Vegetation diversity and composition in relation to different grazing intensity levels in an arid environment in Jordan

Abstract

Grazing practices fundamentally shape plant community composition and biodiversity worldwide, more importantly in water-limited environments. This study aimed to investigate plant community composition, species distribution of occurrence and diversity indices in an arid rangeland under different grazing intensities. The quadrat method was used to select 90 × 1 m² quadrats in heavy-grazing, light-grazing and ungrazed sites. Plant species frequency, relative frequency, abundance, relative abundance and density, as well as species richness, evenness, Shannon diversity index and Simpson’s diversity index were calculated. A total of 46 plant species belonging to 17 families were recorded. The Asteraceæ family was represented with the highest frequency (28%). Overall in the study area, around 95%, 70% and 40% of recorded plant families existed in light-grazing, ungrazed and heavy-grazing sites, respectively. The species richness of identified plants in light-grazing and ungrazed sites was 300% and 200% greater, respectively, than in the heavy-grazing sites. Around 85% of existing plants in heavy-grazing sites were therophyte plants. The species frequency, abundance, density and diversity indices were higher in light-grazing sites compared to those under heavy grazing, which indicates a more diverse, heterogenous and balanced plant community in the light-grazing site. Plant communities in light-grazing and ungrazed sites were similar, except for higher species frequency, density and evenness in light-grazing sites. This suggests that light-grazing intensities in the arid rangelands of Jordan enhance plant diversity more than grazing exclusion, which encourages decision-makers and environmentalists to implement regulations prohibiting intensive grazing in the arid rangelands of Jordan.

Keywords:

• exclude grazing
• overgrazing
• plant diversity indices
• heavy grazing
• rangeland