平潭岛台湾相思与黑松不同混交林林下物种多样性与土壤理化性质的关系

Relationship Between Species Diversity and Soil Physicochemical Properties in Different Mixed Forests of Acacia confusa and Pinus thunbergii on Pingtan Island

林下植物多样性和土壤理化性质是反映水土保持稳定性和生长力的关键指标。该研究以平潭岛的5种典型林分类型:Ⅰ.台湾相思(Acacia confusat)林、Ⅱ.黑松(Pinus thunbergii)林、Ⅲ.台湾相思+木麻黄(A.confusa+Casuarina equisetifolia)林、Ⅳ.黑松+台湾相思(P.thunbergii+A.confusa)林和Ⅴ.黑松+滨柃(P.thunbergii+Eurya emarginata)林为例,分析不同林分类型的林下物种多样性与土壤理化因子的差异性,通过冗余分析探讨土壤理化性质与林下物种多样性之间的相互关系。结果表明,黑松+台湾相思混合种植更有利于丰富林下物种多样性,台湾相思+木麻黄植物群落结构简单,物种多样性水平低下。不同混交类型土壤的理化性质不同,相对纯林而言,树种混交有利于提高土壤全钾含量,台湾相思与木麻黄混合种植有利于提高有机质、全氮、碱解氮和有效磷含量。土壤全钾和水溶性盐总量对林下物种多样性影响最大,全钾与灌木层和草本层的物种多样性指数均呈负相关;水溶性盐总量与灌木层物种多样性指数呈正相关,与草本层物种多样性指数呈负相关。因此,在今后混交林的营造模式上,为提高林下物种多样性可以考虑黑松+台湾相思的混合种植;在提高土壤肥力上考虑台湾相思+木麻黄、黑松+台湾相思混合种植;同时通过人为抚育间伐和补植等措施进行树种协调,降低木麻黄化感作用,并控制土壤全钾和水溶性盐总量,促进群落长期稳定发展。

Understory plant diversity and soil physicochemical properties are the key indicators of soil and water conservation stability and growth ability.Five typical stand types on Pingtan Island were selected,including Acacia confusa forest(I),Pinus thunbergii forest(II),A.confusa+Casuarina equisetifolia forest(III),P.thunbergii+A.confusa forest(IV)and P.thunbergii+Eurya emarginata forest(V),the differences of understory plant diversity and soil physicochemical properties in different stand types were analyzed,and explored their relationships through redundancy analysis(RDA).The results showed that the mixed forest of P.thunbergii+A.confusa was more beneficial to enrich the species diversity in the understory,while the community structure of A.confuse+C.equisetifolia forest was simple with low species diversity.The soil physicochemical properties of different mixed forests were different.Compared with pure forest,the mixed planting of tree species was beneficial to increase the total potassium content of soil,and A.confuse+C.equisetifolia and P.thunbergii+E.emarginata forest were beneficial to enhance soil organic matter content,total nitrogen,alkali-hydrolytic nitrogen and available phosphorus.Soil total K and water soluble salt had the greatest influence on species diversity in understory,and total K was negatively correlated with species diversity index in shrub layer and herbaceous layer.The total water soluble salt was positively correlated with the species diversity index of shrub layer and negatively correlated with the species diversity index of herbaceous layer.Therefore,in order to improve the species diversity of the understory,the mixed planting of P.thunbergii+A.confusa could be considered.To improve soil fertility,mixed planting of A.confusa+Casuarina equisetifolia,P.thunbergii+A.confuse could be considered.At the same time,tree species coordination was carried out through artificial tending,thinning and replanting,so as to reduce allelopathy of Casuarina equisetifolia,control total potassium and water soluble salt content in soil for promote long-term stable development of community.