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Abstract
Cenolophium denudatum (Hornem.) Tutin is a perennial herb of the family Apiaceae associated mainly with moist meadow and floodplain habitats. In Kazakhstan, the species occurs near the peripheral part of its geographical range; therefore, studying its population organization is important for understanding mechanisms of population persistence and developing conservation measures. The aim of the present study was to assess the population and ecological characteristics of C. denudatum in Central Kazakhstan and to determine relationships between habitat moisture, spatial and ontogenetic population structure, and reproductive parameters. Field investigations were conducted during 2023–2025 within Karkaraly State National Nature Park. Population parameters were assessed on permanent 10×10 m plots using randomly placed 1×1 m quadrats. A total of 245 individuals were examined. The spatial distribution of plants was predominantly aggregated. The highest population density, 1.4–1.6 individuals/m², was recorded in relatively moist habitats, whereas density decreased to 0.6–0.8 individuals/m² under meadow-steppe conditions. The coefficient of variation in density ranged from 28 to 35%. In floodplain habitats, pregenerative individuals accounted for up to 52% of the population and the age-stability index reached 1.21. With decreasing habitat moisture, this index declined to 0.94 in dry meadows and 0.73 in meadow-steppe communities. The proportion of generative plants increased to 50% under drier conditions, accompanied by a reduction in juvenile fractions. Generative plants reached an average height of 110–125 cm, developed 6–8 umbels and produced 210–260 fruits per plant, while the reproductive coefficient ranged from 0.38 to 0.50. The results demonstrate that the hydrological regime is a major environmental factor determining the demographic structure and stability of C. denudatum populations.