Tree-ring climate response of Fir and Birch from the sub-alpine forest of Dhorpatan Hunting Reserve, western Nepal

Authors: Michelle Mohr*, Department of Earth Science and Geography, California State University, Dominguez Hills, Raju Bista, Department of Earth Science and Geography, California State University, Dominguez Hills, Parveen Chhetri, Department of Earth Science and Geography, California State University, Dominguez Hills
Topics: Biogeography, Mountain Environments
Keywords: Basal Area Increment, drought, growth-climate correlation, radial growth, Ring Width Index
Session Type: Virtual Paper
Day: 4/10/2021
Start / End Time: 8:00 AM / 9:15 AM
Room: Virtual 32
Presentation File: No File Uploaded


The fir (Abies spectabilis) and birch (Betula utilis) are tree species often found coexisting in sub-alpine forest of the Nepal Himalayas. Studies have been carried out on radial growth patterns in their mono-dominant stands. However, no previous study has been recorded from the Dhorpatan Hunting Reserve, western Nepal. Therefore, to assess the temporal growth performance of these cohabitant species, tree-ring samples were collected from the mixed stand at elevation range of 3300-3500 m. Morphometric features such as the diameter at breast height, tree height, and canopy diameter were also measured. Standard ring-width chronologies of both species were developed applying cubic spline detrending to remove non-climatic signals. The ring width chronologies were correlated with climatic variables. We found differential and contrasting responses to climate over time. Birch showed positive growth response to precipitation and negative response to temperature in spring months. Whereas the radial growth of fir was correlated negatively with precipitation and positively with temperature in spring. Moving correlation analyses revealed the divergent influence of the spring climate on these species. Increased temperature and decreasing precipitation appeared to be stronger in the birch's growth limitation, whereas the positive influence of higher temperature on fir growth is gradually diminishing. The significant rising trend of temperature by 1970s coincided with growth decline of birch and increase in fir, as indicated by Basal Area Increment. Thus, the changing climate appeared to drive the successional dynamics in the mixed stand such that fir has potential to occupy the area with continued current climatic trend.

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