Livestock grazing‐induced large‐scale biotic homogenization in arid Mediterranean steppe rangelands

Abstract

Despite many studies that have explored the effect of livestock grazing on plant communities, the response of species composition and diversity to livestock grazing in arid rangelands remains ambiguous. This study examined the effects of livestock grazing on plant communities in arid steppe rangelands of North Africa. Plant diversity of annual species, perennial species, and all species combined were measured and compared between grazed and grazing-excluded areas. We also examined the relative importance of species turnover and community nestedness. Moreover, the effects of livestock grazing on beta diversity at local among transects and landscape among sites scales were examined using the multiplicative diversity partitioning.Results revealed that livestock grazing significantly decreased the alpha diversity of all species combined and the diversity of annual plants. Livestock grazing induced a shift in plant community composition where most species composition variation (74%) was due to infrequent species replacement 'turnover' between the two management types rather than nestedness (26%). Results revealed also that among transects, beta diversity was higher in grazed steppes than in grazing-excluded steppes. Whereas, among sites, beta diversity was lower in grazed steppes compared to grazing-excluded steppes. These findings suggest that livestock grazing in arid steppe rangelands increases the variation in plant species composition at a local spatial scale and engenders vegetation homogeneity at a landscape spatial scale. Therefore, the implementation of appropriate management practices such as short-term grazing exclusion is mandatory to prevent these ecosystems from large-scale biotic homogenization.

Botanical Diversity of Arid Steppe in South East of Algeria (Biskra)

“…In arid steppic rangelands, severe climatic conditions promoted the existence of a specialized plant community [Quezel and Santa, 1963;Slimani et al, 2010;Fatmi et al, 2020;Merdas et al, 2021].…”

On the early warning signal of degradation in drylands: Patches or plants?

“…These species generally present resistance or avoidance mechanisms as a defence against herbivory and can maintain or even increase their abundance under high grazing pressure, which has been well documented in many drylands (e.g. Aguiar et al, 1996;Bertiller & Bisigato, 1998;Bestelmeyer et al, 2004;Fensham et al, 2010;Gatica et al, 2020;Merdas et al, 2021;Van Auken, 2000;Vogel et al, 2022). Third, the model considers that the classification of forage species depends on the dominant herbivore species.…”

Short-term land degradation driven by livestock grazing does not affect soil properties in semiarid steppe rangelands

“…Climate changes combined with overgrazing and an increase in the number of livestock are the main sources of steppe vegetation degradation, causing land desertification and serious decline in steppe areas of Macrochloa tenacissima (L.) Kunth (syn. Stipa tenacissima L.) named in Arabic Alfa or Halfa (Macheroum and Kadik, 2015;Merdas et al, 2021). Free grazing with a high number of animals adversely affects the natural resources of these rangelands already weakened by climatic hazards, including severe droughts and intense heatwave events (Nedjraoui and Bédrani, 2008;Belala et al, 2018;Kouba et al, 2021).…”

“…Steppe degradation was amplified and aggravated by the anarchic clearing and plowing combined with inadequate development of steppe areas and poor grazing management by farmers and pastoralists in the context of aids granted by the state for exploitation of the steppes (Hadeid, 2006). These degradation conditions favor the establishment of plants of low forage value that do not meet the needs of the animal load, but rather this accentuates the pressure of overgrazing on non-degraded areas (Hasnaoui and Bouazza, 2015;Merdas et al, 2021).…”

“…In steppe ecosystems, soil physicochemical properties play a key role in soil-vegetation relationships because the distribution of the vegetation is closely linked to the characteristics of the abiotic environment, especially the edaphic and climatic parameters (Chenchouni, 2017;Bezzalla et al, 2019) and also biotic interactions (Bansal and Sheley, 2016;Merdas et al, 2021) including livestock grazing (Liu et al, 2020), which also has various feedback influences on the soil itself (Haynes and Williams, 1992;Dormaar and Willms, 1998;Yong-Zhong et al, 2005;Cheng et al, 2016;Ye et al, 2016). Several studies have extensively investigated environmental-related problems of North African steppes in terms of soil erosion, desertification, droughts, plant community diversity, and vegetation cover dynamics in relation to livestock grazing and various land managements (Aidoud and Touffet, 1996;Benabderramane and Chenchouni, 2010;Belala et al, 2018).…”