Latitudinal Variation in Leaf and Tree Traits of the Mangrove Avicennia germinans (Avicenniaceae) in the Central Region of the Gulf of Mexico

The variation in leaf mass per area, leaf nutrients (% carbon, nitrogen and phosphorus), and the allometric relation between tree height and diameter of the black mangrove, Avicennia germinans, were explored in nine mangrove forests in similar environments along a 5° latitudinal gradient in the central region of the Gulf of Mexico, as indicated by a southward increase in temperature and precipitation. There was no correlation between leaf nitrogen or phosphorus content and latitude. Leaf mass per area and leaf carbon content were positively correlated with latitude and negatively correlated with temperature and annual rainfall, whereas asymptotic tree height and maximum diameter showed the opposite trend. Such patterns suggest a trade-off between leaf traits and tree size which may be constrained by the same environmental factors along a dry-cold to humid-warm latitudinal gradient.     

A polysaccharide of Alloiococcus otitidis, a new pathogen of otitis media: chemical structure and synthesis of a neoglycoconjugate thereof

Alloiococcus otitidis is a recently discovered Gram-positive bacterium that has been linked with otitis media (middle ear infections). In this study, we describe the structure of a novel capsular polysaccharide (PS) expressed by the type-strain of A. otitidis, ATCC 51267, and the synthesis of a glycoconjugate composed of the capsule PS and bovine serum albumin (BSA). The capsule PS of A. otitidis type-strain was determined to be a repeating trisaccharide composed of 3-substituted N-acetyl-D-glucosamine (GlcpNAc), 6-substituted N-acetyl-D-galactosamine (GalpNAc), and 4-substituted D-glucuronic acid (GlcpA), of which the majority was amidically decorated with L-glutamic acid (Glu): {-->6)-beta-GalpNAc-(1-->4)-[Glup-->6]-beta-GlcpA-(1-->3)-beta-GlcpNAc-(1}n. Monomeric analysis performed on other A. otitidis strains revealed that similar components were variably expressed, but Glu appeared to be a regular constituent in all the strains examined. Due to the suitable presence of GlcpA and Glu, our approach for glycoconjugate synthesis employed a carbodiimide-based strategy with activation of available carboxyl groups by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), which afforded direct coupling between the capsule PS and BSA. Analysis by mass spectrometry indicated that this A. otitidis capsule PS-BSA conjugate was composed of BSA units that carried up to seven capsule PSs. This work represents the first report in the literature describing an A. otitidis cell-surface carbohydrate and the synthesis of a glycoconjugate preparation thereof. Presently, we are formulating plans to immunologically evaluate this A. otitidis glycoconjugate vaccine in animals.     

Human impact on an island ecosystem: pollen data from Sandoy, Faroe Islands

Aim To investigate the form and dynamics of ecosystems on an isolated island in the North Atlantic before human settlement in the first millennium ad , and the effects of human activities thereafter. Location The island of Sandoy, Faroes (61°50′ N, 6°45′ W). Methods Two sequences of lake sediments and one of peat were studied using pollen analysis and sedimentological techniques. Age models were constructed on the basis of radiocarbon dating and, in one case, tephrochronology. The data were analysed statistically and compared with existing data from the region. Results The pollen data indicate that early Holocene vegetation consisted of fell‐field communities probably growing on raw, skeletal soils. These communities gave way to grass‐ and sedge‐dominated communities, which in turn were largely replaced by dwarf shrub‐dominated blanket mire communities well before the first arrival of humans. There is evidence for episodic soil erosion, particularly in the uplands. Changes in the records attributable to human impact are minor in comparison with many other situations in the North Atlantic margins, and with certain published sequences from elsewhere in the Faroes. They include: (1) the appearance of cereal pollen and charcoal, (2) an expansion of ruderal taxa, (3) a decline in certain taxa, notably Juniperus communis and Filipendula ulmaria, and (4) a renewed increase in rates of upland soil erosion. The reliability of palaeoecological inferences drawn from these sites, and more generally from sites in similar unforested situations, is discussed. Main conclusions The subdued amplitude of palynological and sedimentological responses to settlement at these sites can be explained partly in terms of their location and partly in terms of the sensitivity of different parts of the ecosystem to human activities. This study is important in establishing that the imposition of people on the pristine environment of Sandoy, while far from negligible, especially in the immediate vicinity of early farms and at high altitudes, had relatively little ecological impact in many parts of the landscape.     

