Chin J Plant Ecol ›› 2007, Vol. 31 ›› Issue (5): 857-864.DOI: 10.17521/cjpe.2007.0108

Special Issue: 青藏高原植物生态学:种群生态学

• Research Articles • Previous Articles     Next Articles

ECOLOGICAL CHARACTERISTICS OF A SABINA SALTUARIA POPULATION AT TIMBERLINE ON THE SOUTH-FACING SLOPE OF BAIMA SNOW MOUNTAIN, SOUTHWEST CHINA

ZHANG Qiao-Ying1,2(), ZHANG Yun-Chun1, LUO Peng1, WANG Qian1, WU Ning1,*()   

  1. 1Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China
    2State Key Laboratory of Biocontrol, Sun Yat-Sen University, Guangzhou 510275, China
  • Received:2006-04-18 Accepted:2006-07-16 Online:2007-04-18 Published:2007-09-30
  • Contact: WU Ning

Abstract:

Aims Alpine timberlines are ecotones highly sensitive to disturbances and environmental changes that have become a major focus of global climate change research. Sabina saltuaria is an endemic timberline tree in the Qinghai-Tibetan Plateau. It occurs mainly on south-facing slopes and may be useful in ecological restoration of the high-altitude ecosystem. Understanding its ecological characteristics is necessary for understanding its adaptation strategies, as well as the causes and dynamics of timberline patterns in the region.

Methods We established one 0.42 hm2 sample plot at timberline >4 390 m on the south-facing slope of Baima Snow Mountain, Northwest Yunnan Province. We recorded height, DBH (diameter at breast height) or diameter at base for seedlings and saplings, and location of each individual. We used a compass and electronic distance-measuring tool to record the location of each individual. We analyzed the size and DBH structure, time-specific life table, survivorship rate, mortality and hazard rate, spatial point pattern of individuals in each age-class and the co-relationships between different age classes.

Important findings Few seedlings occur at timberline in the area of our field survey (about 17 ind·hm-2, only 1/6 and 1/14 of that of saplings and trees, respectively). Densities declined from trees to saplings to seedlings, and the number of individuals decreased gradually with greater DBH. The survivorship curve was between Deevy type Ⅱ and Ⅲ. The mortality rate curve was similar to the hazard rate curve; both exhibited a peak of mortality at 6-9 cm DBH). Spatial point pattern analysis indicated that most individuals of different age classes had a clumped distribution at different scales (the older the trees, the more aggregative the distribution pattern); however, seedlings had a random distribution at the scale of <14 m. Also the relationships among individuals in different age classes were all significantly correlated with each other. The associations were more significant between seedlings and trees.

Key words: population structure, time-specific life table, survival analysis, spatial point pattern, alpine timberline