Nutrient Characteristics And Productivity Of Natural Phyllostachys Heterocycla Cv. Pubescens Forest In Xiaokeng, Southern Anhui

Phyllostachys heterocycla cv.pubescens is a kind of bamboo variety with the largest cultivated area as used for wood material and bamboo shoots.As one of the most important components of species in subtropical zone,P.heterocycla cv.pubescens play a important role on maintaining the structure,function and biodiversity in subtropical forest ecosystems.A series of specific cultivation practices have been implemented in a large scale for achieving high productivity of P.heterocycla cv.pubescens forest in China in the past decades.The major management practices of bamboo forest include top-cutting and whole bamboo harvesting and utilization,shortening harvesting rotation,loosening soil and fertilizer application,herbicide application for cleaning undergrowth instead of cutting and so on.These implementation of management practices have brought us a high economic outputs in a relevant short term.But,on the other hand,the natural P.heterocycla cv. pubescens forest ecosystems have been heavily disturbed by the frequently strong management practices.Along with the intensive farming,the P.heterocycla cv.pubescens forest productivity is decline in china.To realize the sustainable management of P. heterocycla cv.pubescens forest and to provide theoretical basis for fertilization practice, this project carried through systematic research on productivity and nutrient dynamic of P. heterocycla cv.pubescens forest in Xiaokeng.The results are following:(1) The mean DBH,mean density,mean height,mean Basal area,and mean AGS of natural P.heterocycla cv.pubescens forest in Xiaokeng were,respectively,10.99cm, 3042culms/hm²,13.32m,29.28m²/hm²,and0.37.(2) The total mean biomass of the natural P.heterocycla cv.pubescens forest was 91.91t/hm²,of which 72.26t for up-ground,19.65t for under-ground.The biomass partition was ordered as stem(53.62%)＞foliage(14.77%)＞rhizome(11.63%)＞twig(10.23%)＞root(9.75%).(3) The contents of N,P,K,Ca,Mg,Na were the greatest in foliage than in other components.The ranks of the nutrient contents in the different components were as follows, N:foliage＞rhizome＞root＞stem＞twig;P:foliage＞rhizome＞twig＞root＞stem;K: foliage＞root＞rhizome＞twig＞stem;Ca:foliage＞rhizome＞stem＞root＞twig;Mg: foliage＞root＞twig＞stem＞rhizome;Na:foliage＞root＞rhizome＞twig＞stem.The nutrient contents in the same component was ranked N＞Ca＞K＞Mg＞P＞Na in foliage; Ca＞K＞N＞Na＞P＞Mg in twig;Ca＞N＞K＞Na＞Mg＞P in stem;Ca＞N＞K＞Na＞ P＞Mg in rhizome;and Ca＞N＞K＞Na＞Mg＞P in root.(4) The mean storages of N,P,K,Ca,Mg,Na in the natural P.heterocycla cv.pubescens forest were,respectively,653.280kg/hm² for N,69.929kg/hm² for P,423.446kg/hm² for K, 1459.512kg/hm² for Ca,84.600kg/hm² for Mg,122.202kg/hm² for Na.The total N,P,K, Ca,Mg,Na storages was ordered as Ca＞N＞K＞Na＞Mg＞P.(5) The Contents of total N,P and K in A₀,A and 13 horizons were significantly different amongst bamboo stands.The value of CV(%) was distinctly higher for total P than for total N and K.Result from the regression analysis indicates that the stand productivity was significantly correlated with soil total N and P.There existed significant relationships between productivity index and total K in A horizon(p＜0.05).Except for density,all productivity index was significantly correlated with the total P contents of A and B horizons(p＜0.05).(6) The seasonal changes of N,P,K,Ca,Mg,Na contents in foliage of P.heterocycla cv. pubescens were following.The changeable range of N content lied between 0.03 to 4.23g/kg with the maximum occurred in winter and minimum in spring.The changeable range of P content lied between 0.02 to 0.41g/kg.The maximum content of P occurred in winter while the minimum appeared in spring.The peak value of K content occurred in summer with small variation in the other seasons.The minimal content of Ca appeared in winter while the maximum occurred in spring.The changeable range of Mg content lied between 0.02 to 0.29g/kg with the minimum in summer.The changeable range of Na content lies between 0.02 to 0.18g/kg with the peak value occurred in summer.Ca content of foliage in different seasons(fall,spring,winter) showed relative stability.(7) The seasonal changes of N,P,K,Ca,Mg,Na contents in root were as following.The changeable range of N content lied between 0.35 to 1.96g/kg with the maximum occurred in summer.The peak value of P content occurred in winter.The content of K in fall was close to that in summer.The content of K in winter was close to that in spring.The peak content of Ca occurred in winter while the minimal content appeared in spring.The changeable range of Mg content lied between 0.04 to 0.35g/kg with the minimum appeared in winter.The content of Ca in different seasons showed relative stability.