Research On Effects About Thinning Of Larix Principis-rupprechtii Mayr.Plantation In Guandi Moutain

Larix principis-rupprechtii plantation is one of the main afforestation tree species in humid and sub-humid warm temperate climate zone in China.It is important to study thinning from the aspect of sustainable management for Larix principis-rupprechtii plantation.Accord to trees grow,understory vegetation,soil property,roots to find the best management densities content.In2007,four treatment of different thinning intensities were carried out on the20-year-old Larix principis-rupprechhii plantation-through the short term record and long period observation,the result showed:(1) After thinning,the DBH and individual volume of Larix principis-rupprechtii plantation was growing quickly at the certain site and thinning densinities.The tree ring index showed that the DBH was prompted by different thinning densinities.From the long period observation,the height was related whin thinning.It was no obviously correlated between the stock volume and thinning.But after thinning,the stock volume annual growth and annual growth rate was growing quickly.The heavy thinning was the best one.(2) The herb and shrub species were changed after thinning.Lonicera japonica Thunb,Lespedeza bicolor Turcz.,Spiraea pubescens Turcz and so on were appeared in shrub.Scutellaria baicalensis, Vicia unijuga A.Br and so on were appeared in herb Acer ginnala,Daphne giraldii and so on were disappeared in shrub.Maianthemum bifolium,Cardamine leucantha and so on were disappeared in herb.At the same time,importance value was changed of understory after thinning.The species of importance values of understory shrub was positive correlativity with thinning intensity included:Spiraea trilobata,Rosa davurica Pall etal16species.The species of importance values of understory shrub was maintaining stability included:Betulaceae platyphylla SukQuercus wutaishanica Blume.Crataegus pinnatifida Bge etal5species.he species of importance values of understory shrub was negative correlativity with thinning intensity included:Daphne giraldii.The species of importance values of understory herb was positive correlativity with thinning intensity included:Thalictrum petaloideum L.etal14species.The species of importance values of understory herb was negative correlativity with thinning intensity included:Sanguisorba officinalis L,Maianthemum bifolium etal10species. After thinning1 year,3years,6years,the Simpson diversity index,Shannon-Wiener diversity index,Jsw eveness index with the increase of thinning intensities was increased slightly.In the same thinning intensity polt,the Simpson diversity index,Shannon-Wiener diversity index,Jsw eveness index showed:6years>3years>l year.(3) The soil fertility was improved after thinning,and influenced spatial heterogeneity.The soil PH was increased by1.92%,3.21%,4.61%,however,the soil moisture was decreased by0.15%,3.7%,11.6%. In different thinning intensity,the soil NH4+-N was increased by0.43%,8.66%,29.43%,and the soil NO3--N was increased by40.4%,184.6%,198.8%.The comparison with same layer in different plot,there is a significant different between thinning plot and contrast plot in0-10cm soil layers.The soil fertility of spatial heterogeneous was influenced differently by thinning.The response of thinning was the most significant in soil moisture spatial heterogeneous of0-10cm layers.The soil NH4+-N and Total N had different regular:the different soil layer of spatial heterogeneous in NH4+-N was positive correlativity with thinning intensity and spatial heterogeneous in Total N was negative correlativity with thinning intensity.(4)The root of Larix principis-rupprechtii Mayr.Plantation was influenced with forest stand which improved by thinning. With the forest density growing, the biomass of fine root had parabolic development in0-20cm soil layers. The biomass of fine root was the most biggest when the forest density was3750s/hm2.The fine root length was significant positive correlativity with stock intensity in0-20cm soil layers.