Latitudinal Range Variation of Trees in the United States: A Reanalysis of the Applicability of Rapoport's Rule*     

Chad S. Lane 《The Professional geographer》2007,59(1):115-130

In 1975 E. H. Rapoport described a pattern of increasing latitudinal range sizes for organisms with increasing latitude, a pattern that is now known as Rapoport's rule. The universal applicability of Rapoport's rule has been long contested, making it one of the more controversial biogeographic “rules.” This study aims to reassess the applicability of Rapoport's rule to U.S. tree species. Data presented here suggest that Rapoport's rule does indeed apply to most tree taxa within the United States, but may be taxon specific. In addition, data presented here suggest that tree range patterns consistent with Rapoport's rule in the United States are not restricted to high latitudes and are not the result of a “boundedness effect” but may be intimately linked with the glacial history and physical geography of North America. The analyses conducted here are intended to emphasize the utility of such biogeographic rules even if they are not universally applicable and should, in turn, only be considered biogeographic patterns.  相似文献   

Device for finely resolved sampling of littoral lake regions: Design and operation     

Chad P. Gubala  Charles T. Driscoll  Robert M. Newton  Carl Schofield 《水文研究》1993,7(1):99-104

Although littoral regions in northern lakes may sustain fish spawning grounds, little is known of the temporal or spatial aspects of their thermal and chemical regimes. This shortcoming is due in part to the difficulty in properly sampling these regions throughout the year with adequate spatial resolution. This problem is especially critical in lakes affected by episodic acidification during the spring snowmelt, a period of substantial importance to fisheries recruitment. A device was constructed to alleviate the problems associated with conventional water quality sampling of littoral regions. Constructed of thick walled polyvinyl chloride and permanently installed in the nearshore regions of an Adirondack lake, the episodic event sampler (EES) provided finely resolved (0.25 m) temperature and water chemistry data during the spring snowmelt period (February to May) of 1989. Although the construction and installation of the sampler represented a significant investment in labour and materials, this was offset by the high quality of the data collected. As the samplers were relatively undamaged by freeze-thaw activity, it is expected that they will continue to provide excellent information for several years.  相似文献   

Integrated measurements of acoustical and optical thin layers II: Horizontal length scales     

Mark A. Moline  Kelly J. Benoit-Bird  Ian C. Robbins  Maddie Schroth-Miller  Chad M. Waluk  Brian Zelenke 《Continental Shelf Research》2010,30(1):29-38

The degree of layered organization of planktonic organisms in coastal systems impacts trophic interactions, the vertical availability of nutrients, and many biological rate processes. While there is reasonable characterization of the vertical structure of these phenomena, the extent and horizontal length scale of variation has rarely been addressed. Here we extend the examination of the vertical scale in the first paper of the series to the horizontal scale with combined shipboard acoustic measurements and bio-optic measurements taken on an autonomous underwater vehicle. Measurements were made in Monterey Bay, CA from 2002 to 2008 for the bio-optical parameters and during 2006 for acoustic scattering measurements. The combined data set was used to evaluate the horizontal decorrelation length scales of the bio-optical and acoustic scattering layers themselves. Because biological layers are often decoupled from the physical structure of the water column, assessment of the variance within identified layers was appropriate. This differs from other studies in that physical parameters were not used as a basis for the layer definition. There was a significant diel pattern to the decorrelation length scale for acoustic layers with the more abundant nighttime layers showing less horizontal variability despite their smaller horizontal extent. A significant decrease in the decorrelation length scale was found in bio-optical parameters over six years of study, coinciding with a documented shift in the plankton community. Results highlight the importance of considering plankton behavior and time of day with respect to scale when studying layers, and the challenges of sampling these phenomena.  相似文献   

Possible impacts of climate change on extreme weather events at local scale in south–central Canada     

Chad Shouquan Cheng  Heather Auld  Qian Li  Guilong Li 《Climatic change》2012,112(3-4):963-979

Synoptic weather typing and regression-based downscaling approaches have become popular in evaluating the impacts of climate change on a variety of environmental problems, particularly those involving extreme impacts. One of the reasons for the popularity of these approaches is their ability to categorize a complex set of meteorological variables into a coherent index, facilitating the projection of changes in frequency and intensity of future daily extreme weather events and/or their impacts. This paper illustrated the capability of the synoptic weather typing and regression methods to analyze climatic change impacts on a number of extreme weather events and environmental problems for south–central Canada, such as freezing rain, heavy rainfall, high-/low-streamflow events, air pollution, and human health. These statistical approaches are helpful in analyzing extreme events and projecting their impacts into the future through three major steps or analysis procedures: (1) historical simulation modeling to identify extreme weather events or their impacts, (2) statistical downscaling to provide station-scale future hourly/daily climate data, and (3) projecting changes in the frequency and intensity of future extreme weather events and their impacts under a changing climate. To realize these steps, it is first necessary to conceptualize the modeling of the meteorology, hydrology and impacts model variables of significance and to apply a number of linear/nonlinear regression techniques. Because the climate/weather validation process is critical, a formal model result verification process has been built into each of these three steps. With carefully chosen physically consistent and relevant variables, the results of the verification, based on historical observations of the outcome variables simulated by the models, show a very good agreement in all applications and extremes tested to date. Overall, the modeled results from climate change studies indicate that the frequency and intensity of future extreme weather events and their impacts are generally projected to significantly increase late this century over south–central Canada under a changing climate. The implications of these increases need be taken into consideration and integrated into policies and planning for adaptation strategies, including measures to incorporate climate change into engineering infrastructure design standards and disaster risk reduction measures. This paper briefly summarized these climate change research projects, focusing on the modeling methodologies and results, and attempted to use plain language to make the results more accessible and interesting to the broader informed audience. These research projects have been used to support decision-makers in south–central Canada when dealing with future extreme weather events under climate change.  相似文献   

