镁碱度对土壤微生物生物量及氮素矿化的影响

The Effects of Mg^(2+) Alkalinity on Soil Microbial Biomass and Potentially Mineralizable N in Alkalized Magnesic Soils

土壤剖面中Mg2+的大量存在是土壤发生碱化的原因之一。测定了疏勒河昌马冲积扇缘镁碱化盐渍土土样的Mg2+碱度、Mg2+/Ca2+、pH值、HCO3-+CO32-等化学性质指标,分析了这些化学性质指标对土壤微生物生物量碳(氮)及其潜在可矿化氮的影响。结果表明:微生物生物量碳、微生物熵、微生物生物量氮随Mg2+/Ca2+、Mg2+碱度的升高而线性下降,而潜在可矿化氮随Mg2+/Ca2+、Mg2+碱度的升高而指数下降;另外,微生物生物量C/N与Mg2+/Ca2+和Mg2+碱度的反向变化关系说明,Mg2+碱化盐渍土环境中细菌在微生物群落中占优势。总之,高Mg2+碱度对土壤微生物而言是一种严重的胁迫环境,它使得微生物生物量变小、活性显著降低。

The effects of Mg2＋ alkalinity on microbial biomass C,biomass N and potentially mineralizable N were investigated.The study was conducted along the border area of the alluvial fan of Chang Ma of Shu Le He River.Thirty soil samples were taken and soil chemical and microbial indices were analysed.Biomass C,biomass N,microbial quotient（the percentage of soil organic C present as biomass C） decrease linearly with Mg2＋/Ca2＋ and Mg2＋ alkalinity,while potentially mineralizable N has a negative exponential relationship with Mg2＋/Ca2＋ and Mg2＋ alkalinity.In addition,the biomass C/N tends to be lower in soils with higher Mg2＋ alkalinity,probably reflecting the bacterial dominance in microbial biomass in alkalized magnesic soils.The results indicate that increasing Mg2＋ alkalinity results in a progressively smaller,more stressed microbial community which is less metabolically efficient.