| Litterfall is recognized as the critical pathways of organic matter and nutrient fluxes in forest ecosystems, and is an important part of ecological functions of ecosystem. This research was conducted to study on litterfall dynamics and its nutrients in a subtropical evergreen broad-leaved forest under simulation of nitrogen(N) deposition at Shitai during July 2013 to June 2014. The experiment was designed as follows: the control(CK), low N treatment(LN, 50 kg N·hm-2·a-1), high N treatment(HN, 100 kg N·hm-2·a-1), high N + P treatment(HN+P, 100 kg N·hm-2·a-1+50 kg P·hm-2·a-1). The purpose of the study is to determine the effects of simulated N deposition on forest litter production and its chemical composition, and to provide the basis for restoration and sustainable management of subtropical evergreen broad-leaved forest. The results obtained from 1-year experiment are given in the following.1. Litter productionThe annual mean litter production in the Castanopsis eyrei stand was 7.19t·hm·afor CK, 8.85 t·hm-2·a-1 for LN, 8.77 t·hm-2·a-1 for HN and 9.41 t·hm-2·a-1 for HN+P. The three treatments had a positive effect on litter production. The annual litter production of the Castanopsis sclerophylla stand averaged 7.86 for CK, 9.21 for HN and 8.84t·hm-2 for HN+P, respectively. The HN and HN+P treatment increased the annual litter production. The annual litter productions in this study are within the range of subtropical forest zone reported.2. Litterfall componentsThe order of the litterfall components ranked consistently by their amounts as:foliage>branches>fruit>miscellaneous. There existed significant differences among litterfall components and their proportion to the total litterfall for the sampling stands.Foliar litter was the primary composition in litterfall.3. Litterfall patternThe monthly litterfall in all treatments of Castanopsis eyrei stand and Castanopsis sclerophylla stand showed similar seasonal patterns, with two peaks occurred in April to May and in November. The seasonal patterns of litterfall were similar among the different treatments, suggesting that simulated nitrogen deposition did not change the eco-physiological characteristics of the dominant trees.4. Nutrient in litterfallThe nutrient inputs by litterfall were in order of N>K>Ca>Mg>P. LN?HN and HN+P treatments elevated the average concentrations of N in the litterfall compared with CK. All of the nutrient elements in the foliar litter showed strong seasonal changes.In the Castanopsis eyrei stand, the annual N fluxes by litterfall to the forest floor for the different treatments were 55.77 kg·hm-2 for CK, 64.44 kg·hm-2 for LN, 62.60kg·hm-2 for HN and 69.08 kg·hm-2 for HN+P. The annual P fluxes were CK, 1.73; LN,2.10; HN, 2.07 and HN+P, 2.33 kg·hm-2; K fluxes: CK, 34.72; LN, 39.11; HN, 39.96 and HN+P, 40.23 kg·hm-2; Ca fluxes: CK, 38.55; LN, 46.49; HN, 40.67 and HN+P,40.89 kg·hm-2; and Mg fluxes: CK, 26.23; LN, 34.64; HN, 30.12 and HN+P, 30.98kg·hm-2. Three treatments increased the annual fluxes and were in order of LN>HN+P>HN>CK.In the Castanopsis sclerophylla stand, the annual N fluxes were, respectively, to the forest floor for the different treatments was estimated, at 58.27 kg·hm-2for CK, 70.74kg·hm-2 for HN and 65.42 kg·hm-2 for HN+P; and P fluxes were 2.71 kg·hm-2 for CK,3.67 for HN, and 3.02 for HN+P; K fluxes 36.89 kg·hm-2 for CK, 49.48 for HN, and43.52 for HN+P; Ca fluxes 48.97 kg·hm-2for CK, 52.86 for HN, and 49.45 for HN+P;Mg fluxes 23.73 kg·hm-2 for CK, 24.92 for HN, and 21.89 for HN+P. The results indicated that the annual fluxes were increased by HN and HN+P treatments. However,the order was HN>HN+P>CK.5. C/N ratios in litter componentsAfter 1-year treatments, the N concentration in the foliar litter increased with increasing nitrogen deposition. Thus, the C/N ratios decreased obviously. |
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