施肥对青藏高原燕麦种子生产的增产效应

通过研究施肥水平对燕麦Avena sativa种子产量和品质的影响,筛选出适宜燕麦种子高产的施肥量,为提高燕麦种子生产能力提供直接的理论依据.研究结果表明:在试验设计的施氮梯度范围,施氮对燕麦产量和品质影响作用明显,施氮水平与种子蛋白质含量之间呈显著的线性回归关系(R=0.896 8,P＜0.01),随着施肥量的增加,蛋白质含量持续增加;而施氮水平与有效分蘖数、小穗数、草产量和种子产量之间呈显著的二次回归关系(P＜0.01),表现为"低-高-低"的变化趋势,施氮60 kg/hm2时燕麦种子产量为4358.5 kg/hm2,达到最高,施肥量继续增加,种子产量增幅下降,投入产出比降低.因此,从高产和高效角度综合考虑,生产中以收获燕麦种子为目的时,施氮量应选择60 kg/hm2,而以生产饲草为目的时,施氮量应选择75 kg/hm2.     

高寒草甸土壤微生物群落功能多样性对广布弓背蚁蚁丘扰动的响应

为了解蚂蚁在高寒草甸生态系统中的功能和作用,评估和认识高寒草甸生态系统的健康状况和稳定性,利用Biolog-ECO生态板法对蚁丘干扰后高寒草甸土壤理化性质以及土壤微生物功能多样性进行研究分析,结果表明,1)蚁丘扰动后0~10 cm土层土壤有机质、全氮、速效氮、速效磷、速效钾含量均显著高于蚁丘10~20 cm土层(P<0.05),而蚁丘扰动与土层深度的交互作用对理化性质均无显著影响(P>0.05);2)蚁丘干扰后高寒草甸土壤微生物多样性指数(Shannon-Weiner指数、Pielou指数、McIntosh指数和底物碳源利用数)有所增加;3)主成分分析表明蚁丘干扰对土壤微生物功能多样性产生了影响,改变了微生物代谢功能特征,土壤微生物利用的主要碳源是碳水化合物、氨基酸类和羧酸类;4)冗余分析表明土壤养分影响土壤微生物碳源代谢特征和功能。因此,由于蚂蚁的挖掘活动、有机质的累积等改变了蚁丘土壤微环境,进而改变了土壤微生物的碳源利用类型和代谢功能。     

In vitro susceptibility of Brachyspira hyodysenteriae to organic acids and essential oil components

The antibacterial potential of organic acids and essential oil components against Brachyspirahyodysenteriae, the causative pathogen of swine dysentery, was evaluated. Minimum inhibitoryconcentrations (MIC) of 15 compounds were determined at pH 7.2 and pH 6.0, using a broth microdilution assay.In addition, possible synergism was determined. MIC values for the three tested strains were similar. Fororganic acids, MIC values at pH 6.0 were lower than at pH 7.2. B. hyodysenteriae was mostsensitive to cinnamaldehyde and lauric acid, with MIC values <1.5 mM. Most antibacterial effects of binarycombinations were additive, however, for thymol and carvacrol, synergism could be observed. Invitro results demonstrate the antibacterial action of certain essential oil components and organicacids against B. hyodysenteriae.     

Resting metabolic rates increase with elevation in a mountain‐dwelling lizard

Individuals that inhabit broad elevational ranges may experience unique environmental challenges. Because temperature decreases with increased elevation, the ectotherms living at high elevations have to manage limited activity time and high thermoregulatory effort. The resting metabolic rate (RMR) of a postabsorptive animal is related to its total energy requirements as well as many other fitness traits. Mesquite lizards (Sceloporus grammicus) living on La Malinche Volcano, Mexico, inhabit a wide elevational range with some populations apparently thriving above the tree line. We measured the RMR of lizards from different elevations (i.e., 2,600, 3,200, and 4,100 m) at four ecologically relevant temperatures (i.e., 15, 25, 30, and 35 °C) and found that RMR of mesquite lizards increased with temperature and body mass. More importantly, lizards from the high‐elevation population had mass specific RMR that was higher at all temperatures. While the higher RMRs of high‐elevation populations imply higher metabolic costs at a given temperature these lizards were also smaller. Both of these traits may allow these high elevation populations to thrive in the face of the thermal challenges imposed by their environment.     

Assessment of impact of the introduction of exotic fish species in north-east Thailand

Abstract. Within the framework of a fisheries project in north-east Thailand, project MK/FSPC/069 entitled ‘The Fish Seed Production Centre, North East Thailand’, an assessment was carried out of the ecological impact of introducing exotic fish species (common carp, Cyprinus carpio L., Nile tilapia, Oreochromis niloticus (L.), and Chinese and Indian carps). For the assessment, the protocol of Kohler & Stanley (1984) was followed, covering feasibility of introduction, acclimatization potential, potential impact, and control potentials. Regarding the (ongoing) use of the proposed exotic species in aquaculture, it was concluded that so far no clear ecological impact has been reported from escapes to open water; the use of the exotic species has shown to be highly beneficial from a 9 socio-economic point of view. Regarding the proposed introduction of the exotic species into public waters (natural lakes and man-made reservoirs), it was concluded that earlier releases of these species in north-east Thailand did not provoke severe ecological impact in terms of deterioration of aquatic ecosystems. Incidental cases of minor ecological impact were reported for common carp and nile tilapia. Indications were obtained for niche competition between Chinese and Indian carps and indigenous carps, while similar niche competition was concluded for bighead carp, Aristichthys nobilis (Richardson), and indigenous pelagic zooplankton feeders. Observing the prolific development of the Nile tilapia in a number of reported cases, it was recommended not to include this species in stocking programmes for public water bodies, until more risk assessments are available.