Sensitivity of Treeline in Response to Climate Change

Regional Patterns and Local Processes in the Himalayan Region

   TwitCount

Background

The climate change phenomemnon is the greatest threats to the arctic and alpine zones. High-altitudes zones of the Himalayas are particularly susceptible to climate variability and have shown increase in warming, and perhaps sooner, than the rest of the globe. Among the global mountains regions, the Himalaya is warming almost 2-5 times higher than the global average. The extereme event of climatic varaibilities have been reported and the consequence of such changes are bringing diverse challenges across the Himalayas. The western Himalaya is reported with dry spills with increasing temperature and variation in precipitations while the eastern Himalaya is facing incrasing temperature with increasing intensity of precipitations.   

There is a strong general link between climate change and treeline fluctuation. It is widely hypothesized that treeline structure and position will undergo a significant change in response to current and anticipated future increasing temperature worldwide. Treelines are reported to advance to higher altitude or higher latitude in response to climate warming due to one of the sensitive indicators, i.e. heat deficiency. However, inconsistent observation of global treeline fluctuation suggests the sensitivity of treeline dynamics depend on biotic and abiotic factors in addition to climate warming. The Himalayan region is characterized by the most diverse treeline species and highest treelines among the world. Additionally, high altitude Himalaya is experiencing dramatic warming in the past decades and treelines were affected by mass elevation effect. Therefore, Himalayan treelines are expected to present sensitive responses, including intense tree recruitment and extensive treeline fluctuation, to climatic variability. Macroclimate warming mainly drives temporal changes of alpine treeline in regional scale, but physical and biotic factors moderate it at local sites.

The treeline variability is not only influenced by climate change, but also mediated by species-specific traits and environmental conditions at multiple scales. However, patterns and process of treeline dynamics in response to climate variability, usually mediated by biotic and abiotic factors, are poorly understood and not synthesized in the Himalayas. It is possible to reconstruct treeline position dynamics by using tree recruitment history. This project hypothesizes that sensitivity of Himalayan treeline is determined by climate warming but the process was mediated by physiographic, tree species, treeline form, tree recruitment and growth patterns, and consequently inducing treeline positions and dynamics. The purpose of this project is to reconstruct the history of different treeline dynamics in response to climatic variability along Hindu Kush Himalayan region (HKH) from west Pamir to eastern Tibetan Plateau. The sensitivity of different types of treelines to climatic and environmental change will be studied.

In summary, current understanding of treeline dynamics does not fully explain past and present patterns and their underlying processes, nor allow prediction of their response to climate change. Particularly, there has been little focus on the spatial variation of treeline patterns over larger scale along the HKH. This highlights the needs for a comprehensive and representative assessment across the region regarding the treeline sensitivity to climate change and the combined effects with other physical and biotic factors, and the relative importance of factors on tree growth and treeline position. Thus, it is essential to establish a collborative partnership for comparable studies, knowledge and data sharing and regional meta reserach regarding treeline dynamics.

Selected typical sampling sites of alpine treeline study in the HKH

Objectives

The objective of this regional inception workshop is to establish cooperative mechanism and strengthen collaborative research and synergy among the scientists working on treeline across the HKH and enhance communication, interaction, and data sharing platforms. We aim to examine the impact of climate variability on the tree regeneration, growth processes in treeline ecotone that affects structure and patterns of treelines in the HKH through collaborative research. This will be achieved through the following actions:

  • Knowledge and experience sharing on the research progress and hotspots for treeline study across the HKH;
  • Standardization of protocols and methodology amongst partners of the NSFC-ICIMOD alpine treeline project for sensitivity of treeline in response to climate change in the HKH;
  • Planning on roles, actions and timline for next 3 years regarding collaborative research on treeline in response to climate change in the Himalayan region

Expected outputs

  • Clear-cut division of roles, and implementation plans, activities, and responsibility;
  • Standardized protocols and methodologies for field investigation of tree regeneration, tree growth and treeline position using dendrochronological method at different sites of treeline;
  • Workshop proceedings including abstract, presentation, and summary learning;
  • Setting up a regional Himalaya alpine treeline research network