秦岭水灾迹地油松和华山松更新种群数量特征

QUANTITATIVE FEATURES OF POPULATIONS OF PINUS TABULAEFORMIS AND P.ARMANDII REGENERATED FOLLOWING WATER DAMAGE AT QINLING MOUNTAIN,CHINA

不同植物种群种间比较研究利于揭示种群的形成机制和影响因素。该文研究了秦岭地区蔡玉河流域范家庄段水灾迹地恢复17年后群落优势种油松(Pinus tabulaeformis)和华山松(P.armandii)的种群数量特征。水灾灾后第一年(1989年)就有油松和华山松个体进入迹地,由于较大的高生长速度和侧生长速度,油松种群的平均高度和地径高于华山松,占据了较大的垂直和水平空间。相对来说,油松和华山松高度结构和径级结构模式不同,二者均是小个体数量居多,大个体数量极少,但油松中等大小个体多于华山松。油松和华山松种群的年龄结构模式不同,油松的为单峰右偏曲线,华山松的则近似于正态分布。坡向对油松的年龄结构模式没有影响,但对华山松种群有影响。油松和华山松种群不同高度级、径级和年龄级之间存在显著正或负相关关系,缺少一致性,表明种群大小结构不一定反映年龄结构。油松和华山松种群的密度动态和存活曲线类型一致,均为Ⅱ型,表明二者具有相同的种群动态。总体上说,油松和华山松具有不同的树种生物学特性,使得种群的大小结构和年龄结构不同,但对种群更新存活动态没有影响。

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 m^2 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.