春季解冻期不同纬度兴安落叶松林的土壤微生物生物量

Soil microbial biomass in Larix gmelinii forests along a latitudinal gradient during spring soil thawing

以移栽自兴安落叶松林自然分布区内4个纬度梯度(塔河、松岭、孙吴和带岭)的8年生兴安落叶松林为对象,于移栽3年后(2007年)的春季土壤解冻期,采用氯仿熏蒸浸提法测定了4个纬度梯度(处理)土壤的微生物生物量碳(Cmic)和微生物生物量氮(Nmic)的时间动态.结果表明:在相似基质和相同气候条件下,移栽自4个纬度梯度的兴安落叶松林春季土壤解冻期的Cmic和Nmic平均值差异显著,呈随纬度升高而减少、随土层加深而下降的分布格局.其中塔河、松岭、孙吴和带岭的Cmic平均为554.63、826.41、874.81和1246.18mg·kg-1,而Nmic分别为70.63、96.78、79.76和119.66mg·kg-1.Cmic和Nmic在解冻前达到最大值;解冻初期迅速下降;在冻融交替阶段变化不显著,且维持在较低水平;在解冻末期,来自低纬度的带岭和孙吴的Cmic回升较快.春季冻融期土壤温度和含水量对Cmic和Nmic的影响显著,其影响程度随冻融阶段而变化.土壤微生物生物量与解冻前的土壤温度呈负相关,与整个解冻期间的土壤含水量呈指数关系.

The 8-year-old Larix gmelinii forests were transplanted from four sites （Tahe, Songling, Sunwu, and Dailing） comprising a latitudinal gradient across the distribution range of L. gmelinii in Northeastern China, and the soil microbial biomass carbon （mic） and nitrogen （Nmic ） in spring soil thawing period were measured after 3-year transplanting. Under the similar soil substrates and the same climate conditions, the mean values of soil Cmic and Nmic in the L. gmelinii forests transplanted from the four sites differed significantly, being decreased with increasing latitude and soil depth. The Cmic for Tahe, Songling, Sunwu, and Dailing averaged 554. 63, 826. 41, 874. 81, and 1246. 18 mg·kg^-1, and the Nmic averaged 70. 63, 96.78, 79.76, and 119.66 mg·kg^-1, respectively. The Cmic and Nmic peaked before soil thawing, declined rapidly at the early stage of soil thawing, and had less change and maintained at a lower level during the period of soil freezing-thawing. By the end of soil thawing, the Cmic for lower latitudinal soils （i. e. , Dailing and Sunwu） recovered faster. Soil temperature and moisture content during spring soil thawing affected the temporal patterns of Cmic and Nmic significantly, but the affecting degree depended on the stages of soil thawing. The Cmic and Nmic were negatively correlated to the soil temperature at the early stage of soil thawing, and exponentially related to the soil moisture content during the whole soil thawing period.