Impact of grassland contract policy on soil organic carbon losses from alpine grassland on the Qinghai–Tibetan Plateau          下载免费PDF全文

J. Cao  Y. Gong  E. T. Yeh  N. M. Holden  J. F. Adamowski  R. C. Deo  M. Liu  J. Zhou  J. Zhang  W. Zhang  S. Zhang  D. Sheng  S. Yang  X. Xu  M. Li  Q. Feng 《Soil Use and Management》2017,33(4):663-671

Carbon storage in the soils on the Qinghai–Tibetan Plateau plays a very important role in the global carbon budget. In the 1990s, a policy of contracting collective grasslands to smaller units was implemented, resulting in a change from the traditional collective grassland management to two new management patterns: a multi‐household management pattern (MMP: grassland shared by several households without enclosures) and a single‐household management pattern (SMP: grassland enclosed and used by only one household). In 2016, 50 MMP and 54 SMP winter pastures on the Qinghai–Tibetan Plateau were sampled to assess the differences in soil organic carbon (SOC) between the two management patterns. Results showed that average SOC was significantly greater under MMP than under SMP, with an estimated 0.41 Mg C/ha/yr lost due to SMP following the new grassland contract. Based on the government's grassland policy, four grassland utilization scenarios were developed for both summer and winter pastures. We found that if the grassland were managed under SMP, likely C losses ranged between 0.31 × 10⁷ and 6.15 × 10⁷ Mg C/yr across the Qinghai–Tibetan Plateau relative to MMP, which more closely resembles pre‐1990s grassland management. Previous estimates of C losses have only considered land use change (with cover change) and ignored the impacts driven by land management pattern changes (without cover change). The new data suggest that C losses from the Qinghai–Tibetan Plateau are greater than previously estimated, and therefore that the grassland contract policy should be reviewed and SMP households should be encouraged to reunite into the MMP. These findings have potential implications for land management strategies not only on the Qinghai–Tibetan Plateau but also other grazing regions globally where such practices may exist.  相似文献   

体外产气法评价全株藜麦与全株玉米混合青贮饲料饲用价值     

路平乐  魏玉明  杨发荣  江小帆  李倩  赵生国  蔡原  焦婷 《草地学报》2021,29(11):2391-2398

为提高全株藜麦的饲料化利用率，寻找其与全株玉米的最佳青贮比，试验共设全株藜麦与全株玉米比为100：0，90：10，80：20等11个组合进行青贮发酵，发酵60 d后测定各组青贮料的体外产气发酵指标，使用灰色关联度分析筛选出最佳青贮比例。结果表明，体外发酵至36 h时，各处理组GP趋于稳定，体外发酵减弱接近停止；全株藜麦与全株玉米比例为90：10时，该青贮饲料组合的粗蛋白（CP）和粗脂肪（EE）含量显著高于其他各组（P<0.05），乙酸（AA）、总挥发性脂肪酸（TVFA）含量以及氨态氮（NH₃-N）浓度显著高于其他各处理（P<0.05）。分析表明，全株藜麦与全株玉米比例为90：10时，混合青贮饲料的营养品质和产气发酵特性综合表现最好，可作为优质混合青贮饲料在家畜养殖中推广使用。  相似文献   

A comparison of the effects of carbon dioxide and medical air for abdominal insufflation on respiratory parameters in xylazine-sedated sheep undergoing laparoscopic artificial insemination     

JD Haan  BL Hay Kraus  SR Sathe 《New Zealand veterinary journal》2018,66(4):167-171

AIMS: To determine if abdominal insufflation with medical air will improve oxygenation and ventilation parameters when compared to insufflation with CO₂ in xylazine-sedated sheep undergoing laparoscopic artificial insemination (AI).

METHODS: Forty-seven sheep underwent oestrus synchronisation and were fasted for 24 hours prior to laparoscopic AI. Each animal was randomised to receive either CO₂ or medical air for abdominal insufflation. An auricular arterial catheter was placed and utilised for serial blood sampling. Respiratory rates (RR) and arterial blood samples were collected at baseline, after xylazine (0.1?mg/kg I/V) sedation, 2 minutes after Trendelenburg positioning, 5 minutes after abdominal insufflation, and 10 minutes after being returned to a standing position. Blood samples were collected in heparinised syringes, stored on ice, and analysed for arterial pH, partial pressure of arterial O₂ (PaO₂), and CO₂ (PaCO₂). The number of ewes conceiving to AI was also determined.

RESULTS: Repeated measures ANOVA demonstrated temporal effects on RR, PaO₂, PaCO₂ and arterial pH during the laparoscopic AI procedure (p<0.001), but no difference between insufflation groups (p>0.01). No sheep experienced hypercapnia (PaCO₂>50?mmHg) or acidaemia (pH<7.35). Hypoxaemia (PaO₂<70?mmHg) was diagnosed during the procedure in 14/22 (64%) ewes in the CO₂ group compared with 8/23 (35%) ewes in the medical air group (p=0.053). Overall, 15/20 (75%) ewes in the CO₂ group conceived to AI compared with 16/22 (72.7%) in the medical air group (p=0.867).

