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Oceanography and Atmospheric Sciences and Meteorology

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College of Arts and Sciences Faculty Publications

2011

Articles 1 - 6 of 6

Full-Text Articles in Physical Sciences and Mathematics

Randomization Tests For Quantifying Species Importance To Ecosystem Function, Nicholas J. Gotelli, Werner Ulrich, Fernando T. Maestre Dec 2011

Randomization Tests For Quantifying Species Importance To Ecosystem Function, Nicholas J. Gotelli, Werner Ulrich, Fernando T. Maestre

College of Arts and Sciences Faculty Publications

1. Quantifying the contribution of different species to ecosystem function is an important challenge. We introduce simple randomization tests (and software) for quantifying the average effect of species on ecosystem variables measured in multiple plots with and without the presence of a particular species. These randomization tests formalize the analysis of uncontrolled 'natural experiments' and quantify species effects in standardized deviation units. 2.We tested the method with data on ecosystem function in biological soil crust assemblages of lichens in semi-arid gypsum outcrops in central Spain. In sixty-three 50cm×50cm sample plots, we measured the presence and percentage cover of 17 species …

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Heating Up The Forest: Open-Top Chamber Warming Manipulation Of Arthropod Communities At Harvard And Duke Forests, Shannon L. Pelini, Francis P. Bowles, Aaron M. Ellison, Nicholas J. Gotelli, Nathan J. Sanders, Robert R. Dunn Oct 2011

Heating Up The Forest: Open-Top Chamber Warming Manipulation Of Arthropod Communities At Harvard And Duke Forests, Shannon L. Pelini, Francis P. Bowles, Aaron M. Ellison, Nicholas J. Gotelli, Nathan J. Sanders, Robert R. Dunn

College of Arts and Sciences Faculty Publications

1.Recent observations indicate that climatic change is altering biodiversity, and models suggest that the consequences of climate change will differ across latitude. However, long-term experimental field manipulations that directly test the predictions about organisms' responses to climate change across latitude are lacking. Such experiments could provide a more mechanistic understanding of the consequences of climate change on ecological communities and subsequent changes in ecosystem processes, facilitating better predictions of the effects of future climate change. 2.This field experiment uses octagonal, 5-m-diameter (c.22m 3) open-top chambers to simulate warming at northern (Harvard Forest, Massachusetts) and southern (Duke Forest, North Carolina) hardwood …

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Understanding Earth's Eroding Surface With 10Be, Eric W. Portenga, Paul R. Bierman Aug 2011

Understanding Earth's Eroding Surface With 10Be, Eric W. Portenga, Paul R. Bierman

College of Arts and Sciences Faculty Publications

For more than a century, geologists have sought to measure the distribution of erosion rates on Earth's dynamic surface. Since the mid-1980s, measurements of in situ 10Be, a cosmogenic radionuclide, have been used to estimate outcrop and basin-scale erosion rates at 87 sites around the world. Here, we compile, normalize, and compare published 10Be erosion rate data (n = 1599) in order to understand how, on a globalscale, geologic erosion rates integrated over 103 to 106 years varybetween climate zones, tectonic settings, and different rock types. Drainage basins erodemore quickly (mean = 218 m Myr-1; median = 54 m Myr-1) …

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The Effects Of Climate Change On Density-Dependent Population Dynamics Of Aquatic Invertebrates, Edmund M. Hart, Nicholas J. Gotelli Aug 2011

The Effects Of Climate Change On Density-Dependent Population Dynamics Of Aquatic Invertebrates, Edmund M. Hart, Nicholas J. Gotelli

College of Arts and Sciences Faculty Publications

Global climate change has the potential to alter aquatic communities through changes in evapotranspiration and increased variability in precipitation. We used aquatic mesocosms to test the impacts of variable precipitation on population dynamics of commonn mosquito (Culicidae) and midge (Chironomidae) larvae that inhabit vernal pools. In a mixed deciduous forest in northern Vermont, USA, we orthogonally crossed seven levels of mean water level (increased rainfall) with seven levels of water level coefficient of variation (more variable rainfall) to simulate a broad array of climate change scenarios in 49 experimental mesocosms. The average abundance of Culicidae was highest at low water …

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Effects Of Short-Term Warming On Low And High Latitude Forest Ant Communities, Shannon L. Pelini, Mark Boudreau, Neil Mccoy, Aaron M. Ellison, Nicholas J. Gotelli, Nathan J. Sanders, Robert R. Dunn May 2011

Effects Of Short-Term Warming On Low And High Latitude Forest Ant Communities, Shannon L. Pelini, Mark Boudreau, Neil Mccoy, Aaron M. Ellison, Nicholas J. Gotelli, Nathan J. Sanders, Robert R. Dunn

College of Arts and Sciences Faculty Publications

Climatic change is expected to have differential effects on ecological communities in different geographic areas. However, few studies have experimentally demonstrated the effects of warming on communities simultaneously at different locales. We manipulated air temperature with in situ passive warming and cooling chambers and quantified effects of temperature on ant abundance, diversity, and foraging activities (predation, scavenging, seed dispersal, nectivory, granivory) in two deciduous forests at 35° and 43° N latitude in the eastern U.S. In the southern site, the most abundant species, Crematogaster lineolata, increased while species evenness, most ant foraging activities, and abundance of several other ant species …

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Counting Ants (Hymenoptera: Formicidae): Biodiversity Sampling And Statistical Analysis For Myrmecologists, Nicholas J. Gotelli, Aaron M. Ellison, Robert R. Dunn, Nathan J. Sanders May 2011

Counting Ants (Hymenoptera: Formicidae): Biodiversity Sampling And Statistical Analysis For Myrmecologists, Nicholas J. Gotelli, Aaron M. Ellison, Robert R. Dunn, Nathan J. Sanders

College of Arts and Sciences Faculty Publications

Biodiversity sampling is labor intensive and is especially challenging for myrmecologists, because the sampling units (individual workers) do not correspond in a simple way to the natural units of diversity (individual nests). Because it is usually not possible to reach a sampling asymptote for ants, comparisons of species richness among collections have to be carefully standardized for the number of individuals and number of samples examined. Asymptotic estimators allow for extrapolation to an estimated asymptote of species richness, and rarefaction curves permit meaningful comparisons of samples by interpolating data to a standardized number of sampling units. Winkler sacks of leaf …

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