Impact of stocking rate on species diversity and composition of a subtropical grassland in Argentina

Abstract

Questions: What is the effect of a range of controlled stocking rates on plant species richness and diversity?Location: Subtropical grasslands of Corrientes, Argentina, South America. Methods:We studied the effect of three controlled stocking rates (0.6, 0.8 and 1.0 cow equivalentsÁha À1 ) on species diversity and composition during 8 yr. We calculated species diversity using the antilog of the Shannon-Wiener index, and considered its two components, richness and evenness. We also assessed the proportion of prostrate and erect species. Species abundance was based on biomass estimations.Results: Species diversity under high stocking rates gradually decreased throughout the experiment and became nearly 50% lower than under low stocking rate. This decline was largely accounted for by changes of evenness because species richness was not affected by stocking rates. Species composition clearly diverged among the three treatments over time. Low stocking rate maintained a fairly constant relative cover of erect and prostrate grasses throughout the experiment, whereas intermediate and high stocking rate treatments were gradually and consistently enriched in prostrate grasses and forbs. These effects occurred simultaneously with drastic inter-annual changes likely driven by annual precipitation. Conclusions:The range of stocking rates had no effect on species richness, but reduced diversity through the effect on evenness. High stocking rate progressively increased the proportion of prostrate species in the biomass.

Changes in vegetation composition and structure following livestock exclusion in a temperate fluvial wetland

“…Livestock grazing may favor the development of prostrate‐growth or grazing‐avoider species, as reported for other pasture types (McNaughton, , ; Pucheta, Cabido, Díaz, & Funes, ; Dalle Tussie, ; Díaz et al., ; Pizzio et al., ). Among these, we recorded a high abundance of Cynodon dactylon and Mimosa pigra .…”

“…Livestock grazing may favor the development of prostrategrowth or grazing-avoider species, as reported for other pasture types (McNaughton, 1979(McNaughton, , 1985Pucheta, Cabido, Díaz, & Funes, 1998;Dalle Tussie, 2004;Díaz et al, 2007;Pizzio et al, 2016).…”

Regional productivity mediates the effects of grazing disturbance on plant cover and patch‐size distribution in arid and semi‐arid communities

“…Most of our knowledge about grazing effects on vegetation comes from studies that compare exclosure areas with grazed areas in one environmental location (Milchunas and Lauenroth 1993, Pizzio et al 2016, Herrero-Jáuregui and Oesterheld 2018, generally without an accurate characterization of grazing pressure. Nevertheless, general models indicate that experimental evidence of different grazing pressures along productivity gradients is needed to test hypotheses about grazing effects (Milchunas et al 1988, Westoby et al 1989, Cingolani et al 2005, Oesterheld and Semmartin 2011.…”

Effects of High Impact Grazing on Species Diversity and Plant Functional Groups in Grasslands of Northern Argentina

“…In general, the effects of grazing on plant species composition and diversity are well documented for most of the world's grassland ecosystems [13][14][15][16][17]. However, contrasting results regarding reduced, unaffected or even increased diversity or shifts in plant functional groups were reported.…”

“…Most literature dealing with grazing intensity relates specifically to management with continuous grazing. The latter is determined by the stocking rates, compared to carrying capacity [16,20]. Nevertheless, sustainable grazing management must avoid overstocking and overgrazing [9,21].…”