Abstract:

Aims Comparison of populations of different plant species can reveal the formation mechanism and the influencing factors of the populations. We compared quantitative features of populations of Pinus tabulaeformis and P. armandii, which are the dominants in naturally regenerating communities, following water damage 17 years ago in part of the Fanjiazhuang section of the Caiyuhe Watershed of Qinling Mountain. We asked whether biological features of P. tabulaeformis and P. armandii influence the population size, age structure and population survival dynamics.
Methods We measured the height, basal diameter and age (number of whorled branches) of two individuals in a total plot area of 11 900 m² in 2005.
Important findings As a result of faster height and lateral growth, P. tabulaeformis had greater mean height and basal diameter than P. armandii, and individuals occupied larger vertical and horizontal space. The two populations had different height, diameter and age structures, and no consistenay, which indicated that size structure did not always reflect the age structure. The populations had different age structures, with that of P. tabulaeformis skewed to older trees and that of P. armandii in a near normal distribution. The age structure of P. armandii population was influenced by slope aspect, but that of P. tabulaeformis population was not. Both survivorship curves were the type Ⅱ, which indicated that both populations had similar survival dynamics. Therefore, the different biological characteristics of P. tabulaeformis and P. armandii led to different population size and age structure features, but not survival processes. This implied that environmental factors were the main determinants of population survival dynamics.

Key words: Qinling Mountain, population, quantitative features, Pinus tabulaeformis, P. armandii, water damage