茂兰喀斯特森林不同地形部位优势乔木种群的生态位研究

Niche characteristics of dominant tree populations in karst forest at different topography sites in Maolan National Natural Reserve of Guizhou Province

为了解茂兰喀斯特森林优势乔木种群的生态位特征,该研究对茂兰国家级喀斯特森林自然保护区三种地形(坡地、槽谷、漏斗)进行了群落调查,并计算三种地形部位优势乔木种群的生态位宽度、生态位重叠等特征。结果表明:不同地形部位的优势乔木种群的生态位宽度Bi和Ba值的排列顺序虽稍有差异,但总体上是一致的。轮叶木姜子(Litsea verticillata)在坡地、槽谷地形中的生态位宽度较大,其Bi/Ba分别为0.782 4/0.415 7、0.891 3/0.703 0;齿叶黄皮(Clausena dunniana)在坡地、漏斗地形中有较大的生态位宽度,其Bi/Ba分别为0.788 0/0. 518 3、0. 962 7/0. 826 0。生态位重叠值(Lhi)最大的是漏斗中的朴树(Celtis sinensis)和云贵鹅耳枥(Carpinus pubescens)(0.138 2),最小的是坡地中的圆叶乌桕(Triadica rotundifolia)和巴东荚蒾(Viburnum henryi)(0.001 5)、槽谷中的轮叶木姜子和青冈(Cyclobalanopsis glauca)(0.001 5)。生态学特性和对生境需求相似的物种,生态位重叠值通常较大,反之则小;物种的生态位宽度较大,则其生态位重叠值亦较大,反之则小。这说明三种地形中群落优势种群间的生态位重叠程度较小,茂兰喀斯特森林处于稳定的顶极群落阶段,但群落内种群因环境资源有限而产生的竞争较为激烈,在不同地形生境中的竞争激烈程度表现为漏斗>槽谷>坡地,光照的差异是影响各地形部位优势乔木种群天然分布的主要因子。

In order to understand the niche characteristics of dominant tree populations in karst forest, community investigation was conducted on three topography sites (hillside, valley and funnel) in Maolan National Natural Reserve. Niche characteristics of dominant tree populations at three topography sites were analyzed by niche breadth and niche overlap formula. The results were as follows: The niche breadths B i and B a of the dominant tree populations at different topographical sites were slightly different, but overall, they were consistent. The niche breadth of Litsea verticillata in hillside and valley was larger, and its B i/B a were 0.782 4 / 0.415 7 , 0.891 3 / 0.703 0 , respectively. The niche breadth of Clausena dunniana in hillside and funnel was larger, and its B i/B a were 0.788 0 / 0.518 3 , 0.962 7 / 0.826 0 , respectively. The niche overlap between Celtis sinensis and Carpinus pubescens in funnel was the largest, being 0.138 2, while those between Viburnum henryi and Triadica rotundifolia in hillside, Litsea verticillata and Cyclobalanopsis glauca in valley were the smallest, being 0.001 5. In addition, species with similar ecological characteristics and habit requirements often had high degrees of niche overlap, species with different ecological characteristics and habit requirements often had low degrees of niche overlap. Species with wide niche breadth often had high degrees of niche overlap, species with narrow niche breadth often had low degrees of niche overlap. In a word, low degrees of niche overlap of dominant species were found at different topography sites and therefore, Maolan karst forest is in a stable climax community stage. But it suggested fierce interspecies competition among dominant species for limited environmental resources in climax community in the forest. The intensity of competition of dominant species at different topography sites is funnel> valley> hillside, light is the main factor affecting the natural distribution of dominant arbor populations.