Aridity and Overgrazing Have Convergent Effects on Ecosystem Structure and Functioning in Patagonian Rangelands

Abstract

Over 65% of drylands are used for grazing of managed livestock. Understanding what drives grazing effects on the structure and functioning of rangelands is critical for achieving their sustainability. We studied a network of 239 sites across Patagonian rangelands (Argentina), which constitute one of the world's largest rangeland area. We aimed to (i) evaluate how aridity and grazing affect ecosystem structure and functioning and (ii) test the usefulness of the landscape function analysis (LFA) indices (stability, infiltration and nutrient cycling) as surrogates of soil functioning. Aridity decreased species richness and the cover of palatable grasses but increased the cover of palatable shrubs. Grazing pressure negatively impacted the cover of palatable grasses and species richness but did not affect the cover of shrubs. Aridity had direct and indirect negative relationships with the LFA indices. Grazing pressure had no direct effects on the LFA indices but had an indirect negative effect on them by affecting vegetation structure. The LFA indices were positively and negatively correlated with soil organic carbon and sand contents, respectively, suggesting that these indices are useful proxies of soil functional processes in Patagonian rangelands. Our findings indicate that aridity and overgrazing have convergent effects on the structure and functioning of ecosystems, as both promoted reductions in species richness, the cover of palatable grasses and soil functioning. Rangeland management activities should aim to enhance species richness and the cover of palatable grasses, as these actions could contribute to offset adverse effects of ongoing increases in aridity on drylands. Copyright © 2017 John Wiley & Sons, Ltd.

The impact of grazing on land degradation: A common problem with many driving forces

“…It increases the persistence of vegetation patches under prolonged droughts. Similar negative effects of overgrazing in dry environments were also highlighted by Juan J. Gaitán et al (—this issue) in Patagonian rangelands, Argentina.…”

Meat production and maintaining biodiversity: Grazing by traditional breeds and crossbred beef cattle in marshes and grasslands

“…Naturalness values decreased with increasing grazing intensity, which calls attention to the importance of setting and designing proper management intensities in rangelands. Even though in our case increasing grazing intensity did not lead to the severe degradation of grasslands, several studies identified overgrazing as a major cause of habitat degradation (Deák et al, ; Gaitán et al, ; Tóth et al, ).…”

“…This is probably caused by the trampling effect of the larger-sized crossbred beef cattle, which is higher on wet soil compared to dry soil (Warren, Nevill, Blackburn, & Garza, 1986 (Deák, Valkó, Tóthmérész, et al, 2014c), also leading to decreased moisture indicator values. In the face of climate change, the interaction of grazing-and climate-induced drought will act as an important threat for the conservation values of rangelands (Gaitán et al, 2018;Webb et al, 2017). An option for mitigating the negative effects of climate change could be to apply grazing of traditional cattle breeds in the sensitive marsh areas.…”

“…Due to the large body size of cattle, grazing intensity should be carefully chosen to prevent soil erosion (Salvati & Carlucci, ). Several studies found that high grazing intensity leads to land degradation, due to intensive trampling, nutrient input and excessive defoliation (Brinkert, Hölzel, Sidorova, & Kamp, ; Symeonakis, Karathanasis, Koukoulas, & Panagopoulos, ; Deák et al, ; Gaitán et al, ). Tölgyesi, Bátori, Erdős, Gallé, and Körmöczi () emphasized that grazing intensity should be harmonised with the specific habitat types and plant productivity.…”

Income diversification strategies among pastoralists in Central Asia: Findings from Kyrgyzstan

“…The reasons for declining pasture productivity are seemingly straightforward. Human-induced degradation has been attributed to over-grazing or other damaging land-use practices (Hilker et al 2014;Stevens et al 2016;Kairis et al 2015;Christianen et al 2014;Gaitán et al 2018). Often, the common property nature of pastures causes Garret Hardin's tragedy of commons (Hardin 1968), where multiple users compete for the resource.…”