In Taiyue Mountain of Shanxi Province, five types of organic matter, i.e., biochar, maize straw, leaves of Quercus mongolica and Pinus tabuliformis, and sawdust of wood stem, were separately added to the soils of a P. tabuliformis forest. Nutrient content, enzyme activity, and microbial biomass were analyzed to elucidate the characteristics of soil ecoenzymatic stoichiometry and the element homeostasis of soil microorganisms. The results showed that the addition of woody sawdust significantly increased soil nitrogen and phosphorus content by 17.1% and 37.6%, and enhanced carbon, nitrogen, and phosphorus contents of soil microbial biomass by 118.0%, 41.0%, and 176.6%, respectively. The activities of carbon-, nitrogen- and phosphorus-targeting enzymes (i.e., β-1, 4-glucosaminosidase, β-1,4-N-acetylglucosaminosidase, leucine aminopeptidase and acid phosphatase) generally increased with the C:N of the added organic matter (biochar<Q. mongolica leaf< P. tabuliformis leaf < maize straw < woody sawdust). This indicated that ecoenzymatic stoichiometry was controlled by soil nutrient content and micro-bial biomass. The limitation of soil microbial growth by phosphorus was not alleviated after the addition of different organic matters, as indicated by the results of enzymatic ratio and its vector value. Soil microbial biomass carbon and nitrogen contents and their stoichiometry (C:N, C:P, N:P) were homeostatic, whereas the microbial biomass phosphorus content fluctuated slightly. The stabilities of microbial element contents and their proportion were mainly ascribed to the allocation of extracellular enzyme production. The susceptibility of soil microbial biomass phosphorus to the addition of organic matter indicated phosphorus limitation of microbial growth.
在山西太岳山地区,向油松林土壤中分别添加生物炭、玉米秸秆、蒙古栎叶、油松叶、木屑等5种有机物,测定各处理的土壤养分、酶及微生物生物量等指标,研究外源有机物添加下土壤酶化学计量特征及微生物元素组成的内稳性。结果表明: 添加木屑显著增加了土壤N(17.1%)、P(37.6%)含量,显著增加了微生物生物量碳(118.0%)、氮(41.0%)、磷(176.6%)。C、N、P获取酶(β-1,4-葡萄糖苷酶、β-1,4-N-乙酰氨基葡萄糖苷酶、亮氨酸氨基肽酶、酸性磷酸酶)活性总体上随添加有机物C/N值(生物炭<蒙古栎叶<油松叶<玉米秸秆<木屑)的增加而增加,其化学计量变化受土壤养分状态及微生物生物量的调控。酶活性相对比例及矢量特性表明,研究区微生物生长受到P的限制,且添加有机物没有缓解P的制约作用。微生物生物量碳、氮及化学计量比C∶N、C:P、N∶P属于绝对稳态型,而微生物生物量磷处于非稳态。微生物通过改变酶的分配策略保持微生物体元素及比例的相对稳定,仅有微生物生物量磷对土壤养分变化表现出不稳定性,可能因为P是研究区微生物生长的限制性元素。.
Keywords: Pinus tabuliformis; enzyme activity; organic matter; stoichiometric homeostasis.