作物根系对根际土壤N2O产生与排放的调控机制研究进展

Research progress on the regulatory mechanisms of crop roots on N2O production and emissions in rhizosphere soil

  • 摘要: 农田土壤是大气N2O的重要排放源。农田土壤N2O排放不仅受农业管理措施影响, 还与作物根系生长密切相关, 根系自身代谢对农田土壤N2O生成与还原产生影响, 进而影响农田N2O排放。根际是根系-土壤-微生物相互作用的重要界面, 是根系影响土壤N2O排放最直接、最强烈的关键场所, 也是农田土壤N2O产生的热点区域, 在农田N2O排放中所占份额不容忽视。因而根系对根际N2O排放的影响机制研究普遍受到重视。本文以国内外相关研究为基础, 综合梳理了有关作物根系生长对农田土壤N2O排放的影响强度以及对根际微域N2O产生与排放的调控机制方面的研究进展, 剖析了作物根系影响根际微域土壤N2O产生与排放研究中存在的难点, 并对未来相关研究工作进行了展望。根系对农田N2O排放的影响过程复杂, 涉及因子颇多。大量研究表明, 施肥量及肥料种类, 土壤氮素含量与形态、温湿度、光强等因素可通过调控根系生长来影响作物从土壤中汲取水分和营养以及光合产物向根系的传导与分泌, 改变根际微域通气状况以及微生物赖以生存的碳氮源等营养成分, 进而影响根际微生物的群落结构、数量和活性以及在土壤中的分布, 由此介导根际微生物的硝化、反硝化过程, 影响根际土壤N2O生成、还原与排放。鉴于众多因素的影响, 作物根系生长对土壤N2O的生成与排放的影响具有促进或抑制双重作用, 其作用方向与强弱将影响农田生态系统中N2O的总体排放预算。因此, 研究作物根系对土壤N2O排放的调控作用及其对全球变暖的反馈机制势在必行, 对减少全球N2O排放预测的不确定性、减缓人类活动对全球变化的影响意义重大。

     

    Abstract: Agricultural land is a major source of nitrous oxide (N2O). N2O emissions are not only affected by agricultural management measures but are also closely related to the growth of crop roots. Root self-metabolism affects the formation and reduction of N2O in the rhizosphere soil and subsequently affects N2O emissions from farmland. The rhizosphere is an important interface of root-soil-microbial interactions and is the most direct and intense key area where roots affect soil N2O emissions. It is also a hotspot for soil N2O production in farmlands, and its share in farmland N2O emissions is prominent. Therefore, studies have widely focused on the mechanisms by which roots influence rhizosphere N2O emissions. In this study, relevant research was comprehensively reviewed to evaluate the research progress on the intensity of the influence of crop root growth on N2O emissions in farmland soil and the regulatory mechanisms of N2O production and emissions in the rhizosphere microdomain. Existing difficulties in studying the influence of crop root growth on N2O production and emissions in rhizosphere microdomain soil were also analyzed. Future related research is warranted. The effect of root systems on N2O emissions from farmlands is complicated and involves many factors. Many studies have shown that factors such as fertilizer application amount and type, soil nitrogen content and form, temperature, humidity, and light intensity can affect the water and nutrients extracted from soil, the conduction and secretion of photosynthetic products to the roots by regulating root growth, and change the rhizosphere microdomain aeration status and nutrients, such as the carbon and nitrogen sources that microorganisms depend on for survival. Furthermore, the community structure, quantity, and activity of rhizosphere microorganisms and their distribution in the soil are affected, which mediates the nitrification and denitrification processes of these microorganisms and affects N2O generation, reduction, and emission in the rhizosphere soil. Considering the influence of many factors, crop root growth can promote or inhibit soil N2O production and emission, and the direction and strength of its effects affect the overall N2O emission budget in farmland ecosystems. Therefore, it is necessary to study the regulatory effect of crop roots on soil N2O emissions and their feedback mechanisms on global warming, which is of great importance in reducing the uncertainty of global N2O emission predictions and mitigating the impact of human activities on global climate change.

     

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