997 resultados para 311-U1326D


Relevância:

10.00% 10.00%

Publicador:

Resumo:

Digital maps of the coral reef ecosystem (<~30m deep) of Majuro Atoll, Republic of the Marshall Islands, were created through visual interpretation of remote sensing imagery. Digital Globe’s Quickbird II satellite images were acquired between 2004 and 2006 and georeferenced to within 1.6 m of their true positions. Reef ecosystem features were digitized directly into a GIS at a display scale of 1:4000 using a minimum feature size of 1000 square meters. Benthic features were categorized according to a classification scheme with attributes including zone (location, such as lagoon or forereef, etc.), structure (bottom type, such as sand or patch reef, etc.) and percent hard bottom. Ground validation of habitat features was conducted at 311 sites in 2009. Resulting maps consisted of 1829 features covering 366 square kilometers. Results demonstrate that reef zones occurred in a typical progression of narrow bands from offshore, though forereef, reef flat, shoreline, land, backreef, and lagoon habitats. Lagoon was the largest zone mapped and covered nearly 80% of the atoll, although much of it was too deep to have structures identified from the satellite imagery. Dominant habitat structures by area were pavement and aggregate reef, which covered 29% and 18% of the mapped structures, respectively. Based on the number of features, individual and aggregated patch reefs comprised over 40% of the features mapped. Products include GIS based maps, field videos and pictures, satellite imagery, PDF atlas, and this summary report. Maps and associated data can be used to support science and management activities on Majuro reef ecosystems including inventory, monitoring, conservation, and sustainable development applications.

Relevância:

10.00% 10.00%

Publicador:

Relevância:

10.00% 10.00%

Publicador:

Resumo:

本文研究了紫草科琉璃草属植物小花琉璃草Cynoglossum lanceolatum Forsk.的精油成分及各成分的百分含量,鉴定了其中的69个化合物。同时对此植物的脂溶性成分进行了分离,得到八个单体化合物,鉴定了其中的五个成分,它们分别是:十六碳酸甲酯、β—谷甾醇,5α,豆甾烷-3,6一二酮,6β—羟基—豆甾—4—烯—3—酮和胡萝卜甙。除β—谷甾醇外,其余四个成分为首次从琉璃草属植物中得到。 在精油成分中,茴香脑占整个精油成分的62%,笔者对这一精油组成的特殊性的意义进行了探讨,并讨论了茴香脑,β—谷甾醇及胡萝卜甙的药理活性。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

本文利用同工酶分析技术测定北京市东灵山区两个辽东栎(Quercus Liaotungensis Koidz)群体的遗传结构。共分析统计了13个酶系统的30位点。结果表明:辽东栎群体具有较高的遗传变异水平,两个小群体的平均多态位点百分率达86. 6%,等位基因平均数为2.25,平均期望杂合度为0.311。固定指数为负值(-0.138)表明群体中杂合体过量。小群体间的分化程度不高,两个小群体间的遗传距离为0.037。同工酶测定的总变异中,5.8%来自小群体间,其余(94.2%)来自小群体内。和具有相似生活特征的其它种类乔木相比,每代迁移率估计值(4.20)偏低。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In March 2006, a dead, male bottlenose dolphin (Tursiops truncatus) was found in the salt marsh in Charleston, South Carolina, United States. During necropsy, an enterolith was found completely obstructing the intestinal lumen. Further examination of the enterolith revealed a stingray spine nidus. Most terrestrial enteroliths are composed primarily of struvite (magnesium ammonium phosphate); however, the majority of the enterolith discovered in the stranded dolphin was composed of calcium phosphate carbonate. This case provides an interesting comparison of the variation in the mineral composition between terrestrial and marine enteroliths.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

