中文摘要：

为揭示秦岭南坡植物群落演替与物种多样性之间的复杂关系，采用空间代替时间的方法在秦岭南坡油松林、松栎混交林和锐齿栎林群落典型分布区域设置45个样地进行了群落学调查，统计分析了油松林→松栎混交林→锐齿栎林这→演替序列过程中草、灌、乔3层的物种组成和“物种多样性动态。结果表明：（1）秦岭南坡油松林、松栎混交林和锐齿栎林3种群落共有维管植物312种，隶属于73科183属，其中草本植物136种，灌木（含木质藤本）98种，乔木78种；油松林群落包含52科117属190种，松栎混交林群落含有60科95属129种，锐齿栎林群落则为50科109属178种。（2）沿油松林→松栎混交林→锐齿栎林群落演替序列，草本层物种均匀度和物种多样性显著降低，物种丰富度呈“V”形变化趋势；灌木层物种丰富度、均匀度以及物种多样性均无显著差异；乔木层物种多样性呈明显的单峰型变化，其中松栎混交林群落物种多样性指数最高。研究表明，秦岭南坡松栎林群落物种多样性随演替进展总体上呈现单峰型变化，与中期物种多样性假说一致；物种多样性可能仅仅是群落稳定的一个基础或前提条件。

英文摘要：

Species diversity and its change is one ot the mare tnutcaLu process. Our objective was to examine the complex relationships between the species diversity and commu- nity succession in the successive serials from Pinus tabuliforrnis forest to P. tabuliforrnis-Quercus aliena vat. acuteserrata mixed forest then to the subsequent Q. aliena var. acuteserrata forest on the south-facing slopes in Qinling Mountains. Changes of species composition and diversity in each vegetation stratum were studied using the method of substituting spatial difference for time change. The results showed that.. （1）312 species of vascular plants belonging to 183 genera and 73 families were recorded in 45 quadrats investiga- ted, among which there were 136 herbs, 98 shrubs encompassing woody climbers, and 78 trees. The compo- sition of the three communities was that there were 190 species belonging to 117 genera and 52 families, 129 species belonging to 95 genera and 60 families,and 178 species belonging to 109 genera and 50 families in P. tabuliformis forest, P. tabuliforrnis-Q, aliena var. acuteserrata mixed forest and Q. aliena var. acuteserrata forest,respectively. （2）Species evenness and species diversity in herb layer decreased signifi- cantly during community succession （P;0.05）, species richness showed a V-shaped trend ; shrub layer spe- cies richness,evenness and species diversity did not change conspicuously （P;0.05）;There was a signifi- cant hump-shaped pattern in species diversity in tree layer along the succession process, and the species di- versity reached a peak in the community of P. tabuliformis-Q, aliena var. acuteserrata mixed forest. The studies above indicated that.changes of species diversity presented a hump-shaped model as a whole in the process of community succession of pine oak forests on the south-facing slopes in Qinling Mountains,which agrees with the intermediate species diversity hypothesis The species diversity may simply be one of the basis or prerequisites to the community stability.