坡位与土层对喀斯特原生林土壤微生物生物量与丰度的影响

运用氯仿熏蒸法和实时荧光定量PCR(Real-time PCR)法,检测喀斯特峰丛洼地原生林上、中、下坡位各土层(淋溶层:A层0~10 cm;过渡层:AB层30~50 cm;淀积层:B层70~100 cm)中土壤微生物生物量碳、氮(SMBC、SMBN)及微生物(细菌和真菌)丰度的变化,揭示坡位和土层对土壤微生物生物量和丰度的影响.结果表明,坡位和土层及其交互作用均对土壤微生物生物量及丰度具有显著影响(P0.05).具体表现为,土壤微生物生物量与丰度均随土层深度的增加而降低;A层SMBC在下坡位表现最高,均高于上坡位(P0.05),AB层、B层SMBC在中坡位最高;SMBN均在下坡位表现为最高,显著高于上坡位(P0.05);除B层细菌丰度、AB层真菌丰度在各坡位间无显著差异外,均表现为中坡位最高(P0.05).逐步回归分析结果表明,在坡位和土层的影响下,有机碳、碱解氮与p H、碱解氮与速效磷、速效钾分别是SMBC、SMBN、细菌丰度、真菌丰度的主要影响因子.

Effects of Slope Position and Soil Horizon on Soil Microbial Biomass and Abundance in Karst Primary Forest of Southwest China

To explore the effects of slope position and soil horizon on soil microbial biomass and abundance, chloroform fumigation extraction methods and real-time fluorescence-based quantitative PCR (Real-time PCR) were adopted to quantify the changes of soil microbial biomass C, N and abundance of bacteria and fungi, respectively.Soil samples were harvested from three horizons along profile, i.e., leaching horizon (A, 0-10 cm), transitional horizon (AB, 30-50 cm) and alluvial horizon (B, 70-100 cm), which were collected from the upper, middle and lower slope positions of a karst primary forest ecosystem.The results showed that slope position, soil horizon and their interaction significantly influenced the soil microbial biomass and abundance (P<0.05).Different from A horizon, where SMBC was greater in lower than in upper slope position (P<0.05), SMBC in AB and B horizons were highest in middle slope position.Similarly, SMBN was greater in lower than in upper slope position for A, AB and B horizons.Besides soil bacterial abundance in B horizon and fungal abundance in AB layer, the middle slope position had the highest value for all the three soil horizons (P<0.05).Stepwise regression analysis showed that soil organic carbon, available nitrogen and pH were the key factors responsible for SMBC and SMBN variation, respectively, while the important factors responsible for the variation of bacteria abundance were available nitrogen and available phosphorus, and that for fungi abundance variation were available potassium.