Statistical Modeling of Biodiversity and Ecological Structure of the Caspian Coastal Flora (Azerbaijan)
Elshad Gurbanov1 
, Humira Huseynova1*
Abstract. The Caspian coastal zone of Azerbaijan presents pronounced environmental gradients in soil moisture and salinity, making it a valuable model system for investigating plant community assembly in brackish transitional habitats. This study examined three hypotheses: (i) soil moisture is the primary structuring force of plant community composition and diversity; (ii) salinity acts as a secondary stress filter reducing community evenness; and (iii) anthropogenic disturbance modulates both effects. Between 2023 and 2025, a total of 520 stratified random geobotanical relevés (100 m² plots) were established across six botanical-geographic districts using the Braun-Blanquet approach. Volumetric soil moisture and electrical conductivity were recorded at peak dry season, while anthropogenic pressure was quantified through infrastructure proximity and remote-sensing-derived land-use intensity indices. The sampled flora encompassed 1,054 vascular plant species.
Community composition varied significantly across districts (χ² = 214.7, p < 0.001). Shannon diversity declined from humid (H′ = 1.41) to saline-arid zones (H′ = 1.19; ANOVA: F₄,₅₁₅ = 26.3, p < 0.001, η² = 0.17). PERMANOVA indicated that measured environmental variables collectively explained 42% of compositional dissimilarity. Ordination analyses identified moisture as the dominant gradient (PC1: 35.8%) and salinity-disturbance as secondary (PC2: 22.4%). Variance partitioning attributed 28% to pure environmental drivers and 12% to shared fractions, while approximately 58% remained unexplained, reflecting contributions from dispersal limitation, biotic interactions, and microsite heterogeneity. Generalised linear models confirmed significant negative effects of salinity (β = −0.20) and disturbance (β = −0.14) on diversity, alongside a significant moisture × salinity interaction. These findings establish a quantitative ecological baseline for conservation management across the Azerbaijani Caspian coast under ongoing sea-level fluctuation and increasing land-use pressure.
Keywords: Caspian coastal flora, environmental filtering, stress‑gradient hypothesis, soil salinity, community assembly, multi‑seasonal variability, anthropogenic disturbance, remote sensing