坡位对寒温带天然樟子松林土壤微生物生物量碳氮的影响

目的研究我国寒温带天然樟子松林土壤微生物生物量碳、氮含量与坡位之间的关系，了解樟子松林对立地条件的响应，揭示天然樟子松林土壤微生物生物量变化特征及影响因素。方法以大兴安岭北部不同坡位天然樟子松林为研究对象，选择坡上、坡中和坡下3种立地条件，采用氯仿熏蒸浸提法测定了0 ~ 10 cm和10 ~ 20 cm土层土壤微生物生物量碳、氮含量。对其季节动态变化规律及影响因素进行分析比较。结果在观测期内（5—9月），樟子松林土壤微生物生物量碳、氮含量均呈现出波动式下降趋势，其变化范围分别是74.33 ~ 515.33 mg/kg和15.33 ~ 240.57 mg/kg，土壤微生物生物量碳氮比在1.04 ~ 5.73之间。坡位对土壤微生物生物量碳、氮和碳氮比产生显著影响（P < 0.01），坡下和坡中樟子松林土壤微生物生物碳、氮含量均值显著高于坡上（P < 0.05）；不同土层间土壤微生物生物量碳、氮含量也存在显著差异，0 ~ 10 cm土层显著高于10 ~ 20 cm土层（P < 0.05）。土壤微生物生物量碳、氮与土壤总有机碳、全氮和土壤含水量呈显著正相关，但与土壤温度和pH 值相关性不显著。结论坡位对天然樟子松林土壤微生物生物量影响显著，其含量存在明显的立地分异规律性，土壤总有机碳、全氮和土壤含水量是导致土壤微生物生物量碳、氮差异的主要影响因子。 

Effects of slope position on soil microbial biomass carbon and nitrogen in natural Pinus sylvestris var. mongolia forest in the cold temperature zone

ObjectiveIn order to study the characteristics of soil microbial biomass carbon and nitrogen in natural Pinus sylvestris var. mongolia forest in the cold temperature zone, the dynamic variation rule of soil microbial biomass carbon and nitrogen and those influencing factors were analyzed to provide a theoretical basis for soil nutrient transport and flow characteristics in the natural Pinus sylvestris var. mongolia forest.MethodMeasurements were taken every month from May to September in 2017 at three sites, including the top, the middle, the lower regions of slope in the Pinus sylvestris var. mongolia forest. The microbial biomass carbon and nitrogen in the 0?10 cm and 10?20 cm were determined by chloroform fumigation and extraction method, with their seasonal dynamics and the relationships with soil physicochemical properties in three sites.ResultThe results showed that the soil microbial biomass carbon and nitrogen contents under different slope positions presented fluctuating downward trends from May to September, with the ranges of 74.33 to 515.33 mg/kg and 15.33 to 240.57 mg/kg, respectively. The microbial biomass carbon-nitrogen radio was between 1.04 and 5.73, which was significantly different among varied site conditions during the measuring periods. The mean values of soil microbial biological carbon and nitrogen in the lower and middle regions of slopes were significantly higher than those in the top regions of slope (P < 0.05). Site conditions had significant effects on soil microbial biomass carbon, nitrogen and soil microbial biomass carbon-nitrogen ratio (P < 0.01). The soil microbial biomass carbon and nitrogen contents in 0?10 cm soil layer were significantly larger than those in 10?20 cm soil layer. Soil microbial biomass carbon and nitrogen were significantly positively correlated with soil total organic carbon, total nitrogen and soil water content, but not correlated with soil temperature and pH.ConclusionThe study shows that slope position has significant influence on soil microbial biomass in the Pinus sylvestris var. mongolia forest in the cold temperature zone, and its content has obvious site-differentiation rule. Soil total organic carbon, total nitrogen and soil water content are the main influencing factors leading to soil microbial biomass carbon and nitrogen difference.