Regional Variation in Plant Community Composition and Soil Properties of Alcea nudiflora Habitats Along an Elevational Gradient in the Trans-Ili Alatau, Kazakhstan

Abstract

Wild plant populations in mountain ecosystems often depend on specific combinations of soil, vegetation and microsite conditions. Alcea nudiflora (Lindl.) Boiss. is a poorly studied Malvaceae species in Central Asia, and its population structure across different soil and vegetation conditions in the Trans-Ili Alatau remains insufficiently documented. We assessed three natural populations of A. nudiflora along an elevational gradient in the Trans-Ili Alatau, Kazakhstan: P1 at 900 m a.s.l., P2 at 1438 m a.s.l. and P3 at 1620 m a.s.l. Floristic composition, vegetation structure, ontogenetic stages and soil physicochemical properties were analysed using field surveys, 10 × 10 m plots, soil descriptions, laboratory analyses and exploratory ordination. P1 occurred in relatively open meadow–shrub vegetation and showed the strongest coenotic expression of A. nudiflora, with 62 individuals recorded within the 100 m2 vegetation plot and a broad representation of major ontogenetic stages. In P2, A. nudiflora remained a regular component of shrub–meadow and forest-edge vegetation, whereas in P3, the species occurred sparsely and was restricted to meadow openings, forest-edge gaps, and local microsites. Surface soil properties varied among habitats. In the upper horizon, P1 had 3.67% humus, 95.2 mg kg−1 readily hydrolysable N, 36.0 mg kg−1 available P2O5, 610 mg kg−1 available K2O, pH 8.41 and 4.28% CO2; P2 had 3.72% humus, 39.2 mg kg−1 readily hydrolysable N, 44.8 mg kg−1 available P2O5, 450 mg kg−1 available K2O, pH 8.23 and 0.54% CO2. PCA explained 37.1%, 33.8% and 9.4% of variance on PC1–PC3, summarizing gradients of nutrients, texture, carbonates and alkalinity. The results indicate that population status is associated with surface soil conditions, vegetation structure and microsite availability rather than elevation alone.