Responses To Simulated Nitrogen Deposition Of Different Ages Of Eucalyptus Dunnii Young Growth

In the past few decades,human activities such as fossil fuel combustion,fertilizer production and use and intensive management of animal husbandry,et al make many nitride emissions to the atmospheric.Nitrides cause accumulation in the atmosphere then settling to terrestrial and aquatic ecosystems,especially since the 20th century,70s,acid deposition in industrialized countries such as Europe and America has become an important environmental problems;The most important implication of Nitrogen deposition on forest ecosystems is to speed up the trees,forest soil and litter nutrient leaching,thus changing the system of biogeochemical cycles;With the rapid economic development,Southern China after Europe and the United States has become the third largest acid deposition areas,nitrogen deposition on forest ecosystems have been affected by more and more attention.The current atmospheric nitrogen deposition on broad-leaved forest and forest soil,as well as the impact and feedback of litter decomposition has been reported rarely.E.dunnii is a major economic tree species in Fujian region,so to clarify the feedback and negative feedback mechanism between nitrogen deposition and E.dunnii plantation stands,which can help provide a theoretical foundation for nitrogen deposition on forest ecosystems as well as a theoretical foundation for sustainable forest management.The experiment designed four levels of nitrogen treatment:N0(0kg ? hm-2 ? a-1),N1(40kg ? hm-2 ? a-1),N2(80kg ? hm-2 ? a-1),N3(120kg ? hm-2 ? a-1),repeat three times for each treatment to study the impact of nitrogen deposition on growth,soil nutrients,tree nutrients and litter decomposition of different ages of Eucalyptus dunnii,The main findings were as follows:1 The effects of simulated nitrogen deposition on tree growth of different age of young growth E.dunnii:Throughout the experimental process,the level treatment E.dunnii young growth tree height, diameter at breast height quarter growth rate of the overall trends are as follows:first reduced then increased.After one year experiment we found that high concentrations of nitrogen deposition inhabit the growth of diameter at breast height,and 2-N2 treatment was the largest diameter at breast height growth of 45.55 percent.All nitrogen treatment promoted the the tree height growth, and 2-N1 treatment was the greatest degree of tree height growth of 43.83 percent2 The effects of simulated nitrogen deposition on soil nutrients of different age of young growth E.dunnii:With the same nitrogen treatment in the same period,the content of total nitrogen in forest soils are showed the same rule as follows:upper＞middle＞lower;at the same soil layer and the same nitrogen deposition level,the content of total nitrogen increased with the treatment time extended;on the same period,the content of total nitrogen of forest soil hoist with the concentration treatment increased.The same nitrogen treatment in the same period of the organic carbon content of the upper soil layer was significantly higher than the middle and lower soil layer organic carbon content;with the same nitrogen treatment on the same soil layer,the soil organic carbon content reduced with the treatment time extended;the same period in the same layer of soil organic carbon content reduced with the concentration treatment increased.The same nitrogen treatment on the same soil layer of soil C/N reduced with the treatment time increased;the same period on the same soil layer of soil C/N decreased with the treatment concentration increased;the same nitrogen treatment in the same period,except the sampe of July 2007 on 2-N3 trearment,October 2007 on 2-N2 trearment,April 2008 on 2-N3 trearment and January 2008 on the 3-N0 treatment,other samples were showed as follows:the upper soil C/N higher than the middle and lower soil layer.The same nitrogen treatment in the same period,the upper soil available phosphorus content was significantly higher than the middle and lower soil;the same period on the same soil layer of soil available phosphorus content decreased with the treatment concentration increased;soil available phosphorus content of two-year-old forest decreased by the treatment time increased in the first three quarters of experimental time of the same nitrogen treatment on the same soil layer,but the last two quarter of available phosphorus content is relatively stable;three-year-old stands at the course of the entire experiment,soil available phosphorus content is relatively stable.In the same period and the same soil layer of soil available K content reduced with the treatment concentration increased;except the sample of July 2008 of three-year-old forest,the upper layer soil available K content of other samples was significantly higher than the middle and lower soil layers;nitrogen deposition on the surface had a catalytic role on the leaching of soil available K.with the treatment time extended,the available phosphorus content increased,but not significantly.3 The effects of simulated nitrogen deposition on the growth of the different age groups of live E.dunnii young forestsAfter a year of experiments,Nitrogen deposition enhanced an improvement of leaf Nitrogen content of E.dunnii young growth forests