川西亚高山云杉叶凋落物质量损失过程及土壤生物的作用

采用分解袋法,研究了川西亚高山云杉纯林与混交林叶凋落物的质量损失过程及土壤动物与微生物的作用。结果如下:(1)云杉叶凋落物分解过程中,土壤动物数量总体呈下降趋势,即土壤动物主要在分解前期发挥作用,其中,大型土壤动物早期以植食性的蛴螬为主,中期以捕食性的石蜈蚣为主,后期以腐食性的马陆为主;中小型土壤动物始终以螨类、跳虫和线虫为优势类群;相关分析表明线虫数量与云杉叶凋落物分解速率相关性最大,大型土壤动物次之。(2)云杉叶凋落物分解过程中,微生物数量总体呈上升趋势,即土壤微生物主要在分解后期发挥作用,进一步相关分析表明真菌数量与云杉叶凋落物分解速率相关性大于细菌和放线菌。(3)云杉纯林叶凋落物分解速率低于混交林,其中分解3、15、21、24个月时,纯林小孔径分解袋失重率分别为混交林的65.51%、95.73%、98.91%、94.8%,大孔径分解袋失重率分别为混交林的89.83%、92.95%、98.13%、97.13%,即,两类林分小孔径分解袋及凋落物分解前期失重率差异更为明显,表明凋落物分解速率既受底物质量的影响,也和参与分解的土壤生物有关,其中与线虫、大型土壤动物及真菌的数量相关性最大。

PROCESS OF LEAF LITTER MASS LOSS AND THE CONTRIBUTIONS OF SOIL ORGANISMS IN PICEA ASPOERATA PLANTATIONS OF WESTERN SICHUAN

Litter decomposition, as one of the important processes in the forest ecosystem, is mainly controlled by climate, forest type, litter quality, and soil organisms. In order to investigate the mass loss rates in for the different mesh sizes of litterbags and analyze the contributions of soil fauna and soil microbe to the litter decomposition, a field experiment using litterbags was conducted in Picea aspoerata pure and mixed plantations of western Sichuan. First, our results showed that the total amount of soil fauna was decreasing during the whole litter decomposition stages, which suggested that soil fauna was the dominant factor of the litter decomposition at the early stage. We also found that the phytophagous soil macro faunal species during the whole litter decomposition stages appeared earliest, followed by the predatory and saprozoic species. Correlation analysis showed that the correlation coefficient of nematode amount and litter decomposition rate was the highest, followed by that of macro fauna amount. Secondly, quantity of soil microbe was increasing during the whole litter decomposition stages, which meant that the microbe prevailed as the regulator of the litter decomposition at the later stage. Correlation analysis showed that the correlation coefficient of litter decomposition rate with fungus quantity and was higher than those with bacteria and actinomycete. Thirdly, we found that the rates of litter mass loss in P. asperata pure plantation were lower than that of the mixed plantation. The decomposition rates of small mesh litterbags in pure plantation were 65.51%, 95.73%, 98.91%, 94.8% of that in the mixed plantation and the decomposition rates of big mesh litterbags in pure plantation were 89.83%, 92.95%, 98.13%, 97.13% of that in the mixed plantation at 3,15,21,24 months respectively. The difference of the rate of litter mass loss between two forest types was more significant at the early stage than at the later stage and more significant in small mesh litterbags than in big mesh litterbags. Our results inferred that the rates of litter mass loss were influenced not only by the quality of litter, but also by the soil organisms which involved in the litter decomposition, especially nematode, macro fauna and fungus.