Populations of Hippophae rhamnoides as an indicator of tugai forest degradation in the Zarafshan River valley

Tugai forests of the Zarafshan River valley are highly vulnerable ecosystems experiencing increasing anthropogenic pressure and hydrological alterations. Assessing their degradation requires reliable biological indicators. This study aims to evaluate coenopopulations of Hippophae rhamnoides L. as an indicator of tugai ecosystem transformation. Field investigations were conducted in five coenopopulations within the Zarafshan National Nature Park. The study included analysis of ontogenetic structure, population density, morphological variability, and vitality indices based on standardized geobotanical and population-biological methods. All studied coenopopulations were classified as normal but incomplete. Under anthropogenic disturbance (grazing, fires, and fruit harvesting), left-skewed ontogenetic spectra dominated, characterized by a prevalence of young generative individuals and reduced regeneration. A fire-affected coenopopulation exhibited a right-skewed spectrum with accumulation of middle-aged generative and senile individuals and absence of pre-generative stages, indicating severe degradation. In less disturbed habitats. A centered ontogenetic spectrum was observed, reflecting relatively stable population conditions. Population maintenance was primarily supported by vegetative reproduction. while seed regeneration remained low. Morphological traits showed moderate variability (CV = 2.3–37.2%), indicating limited adaptive plasticity. Vitality analysis revealed both thriving and depressed coenopopulations depending on habitat conditions. The results demonstrate high sensitivity of Hippophae rhamnoides to environmental changes and confirm its suitability as an indicator of tugai forest degradation. Reduced vitality and weak regeneration highlight the need for urgent conservation and restoration measures in the Zarafshan River valley.