Elevation is a strong determinant of local climate and may therefore be an important factor to consider when examining the association between climate and tree growth. In this study, we developed a set of tree-ring width records for Abies spectablis (D.Don Spach) in the Manang Valley of central Nepal Himalaya and tested how tree growth and the relationship between tree growth and climate varied across a 450-m elevation transect. The sampled trees had a median age of 115 years, and the oldest individual specimen, which was located at 3775 m, had more than 212 rings. The common signal shared across the tree-ring series was relatively weak, which is typical for ring-width chronologies from the Himalayas. Even though these forests are located within a semi-arid climate, temperature had a stronger and more consistent influence on Abies growth than precipitation. All three chronologies across the transect exhibited a negative relationship with mean March–June temperatures, which could reflect the impact of warm weather during the early part of the growing season, possibly mediated through its influence on evapotranspiration and soil moisture. While interannual fluctuations in tree growth were synchronous across sites, longer-term trends in growth varied across the transect, with high-elevation trees showing elevated growth during the last two or three decades and lower-elevation trees behaving just the opposite. These disparate trends suggest the factors that control longer-term trends in forest productivity vary substantially with elevation. For studies intending to use tree-ring width records in the Trans Himalaya as climate proxies, it may be preferable to collect specimens at lower forest sites, where the agreement across the population of trees is stronger. Because longer-term trends in ring width can differ substantially from one elevation to another in this region, it may also be necessary to collect a greater number of samples from several positions along an elevation gradient.
Bibliographical noteFunding Information:
This research was funded by the Community-based Forest Management in the Himalaya Project , a joint Danida-funded initiative of the University of Copenhagen, the Department of Forest Research and Survey (DFRS), Nepal and the Institute of Forestry, Tribhuvan University. We thank Mr. Rabindra Maharjan for his support in fieldwork and sample preparation, and Mr. Narayan Gaire for helpful advice on sample collection and analysis. Dr. Kurt Kipfmueller provided constructive advice at an early stage in this project. The DFRS provided access to laboratory facilities for sample preparation and tree-ring measurement and the Annapurna Conservation Area Project gave permission to conduct fieldwork in the Manang Valley.
- Abies spectabilis
- Central Himalaya
- Elevation transect
- Tree-climate relations