Influence of climatic and geographic factors on the spatial distribution of Qinghai spruce forests in the dryland Qilian Mountains of Northwest China

Wenjuan Yang; Yanhui Wang; Ashley A Webb; Zengyuan Li; Xin Tian; Zongtao Han; Shunli Wang; Pengtao Yu

doi:10.1016/j.scitotenv.2017.08.180

Influence of climatic and geographic factors on the spatial distribution of Qinghai spruce forests in the dryland Qilian Mountains of Northwest China

Sci Total Environ. 2018 Jan 15:612:1007-1017. doi: 10.1016/j.scitotenv.2017.08.180. Epub 2017 Sep 7.

Authors

Wenjuan Yang¹, Yanhui Wang², Ashley A Webb³, Zengyuan Li⁴, Xin Tian⁴, Zongtao Han⁴, Shunli Wang⁵, Pengtao Yu¹

Affiliations

¹ Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Key Laboratory of Forest Ecology and Environment of the State Forestry Administration of China, Beijing 100091, China.
² Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Key Laboratory of Forest Ecology and Environment of the State Forestry Administration of China, Beijing 100091, China. Electronic address: wangyh@caf.ac.cn.
³ NSW Department of Primary Industries, Tamworth Agricultural Institute, Calala, NSW 2340, Australia.
⁴ Research Institute of Forest Resource Information Techniques, Chinese Academy of Forestry, Beijing 100091, China.
⁵ Academy of Water Resource Conservation Forests of Qilian Mountains in Gansu Province, Zhangye 734000, Gansu, China.

PMID: 28892842
DOI: 10.1016/j.scitotenv.2017.08.180

Abstract

The effect of climate variables (temperature and precipitation) on forest spatial distribution is more prominent in dryland high mountains, where forest distribution is inherently very sensitive to and strongly limited by the substantial spatial heterogeneity of site conditions. Thus, a more reliable prediction of forest distribution under changing environment depends upon an understanding of the joint influence of climatic and topographic factors and their thresholds. This study was conducted on Qinghai spruce forests as dominant tree species in the Qilian Mountains of northwest China. The spruce forest distribution was surveyed by remote sensing in Dayekou watershed and by field investigation in a nested smaller watershed. Analyses showed that mean annual air temperature and precipitation, which vary with elevation, are the key climatic factors determining forest distribution, but slope aspect also plays an essential role. The potential core distribution area of denser forests and potential distribution area including sparse forests are between the axes of elevation (2635.5-3302.5 and 2603.4-3325.8m a.s.l.) and slope aspect (-74.4-61.2° and -162.6-147.1° deviated from north). The corresponding threshold of mean annual air temperature at the upper elevation boundary is -2.59 and -2.73°C, while the threshold of mean annual precipitation at the lower elevation boundary is 378.1 and 372.3 mm, respectively. Using these thresholds and the elevation gradients of climatic factors, the shifting of elevation boundaries under climate change scenarios can be predicted. However, the forest distribution is also limited by a soil thickness of ≥40cm; and by slope position of lower-, lower- and middle-, and entire-slope within the elevation ranges of <2800, 2800-2900, and >2900m a.s.l., respectively. This study showed that adding geographic factors will greatly improve the prediction of changes in forest distribution area in dryland mountains, in addition to the influence of climatic factors.

Keywords: Arid zone; Climate change; Forest distribution; Mountain area; Topography.