Seasonal Changes Modulate the Rhizosphere of Desert Plant Species

Arid and semi-arid ecosystems are categorized as having degraded soils due to the limited availability of water and nutrients. The perennial shrubs in these regions have developed different ecological and physiological adaptations to cope with harsh conditions. The plant species vary in the chemical profile of their root exudates, which can induce variability in the microbial community in the rhizosphere. The present research has been conducted (i) to investigate the variation in composition, diversity, and structure of rhizosphere's bacterial community of desert plants; (ii) to identify plant-specific effects on the rhizosphere microbial community structure; and (iii) to determine the influence of soil moisture on the rhizosphere's microbial community and soil biological properties under stressful conditions. Ten desert plant species from the Cholistan desert were selected as test specimens. Bacterial communities from the rhizosphere of 10 plants of each species were explored. Soil samples were collected during monsoon (June-August) and dry months (March-May). Microbial community structure analyses were carried out through 16S rRNA sequencing by targeting V3 and V4 regions. Among tested plant species, the rhizosphere of Leptadenia pyrotechnica (S6 vs. S16), Aerva javanica (Burm. f.) Juss. ex Schult (S9 vs. S19), and Vachellia jacquemontii (Benth.) (S10 vs. S20) had greater microbial diversity in both seasons. Higher levels of microbial communities were found during monsoon season. Furthermore, Gammaproteobacteria were abundant in the rhizospheres of all studied plants during the monsoon season. In contrast, the rhizosphere was abundant with unidentified_Actinobacteria during the dry season. The rhizospheric soil was further analyzed for biological properties. The maximum microbial biomass carbon (165 mg kg(-1)) and microbial biomass nitrogen (6.7 mg kg(-1)) were found in the rhizosphere of Vachellia jacquemontii (Benth.) Benth during monsoon season. However, a minimum of microbial biomass carbon (119 mg kg(-1)) and microbial biomass nitrogen (4.2 mg kg(-1)) were found in the rhizosphere of Cleome pallida Kotschy during dry seasons. The diversified microbial community structure and biological properties enable desert plants to cope with adverse climate conditions.