内蒙古荒漠草原草库伦氮素补给与调控过程及其技术原理

Second only to water, nitrogen is the most important plant component able to dramatically hinder productivity of desert steppe. Long-term lack of supplemental nitrogen, desert steppe ecosystem may have poor nitrogen content, especially serious for enclosed pastureland. Previous research has identified problems with nitrogen management and explored soil nitrogen composition in desert steppe ecosystem. It was also discovered that forage legumes are genetically diverse and highly dynamic throughout populations. Meanwhile, soil nitrogen component of typical enclosed pastureland had been surveyed. The test of precipitation control in canopy, nutrient-deficient field trials, controlled-release nitrogen experiment, biochar of cow and sheep feces and leguminous grass reseeding trials will been carried out. Evaluative criteria included soil nitrogen content, soil moisture content, biomass accumulation and nitrogen nutrition habits over time. Interactions between water and nitrogen as well as carbon and nitrogen were investigated. Vegetation restoration of excellent forages was also observed. Valuable insights about technical approaches of nitrogen additions were gained as to these interactions and various mechanisms were discovered in the process. Coinciding this research to known principles which include water, carbon and nitrogen interaction can aid in development of better management principles to obtain high-quality enclosed desert steppe pasturelands. Prospects are good for further application and employment of these principles.

氮素是仅次于水分制约荒漠草原生产力的重要因素。长期不合理利用，导致荒漠草原生态系统"贫氮化"，草库伦格外严重。本项目根据草库伦氮素补给和调控实践中存在的问题，在研究了解典型草库伦土壤氮素组分和豆科牧草多样性特征及其变化规律的基础上，通过雨棚降水控制模拟试验、原位培养试验、田间氮肥肥效试验、牛羊粪便生物质炭试验以及豆科牧草补播等试验，分析测定土壤氮素组分及其含量、土壤水分动态、牧草生长及氮素营养习性等，研究了解水氮耦合作用、碳氮互作效应、优质牧草植被恢复过程，探索基于水氮耦合、碳氮互作和生物固氮作用与原理的氮素补给与调控技术途径，揭示其机制与原理，并提出基于水碳氮互作的荒漠草原优质草库伦建设及生产技术原理，研究成果将具有良好的推广应用前景。

荒漠草原具有高强度生产的鲜明特点，从而导致草库伦土壤氮素锐减，加剧了草原退化。本研究以不同类型的荒漠草原草库伦为研究对象，开展了不同类型草库伦土壤氮素的组成成分及变化规律研究，分析了不同利用强度下草库伦豆科牧草特征，研究了不同调控措施对荒漠草原草库伦土壤氮素供给的差异及对植被的影响，基于水氮控制试验和田间氮肥肥效试验，探索了荒漠草原草库伦氮素补给与调控技术途径。研究结果表明：（1）荒漠草原土壤氮素在空间上表现出南部及东南部显著高于北部和东部的分布格局。（2）不同水热分布区的荒漠草原土壤全氮分布格局不同，但总体表现为利用强度越高的地带土壤氮素垂直分布梯度受到破坏，表层土壤全氮含量高于深层土壤。利用强度较低的地带土壤深层全氮含量高于表层。（3）在荒漠草原豆科植物密度及盖度受水热的综合作用时影响不大，但是温度和湿度分别会对豆科植物密度及盖度产生显著影响。（4）控释肥料对退化草地的盖度、密度的影响差异不显著；但显著提高了地上生物量，促进退化草地恢复。（5）探索了制备羊粪生物质炭工艺流程，在200℃下，热解炭化20-30分钟，炭产率达到59.25%。（6）荒漠草原降水增大显著增加地上净初级生产力（ANPP）、地下净初级生产力（BNPP）、土壤有机碳（OC）和土壤总氮含量（TN），而降水减少显著降低BNPP、OC和TN含量。施加N素能显著增加草地ANPP、BNPP、OC和TN含量。降雨量的变化以及氮素添加下生物与非生物因素对生态系统的土壤呼吸有重要的调节作用。