Life history and spatial distribution of a Taiwania flousiana population in Leigong Mountain, Guizhou province, China

Abstract

Aims: We studied the life history and distribution of a Taiwania flousiana Gaussen population in Leigong Mountain, Guizhou Province, China, to explain population growth characteristics, and how biological and environmental factors affect population distribution and dynamics. Methods: T. flousiana, a rare and endangered plant, is distributed in patches on southeastern facing slopes at altitudes of 800-1300m on Leigong Mountain. We sampled trees in 30 plots (30m × 30m), and in each plot, we established 9 subplots (10m × 10m) to measure the shrubs, grasses and regeneration of this species. We recorded the diameter at breast height (DBH) of each tree, and then divided them into 13 size classes: S1, H ≤ 2. 5m (DBH < 5. 0cm); S2, H > 2. 5m (DBH < 5. 0cm); S3, 5. 0cm ≤ DBH < 10. 0cm; S4, 10. 0cm ≤ DBH < 15.0cm; S5, 15. 0cm ≤ DBH < 20. 0cm, and so on. We recorded the location of every T. flousiana individual using coordinates (x,y) within each subplot. We determined the population size and structure, life expectancy and survivorship curve of T. flousiana to analyze population structure and dynamics. Important findings: Because T. flousiana seedlings and big trees were rare, the structure and size classes of the population indicate the T. flousiana population is in decline. This appears to be caused by the species biological characteristics and environmental factors. The survivorship curve of this T. flousiana population generally matches the Deevey II type. There are 2 peaks of mortality in the 6th and 12th size classes caused by intraspecific competition for resources and physiological aging, respectively. The life expectancy of this species decreased monotonically during its life span, although T. flousiana seedlings and big trees were rare and had low survival rates. The species generally has a clumped distribution pattern, but this gradually changes over time from a clumped to a random pattern as trees matures from young to middle-aged to old trees. Populations tend to be clumped in the first five size classes, and are distributed-randomly from the 7th size class to the 13th size class. These different developmental stages were related to the biological and ecological characteristics of the species and to microenvironmental conditions. Meanings: We conclude T. flousiana conservation strategies should focus on seedling establishment and conservation, reducing human disturbance and enhancing genetic diversity between populations.