| Long-term climate changes would have direct and indirect influence to the litter decomposition. On one hand, climate changes can influence litter decomposition directly as a result of their effects on the precipitation and temperature in the forest ecosystem; On the other hand, through long-term climate changes would lead to the transfer of climatic zone and the removal of species in the forest, thereby their would alter the original species composition of the forest and trigger the species and proportion change in the forest litter composition, and then would effect the original litter decomposition indirectly. For clarify the potential impact of climate changes in the future on the litter decomposition in the eastern mountainous region in the northeast china forest. Our study object based on the leaf litter from Pinus koraiensis which is the main tree species in northeast forest climax community and Quercus mongolica which has the biggest area in the northeast secondary forest and the climate changes in the future have great advantage for its grow. We used microcosm study to simulate temperature increase (+4℃+6℃) and buried litter bags with Pinus koraiensis and Quercus mongolica leaf litter in different proportion mixture(Quercus mongolica:Pinus koraiensis MH3:1、MH1:1、 MH1:3、pure Quercus mongolica and pure Pinus koraiensis) in the field of Liangshui original korean pine forest and Laoshan Quercus mongolica secondary forest to simulate the alter in litter species composition and proportion under the effect of future climate changes. We simultaneously measured cumulative CO2production、mass loss rate、C and N elements decompose dynamic in the mix litter respectively and though analysis and comparison the observed and respected mass loss rate in the mix litter C/N rate, then we made generalized analysis of these date can come to the conclusion that:(1) The indoor single factor control microcosm experiment indicated that the increase temperature accelerated pure Quercus mongolica leaves litter, pure Pinus koraiensis needle litter and their litter mixture decomposition rate. In different temperature level, the decomposition characteristics in different litter quality have distinction, in+0℃and+4℃condition,the decomposition rate in the order of mixture litter>pure Quercus mongolica leaves litter> pure Pinus koraiensis needle litter. However, in the+6℃condition, the decomposition rate between mixture litter and pure Quercus mongolica leaves litter have just a small difference, but both of them decomposition faster than pure Pinus koraiensis needle litter.(2) The field experiments in the original broad-leaved korean pine forest indicated that compared with single litter decomposition, Quercus mongolica and Pinus koraiensis mix litter can accelerated the decomposition rare of pure Quercus mongolica leaves litter and pure, and enhance their decomposition turnover time. In the mixture litter, Quercus mongolica leaves litter can accelerate Pinus koraiensis needle litter initial C release and N enrichment, reduce C/N rate, may enhance the decomposition rate of Pinus koraiensis needle litter; Pinus koraiensis needle litter can accelerate Quercus mongolica leaves litter initial C release, but have not obvious significance affect on Quercus mongolica leaves litter N decomposition. Low-proportion Quercus mongolica leaves litter mix with Pinus koraiensis needle litter have the fastest decomposition rate, with the Quercus mongolica leaves litter proportion increase in the mixture litter, the decomposition rate increase after decrease in the first.(3) The field experiments in the Quercus mongolica secondary forest indicated that compared with single litter decomposition, Quercus mongolica leaves litter and Pinus koraiensis needle litter mix in either proportion decomposition faster than single Pinus koraiensis needle litter, but only MH1:3decomposition faster than single Quercus mongolica leaves litter, however, MH1:1and MH3:1have not significant different in the mass loss; The litter decomposition mass loss rate observed value and predicted value in the different treatments indicated that MH1:3and MH1:1observed value is greater than predicted value, their have acceleration effect for litter decomposition; however, MH3:1observed value is lower than predicted value, it has inhibiting effect for litter decomposition. In the mixture litter MH3:1, Quercus mongolica leaves litter can accelerate Pinus koraiensis needle litter initial C decomposition, however, in other proportion mixture litter, Quercus mongolica leaves litter have inhibiting effect for Pinus koraiensis needle litter C decomposition. In the mixture litter MH1:3, Quercus mongolica leaves litter have obvious acceleration effect for Pinus koraiensis needle litter N enrichment, however, for other proportion, Quercus mongolica leaves litter have inhibiting effect for Pinus koraiensis needle litter N decomposition;in the mixture litter MH1:1and MH1:3, inus koraiensis needle litter can accelerate Quercus mongolica leaves litter C decomposition, however, in the mixture litter MH3:1, the effect of Pinus koraiensis needle litter on Quercus mongolica leaves litter C decomposition is inhibiting after accelerate in the first; Pinus koraiensis needle litter have not obvious regularity for Quercus mongolica leaves litter. Overall, the litter in the mixture MH1:3have the fastest decomposition rate, enhance the turnover time when the litter decomposition in mix.(4) Comprehensive analysis indoor microcosm study and field experiments results, derived temperature is one of the most important factor for litter decomposition, the decomposition fast with the temperature increase; Litter mix decomposition have acceleration effect on litter decomposition, have inordinately influence to the litter C,N decomposition and C/N rate of two species; Litter decomposition have home-field effect; All the treatments decomposition faster in the Quercus mongolica secondary forest than in the original broad-leaved korean pine forest. Therefore, under the background of climate change, increase temperature will enhance the decomposition rate of Quercus mongolica and Pinus koraiensis litter; In the process Quercus mongolica gradually become associated species in the original broad-leaved korean pine forest, Quercus mongolica and Pinus koraiensis litter mix can accelerate litter decomposition, moreover, MH1:3is decomposition fastest; Similarly, in the process Quercus mongolica secondary forest gradually evolvement to climax community, Quercus mongolica and Pinus koraiensis litter mix can obvious accelerate litter decomposition in the earlier stage, MH1:3is also decomposition the fastest in the whole decomposition process. Litter in the laoshan Quercus mongolica secondary forest decomposition faster than liangshui original broad-leaved korean pine forest. |
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