| 三江源区草地生态畜牧业合作社模式下“土-草-畜-水”氮素流动与平衡 | |
| Alternative Title | Nitrogen flow and balance of "soil-grass-livestock-water" in ecological animal husbandy cooperatives in The Three Rivers Source Region on Tibetan plateau |
| 宋甜儿 | |
| Subtype | 硕士 |
| Thesis Advisor | 郭瑞英 ; 尚占环 |
| 2021-05-19 | |
| Degree Grantor | 兰州大学 |
| Place of Conferral | 兰州 |
| Degree Name | 理学硕士 |
| Degree Discipline | 生态学 |
| Keyword | 青藏高原 三江源区 生态畜牧合作社 氮循环 15N 稳定同位素技术 生态集约化 |
| Abstract | 为解决青藏高原草畜矛盾，近些年在国家政策支持下，生态畜牧业合作社经营模式在青藏高原得到了较快发展。生态畜牧业合作社的草地畜牧业具有生态集约化的特征，那么可持续性的养分管理就需要纳入到生态畜牧业合作系统中。对大多数高寒草地畜牧业系统而言，氮素是限制生产力最为重要的因素之一，因此研究氮素在以生态畜牧业合作社为经营单元的土-草-畜-水中的贮量动态和变化规律，对生态畜牧业合作社经营中合理利用草原、科学施肥、补充草地氮营养，使草原保持氮平衡，维持草地生产力可持续性具有重要意义，是生态畜牧业合作社可持续经营的重要科学依据。 该研究选取了青藏高原三江源区三个典型的生态畜牧业合作社及其对照牧户单营的草地和家畜系统中土壤、植物、家畜粪便、周围水体为研究对象，测定这些组分中全氮含量和稳定氮同位素δ15N值，旨在通过氮素在土-草-畜-水各个环节的运转和循环过程，揭示氮储量动态变化并利用15N自然同位素技术追踪不同环节的氮素来源与流向，最后通过明确氮输入和氮输出过程定量研究草地系统氮流动空间特征，揭示在三江源区生态畜牧业合作社草地-畜牧系统氮循环的平衡状况，为生态畜牧业合作社实现生态集约化和可持续管理提供科学参考。主要研究结果如下： （1）两种管理模式下草地的土壤全氮、可溶性总氮与可溶性无机氮（铵态氮与硝态氮）储量季节动态均呈现倒V字变化，而可溶性有机氮储量的季节动态则呈现相反的变化。 （2）畜牧业的集约化经营显著提高了天然草地土壤氮储量（可达9421.9 kg/ha），在整个生长季植被氮素吸收量与土壤无机氮基本能够维持平衡，无机氮以NH4+-N为主，提高了氮的利用性。草地的退化和开垦种植都会导致土壤中氮储量的下降，降低草地生产力。退化草地的植被氮素吸收量与土壤无机氮供应虽然基本能达到供需平衡，但从试验数据上可以清楚的反映出可溶性无机氮占到可溶性总氮的绝大部分（合作社与牧户单营土壤可溶性无机氮分别占可溶性总氮的82.32%、72.61%），使得草地土壤中固定的无机氮逐渐增加，成为无效消耗。经过人工种植的恢复草地，氮素吸收量与土壤无机氮供应虽然也基本能达到供需平衡，但通过对比两种无机氮储量占可溶性总氮的比例可以看到，牧户单营模式下的人工草地NO3--N（49.50%）显著高于NH4+-N（8.12%），草地渗透性差;合作社人工种植燕麦地在7月下旬至9月下旬收割前，土壤无机氮对植物氮素吸收量供应明显不足。 （3）家畜粪便是本研究中草地周围四条河流NO3-的主要来源，对于流经施肥人工草地的河流来说，化肥中的NO3-（或NH4+经矿化作用产生的NO3-）是水体内NO3-的第二大来源;而对于不施肥的草地来说，土壤内有机氮经过矿化及硝化等反应产生的NO3-是水体内的NO3-第二大来源。 （4）在两种管理模式下的草地生态系统中，牧草-土壤阶段δ15N值富集因子在0.549‰~2.932‰之间;家畜-土壤阶段δ15N值富集因子在1.128‰~2.293‰之间;水体-土壤阶段δ15N值富集因子在3.674‰~4.340‰之间。而牧草-家畜营养级上升的过程中，其富集在退化草地和天然草地两种不同草地类型间出现截然相反的作用：退化草地牧草-家畜阶段稳定氮同位素出现了极弱的甚至是负的富集作用，而天然草地的家畜则富集了来自牧草的氮稳定同位素。 （5）通过比对合作社模式和牧户单营模式下三种草地类型（近似未退化天然草地、人工草地和退化天然草地）的氮平衡账户，可以看出合作社模式下不同草地类型间单位面积氮输入和输出差异较大，特别是禁牧草地氮利用率较低，总体呈现氮素盈余的状态;而牧户单营模式下三种草地类型虽然氮素利用率较合作社高，但总体呈现氮素亏损的状态，草地生产力较低。 综上所述，三江源区生态畜牧业合作社的发展不仅在一定程度上实现了人、草、畜的整合，使得当地草地畜牧业向规模化、集约化的方向发展，增加了牧民的收入结构，带动了当地经济的发展，更是通过退牧还草的措施提高了天然草地养分存储能力，优化了氮平衡账户，提高了草地生产力。在未来的合作社规模化发展过程中，应注重退化草地养分管理及草地综合水平的提高，优化人工草地施肥和家畜粪便的管理，吸引更多牧户入社，同时加强对周围河流水体养分的监测，防止过度的集约化畜牧业引发的潜在环境风险，促进生态畜牧业合作社实现生态集约化经营管理，从而实现青藏高原三江源区合作社可持续发展。 |
| Other Abstract | In order to solve the grass-livestock contradiction on the Tibetan plateau, the ecological livestock cooperative business model has been developed faster on the Tibetan plateau in recent years with the support of national policies. Grassland animal husbandry in ecological livestock cooperatives has the characteristics of ecological intensification, then sustainable nutrient management needs to be incorporated into the ecological livestock cooperative system. For most alpine grassland livestock systems, nitrogen is one of the most important factors limiting productivity. Therefore, studying the dynamics and changes of nitrogen storage in "soil-grass-livestock-water", which are operated by ecological livestock cooperatives, is important for the rational use of grassland, scientific fertilization, and replenishment of grassland nitrogen in ecological livestock cooperatives. It is an important scientific basis for the sustainable operation of ecological livestock cooperatives, which is to maintain the nitrogen balance of grassland and maintain