How will the Distribution and Size of Subalpine Abies Georgei Forest Respond to Climate Change? A Study in Northwest Yunnan, China

Abstract

The changing recruitment rate of subalpine tree populations could indicate the effects of climate change on a mountain ecosystem. The population of the dominant tree species of the Baima Snow Mountains in northwestern Yunnan, Abies georgei Orr, was investigated with a vegetation survey and tree-ring analysis. Structural and age characteristics were used to indicate the process and rates of geographical change, and the altitudinal range and size of forest were predicted using GIS with various climate change scenarios. The greatest increase of recruitment has occurred near the upper treeline on north-facing slopes, and the regeneration rate has been reduced at and below its once-optimal altitudinal range. The species limit has advanced upslope at an average rate of 11 m per decade, while the lowest limit of regeneration has retreated upslope at an average rate of 31 m per decade. In the 21st century, the altitudinal range of A. georgei forest may decrease by 13.6-25.9% and the forest size may contract by 16.4-38.6%. We demonstrate that the study of both upper and lower species limits of migrating subalpine species is crucial for predicting forest change, and suggest the involvement of spatial (geometry) as well as temporal (climate) factors in the shifting of alpine treeline.

Keywords:

• Age structure
• Baima Snow Mountain Nature Reserve
• dendrochronology
• species range
• forest size
• alpine treeline
• tree-rings