Andrew L. Thurman

Statistically-Estimated Tree Composition for the Northeastern United States at Euro-American Settlement

We present a gridded 8 km-resolution data product of the estimated composition of tree taxa at the time of Euro-American settlement of the northeastern United States and the statistical methodology used to produce the product from trees recorded by land surveyors. Composition is defined as the proportion of stems larger than approximately 20 cm diameter at breast height for 22 tree taxa, generally at the genus level. The data come from settlement-era public survey records that are transcribed and then aggregated spatially, giving count data. The domain is divided into two regions, eastern (Maine to Ohio) and midwestern (Indiana to Minnesota). Public Land Survey point data in the midwestern region (ca. 0.8-km resolution) are aggregated to a regular 8 km grid, while data in the eastern region, from Town Proprietor Surveys, are aggregated at the township level in irregularly-shaped local administrative units. The product is based on a Bayesian statistical model fit to the count data that estimates composition on the 8 km grid across the entire domain. The statistical model is designed to handle data from both the regular grid and the irregularly-shaped townships and allows us to estimate composition at locations with no data and to smooth over noise caused by limited counts in locations with data. Critically, the model also allows us to quantify uncertainty in our composition estimates, making the product suitable for applications employing data assimilation. We expect this data product to be useful for understanding the state of vegetation in the northeastern United States prior to large-scale Euro-American settlement. In addition to specific regional questions, the data product can also serve as a baseline against which to investigate how forests and ecosystems change after intensive settlement. The data product is being made available at the NIS data portal as version 1.0.

Temporal variation in viral hemorrhagic septicemia virus antibodies in freshwater drum (Aplodinotus grunniens) indicates cyclic transmission in Lake Winnebago, Wisconsin

ABSTRACT Viral hemorrhagic septicemia virus (VHSV) is an emerging pathogen that causes mass mortality in multiple fish species. In 2007, the Great Lakes freshwater strain, type IVb, caused a large die-off of freshwater drum (Aplodinotus grunniens) in Lake Winnebago, Wisconsin, USA. To evaluate the persistence and transmission of VHSV, freshwater drum from Lake Winnebago were tested for antibodies to the virus using recently developed virus neutralization (VN) and enzyme-linked immunosorbent (ELISA) assays. Samples were also tested by real-time reverse transcription-PCR (rRT-PCR) to detect viral RNA. Of 548 serum samples tested, 44 (8.03%) were positive by VN (titers ranging from 1:16 to 1:1,024) and 45 (8.21%) were positive by ELISA, including 7 fish positive by both assays. Antibody prevalence increased with age and was higher in one northwestern area of Lake Winnebago than in other areas. Of 3,864 tissues sampled from 551 fish, 1 spleen and 1 kidney sample from a single adult female fish collected in the spring of 2012 tested positive for VHSV by rRT-PCR, and serum from the same fish tested positive by VN and ELISA. These results suggest that VHSV persists and viral transmission may be active in Lake Winnebago even in years following outbreaks and that wild fish may survive VHSV infection and maintain detectable antibody titers while harboring viral RNA. Influxes of immunologically naive juvenile fish through recruitment may reduce herd immunity, allow VHSV to persist, and drive superannual cycles of transmission that may sporadically manifest as fish kills.

Detection of smoothly distributed spatial outliers, with applications to identifying the distribution of parenchymal hyperinflation following an airway challenge in asthmatics

Methacholine challenge tests are used to measure changes in pulmonary function that indicate symptoms of asthma. In addition to pulmonary function tests, which measure global changes in pulmonary function, computed tomography images taken at full inspiration before and after administration of methacholine provide local air volume changes (hyper-inflation post methacholine) at individual acinar units, indicating local airway hyperresponsiveness. Some of the acini may have extreme air volume changes relative to the global average, indicating hyperresponsiveness, and those extreme values may occur in clusters. We propose a Gaussian mixture model with a spatial smoothness penalty to improve prediction of hyperresponsive locations that occur in spatial clusters. A simulation study provides evidence that the spatial smoothness penalty improves prediction under different data-generating mechanisms. We apply this method to computed tomography data from Seoul National University Hospital on five healthy and ten asthmatic subjects. Copyright

A new application of change point analysis reveals extensive edge effects on a temperate mixed forest

Questions nHow do landscape changes along edges of protected areas affect forest interiors and stand development? What are the locations, spatial extents and magnitudes of these effects? n nLocation nThe 8500-ha Sylvania Wilderness Area, Michigans Upper Peninsula, USA. n nMethods nWe conducted vegetation surveys in 202 plots in ten transects crossing the Sylvania Wilderness border in 2013 and 2014. We recorded characteristics of forest structure, trees, shrubs, saplings, seedlings and herbaceous species. We constructed GLMM to estimate the location, spatial extent and magnitude of change of edge effects on Sylvania with a range of possible edge effect locations and widths of effect. We selected best-fit models that minimized the AIC and applied likelihood ratio tests to assess the statistical significance of each edge effect. n nResults nOverall, evidence of edge effects occurred up to 625xa0m into the Sylvania Wilderness, with most significant changes occurring within 400xa0m of the wilderness border. Wide zones of change occurred across the wilderness border, while zones of change farther from the edge tended to be narrower, suggesting that distinct environments are established beyond the transitional habitats surrounding the border region. Canopy-level and understorey-level variables exhibited the largest magnitudes and steepest gradients of change, indicating these communities are strongly influenced by edge effects in this forest system. Canopy-level heterogeneity also increased approaching the internal core area of Sylvania. n nConclusions nIn this case study, we applied a linear change point model and found a minimum buffer zone of 400xa0m to mitigate edge effects in an old-growth temperate mixed forest. Regionally, land managers could implement this buffer to existing edges of protected areas or negotiate this buffer zone in land acquisitions. A more stringent buffer zone of 625xa0m internal and 250xa0m external to old-growth forests would be ideal. This application of change point analysis provides a simple, efficient method to establish effective buffer zones and to identify functional groups or ecosystem attributes for which edge effects are of greatest conservation concern. We recommend modifying our open-source change point package to estimate local edge effects that take into account regional characteristics.