An intensive commercial hook-and-line fishing operation targeted the demersal fisheries resources at Saya de Malha Bank in the Southwest Indian Ocean. Fishing was conducted with 12 dories that were equipped with echo sounders and electric fishing reels and supported by a refrigerated mothership. Over a 13-day period in the 55–130 m depth range, a total of 74.3 metric tons (t) of fish were caught, of which the crimson jobfish (Pristipomoides filamentosus) represented 80%. Catch rates decreased with time and could not be attributed to changes in location, climatic conditions, fishing depth, fishing method, or bait type. The initial virgin biomass of P. filamentosus available to a line fishery at the North Western promontory of Saya de Malha Bank was estimated at 72.6 t through application of the Leslie model to daily catch and effort data. Biomass densities of 2364 kg/km2 and 1206 kg/km were obtained by applying the initial biomass estimates to the surface area and to the length of the dropoff that was fished. The potential sustainable yield prior to exploitation was estimated at 567 kg/km2 per year. The quantity of P. filamentosus caught by the mother-ship-dory fishing operation represented 82% of the initial biomass available to a hook-and-line fishery, equivalent to more that three times the estimated maximum sustainable yield. The results of the study are important to fisheries managers because they demonstrate that intensive line fishing operations have the potential to rapidly deplete demersal fisheries resources.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

锡林郭勒草原是欧亚大陆草原区亚洲东部草原亚区保存比较完整的原生草原部分。区内生态环境类型独特,具有草原生物群落的基本特征,并能全面反映内蒙古高原典型草原生态系统的结构和生态过程。本区拥有目前我国最大的草原与草甸生态系统类型的自然保护区,在草原生物多样性的保护方面占有重要的位置和明显的国际影响。目前,草地退化导致的区域生态问题越来越突出,评价我国草地资源生态服务功能的经济价值,对于制定合理的区域生态保护和经济开发决策、保护和恢复草地生态系统具有重要意义。 针对锡林郭勒草原生态系统服务价值的评估,根据不同的退化强度对锡林郭勒草原植被类型进行定量模拟将其分为正常草地和退化草地,根据退化等级标准划分,将其分为严重退化、中度退化和轻度退化,以锡林郭勒草原有机物生产为基础,分别采用市场价值法、替代市场法和假想市场法等,估算其主要服务功能的经济价值。 本研究选取草地生态系统服务功能价值的功能指标包括食物和原材料生产、旅游和娱乐、有机物质生产、气体调节价值、水土保持、涵养水源价值、以及生物控制及其生物多样性等8类功能进行了评价,基于服务功能机制对其价值量评价方法进行了探索.并在此基础上对其生态经济价值进行了评价,得出锡林郭勒草地生态系统8类服务功能的年生态经济价值分别为元,3.4×108元、6.7×108元、15.8×108元、122.24×108元、3.9×108元107.64×108元、16×108元、36.01×108元,8类功能的总价值为311.69×108。 研究结果表明,草地生态系统除为社会提供直接产品价值外.还具有巨大的间接使用价值,而且这种价值对人类的贡献与提供产品本身同样重要。在各种服务功能中,水土保持价值最为重要;因此,加强草原生态系统环境建设对于维持区域生态安全具有重要意义。今后草地生态系统服务功能及其价值评价工作应注重加强草地生态系统服务功能机制研究。

Relevância:

10.00% 10.00%

Publicador:

Relevância:

10.00% 10.00%

Publicador:

Resumo:

