi: 10.1890/ES14-00171.1.

Interpretive Summary: Information on the influence of feral horses on vegetation and soil characteristics in the sagebrush steppe is limited and has resulted in controversy regarding their management. We compared vegetation and soil surface characteristics in feral horse grazed and ungrazed (exclosures) areas at five sites in northern Nevada. Horse grazed areas had lower sagebrush density and plant diversity, greater soil penetration resistance, and lower soil aggregate stability than ungrazed areas. The cumulative effect of feral horse grazing on soil characteristics suggests that they are increasing the risk of soil erosion and potentially decreasing the availability of water for plant growth. The two-fold increase in sagebrush density with horse exclusion suggest that feral horses limit sagebrush recruitment and thereby may negatively impact sage-grouse and other sagebrush associated wildlife. These results suggest that the effects of feral horses on sagebrush ecosystems should be considered when developing conservation plans for sagebrush steppe communities and associated wildlife. The results of this study also suggest that the policy of minimal management of feral horses may not be scientific sound ecosystem management for arid and semi-arid rangelands.

Technical Abstract: Feral horses (Equus caballus) are viewed as a symbol of freedom and power; however, they are also a largely unmanaged, non-native grazer in North America, South America, and Australia. Information on their influence on vegetation and soil characteristics in semi-arid rangelands has been limited by confounding effects of cattle grazing and a lack of empirical manipulative studies. We compared vegetation and soil surface characteristics in feral horse grazed areas and ungrazed exclosures at five sagebrush (Artemisia L.) steppe sites in northern Nevada. Horse grazed areas had lower sagebrush density and plant diversity, greater soil penetration resistance, and lower soil aggregate stability than ungrazed areas. Herbaceous cover and density generally did not differ between treatments. The cumulative effect of feral horses on soil characteristics suggests that they may affect the ecological function of semi-arid rangelands by increasing the risk of soil erosion and potentially decreasing the availability of water for plant growth. The two-fold increase in sagebrush density with horse exclusion suggest that feral horses limit sagebrush recruitment and thereby may negatively impact Greater sage-grouse (Centrocercus urophasianus) and other sagebrush associated wildlife. These results suggest that the effects of feral horses on sagebrush and other semi-arid ecosystems should be considered when developing conservation plans for these ecosystems and associated wildlife.