Do aeolian deposits and sand encroachment intensity shape patterns of vegetation diversity and plant functional traits in desert pavements?

Abstract

The effects of sand encroachment on composition, diversity, and functional patterns of vegetation in drylands are rarely studied, and yet addressing these aspects is important to deepen our understanding of the biodiversity conservation. This study aimed to investigate the effect of sand encroachment on plant functional biodiversity of desert pavements (gravel deserts) in the Sahara Desert of Algeria. Plants were sampled and analyzed in three desert pavements with different levels of sand encroachment (LSE) and quantity of aeolian deposits (low, LLSE; medium, MLSE; and high, HLSE). Within the sample-plot area (100 m²), density of every plant species was identified and total vegetation cover was determined. Plant taxonomic and functional diversity were analyzed and compared between LSE. Result showed that 19 plant species in desert pavements were classified into 18 genera and 13 families. Asteraceae and Poaceae were the most important families. The species Anabasis articulata (Forssk) Moq. characterized LLSE desert pavements with 11 species, whereas Thymelaea microphylla Coss. & Durieu ex Meisn. and Calobota saharae (C&D) Boatwr. & van Wyk were dominant species of desert pavements with MLSE (14 species) and HLSE (10 species), respectively. The highest values of species richness and biodiversity were recorded in desert pavements with MLSE, while low values of these ecological parameters were obtained in desert pavements with HLSE. Desert pavements with LLSE were characterized with the highest values of species abundances. Plant communities were dominated by chamaephytes, anemochorous, arido-active, and competitive stress-tolerant plants. The increase in LSE along the gradient from LLSE to HLSE induced significant changes in plant community variables including decreases in plant density, plant rarity, lifeform composition, morphological type, and aridity adaptation. Desert pavements with HLSE favor the degradation of vegetation and trigger biodiversity erosion.

Floristic Diversity of Zygophyllum album Communities Associated with Water Towers in the Algerian Sahara

“…Other major families of angiosperms (Poaceae, Amaranthaceae and Apocynaceae) are well represented in the study area. These families are also reported as the most frequent families in the Algerian Sahara [2,24,27,32,36,40,48]. In addition, Ozenda [4] underlined the importance of these families which proved to be the most frequent families in the Algerian flora.…”

“…In each site at Zygophyllum album, 2 to 4 phytoecological relevés were conducted using subjective sampling [34]. The relevés area is 100 m 2 (10 m x 10 m) chosen on the basis of studies of Saharan plant communities [30][31][32][35][36]. In each relevés, we listed all species present with their abundance-dominance coefficients [37].…”

“…The use of this plant in the form of crude extracts, infusions and plasters is a widespread practice in the treatment of many pathologies in Algeria [18]. The Saharan vegetation is currently well known on the floristic and ecological levels [4,2,20,[23][24][25][26][27][28][29][30][31][32][33]. Despite this, few studies have been reported on the ecology of Zygophyllum album communities in different Saharan habitats.…”