Effects Of Different Disturbance Types On Subtropical Forest Community Structure And Diversity

The research uses the basic principles and methods of community science and ecology,based on a comprehensive investigation of the typical types of human disturbance and community characteristics in Hefeng County,starting from the types(Residential area、Farming、Mining area、Scene and Express way)and intensity of disturbance(Gravity 、 Moderate and Slight),the effects of human disturbance on species composition,important value of dominant species,species diversity,community structure and niche of dominant species in tree layer at all levels of plant community were studied.The main research results are as follows:(1)Under the same disturbance type,the mean diameter,mean canopy height and sum of chest height and area of the community showed a similar law.The severe interference has a great influence on the mining area and express way,and the change of community structure in mining area is the most significant,the disturbing intensity has little influence on the communities of residential area,farming and scene.The individual number of tree layer mainly concentrated in small diameter class and small height class,except for farming disturbance community,the individual number of other four disturbance types increased under moderate or slight disturbance.(2)Plant communities of different disturbance types have different species composition,and the disturbing intensity changes the species composition of the community at the level of family,genus and species,reaching the maximum in moderate or slight disturbance communities.The disturbance of residential area and express way changed the basic types of communities,and the interference of farming,mining area and scene spots changed the status of the dominant species in the tree layer of the community.The dominance of the dominant species in the tree layer,such as Cunninghamia lanceolata,Liriodendron chinense,and Cryptomeria fortune decreases significantly with the reduction of the disturbing intensity in the communities of various interference types;the dominance of the shrub layer such as Camellia cuspidate,Rubus lambertianus,Weigela japonica var.sinica,and Rubus setchuenensis dominance decreased or disappeared;herb layer such as Indocalamus tessellatus,Iris japonica and Impatiens oxyanthera appeared or dominance increased.(3)The species diversity of the communities of various disturbance types,the arbor layer is farming>residential area>scene area>mining area>express way;there was no significant difference in the overall diversity of shrub layer;the species diversity of herb layer was the highest in residential area and farming disturbance communities.Affected by different disturbing intensity,the diversity index of tree,shrub and herb of each disturbance type was the highest under moderate or slight interference except scene disturbance,and the influence of severe disturbance on mining community was the greatest.The species richness,Shannon-Wiener index and Simpson index are the highest in herb layer;the Pielou index is the highest in shrub layer.(4)Studies on the niche of dominant tree populations in different interference communities show that Cunninghamia lanceolata,Castanea mollissima,Cryptomeria fortune and Rhus chinensis have larger niche breadth in the five interference communities,these species have strong adaptability to the environment and are fully utilized for resources.The niche breadth values of Liquidambar acalycina in residential area,Liriodendron chinense in mining area and Metasequoia glyptostroboides in express way disturbance under different disturbance levels were all 0,the niche spatial pattern has not undergone essential changes.More than 65 ~ 80 % of the dominant species in the tree layer of the five types of disturbance communities had niche overlap,indicating that the competition between species in the tree layer was fierce.As the disturbing intensity decreases,the niche overlap between species in the community had an increasing trend.