Impact of grazing ban of olive plots on floristic richness and diversity, and plant biomass in the Zloul Valley (Morocco)

Khalid BENARCHID
Laboratoire Eco-Conception, Energie, Environnement et Innovation. Faculté des Sciences et Techniques, Université Hassan 1er, Settat– Maroc. Corresponding author: k.benarchid@uhp.ac.ma
Mohammed KHATORI
Laboratoire Eco-Conception, Energie, Environnement et Innovation. Faculté des Sciences et Techniques, Université Hassan 1er, Settat– Maroc
Said HILALI
Laboratoire Eco-Conception, Energie, Environnement et Innovation. Faculté des Sciences et Techniques, Université Hassan 1er, Settat– Maroc

Abstract

In the past half-century, the forest of Zloul Valley has been severely deforested. For forty years, olive trees have been planted on deforested land, and now it is close to 5000 hectares. Therefore, to protect the olive culture, large-scale grazing in the valley is prohibited. The purpose of this study is to determine the impact of the grazing ban on floristic richness and diversity and above-ground biomass (herbaceous and shrub strata). Floristic research has been conducted on 50 surveys, of which 25 were conducted in protected olive fields and 25 were conducted in unprotected areas

The grazing ban had a positive effect on above-ground biomass and species richness. Compared with those produced in unprotected areas, the protected olive plots produced significantly higher above-ground biomass. The floristic analysis revealed also that the prohibition of grazing resulted in a higher species richness compared to that of the unprotected zone with respectively 185 and 119 species. However, it led to a decline in plant diversity, the Shannon-Weaver index values were 4.81 and 4.52, respectively. Furthermore, the floristic composition of the grazing ban olive plots has been more unbalanced compared with the unprotected areas, with equitability indices of 0.59 and 0.68, and perturbation indices of 76.8 and 63%, respectively.

The long-standing ban on the graze seems to be mixed. Despite its positive effect on the species richness and above-ground biomass, it led to low floristic diversity and a perturbated floristic composition.

Keywords: Biodiversity; Floristic diversity; Grazing Ban; Restoration; Therophytisation.