Grazing represents the most extensive use of land worldwide. Yet its impacts on ecosystem services remain uncertain because pervasive interactions between grazing pressure, climate, soil properties, and biodiversity may occur but have never been addressed simultaneously. Using a standardized survey at 98 sites across six continents, we show that interactions between grazing pressure, climate, soil, and biodiversity are critical to explain the delivery of fundamental ecosystem services across drylands worldwide. Increasing grazing pressure reduced ecosystem service delivery in warmer and species-poor drylands, whereas positive effects of grazing were observed in colder and species-rich areas. Considering interactions between grazing and local abiotic and biotic factors is key for understanding the fate of dryland ecosystems under climate change and increasing human pressure.

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Purpose The purpose of this paper is to illustrate the benefits of reintroducing traditional grazing systems practices for improving arid rangelands. Grazing is the most extensive land use in southern Tunisia, but the rangelands have suffered many decades of severe degradation due to profound socioeconomic changes and the emergence of an agro-pastoral society in place of the former pastoral one. Traditional grazing systems (gdel and herd mobility), which had historically allowed for grazing deferment and control of grazing livestock were abandoned. Yet grazing management strategies are important tools to sustain integrated livestock rangeland production systems in dry areas in the face of ongoing climate change and human pressure. Design/methodology/approach This study assesses the revival of traditional best practices of rangeland resting in a representative community. Total plant cover, species composition, flora richness and range production were determined in six rangeland sites subjected respectively to one, two and three years of rest; one and two years of light grazing after rest; and free grazing (control). Findings Results showed that dry rangelands keep their resilience to the negative effects of climate change once human pressure is controlled. A maximum of two years of rest is enough to sustainably manage the rangelands in southern Tunisia, as this protection showed considerable and positive effects on the parameters scored. Originality/value The revival of the traditional best practices under new arrangements adapted to current biophysical and socioeconomic conditions would be an excellent tool to mitigate the negative effects of frequent droughts and reduce the animal feed costs that poor farmers face.

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The restoration technique importance resides on the assessment of its impact on biodiversity. This assessment is possible by the use of some environmental indicators extracted from a diachronic study of land cover changes in protected areas. Our study is

Institut des régions arides (IRA) Laboratoire d'écologie pastorale 4119 Médenine Tunisie Tirés à part : M. Neffati RésuméLa désertification, qui ne cesse de s'aggraver, est devenue depuis quelques décennies le principal problème environnemental en Tunisie méridionale. Soumises à une aridité climatique et édaphique en plus d'une surexploitation de leurs ressources, les steppes de cette région sont considérées comme étant très dégradées. Le présent travail se propose de quantifier les effets de la sécheresse et de l'action anthropozoïque sur le couvert végétal naturel au niveau. Quelques attributs structuraux ont été retenus pour décrire les variations saisonnières (automne 2005 et printemps 2006) de ces écosystèmes sous l'effet de ces contraintes. Les principaux résultats obtenus montrent que les relations entre les conditions édaphoclimatiques et le couvert végétal sont fortement influencées par la pression anthropozoïque et la topographie. Le substrat de la station 1 garantit une meilleure résistance aux conditions d'aridité que les autres. La topographie ralentit les effets de la sécheresse et assure une meilleure résilience à ces écosystèmes. Abstract Seasonal variation of some structural attributes of the Matmata Mountains ecosystems in southern Tunisia under the effect of drought and anthropozoic actionIn southern Tunisia, over the past few decades desertification has become the main environmental problem. The steppes of this region, subjected to severe and irrational exploitation for a long period in addition to climate and soil aridity, are highly degraded. This study aims at quantifying the effects of drought and topography on the natural plant cover of the Matmata Mountains in southern Tunisia. Some structural attributes have been assessed in order to describe the evolution of plant communities under these constraints. The main results show that relationships between soil, climate conditions and plant cover are strongly influenced by topography and human activities. the gypsum substratum shows a better resistance to arid conditions than the calcareous one. The Northern exposition manifests the best resilience in confronting these ecosystems.

This is the final version of the article that is published ahead of the print and online issue Sustainable rangeland management in arid areas can contribute to the mitigation of climate change and rising atmospheric carbon dioxide concentrations, because they store considerable amounts of carbon both in the aboveground vegetation and in the soils (Derner and Schuman 2007;Yang et al. 2017). In general, plant biomass of rangelands is relatively low at approximately 2-6 kg m −2 , compared with other terrestrial ecosystems reaching 10-18 kg m −2 (Ruijun et al. 2010), but their large area offers significant potential for carbon sequestration (Chen et al. 2009). Dryland ecosystems have a sequestration potential of approximately 1 billion tons of carbon per year, accounting for more than 12% of global anthropogenic greenhouse gases emissions (Lal 2004). Some studies indicate that 59% of total carbon storage in Africa is in arid areas (Campbell et al. 2008; UNEP 2008). In these regions, where pastoral activities are dominant, most of the sequestered carbon is stored underground, and is therefore relatively stable (FAO 2002). There is also a substantial amount of aboveground carbon stored in trees, bushes, shrubs and grasses, which are not grazed or are only moderately disturbed by grazing (IPCC 2007; Vashum and Jayakumar 2012). However, it has been suggested that, under current land use management, overgrazing leads to loss of carbon stocks (Tessema et al. 2011). Many rangeland management techniques, such as rehabilitation and grazing enclosures, aim to increase forage production and to consolidate the carbon sequestration potential both in soils and in aboveground vegetation (Homann et al. 2008). National parks and other protected areas have been established to protect biodiversity and maintain ecological stability through restriction of livestock grazing and other human interventions. According to Campbell et al. (2008), 15.2% of global carbon stock is stored within protected areas, which cover 12.2% of total land area, highlighting the importance of protected areas in climate change mitigation.Long-term protection of such dryland areas increases spatial heterogeneity and vegetation cover and leads to the development of new vegetation units (Tarhouni et al. 2014). This management technique significantly improves aboveground productivity of shrubby plants in

Resting or grazing exclusion is an effective practice widely adopted to restore degraded, arid rangelands. To understand its effect on plant diversity, we studied Hill’s diversity indices during two growing seasons (2017–2019). The experiment consisted of a three-level factorial design with four plant communities subjected to different resting durations (one, two, and three years) compared to continuously grazed areas (control). The results showed that rainfall plays an important role in arid rangeland restoration. Under favorable conditions, one-year grazing exclusion considerably enhanced species richness and evenness diversity compared to longer resting durations under dry to average rainfall conditions. The decision to how long livestock grazing exclusion would last should not be decided upfront as it depends on the climatic and the site-specific conditions. The findings of this study will have vital management implications for development agencies. Knowing that short grazing exclusion with adequate rainfall amount and distribution could be enough and offers a cost-effective technical option to ensure the sustainable restoration of arid rangeland. This flexible grazing management would also be more acceptable by the pastoral communities. Longer resting periods could have detrimental effects on arid rangeland vegetation, in addition to adding more pressure on the remaining rangeland areas open to grazing.