Study On Understory Vegetation Diversity And Soil Physical-chemical Properties Of Teak(Tectona Grandis L.f)Plantation

91 temporary sample plots were set in teak（Tectona grandis）plantations located in Jieyang city of Guangdong province,Hekou of Yunnan province,Mengla of Yunnan province and Hainan province for surveying the species name,quantity,height and coverage of understory vegetation,and collecting soil samples of 0-20 cm and 20-40 cm layers.Understory vegetation biodiversity and soil physical-chemical properties in different densities,ages,slope aspects the plantaitons and their correlations were studied.Site qualities were also evaluated by using method of principal component analysis in terms of biodiversity indexes and soil physical-chemical properties,which should provide theoretical basis for establishing and sustainable management of teak plantations.The main conclusions were listed as follows:（1）The results of teak plantations with different densities in Jieyang City of Guangdong Province were as follows: The Shannon-Wiener index（SWI）,Simpson index（SI）,Richness index（RI）,and Evenness index（EI）of understory vegetation showed a tendency of risings and then dropings with the increase of stand density.The soil physical-chemical properties in upper layer were superior to those in deeper layer.The capillary porosity,non-capillary porosity,available K,available P,total P,exchangeable acid and exchangeable aluminum were significant difference among the different stand densities（P < 0.05）.With the increase of stand density,the soil physical-chemical properties presented a change process from improvement to degradation.By principal component analysis,the stand density of 1 050 tree·hm-2 was more favorable to keep undergrowth species diversity and soil physical-chemical properties.There was significantly negative correlation between soil capillary porosity,total porosity and species diversity index of undergrowth in different density of teak plantation.The available P was also an important factor affact the diversity index of shrub.（2）The results of teak plantations of different ages in Hekou city of Yunnan Province were as follows: With the raise of forest age,the Shannon-Wiener index,Simpson index,Richness index,Evenness index of shrub layer,Richness index and Evenness index of herb layer showed a trend of droping after initinal increasing,and all of the index value in 20 years were the largest.Soil volumetric water content,field capacity,capillary porosity,total porosity and non-capillary porosity physical indexes increased after reduced first,and then reduced again,which was contrary to the soil density.The tendency of total K,available K,available P,total N,organic matter,exchangeable calcium,the upper exchangeable acid and cation exchange capacity of soil was raised up then droped down;According to principal component analysis,the order of the composite score of different years on species diversity and soil physical-chemical properties was: 20a>8a>13a>26a.Which indicated that site quality was best in 20 years of teak plantations.There was a significant positive correlation among the Shannon-Wiener index,Richness index and total porosity,capillary porosity in theherb layer.The Shannon-Wiener index and capillary porosity,field capacity,total P,exchangeable calcium showed a significant correlation in the shrub layer,Evenness index,Richness index and capillary porosity,field capacity,exchangeable calcium also showed a significant correlation in the shrub layer.（3）The results of teak plantations of different slope position in Mengla of Yunnan Province were as follows: From up to down of the hill,the Shannon-Wiener index,Simpson index,Richness index,and Evenness index of herb layer increased gradually,while the diversity index of shrub layer shown the opposite.The field capacity and capillary porosity fell with slope from up to down,but soil density was icreased.The value of volumetric water content,total porosity and non-capillary porosity wasranked by the slope of middle>top>down.Soil nutrients showed the upper was better than the lower.In the overall nutrient comparison: middle slope was better than upper and down slope.According to the result of principal component analysis and the growth situation of teak,middle or down slopes were suitable for teak to grow.The significant correlations were found between total K and Shannon-Wiener index,Simpson index,Richness index of herb layer in the plantation with different slope position.（4）The results of teak plantations of different sites in Hainan Province were as follows: The same species diversity index at the three sites was shown that the shrub layers were higher than the herb layer.Generally speaking,the soil physical properties of Sanya gaofeng and wuzhishan maoyang were better than sanya banlingshuiku,soil exchangeable acid,exchangeable aluminum,base saturation,exchangeable magnesium,cation exchange capacity and the available Fe²⁺/Fe³⁺ magnifested: sanya gaofeng> wuzhishan maoyang > sanya banlingshuiku.The total P,available P,total N,organic matter: sanya banlingshuiku > wuzhishan maoyang >sanya gaofeng.And exchangeable calcium,total K of up and Available Zn²⁺ down showed: wuzhishan maoyang > sanya gaofeng> sanya banlingshuiku.By comprehensive score,the wuzhishan maoyang is the better growing site for teak.Available P and Shannon-Wiener index,Richness index demonstrated a significant positive correlation.Significant negative correlations between total P and species diversity index of herb were found in teak plantation of deferent regions in Hainan.Also,soil density,volumetric water content and available P was of indication value in herb diversity.（5）There were 59 species in Jieyang of Guangdong Province,belonging to 55 genera and 39 families,66 species in Hekou of Yunnan Province,belonging to 62 genera and 39 families,and 65 species in Mengla of Yunnan Province,belonging to 63 genera and 42 families.The vegetation was most abundant in Hainan,where 87 species of plants were founded,belonging to 80 genera and 38 families.The dicotyledonous plants were dominant in the teak plantation.Mikania micrantha,Dicranopteris dichotoma,Imperata cylindrica,Microstegium vagans,Thysanolaena maxima,Flacourtia indica and Catunaregam spinosa were the sign of poor growth of teak.While Commelina communis,Polygonum chinense,Woodwardia japonica,Cyclosorus parasiticus and Garcinia oblongifolia indicated a good site for teak growth.