Response of Riparian Vegetation, Instream Habitat, and Aquatic Biota to Riparian Grazing Exclosures

Abstract

Improper riparian grazing can alter riparian vegetation and reduce streambank stability, negatively impacting aquatic habitat and biota. We evaluated differences in riparian and instream habitat, benthic macroinvertebrates, and fish inside versus outside seven riparian exclosures constructed from 1982 to 2005 in Idaho. The normalized difference vegetation index from Landsat imagery (1985 to 2015) showed significant increases in riparian vegetation productivity after some but not all exclosures were constructed. Field data collected in 2015 showed woody riparian vegetation to be more abundant, streambanks less altered, and stream channels narrower inside versus outside exclosures, as we expected. However, instream habitat, a benthic macroinvertebrate index, fish species richness, and adult salmonid density showed no response. Higher age‐0 salmonid densities were the only aquatic organism response observed. Broader watershed‐scale factors likely limited strong and consistent responses by aquatic biota to exclosures. We conclude that riparian exclosures have localized effects on stream systems, such as increased riparian vegetation, reduced streambank alteration, and improved channel stability, but may not always influence aquatic biota that commonly reflect larger watershed‐scale processes and conditions. Therefore, well‐maintained riparian exclosures should be used to eliminate livestock use in localized areas of stream corridors that are sensitive to disturbance. To improve stream health at the larger watershed scale that is relevant to most aquatic biota, exclosures should only be one of several grazing management tools implemented simultaneously to reduce the impacts of improper livestock grazing.

Livestock management, beaver, and climate influences on riparian vegetation in a semi-arid landscape

“…Prior research has elucidated relationships between grazing management, beaver, climate, and stream characteristics individually or in tandem relative to riparian area productivity in arid and semi-arid landscapes. For example, Huntington and others [48] described the correlation between climate and riparian vegetation vigor measured as NDVI, while multiple studies have demonstrated recovery of willow and other riparian vegetation with exclosure or alternative management of livestock grazing [73, 96–99], including in adjacent watersheds [53, 100, 101]. Similarly, an increasing body of literature describes the anticipated riparian area benefits associated with beaver activity and identifies those physical and biological site conditions conducive to extensive beaver dam development [37–47, 87].…”

“…We demonstrate that grazing management within exclosures can yield riparian area vegetation productivity comparable to those produced by conservation-oriented grazing management, and that beaver dams can increase the recovery effects of each of these grazing strategies, but other considerations may dictate which treatment land managers apply to meet riparian objectives. In practice, conservation-oriented grazing strategies may be preferable to exclosures due to ease of implementation, flexibility, and scale of impact [28, 100]. We acknowledge that our categorization of grazing management into three treatments may be overly simplistic but chose general categories to facilitate comparison across watersheds and time.…”

Riparian Land Use and Hydrological Connectivity Influence Nutrient Retention in Tropical Rivers Receiving Wastewater Treatment Plant Discharge

“…First, riparian vegetation can act as a buffer preventing nutrient loads from non-point sources via agricultural and urban surface runoff. The consolidation of riparian buffers (permanently vegetated areas between rivers and the surrounding landscape) is among the nutrient mitigation best management practices (Dauwalter et al, 2018;Krzeminska et al, 2019), also in the context of restoration initiatives (McMillan et al, 2014;Johnson et al, 2016). Second, the lateral hydrological connectivity between riparian areas and the main channel can stimulate riparian biogeochemical processes that can reduce nutrient loads transported downstream (Reckendorfer et al, 2013;Vigiak et al, 2016;Covino, 2017).…”

Spatial patterns of meadow sensitivities to interannual climate variability in the Sierra Nevada

“…Landsat satellite imagery has proven to be an effective and efficient data source for monitoring key ecological attributes of meadows and riparian systems over extensive areas and time periods (Ager & Owens, ; Cartwright & Johnson, ; Cohen & Goward, ), including above‐ground biomass, which relates to vegetation structure, function and composition, and vegetation water content. Recent advances in cloud computing (Gorelick et al, ) now permit efficient application of algorithms across the Landsat satellite image archive for long‐term monitoring of groundwater dependent ecosystems with respect to climate and management (Dauwalter, Fesenmyer, Miller, & Porter, ; Hausner et al, ; Huntington et al, ).…”