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An Analog Approach For Weather Estimation Using Climate Projections And Reanalysis Data, Patrick J. Clemins, Gabriela Bucini, Jonathan M. Winter, Brian Beckage, Erin Towler, Alan Betts, Rory Cummings, Henrique Chang Queiroz
An Analog Approach For Weather Estimation Using Climate Projections And Reanalysis Data, Patrick J. Clemins, Gabriela Bucini, Jonathan M. Winter, Brian Beckage, Erin Towler, Alan Betts, Rory Cummings, Henrique Chang Queiroz
College of Agriculture and Life Sciences Faculty Publications
General circulation models (GCMs) are essential for projecting future climate; however, despite the rapid advances in their ability to simulate the climate system at increasing spatial resolution, GCMs cannot capture the local and regional weather dynamics necessary for climate impacts assessments. Temperature and precipitation, for which dense observational records are available, can be bias corrected and downscaled, but many climate impacts models require a larger set of variables such as relative humidity, cloud cover, wind speed and direction, and solar radiation. To address this need, we develop and demonstrate an analog-based approach, which we call a ‘‘weather estimator.’’ The weather …
Bi-Dimensional Null Model Analysis Of Presence-Absence Binary Matrices, Giovanni Strona, Werner Ulrich, Nicholas J. Gotelli
Bi-Dimensional Null Model Analysis Of Presence-Absence Binary Matrices, Giovanni Strona, Werner Ulrich, Nicholas J. Gotelli
College of Arts and Sciences Faculty Publications
Ecology, published by Wiley Periodicals, Inc., on behalf of the Ecological Society of America. Comparing the structure of presence/absence (i.e., binary) matrices with those of randomized counterparts is a common practice in ecology. However, differences in the randomization procedures (null models) can affect the results of the comparisons, leading matrix structural patterns to appear either “random” or not. Subjectivity in the choice of one particular null model over another makes it often advisable to compare the results obtained using several different approaches. Yet, available algorithms to randomize binary matrices differ substantially in respect to the constraints they impose on the …
Ecological Network Metrics: Opportunities For Synthesis, Matthew K. Lau, Stuart R. Borrett, Benjamin Baiser, Nicholas J. Gotelli, Aaron M. Ellison
Ecological Network Metrics: Opportunities For Synthesis, Matthew K. Lau, Stuart R. Borrett, Benjamin Baiser, Nicholas J. Gotelli, Aaron M. Ellison
College of Arts and Sciences Faculty Publications
Network ecology provides a systems basis for approaching ecological questions, such as factors that influence biological diversity, the role of particular species or particular traits in structuring ecosystems, and long-term ecological dynamics (e.g., stability). Whereas the introduction of network theory has enabled ecologists to quantify not only the degree, but also the architecture of ecological complexity, these advances have come at the cost of introducing new challenges, including new theoretical concepts and metrics, and increased data complexity and computational intensity. Synthesizing recent developments in the network ecology literature, we point to several potential solutions to these issues: integrating network metrics …
Estimates Of Local Biodiversity Change Over Time Stand Up To Scrutiny, Mark Vellend, Maria Dornelas, Lander Baeten, Robin Beauséjour, Carissa D. Brown, Pieter De Frenne, Sarah C. Elmendorf, Nicholas J. Gotelli, Faye Moyes, Isla H. Myers-Smith, Anne E. Magurran, Brian J. Mcgill, Hideyasu Shimadzu, Caya Sievers
Estimates Of Local Biodiversity Change Over Time Stand Up To Scrutiny, Mark Vellend, Maria Dornelas, Lander Baeten, Robin Beauséjour, Carissa D. Brown, Pieter De Frenne, Sarah C. Elmendorf, Nicholas J. Gotelli, Faye Moyes, Isla H. Myers-Smith, Anne E. Magurran, Brian J. Mcgill, Hideyasu Shimadzu, Caya Sievers
College of Arts and Sciences Faculty Publications
We present new data and analyses revealing fundamental flaws in a critique of two recent meta-analyses of local-scale temporal biodiversity change. First, the conclusion that short-term time series lead to biased estimates of long-term change was based on two errors in the simulations used to support it. Second, the conclusion of negative relationships between temporal biodiversity change and study duration was entirely dependent on unrealistic model assumptions, the use of a subset of data, and inclusion of one outlier data point in one study. Third, the finding of a decline in local biodiversity, after eliminating post-disturbance studies, is not robust …
