少花蒺藜草对科尔沁沙地土壤氮转化效应的研究

外来入侵植物会影响入侵地土壤氮库结构,研究外来植物与土壤氮转化的关系可以为揭示其入侵机制提供理论依据。以中国北方农牧交错带大面积发生的入侵植物少花蒺藜草为研究对象,选取裸地及本土植物鹅观草样地作为对照,研究少花蒺藜草入侵与外源氮对土壤氮转化速率的影响,以期从土壤氮转化速率的角度探讨少花蒺藜草的入侵机制。结果表明:与裸地及本地植物鹅观草样地相比,少花蒺藜草入侵地土壤氮净矿化速率增加;在分蘖期前(6-7月),土壤硝化速率增加、氨化速率降低;自分蘖开始至枯萎(8-10月),土壤硝化速率降低、氨化速率增加。添加NH4+-N或NO3--N对整体的氮转化速率水平有影响,并使分蘖期后少花蒺藜草入侵地的氮矿化速率降低,但不改变分蘖前后三样地间硝化和氨化速率的大小关系。与净硝化速率及净氨化速率的关联性大小顺序为:添加外源氮处理>少花蒺藜草入侵>交互效应。与净矿化速率的关联性大小顺序为:添加外源氮处理>交互效应>少花蒺藜草入侵。添加外源氮更有利于裸地及本地植物鹅观草样地的氮矿化作用。少花蒺藜草在低氮素含量环境中表现出的生长优越性揭示了其适应沙质草地生态系统的一种入侵机制。

The Effect of Cenchrus spinifex on Nitrogen Mineralization of Horqin Sandy Soil

Invasive plants can affect the nitrogen pool structure of the local soil.In this paper,the effects of Cenchrus spinifex invasion and exogenous N on the soil nitrogen conversion rate were studied,with the bare land and native plant Roegneria kamoji as the control,so as to explore the soil nitrogen conversion rate of C.spinifex invasion.The results showed that the soil net N mineralization rate in C.spinifex invaded-area was increased,net nitrification rate was increased from June to July and then decreased during August to October.The net amination rate was decreased before tillering stage and increased after that,compared with those of bare land and native plant R.kamoji soil.With the addition of NH4+-N/NO3-N,net N mineralization rate in C.spinifex invaded-area was decreased after tillering stage,while the relation of net nitrification rate and amination rate between three samples didn’t change.Adding exogenous N had the greatest impact on the net nitrification rate and net amination rate,followed by soil types and the interaction effect,while the influences on the net mineralization rate were exogenous N,interaction effect,and plant type,respectively.The superiority of C.spinifex in an environment with low nitrogen content reveals an ecological adaptation mechanism in sandy grassland ecosystems.