Seasonal Losses of Surface Litter in Northern Great Plains Mixed-Grass Prairies

Surface litter protects rangeland soils against wind and water erosion and provides food and nesting materials for wildlife and insects. However, the ability of grassland systems to provide these services depends on the little studied topic of seasonal surface litter decomposition. Seasonal and annual surface litter decomposition rates were determined between 2014 and 2015 in central and western South Dakota at three mixed-grass prairie locations. Residue bags containing surface litter were placed in the field in late fall (1 November) of 2014 and removed after the winter (1 April), spring (1 July), and summer + fall seasons (1 November) of 2015. The litter was analyzed for total C, total N, acid detergent fiber (ADF), and acid detergent lignin (ADL). Average winter temperatures ranged from −5^oC to −15^oC, while summer temperatures ranged from 10^oC to 35^oC. Litter decomposition was lowest during the winter (0.57−0.86 g [kg × day]⁻¹) and greatest during the summer + fall (2.12−2.69 g [kg × day]⁻¹). Over the entire season, 40.8−62% of the surface litter decomposed. Winter litter decomposition was positively correlated with air temperature (r = 0.62, P < 0.01) and snow depth (r = 0.61, P < 0.01), and negatively correlated with C/N ratio (r = −0.65, P < 0.01), ADF (r = −0.35, P < 0.05), and ADL (r = −0.25, P < 0.05) concentrations. These findings indicate that winter decomposition cannot be ignored and that winter surface litter decomposition increases with snow depth.     

Mitigation of N2O emissions from grassland by nitrification inhibitor and Actilith F2 applied with fertilizer and cattle slurry

Abstract. Nitrous oxide (N₂O) is involved in both ozone destruction and global warming. In agricultural soils it is produced by nitrification and denitrification mainly after fertilization. Nitrification inhibitors have been proposed as one of the management tools for the reduction of the potential hazards of fertilizer-derived N₂O. Addition of nitrification inhibitors to fertilizers maintains soil N in ammonium form, thereby gaseous N losses by nitrification and denitrification are less likely to occur and there is increased N utilization by the sward. We present a study aimed to evaluate the effectiveness of the nitrification inhibitor dicyandiamide (DCD) and of the slurry additive Actilith F2 on N₂O emissions following application of calcium ammonium nitrate or cattle slurry to a mixed clover/ryegrass sward in the Basque Country. The results indicate that large differences in N₂O emission occur depending on fertilizer type and the presence or absence of a nitrification inhibitor. There is considerable scope for immediate reduction of emissions by applying DCD with calcium ammonium nitrate or cattle slurry. DCD, applied at 25 kg ha^–1, reduced the amount of N lost as N₂O by 60% and 42% when applied with cattle slurry and calcium ammonium nitrate, respectively. Actilith F2 did not reduce N₂O emissions and it produced a long lasting mineralization of previously immobilized added N.     

新疆草地优势种植物相对生物量沿海拔梯度变化特征

优势种作为草地生态系统中地上生物量的主要贡献者,其生物量既受到环境因素的影响,也受到共存种种间关系的影响。然而,由于物种的不同和环境梯度的差异,目前有关优势种生物量与环境因素关系的研究,尚未获得一致性的结论。基于此,本研究以2011-2013年对新疆9种草地类型397个样地中优势种相对生物量的调查数据为基础,首先统计了不同草地类型中优势种组成,其次通过一般线性模型分析了优势种相对生物量随海拔梯度变化特征,以及共存优势种相对生物量之间的关系。结果显示：1）新疆草地共有169个优势种,隶属31科120属。这些优势种主要以禾本科植物为主,占据了优势种的19.53%。其中,高寒草原、温性草甸草原、温性草原、温性荒漠草原和温性草原化荒漠中,最主要的优势种均为针茅。而在高寒草甸、山地草甸和温性荒漠中,最主要的优势种则分别为珠芽蓼、千叶蓍和角果藜;2）优势种相对生物量与海拔的关系可以归为5类,分别呈现无显著关系、先降低后升高的U型变化趋势、显著正相关关系、显著负相关关系和先增加后降低的单峰型关系。这5类关系所对应的优势种数量分别为50、9、8、6和4个,分别占优势种总数的64.9%、11.7%、10.4%、7.8%和5.2%;3）24个共存优势种之间,其相对生物量共存在19对显著关系,且大多数共存优势种相对生物量之间主要表现为负相关关系。本研究表明,优势种相对生物量与海拔的关系,因物种不同呈多种变化格局且受到共存优势种的影响,结果可对未来新疆草地地上生物量的维持和管理,提供一定的参考依据。     