Changing Forests-Changing Streams: Riparian Forest Stand Development And Ecosystem Function In Temperate Headwaters, Dana R. Warren, William S. Keeton, Peter M. Kiffney, Matthew J. Kaylor, Heather A. Bechtold, John Magee
Changing Forests-Changing Streams: Riparian Forest Stand Development And Ecosystem Function In Temperate Headwaters, Dana R. Warren, William S. Keeton, Peter M. Kiffney, Matthew J. Kaylor, Heather A. Bechtold, John Magee
Rubenstein School of Environment and Natural Resources Faculty Publications
Light availability influences temperature, primary production, nutrient dynamics, and secondary production in aquatic ecosystems. In forested freshwater ecosystems, shading by streamside (riparian) vegetation is a dominant control on light flux and represents an important interaction at the aquatic-terrestrial interface. Changes in forest structure over time, particularly tree mortality processes that gradually increase light penetration through maturing forest canopies, are likely to influence stream light fluxes and associated ecosystem functions. We provide a set of conceptual models describing how stream light dynamics change with the development of complex canopy structure and how changes in light availability are likely to affect stream …
Ecological And Biogeographic Null Hypotheses For Comparing Rarefaction Curves, Luis Cayuela, Nicholas J. Gotelli, Robert K. Colwell
Ecological And Biogeographic Null Hypotheses For Comparing Rarefaction Curves, Luis Cayuela, Nicholas J. Gotelli, Robert K. Colwell
College of Arts and Sciences Faculty Publications
The statistical framework of rarefaction curves and asymptotic estimators allows for an effective standardization of biodiversity measures. However, most statistical analyses still consist of point comparisons of diversity estimators for a particular sampling level. We introduce new randomization methods that incorporate sampling variability encompassing the entire length of the rarefaction curve and allow for statistical comparison of i ≥ 2 individual-based, sample-based, or coverage-based rarefaction curves. These methods distinguish between two distinct null hypotheses: the ecological null hypothesis (H0eco) and the biogeographical null hypothesis (H0biog). H0eco states that the i samples were drawn from a single assemblage, and any differences …
Using Historical And Experimental Data To Reveal Warming Effects On Ant Assemblages, Julian Resasco, Shannon L. Pelini, Katharine L. Stuble, Nathan J. Sanders, Robert R. Dunn, Sarah E. Diamond, Aaron M. Ellison, Nicholas J. Gotelli, Douglas J. Levey
Using Historical And Experimental Data To Reveal Warming Effects On Ant Assemblages, Julian Resasco, Shannon L. Pelini, Katharine L. Stuble, Nathan J. Sanders, Robert R. Dunn, Sarah E. Diamond, Aaron M. Ellison, Nicholas J. Gotelli, Douglas J. Levey
College of Arts and Sciences Faculty Publications
Historical records of species are compared with current records to elucidate effects of recent climate change. However, confounding variables such as succession, land-use change, and species invasions make it difficult to demonstrate a causal link between changes in biota and changes in climate. Experiments that manipulate temperature can overcome this issue of attribution, but long-term impacts of warming are difficult to test directly. Here we combine historical and experimental data to explore effects of warming on ant assemblages in southeastern US. Observational data span a 35-year period (1976-2011), during which mean annual temperatures had an increasing trend. Mean summer temperatures …
Rarefaction And Extrapolation With Hill Numbers: A Framework For Sampling And Estimation In Species Diversity Studies, Anne Chao, Nicholas J. Gotelli, T. C. Hsieh, Elizabeth L. Sander, K. H. Ma, Robert K. Colwell, Aaron M. Ellison
Rarefaction And Extrapolation With Hill Numbers: A Framework For Sampling And Estimation In Species Diversity Studies, Anne Chao, Nicholas J. Gotelli, T. C. Hsieh, Elizabeth L. Sander, K. H. Ma, Robert K. Colwell, Aaron M. Ellison
College of Arts and Sciences Faculty Publications
Quantifying and assessing changes in biological diversity are central aspects of many ecological studies, yet accurate methods of estimating biological diversity from sampling data have been elusive. Hill numbers, or the effective number of species, are increasingly used to characterize the taxonomic, phylogenetic, or functional diversity of an assemblage. However, empirical estimates of Hill numbers, including species richness, tend to be an increasing function of sampling effort and, thus, tend to increase with sample completeness. Integrated curves based on sampling theory that smoothly link rarefaction (interpolation) and prediction (extrapolation) standardize samples on the basis of sample size or sample completeness …
