紫柏山林麝分布区植物群落乔木层结构特征

Structural characteristics of plant communities’ arbor stratum in Moschus berezovskii distribution areas in Zibaishan Nature Reserve

通过沿海拔梯度的系统取样,采用中点四分法对紫柏山北坡林麝分布区的植物群落乔木层结构特征进行了调查。结果表明:(1)根据聚类分析,可将植物群落划分为6种类型,低海拔地带2种,即锐齿槲栎林和锐齿槲栎+川鄂鹅耳枥+白桦林;中海拔地带4种,即铁橡树林、铁橡树+川鄂鹅耳枥林、米心树+坚桦林和坚桦林;高海拔地带1种,即坚桦林;(2)海拔从低到高,优势科逐渐从壳斗科向桦木科转变,优势属从栎属向桦木属转变;(3)随着海拔升高,乔木胸径显著增加,乔木密度则呈下降趋势;中海拔林段物种丰富度、多样性、均匀度最高,物种优势度最低,低海拔林段相反;(4)低海拔地段小径级(DBH<12cm)个体居多,随着海拔升高大径级个体比例(DBH≥24cm)逐步增大。

Through a systematic survey along altitudinal gradient and by using point-centered quarter method, this paper studied the structural characteristics of plant communities＇ arbor stratum in Moschus berezovskii distribution areas in Zibaishan Nature Reserve located in the Fengxian County of Shaanxi Province. According to cluster analysis, the plant communities could be classified into six types, i. e. , Quercus aliena and Q. aliena ＋ Carpinus henryan ＋ Betula platyphylla at low altitude （1 300-1 700 m）, Q. spinosa, Q. spinosa ＋ C. henryan, Fagus engleriana ＋ B. chinensis and B. chinensis at medium altitude （ 1 700 - 2 050 m）, and B. chinensis at high altitude （2 050- 2 300 m）. With increasing altitude, Fagaceae was gradually replaced by Betulaceae as the dominant family, Quercus was substituted by Betula as the dominant genera, and the diameter at breast height （DBH） of the arbors tended to increase while their density inclined to decrease. The arbor species at medium altitude had the highest richness, diversity and evenness indices and the lowest dominance index, while those at low altitude were in adverse. At low altitude, the individuals with DBH less than 12 cm were dominant, but with increasing alti- tude, the proportions of those with larger DBH （ ≥12 cm） increased gradually.