GEOLOGICAL IMPACT ON PLANT COMMUNITY STRUCTURE AND DIVERSITY

Abstract

Geological factors are fundamental determinants of plant community structure and diversity, shaping not only physical terrain but also the chemical and physical properties of the soil. While climate and biotic interactions are crucial, geology often acts as a first-order filter, establishing baseline conditions for other ecological processes. This study investigated the profound influence of geological heterogeneity on soil physicochemical properties and, consequently, plant community composition and diversity within a region encompassing diverse bedrock types (igneous, sedimentary, metamorphic). We systematically collected high-resolution geological data, comprehensive soil samples (analyzing pH, nutrient content, texture, and trace elements), and detailed plant community data (species identification, cover, abundance). Our results demonstrate significant variations in soil properties directly linked to underlying geological units, such as higher pH and calcium in limestone-derived soils versus low Ca:Mg ratios and high nickel in serpentine soils. These edaphic differences imposed strong selective forces on plant species, leading to distinct community structures and biodiversity levels. Plant diversity, including species richness and Shannon-Wiener diversity, was significantly lower on serpentine substrates compared to limestone. Non-metric Multidimensional Scaling (NMDS) ordination clearly separated plant communities based on their geology, with Permutational Multivariate Analysis of Variance (PERMANOVA) confirming geology as a significant driver, accounting for 38.5% of total variation. Redundancy Analysis (RDA) identified soil pH, Ca:Mg ratio, and nickel concentration as key environmental factors correlated with community shifts. Variance partitioning analysis further emphasized the pervasive impact of geology, both directly and indirectly through soil attributes, in shaping plant community composition and diversity. These findings underscore the critical importance of incorporating geological context into ecological research, conservation strategies, and natural resource management, particularly in the face of increasing anthropogenic stress and climate change.