Contrasting Soil Conditions and Divergent NDVI Dynamics Under Long-Term Climate Warming Across Acanthophyllum gypsophiloides (Caryophyllaceae) Habitats in Central Asia

The rare Central Asian plant Acanthophyllum gypsophiloides occurs in environmentally contrasting mountain and foothill localities of the Syrdarya Karatau. We evaluated whether three populations—Sayasu, Kuyik, and Birlik—are associated with contrasting profile-level edaphic conditions within a shared regional climatic background, and whether these locality-level contrasts are accompanied by differences in population demographic configuration and local vegetation greenness. The three sampled soil profiles differed markedly in their physicochemical characteristics. Sayasu and Kuyik were dominated by coarse-textured material with low fine-fraction contents, whereas the Birlik profile contained a substantially greater < 0.01 mm fraction but showed the lowest humus and total macronutrient concentrations, the highest pH (8.55–8.69), and markedly greater carbonate content (CO2, 4.91–7.04%). Both WorldClim and CHELSA indicated long-term warming during 1980–2019, although the estimated rates differed between products, whereas precipitation patterns were more dataset-dependent. Population density and ontogenetic structure also differed among the three localities. Sentinel-2 NDVI values extracted at the population locations were 46.3%, 59.5%, and 61.0% lower in 2025 than the corresponding 2016 values at Sayasu, Kuyik, and Birlik, respectively; these observations represent pixel-scale vegetation greenness rather than species-specific population performance. Overall, the three localities were differentiated primarily by contrasting sampled soil-profile conditions within a common regional warming context, while demographic structure and local vegetation greenness provided complementary ecological evidence. These co-occurring patterns identify locality-specific environmental contrasts relevant to conservation monitoring but do not establish causal relationships among soil conditions, climate, vegetation greenness, and population dynamics.