Chin J Plant Ecol ›› 2018, Vol. 42 ›› Issue (11): 1082-1093.DOI: 10.17521/cjpe.2018.0082

• Research Articles • Previous Articles     Next Articles

Spatio-temporal dynamics of two alpine treeline ecotones and ecological characteristics of their dominate species at the eastern margin of Qinghai-Xizang Plateau

ZHOU Tian-Yang1,2,3,NARAYAN Prasad Gaire4,8,LIAO Li-Bin1,2,ZHENG Li-Li2,5,WANG Jin-Niu1,3,6,*(),SUN Jian5,WEI Yan-Qiang7,XIE Yu1,WU Yan1,3,*()   

  1. 1Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China
    2University of Chinese Academy of Sciences, Beijing 101408, China
    3Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization, Chinese Academy of Sciences, Chengdu 610041, China
    4Central Department of Environmental Science, Tribhuvan University, Kathmandu, Nepal
    5Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
    6International Center for Integrated Mountain Development, Kathmandu, Nepal
    7Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
    8Xishuangbanna Tropical Botanical garden, Chinese Academy of Sciences, Xishuangbanna, Yunnan 666303, China
  • Received:2018-04-11 Accepted:2018-11-04 Online:2018-11-20 Published:2019-03-13
  • Contact: Jin-Niu WANG,Yan WU
  • Supported by:
    Supported by the National Natural Science Foundation of China(41661144045);Supported by the National Natural Science Foundation of China(31400389)

Abstract:

Aims Temperature limit is the main cause of alpine treeline formation. Therefore, it is important to understand the response mechanisms of alpine treeline as well as their tree species under the global climate change. The present study focused on the spatio-temporal dynamics of treeline and ecological characteristics of the tree species in two treeline ecotones.
Methods Two vertical belt-transect plots were established in each treeline ecotone of the Zheduo Mountain and Jianziwan Mountain of the eastern Qinghai-Xizang Plateau. Top and bottom of each transects were lain between species line and forest line, respectively. Detailed information of each tree species treeline, including species name, latitude, longitude, height, age, base diameter, and coordinates, was recorded accordingly.
Important findings The temperatures of the two research areas have increased during the past 58 years. The precipitation has decreased slightly in both the Zheduo Mountain and Jianziwan Mountain. The age structure of Abies fabri from the Zheduo Mountain and A. squamata from the Jianziwan Mountain showed a reversed “J” shape curve and a bimodal shape, respectively. Within the two transects, due to the limitation of seed diffusion, the dominate species showed aggregated distributions at the small scale. At the large scale, A. fabri was aggregated at the Zheduo Mountain, while A. squanmata of the Jianziwan Mountain was randomly distributed due to the impact of surrounding environmental factors. Both tree height and base diameter decreased with the increase of elevation. The fir trees (Abies spp.) at the upper part of the treeline ecotone presented an allometric growth, whose height growth rate was higher than that of base growth, while the relationships between height growth and base growth were isometric at almost mid and lower part of the treeline ecotone. Compared with 10 years ago, there was no significant change at the position of treeline and tree species line of the Zheduo Mountain and the Jianziwan Mountain, neither of the tree density in the Jianziwan Mountain. However, the number of trees in the Zheduo Mountain increased by about 25%. Compared with 20 years ago, tree species lines of the Zheduo Mountain and Jianziwan Mountain were shifted upwards by 50 and 30 m, respectively. Besides, their treeline positions were increased by 75 and 40 m, respectively. Furthermore, the number of trees also increased significantly by 220% and 100%, respectively. Therefore, the treeline and its constructive species are mainly affected by temperature at the large spatio-temporal scale, while influenced by temperature and ambient environment at the small spatio-temporal scale.

Key words: treeline, spatio-temporal dynamics, age structure, allometric, altitude gradient