| Pinus massoniana is the main afforestation tree species in south China.However,most of the Pinus massoniana forest built in China are single structure pure forest,with poor diversity and stability,and are prone to soil acidification,soil fertility decline,and weakened ability to resist diseases and insect pests.Therefore,it is very important and urgent to study the mixed forest of Pinus massoniana and broad-leaved trees.Schima superba and Liquidambar formosana are fast-growing broad-leaved trees with a wide range of suitable species.Areas that can grow Pinus massoniana are also generally able to grow Schima superba and Liquidambar formosana.This study through the Lianfeng town,Liancheng county,Fujian province in 2011 to build the pure stand of Pinus massoniana(hereinafter referred to as the MC),Schima superba and Pinus massoniana mixed forest(hereinafter referred to as the MH),Liquidambar formosana and Pinus massoniana mixed forest(hereinafter referred to as the MF),Pinus massoniana,Schima superba and Liquidambar formosana mixed forest(hereinafter referred to as the MHF)and so on 5 hectares of 8 years(hereinafter referred to as the 8 a)different forest tree growth,diversity,forest stand structure,bringing layer temperature and humidity,soil physical and chemical properties,litter standing crop and undergrowth biomass for investigation and study,investigation and research results are as follows:(1)Mixed forests of Pinus massoniana and broad-leaved trees are conducive to the growth of trees,and the forest productivity of different stand types is different.The average tree height of 8a-growing MC,MH,MF and MHF mixed forests was 3.89m,4.19m,4.67m and 4.71m,respectively.The average DBH was 5.65cm,6.03cm,6.59cm and 6.61cm,respectively.Individual plant volume was 0.0057m~3,0.0067m~3,0.0089m~3and 0.0090m~3 respectively.The volume per hectare was 9.25m~3,10.83m~3,14.51m~3 and 14.94m~3.MHF>MF>MH>MC were observed in average tree height,average DBH,average timber volume per tree and volume per hectare.(2)Pinus massoniana broad-leaved mixed forest contributes to the improvement of stand structure,and there are certain differences among different stand types in stand structure.The average crown amplitudes of8a-born MC,MH,MF and MHF were 1.93m,2.15m,2.42m and 2.53m respectively.The average branch height was 0.92m,0.93m,1.12m and1.17m,respectively.The average height of irrigation layer was 0.70m,0.73m,0.84m,0.82m,and the average height of grass layer was 0.52m,0.58m,0.64m,and 0.69m,respectively.The specific laws were expressed as MHF>MF>MH>MC in the average canopy width,average branch height,average grass layer height and average irrigation layer height.(3)Pinus massoniana broad-leaved mixed forest is conducive to improving the species diversity of shrub and herb layer.The species richness index,diversity index,evenness index and dominance index of the four stand types were all reflected in the shrub layer>herb layer.Secondly,the richness index of shrub layer was MC<MH<MHF<MF.The herb layer richness index was MC<MH<MHF=MF.The diversity,evenness and dominance index of shrub layer were MC<MH<MF<MHF.The diversity,evenness and dominance index of herb layer were MC<MH<MHF<MF.To sum up,the values reflected in richness index,diversity index,evenness index and dominance index all directly indicate that the species diversity of Pinus massoniana mixed forest is better than that of Pinus massoniana pure forest.Species in the shrub and grass layer of Pinus massoniana mixed forest are more than that of Pinus massoniana pure forest,and the distribution is more uniform.(4)Pinus massoniana broad-leaved mixed forest contributes to the decrease of temperature and increase of humidity in the forest,and there are certain differences among different stand types on microclimate.8a MC,MH,MF,MHF forest temperature was 20.84?,20.09?,20.1?and19.78?;The average temperature of MH,MF and MHF in MC forests decreased by 3.60%,3.56%and 5.08%,respectively.The average humidity in MC,MH,MF and MHF forests was 61.31%,62.69%,62.9%and 63.9%,respectively.MH,MF and MHF increased by 2.26%,2.60%and 4.23%respectively as compared with the average temperature in MC forests.(5)Mixed forest of Pinus massoniana and broad-leaved tree is beneficial to improving the physicochemical properties of soil.Different mixed forest have certain differences in improving the physicochemical properties of soil,and there is a certain correlation between the physicochemical properties of soil.The average soil bulk density of8a-growing MC,MH,MF and MHF mixed forests was 1.585g/cm~3,1.525g/cm~3,1.500g/cm~3,1.495g/cm~3.The average porosity of soil was41.65%,43.63%,44.45%and 44.62%.Firstly,the soil bulk density of 0-20cm soil layer is all lower than that of the corresponding 20-40cm soil layer.Secondly,soil porosity MHF>MF>MH>MC;MC>MH>MF>MHF on soil bulk density.Thirdly,in terms of maximum and minimum moisture holding capacity,the moisture holding capacity of MHF in the 0-20cm soil layer increased by 4.38%compared with that of MC.MHF>MF>MH>MC were observed in terms of water holding capacity,indicating that mixed forest of Pinus massoniana and broad-leaved tree had a better ability to increase soil water holding capacity than MC.Fourth,the organic matter,total N,total P,total K,alkali-hydrolyzed nitrogen,rapidly available phosphorus,rapidly available potassium and other components in the 0-20cm soil layer are all greater than the corresponding values in the 20-40cm soil layer.PH shows the opposite pattern.According to the correlation analysis of soil physical and chemical properties,the factors such as soil organic matter,total nitrogen,total phosphorus,total potassium,alkali-hydrolyzed nitrogen,available phosphorus,available potassium,PH value,carbon nitrogen ratio,soil bulk density,porosity and soil water holding capacity are correlated.According to the multiple comparative analysis of SPSS,there are corresponding significant differences among different soil chemical properties.(6)Pinus massoniana broad-leaved mixed forest was beneficial to increase litter stock and undergrowth biomass.There were significant differences in litter stock,thickness and undergrowth biomass among different stand types.The laws of litter present quantity,average litter thickness,littercoverageandundergrowthbiomassare MHF>MF>MH>MC. |
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