Coupling Self-Organizing Maps With A Naïve Bayesian Classifier: Stream Classification Studies Using Multiple Assessment Data, Nikolaos Fytilis, Donna M. Rizzo
Coupling Self-Organizing Maps With A Naïve Bayesian Classifier: Stream Classification Studies Using Multiple Assessment Data, Nikolaos Fytilis, Donna M. Rizzo
College of Engineering and Mathematical Sciences Faculty Publications
Organizing or clustering data into natural groups is one of the most fundamental aspects of understanding and mining information. The recent explosion in sensor networks and data storage associated with hydrological monitoring has created a huge potential for automating data analysis and classification of large, high-dimensional data sets. In this work, we develop a new classification tool that couples a Naïve Bayesian classifier with a neural network clustering algorithm (i.e., Kohonen Self-Organizing Map (SOM)). The combined Bayesian-SOM algorithm reduces classification error by leveraging the Bayesian's ability to accommodate parameter uncertainty with the SOM's ability to reduce high-dimensional data to lower …
Bioenergy Harvesting Impacts On Ecologically Important Stand Structure And Habitat Characteristics, Caitlin E. Littlefield, William S. Keeton
Bioenergy Harvesting Impacts On Ecologically Important Stand Structure And Habitat Characteristics, Caitlin E. Littlefield, William S. Keeton
Rubenstein School of Environment and Natural Resources Faculty Publications
Demand for forest bioenergy fuel is increasing in the northern forest region of eastern North America and beyond, but ecological impacts, particularly on habitat, of bioenergy harvesting remain poorly explored in the peer-reviewed literature. Here, we evaluated the impacts of bioenergy harvests on stand structure, including several characteristics considered important for biodiversity and habitat functions. We collected stand structure data from 35 recent harvests in northern hardwood-conifer forests, pairing harvested areas with unharvested reference areas. Biometrics generated from field data were analyzed using a multi-tiered nonparametric uni-and multivariate statistical approach. In analyses comparing harvested to reference areas, sites that had …
Do Anthropogenic Dark Earths Occur In The Interior Of Borneo? Some Initial Observations From East Kalimantan, Douglas Sheil, Imam Basuki, Laura German, Thomas W. Kuyper, Godwin Limberg, Rajindra K. Puri, Bernard Sellato, Meine Van Noordwijk, Eva Wollenberg
Do Anthropogenic Dark Earths Occur In The Interior Of Borneo? Some Initial Observations From East Kalimantan, Douglas Sheil, Imam Basuki, Laura German, Thomas W. Kuyper, Godwin Limberg, Rajindra K. Puri, Bernard Sellato, Meine Van Noordwijk, Eva Wollenberg
Rubenstein School of Environment and Natural Resources Faculty Publications
Anthropogenic soils of the Amazon Basin (Terra Preta, Terra Mulata) reveal that pre-Colombian peoples made lasting improvements in the agricultural potential of nutrient-poor soils. Some have argued that applying similar techniques could improve agriculture over much of the humid tropics, enhancing local livelihoods and food security, while also sequestering large quantities of carbon to mitigate climate change. Here, we present preliminary evidence for Anthropogenic Dark Earths (ADEs) in tropical Asia. Our surveys in East Kalimantan (Indonesian Borneo) identified several sites where soils possess an anthropogenic development and context similar in several respects to the Amazon's ADEs. Similarities include riverside locations, …
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
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 …
Null Model Analysis Of Species Associations Using Abundance Data, Werner Ulrich, Nicholas J. Gotelli
Null Model Analysis Of Species Associations Using Abundance Data, Werner Ulrich, Nicholas J. Gotelli
College of Arts and Sciences Faculty Publications
The influence of negative species interactions has dominated much of the literature on community assembly rules. Patterns of negative covariation among species are typically documented through null model analyses of binary presence/absence matrices in which rows designate species, columns designate sites, and the matrix entries indicate the presence (1) or absence (0) of a particular species in a particular site. However, the outcome of species interactions ultimately depends on population-level processes. Therefore, patterns of species segregation and aggregation might be more clearly expressed in abundance matrices, in which the matrix entries indicate the abundance or density of a species in …