Livestock Impacts on Riparian Ecosystems and Streamside Management Implications... A Review

Abstract

Historically, riparian vegetation has been defined as vegetation rooted at the water's edge (Campbell and Franklin 1979). Quite often, however, the stream influences vegetation in many ways and well beyond the water line. In lotic systems, the stream is not only responsible for increased water availability, but also for the soil deposition, unique microclimate, increased productivity, and the many consequential, self-perpetuating biotic factors associated with riparian zones. These factors all contribute in the formation of a unique assemblage of plant communities quite distinct from upland communities surrounding the riparian zone. Therefore, along streambanks, other lotic systems, and even ephemeral drainages, riparian ecosystems could best be defined as those assemblages of plant, animal, and aquatic communities whose presence can be either directly or indirectly attributed to factors that are stream-induced or related (Kauffman 1982). Riparian zones can vary considerably in size and vegetation complexity because of the many combinations that can be created between water sources and physical characteristics of a site (Odum 1971, Platts 1979, Swanson et al. 1982). Such characteristics, include gradient, aspect, topography, soil type of streambottom, water quality, elevation, and plant community (Odum 1971). However, riparian zones, particularly those bordering streams or rivers, have several characteristics in common. They are ecotonal, with high edge to area ratios (Odum 1978). As functional ecosystems they are very open with large energy, nutrient, and biotic interchanges with aquatic systems on the inner margin (Cummins 1974, Odum 1978, Sedel et al. 1974) and upland terrestrial ecosystems on the other margin (Odum 1978). Thomas et al. (1979) stated that all riparian zones within managed rangelands of the western United States have the following in common: (1) they create well-defined habitat zones within the much drier surrounding areas; (2) they make up a minor proportion of the overall area; (3) they are generally more productive in terms of biomass-plant and animal-than the remainder of the area; and (4) they are a critical source of diversity within rangelands. Both density and diversity of species tends to be higher at the

Cattle herbage utilization patterns under high-density rotational grazing in the Aspen Parkland

“…Greater absolute biomass removal from riparian meadows corroborates results from other studies (e.g., Kauffman and Krueger 1984;Gillen et al 1985;Willms 1988) on the importance of riparian meadows as foraging sites for livestock. Given that cattle tend to be more selective at the beginning of a rotational grazing period (Walker et al 1989), the visitation frequency data documented here tend to support the notion that livestock occupy riparian meadows immediately upon initiation of the grazing period.…”

“…Localized overuse can significantly affect plant community composition (Kauffman and Krueger 1984), in turn affecting other rangeland values including wildlife habitat (Schulz and Leininger 1990). Despite their importance, riparian zones have often been overlooked because of their small size relative to the entire landscape (Gillen et al 1985), and accordingly, are more likely to be overgrazed, particularly under season-long grazing systems (Platts 1990).…”

“…This recommendation appears to assume that grazing is incompatible with the safe utilization and long-term conservation of riparian vegetation. Other evidence exists, however, suggesting riparian productivity and soil properties can be maintained or improved under appropriate livestock grazing strategies (e.g., Kauffman and Krueger 1984;Elmore 1992;Kie and Boroski 1996). For instance, rotational grazing may promote more uniform distribution of grazing pressure across the landscape (Platts 1990).…”

Overgrazing in the Montado? The need for monitoring grazing pressure at paddock scale

“…Photographic records could be used to assess ground cover, representing the amount of plant material (dead or alive) that covers the soil surface, expressed as a percentage. Ground cover, although not representing biomass availability, could be used as an alternative alarm indicator for overgrazing (Kauffman and Krueger 1984). To our knowledge, ground image information has not been used for monitoring montados, though, a preliminary study (Rato et al 2013) where an image processing technique was tested has shown a 95 % correlation between manual and image processing evaluation of vegetation ground cover.…”

“…Because legumes tend to be more sensitive to treading damage than grasses, a shift on pasture composition toward grasses may occur under heavy hoof action with consequent reduction on plant diversity. Damage from treading is typically higher on heavy clay soils and is greatly increased under high soil moisture conditions (Kauffman and Krueger 1984). Treading can also create gaps in the sward, which may be suitable for plant regeneration thus having a positive effect on the establishment of annual and bi-annual species (Metera et al 2010).…”