长期复合污染胁迫下杉木林分结构变化研究

THE STRUCTURAL CHANGES OF CUNNINGHAMIA LANCEOLATA HOOK. COMMUNITY EXPOSED IN COMPOUND-POLLUTED ENVIRONMENT FOR A LONG TERM

对长期复合污染胁迫下杉木林分进行了群落调查 ,采用比较方法着重分析了群落结构和物种组成结构等方面的变化。结果表明 :长期复合污染胁迫下 ,杉木林分空间结构矮小化。其中乔木群体平均高度降低 4 1 4 m,平均胸高直径降低 3 6 9cm;杉木种群生长衰弱 ,密度降低 7株 1 0 0 m2 ,盖度减小 2 5 %。乔木群体的不良变化为林床植物的发展创造了有利的条件。灌木层密度和盖度分别增加 4 3株 1 0 0 m2 和 35 %。草本层变化不大 ,这主要是乔灌木层盖度消长的变化。大量落叶阔叶树种侵入并成功定居 ,导致污染胁迫下杉木林已由同龄纯针叶林演变为异龄针阔混交林 ,也正在向阔叶林变化。暗示这些阔叶树种是该污染区森林恢复和重建的理想树种。总体而言 ,长期的污染胁迫引起群落各层片物种多样性和均匀度增加 ,生态优势度降低 ,群落向着复杂化变化 ,表明该区长期污染胁迫有效促进了杉木林沿正向演替顺利发展。

Cunninghamia lanceolata Hook.forest exposed in compound polluted environment for long period was investigated and its structural changes were analyzed by comparative study with the normal forest in the same afforestation site,technique and time in this paper.Some interesting conclusions were drown.Under the compound polluting stress for a long term,tree layers of the forest occurred unfavorable spatial decline.Both the average height and diameter at breast height(DBH) decreased 4.14 m and 3.96 cm respectively.The density and coverage also reduced 7 stems/100 m 2 and 25% respectively.Cunninghamia lanceolata population grew weakly. Ascribing to the tree population declining,understory habitats were so profitable for shrubs that their density and coverage increased 43 stems/100 m 2 and 35% respectively.Herbs kept relative stable.To make interesting,species compositions had obvious differences,especially in tree layer.Many deciduous broadleaf trees implanted and colonized successfully, and this changed Cunninghamia lanceolata forest into uneven aged,broad and conifer leaves mixed forest from even aged and conifer pure forest,and being changed into broad leaf forest.It inferred that those broad leaf trees,including Sassafras tsumu,Lindera glauca,Quercus variabilis,Betula luminifera, Populus sp.,Symplocos sp.etc.,may be the most suitable species of restoring and reconstructing forest after Cunninghamia lanceolata forest degraded. Totally speaking,the long term stresses of compound pollution made Cunninghamia lanceolata forest have higher species diversity index and community evenness and lower ecological dominance,implying the long term stresses of compound pollution guided Cunninghamia lanceolata forest developing to complicate direction and on normal succession’s way.