We examined species composition, community characteristics, diversity, and community similarity of five Quercus communities composed of three Quercus species (Q. variabilis, Q. aliena var. acutiserrata, Q. wutaishanica) on the altitudinal gradient on the south and north slopes of Taibai Mountain. The results showed that there was an altitudinal transition pattern from Q. variabilis pure forest to Q. variabilis-Q. aliena var. acutiserrata mixed forest, Q. aliena var. acutiserrata pure forest, Q. aliena var. acutiserrata-Q. wutaishanica mixed forest and Q. wutaishanica pure forest on the south and north slopes of Taibai Mountain. The main companion species of Quercus community on the north slope were Pinus armandii, Castanea seguinii, and Sorbus alnifolia, and were Pinus tabuliformis, C. seguinii, Carpinus cordata, and Q. spinosa on the south slope. Species richness, woody plant density, and Quercus species dominance on the north slope of Taibai Mountain were higher than those on the south slope. α diversity of tree layer in Quercus community on the south and north slopes of Taibai Mountain increased first, then decreased and then increased with altitude. α diversity of tree layer was higher in mixed forests than pure forests. α diversity of shrub layer was higher than that of tree layer and herb layer in Quercus community on south and north slopes. β diversity fluctuated greatly along the altitudinal gradient on the south and north slopes, indicating that species composition changed greatly with altitude. Results of redundancy analysis showed that mean warmest month temperature, altitude and tree height accounted for 79.0% of the community diversity on the north slope, and that soil water content, tree height, canopy density and mean annual temperature accounted for 79.6% of the community diversity on the south slope. Overall, Quercus dominance was higher on the north slope of Taibai Mountain, and the substitution distribution pattern of Quercus species was clearer than that on the south slope. Environmental factors related to temperature and precipitation jointly affected α diversity of Quercus communities.
以秦岭主峰太白山南北坡呈替代分布的3种栎类植物(栓皮栎、锐齿槲栎和辽东栎)形成的5种栎类群落为对象,研究海拔梯度上5种栎类群落的物种组成、群落特征、多样性和群落相似性。结果表明: 随海拔的升高,太白山南北坡均呈现由栓皮栎纯林向栓皮栎-锐齿槲栎混交林、锐齿槲栎纯林、锐齿槲栎-辽东栎混交林、辽东栎纯林的过渡模式。太白山北坡栎类群落的主要伴生种为华山松、茅栗、水榆花楸,南坡栎类群落的主要伴生种为油松、茅栗、千金榆、刺叶栎。太白山北坡的物种丰富度、木本植物密度、栎类树种优势度均高于南坡。太白山南北坡栎类群落的乔木层α多样性指数随海拔升高呈升高-降低-升高的趋势,混交林的乔木层α多样性比纯林高;南北坡栎类群落的灌木层α多样性高于乔木层和草本层。南北坡栎类群落的β多样性在海拔梯度上波动较大,随海拔升高物种组成变化较大。冗余分析表明,最暖月均温、海拔、树高对北坡群落多样性的解释率达79.0%,土壤含水率、树高、郁闭度、年均温对南坡群落多样性的解释率达79.6%。整体来看,太白山北坡栎类树种的优势度更高,栎类树种的替代分布格局较南坡更加清晰,与温度和降水有关的环境因子共同影响着栎类群落的α多样性。.
Keywords: community similarity; community structure; diversity.; species composition; substitution distribution.