and the most obvious effect was on 2-N3 treatment of 89.22 percent;it also enhanced an improvement of leaf Phosphorus content,and the most obvious effect was on 2-N1 treatment of 262.22 percent.Nitrogen deposition enhanced an improvement of leaf K content,and the most obvious effect was on N2 treatment of 78.82 percent,but it played an inhibitory effect on two-year-old forest,and the most obvious effect was on N3 treatment of 19.32 percent.Nitrogen deposition inhibited the improvement of leaf carbon content of two-year-old forest,and N3 treatment increased the minimum level;N0,N2 and N3 all promoted the improvement of leaf carbon content of three-year-old forest,and N0 treatment increased the maximum level of 5.18 percent.Nitrogen deposition caused a reduction of leaf calcium and magnesium content of young growth E.dunnii,and the most obvious treatment effects were:2-N3 of 54.25 percent and 2-N1 of 49.1 percent.After a year of experiments,all nitrogen treatments enhanced nitrogen content of branches of three-year-old forest and N0 treatment increased the maximum level of 96.85 percent;but to two-year-old forest,there was only N3 play a advanced role.Nitrogen deposition promoted the phosphorus content of branch,and 2-N2 treatment of the most significant of 260.91 percent.All nitrogen treatments inhibited K content of branches and 2-N2 treatment had played the most significant inhibitory effect,while the 3-N1 treatment enhanced K content of branches.all nitrogen treatments inhibited carbon content of branches and 2-N0 treatment had played the most significant inhibitory effect of 49.44 percent,while 2-N3 and 3-N1 treatments enhanced carbon content of branches.all nitrogen treatments enhanced an inhabition of calcium content of branches, and 3-N0 treatment had played the most significant reduction effect of 63.14 percent.all nitrogen treatments enhanced an reduction of magnesium content of branches,and 2-N3 treatment had played the most significant reduction effect of 50.65 percent.4 The effects of simulated nitrogen deposition on the leaf litter decomposition of the different age groups of E.dunnii young forestsNitrogen deposition inhibited litter decomposition.The most obvious inhibitory effect of two-year-old forest was in May and June of 2008,and N3 inhibit the most,compared with the control level,the value of weight loss rate decreased 2.96 percent and 3.12 percent;Of three-year-old forest was in February and May,other times were no significant inhibitory effect. the inhibitory effect of N2,N3 treatment was better than the inhibitory effect of N1 treatment; inconsistent changes happened to three-year-old forest.At the first three months of the experiment,the inhibitory effect of N2 treament to two-year-old forest litter decomposition was greater than the inhibitory effect of N1,N3;The most obvious inhibitory effect of three-year-old forest was found in January of 2008.The inhibitory effect of N3 treatment to two-year-old forest was better than the inhibitory effect of N1,N2 after April,and to three-year-old forest,it showed the same laws from the beginning in June 2008.Litter decomposition mainly occurred in the first six months The largest weight loss rate reached 41.23 percent and after this time,the litter weight loss rate did not change significantly.After a year of experiments,nitrogen deposition restrained nitrogen liberation of the leaf litter,and the most obvious inhibition effect was in 2-N1 of 32.17 percent.Litter decomposition process of the release pattern of N elements was as follows:quick release-slow enrichment-slow release-a small amount of enrichment.And potassium element performed direct release.Nitrogen deposition promoted the release of potassium.Phosphorus release model was:Rapid release - a small amount of enrichment - a small amount of release - a small amount of enrichment,nitrogen treaments of low and middle concentrations inhibited phosphorus release effct of c,but nitrogen treaments of high concentration promoted the effect of phosphorus release; nitrogen deposition played a facilitating role to three-year-old forest.Nitrogen deposition promotes carbon degradation of litter,but the difference among each treatment is not significant.Nitrogen deposition inhibited calcium element loss of leaf litter of two-year-old forest,and low concentrations of nitrogen treatment played the greatest inhibitory effect,compared with the control level,the residual rate was 6.43 percent lower.With analysis of variance,the treatments were significantly different;N1 treatment inhibited calcium element loss of leaf litter of three-year-old forest,but N2 and N3 played a promotion role,the greatest effect higher.Variance analysis showed that there were no significant differences among treatments.Nitrogen deposition inhibited magnesium element loss of leaf litter of two-year-old forest, and the inhibitory effect was better as the concentration increases.Variance analysis showed that there were significantly different among treatments.N3 treatment played a promotion role to three-year-old forest,but N1 and N2 are played a inhibition role,the greatest inhibition effect happened in N2 treatment,compared with the control level,thr residual rate was 4.55 percent lower.Variance analysis showed that there were no significant differences among treatments.