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

摘要：

为了揭示天然林优势树种对资源环境利用状况及其竞争程度,在太行山南麓海拔850—1850 m天然林分布区设置29块固定监测样地并进行生态学调查,在对天然林树种结构进行PCoA主坐标分析的基础上,采用物种重要值及其变异系数、生态位宽度、生态位重叠指数、生态位相似性指数等指标研究了不同海拔梯度天然林优势树种的生态位特征。结果表明：PCoA主坐标分析和ANOSIM群落相似性检验结果均显示不同海拔梯度乔木树种结构存在着显著的差异（r=0.199,P=0.006）;不同海拔梯度的29个样地中共记录到乔木树种68种,其中栓皮栎（Quercus variabilis）在低海拔区（850—1150 m）和中海拔区（1150—1450 m）重要值均最大,分别为0.389和0.332;槲栎（Quercus aliena）在高海拔区（1450—1850 m）重要值最大,其值为0.227,且在3个海拔区生态位宽度均最大,其Levins和Shannon生态位宽度分别为7.293和2.153、4.023和1.548、8.269和2.200。中海拔区所有优势树种的生态位重叠指数均值和生态位相似性均值均最高,其值分别为0.49和0.39;Levins和Shannon生态位宽度值分别与优势种重要值呈显著正相关（r=0.791,t= -5.777,P=0.010,n=14;r=0.599,t= -8.813,P=0.024,n=14）。研究区重要值和生态位宽度较大的树种为栓皮栎和槲栎,中海拔区优势树种对资源环境需求较相似,种间竞争较激烈。亟需开展以调整种间关系为主要目标的森林经营活动,进而促进健康稳定的林分形成。该研究可为开展不同海拔梯度植物群落发育动态研究提供理论依据,也可为制定科学合理的天然林保护措施提供参考。

关键词: 生态位特征, 优势树种, 海拔梯度, 天然林, 太行山南麓