Project Details
Projekt
Sensitivity and Response of Treeline Ecotones in the Nepal Himalaya to Climate Warming (TREELINE-II)
Subject Area
Forestry
Physical Geography
Physical Geography
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 496940480
Treeline shifts in response to climate warming have been shown for many treeline environments in the world. However, recent studies including our own findings from TREELINE-I indicate that climate warming effects are altered at local scale by non-thermal factors. At the Rolwaling treeline, our results suggest that the dense Rhododendron campanulatum krummholz zone retards a treeline shift to higher elevations. We assume krummholz thickets to be highly competitive and to act as a barrier, slowing down population processes at the front-edge of the treeline-forming species Betula utilis and Abies spectabilis. Other driving factors of treeline inertia presumably include limited availability of nitrogen and phosphorous, as well as soil moisture deficits in the pre-monsoon season, the latter adversely affecting tree growth in recent decades. These findings point to considerable research gaps that still render meaningful predictions of treeline dynamics under climate change conditions impossi¬ble. TREELINE-II will test the hypothesis that krummholz zones are the crucial structural component of central Himalayan treeline ecotones controlling any treeline shifts, and that climate warming leads to widely disparate spatial and temporal responses of krummholz and non-krummholz treelines. Diverging spatial responses are presumably caused by intrinsically driven feedback mechanisms such as allelopathy and nutrient limitation, which affect temporal responses as reflected in primarily climate driven species-specific growth dynamics. Understanding spatial and temporal differences in response to climate change between krummholz and non-krummholz treelines is key to the question to what extent Himalayan treeline shifts can be expected in the 21st century. To analyse the contradicting responses, TREELINE-II will extend the Himalayan study sites with a balanced share of krummholz and non-krummholz treelines, and will provide a comprehensive climate-environmental analysis and modelling framework, allowing robust projections of potential future changes in the elevational structure and dynamics of Himalayan treeline ecotones. TREELINE-II will be the first project to address in detail a hitherto largely omitted component of Himalayan treeline ecotones, shifting the scientific focus of Himalayan treeline research to the role of the krummholz zone in treeline inertia, and deliver a step-change in process-based understanding of krummholz vs. non-krummholz treeline dynamics.
DFG Programme
Research Grants
Co-Investigators
Dr. Maria Bobrowski; Dr. Shabeh Hasson; Dr. Ruhollah Taghizadeh-Mehrjardi
