Person: Cogbill, Charles
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Cogbill
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Charles
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Cogbill, Charles
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Publication Four Centuries of Change in Northeastern United States Forests(Public Library of Science, 2013) Thompson, Jonathan R.; Carpenter, Dunbar N.; Cogbill, Charles; Foster, DavidThe northeastern United States is a predominately-forested region that, like most of the eastern U.S., has undergone a 400-year history of intense logging, land clearance for agriculture, and natural reforestation. This setting affords the opportunity to address a major ecological question: How similar are today's forests to those existing prior to European colonization? Working throughout a nine-state region spanning Maine to Pennsylvania, we assembled a comprehensive database of archival land-survey records describing the forests at the time of European colonization. We compared these records to modern forest inventory data and described: (1) the magnitude and attributes of forest compositional change, (2) the geography of change, and (3) the relationships between change and environmental factors and historical land use. We found that with few exceptions, notably the American chestnut, the same taxa that made up the pre-colonial forest still comprise the forest today, despite ample opportunities for species invasion and loss. Nonetheless, there have been dramatic shifts in the relative abundance of forest taxa. The magnitude of change is spatially clustered at local scales (<125 km) but exhibits little evidence of regional-scale gradients. Compositional change is most strongly associated with the historical extent of agricultural clearing. Throughout the region, there has been a broad ecological shift away from late successional taxa, such as beech and hemlock, in favor of early- and mid-successional taxa, such as red maple and poplar. Additionally, the modern forest composition is more homogeneous and less coupled to local climatic controls.Publication Variations in Old-Growth Structure and Definitions: Forest Dynamics on Wachusett Mountain, Massachusetts(Wiley-Blackwell, 2001) Orwig, David; Cogbill, Charles; Foster, David; O, John F.One of the largest old-growth forests in southern New England was recently ‘‘discovered’’ on the exposed upper slopes of Wachusett Mountain, Massachusetts, a heavily used recreational area located ,80 km (,50 miles) from Boston. We analyzed historical records, dendroecological data, vegetation, and coarse woody debris to characterize the dynamics and development of four major old-growth stands on the mountain and explored the potential factors enabling these forests to survive and elude recognition as old-growth forests for .150 yr. Historical data suggest that most of the area’s forests were composed of a mixture of Quercus rubra and northern hardwood species. Species abundances and recruitment dynamics in the four stands exhibit highly variable spatial and temporal patterns across sites that differ in aspect and exposure. Three uneven-aged hardwood stands contain Quercus rubra in the largest size classes, various amounts of Fagus grandifolia, Acer, and Betula species in the middle size classes, and dense thickets of several shrub species in the small size classes. Several of a set of randomly aged individuals of Q. rubra, B. lenta, and B. alleghaniensis are at or very near the maximum longevity known for these species. A Tsuga canadensis stand contains unimodal size and age distributions, with trees ,60- cm dbh and 100–300 yr old. Quercus rubra recruitment occurred on all sites from the 1600s through the early 1800s, when it dropped precipitously on most sites and was replaced by either Tsuga or Acer and Betula species. These recruitment changes were apparently driven by changes in disturbance regime over the last two centuries, from fire in the early record to hurricanes (1815 and 1938), and more recently, frequent wind, ice, and snow damage but no fire. Asynchronous tree-ring releases and suppression and relatively low amounts of coarse woody debris corroborate this interpretation. Chronic canopy damage produced short-statured and unusually gnarled trees, which gave the forest unusual resistance to severe winds from hurricanes, discouraged logging, and prevented the recognition of the forest’s old-growth status despite its heavy recreational use.Publication Statistically-Estimated Tree Composition for the Northeastern United States at Euro-American Settlement(Public Library of Science, 2016) Paciorek, Christopher J.; Goring, Simon J.; Thurman, Andrew L.; Cogbill, Charles; Williams, John W.; Mladenoff, David J.; Peters, Jody A.; Zhu, Jun; McLachlan, Jason S.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.Publication Novel and Lost Forests in the Upper Midwestern United States, from New Estimates of Settlement-Era Composition, Stem Density, and Biomass(Public Library of Science, 2016) Goring, Simon J.; Mladenoff, David J.; Cogbill, Charles; Record, Sydne; Paciorek, Christopher J.; Jackson, Stephen T.; Dietze, Michael C.; Dawson, Andria; Matthes, Jaclyn Hatala; McLachlan, Jason S.; Williams, John W.Background: EuroAmerican land-use and its legacies have transformed forest structure and composition across the United States (US). More accurate reconstructions of historical states are critical to understanding the processes governing past, current, and future forest dynamics. Here we present new gridded (8x8km) reconstructions of pre-settlement (1800s) forest composition and structure from the upper Midwestern US (Minnesota, Wisconsin, and most of Michigan), using 19th Century Public Land Survey System (PLSS), with estimates of relative composition, above-ground biomass, stem density, and basal area for 28 tree types. This mapping is more robust than past efforts, using spatially varying correction factors to accommodate sampling design, azimuthal censoring, and biases in tree selection. Changes in Forest Structure We compare pre-settlement to modern forests using US Forest Service Forest Inventory and Analysis (FIA) data to show the prevalence of lost forests (pre-settlement forests with no current analog), and novel forests (modern forests with no past analogs). Differences between pre-settlement and modern forests are spatially structured owing to differences in land-use impacts and accompanying ecological responses. Modern forests are more homogeneous, and ecotonal gradients are more diffuse today than in the past. Novel forest assemblages represent 28% of all FIA cells, and 28% of pre-settlement forests no longer exist in a modern context. Lost forests include tamarack forests in northeastern Minnesota, hemlock and cedar dominated forests in north-central Wisconsin and along the Upper Peninsula of Michigan, and elm, oak, basswood and ironwood forests along the forest-prairie boundary in south central Minnesota and eastern Wisconsin. Novel FIA forest assemblages are distributed evenly across the region, but novelty shows a strong relationship to spatial distance from remnant forests in the upper Midwest, with novelty predicted at between 20 to 60km from remnants, depending on historical forest type. The spatial relationships between remnant and novel forests, shifts in ecotone structure and the loss of historic forest types point to significant challenges for land managers if landscape restoration is a priority. The spatial signals of novelty and ecological change also point to potential challenges in using modern spatial distributions of species and communities and their relationship to underlying geophysical and climatic attributes in understanding potential responses to changing climate. The signal of human settlement on modern forests is broad, spatially varying and acts to homogenize modern forests relative to their historic counterparts, with significant implications for future management.