The Study Of Plant Species Diversity And Niche Of Dominant Of Low-beneficial Cypress Forests Under Different Transformation Models

The reconstructions of artificial forest always bring changes of biotope,those changes will reflect in plant diversity and community relations.Cupressus funebris low efficiency stands is the main forest type in Sichuan basin hilly region,the growth status of Cupressus funebris is poor and soil erosion is severest.It is necessary to adjust forest structure.In order to provide theoretical basis for Cupressus funebris low efficiency stands reconstruction,11reconstructing patterns after 4 years were selected as research object.We studied the plant diversity,niche characteristics of herbs and shrubs,chemical and physical properties of soil,to revealed the changes of plant diversity,ecological laws including plant community structure,utilization of resources and interspecific competition,the effects of reconstruction on soil structure,moisture and nutrient.Pure forest patterns of Cinnamomum septentrionale,Alnus cremastogyne,Toona sinensis,mixed patterns of Cinnamomum septentrionale + Alnus cremastogyne,Cinnamomum septentrionale+ Toona sinensis,Toona sinensis + Alnus cremastogyne,Cinnamomum septentrionale + Alnus cremastogyne + Toona sinensis,the cutting-blank were selected as the research object and pure Cupressus funebris forest as contrast.The pure forest patterns has two densities,the planting spacing of high density is 1.5m×2m while low density is 1.5m×4m,planting spacing of mixed patterns is 1.5m×2m,The results were found as follows:(1)For herbaceous layer,the Shannon-Wiener index,Simpson index,Pielou index and richness index of reconstructing patterns are all higher than pure Cupressus funebris forest(1.48,0.69,0.82 and 1.27)except pure Toona sinensispattern(1.30,0.65,0.72,1.15 and 1.19,0.65,0.86,0.66),low density pure Cinnamomum septentrionalepattern(1.48,0.76,0.92 and 0.85)and Cinnamomum septentrionale + Alnus cremastogyne + Toona sinensispattern(1.44,0.72,0.81 and 1.12).Among all reconstructing patterns,the biological diversities of mixed patterns of Cinnamomum septentrionale + Toona sinensis(1.83,0.83,0.94 and 1.30)and Alnus cremastogyne+ Toona sinensis(1.82,0.83,0.93 and 1.33)were significantly higher than pure Cupressus funebris forest,these two patterns are the relatively optimal reconstruction types.For shrub layer,the biological diversities of all reconstructing pattern types are higher than pure Cupressus funebris forest(1.37,0.70,0.97 and 0.85).Among those reconstructing patterns,the mixed patterns of Cinnamomum septentrionale + Alnus cremastogyne(2.12,0.80,0.77 and 2.43),Toona sinensis +Alnus cremastogyne(1.95,0.82,0.81 and 2.18),Cinnamomum septentrionale + Toona sinensis(1.95,0.80,0.78 and 1.96)have the better reconstructive effect.The biological diversities of shrub layer were higher than herbaceous layer,which means the succession is more centralized in shrub communities.(2)For herbaceous layer,the Adiantum capillus-veneris had the widest niche breadths(2.365)before the reconstruction,and the ombrophytes were in the dominant position.After the reconstruction,the light condition and soil properties of the undergrowth had been changed,heliophytes like Miscanthus floridulus had occupied the living space quickly in low density pure forest patterns.With forest canopy density increased,ombrophytes like Carex tristachya,Ficus tikoua,Oplismenus compositus and Duchesnea indica have occupied the dominant position again.For shrub layer,the Myrsine africana had the widest niche breadths(1.357)before,after reconstruction,the canopy density of arborous layer have been reduced significantly.The Broussonetia papyrifera start to occupied the dominant position in reconstructing patterns.With the increase of canopy density,the Shade-enduring plants like Vitex negundo,Myrsine Africana andElaeagnus pungens play an important role in shrub communities again.(3)The niche breadth values were significant positively correlated with importance values(r=0.7641)and resource-niche(0.9635).Its means the plant which has a wide niche breadth value always has a high importance value and has more resource-niche.The relation between niche breadth and resource-niche is more related.(4)The niche overlap is not concerned with niche breadth,species which had wide niche breadth both had high and low niche overlap value.In general,the niche overlap values among herbaceous and shrub populations were low,but the niche overlap of shrub layer is higher than herb layer.It means the niche differentiation was obvious and interspecific competition was not fierce in herb layer.This may be associated with the short time reconstruction.But the succession is more centralized in shrub layer,it causes a certain degree of competition.(5)The soil physical properties of reconstructing patterns are as follows:Except low density pure Cinnamomum septentrionale pattern,the other patterns are all better than pure Cupressus funebris forest.Those reconstructing patterns increased the soil moisture content and reduced the soil compactness,makes soil more beneficial to the growth of vegetation.The mixed patterns of Cinnamomum septentrionale + Alnus cremastogyne and Cinnamomum septentrionale + Toona sinensis,the high density pure Alnus cremastogyne pattern are better to improvement the soil.The soil chemistry properties of reconstructing patterns are as follows:The reconstructing patterns for improved soil pH value,total P,total K is not obvious or even declined,but for increase the content of total N,hydrolyzable N,available P,available K and organic matter is remarkable.In all those patterns,mixed patterns of Cinnamomum septentrionale + Alnus cremastogyne,Cinnamomum septentrionale + Toona sinensis,Toona sinensis + Alnus cremastogyne have the better reforestation effect.(6)The correlation between soil physical properties and plant diversity is higher than soil chemistry properties.This means the soil physical properties are the main influence factors of plant diversity.