海南农牧生产体系氮素养分流动时空变化特征

氮素是生命活动必须的元素之一，然而一定区域内过多的氮素输入可能会造成严重的环境污染。本研究以热带地区的海南岛为研究对象，明确其农牧生产体系氮素流动过程和特征，分析氮素输入和输出量变化关系及其利用效率的时空变化，以期优化农牧体系养分管理，为制定海南省农牧业发展政策提供科学依据。通过运用食物链养分流动模型（NUtrient flows in Food chains，Environment and Resources use，NUFER）并结合Origin和ArcGIS等软件分析海南地区1987-2016年间农牧生产体系氮素养分流动时空变化特征，同时首次对海南省农牧生产体系内部氮素流动在理想与实际情况下的时空变化做出了相关性分析。结果显示海南地区30年间农牧生产体系氮素总输入量由134.15 Gg增长到406.39 Gg，总输出氮素由84.75 Gg增长到307.77 Gg。30年来，农田生产子系统氮素利用效率由12.39%增长到20.54%，动物生产子系统氮素利用率由6.10%增长到13.88%，农牧结合体系氮素利用效率整体呈现上升趋势，由1987年的12.84%增加到2016年的21.63%。空间上，农田生产子系统中，氮素总输入与总输出项中增幅最高的分别是澄迈县和琼海市，五指山市两项增长均最低；动物生产子系统中，氮素总输入与总输出项增幅最高的分别是文昌市和儋州市，五指山市两项增长均最低。1987-2016年海南岛农牧生产体系氮素投入持续增长，氮素利用率低下，空间差异较大，土壤氮素盈余量较高。相关性分析表明，农田生产子系统与动物生产子系统出现较严重的脱节。因而，为提高海南地区氮素流动效率和促进可持续发展，应注重提高本地饲料产量、合理使用肥料、循环利用畜禽粪尿，进一步优化农牧业发展布局，建立农牧结合的高效生产体系。

Spatial and temporal characteristics of nitrogen flows in farming and animal production system in Hainan Province

Though nitrogen is one of the necessary elements for life activities, its'' excessive input in a region may cause serious environmental pollution. Hainan Island, a province in the tropics, was taken as the research object to investigate the process and characteristics of nitrogen flows in farming and animal production system. To optimize the nutrient management of this system, the relationships of nitrogen input and output changes and the temporal and spatial characteristics of nitrogen utilization efficiency were analyzed, which would provide scientific basis for the policy setting of agriculture and animal husbandry development in Hainan province. The model of NUtrient flows in Food chains, Environment and Resources use (NUFER) combining with Origin and ArcGIS software were used to analyze the temporal and spatial changes of nitrogen flows in farming and animal production system in Hainan Province from 1987 to 2016, meanwhile for the first time, the correlation of spatial and temporal variations of nitrogen flows in the farming and animal production system was analyzed under ideal and actual conditions. The results showed that the total nitrogen input increased from 134.15 Gg to 406.39 Gg, the total nitrogen output increased from 84.75 Gg to 307.77 Gg in the past 30 years. The nitrogen utilization efficiency of the farming production subsystem increased from 12.39% to 20.54%, and that of the animal production subsystem increased from 6.10% to 13%. The nitrogen utilization efficiency of the integrated system of farming and animal production increased from 12.84% in 1987 to 21.63% in 2016. In spatial distribution, the increase of total nitrogen input and output was the highest in Chengmai County and Qionghai City, respectively, while being the lowest in Wuzhishan City. In the animal production subsystem, the increase of total nitrogen input and output was the highest in Wenchang City and Danzhou City, respectively, while being the lowest in Wuzhishan City. The results show that the nitrogen input of farming and animal production system in Hainan Island increased continuously from 1987 to 2016, with the low nitrogen utilization efficiency, the big spatial difference, and the high soil nitrogen surplus. The correlation analysis showed that the farming production subsystem and the animal production subsystem were disjointed seriously. Therefore, in order to improve the efficiency of nitrogen flows and promote the sustainable development in Hainan Province, it is necessary to increase the yield of local feedstuff, make rational use of fertilizer, recycle livestock and poultry manure, further optimize the layout of agriculture and animal husbandry development, and establish a highly efficient production system for farming and animal husbandry.