Variation in demographic traits and growth patterns of three dioecious Juniperus taxa on the scree-sloped mountains of the Hindu Kush
摘要
Dioecious Juniperus taxa in the Hindu Kush mountains are facing threats from human activity and climate change, emphasizing the need for demographic data to assess taxa- and sex-specific microhabitat responses. We investigated dendrometric traits, the sex ratio, sex-specific growth (cm · year⁻1), and reproductive effort of three Juniperus taxa along an elevational gradient (2,400–3,500 m a.s.l.). Vegetation data from 30 stands were analysed, with the sex ratio determined by counting male and female individuals, growth rates assessed through dendrochronology, and reproductive effort quantified by counting cones and viable seeds. J. excelsa showed significantly greater diameter (> 24.3 cm), height (> 5.24 m), and age (> 132 years) than the other Juniperus taxa (P < 0.02), whereas J. semiglobosa had the highest growth (> 0.18), especially in males (0.20, P = 0.04). The sex ratio was relatively balanced in J. excelsa (0.8) and J. semiglobosa (0.87), while a more skewed sex ratio (0.3) was recorded in J. excelsa subsp. polycarpos, which also occupied a narrow elevational range (2,628–2,929 m). By contrast, J. semiglobosa dominated broader and higher elevations (2,546–3,450 m), reflecting its greater ecological amplitude. Cone production in J. semiglobosa and J. excelsa was moderate, whereas it was significantly lower in J. excelsa subsp. polycarpos. Overall, seed viability was low (26–34%), and both cone production and seed viability increased with elevation. Environmental variables, including elevation, soil pH, texture, nutrients and hydraulic properties, were significantly associated with species traits. These findings highlight sex- and taxa-specific adaptations to microhabitat variation, informing targeted conservation strategies for sustainable management.