鄂西南木林子常绿落叶阔叶混交林恢复过程中优势树种生态位动态

运用Shannow-wiener生态位宽度指数和Pianka生态位重叠指数,分析了鄂西南木林子常绿落叶阔叶混交林恢复过程中优势树种生态位动态。结果表明:大穗鹅耳枥(Carpinus fargesii)、四照花(Cornus kousa var.Chinensis)、青冈(Cycloblanopsis glauca)生态位总宽度较大,且在5个不同恢复时期均有分布。恢复期14a、35a、60a、85a和110a生态位宽度最大的树种分别为白马桑(Weigela japonica var.sinica)、大穗鹅耳枥、四照花、光皮桦(Betula luminifera)和尾叶冬青(Ilex wilsonii)。随着群落的恢复,优势落叶树种生态位宽度表现出下降趋势,优势常绿树种则呈上升趋势。当恢复到顶极群落阶段,乔木层常绿和落叶树种生态位接近,灌木层常绿灌木占据较大生态位。随着群落的恢复,优势落叶树种与其它树种的生态位重叠值呈波动性下降趋势,优势常绿树种表现为波动性上升趋势,群落全部树种间生态位重叠程度呈小幅度波动性下降趋势。相同或相似生活型的演替早期种间的高生态位重叠,意味着种间对资源利用的相似性和竞争关系,演替后期种与其它树种间的生态位重叠的增加,意味着不同生活型树种在水平空间重叠而在垂直空间分化,这是不同树种对有限环境资源充分利用的一种机制。

Niche dynamics during restoration process for the dominant tree species in montane mixed evergreen and deciduous broadleaved forests at Mulinzi of southwest Hubei

The niche dynamics during natural restoration process of dominant tree species in montane mixed evergreen and deciduous broadleaved forests at Mulinzi of Southwest Hubei were analyzed by means of Shannow-wiener niche breadth index and Pianka niche overlap index. The results showed that the total breadth of niche of Carpinus fargesii, Cornus kousa var. Chinensis and Cycloblanopsis glauca were higher and theses tree species were found in all five restoration stages. Weigela japonica var. sinica, Carpinus fargesii, Cornus kousa var. Chinensis, Betula luminifera and Ilex wilsonii were the species with the largest niche breadth for the restoration stage of 14, 35, 60, 85 and 110 years respectively. There was a general trend that the niche breadth of dominant deciduous tree species decreased with increasing degree of community restoration, while that of dominant evergreen tree species was on the contrary. When the community restored to its climax stage, the niche of evergreen species in tree layer was close to that of deciduous trees, and that of evergreen species in shrub layer occupied a larger niche; this was a spatial pattern for better sharing of natural resources. With increasing restoration degree of community, the niche overlap between dominant deciduous tree species and other tree species had a trend of fluctuant decrease; while that of dominant evergreen tree species had a trend of fluctuant increase; and the niche overlap among all tree species in communities had a tendency of slightly waved decrease. The results showed that higher niche overlap among the early-succession species with same or similar life form meant a similar or competing requirement on resources. The increase of niche overlap among the late-succession species and other tree species represented a horizontally spatial overlap but vertically spatial differentiation; this is a full use mechanism of different tree species regarding limited resources in their environment.