| Phyllostachys praecox is the favorable bamboo species which has been chosen for decades, and mainly located at Lin'an,Yuhang,Deqing counties of Zhejiang province and some other provinces in Southeast China.From 1990,the intensive management models(massive fertilization and winter mulching) in Phyllostachys praecox stands have started and extensional widely,which inducing bamboo shoots earlier,yield higher,a better price and income for farmers.In this study,we investigated and sampled soils in the main production area of phyllostachys praecox stands,namely Sankou town.Xitianmu village and.Hengfan town in Lin'an city,choosing 1a,5a,10a,15a planting years of bamboo stands and 0a(the paddy soil nearby as the beginning soil of phyllostachys praecox stands for check).Each planting year's of soil profile was replicated 4 times.The objective of this study was to analyse the temporal and spatial variation of soil N and P along with planting years and the profile depth as well as sampling areas in phyllostachys praecox stands during last 15 years under such an intensive management,and to know the trend and proportion of some available forms of N and P to total quantity.From which we can reveal the evolution of soil fertility quality under the intensive management in Phyllostachys praecox stands, hope to provide some basis for building a harmony ecosystem among paddy rice fields, Phyllostachys praecox stands and the surrounded water.Results indicated as follows:1.With the prolonging planting years of Phyllostachys praecox stands,the soil total nitrogen (TN),alkali-hydrolyzed nitrogen(AHN) and soluble organic nitrogen(SON) content increased significantly.Because of the difference of sampling areas and time,the data varied from places to places,but the variation trend were similar.Take 0-10cm for example,soil TN increased from 1.86g/kg(1a) to 4.61g/kg(15a),data demonstrated that soil TN content in the bamboo stands of 15a would achieve 2.48 times of 1a;AHN can get 438.90mg/kg when up to 15a,even as high as 508.73mg/kg;SON also increased from 1a to 15a.There was significant difference between 10a and 15a of all nitrogen data,and the accumulation was happened at 0～20 cm soil upper layer mainly,but did not affect to 20～40 cm deep soil layer yet.Furthermore,the soil TN content decreased progressively along with the depth increasing in a profile,and the intensive management had mainly influenced the N content in the surface (0～10cm)and the sub-surface(10～20cm) layers of bamboo soil.2.Comparing with fresh soil and dry soil,SON of fresh soil was higher than the other in 0～10cm layer,but no difference in 10-20cm and 20-40cm.It reflected that the first layer with relatively much higher water content and SON,par of SON will be lost by evaporation during air drying process,while sub-soil and deep soil layer with relative lower SON and thus N lost during air drying process is not a big proportion.And the SON content was increased with increased temperature of extraction solution(10℃,30℃,60℃) and extraction time.3.With the prolonging planting years of Phyllostachys praecox stands,the soil total phosphorus (TP),available phosphorus(AP) and organic phosphorus(SOP) content increased steadily.However, before 10 years,the soil TP content was higher at surface and bottom layers,and lower in the sub-surface layer in Sankou town,and in other places was reduced gradually from surface to bottom layers.There was significant difference between 10a and 15a of AP,and the content was reduced with the soil depth,also had significant variation among every layers;The SOP content rose up with the planting years prolonging too,but there was no significant difference among 1a,5a and 10a, except 15a.And the change trend followed the soil depth was the same as AP.4.In Sankou town,the correlation between TN and OM was highly significant(r=0.958**, p＜0.01),in the three places,the correlations between AHN,OM and TN were also highly significant. In Xitianmu,SON and TN was very significant(r=0.7318**,p＜0.01),while it was significant between SON and AHN(r=0.6649*,p＜0.05).5.Phyllostachys praecox stands soil samples were analyzed with the solution 31p NMR to study the structure of soil organic P.Result revealed that inorganic orthophosphate,pyrophosphate were increased with the increase of planting years,and decreased with the prolonging soil depths. Orthophosphate monoesters were also increased with the increase of planting years and of soil depths respectively.Orthophosphate diesters and pyrophosphate content was little,they might due to the time of sampling and their unstability,which could hydrolyze easily.6.Compared the soil TN of all Phyllostachys praecox stands(1a) and of wetland paddy soil (CK),the later was higher than the former,this was the result of changing from wetland paddy fields to dry land of bamboo forest stands,but to compare with Phyllostachys praecox stands(15a),the soil TN of rose up back and one increased about 34.66%～128%.And the soil TN of Phyllostachys praecox stands(15a) was much higher than the data of State Second Soil Survey done in 1984, because of the intensive management,residual nitrogen in soil was accumulated more and more.On the meantime,an N input and output budget of intensively managed Phyllostachys praecox stand has preliminary calculated,showing that about 56%soil N was disappear,that we should improve fertilizing regimes,emphasize on the combination of higher yield,higher efficiency and ecological security,and decrease the over accumulation of N in soil or reduce the loss of N, minimize the threaten to the surrounded water quality,to build a harmony ecosystem among wetland paddy fields-Phyllostachys praecox stands-the surrounded water body.
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