Implications of tree species – environment relationships for the responsiveness of Himalayan krummholz treelines to climate change Implications of tree species – environment relationships for the responsiveness of Himalayan krummholz treelines to climate change

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Vol14 No.3: 453-473

Title】Implications of tree species – environment relationships for the responsiveness of Himalayan krummholz treelines to climate change

Author】Niels SCHWAB1*; Udo SCHICKHOFF1; Birgit BÜRZLE1; Michael MÜLLER2; Jürgen BÖHNER1; Ram Prasad CHAUDHARY3; Thomas SCHOLTEN2; Jens OLDELAND4

Addresses】1 CEN Center for Earth System Research and Sustainability, Institute of Geography, University of Hamburg, Bundesstraße 55, 20146 Hamburg, Germany; 2 Department of Geosciences, Chair of Soil Science and Geomorphology, University of Tübingen, Germany; 3 Research Centre for Applied Science and Technology & Central Department of Botany, Tribhuvan University, Nepal; 4 Biocentre Klein Flottbek, University of Hamburg, Ohnhorststr. 18, 22609 Hamburg, Germany

Corresponding author】niels.schwab@uni-hamburg.de

Citation】Schwab N, Schickhoff U,BürzleB, et al. (2017) Implications of tree species – environment relationships for the responsiveness of Himalayan krummholz treelines to climate change. Journal of Mountain Science 14(3). DOI: 10.1007/s11629-016-4257-z

DOI】10.1007/s11629-016-4257-z

Abstract】Climate warming is expected to advance treelines to higher elevations. However, empirical studies in diverse mountain ranges give evidence of both advancing alpine treelines as well as rather insignificant responses. In this context, we aim at investigating the sensitivity and responsiveness of the near-natural treeline ecotone in Rolwaling Himal, Nepal, to climate warming. We analysed population densities of tree species along the treeline ecotone from closed forest stands via the krummholz belt to alpine dwarf shrub heaths (3700-4200 m) at 50 plots in 2013 and 2014. We quantified species - environment relationships, i.e. the change of environmental conditions (e.g., nutrient and thermal deficits, plant interactions) across the ecotone by means of redundancy analyses, variation partitioning and distance-based Moran's eigenvector maps. In particular, we focus on explaining the high competitiveness of Rhododendron campanulatum forming a dense krummholz belt and on the implications for the responsiveness of Himalayan krummholz treelines to climate change. Results indicate that treeline trees in the ecotone show species-specific responses to the influence of environmental parameters, and that juvenile and adult tree responses are modulated by environmental constraints in differing intensity. Moreover, the species - environment relationships suggest that the investigated krummholz belt will largely prevent the upward migration of other tree species and thus constrain the future response of Himalayan krummholz treelines to climate warming.

Keywords】Himalaya; Nepal; Population structure; Rhododendron campanulatum; Spatial patterns; Species-environment relationships; Stand density; Variation partitioning