火烧对河北平泉油松林土壤微生物量的影响

以河北平泉油松林近期(火后半年)火烧迹地为研究对象，根据树干熏黑高度和树木死亡率情况，划分不同火烧强度(轻度、中度、重度)，并以邻近未火烧区设置对照样地，采用氯仿熏蒸浸提法测定各研究区土壤微生物量碳、氮(C_mic、N_mic)，分析不同强度火烧对其土壤微生物量碳、氮(C_mic、N_mic)的影响。结果表明:不同强度火烧后土壤C_mic、N_mic含量均呈下降的趋势，不同土层间土壤C_mic、N_mic含量随土层深度增加而逐渐减小，土壤C_mic变化在34~205 mg/kg之间，土壤N_mic变化在7~40 mg/kg之间；土壤微生物量碳氮比(C_mic/N_mic)整体处于5~6之间。双因素方差分析表明:火烧强度、土层深度及二者的交互作用对土壤有机碳(SOC)、全氮(TN)、铵态氮(NH₄+-N)、硝态氮(NO₃--N)均有显著影响(P < 0.05)，对于土壤pH值，仅火烧强度对其影响显著(P < 0.05)；同时，火烧强度、土层深度及二者的交互作用对土壤C_mic和N_mic的影响均达到极显著水平(P < 0.01)。土壤养分(SOC、TN、NH₄+-N和NO₃--N)主要集中在表层(0~10 cm)，重度火烧后土壤养分含量显著减少，同时，土壤pH显著升高。相关分析结果表明:土壤有机碳、全氮对土壤C_mic、N_mic有极显著影响(P < 0.01)，土壤C_mic、N_mic含量与土壤有机碳、全氮均呈正相关。主成分分析进一步表明土壤有机碳、全氮是影响土壤C_mic、N_mic的主要因素。 

Impact of fire on soil microbial biomass of Pinus tabuliformis forest in Pingquan County,Hebei of northern China

In the burned area of Pinus tabuliformis forest in Pingquan County, Hebei of northern China, we measured soil microbial biomass carbon (Cmic), nitrogen (Nmic) of different fire intensity regions with a fumigation-extraction method after burned half a year. The study area was classified into different levels according to the smoked height and tree mortality: high-severity sites, middle-severity sites, low-severity sites and nearby unaffected sites. The purpose of our research was to explore the effects of different severity fire on Cmic and Nmic . The results showed that both Cmic and Nmic decreased after different intensity burning and gradually declined with the soil depth. Cmic ranged from 34-205 mg/kg;Nmic ranged from 7-40 mg/kg;Cmic/Nmic was wholly at 5-6. Two-way ANOVA showed that fire severity, soil layer and the interaction of the two factors had significant effects on soil organic carbon ( SOC) , soil total nitrogen ( TN) , NH4+-N, NO3--N ( P <0. 05 ) . However, soil pH was only positively correlated with fire severity ( P <0. 05 ) . Meanwhile, fire severity, soil layer and the interaction of the two factors had significant effects on Cmic and Nmic(P<0. 01). Soil nutrients were distributed mainly in the 0-10 cm layer and dropped sharply after the high-severity fire. Besides, soil pH increased significantly after the high-severity fire. The correlation analysis result showed that SOC and TN influenced the Cmicand Nmic extremely significantly (P<0. 01).The soil microbial biomass was positively correlated with SOC and TN. Principal component analysis further prove that SOC and TN are the main factors affecting Cmic and Nmic .