滇南人工种子繁殖灯台树林木生长状况研究

以不同环境条件下人工灯台树林木50cm处直径、株高、枝下高、分台数、分枝数和冠幅的实测数据为基础,用方差分析、多重比较分析和均值比较等方法研究了灯台树的生长状况。结果表明,灯台树幼林植株长势具有随年均温、最冷月温和相对湿度递增,但随海拔高度递减,呈现良好的长势。     

城市胁迫生境下二球悬铃木叶片的发育稳定度及其环境指示功能

对采自上海市区14个样点的二球悬铃木叶片发育稳定度、叶片气孔密度和气孔长径进行研究。结果表明,在3个采样时期,根据叶片宽度确定的非稳态不对称指数(FA1)和根据叶片侧脉长度确定的偏向性不对称指数(RDA1)在不同环境胁迫程度(UESL)下均表现出显著的差异,但进一步分析表明,各样点FA1与环境胁迫程度UESL之间呈显著的非线性回归关系,而RDA1与环境胁迫程度之间却未显示类似关系。此外,FA1与叶片气孔密度和气孔长径之间的显著相关关系表明,它们可共同作为指示小尺度上环境胁迫的有效指标,而RDA1是叶片的一种正常发育状态参数,并不适于反映环境胁迫状态。     

堰蜒逃逸行为的影响因子

通过野外和室内实试检测蝘蜒逃逸行为的影响因子。野外研究显示,蝘蜒可接近距离与隐蔽所间距呈显著正相关。与动物体温和基底温度无关;在开阔生境中,成体和幼体的可接近距离相似．而郁闭生境中成体的可接近距离显著大于幼体。室内试验表明。两性蝘蜒的可接近距离差异显著,繁殖期雌体的可接近距离大于雄体。     

Visualizing environmental correlates of species geographical range limits

Although many studies have treated aspects of species geographical distributions and numerous approaches exist for understanding overall ecological correlates of distributions, software tools for exploring environmental correlates of distributional limits are relatively few. We focused on the challenge of understanding spatial correlates of distributional limits, and developed an extension to arcview that provides a simple, univariate test and visualization for such explorations. The ‘Boundary U‐test’ seeks out environmental variables that show steep gradients associated with user‐defined boundaries across geography. We illustrate the tool and its applications with an example of the likely historical distribution of Mexican wolf (Canis lupus).     

The Distribution of Grazing Pressure in Relation to Vegetation Resources in Semi-arid West Africa: The Role of Herding

In semi-arid West Africa, livestock are increasingly managed by sedentary producers in close proximity to expanding cropped lands. To evaluate the agricultural and environmental implications of this trend, a study was conducted to investigate the effect of grazing management on the spatial distribution of grazing pressure, the forage provided animals during the grazing period, and local herd-forage ratios across three agropastoral landscapes characterized by varying cultivation pressure. During the 19-month study period, data on herbaceous vegetation, livestock populations, and grazing itineraries were collected. These data were referenced to land units averaging 70 ha in area. Using this approach, each of 3,819 grazing itineraries was characterized as to: 1. the sum of the products of the palatable forage mass of a particular land unit and the time spent grazing by the herd within that unit (FAT, expressed in kg-hours ha⁻¹); and 2. the average palatable herbaceous forage mass encountered by livestock across the itinerary weighted by the time spent in the land units crossed (FA, expressed in kg ha⁻¹). The spatial dispersion of livestock grazing around human settlements was found to decline with a reduction in herding labor investment (herded>herd-release>free pasture). Multiple regression analyses of itinerary data demonstrate that both FAT and FA also decline with a reduction in herding labor investment. Herded and herd-release managed livestock were offered more palatable forage and grazed areas of higher forage availability than free-pastured animals. This supports arguments that as the investment of time and effort into herding declines, feed supply to livestock will decline and the potential for grazing-induced environmental change will increase.     

马占相思树干液流特征及其与环境因子的关系

运用Granier热消散式探针法对华南丘陵退化荒坡植被恢复先锋树种马占相思(Acaciamangium)树干液流密度进行长期连续观测,并对其周围环境因子如空气温度、空气相对湿度、土壤相对湿度、光合有效辐射和总辐射进行同步观测。通过分析发现马占相思边材厚度与胸径存在显著线性相关关系;马占相思树干液流密度最大值与边材面积具显著相关关系;马占相思树干东、南、西、北4个方位测得的液流密度具显著差异,且各方位相互之间均有显著相关关系;马占相思树干液流每天到达峰值与光合有效辐射和水蒸气压亏缺到达峰值存在一定的时滞,这两个时滞与树高无关,个体间时滞差异在湿季较小,干季较大;干湿季液流平均值和最大值具显著差异,湿季蒸腾水量大于相同时间内干季蒸腾水量;液流的变化与空气温度、空气相对湿度、光合有效辐射、总辐射、水蒸气压亏缺等环境因子的变化具显著相关关系,按相关程度排序为:光合有效辐射>总辐射>水蒸气压亏缺>空气相对湿度>空气温度。     

东北老工业基地煤炭矿区环境问题与生态对策

在对我国东北老工业基地煤炭矿区环境问题进行分析的基础上,提出了解决该地区煤炭矿区环境问题的生态对策,包括着重强调煤炭矿区的生态可持续发展对于采矿工业的复兴具有重要推进作用,而澳大利亚关于最佳实践的经验对于今后采煤矿区的发展具有重要借鉴意义。推行生态多元综合治理的土地复垦一修复模式是今后煤炭矿区环境保护的方向。