关键词: 生态位特征, 优势树种, 海拔梯度, 天然林, 太行山南麓

Abstract:

In order to reveal the utilization status for resources of dominant tree species and the degree of competition between dominant tree species in natural forests, twenty-nine fixed plots have been established in the natural forest distribution area at an altitude of 850-1850 m in the south of Taihang Mountains, and ecological investigations has been carried out also. On the basis of Principal Coordinate Analysis (PCoA) for the structure of natural forest tree species, the niche characteristics of dominant tree species in natural forests at different altitude gradients were studied using indicators such as species importance value and its coefficient of variation, niche width, niche overlap index, and niche similarity index. The results of PCoA and ANOSIM community similarity tests showed that significant differences in the structure of tree species at different altitude gradients were found (r=0.199, P=0.006). A total of 68 tree species were recorded in 29 plots at different altitude gradients, of which the Quercus variabilis had the biggest important values in the lower altitude area (850-1150 m) and the medium altitude area (1150-1450 m) (important values were 0.389 and 0.332, respectively). The importance value of Quercus aliena (0.227) was the biggest in the higher altitude area (1450-1850 m) of all dominant tree species, and the niche width of Quercus aliena was the largest in all altitudinal gradient areas of all dominant tree species, with Levins and Shannon niche widths were 7.293 and 2.153, 4.023 and 1.548, 8.269 and 2.200, respectively. The average niche overlap index values and the average niche similarity values of all dominant tree species in the medium altitude area are the highest, which were 0.49 and 0.39, respectively. The niche width values of Levins and Shannon were significantly positively correlated with the important values of dominant species, respectively (r=0.791, t= -5.777, P=0.010, n=14; r=0.599, t= -8.813, P=0.024, n=14). Therefore, the tree species with larger important values and niche widths in the study area are Quercus variabilis and Quercus aliena. The dominant tree species in the medium altitude area have similar resource and environmental requirements, and strong competition between species. The forest manage activities should been introduced immediately to adjust the relationship between tree species, which in turn would promote the establishment of healthy and stable forest stands. This study could provide a theoretical basis for the study of plant community dynamics at different altitude gradients, as well as a reference for the development of scientific and reasonable natural forest protection measures.

Key words: niche characteristics, dominant tree species, altitudinal gradient, natural forest, south of Taihang Mountains