Relationships alpha plant species diversity and environmental factors in oak forests in Sultandağı district (Afyonkarahisar)

This thesis quantifies alpha‐level plant diversity in oak (Quercus sp.) forests of the Sultandağı district (Afyonkarahisar, Türkiye) and elucidates its relationships with major environmental factors. Forty primary plots (100 × 100 m) were established across the full environmental gradient within the Sultandağı Forest Administration; each contained two subplots (20 × 20 m). Braun–Blanquet cover values recorded in the field were converted to the Westhoff & Van Der Maarel and Fontaine scales to calculate species richness (S), Shannon–Wiener (H′), Simpson (1 – λ) and Pielou evenness indices (E). The climate data downloaded from the WorldClim 2.1 database, the 1:250 000 geological maps, and the other topographic variables were processed in a GIS environment and clipped to the exact boundaries of the study area. The floristic inventory documented 326 taxa (32 families, 192 genera), including 40 Turkish endemics. Species richness ranged from 12 to 58 (x̄ = 26.2). On the Westhoff–Van Der Maarel scale, H′ varied between 2.34 and 3.94 and Simpson's 1 – λ between 0.88 and 0.98; on the Fontaine scale, H′ ranged from 1.19 to 3.56 and Simpson's 1 – λ from 0.42 to 0.96. Pearson correlations revealed negative associations of alpha diversity with elevation (r = –0.22) and annual precipitation (r = –0.29) and positive associations with solar radiation (r = 0.24) and mean annual temperature (r = 0.24). A regression tree model (R² train = 0.226; R² test = 0.204) identified terrain ruggedness and annual precipitation as the strongest predictors. Maximum diversity occurred in micro-topographic sites with precipitation < 558 mm and high ruggedness (> 66.373) while annual precipitation exceeding the 558 mm threshold. These findings confirm that the Sultandağı oak forests constitute ecologically significant ecosystems in terms of floristic diversity and endemism. Although alpha diversity exhibits only moderate variation among oak stand types, beta diversity (dissimilarity) analyses indicate appreciable compositional turnover across these stand types, underscoring the importance of habitat heterogeneity for conservation planning.