Labile, recalcitrant, and microbial carbon and nitrogen pools of a tallgrass prairie soil in the US Great Plains subjected to experimental warming and clipping

Carbon (C) and nitrogen (N) fluxes are largely controlled by the small but highly bio-reactive, labile pools of these elements in terrestrial soils, while long-term C and N storage is determined by the long-lived recalcitrant fractions. Changes in the size of these pools and redistribution among them in response to global warming may considerably affect the long-term terrestrial C and N storage. However, such changes have not been carefully examined in field warming experiments. This study used sulfuric acid hydrolysis to quantify changes in labile and recalcitrant C and N fractions of soil in a tallgrass prairie ecosystem that had been continuously warmed with or without clipping for about 2.5 years. Warming significantly increased labile C and N fractions in the unclipped plots, resulting in increments of 373 mg C kg⁻¹ dry soil and 15 mg N kg⁻¹ dry soil, over this period whilst clipping significantly decreased such concentrations in the warmed plots. Warming also significantly increased soil microbial biomass C and N in the unclipped plots, and increased ratios of soil microbial/labile C and N, indicating an increase in microbial C- and N-use efficiency. Recalcitrant and total C and N contents were not significantly affected by warming. For all measured pools, only labile and microbial biomass C fractions showed significant interactions between warming and clipping, indicating the dependence of the warming effects on clipping. Our results suggest that increased soil labile and microbial C and N fractions likely resulted indirectly from warming increases in plant biomass input, which may be larger than warming-enhanced decomposition of labile organic compounds.     

Human case of bubonic plague resulting from the bite of a wild Gunnison's prairie dog during translocation from a plague‐endemic area

Plague is a zoonotic disease (transmitted mainly by fleas and maintained in nature by rodents) that causes severe acute illness in humans. We present a human plague case who became infected by the bite of a wild Gunnison's prairie dog, and a good practical example of the One Health approach that resulted in a rapid public health response. The exposure occurred while the animal was being transported for relocation to a wildlife refuge after being trapped in a plague enzootic area. This is the first report of a human plague case resulting from the bite of a Gunnison's prairie dog. Additionally, we present an observation of a longer incubation period for plague in captive prairie dogs, leading to a recommendation for a longer quarantine period for prairie dogs during translocation efforts.     

中国北方牧区草原牧业生态经济学透视

本文采用生态经济学的理论和方法 ,揭示了中国北方牧区草原雪灾背后的生态经济问题 ,中国北方草原牧业生态经济系统的主要特点是结构脆弱 ,功能低下。随着人口的高速增长 ,经济系统对生态系统的干预大大超过生态系统的自我调节能力 ,不合理的人类经济活动破坏了生态经济平衡 ,使草原生态系统严重退化 ,牧业经济系统陷于困境 ,系统抗灾能力降低。在缺乏有效生态经济管理的情况下 ,生态效益的外部性将不可避免地使生态经济系统矛盾更加尖锐化 ,系统运行陷入双轨恶性循环 ,并最终阻碍牧业经济持续发展     

建立中国草原生态补偿机制的依据、原则及配套政策研究

重林轻草、重政府投入轻民间参与、重有形价值轻无形价值已经成为我国生态建设中的普遍现象。本文从研究草地的价值贡献和我国草地严重的退化与沙化现状出发,分析了进行草原生态补偿的必要性和紧迫性,并在此基础上提出了对草原生态补偿的理论依据、原则和相应的政策建议。     

藏北高寒草原草地退化及其驱动力分析

藏北高寒草原是西藏畜牧业发展的核心区域.近年来,日趋严重的草地退化已从整体上影响并制约着区域经济的可持续发展.藏北高原自然环境严酷、生态系统脆弱,在全球变化的大背景下,随着人类干预强度和频度的不断提高,草地生态系统的退化正呈进一步加重的趋势.在阐述藏北高原草地退化现状的基础上,就藏北高原草地生态系统的退化成因进行了深入分析.     

甘南高寒草原面临的问题及对策

草原高寒资源是大自然的主体部分之一,是人类赖以生存和发展的物质基础,是维护生态平衡的重要环节。甘南草原是长江、黄河上游重要的水源补给和涵养区,在中国西部生态环境系统中处于十分重要的位置。保护和建设好甘南草原,不仅影响广大农牧民赖以生存的基本生产、生活资料,而且也维系着黄河、长江中下游地区的生态安危。     

丙酸对高水分紫色达利菊干草贮藏稳定性的影响

紫色达利菊是自然生长在草原上的一种重要豆科牧草,与苜蓿具有相似的饲喂价值。高水分打捆有益于缩短牧草的田间养护期,降低损失风险,但因水分高、易发霉而不易贮藏,从而影响牧草的营养价值和安全性。本试验研究了丙酸对高水分紫色达利菊干草贮藏稳定性的影响。结果表明,高水分打捆(28%)与低水分打捆(17%)的紫色达利菊干草具有相似的化学组分,但高水分打捆不利于干草的贮藏。添加一定浓度的缓冲丙酸降低了(P<0.05)高水分打捆干草贮藏后期的温度、pH及中性洗涤纤维和酸性洗涤纤维的含量,减少了细菌总数及霉菌和酵母菌的数量,增加了干草粗蛋白和水溶性碳水化合物的含量。综上所述,添加丙酸有利于提高高水分紫色达利菊干草的营养价值、饲用安全性和贮藏稳定性。     

