Vegetation traits are accurate indicators of how do plants beat the heat in drylands: Diversity and functional traits of vegetation associated with water towers in the Sahara Desert

摘要

Water is the key determinant factor of ecosystem balance, especially in hot desert regions facing multiple climatic and edaphic constraints. In the Sahara Desert, vegetation associated to man-made mesic environments such as open-air irrigation channels and oases is little studied. In order to understand the vegetation-water relationship in xeric environments, the present study focused on estimating diversity and determining functional traits of plant communities established around water points developed near water towers in the region of Adrar (Sahara Desert of Algeria). Based on data collected from 31 phytoecological releves, spontaneous vegetation was analyzed using diversity parameters (viz. species richness, diversity, richness estimation and similarity), and plant functional traits PET' (viz. life forms, morphological, phytogeographical and dispersal types, Grime's and Noy-Meir's strategies). A total of 4695 individuals belonging to 53 plant species and 23 families were collected. Rarefaction and extrapolation curves applied for all the surveys carried out indicated that the estimated species richness is projected to be 77.2 +/- 10 species from 31 survey plots and it is predicted to reach up to 116 +/- 30 species from 200 survey plots, which represents an increase of 119% of the observed species richness. According to the real spectrum (abundance-based data) of PFT, plant species are mainly hemicryptophytes (54.12%) and arid-actives (69.97%) that adopt various dispersal strategies including anemochores (57.68%) and barochores (36.68%). Grime's strategies showed the predominance of competitive and stress-tolerant species (52.76%). The phytogeographical analysis revealed the dominance in the strict sense of the Tropical-Mediterranean-Saharo-Arabian element (36.59%) which adapts well to the Saharan climate. This study showed the role of water in shaping the functional characteristics of vegetation in hyper-arid regions. The functional diversity of Saharan vegetation reflects species strategies for a better exploitation of the water and guaranteeing their coexistence in hyper-arid environments.