Beaver herbivory and its effect on cottonwood trees: influence of flooding along matched regulated and unregulated rivers

We compared beaver (Castor canadensis) foraging patterns on Fremont cottonwood (Populus deltoides subsp. wislizenii) saplings and the probability of saplings being cut on a 10 km reach of the flow‐regulated Green River and a 8.6 km reach of the free‐flowing Yampa River in northwestern Colorado. We measured the abundance and density of cottonwood on each reach and followed the fates of individually marked saplings in three patches of cottonwood on the Yampa River and two patches on the Green River. Two natural floods on the Yampa River and one controlled flood on the Green River between May 1998 and November 1999 allowed us to assess the effect of flooding on beaver herbivory. Independent of beaver herbivory, flow regulation on the Green River has caused a decrease in number of cottonwood patches per kilometre of river, area of patches per kilometre, and average stem density within cottonwood patches. The number of saplings cut per beaver colony was three times lower on the Green River than on the Yampa River but the probability of a sapling being cut by a beaver was still higher on the Green River because of lower sapling density there. Controlled flooding appeared to increase the rate of foraging on the Green River by inundating patches of cottonwood, which enhanced access by beaver. Our results suggest regulation can magnify the impact of beaver on cottonwood through interrelated effects on plant spatial distribution and cottonwood density, with the result that beaver herbivory will need to be considered in plans to enhance cottonwood populations along regulated rivers. Published in 2002 by John Wiley & Sons, Ltd.     

工蜂采集蜂胶的行为观察及胶源植物的研究

蜂胶中大约50%成分来自植物树脂,不同地区的蜂胶具有不同的植物来源。本实验通过对工蜂采集蜂胶的行为进行观察,并运用高效液相色谱法（high performance liquid chromatography,HPLC）对加拿大杨树芽的树脂（简称加杨芽脂）、采胶工蜂后足上的树脂和蜂箱中蜂胶的多酚类成分进行分析。结果表明：加杨芽脂、工蜂后足上的树脂和蜂胶不仅在物理状态上非常接近,而且在化学成分及其相对含量上也很相似。因此,中国蜂胶的胶源植物是黑杨派中欧洲黑杨以及它的杂交品种--加拿大杨。     

加杨雄花序营养成分分析

对加杨雄花序的蛋白质、脂肪、膳食纤维、氨基酸、矿质元素、维生素等营养成分进行了分析测定，并与常用蔬菜的营养成分进行比较。结果表明，加杨雄花序中含有丰富的营养，其中蛋白质含量高达2．55％，脂肪含量达0．12％，粗纤维含量达1．31％，富含动物生长必需的微量元素和氨基酸,很值得进一步的开发利用。     

加杨雄花序提取物体外抗氧化及对 DNA损伤的保护作用研究

利用比色法、化学发光法,研究了加杨雄花序提取物体在体外对O2-·,·OH,H2O2活性氧自由基的清除作用,以及通过Cu2 -Phen-H2O2-Vit.C-DNA发光体系研究加杨雄花序提取物对·OH引起的DNA氧化损伤的保护作用。实验结果表明加杨雄花序提取物对O2-·,·OH,H2O2自由基均有明显的清除作用,其50%抑制浓度(IC50)分别为0.69、1.73、0.23mg/ml,并能显著抑制·OH对DNA氧化损伤。     

毛细管电泳间接激光诱导荧光法测定苦蒿和青蒿中酸性成分

利用毛细管电泳建立了中药苦蒿和青蒿及其制剂中11种酸性化合物的同时定量分析方法。其最佳电泳条件为:熔融石英毛细管50 cm(40 cm处检测窗口)×75μm i.d.;分离电压:+15 kV;分离温度:25℃;缓冲液(含:35.7 mmol/L磷酸钠,2.86×10-5mol/L荧光素钠,少量甲醇,pH=11.42);进样压力:0.5 psi(3.45 kPa),进样时间5.0 s;荧光素钠为激光诱导荧光响应试剂;LIF激发光波长:488 nm,检测波长:520 nm。该方法线性范围宽、相对标准偏差低、精密度高、重现性好,用于实际样品的测定,获得满意结果。     

微波辅助萃取-高效液相色谱法测定香丝草中槲皮素

采用微波辅助萃取法提取,以高效液相色谱法测定香丝草中的槲皮素。确定了微波辅助萃取法提取香丝草中槲皮素的最佳条件为:溶剂乙醇的体积分数为60%,微波辐射时间10 min,液固质量比45∶1,微波提取压力500 kPa。所得结果的相对标准偏差为1.13%².39%,回收率在99.75%2.39%,回收率在99.75%¹01.38%之间。     

Diet Breadth and Variability in Sander spp. Inferred from Stable Isotopes

We used stable isotopes of carbon and nitrogen to evaluate trophic similarity between sauger Sander canadensis and walleye S. vitreus in three Missouri River impoundments characterized by unique differences in riverine habitat. Mean δ¹⁵N was similar for sauger and walleye in each reservoir ranging from 15.7 to 17.8‰ for sauger and 15.2 to 17.7‰ for walleye. However, mean δ¹³C was greater for sauger (?24‰) than for walleye (?25‰) in Lake Oahe (lacustrine habitat), where rainbow smelt Osmerus mordax is an important prey species for walleye. Variation in δ¹⁵N and δ¹³C values was similar between walleye and sauger in Lewis and Clark Lake (riverine habitat), but was greater for sauger than for walleye in Lake Oahe, implying that in pelagic environments, sauger exhibit a larger diet breadth and lower diet consistency compared with walleyes. Isotope analyses support observations from traditional gut content studies that diet overlap between sauger and walleye varies with environmental conditions and is more similar in riverine food webs than in large lakes and impoundments. Copyright © 2015 John Wiley & Sons, Ltd.     

ICP-MS测定两种一枝黄花中12种微量元素

为确定两种一枝黄花中微量元素的差异,建立了微波消解-ICP-MS法,测定加拿大一枝黄花与一枝黄花中Ca、Mg、P、Fe、Mn、Ni、Cu、Zn、Se、Cr、Hg和Pb12种微量元素。方法的加标回收率为95.2%～107.1%,相对标准偏差在2.5%～8.9%之间,检出限在0.002～0.057μg.L-1之间,该方法具有良好的准确度和精密度。分析结果表明,加拿大一枝黄花与一枝黄花均含有Ca、Mg、P、Mn和Fe元素,前者中Ca、Cr、Mn、Zn、Pb、Ni含量较高,而后者中的Mg、P、Fe、Cu、Se含量较高。