Homogenization Applied to Integrate Across Spatial and Temporal Scales in Forest/Insect Ecology

POWELL 0077663在一个当前感兴趣的生态问题中，存在着应用和测试同质化的所有要素，以解决规模问题并模拟气候和人类对暴发昆虫物种的影响。这位研究人员和他的同事建立了山松甲虫(Dendroctonus Boderosae)对松树寄主的扩散和大规模攻击的确定性空间模型。该模型在公顷空间尺度和天数时间尺度上得到了验证和描述。在这个项目中，他们利用MPB/宿主系统上的同质化技术构建了一个森林规模(100公顷/年)模型，反映了当前昆虫发育、扩散和对气候反应的小规模时空模型的大范围紧急后果。在如此大的尺度上进行直接计算将是令人望而却步的；大多数生态模拟都面临着类似的困难，涉及现实尺度上的时空异质性和生命-系统/扩散的相互作用。研究人员开发同质化程序，使这种类型的生态模拟通常易于处理，并在MPB/主机系统中实施和测试这些程序。均化过程产生一个积分-差分方程式(IDE)，在景观尺度上以长达一年的时钟“滴答”运行。在验证阶段，使用IDE模型对景观进行分类；通过与航空影像的比较，对错误分类进行统计分析，使模拟方法具有自我校正的能力；最后，使用情景研究来检验假设的气候和管理轨迹对寄主/昆虫动态的影响。这说明了同质化方法在生态背景下的力量，并提供了必要的例子，使生物和环境研究人员能够获得这些技术。均匀化方法是一种数学技术，它允许从确定性的小尺度模型中推导出大尺度的性质。就我们所知，同质化的方法从未被应用于生态问题，在那里，规模问题是许多辩论的焦点。一种可能的攻角是联合使用模型和模拟，然后用空间上明确的数据进行验证。由于时空尺度的相互作用，完全描述空间异质性和气候变化的生态问题的直接计算方法是极其困难的。一方面，由于缺乏任何生态尺度上有效的、确定性的空间模型，另一方面，扩展空间观测的困难，加剧了这一困难。在这个项目中，研究人员和他的同事们将同质化技术应用于山松甲虫/罗奇松生态系统，以解决规模问题，并模拟气候和人类对昆虫物种种群爆发的影响。

Powell0077663 In one ecological problem of current interest all theelements exist for application and testing of homogenization toresolve the scale issue and simulate climate and human impacts onoutbreak insect species. The investigator and his colleagues havedeveloped a deterministic spatial model of Mountain Pine Beetle(MPB, Dendroctonus ponderosae) dispersal and mass-attack of pinehosts. The model is validated and descriptive on spatial scalesof hectares and time scales of days. In this project they usetechniques of homogenization on the MPB/host system to constructa forest scale ( 100 hectare/years) model reflecting thelarge-scale emergent consequences of current small-scale spatialand temporal models of insect development, dispersal, andresponse to climate. Direct computation on such large scaleswould be prohibitive; similar difficulties face most ecologicalsimulations involving spatio-temporal heterogeneity at realisticscales and life-system/dispersal interactions. The investigatorsdevelop homogenization procedures that make this type ofecological simulation generally tractable, and implement and testthese procedures in the MPB/host system. The homogenizationprocedure generates an integro-difference equation (IDE),operating with year-long clock `ticks' on landscape scales. In avalidation phase, the IDE model is used to classify landscapes.Statistically analyzing misclassifications in comparison toaerial imagery makes the simulation methodology self-correcting.Finally, scenario studies are used to examine consequences ofhypothetical climate and management trajectories on host/insectdynamics. This illustrates the power of homogenizationapproaches in an ecological context, and provides needed examplesto make these techniques accessible to biological andenvironmental researchers. The method of homogenization is a mathematical techniquethat allows deduction of large-scale properties fromdeterministic small-scale models. To the best of our knowledgethe method of homogenization has never been applied to ecologicalproblems, where issues of scale are the focus of much debate. Onepossible angle of attack is joint use of models and simulation,followed by validation with spatially explicit data. Directcomputational approaches to ecological problems with fulldescription of spatial heterogeneity and climatic variation areextremely difficult due to interaction of scales in time andspace. The difficulty is exacerbated on the one hand by thepaucity of validated, deterministic spatial models at anyecological scale, and by the difficulty of extended spatialobservations on the other. In this project the investigators andhis colleagues apply the technique of homogenization to theMountain Pine Beetle/Lodgepole Pine ecosystem to resolve thescale issue and simulate climate and human impacts on populationoutbreaks of insect species.