| Since the industrial revolution, human activities created a large number of active nitrogen (N), so that the content of the proportional increase in atmospheric N deposition. N deposition and distribution of its sources rapidly expanding throughout the world, and continue to sink to the terrestrial and aquatic ecosystems. China has become the world outside of Europe and the United States, following the third largest N settlement clusters. Excess N deposition has caused eutrophication, soil and water acidification, terrestrial ecosystems N saturation, nutrient imbalances element and a series of ecological problems. Litter as an important part of forest ecosystems material circulation and energy flow, which in maintaining plant productivity, soil fertility, microbial activity and forest ecosystems have an important role in the carbon cycle. Thus, in the context of globalization, N deposition, N deposition study of litter and nutrient dynamics of extremely important. Secondary forest (secondary forest) as the main body of China and the world's forest resources, has an important role in the global material circulation and energy flow. Thus, in the context of globalization, N deposition, to study the evergreen broadleaf Litter return in response to increased N deposition, provide a theoretical basis and data support for nutrient cycling and energy flow area of forest ecosystems, which in turn is more reasonable and efficient solutions to global environmental problems of excess N deposition to provide a scientific basis.This study selected Sichuan Wawushan secondary evergreen broad-leaved forest for the study, using the test method to simulated N deposition (April 2013-June 2015), performed with NH4NO3 N deposition process, set up three kinds of N addition levels:control (CK,0 g N m-2·a-1), low N (LN,5 g N m-2 · a-1), high N (HN,15 g N m-2 · a-1), Effect of litter, litter nutrient content and the amount of restitution eLEMENTS N settlement. Experimentally species are divided into:flat Detached, China superba, Ke crust, thin stems and wild Acanthopanax Evodia Tong et al., In which flat Detached, China Ke Schima and crusty as the main species, so this experiment will litter was divided into:flat Detached, China superba, hard shell Ke, other fruit trees and branches five parts. The following conclusions.(1) simulated N deposition on the amount of litter has not reached statistical significance, but showed an increase trend of litter litter, litter growth LN and HN were treated at 4% and 17%. Annual litter litter obvious bimodal peak probably occurred around May and November, N settlement does not change the dynamic changes monthly amount of litter. Litter leaf litter 84.2%?86.9% of the total, including other species of leaf litter> China superba leaf litter> flat leaf litter Detached> crusty Ke leaf litter.(2) under simulated N deposition process, nutrient content of N, K, Ca and Mg, etc. showed an increasing trend, P nutrient content showed a decreasing trend. Nitrogen deposition significantly increased the LN and HN processing flat leaf litter K Detached element content. The remaining components and elements of indicators did not show significant differences among treatments. Each component of each litter nutrient content were significant seasonal variation.(3) natural state (not Nitrogen), the litter K, N, Ca, Mg and P elements restitution amounts were 10.12,9.06, 8.75,4.68 and 1.14 kg·hm-2. Nitrogen deposition significantly increased the amount of N elements return increased from 9.06 kg·hm-2 was 13.93 kg·hm-2 and 15.22 kg·hm-2, an increase of 54% and 68%. Nitrogen deposition also significantly increased the amount of potassium restitution, an increase of 12% and 35%. There are significant seasonal variation amount of each component element restitution litter. |
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