Adaptive strategies of Rhododendron campanulatum and Rhododendron anthopogon subsp. hypenanthum in the alpine ecosystem of Central Himalaya, India

Rhododendron campanulatum and Rhododendron anthopogon subsp. hypenanthum are significant species of the alpine ecosystem of the Central Himalaya, India where they not only constitute the important ecological associations but have also been integrated within the culture of the local residential population. This study investigated their adaptive strategies against the alpine environmental stress through ecological and morphological assessments along an altitudinal gradient. Ecological data were collected from 10 quadrats (plot size 10 m x 10 m each) laid per site, while morphological traits were measured from 100 healthy and mature leaves (10 from each of 10 randomly selected individuals) from each sampling site of the study area. Results of Importance Value Index and Provenance Value showed that both species became increasingly dominant at higher altitudes. R. campanulatum exhibited IVI of 62.7 at Site 2, 193.3 at Site 3 and 268.1 at Site 4. R. anthopogon subsp. hypenanthum showed PV of 35.7 at Site 2, 55.5 at Site 3 and 98.4 at Site 4 confirming their dominancy in upper zones. Leaf morphology analyses, based on 10 mature leaves collected from each site, showed Leaf area (r= -0.93⁎⁎), Specific leaf area (r = -0.88⁎⁎) and Leaf shape index (r= -0.812⁎⁎) significantly decreased with increasing altitude and varied along the altitude at p < 0.05 level of significance. It was also observed that R. campanulatum was shrinking in size and transforming to woody thickets with increasing altitude. The obtained results showed the survival of both the species of Rhododendron L. in the study area as an attribute of their plasticity against the tough environmental conditions of the alpine ecosystem.