991 resultados para 187-1161
Resumo:
Landscape ecology concepts developed from terrestrial systems have recently emerged as theoretical and analytical frameworks that are equally useful for evaluating the ecological consequences of spatial patterns and structural changes in the submerged landscapes of coastal ecosystems. The benefits of applying a spatially-explicit perspective to resource management and restoration planning in the coastal zone are rapidly becoming apparent. This Theme Section on the application of landscape ecology to the estuarine and coastal environment emerged from a special symposium at the Coastal and Estuarine Research Federation (CERF) 20th Biennial Conference (Estuaries and Coasts in a Changing World) held in Portland, Oregon, USA, in November 2009. The 7 contributions in this Theme Section collectively provide substantial insights into the current status and application of the landscape approach in shallow marine environments, and identify significant knowledge gaps, as well as potential directions for the future advancement of ‘seascape ecology’.
Resumo:
EXTRACT (SEE PDF FOR FULL ABSTRACT): Laminated sediments are preserved in upper Pleistocene sections of cores collected on the continental slope at water depths within the present oxygen-minimum zone from at least as far north as the Klamath River and as far south as Point Sur. Comparison of sediment components in the laminae with those delivered to sediment traps as pelagic marine "snow" show the dark/light lamination couplets are indeed annual (varves). ... The presence of carbon-, sulfur-, and metal-rich sediments, as well as lack of bioturbation, all support the theory that the oxygen-minimum zone in the northeastern Pacific Ocean was more intense - in fact, anoxic - during the late Pleistocene in response to greater coastal upwelling and higher organic productivity.
Resumo:
(一)蒙古栎红松林动态的研究 本文综述了森林动态模型的基本概念和发展历史,把模型分为生长和演替模型两类,并比较了两类模型的特点和适用条件,详细论述了演替模型的基本原理,分析了早期和最新林窗模型的特点,给出了林窗模型的最新进展,指出森林动态模型的发展趋势为:①、为满足不同用户对模型的要求,模型应向综合总体方向发展;②、随着生理生态学的发展、试验仪器及分析方法的进步,和为了进一步认识森林动态变化的机理,建立树木生长机制过程模型成为另一个必然的发展方向。 随后综合分析了广泛应用于林窗模型中作为描述树高和直径关系的数学函数,通过理论分析和实际观测数据拟合及预测精度检验,表明理查德方程和单分子方程是森林动态林窗模型中描述树高和直径关系的最佳方程。 通过对蒙古栎红松林三个年龄阶段物种和结构动态实际观测数据分析表明,该类型森林的早期阶段以蒙古栎等阳性树种占优势,中期形成红松和阔叶树占优势的混交林,后期以红松占绝对优势。对该类型森林直径分布变化的研究得出:林分发育的早期,阔叶树中大径级木较多,针叶树中小径级木多;在林分发育的后期呈相反分布。用理论概率模型拟合直径分布表明,韦布尔概率分布模型是描述蒙古栎红松林直径分布的最合适函数。 在以上研究结果的基础上,以森林动态斑块理论为基础建立了蒙古栎红松林动态变化的林窗模型FOROAK,该模型包括对树木生长的生物学过程和影响树木生长的环境因子模拟两部分。运行模型用两种不同面积大小的样地分析森林动态,确定蒙古栎红松林林窗面积为0.05ha。以实际调查数据检验模型,证明所得模型能合理预测森林变化过程,在预测树种组成上精度很高。对裸地上森林的模拟表明蒙古栎红松林动态过程复杂,蒙古栎和白桦在林分发育开始占优势后期渐被红松取代。对现实原始林预测显示,森林未来300年变化稳定,红松株数和生物量变化很小。 最后,应用建立的林窗模型研究了同龄纯林林分密度动态,模拟了林分密度、断面积、生物量、叶面积指数和生产力150年的变化,用林分密度效应的3/2法则和产量恒定法则检验模拟结果表明,模拟的林分密度发展与理论预测相符合,通过本文的研究既检验了林窗动态模型又印证了林分密度效应理论。 (二)生物多样性主题信息标准的研究 中国是世界上生物多样性最丰富的国家之一,在多年的调查、研究和保护工作中,已积累了大量的数据资料,因此,被联合国环境规划署挑选参加“发展中国家生物多样性数据管理能力建设及信息系统网络化”项目,该项目的主要内容之一就是了解与生物多样性有关领域的主题信息标准。 主题信息标准部分讨论了生物多样性信息的收集、管理和转换标准,系统而全面地概述了生物多样性有关领域应用的数据分类系统、核心数据集以及与数据获得有关的术语、定义和数据模型,并讨论了各部门在研究和促进生物多样性信息标准化方面的成果和正在开展的工作。涉及的领域有自然和人工生境中的陆地植被、农业、林业、湿地、海岸和海洋,还有保护区、物种和对生物多样性有威胁的因子等专题。 文中讲述了与陆地植被分类有关的土地利用方式和土地覆盖分类等问题,并给出了国际国内应用广泛的植被分类系统。讨论了农业中与生物多样性有直接关系的分类系统,包括土地分类系统、土壤分类系统等。从森林生态系统和土地利用、林权和林政、森林资源调查、评价和监测、森林利用和经营实践、森林环境和可持续发展等几方面讨论了这些主题的概念、术语和数量划分标准。 讨论了湿地分类系统的发展,列举了国内外应用广泛的分类系统。论述了海岸和海洋生境及保护区的分类系统和标准,给出了数据定义和模型。列举了国内外广泛应用的物种命名标准和其发展过程。分遗传多样性、物种多样性和生态系统多样性三个层次讨论了它们受威胁的特点和评价现状,最后分别不同的威胁因子,如:生境丧失和片断化、全球气候变化、酸雨、臭氧层破坏和有毒污染物讨论了它们对生物多样性的威胁特点和评价现状。
Resumo:
As the global population has increased, so have human influences on the global environment. ... How can we better understand and predict these natural and potential anthropogenic variations? One way is to develop a model that can accurately describe all the components of the hydrologic cycle, rather than just the end result variables such as precipitation and soil moisture. If we can predict and simulate variations in evaporation and moisture convergence, as well as precipitation, then we will have greater confidence in our ability to at least model precipitation variations. Therefore, we describe here just how well we can model relevant aspects of the global hydrologic cycle. In particular, we determine how well we can model the annual and seasonal mean global precipitation, evaporation, and atmospheric water vapor transport.
Resumo:
A discussion is presented on the applications of remote sensing to fisheries. The measurement of temperature, wind stress, and ocean colour using remote sensing techniques is considered.
Resumo:
Caulerpa racemosa var. macrophysa, C. racemosa var cornyphora and C. scalpelliformis are analyzed by quantitative paper chromatographic technique for their amino acid contents in proteins, peptides and free state. It is found that no appreciable variation occurs in the quality of amino acid make up in these algae; but quantitative differences are apparent in them. Moreover, both qualitative and quantitative variations occur in the amino acid make up of the peptides, and in the free state. The results are compared with those of the other investigations.