Study On The Decomposition Characteristic Comparison And Mixed-decomposition Between Chinese Fir And Broad-leaved Species Litter

Chinese fir(杉木) is a timber species which grows quickly and has an important role in south forestry. Ecosystem of Chinese fir artificial forestry is declining seriously because of successive plantation which restricted sustaining development of Chinese fir artificial forestry. Many researches indicated that one of the most important factors which induce soil declining is that Chinese fir litter decompose slowly and that the nutrients return to the soil is little, the ability of self-raising is also limited, etc. Techniques such as fertilization and scanty cutting can improve decomposition condition of forestry litter. But as far as grown forestry is concerned, these measures are not enough. So taking sufficient advantage of species relations, building logical artificial forestry to accelerate Chinese fir litter decomposition and expedite nutrient returning has become an important issue during the course of cultivating Chinese fir artificial forestry.Applying the nylon bag method, Phoeba bournei (楠木)and Schima superba (木荷) were chosen particularly to mixed-decompose with Chinese fir leaf litter in different proportion on the base of studying the character of their solo decomposition, and the basin simulate experiment was also adopted to study the influence of litter decomposition on the soil. This study aimed to understand the inter-species relative of mixed forest and find one or more proper species mixed-plantation with Chinese fir which can accelerate Chinese fir litter decomposition and reduce the soil declining, and offer the reference to Chinese fir mixed forestry. The results indicated,(1) Chinese fir litter decomposed slowly, and the difference of decomposition rate between leaf and branch was big. The first year weightlessness of leaf litter was 40.6%, the decomposition coefficient was 0.0013d^-1 and the time of 50% and 95% decomposition were 1.47a and 6.32a.While the first year weightlessness of branch litter was only 23.1%, the decomposition coefficient was 0.00l0d^-1 and the time of 50% and 95% decomposition were 1.96a and 8.27a respectively. During the course of the Chinese fir litter decomposition, the concentration of N and P both were ascending, and the branch's extent larger than the leaf. K was descending sharply; C and C/N were descending fluctuantly. N, P, K and C released purely in the leaf litter, but in the branch litter, only K and C released purely when the end of experiment. The sequence of releasing rate was K>C>N>P.(2) Different treatment had different influence on the decomposition of Chinese fir. Buried treatment could improve its decomposition, and the first year weightlessness of leaf and branch had increased by 14.5% and 38.5% over the soil surface treatment respectively; the first yearweightlessness of fertilize NO>N treatment had increased by 13.3 over the unfertilized treatment. But fertilize NH+4-N treatment's approximated the comparison.(3) The different species had different decomposition rates. The weightlessness rates of three species were Schima superba (51.6%) >Phoeba bournei (42.0%) >Chinese fir (40.6%). their first month weightlessness rates were all high, and the peak value of Chinese fir's weightlessness rate appeared at May, but Schima superba and Phoeba bourneVs both appeared at September. Decomposition coefficients of three species were 0.0013d-l, 0.0014d-l, 0.0020d-l, half decomposition time were 1.47a, 1.32a, 1.02a and 95% decomposition time were 6.32a, 5.26a, 4.17a respectively. The above all showed the leaf litter of broad-leaved species decompose quickly and the Chinese fir slowly.(4) During the course of Chinese fir, Phoeba bournei and Schima superba's leaf litter decomposition, each nutrient element had different concentration change trend. P concentration of three was fluctuant ascending slowly; K concentration descended sharply in the prophase of decomposition, especially Chinese fir, and mild change trend in the anaphase; There were many discrepancies of N concentration among species, Chinese fir and Phoeba bournei had enrichment always, but Schima superba's changed from descending to ascending and then to descending. After a year, its concentration changed from 10.894g-kg"' to 10.981g-kg''. Three leaf litters also had different nutrient element releasing rates, N, P, K and C of three species were all released gradually, and the sequence of releasing rate was K>OP>N; In three species, Schima superba had the biggest releasing rate, Chinese fir smallest which had the same trend as the weightlessness.(5) From the weightlessness rate of Chinese fir in the mixed-decomposition, in the course of mixed-decomposition between Chinese fir and Phoeba bournei, it was no impacted by Phoeba bournei in the prophase but was promoted prominently in the anaphase, and the more proportion of Phoeba bournei, the more obvious promotion to it. In the course of mixed-decomposition between Chinese fir and Schima superba, it was also no impacted by Schima superba in the prophase but was affected by Schima superba and the more proportion of Schima superba, the more obvious inhibition to it.(6) During the period of mixed-decomposition with different proportion between Chinese fir and Phoeba bournei leaf litter, the decomposition coefficient of Chinese fir was improved by Phoeba bournei to a certain extent and the more proportion of Phoeba bournei, the higher decomposition coefficient which was 0.0013d'\ 0.0014d"\ 0.0015c!'1 respectively, meanwhile, the half decomposition time and 95% decomposition time of Chinese fir were also shorten. But when the mixed-decomposition between Chinese fir and Schima superba leaf litter in differentproportion, the decomposition of Chinese fir was inhibited weakly by Schima superba in general.The decomposition coefficients of Chinese fir leaf litter in three proportion treatments were all 0.0013d"1, the half and 95% decomposition time of each group were similar or more than the comparison. Whereas Chinese fir leaf litter inhabited Phoeba bournei decompose and promoted Schima superba to certain extent.(7) When mixed-decomposition between Chinese fir and Phoeba bournei leaf litter with different proportion, the decomposition was promoted to certain degree, and the more proportion of Phoeba bournei, the higher promotion to it. When the mixed-decomposition between Chinese fir and Schima superba, Chinese fir and Schima superba had no interaction in the group of 75%Chinese fir+25%Schima superba, and the decomposition was inhibited to certain degree in groups of 50%Chinese f\x+50%Schima superba and 25%Chinese fir+75%Schima superba, but the decomposition was inhibited when the mixed-decomposition between Chinese fir and Schima superba in general.(8) Mixed-decomposition of litter had complex influences on each element of Chinese fir. Each element concentration change trend of Chinese fir in the mix-decomposition approximated to the comparison on the whole. During the course of mixed-decomposition between Chinese fir and broad-leaved species leaf litter, N, P and K concentration of Chinese fir in the mixed-decomposition was lower than the comparison in the prophase then higher than the comparison subsequently in general, and then lower appreciably than or approximate to the comparison when mixed decomposition of 360 days; C/N and C concentration also lower than or approximate to the comparison appreciably. When mixed decomposition between Chinese fir and Phoeba bournei leaf litter, N, C and K releasing rate of Chinese fir were all promoted, and the more proportion of Phoeba bournei, the higher promotion to them; P releasing rate was inhibited. But when mixed decomposition between Chinese fir and Schima superba, N, C and P releasing rate of Chinese fir were all promoted and K releasing rate was inhibited.(9) During the period of mixed-decomposition between Chinese fir and broad-leaved species leaf litter, each element nutrient was releasing all the time. The more broad-leaved leaf litter, the higher releasing rate of N, P and C, but K was contrary to them. Compared the nutrient remaining rate's expected value with observed value of mixed-decomposition between Chinese fir and broad-leaved leaf litter, the results showed, releasing of N, P and C was inhibited except K when mixed-decomposed with Phoeba bournei; And Releasing of N and P, especially K element was inhibited except C when mixed-decomposed with Schima superba leaf litter.(10) The decomposition of leaf litter has positive role in soil acidification, and the sequence was 25%Chinese f\r+75%Phoeba bournei group(5.1) > pure Schima superba...