Effects Of Site Conditions On Phyllostachys Pubescens Seedling Plantations

This work was conducted to study the Phyllostachys pubescens seedling plantations with major objectives for the relationship between stand growth and site factors to determine its suitable site types.By field survey of the sample plots,the relationship between the site factors and stand biomass were analysed.The main results of the research were as follows.1.The mean DBH,mean height,bamboo stocking index and mean density in the 5 plots of the Phyllostachys pubescens plantations was 8.6 cm,11.2 m,0.31 and 4360 culms/hm2,respectively.The bamboo densities of the 5 sample plots were between 2933 to 6080 culms/hm2.80% of the sample plots surveyed were middle-yield stands and their bamboo stocking indices were between 0.32 and 0.40.2.The stand biomass in the 5 plots was ranked as Plot 5 > Plot 1 > Plot 4 > Plot 3 > Plot 2 and their mean biomass partitioning showed no difference with the order of culm > roots > branch > foliage.The total mean biomass was 61.65 t·hm-2.3.The mean moisture contents of the different organs ranged from 32.41% to 53.45% with higher moisture content in the underground part than in the overground part.The mean concentrations of N,P,K,Ca and Mg in the organs ranked by leaves > branches > culm.The nutrient contents were ordered as N > K > Mg > Ca > P in leaves,as K > N > Mg > P > Ca in branches and roots,and as N > K > Mg > P > Ca inculms.The contents of N and K were much higher than those of P,Ca and Mg in all the organs.4.The content of the total organic carbon ranged from 44.722 to 86.990 mg·kg-1 in 0-20 cm soil layer and from 47.483 to 83.880 mg·kg-1 in 21-40 cm soil layer.The ratio of C/N ranged from 6.378 to 7.684 in 0-20 cm soil layer and from 3.428 to 8.38 in 21-40 cm soil layer.The mean of the total organic carbon?TOC?in the sampling plots was ordered as Plot 2 > Plot 1 > Plot 5 > Plot 3 > Plot 4.In 0-20 cm soil layer,the order of total N content was ranked as Plot 5 > Plot 3 > Plot 4 > Plot 2 > Plot 1;for total P was as Plot 4 > Plot 1 > Plot 5 > Plot 2 > Plot 3;total K was as Plot 1 > Plot 2 > Plot 4 > Plot 3 > Plot 5;total Ca was as Plot 2 > Plot 4 > Plot 3 > Plot 5 > Plot 1;and total Mg was as Plot 4 > Plot 5 > Plot 3 > Plot 2 > Plot 1.The mean total content was ordered by N > K > P > Ca > Mg.In 21-40 cm soil layer,the total N content was ordered by Plot 5 > Plot 3 > Plot 2 > Plot 1 > Plot 4;total P was by Plot 3 > Plot 2 > Plot 5 > Plot 4 > Plot 1;total K by Plot 1 > Plot 4 > Plot 2 > Plot 3 > Plot 5;total Ca by Plot 2 > Plot 5 > Plot 4 > Plot 3 > Plot 1;total Mg by Plot 5 > Plot 4 > Plot 3 > Plot 2 > Plot 1.For the mean available nutrient contents,the order was ranked as NO₃^--N > > NH₄⁺-N > available P in 0-20 cm soil layer while was NH₄⁺-N > available P > NO₃^--N in 20-40 cm soil layer.5.The correlation analysis showed that satnd biomass was significantly correlated with the basal area and the culm density,and had no relation to the soil bulk density and moisture content.The main factors affecting DBH growth of Phyllostachys pubescens were soil K,Ca,Mg,NH₄⁺-N,NO₃^--N and available P contents with the correlation coefficients ranked as Ca > Mg > K > NH₄⁺-N > available P > NO₃^--N > total P > total N.However,the culm height was mainly related with total N,P,K,Ca and available P contents,the order of the correlation coefficients was total N > K > Ca > total P > available P > Mg > NO₃^--N > NH₄⁺-N.The culm stocking index was significantly correlated with all of the elements except for total P,Ca and NO₃^--N.