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

春季解冻期不同纬度兴安落叶松林的土壤微生物生物量


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CmicNmic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1246.18 mg·kg-1,而Nmic分别为70.63、96.78、79.76 和119.66mg·kg-1.CmicNmic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CmicNmic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 (Cmic) and nitrogen (Nmic) 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 Cmic and Nmic in the L. gmelinii forests transplanted from the four sites differed significantly, being decreased with increasing latitude and soil depth. The Cmic for Tahe, Songling, Sunwu, and Dailing averaged 55463, 82641, 87481, and 124618 mg·kg-1, and the Nmic averaged 7063, 9678, 7976, and 11966 mg·kg-1, respectively. The Cmic and Nmic 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 Cmic 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 Cmic and Nmic significantly, but the affecting degree depended on the stages of soil thawing. The Cmic and Nmic 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.