the sustainability of grassland productivity. In this study, the soil, plants, livestock manure, and surrounding water bodies in the grassland and livestock systems of three typical ecological livestock cooperatives and their control herders in The Three-River Source Region of the Qinghai-Tibet Plateau were selected as the research objects, and the total nitrogen content and stable nitrogen isotope δ15N values in these components were measured. The aim is to reveal the dynamic changes of nitrogen storage through the operation and circulation process of nitrogen in each link of "soil-grass-animal-water"and to trace the source and flow direction of nitrogen in different links by using 15N natural isotope technology. The main results are as follows. The main results of the study are as follows. (1) The seasonal dynamics of total nitrogen, total soluble nitrogen and soluble inorganic nitrogen (ammonium nitrogen and nitrate nitrogen) in grassland soils showed inverted "V"changes, while the seasonal dynamics of soluble organic nitrogen storage showed opposite changes. (2) The intensive management of alpine grassland animal husbandry significantly increased the soil nitrogen storage of natural grassland (up to 9421.9 kg/ha), and the balance between vegetation nitrogen uptake and soil inorganic nitrogen could be maintained throughout the growing season, and inorganic nitrogen was mainly NH4+-N, which improved the nitrogen utilization.Both degradation of ecological livestock cooperatives'grasslands and reclaimed cultivation will lead to a decrease in soil nitrogen storage and reduce grassland productivity. Although the vegetation nitrogen uptake and soil inorganic N supply of degraded grassland can basically reach a balance between supply and demand, it can be clearly reflected from the experimental data that soluble inorganic N accounts for the vast majority of total soluble N (82.32% and 72.61% of total soluble inorganic N in the soil of cooperatives and herders'single camps, respectively), making the fixed inorganic N in grassland soil gradually increase and become ineffective consumption . Although the nitrogen uptake and soil inorganic N supply of the restored grassland after artificial planting can also basically reach the balance of supply and demand, it can be seen by comparing the ratio of two kinds of inorganic N storage to total soluble N. The NO3--N (49.50%) of the artificial grassland in the pastoralist single-camp model is significantly higher than NH4+-N (8.12%), and the grassland is poorly permeable;the cooperative's artificially planted oatland is not well permeable from late July to Before harvesting in late July to late September, the supply of soil inorganic N to plant N uptake was significantly insufficient. (3) Livestock manure was the main source of NO3-in the four rivers around its grassland. For rivers flowing through fertilized artificial grassland, NO3-in fertilizer (or NO3-produced by mineralization of NH4+) was the second largest source of NO3-in the water body;while for the non-fertilized grassland, NO3-produced by organic nitrogen in the soil through mineralization and nitrification and other reactions was the The second largest source of NO3-in the water body. (4) In the grassland ecosystem underthe two management modes, the δ15N enrichment factor of pasture-soil