Slope Aspects and Elevation Influenced Herbaceous Diversity and Soil Characteristics in Tropical Forests of Indian Desert

Abstract

Aim: Understanding the interactive effects of aspects and elevation on soil properties and vegetation diversity in hill forests of the desert environment is essential for devising strategies to restore such degraded hills.
 Place and Duration: Observations were recorded from September to October months of both 2017 and 2018 in a hill forest area in Thar Desert of Rajasthan, India.
 Methodology: Three-hundred-twenty plots of 1 m2 (clustered at sixty-four positions based on eight slope aspects and eight elevations) were studied for herbaceous diversity and soil properties by sorting vegetation to species level and soil sampling in each plot. Community population (P), height, soil water content (SWC), pH and organic carbon (SOC) were measured and species-richness (R), Shannon-Weiner diversity (Hꞌ), dominance (D) and evenness (J') were calculated.
 Results: Out of 174 species recorded from 34 families and 122 genera, 163 species showed IVI <5. Highest number of species (48) were from family Poaceae. Soil pH, SWC, SOC, P and height were greater in 2017, whereas R, Hꞌ and Jꞌ were greater in 2018. Soil pH, vegetation height and D were lowest in northeast and highest (1.04-1.54-fold) in west to southeast. SOC, SWC, R and J' were 1.16-2.35-fold greater in northeast than south aspect. P, height and H′ showed a reverse trend with 1.15-1.53-fold variation. SOC, height, R and H' increased by 1.30-2.35-fold with an increase in elevation from <230m to >600m, whereas D and pH showed a decreasing trend. The highest values of SWC, P and Jꞌ were in 800-900m, 700-800m and 600-700m respectively. Though varied with aspects, <230m area was dominated by xeric species, middle by Aristida adscensionis and higher ones by Apluda mutica/Heteropogon contortus.
 Conclusion: Altitude had stronger impact on all variables except SWC, which was influenced strongly by aspects making southern slopes drier than the northern slopes and influenced species structure and composition. Such areas require effective conservation, but aspect and elevation should be given due importance in devising restoration strategies for efficient management of biodiversity and mitigating climate change.