A multi-scaled analysis of avian response to habitat amount and fragmentation in the Canadian dry mixed-grass prairie

Previous research has suggested that ducks and songbirds may benefit from prairie landscapes that consist primarily of contiguous grasslands. However, the relative importance of landscape-level vs. local characteristics on mechanisms underlying observed patterns is unclear. We measured effects of grassland amount and fragmentation on upland and wetland songbird and duck density and nest success, and on some nest predators, across 16 landscapes in southern Alberta, Canada. We compared these landscape-level effects with local-scale responses, including distance to various edges and vegetation characteristics. We also evaluated several statistical approaches to comparing effects of habitat characteristics at multiple spatial scales. Few species were influenced by grassland amount or fragmentation. In contrast, distance to edge and local vegetation characteristics had significant effects on densities and nest success of many species. Previous studies that reported effects of landscape characteristics may have detected patterns driven by local mechanisms. As a corollary, results were very sensitive to statistical model structure; landscape level effects were much less apparent when local characteristics were included in the models.     

Zanthoxylum piperitum (DC), a potential feeding deterrent for mammals: studies with Microtus ochrogaster (Wagner)

Total extract from the fruit of Szechuan pepper (Zanthoxylum piperitum DC), the volatile components of the extract and a non‐volatile fraction containing alkylamides (NVA fraction) are feeding deterrents for rats. The present study investigated the effectiveness of these natural repellents in prairie voles (Microtus ochrogaster Wagner). Two‐choice feeding trials were conducted during which food‐deprived voles were offered choices between oat‐bran wafers. In Experiment 1, 10 voles were given three sets of feeding trials, each 2 h long. Baseline consumption was established during the first set of two trials by offering a choice between two oat‐bran wafers dipped in ethanol, the control solvent. During the second set of two trials the voles were given a choice between an oat‐bran wafer dipped in ethanol and a wafer dipped in Zanthoxylum extract. During the third set the voles were given a choice between a wafer served on top of a screened dish containing a sample of ethanol and a wafer served on top of a dish containing a sample of extract. In this manner the voles were exposed to volatile compounds emanating from the extract but could not contact it. Wafers dipped in extract were almost completely avoided. The volatile components of extract also significantly reduced food intake. In Experiment 2, habituation to the volatile constituents of extract was examined in 16 Zanthoxylum‐naïve voles. Baseline consumption was established by offering two wafers served on top of screened dishes containing ethanol. This was followed by twelve tests during which a choice between a wafer served above a sample of ethanol and a wafer served above a sample of extract was given. The voles failed to habituate to the volatile components of extract, consistently consuming less of the wafers served above extract. In Experiment 3 a dose‐response curve to Zanthoxylum extract was established, using 12 stimulus‐naïve voles. After baseline consumption was established, the animals were given two tests each, presenting a choice between a control wafer and a wafer dipped in a dilution of extract (0.001–100 g liter^?1). Only concentrations of 10 and 100 g liter^?1 reduced food intake. In Experiment 4 the effects of the non‐volatile fraction of extract were compared to those of whole extract. Vegetable oil was used as solvent. Eight stimulus‐naïve voles were given two tests with a choice between an oil‐dipped and an extract‐dipped wafer. A second group of eight voles received two tests with a choice between an oil‐dipped and NVA‐dipped wafer. Extract‐dipped wafers were avoided, but the NVA fraction had no effect on food consumption. Copyright © 2004 Society of Chemical Industry     

草原短尾羊Brachyury蛋白多克隆抗体制备

【目的】克隆草原短尾羊Brachyury基因（即T基因）编码区（CDS）,并制备Brachyury蛋白特异性多克隆抗体,为草原短尾羊短尾表型机制研究提供重要的试验材料。【方法】提取草原短尾羊16 d胚胎的组织RNA,反转成cDNA,以cDNA为模板,采用PCR方法克隆草原短尾羊Brachyury基因CDS全长序列。将Brachyury基因CDS全长序列连接至pEASY-Blunt E1载体,构建原核表达载体pEASY-Blunt E1-Brachyury,并进行Nhe Ⅰ和EcoR Ⅰ双酶切鉴定。将原核表达载体导入RosettagamiB（DE3）大肠杆菌,并进行IPTG诱导表达,对表达产物进行回收纯化。利用纯化后的表达产物免疫6周龄日本大耳白兔,用间接ELISA（iELISA）法测定血清多克隆抗体效价。以制备的多克隆抗体为一抗,采用Western blot法检测草原短尾羊16,20,25和30 d胚胎中Brachyury蛋白的表达水平。【结果】克隆了1 335 bp的草原短尾羊Brachyury基因CDS全长序列,成功构建了原核表达载体pEASY-Blunt E1-Brachyury,表达获得了49.16 ku的重组Brachyury蛋白。成功制备了重组Brachyury蛋白多克隆抗体,抗体效价达1∶1 500,该多克隆抗体可以特异性识别草原短尾羊胚胎中的Brachyury蛋白。草原短尾羊16 d胚胎中Brachyury蛋白的表达量最高。【结论】成功制备草原短尾羊Brachyury蛋白兔血清多克隆抗体,抗体效价为1∶1 500,该多克隆抗体可以特异性识别草原短尾羊胚胎中的Brachyury蛋白。