采伐干扰下次生林灌木层主要树种的生态位动态

为探讨采伐干扰下的灌木层主要树种的生态适应性,用Levins、Schoener和Pianka等生态位测度公式定量分析闽北天然次生林采伐后灌木层主要树种生态位动态。结果表明:样地中黄绒润楠和刺毛杜鹃的生态位最大,属优势树种;甜槠、石栎和映山红为衰退树种,在林分生产作业中需加以保护。采伐干扰促进了灌木层主要树种的生态位释放,各树种的生态位宽度在伐后10~15 a达到峰值,随后下降,伐后20 a接近于未采伐林的生态位;各树种弱度和中度择伐的生态位宽度值约占其生态位宽度总值的50%。生态位重叠值在伐后10 a最大,随后下降,到伐后20 a趋于稳定状态。因此灌木层主要树种生态位的最优期为伐后10~15 a,最佳采伐干扰强度为弱度和中度择伐。

Effect of harvesting on niche dynamics of the main tree species in the shrub layer of a secondary forest

To explore the ecological adaptability to cutting disturbance,niche dynamics of the main tree species in the shrub layer of a natural secondary forest in northern Fujian was examined and measured using Levins,Schoener,and Pianka formulas.Results indicated that Machilus grijsii and Rhododendron championiae niches were the largest and belonged to the dominant species in the plots.Castanopsis eyrei,Lithocarpus glaber,and Rhododendron simsii were in decline,and thus need to be protected during forestry production.Cutting disturbance promoted the niche release of the main tree species in the shrub layer.The niche breadth of each tree species peaked 10-15 years after cutting,decreased,and then closed to the niche breadth of the non-cutting forest after 20 years.The niche breadth of low and middle selective cutting accounted for approximately 50%of the total niche breadth of each tree species.The maximum niche overlap occurred 10 years after cutting,decreased,and then stabilized 20 years after cutting.Therefore,the optimal niche period of the main tree species in the shrub layer is 10-15 years after cutting,and optimal cutting disturbance occurs with low and middle selective cutting intensities.