峡谷型喀斯特不同生态系统的土壤微生物数量及生物量特征

采用样地调查与室内分析相结合的方法,研究了峡谷型喀斯特水田、旱地、草地、灌丛、人工林、次生林6种生态系统不同深度土壤微生物数量、微生物生物量特征及其分形关系。结果表明:峡谷型喀斯特不同生态系统的土壤微生物数量及组成不同,微生物数量均以次生林最高,旱地最低,其组成数量均为细菌放线菌真菌,细菌是土壤微生物的主要类群,数量多达26.66×105—71.64×105cfu/g,占全部微生物比例为87.00%—95.50%,其次为放线菌数量,为1.45×105—3.78×105cfu/g,所占比例为4.21%—12.39%,真菌数量最小,为0.07×105—0.23×105cfu/g,所占比例仅为0.24%—0.61%,不足1%。不同生态系统土壤微生物生物量碳(MBC)、氮(MBN)、磷(MBP)的含量不同,次生林MBC与MBN最高,人工林MBP最高,旱地MBC最低,草地MBN与MBP最低;各生态系统均为MBCMBNMBP。不同生态系统的MBC/SOC、MBN/TN、MBP/TP分别为0.44%—0.97%、2.13%—3.13%、1.46%—2.13%,差异不显著;MBC/MBN在3.06—6.54之间,其中次生林极显著高于其他生态系统,其他生态系统差异不显著。不同生态系统土壤微生物数量及生物量均随土层加深而减少,且具有良好分形关系,均达到了极显著水平(P0.01)。探讨土壤微生物活性为提高石灰土土壤肥力、促进喀斯特植被迅速恢复提供依据。

Characteristics of soil microbial populations and biomass under different ecosystems in a canyon karst region

Determining the relationship between soil microbial populations and soil microbial biomass in ecosystems can provide useful information for vegetation restoration in the canyon Karst region. Therefore, based on a combination of field investigation and laboratory analysis, we analyzed soil microbial populations and soil microbial biomass at different soil depths as well as their fractal relationships under six typical ecosystems, i.e., paddy field, dry land, grassland, Shrubbery, plantation forest, and secondary forest, in the canyon Karst region in southwest China. Three plots with size of 20 m × 20 m were constructed in each ecosystem type, and five soil samples were collected at four corners and the middle in each plot and then mixed as one sample. The dilution plate method and the chloroform fumigation extraction method were used to determine soil microbial populations and soil microbial biomass., respectively. The results showed that soil microbial populations and composition varied under different ecosystems in the canyon karst region. Soil microbial populations were largest in the secondary forest, followed by the plantation forest, while least in the dry land, indicating that the project of returning crop land to forests or grassland have a significant impact on increasing the soil microbial populations. Microbial composition in the six ecosystems performed in the order of bacteria > actinomycetes > fungi. The bacteria number was 26.66×10⁵-71.64×10⁵cfu/g with the highest proportion of 87.00%-95.50% of total soil microbial number; followed by actinomycetes, whose number and proportion were 1.45×10⁵-3.78×10⁵cfu/g and 4.21%-12.39%, respectively. However, the fungi quantity was 0.07×10⁵-0.23×10⁵cfu/g, and the proportion was less than 1%, just only 0.24%-0.61%. Under different ecosystem types, soil microbial biomass carbon (MBC), soil microbial biomass nitrogen (MBN), and soil microbial biomass phosphorus (MBP) were diverse, but all of them appeared to be a trend of MBC > MBN > MBP. Soil MBC and MBN was highest in the secondary forest, while MBP was highest in the plantation forest, in comparison with that MBC was lowest in the dry land, MBN and MBP were lowest in the grass. The ratios of MBC/SOC, MBN/TN and MBP/TP ranged from 0.44%-0.97%, 2.13%-3.13%, and 1.46%-2.13%, respectively, with no significant differences among the six ecosystems. The value of MBC/MBN ranged from 3.06 to 6.54, which in the secondary forest was significantly higher than that in other ecosystems; however, no significant differences existed among the rest ecosystems. A good fractal relationship existed between soil microbial populations and soil microbial biomass at a highly significant level (P < 0.01). Moreover, both soil microbial populations and soil microbial biomass in the six ecosystems decreased as an increase in soil depth. As a result, exploring soil microbial activities could provide the basis for improving the soil fertility of lime soil and boosting vegetation restoration in karst regions.