JEE Journal of Ecology and Environment RESEARCH Regeneration and leaf traits variation of Rhododendron campanulatum along elevation gradient in western Nepal Himalaya Dipesh Karki 1 , Bijay Pandeya 2 , Rachana Bhandari 2 , Dikshya Basnet 1 , Balkrishna Ghimire 1 , Shreehari Bhattarai 1 and Bharat Babu Shrestha 3 * 1 Faculty of Forestry, Agriculture and Forestry University, Hetauda 44107, Nepal 2 Boreal Terrestrial Ecosystems Laboratory (ECOTER), University of Quebec at Chicoutimi, Chicoutimi, QC G7H 2B1, Canada 3 Central Departments of Botany, Tribhuvan University, Kritipur 44613, Nepal ARTICLE INFO Received January 22, 2024 Revised February 26, 2024 Accepted March 7, 2024 Published on April 23, 2024 *Corresponding author Bharat Babu Shrestha E-mail shresthabb@gmail.com Background: Plant species of the alpine treeline ecotone are highly sensitive to climate change and may adjust their population dynamics, and functional traits in response to changing climate. This study examined regeneration patterns and leaf traits variations in an important treeline ecotone element Rhododendron campanulatum along the el- evation gradient in western Nepal to assess its potential adaptive responses to climate change. The distribution range of R. campanulatum (3,400–3,800 m above sea level [a.s.l.]) was divided into five horizontal bands, each with a 100 m elevational range. Eight plots (10 m × 10 m) were sampled in each band, resulting into a total of 40 plots. In each plot, all R. campanulatum individuals and co-occurring tree species were counted. From each elevation, R. campanulatum leaf samples were collected to determine leaf dimensions, leaf density, specific leaf area (SLA), and stomatal density (SD). Results: The density-diameter curve indicated that R. campanulatum was regenerating well, with enhanced regeneration at higher elevation (3,800 m a.s.l.) than at lower. Tree canopy cover appeared to be the major determinant of R. campanulatum regeneration, as indicated by a higher number of seedlings in treeless stands. With increasing elevation, the leaf length, width, SLA, and stomata length decreased but leaf thickness and SD increased. Conclusions: Overall, a higher regeneration and lower SLA with the high SD in the leaves at the upper limit of the species distribution suggested that R. campanulatum is well adapted at its upper distribution range with the possibility of upslope range shift as temperature increases. Keywords: climate change, leaf stomata, Nepal Himalaya, plant functional traits, specific leaf area, treeline ecotone Introduction High-elevation regions are particularly sensitive to shift- ing climatic belts due to global climate changes, and, con- sequently, they are strong indicators of climate change be- cause the vegetation they have is highly influenced by temperatures (Grabherr et al. 1994). The growth and re- production of plant communities in higher elevations are mainly controlled by temperature (Grace et al. 2002), re- sulting in steep ecological gradients along with elevation and restricted ecotone (Pauli et al. 2015). Therefore, minor fluctuations in ambient temperature may induce alter- ations in the elevational position of the treeline. Addition- ally, many plant species are shifting upward as a result of global warming, creating higher stand densities and driv- ing treelines to higher elevations (Gaire et al. 2017; Singh et al. 2018; Tiwari et al. 2017). Treeline dynamics can be characterized by studying re- generation patterns of the treeline forming species (Mainali et al. 2020; Sharma et al. 2020), which may be reflected in the population structure (Tiwari et al. 2018). Successful re- generation is indicated by the presence of an adequate number of seedlings, saplings, and young trees in a given population (Mishra et al. 2013; Pokhriyal et al. 2010). Re- generation not only displays the current condition, health, and vitality of the forest but also shows how the forests will look like in the future (Zhang et al. 2007). Regeneration varies along elevation gradients due to differing tempera- ISSN: 2288-1220 https://doi.org/10.5141/jee.24.011 (2024) 48:16 © 2024 The Author(s) Open Access Open Access This article is licensed under a Creative Commons Attribution (CC BY) 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ The publisher of this article is The Ecological Society of Korea in collaboration with The Korean Society of Limnology.