CO2浓度升高和气候变暖已成为不可逆转的现实,而具有强氧化性的臭氧浓度升高也被认为是全球变化的重要组成部分,已经或将对植被生长产生严重威胁。冬小麦(Triticum aestivum L.)生长发育期内受到环境变化的影响相对较大。小麦是对臭氧最为敏感的作物之一,华北地区冬小麦灌浆期容易发生臭氧污染。本研究以冬小麦为试材,研究了CO2浓度加倍和2oC增温对中国北方不同年代推出的冬小麦品种幼苗生长的效应;研究了不同小麦品种对花后短期臭氧胁迫的反应;分别研究了干旱、增温与臭氧污染对冬小麦旗叶光合和产量的交互影响。研究结果如下: 1) CO2浓度加倍和温度升高加快冬小麦幼苗的生长速率。CO2浓度加倍主要是促进了幼苗的分蘖(+1.54分蘖),而增温加快了发育进程(主茎叶片数比对照多1叶)。不同品种对CO2浓度加倍和增温的响应存在着差异,但与育种年代没有显著相关关系。从20个品种的总体情况来看,CO2浓度加倍和2.0℃增温对冬小麦幼苗的生长具有叠加效应。生长较慢的冬小麦品种对CO2浓度加倍的反应越大。 2) CO2浓度加倍显著提高了小麦新展开叶的净光合速率(Psat),显著降低了气孔导度(gs)和蒸腾速率(E),从而显著提高了瞬时水分利用效率(ITE),但不同小麦品种对CO2浓度加倍的反应与其育种年代没有明显的相关性;增温对冬小麦叶片Psat的效应不显著,但显著降低了gs,而E显著增大,从而导致ITE显著降低,其中,Psat对增温的反应与品种育种年代呈显著正相关(R=0.525, p<0.05),并与叶片比叶面积(SLA)显著正相关(R=0.45, p<0.001)。CO2浓度加倍和增温同时处理时对Psat、gs和ITE的效应显著大于CO2浓度加倍处理。 3) 冬小麦灌浆初期,短时间的臭氧胁迫对旗叶的同化能力带来了显著的负效应,而且光合性能最大的叶片中部受到的抑制最为严重。同化能力的下降导致最终产量的降低。然而,不同品种对臭氧的敏感性存在着很大差异。臭氧对具有较高收获指数和产量的当代品种-烟农19的效应(-19%,p<0.01)明显大于产量较低的老品种-农大311(-8%,p<0.05),主要表现在叶片可见伤害程度较大,旗叶净光合速率受到的负效应较大,籽粒重量以及穗粒数均显著降低。 4) 短期高浓度臭氧胁迫对处于中度干旱胁迫下的小麦植株产生了可见伤害(<20%),但伤害程度明显低于处于土壤含水量较高的植株(>30%)。短期臭氧处理显著降低了处于较高土壤含水量下的小麦旗叶Psat(-36%),干旱胁迫也显著降低了旗叶Psat(-34%),但臭氧仅使处于中度干旱胁迫下的植株旗叶Psat进一步降低了7.8%。gs的变化趋势与Psat的变化基本一致。臭氧处理结束并复水后,干旱处理植株的Psat与对照基本相同,而臭氧处理过的植株均明显低于对照,其中臭氧处理期间处于良好土壤含水量条件下的植株旗叶Psat显著低于对照,并且随着植株的衰老,其下降的速度明显快于其它处理,表明衰老速度加快。而中度干旱胁迫可减轻臭氧对小麦产量的危害程度。 5) 正常供水条件下,短期臭氧处理结束2天后,小麦旗叶Psat与对照植株的值接近,然而随着时间的延长,Psat下降的速度明显快于对照。臭氧处理结束后,植株若遭受干旱胁迫,旗叶Psat显著低于对照。虽然gs的变化趋势与Psat基本一致,但臭氧处理后光合的降低主要是由非气孔限制因素引起的。旗叶光合能力下降、叶片提前衰老,是臭氧处理导致产量显著降低的主要原因。穗粒数没有显著变化,而千粒重却显著降低。而臭氧处理后若遇干旱胁迫,旗叶的光合能力以及光合有效期进一步减少,导致不育小花数增多,因此籽粒产量进一步减少。 6) 灌浆期臭氧浓度升高显著降低了小麦叶片的光合能力,导致产量显著降低;2oC升温加快了植株的衰老,然而并没有对产量性状产生显著效应;温度和臭氧两因子对旗叶的气体交换参数具有交互效应,但对各产量性状均没有交互效应发生。 综合以上研究结果,不同品种对环境变化的响应存在着显著差异,意味着可以通过育种途径来减轻未来环境变化对农业生产的负面影响;灌浆期臭氧胁迫显著降低冬小麦的产量,环境因子可影响臭氧胁迫效应,但之间的交互作用比较复杂,有待进一步深入研究,以保证未来全球变化环境下的粮食安全。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

以我国主要经济海产品中国对虾( Penus chinensis ) 为研究对象, 通过Sephadex G250 、RP2HPLC 等 技术分离纯化到PC2 Ⅲ系列中国对虾天然抗菌肽。经初步鉴定, 该系列抗菌肽对革兰氏阴性和革兰氏阳性菌都 表现出程度不一的抑菌活性, 且不同程度地影响小白鼠离体回肠肌收缩, 但无丝氨酸蛋白酶抑制剂活性。用 MALDI2TOF 质谱对样品进行分析, 检测到分子量分别为1 071 Da 和1 311 Da 的两种抗菌肽。这些抗菌肽对对虾 抵御微生物的侵袭具有重要的作用