三江源区不同高寒草地植物矿物元素含量特征及分析

本试验对三江源区不同高寒草地植物中6种矿物元素（钾K,钙Ca,钠Na,镁Mg,锌Zn,铁Fe）的含量进行了测定和分析,结果表明：植物中K元素含量为7.314～12.803 g·kg^-1之间,Ca元素含量为2.851～6.823 g·kg^-1之间,Na元素含量为64.404～185.553 mg·kg^-1之间,Mg元素含量为1.272～2.655 g·kg^-1之间,Zn元素含量为14.718～51.387 mg·kg^-1之间,Fe元素含量为161.056～531.677 mg·kg^-1之间;豆科（Leguminosae）植物和杂类草（Forbs）矿物元素含量显著高于禾本科（Gramineae）和莎草科（Cyperaceae）植物;植物中K元素与Mg元素、Ca元素与Na元素、Ca元素与Zn元素、Na元素与Zn元素含量之间呈极显著正相关关系（P<0.01）,Ca元素与Fe元素、Mg元素与Fe元素之间呈显著正相关关系（P<0.05）;根据美国国家研究理事会（National research council,NRC）绵羊日粮矿物元素需求标准,三江源区各草地植物中Na,Zn元素相对缺乏,其它4种元素均能满足放牧藏羊的矿物营养需求。     

松嫩盐碱草原混播草地组合试验研究

为研究草原盐碱化治理中遇到的问题,试验采用不同土壤处理苜蓿与披碱草混播的试验设计,共设计5种处理组合,结果表明,不同处理间以施微生物有机肥处理产草量最高.说明适当的施肥处理和混播处理可以修复盐碱草地,环境条件的改变会加速生态环境的恢复.     

江河源区退化草地鼠害的治理研究

针对江河源区草场退化、高原鼠兔危害严重的状况,采用了翻耕、耙耱、撒播、轻耙、镇压等一系列治理措施.结果表明,这种以生态工程为主的治理措施,不仅使草场植被在短期内得到恢复,而且害鼠种群数量也得到了有效控制;同时,为防止鼠兔数量回升、减少扩散、播种牧草幼苗免遭啃食和挖掘破坏,在不同处理区又采取了以药物防治为辅的控制措施.在现场药效试验和大面积灭鼠中,0.075%敌鼠钠盐、0.1%C型肉毒杀鼠素和0.1%D型肉毒杀鼠素毒饵对鼠兔均具有良好灭效,且不污染环境,无二次中毒,对保护天敌、发挥生物控制危害具有一定意义.因此,在退化草场鼠害治理中,综合分析各组分之间的相互关系,有针对性地进行治理,才能收到良好效果,从而达到综合治理的目的.     

人为干扰对典型草原土壤侵蚀影响的价值评价

基于不同干扰条件下典型草原风洞试验的研究结果,计算了风蚀所造成的各种损失(养分、有机碳的损失及废弃地的形成等等),在此基础上,定量评价了人为干扰对土壤侵蚀过程的影响。研究结果表明,禁牧可以明显减小由风蚀所导致的草原生态系统的价值损失,而开垦和放牧则会增加其价值损失(包括速效养分、有机碳和废弃地形成)。总的来看,不同风速下不同生态系统的价值损失速率由大到小的排列顺序为:新开垦农田>农田>自由放牧草原>2003年禁牧草原>1987年禁牧草原;同时,风速越大不同干扰类型之间的价值损失差值越大。     

西部退耕还林还草后鼠类群落改变的现状调查

对青海省大通县退耕还林还草地及周边农田鼠类群落组成进行调查研究,在退耕还林还草地共捕获鼠类6种728只,以根田鼠和高原鼢鼠为优势种;农田中共捕获各种鼠类3种75只,以长尾仓鼠为优势种。比较发现,退耕还林还草后,鼠类群落组成发生了明显的变化,与之相适应,鼠害治理应针对不同的鼠类种群和危害程度采取相应的控制措施。     

波尔山羊杂交优势利用与南方灌丛草地开发

波尔山羊是目前世界上最优良的肉用山羊品种之一,国外研究及笔者在国内的试验表明,波尔山羊对本地低产山羊的杂交改良效果十分显著,因而可利用其杂交优势发展高效肉羊生产,高效肉用山羊生产系统的建立,对我国南方丰富的天然灌丛草地资源的开发利用具有交大的潜在价值,可为南方草地畜牧业提供新的发展途径,