Population structure, regeneration potential and leaf morphological traits of Rhododendron campanulatum D.Don along an altitudinal gradient in Western Himalaya

The vegetation of the alpine treeline ecotone is among the most vulnerable and sensitive to global climate change. Treeline species respond to global warming through changes in their population structure, regeneration, plant functional traits and shift in their habitat. This study was carried out on Rhododendron campanulatum D.Don, a typical plant species of the Himalayan treeline ecotone, to understand the variation in population structure, regeneration potential and leaf morphological traits along the altitudinal gradient (3100-3550 m.a.s.l.) in Tungnath, Western Himalaya. We reported the higher seedling (3480 stem ha(-1)) and juvenile (2210 stem ha(-1)) density of the species above the treeline at 3400 m.a.s.l. This clearly shows a good regeneration status and indicates the upward shift of the species. Leaf morphological traits such as length, width, and the specific leaf area decreased with an increase in elevation but leaf thickness increased with an increase in elevation. SLA was higher (71.14 cm(2)/g; p < 0.001) at 3100 m.a.s.l. located below the treeline than 3550 m.a.s.l. (60.08 cm(2)/g; p < 0.001)) located above the treeline. The results indicate that the species has large flexibility in the morphological performance and its high level of plasticity in morphological traits may explain its wider niche and ability to survive in harsh alpine conditions.