Study Of Foliar Litter Decomposition In Different Climate Zones And Acid Rain Stress

Litter decomposition is an important link for material recycling and energy conversion in terrestrial ecosystems, and it is affected by the combined effects of multiple factors, such as substrate quality, climate, soil microbe and the outside environmental conditions. The litter decomposition test under different climate gradients was conducted in five climate zones in eastern China by means of litterbag technique. In addition, we set up the experiment of litter decomposition under different gradients of acid rain in the subtropical area with high incidence of acid rain, to study the effects of acid rain in litter decomposition.The results of the study in subtropical area suggested that decomposition rate significantly correlated with concentrations of initial C, N, P and Lignin, Lignin:N ratio and C:N ratio. And in different decomposition phases and sites, the main variables and parameter value for predicting decomposition rate were different. The differences in climatic conditions had greater impact on decomposition rate in the cross-climatic zones experiment. Average annual precipitation is the primary climate factors that affected litter decomposition in different climatic conditions.The study of the 3 different foliar litters decomposition under climate gradients showed that the decomposition rate of k value of 3 foliar litters(S. superba, M. chapensls and C. glauca) in the 5 climatic zones were between 0.17and 0.95. There was a common trend for the decomposition rates of the 3 kinds of foliar litters in different climate zones, the k-value was the highest in the tropical zone(Jianfeng ling), followed by south subtropical zone(Dinghu shan), mid-subtropical zone(Qiandao hu), mid-temperate zone(Liangshui), warm temperate zone(Dongling shan). The lowest decomposition rate in Dongling shan may be associated with its higher elevation and lower temperature. In the same climate zone, litter decomposition rate was different among species. M. chapensls had the highest decomposition rate which ranged from 0.46 to 0.95; It was 0.17~0.68 for S. superba, and 0.22~0.57 for C. glauca. The initial nutrient content of M. chapensls foliar litter was the highest among the three. The result showed that the initial nutrient content and lignin/N ratio of litter showed better predictability for the decomposition rate.The dynamics of nutrient content during decomposition showed an alternating process of enrichment-release. The differences in nutrient concentration dynamics of the 3 kinds of foliar litters among the 5 sample situations were similar: the enrichment-release process was more significant in warm climate than that in colder regions.The results of experiments of effects of simulated acid rain on the decomposition of foliar litter indicated that the range of the litter decomposition rate(k) is between 0.15~0.80 for Schima superba, M. chapensls and C. glauca, and the decomposition rate had been slowed down with the increase of the stress grade of acid rain. The k-value of 3 kinds of foliar litters in the moderate (pH4.0) and severe (pH2.5) acid rain stress were less than that of the control treatment (pH5.6). The semi-decomposed and 95% litter decomposition cycle were all extended under the moderate and severe acid rain treatment. In the same acid rain intensity, the k-value of Schima superba was the maximum, which was significantly greater than that of M. chapensls and C. glauca.In the experiment of simulated acid rain'stress, the nutrient content of different foliar litters of the control group tended to the same level after decomposition of 2 years, and the nutrient dynamics under acid rain stress showed greater difference. Acid rain stress had an inhibiting effect on N enrichment and K release.