Characteristic Of Nitrogen Utilization And Effects To Mulching Management Of Phyllostachys Violascens

Phyllostachys violascens,one of high quality and high-yield shoot use bamboo species with a long shooting period from May to October,has great value for plantting and extension,which was planted in large area of Zhejiang,Jiangsu and Jiangxi.Since 1990 s,the mulchment with heavier winter forest mulching plus fertilization was popularization and application,which significantly improved the economic benefits,but followed by degeneration.In order to demenstrate the physiological and ecologival response of Phyllostachys violascens,and provide theoretical basis for promoting plant,based on a pot experiment with five different nitrogen fertilizers additions,which ratios of NO₃^--N and NH₄⁺-N were 1:0,2:1,1:1,1:2,0:1,to analyzed the effects of nitrogen forms and ratios on physiological metabolism and nutrient absorption.In addition,Taking different years of mulching management Phyllostachys violascens stands as objects,soil nitrogen contents,nitrification and denitrification were investigated.The main results were showed as follows:1 Effects of nitrogen forms and ratios on photosynthetic characters and main enzyme activities in nitrogen metabolism of Phyllostachys violascensBased on a pot experiment with five different nitrogen fertilizer additions,which ratios of NO₃^--N and NH₄⁺-N were 1:0,2:1,1:1,1:2,0:1,show that under the same levels of nitrogen application,with NH₄⁺-N proportion increasing,the content of photosynthetic pigment firstly rose and then fell;under the treatment of ammonium Nitrate ratio with 1: 2 it was significantly higher than the other treatments;while Ci variation was opposite,for treatment of ammonium nitrate ratio with 1:2 it was significantly lower than the other treatments;meanwhile activitives of NR,GS showed a trend which firstly went up and then down with increasing concentrations of NH₄⁺-N.Additionally there was no significant difference amone the performance of mixed nutrition,which might mean both nutritional treatments were higher than a single nitrogen form.Based on the analysis it might be concluded that Phyllostachys violascens was a kind of slightly-pro-ammonium plant,and mixed nutrition with ammonium nitrate was helpful for leaf photosynthesis and nitrogen assimilation.2 Effects of nitrogen forms and ratios on antioxidant system of Phyllostachys violascensUnder same treated condition of ratio of NO₃^--N and NH₄⁺-N,the content of MDA,soluble protein and activities of autioxidant enzyme were higher in leaves than roots,it is feasible that leaves had more sensitive response for nitrogen forms.With the concentration of NH₄⁺-N increasing,the content of MDA in leaves and roots decreased firstly and increased subsequently,reached the lowest level in the ratio of NO₃^--N and NH₄⁺-N was 1:1.Activities of autioxidant enzyme increased firstly and then decreased generally,and which in mixotrophism were higher.And SOD and CAT activities in leaves reached highest in the 1:2 ratio of NO₃^--N and NH₄⁺-N,SOD activity in roots reached highest in the 1:1 ratio of NO₃^--N and NH₄⁺-N,CAT and POD activities reached highest in the 1:2 ratio of NO₃^--N and NH₄⁺-N.The content of soluble protein also increased firstly and then decreased,which in leaves and roots reached highest in 1:2 and 1:1 ratio of NO₃^--N and NH₄⁺-N.In mixed nutrition,the content of MDA was lower,the content of soluble protein and activities of autioxidant enzyme kept at much higher level,therefor the degree of oxidative stress was comparatively low,resistance was stronger.It is concluded that under the mixture of NO₃^--N and NH₄⁺-N at the ratio of 1:1,the degree of oxidative damage of leaves and roots of Phyllostachys violascens is least,and autioxidant enzyme activities are stronger,is able to boost growth and biomass accumlction of Phyllostachys violascens.3 Effects of nitrogen forms and ratios on nutrient stoichiometric characteristics of Phyllostachys violascensUnder the same levels of nitrogen application,different forms of nitrogen had no significant effect on C content of leaves or fine roots,but significantly influenced stoichiometric characteristics of C,N,P and allometric relationship among C,N,P of Phyllostachys violascens.With NH₄⁺-N proportion in nitrogen supply increasing,C content of leaves and fine roots was not significantly changed?p<0.05?.The variation of N and P content both followed a shape of inverted-V,which were higher at ratio of 1:1 and 1:2.C:N,C:P and N:P in leaves and fine roots decreased with increasing NO₃^--N : NH₄⁺-N ratio,indicated the increasing growth rate of leaves and fine roots;the SMA slope for N vs C and N vs P in leaves and fine roots also followed a shape of inverted-V,which increased significantly at NO₃^--N : NH₄⁺-N ratio of 1:1 and 1:2,indicated that more content of C,P would accumulate at both ratios.4 Effects of temporal-spatial variation of soil nitrogen content of Phyllostachys violascens under mulching managementBased on soil ammonium and nitrate contents,nitrate ammonium ratio of different mulching for one year,three year,five year and non-mulching,the contents of soil ammonium and nitrate and nitrate ammonium ratio had an obvious seasonal variation.The trend of soil ammonium and nitrate contents both decreased firstly and then increased,ammonium content was highest in January and lowest in July,nitrate content was highest in January and lowest in April.The trend of nitrate ammonium ratio increased at first and then decreased.With the increasing of soil depth,soil ammonium content showed a decreasing trend of surface-aggregation;Nitrate content in the short-term mulching of Phyllostachys violascens stand showed bottom accumulation,which mulched of 3 years and 5 years showed surface-aggregation;Compared with non-mulching,soil nitrate ammonium ratio in short-term mulched stand was gradually increasing,nitrate was the main forms,and mulched of 3 years and 5 years increased the proportion of ammonium,forming “eutrophication habitat” with more ammonium.5 Effects of mulching management on soil nitrification and denitrification in Phyllostachys violascens standsBased on soil nitrification and denitrification rate of different mulching years in Phyllostachys violascens stands,showed that different mulchment years and seasons had significant effects on the soil nitrification rate of Phyllostachys violascens stands,and the period mulching with seasonal significant interactions.With the increase of the years mulching,soil nitrification rate gradually decreased every season.In addition,the correlation between soil nitrification rate and nitrogen source decreased,but the correlation between organic matter and physical factors showed an increasing trend.The main physical factors affecting the nitrification rate of the soil in the forest were diversified.Soil denitrification rate in different seasons did not change significantly,only in July and September showed soil denitrification rate with mulched five years was significantly higher than other treatments,with long mulchment denitrification showed increasing trend,increasing nitrogen loss.6 Effects of mulching on soil nitrification and denitrification in Phyllostachys violascens standsBoth mulching and covering duration had a significant impact on nitrification and denitrification,and these two factors interacted with each other.Mulching enhanced denitrification,but prolonged mulching inhibited nitrification.In general,mulching reduced the correlation between the rates of nitrification and denitrification and soil physicochemical properties.Meanwhile,it diversified and complicated the major environmental factors on nitrification and denitrification.Our results suggest that mulching could affect soil nitrogen cycling processes in the Phyllostachys violascens stand,increasing nitrogen loss in the soil.7 Effects of mulching on nitrogen translotation in Phyllostachys violascens standsMulching promoted the absorption and utilization of the nitrogen fertilizer of Phyllostachys violascens,and reduced the transmission of the nitrogen nutrient to a certain extent,that is,the physiological integration function of the nutrient in Phyllostachys violascens was weakened.Experimental research on the background and the background of the soil nitrogen literacy of Phyllostachys violascens and the cloning and fragmentatio-n of the underground stem may have a significant effect on the physiological function of nutrients.