Relationships between urbanization and the oak resource of the Minneapolis/St. Paul Metropolitan area from 1991 to 1998

Urbanization was associated with loss and transformation of the oak forest in the Twin Cities (Minneapolis and St. Paul) metropolitan area (TCMA) over a recent 7-year interval. Between 1991 and 1998, urbanization increased based on several indicators: population density, area of developed land, and area of impervious surface—total impervious area and area within three classes of increasing degree of imperviousness (protected, affected, and degraded). We quantified relationships between changes in urbanization and changes in several parameters describing the oak forest at the scale of ecological subsection. Increased total and affected impervious area were strongly correlated with decreased area of oak forest when changes of the urbanization indicators and oak were expressed as percentages of the subsection area. Relationships were reversed when changes were expressed as percentages of the 1991 values. Increased population density was strongly correlated with increased loss in numbers and increased isolation of oak patches, but weakly correlated with loss of oak forest area. This is the first study to quantify relationships between changes in urbanization and changes in a specific forest cover type. Our results demonstrate complexities of urbanization impacts on a metropolitan forest resource, and highlight the importance of selected variables, spatial and temporal scales, and expressions of change when quantifying these relationships.     

Induced Defensive Response of Myrtle Oak to Foliar Insect Herbivory in Ambient and Elevated Co2

The rising level of atmospheric CO2 has stimulated several recent studies attempting to predict the effects of increased CO2 on ecological communities. However, most of these studies have been conducted in the benign conditions of the laboratory and in the absence of herbivores. In the current study, we utilized large octagonal chambers, which enclosed portions of an intact scrub-oak community to investigate the interactive effects of CO2 and insect herbivory on myrtle oak, Quercus myrtifolia. Specifically, we assessed the effects of ambient and elevated CO2 (2x current concentrations) on percent foliar nitrogen, C:N ratio, total relative foliar tannin content, and the presence of leaf damage caused by leaf mining and leaf chewing insects that feed on myrtle oak. Total foliar N declined and C:N ratios increased significantly in oaks in elevated CO2 chambers. The percentages of leaves damaged by either leafminers or leaf chewers tended to be lower in elevated compared to ambient chambers, but they co-occurred on leaves less than expected, regardless of CO2 treatment. Leaves that had been either mined or chewed exhibited a similar wounding or defensive response; they had an average of 25 and 21% higher protein binding ability, which is correlated with tannin concentration, compared to nondamaged control leaves, respectively. While the protein-binding ability (expressed as total percent tannin) of leaves from elevated CO2 was slightly higher than from leaves grown in ambient chambers, this difference was not significant.     

白栎淀粉的特性

采用X射线衍射仪、粒度仪、差示扫描量热仪(DSC)、分光光度计、质构仪等对白栎淀粉的结构及性质进行研究,并与玉米淀粉进行比较。结果表明:白栎淀粉颗粒粒径较小,平均粒径为3.15μm,结晶结构属A型,直链淀粉含量18.90%,糊化温度为72.3～84.7℃;白栎淀粉溶解性和膨润力高于玉米淀粉;白栎淀粉糊具有透明度低、凝沉性大、冻融稳定性差、黏度小、酶解率较高的特点;质构分析表明白栎淀粉糊凝胶强度较大,质地和口感较好。     

An evaluation of extracts of five traditional medicinal plants from Iran on the inhibition of mushroom tyrosinase activity and scavenging of free radicals

