Soil phytoliths as evidence for species replacement in grazed rangelands of central Argentina

Abstract

Iglesias, R. M. 2004. Soil phytoliths as evidence for species replacement in grazed rangelands of central Argentina. Á/ Ecography 27: 725 Á/732.Rangeland utilization for livestock production in central Argentina has apparently resulted in the replacement of preferred mid-grasses (Poa ligularis and Stipa clarazii ) by preferred short-grasses (Piptochaetium napostaense and Stipa tenuis ) and avoided grasses (Stipa tenuissima and Stipa eriostachya ). However, the botanical composition in the pristine condition is unknown due to the lack of historical data and relict areas. The objective of this study was to analyze soil phytolith assemblages from a representative site of central Argentina rangelands to test the presumed floristic changes. Soil phytolith assemblages (SPAs) were compared with three plant phytolith assemblages (PPAs), each of it made up of two species. One PPA was integrated by the preferred mid-grasses P. ligularis and S. clarazii , another by the preferred short-grasses P. napostaense and S. tenuis, and a third one by the avoided grasses S. eriostachya and S. tenuissima . For each PPA, the proportion of species representing the best fit with SPAs was estimated by considering all possible lineal combinations between the phytolith assemblage of the two integrating species, and selecting that representing the minimum distance to SPA. The highest degree of similarity between SPAs and PPAs corresponded to the PPA integrated by P. ligularis and S. clarazii . Our results support the hypothesis of the dominance of preferred mid-grasses in the pristine condition in rangelands of central Argentina, and that a shift towards the dominance of preferred short-grasses and avoided grasses has occurred in its present disturbed condition.L. Gallego, R. A. Distel

Effect of fencing and grazing on a Kobresia-dominated meadow in the Qinghai-Tibetan Plateau

“…Functional groups were the same with Fig. 2 are excluded for ten or more years (Distel and Boo 1996;Moretto and Distel 1997;Gallego et al 2004). In concordance, graminoids and sedge species, which dominate in alpine community and are palatable for herbivores, showed significant improvement in fenced meadows.…”

Effects of artificial grassland establishment on soil nutrients and carbon properties in a black-soil-type degraded grassland

“…This is also related to a stronger growth and competitive advantage shown by Elymus nutans. Previous research has reported that palatable grasses have greater competitive ability and show a greater increase in abundance in grasslands than unpalatable grasses where livestock are excluded (Distel and Boo 1996;Moretto and Distel 1997;Gallego et al 2004). Furthermore, palatable grasses which had higher productivity and quality can lock abundant nutrients within their tissues from the soil (Moretto and Distel 1997;Harris et al 2007).…”

Cumulative effects of 20-year exclusion of livestock grazing on above- and belowground biomass of typical steppe communities in arid areas of the Loess Plateau, China

“…Zhao et al (2008) found that long-term exclusion of livestock grazing can significantly improve soil nutrient properties and soil organic carbon in grassland community of the Loess Plateau. Conversely, improvement of soil nutrient conditions in grassland can promote the growth of plant species and biomass accumulation, especially for palatable grasses which have greater competitive ability than unpalatable grasses (Gallego et al 2004). Wu et al (2009) found that nine-year exclusion of livestock grazing had negative consequences for biodiversity because it led to a reduction of plant density and species diversity in an alpine grassland community.…”