Assessment of species diversity and state of Stipa tenacissima steppes

Abstract

North African steppes are subjected to extreme degradation resulting in the reduction of their surface, genetic erosion of resources, and decrease in biodiversity. Stipa tenacissima steppes, which constitute one of the most representative vegetation types in the driest areas of the Mediterranean basin, are continuously degrading. With the aim of contributing to a better knowledge of the floristic composition and diagnosing the state of degradation of these steppes, we conducted a phytoecological analysis of 10 S. tenacissima sites in Tunisia. Floristic inventory compiled a systematic list of 46 vascular plant species belonging to 43 genera and 26 families. Species richness ranged from 4 to 18 species per 900 m 2 . Total vegetation cover was moderate and fluctuated between 22.8% and 49.9%. Our results revealed also a decreasing trend in species richness with increasing elevation (ρ = -0.585). Indeed, species richness was negatively correlated with slope (ρ = -0.19) and positively correlated with sand content (ρ = 0.262). Biological types were dominated by chamaephytes; this chamaephytization is due to the phenomenon of aridization and overgrazing. Moreover, the low species cover and the appearance of nonpalatable species highlighted the vulnerability of these steppes to degradation.

Effect of silvicultural treatment of individual selection on the horizontal structure of a pine-oak forest in northern Mexico

“…Santana et al (2014) attributed the differentiation of groups to the environmental heterogeneity present in a mountain cloud forest analyzed in the Transversal Volcanic System of Michoacan in Mexico. Instead, Ghiloufi et al (2015) concluded that the absence or presence, in terms of species composition, presents inequalities due to the recruitment of new sets of species. Another identified factor that has led communities towards a differentiated assemblage of species is anthropogenic, Williams-Linera (2002) indicated that human activities exert an important influence on the type and degree of fragmentation of ecosystems, reflected in the inequality and turnover of species.…”

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

“…Over the last three decades, steppic rangelands have suffered from rapid degradation [Slimani et al, 2010] by climatic factors [Bensmira et al, 2015] and human activities such as overgrazing. The impact of overgrazing is reflected by the rarefaction and even disappearance of some useful plant species with high forage value, the abundance and even dominance of some less palatable species, and the development of unpalatable species [Ghiloufi et al, 2015]. However, the area of grazing rangeland has decreased at the expense of marginal crops [Demnati et al, 2017].…”