CONCLUSIONS AND CLINICAL RELEVANCE: There were no statistical or clinical differences in RR, PaO₂, PaCO₂, pH, or conception to AI when comparing the effects of CO₂ and medical air as abdominal insufflation gases. None of the sheep experienced hypercapnia or acidaemic, yet 42% (19/45) of sheep developed clinical hypoxaemia, with a higher percentage of ewes in the CO₂ group developing hypoxaemia than in the medical air group. Based on the overall analysis, medical air could be utilised as a comparable alternative for abdominal insufflation during laparoscopic AI procedures.  相似文献   

天敌昆虫低温贮藏研究进展     

沈祖乐  李翌菡  周雅婷  许炜明  邱宝利 《热带作物学报》2017,(2):374-380

在农业生产中由于化学农药的长期不合理使用,导致"3R"问题持续存在和人类赖以生存的环境日益恶化,生物防治产品及技术在有害生物综合治理中的作用越发重要。天敌昆虫的生长发育及存活期往往很短,探索其储存技术是天敌昆虫规模化生产中的关键性环节。低温贮藏可以延长天敌昆虫的寿命,进而可以为生物防治提供充足、稳定的天敌产品。因此,天敌昆虫低温贮藏一直是生物防治领域研究的热点。本文围绕天敌昆虫低温贮藏这一环节,就低温诱导天敌昆虫滞育虫态、冷驯化对昆虫低温贮藏效果的影响、低温贮藏对天敌昆虫适合度(寿命、羽化率、性比、个体尺寸大小、飞行扩散能力等)的影响等方面进行综述,以期为天敌昆虫产品的规模化生产及应用技术提供参考。  相似文献   

Genotypic Variability in Biomass Protein and Nucleic Acids in Four Linum Species to Sodicity Stress     

A. K. Singh  B. B. Singh 《Journal of Agronomy and Crop Science》1991,167(1):1-7

Differences in gas exchange parameters i.e. carbon exchange rate (CER), transpiration (Tr), water vapor conductance (g) were investigated, under a controlled environment, in a semi-dwarf (SD) Triticum aestivum line, its tall (TL) near isoline and the Payne (PA) variety characterized by small leaves. The plants were maintained in: (a) optimal substrate moisture condition (CTR); (b) salinized by watering with a 0.12 m NaCl solution (SLT); (c) water stressed by withholding waterings during a period of six days (STR); (d) stressed and salinized during the same period and with the same saline solution (S + S). CER and Tr were negatively affected by the stresses; SLT and S + S treatments had a higher WUE compared to their respective controls CTR and STR.
SD line had a better performance in terms of CER and WUE, particularly when water and salt stresses interacted. Leaf anatomy and assimilation/internal CO₂ concentration curves contributed to explaining the SD performance.  相似文献   

原油管道改输天然气前的清管实践     

王振洪 《油气储运》2005,24(3):49-50

为保证原油管道改输天然气后的输气质量和运行安全,必须在管道输气前实施清管。介绍了新疆塔河油田四、六区块4-1计转站至1号联合站原来的原油集输管道改输天然气前的清管方案和清管步骤,分析了其清管效果,指出利用经清管检测达标后的原油管道改输天然气与再建输气管道相比,不仅施工周期短,工艺操作简单,而且还可节约大量的建设资金。  相似文献   

Studies on Tomato Seedling Quality Indices Under Simulated Shipping and Storage Conditions     

NING Wei  GE Xiao-guang  LI Tian-lai 《中国农业科学(英文版)》2004,3(12)

Indices of the tomato seedling quality maintenance level after production before field planting were studied through simulated experiments, small--scale operation, indoor analyses and measurements, and field observation. The results showed that under simulated shipping and storage conditions, seedling quality change following different durations (days) of shipping and storage was correlated significantly or even very significantly with certain physiological and morphological indices. With various measured indices following different periods of shipping and storage treatment subjected to multinomial successive regressive correlation analysis, the principal factors influencing seedling quality maintenance level are identified to be chlorophyll content→dry short weight→ leaf freshness index in order of their importance. Significance analysis with multinomial fitted equation indicated that correlations between any one of above three factors and the growth index after field planting reached very significant difference level.  相似文献   

有摩擦的高速气体管流     

朱文重 《湖南农业大学学报(自然科学版)》1990,17(2)

本文以多变热力过程为基础建立了有摩擦管路的计算公式,并对计算方法和有关问题作了分析说明.  相似文献   

输气管道的安全保证     

陈向新 《油气储运》1994,13(5):32-34

随着输气管道建设的发展，管道自身及其周围建筑物的安全保证问题，已引起人们高度重视，关于管道安全保证有两种指导思想：①距离安全保证模式，其设防原则是对管道自身强度有一定要求，主要通过控制不同压力，不同管径的管距建筑物的相应距离来保证管道及附近建筑物的安全；②强度安全保证模式，其设防原则是在管道设计，材料及设备选用，施工，检验，生产到更新改造的全过程中，对管道的强度和严密性有严格的要求，为管道系统及周  相似文献   

大型液化气低温储罐结构及其保冷设计   总被引：6，自引：0，他引：6  

陈江凡  邹华生  龚敏 《油气储运》2006,25(7):11-15

根据储存液化气大容量储罐的超低温特点，对液化石油气和液化天然气低温储存储罐的隔冷保温材料及其保温结构设计进行了研究，并对几种大型圆筒型立式储罐的结构设计及其技术经济特性进行了讨论和比较。  相似文献