Lentic Meadows and Riparian Functions Impaired After Horse and Cattle Grazing

Abstract

ABSTRACTPerennially and intermittently available water in lentic, spring‐fed herbaceous meadows supports wetland plants that build and maintain absorbent soil organic matter, capture sediment, prevent erosion, and thereby sustain riparian ecosystems. Enhanced forage and available water attract a diversity of wildlife and grazing animals that can degrade riparian vegetation through prolonged overuse. We tested novel monitoring methods and adapted existing methods to obtain quantified vegetation data that have been consistently linked to riparian functionality and compared these data to ungulate species use. We quantified ungulate use with time‐lapse cameras at 10 Nevada spring‐fed herbaceous meadows where core greater sage‐grouse (Centrocercus urophasianus) habitat, public land grazing allotments, and free‐roaming horse (Equus caballus) herd management areas (Bureau of Land Management) or territories (U.S. Department of Agriculture Forest Service) overlapped. Free‐roaming horses used most study sites over longer periods and grazed more intensely than cattle or domestic sheep. Native ungulate grazing intensity was comparatively negligible. Free‐roaming horses selected spring‐fed meadow sites on average 51 (±33 [SE]) times more than the surrounding rangelands, and cattle selected them 30 ± 23 times more. Within the wettest area of a site, study sites with longer duration of use and higher intensity of use had more soil alteration and bare ground. Riparian ecosystem degradation occurred where meadows had limited rest or recovery time from grazing during the growing season. At all sites we noted loss of riparian function, especially within the hydric areas with the highest potential to grow abundant cover of stabilizing wetland plant species. Transects for monitoring soil alteration and vegetation cover in this hydric location can provide a leading indicator of riparian recovery or degradation and help in adjusting free‐roaming horse population levels or livestock management strategies. © 2021 The Wildlife Society.