Micro-patterns in grassland vegetation created and sustained by sheep-grazing

Abstract

An initially uniform Holcus lanatus-dominated sward came partly under hay-making and partly under sheep-grazing. Preferential grazing by sheep resulted in grazing at different intensities giving rise to a macro-pattern of various plant communities. Besides this macro-pattern a micro-pattern developed in the grazed area, which was absent under hay-making. In the micro-pattern short, heavily grazed areas alternated with taller, lightly grazed patches, both having the same species composition. The heavily grazed area was characterized by equal amounts of monocots and dicots. The lightly grazed patches were dominated by Agrostis tenuis, and had a large amount of litter which probably causes the absence of mosses. The protein percentage of green material is higher in the heavily grazed areas than in the lightly grazed patches.Sequential charting indicated that the micro-pattern was more or less stable. An interaction between the vegetation micro-pattern and grazing patterns is suggested. Heavy grazing results in forage with a high protein content and hence attracts animals. Light grazing results in forage with a relatively low protein content, animals avoid the area and litter accumulates.

Capitulum and rosette leaf avoidance from grazing by large herbivores in Taraxacum

“…Grasses and forbs show different responses to grazing by large herbivores. For example, grasses that have a growing point at the leaf base (intercalary meristem) can endure grazing and give rise to short, grazed lawns (Hunter 1962;Bakker et al 1983;McNaughton 1984). However, forbs with rosette leaves, including Taraxacum, can provide low ground cover but incur damage from grazing.…”

Modelling the structural changes in vegetation under different grazing regimes

“…Areas previously grazed will be revisited regularly to harvest the regrowth of young shoots of high palatability and nutritive value; this leads to a mosaic pattern of heavily used and virtually unused vegetation. A pattern of the levels 'land unit', 'between community' and 'within community' can be distinguished (Oosterveld, 1976;Bakker et al, 1984;Hillegers, 1984;Putman, 1986). If the grazing management is stable, this pattern will be enhanced; areas of short herbaceous cover will be maintained, while the ungrazed areas follow a succession via tall grasses and forbs and shrub and tree establishment to woodland and forest.…”

“…2). The changes in vegetation structure caused by selective grazing, trampling, and manuring are followed by changes in the plant species composition ( Van de Laar & Slim, 1979;Bakker et al, 1983;Bakker et al, 1984). Relatively little research has been done on changes in the fauna under extensive grazing.…”

Interspecific Competition Interacts with the Spatial Distribution of a Palatable Grass to Reduce Its Recruitment

“…In many rangelands, inadequate grazing management triggered degradation evidenced by decreases in plant cover, changes in plant-community structure, decreases in the abundance of palatable species, encroachment of woody plants, and soil erosion (Westoby 1980;Walker et al 1981;Brown and Archer 1989;Archer 1990;Schlesinger et al 1990;van Auken 2000). Furthermore, grazing can disrupt the original spatial patterns of plant communities at different scales and generate new associations among remnant species (Bakker et al 1983;Papatheodorou et al 1993;Berg et al 1997;Dale and Zbigniewicz 1997;Adler et al 2001;Cipriotti and Aguiar 2005). In many rangelands throughout the world, the remaining individuals of the highly preferred species (i.e., palatable species) grow in places protected from herbivores, e.g., refuges under the canopy of woody plants, cactus clumps, or near less palatable species (Bakker et al 1983;Berg et al 1997;Rebollo et al 2002;Oesterheld and Oyarzá bal 2004).…”

“…Furthermore, grazing can disrupt the original spatial patterns of plant communities at different scales and generate new associations among remnant species (Bakker et al 1983;Papatheodorou et al 1993;Berg et al 1997;Dale and Zbigniewicz 1997;Adler et al 2001;Cipriotti and Aguiar 2005). In many rangelands throughout the world, the remaining individuals of the highly preferred species (i.e., palatable species) grow in places protected from herbivores, e.g., refuges under the canopy of woody plants, cactus clumps, or near less palatable species (Bakker et al 1983;Berg et al 1997;Rebollo et al 2002;Oesterheld and Oyarzá bal 2004). This close association among adult plants results from a balance between protection against domestic grazers and interspecific competition (Oesterheld and Oyarzá bal 2004).…”