stage ranged from 0.549‰to 2.932‰;the δ15N enrichment factor of livestock-soil stage ranged from 1.128‰to 2.293‰;and the δ15N enrichment factor of water-soil stage ranged from 3.674‰to 4.340‰. In contrast, the enrichment in the process of rising pasture-livestock trophic level showed diametrically opposite effects between two different grassland types, degraded grassland and natural grassland: the stable N isotopes in the pasture-livestock stage of degraded grassland showed extremely weak or even negative enrichment, while the livestock in natural grassland enriched the N stable isotopes from pasture. (5) By comparing the nitrogen balance accounts of three grassland types (nearly undegraded natural grassland, artificial grassland and degraded natural grassland) under the cooperative model and the herding monoculture model, it can be seen that there are large differences in nitrogen input and output per unit area among different grassland types under the cooperative model, especially the nitrogen utilization rate of the rangeland is lower and the overall state of nitrogen surplus is shown;while the nitrogen utilization rate of the three grassland types under the herding monoculture model, although In contrast, although the nitrogen utilization rate of the three grassland types under the herding monoculture model was higher than that of the cooperatives, the overall state of nitrogen deficit was observed, and the productivity of the grassland was lower. In summary, the development of ecological livestock cooperatives in The Three-River Source Region not only realized the integration of human, grass and livestock to a certain extent, which made the local grassland livestock industry develop in the direction of scale and intensification, increased the income structure of herders and drove the development of the local economy, but also improved the nutrient storage capacity of natural grassland through the measure of "returning grazing to grass", and optimized the nitrogen storage capacity of natural grassland. It also improves the nutrient storage capacity of natural grassland through the measure of "returning pasture to grass", optimizes the nitrogen balance account, and improves the productivity of grassland. In the process of future cooperative scale development, we should pay attention to the nutrient management of degraded grassland and the improvement of the comprehensive level of grassland, optimize the management of artificial grassland fertilization and livestock manure, attract more herding households to join the cooperative, and strengthen the monitoring of nutrients in the surrounding river water bodies to prevent the potential environmental risks caused by excessive intensive animal husbandry, and promote the ecological livestock cooperative to realize ecological intensive management, so as to realize The sustainable development of the cooperative in The Three-River Source Region of the Tibetan plateau. |
| Pages | 153 |
| URL | 查看原文 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | https://ir.lzu.edu.cn/handle/262010/460963 |
| Collection | 生命科学学院 |
| Affiliation | 生命科学学院 |
| First Author Affilication | School of Life Sciences |
| Recommended Citation GB/T 7714 | 宋甜儿. 三江源区草地生态畜牧业合作社模式下“土-草-畜-水”氮素流动与平衡[D]. 兰州. 兰州大学,2021. |
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