补饲对放牧藏羊排泄物氮迁移转化的影响及机制研究

The Qinghai-Tibetan Plateau is not only the cradle and water source of many big rivers in China and also one of the important rangeland based animal husbandry base which has the key ecological status. As the strengthening support of central government for the rural area in China, it has been more and more popular to feed grazing livestock with supplementary in the Qinghai-Tibetan Plateau. The supplementary will increase the N and energy content of the excreta for the increasing of N intake by livestock. All these changes may influence the decomposition rate and the way that N return of excreta and will affect the transformation and distribution models of the excreta N between livestock, soil and forage and result in a series of environmental problems. Thus, we are playing to the experiment focus on the influence of supplementary on the decomposition rate of Tibetan sheep excreta and N transformation on the field. The purposes of this research are to quality the relationship between N intake and N excretion, to explore the influence of supplementary on excreta decomposition and N releasing and its mechanism and the potential environmental effects. The results may provide the theoretical basis for the healthy management of Qinghai-Tibetan alpine meadow.

青藏高原生态地位重要，既是众多大江大河的发源地，也是我国主要的草原畜牧业基地之一。随着国家对牧区支持力度的加大，放牧与补饲相结合的生产方式在青藏高原牧区日益普遍。补饲增加了放牧家畜N摄入量，同时也会改变放牧家畜排泄物的N含量和能量特征，这些变化将影响到放牧家畜排泄物分解速率和N返还途径，以及排泄物N在牧草—土壤—环境间的迁移转化和分配，并产生诸多环境问题。因此，本项目拟在青藏高原高寒草甸开展野外控制试验，研究补饲对放牧藏羊排泄物分解和N迁移转化的影响，试图明确补饲N与放牧藏羊排泄物N迁移转化的定量关系，探索补饲对放牧藏羊排泄物分解与氮释放途径的影响及作用机理和可能引起的环境效应，以期为高寒草甸生态系统的健康管理提供理论基础。

本项目在甘肃玛曲高寒草甸结合家畜和野外定位试验，定量研究了补饲对高寒草甸放牧藏羊排泄物分解与氮释放途径的影响及作用机理。目前已发表论文4篇，其中SCI论文2篇，国际会议论文2篇, 已授权国家发明专利1项，申报专利2项, 4名研究生依托本项目完成学位论文。项目任务书中所有目标均已完成。.主要研究结果如下：(1) 初步明确了高寒草甸放牧藏羊羊粪N分解规律。发现高寒草甸藏羊羊粪N分解过程以气态氮形式分解为主，第1年通过气态挥发过程损失的粪氮占其总氮含量的40.3%。(2) 初步明确了高寒草甸羊粪气态形式损失特征。发现夏季是羊粪中的物质通过气态形式损失的旺季，其中氧化亚氮的排放速率可达春季和冬季的4倍。(3) 初步确定了藏羊尿和粪氮排放量与蛋白补饲量的关系。放牧藏羊蛋白采食量（CPI）与尿氮排出量（UN）的关系为：UN= 0.4503 CPI + 1.6164，与粪氮排出量（FN）的关系为:FN= 0.1304 x CPI + 13.412。补饲会极大的增加藏羊尿氮排出量，增幅远高于粪氮排出量。补饲后放牧藏羊通过排泄物进入草地的氮中，约77.5%来自尿氮，其它22.5%来自粪氮。(4) 初步确定了影响藏羊羊粪分解速率的主要因子。发现对羊粪分解速率影响较大的因素主要为：放牧率、环境因素和羊粪有机物含量。.研究成果可为高寒草甸生态系统的健康管理提供理论基础。