| Taking Pinus tabulaeformis forest with young-aged, middle-aged and near mature, pure forest with Populus davidiana and mixed forest with Populus davidiana, Betula platyphlla and Quercus mongolica as test objects, the variations of soil microbial biomass carbon, respiration and metabolic quotient along the leaf litter composition were studied. As a consequence, scientific basis and data supporting were provided for the study of microbiological mechanisms and the relationship between soil microorganisms and leaf litter composition, through this study. The results were as follows.(1) The average contents of MBC in 0-20cm layers were 69.48 mg·kg-1 in control,114.14 mg·kg-1 in undecomposed litter treatment and 126.06 mg·kg-1 in semi-decomposed litter treatment in Pinus tabulaeformis young-aged forest, and the average rates of MR were 0.46 μg·g-1·h-1,0.73 μg·g-1·h-1 and 0.75 μg·g-1·h-1, respectively. The average contents of MBC in 0-20cm layer were 80.63 mg·kg-1,131.70 mg·kg-1 and 146.00 mg·kg-1, and the average rates of MR were 0.48 μg·g-1·h-1, 0.68 μg·g-1·h-1 and 0.71 μg·g-1·h-1 in Pinus tabulaeformis middle-aged forest, respectively. The average contents of MBC in 0-20cm layer were 97.81 mg·kg-1,183.12 mg·kg-1 and 211.06 mg·kg-1, and the average rates of MR were 0.56 μg·g-1·h-1,0.80 μg·g-1·h-1 and 0.86 μg·g-1·h-1 in Pinus tabulaeformis near mature forest, respectively. Thus, MBC and the utilization efficiency of organic carbon in soil were Pinus tabulaeformis young-aged forest<Pinus tabulaeformis middle-aged forest <Pinus tabulaeformis near mature forest, and semi-decomposed litter treatment> undecomposed litter treatment> control treatment. Meanwhile, MR in soil was Pinus tabulaeformis middle-aged forest<Pinus tabulaeformis young-aged forest<Pinus tabulaeformis near mature forest, and semi-decomposed litter treatment>undecomposed litter treatment. It is shown that adding litter into soil could significantly increase MBC, MR and the utilization efficiency of organic carbon. MBC and the utilization efficiency of organic carbon in the stand increased gradually, and MR had a trend of increasing after decreasing initially with the forest age growth. Besides, semi-decomposed litter treatment could enhance microbial activity and the utilization efficiency of organic carbon in soil.Moreover, double factor variance analysis showed that litter in different ages Pinus tabulaeformis forest had a significant effect on MBC and qCO2 in each layer, and MR in 10-20cm layer. Litter decomposition of different degrees had a significant effect on soil microbial characteristics in 5～10cm and 10～20cm layers. However, there were no significant interactions on soil microbial characteristics in each soil layer.(2) The average contents of MBC in 0-20 cm soil layer were 24.8 mg·kg-1,325.3 mg·kg-1, 349.8 mg·kg-1 and 319.0 mg·kg-1 in the leaf litter removal treatment, Betula platyphlla treatment, Populus davidiana treatment and Quercus mongolica treatment, and the average rates of MR were 0.66 μg·g-1·h-1,1.12 μg·g-1·h-1,1.16 μg·g-1·h-1 and 1.10 μg·g-1·h-1,respectively. Meanwhile, in 0-20 cm soil layer, the average contents of MBC in the treatment with single leaf litter, mixed litter of two plant species and mixed litter of three plant species were 331.37 mg·kg-1,418.52 mg·kg-1 and 529.34 mg·kg-1, and the average rates of MR were 1.13 μg·g-1·h-1,1.30 μg·g-1·h-1 and 1.46 μg·g-1·h-1, respectively. In contrast to the MBC and MR, qCO2 in soil showed a reverse pattern. So, the different compositions of litter led to different degrees of soil microbial characteristics. Enhancement of litter quality and mixture of different species of leaf litter could increase MBC, MR and the utilization efficiency of organic carbon in soil.(3) The treatments with Betula platyphlla and Quercus mongolica leaf litter in home environment (Bh and Qh) had higher contents of MBC than that in other environment (Ba and Qa). But, there was no significant difference in MR between home environment and other environment. Response degree of MBC and MR to home-field advantage of different litter decomposition was inconsistent. The MBC in Qa treatment fell by 39.63%,34.92% and 33.50% compared to Qh treatment, in each soil layer. But MBC in Betula platyphlla treatment were 31.57%,27.14% and 16.97%, respectively. MR in Qa treatment accounted for 96.29%,92.43% and 83.73% of Qh treatment, while MR in Betula platyphlla treatment were 99.44%,97.28% and 101.31%. In contrast to MBC, qCO2 in soil showed a reverse pattern. So, MBC and qCO2 had an obvious response to home-field advantage of Betula platyphlla and Quercus mongolica litter decomposition. Meanwhile, soil microbial characteristics had a higher response degree to home-field advantage of Quercus mongolica litter than Betula platyphlla litter... |
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