Fir Treeline in South Eastern Tibetan Plateau: Little Change in 200 years of Warming

Today, I am discussing about the paper published in May 2011 issue of New Phytologist entitled: Little change in the fir tree-line position on the southeastern Tibetan Plateau after 200 years of warming, by Eryuan Liang, Yafeng Wang, Dieter Eckstein and Tianxiang Luo.

 

The authors have started the paper with the definition of treeline given by Korner and Paulsen (2004), personally this is most favored definition of treeline by me also. Treeline elevation, tree regeneration, and growth are controlled by temperature, thus treeline communities quickly response to climate change by showing changes in structure and position. Authors have cited various papers, which have reported treeline shift around the world. Most significant one is by Harsch et al. (2009), which indicated that treeline has shifted in 55% of 166 study site all around the world. In the study site of this paper Sygera Mountain, Tibetan Plateau, and very few study has been carried out related to treeline ecotone in this area.  Abies georgei (Smith fir) is the treeline species, and treeline varies from 4250 m in south-facing slope to 4400 m north facing slope. It is a natural treeline, and form is diffuse type. This site is away from human disturbances. Three 30 m x 150 m rectangular plots were laid down from forest line to species line. Treeline was defined as uppermost tree with a minimum height of 2 m, and upward shift of treeline is defined as the change in elevation at which the highest tree is found.  Dendroecological methods were used to analyze the recruitment pattern and treeline shift.  

The age structure in all the plots showed reverse J shaped structure and most of the individuals were established after 1950s, and recruitment rate increase abruptly after 1970s, which indicate global warming impact on recruitment pattern. However, treeline has not shifted significantly in all these plots, and possible reasons are lack of seed dispersal and disturbance. Lastly, authors have suggested for comprehensive treeline studies across the Sygera Mountain for more concrete understanding of treeline dynamics and climate change.  

May issue of New Phytologist can be accessed at: http://onlinelibrary.wiley.com/doi/10.1111/nph.2011.190.issue-3/issuetoc

-Parveen Kumar Chhetri