This study aimed to evaluate the free radical scavenging and inhibition properties of five medicinal plants, including Quercus infectoria Olive., Terminalia chebula Retz. , Lavendula stoechas L., Mentha longifolia L., Rheum palmatum L., toward the activity of mushroom tyrosinase using l -tyrosine and l -3,4-dihydroxyphenylalanine ( l -DOPA) as the substrate. The methanol extracts of Q. infectoria and T. chebula showed strong radical scavenging effect in 2,2'-dipheny l -1-picrylhydrazyl (DPPH) assay (IC₅₀ = 15.3 and 82.2 μg mL⁻¹ respectively). These plants also showed inhibitory effects against the activity of mushroom tyrosinase in hydroxylation of l -tyrosine (85.9% and 82.2% inhibition, respectively). These two plants also inhibited the oxidation of l -DOPA similar to kojic acid as positive control (IC₅₀ = 102.8 and 192.6 μg mL⁻¹ respectively). In general Q. infectoria and T. chebula significantly inhibited tyrosinase activity and DPPH radical. Both activities were concentration-dependant but not in linear manner. It is needed to study the cytotoxicity of these plant extracts in pigment cell culture before further evaluation and moving to in vivo conditions.     

Analysis of phenolic compounds in cork from Quercus suber L. by HPLC–DAD/ESI–MS

The aim of the present work was to identify the extractable phenolic compounds present in cork from Quercus suber L. The structures of thirty three compounds were tentatively identified by liquid chromatography coupled to electrospray ionisation mass spectrometry (HPLC–DAD/ESI–MS). The majority of those compounds were gallic acid derivatives, in the form of either galloyl esters of glucose (gallotannins), combinations of galloyl and hexahydroxydiphenoyl esters of glucose (ellagitannins), dehydrated tergallic-C-glucosides or ellagic acid derivatives. Others were found to correspond to low molecular weight phenolic compounds, like acids and aldehydes. Mongolicain, a flavanoellagitannin in which hydrolysable tannin and flavan-3-ol moieties are connected through a carbon–carbon linkage, was also detected in cork from Q. suber L. The results illustrate the rich array of phenolic compounds present in cork.     

Effects of Elevated CO<Subscript>2</Subscript> and Herbivore Damage on Litter Quality in a Scrub Oak Ecosystem

Atmospheric CO₂ concentrations have increased dramatically over the last century and continuing increases are expected to have significant, though currently unpredictable, effects on ecosystems. One important process that may be affected by elevated CO₂ is leaf litter decomposition. We investigated the interactions among atmospheric CO₂, herbivory, and litter quality within a scrub oak community at the Kennedy Space Center, Florida. Leaf litter chemistry in 16 plots of open-top chambers was followed for 3 years; eight were exposed to ambient levels of CO₂, and eight were exposed to elevated levels of CO₂ (ambient + 350 ppmV). We focused on three dominant oak species, Quercus geminata, Quercus myrtifolia, and Quercus chapmanii. Condensed tannin concentrations in oak leaf litter were higher under elevated CO₂. Litter chemistry differed among all plant species except for condensed tannins. Phenolic concentrations were lower, whereas lignin concentrations and lignin/nitrogen ratios were higher in herbivore-damaged litter independent of CO₂ concentration. However, changes in litter chemistry from year to year were far larger than effects of CO₂ or insect damage, suggesting that these may have only minor effects on litter decomposition.     

蒙古栎橡子-小麦混粉的流变学特性

将蒙古栎橡子粉与小麦粉按不同的比例混合,利用布拉本德粉质仪与拉伸仪测定蒙古栎橡子-小麦混粉面团的流变学特性,并对混粉中的理化指标与混粉面团流变学参数之间进行相关性分析,探讨蒙古栎橡子粉对小麦粉品质的影响。结果表明：随着橡子粉含量增加,混粉的吸水率呈先减小后增大的趋势,面团的形成时间与稳定时间缩短,弱化度提高;所有样品的拉伸阻力与拉伸比例随醒发时间的增长而增大,而混粉面团的延伸度与能量均呈下降趋势;在相同的醒发时间下,拉伸参数随橡子粉添加比例的增加呈先增大后减小的趋势。与混粉面团流变学特性呈高度正相关的理化指标是混粉面团湿面筋及蛋白质的含量。提示不同比例的蒙古栎橡子粉可以显著影响面团的流变学特性。