Management of exogenous threats to Antarctica and the sub-Antarctic Islands: balancing risks from TBT and non-indigenous marine organisms     

Lewis PN  Riddle MJ  Hewitt CL 《Marine pollution bulletin》2004,49(11-12):999-1005

The discovery of high levels of tributyltin compounds in Antarctic marine sediments has prompted managers to consider the banning of such substances in this region. We propose that the banning of antifouling coatings may result in an increase in the risk of non-indigenous species invasions. Our studies show that un-treated vessels carry a more diverse community of fouling organisms than treated hulls on which fouling is restricted to specific untreated niches. Up to 40% of the species recruited to the hulls of Southern Ocean vessels are species with invasive histories. Viable fouling assemblages can survive prolonged voyages to high-latitude coastlines, yet passage through sea-ice may remove fouling communities due to mechanical abrasion reducing the hazard of introductions to ice-bound coastlines. The banning of antifouling compounds may be of particular concern for the ice-free sub-Antarctic islands which represent a common anchorage point for vessels on-route to Antarctica.  相似文献   

Diatom assemblage response to Iroquoian and Euro-Canadian eutrophication of Crawford Lake,Ontario, Canada   总被引：2，自引：0，他引：2  

Erik J. Ekdahl  Jane L. Teranes  Chad A. Wittkop  Eugene F. Stoermer  Euan D. Reavie  John P. Smol 《Journal of Paleolimnology》2007,37(2):233-246

Diatom and geochemical data from Crawford Lake, Ontario, have been used to document limnological responses to periods of cultural disturbance resulting from native Iroquoian occupation of the watershed (1268–1486 AD) and Euro-Canadian agriculture and deforestation (1867 AD–present). Here, we further develop the high-resolution nature of the Crawford Lake sediment record to examine the physical, chemical and biological aspects of limnological response to human disturbances in the lake catchment area with exceptional detail. We report detailed diatom abundance and flux data for individual taxa from Crawford Lake, and further describe the relationship between assemblage composition and environmental conditions using canonical correspondence analysis (CCA). Diatom assemblage data are used to calculate diatom inferred-total phosphorus (DI-TP) concentrations for the past ∼1,000 years. We also examine the diatom community response during and after periods of disturbance by Iroquoian and Euro-Canadian populations, and compare this response to existing geochemical proxies of lake production and new elemental geochemical indicators of catchment area erosion. In particular, we explore the differing limnological response to the two distinct periods of cultural eutrophication and examine the limnological processes that occurred during the period of␣low (or no) human activity (1487–1866 AD), when geochemical indicators of lake production recovered to pre-disturbance conditions, but diatom assemblages notably did not. Our results illustrate the highly susceptible nature of diatom communities to periods of anthropogenic disturbance, and emphasize that ecological indicators (such as diatom assemblages) should be included with other proxies (such as nutrient concentrations and physical characteristics) when assessing disturbance and recovery in lake systems.  相似文献   

Placing the “Analyst” in Discourse Analysis: Iteration,Emergence and Dialogicality as Situated Process     

Chad N. Steacy  Brian S. Williams  Christian L. Pettersen  Hilda E. Kurtz 《The Professional geographer》2016,68(1):166-173

Discourse analysis is a powerful and versatile methodological tool, informing a diverse body of critical geographic scholarship. Too often, however, discourse analysis remains unexplored, operating as a “black box,” underelaborated and hence undertheorized as to just what it offers. In this article, we articulate discourse analysis as inherently processual, by which we mean both that it should be understood as a process and that it can play an integral role throughout the research process. This article is derived from a meta-analysis of an exercise that invited early-career geographers to conduct discourse analysis on commentary centered on the 2013 U.S. federal government shutdown. The reflexive research process highlights the iterative, emergent, and dialogic properties of a processual engagement with a text. We suggest that recognizing these qualities enriches the role of both the analysis and the analyst(s) and expands the valence of discourse analysis as a productive and versatile component of critical human geography.  相似文献   

Corrigendum     

Chad W. Higgins  Marc B. Parlange  C. Meneveau 《Boundary-Layer Meteorology》2004,110(3):479-479

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Acoustic observations of the swimming behavior of the euphausiid Euphausia pacifica Hansen     

De Robertis  Alex; Schell  Chad; Jaffe  Jules S 《ICES Journal of Marine Science》2003,60(4):885-898

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Trawl hangs, baby fish, and closed areas: a win-win scenario     

Link  Jason S; Demarest  Chad 《ICES Journal of Marine Science》2003,60(5):930-938

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