Biology subjects

Foster, D. R.

Publications and source records attributed to Foster, D. R..

3 recordsLinked to original sources

bioRxiv2019

Potential impacts of insect-induced harvests in the mixed forests of New England

Forest insects and pathogens (FIPs) have significant impacts on U.S. forests, each year affecting an area nearly three times the area of wildfires and timber harvesting combined. We surveyed family forest owners (FFOs) in the northeastern U.S. and 84% of respondents indicated they would harvest in at least one of the presented FIP infestation scenarios. This harvest response represents a potentially significant shift in the timing, extent, and species selection of harvesting in the Northeast. Here we used the landowner survey, regional forest inventory data, and characteristics of the emerald ash borer (EAB, Agrilus planipennis) invasion to examine the potential for a rapidly spreading FIP to alter harvest regimes and affect regional forest conditions. Twenty-five percent of the FFO parcels in the Connecticut River Watershed in New England are likely to be harvested in response to EAB within 10 years. This prediction represents an increase in harvest frequencies, from 2.9%/yr (historically) to 3.7%/yr, on FFO woodlands. At typical harvest intensities, this would result in 13% of the total aboveground biomass removed through these harvests, with 81% of that biomass from species other than ash, creating a forest disturbance that is over twice the magnitude of the disturbance from EAB alone.

ecology↗

bioRxiv2019

Multivariate climate change, the climate niche, and the Holocene history of eastern hemlock (Tsuga canadensis)

Forests in the eastern North America have changed progressively over the 11,700 years of the Holocene Epoch. To understand the dynamics involved, we focus on eastern hemlock (Tsuga canadensis), which shifted its distribution through time and, notably, exhibited a rapid range-wide decline at 5280{+/-}180 YBP. We consider how climate could have shaped this history by comparing fossil pollen records from eight New England sites with quantitative temperature and effective precipitation reconstructions and evaluating the realization of Tsugas climate niche through time. The comparisons indicate that multivariate climate change significantly influenced Tsuga abundance, including its abrupt decline and recovery. The comparisons show that the realized climate niche of Tsuga expressed today includes two important features that persisted through time. First, Tsuga pollen percentages reach their maxima (>30%) where July temperatures equal 18-20{degrees}C, but do so at two modes where annual precipitation equals either [~]1100 or [~]775 mm. The bimodality reflects Tsugas two geographic modes in the Great Lakes and Appalachian regions today, and explains past dynamics, such as short-lived peaks in Tsuga abundance associated with effective precipitation of [~]775 mm at ca. 10,000 years before CE 1950 (YBP). Second, the two peaks in Tsuga abundance follow negative correlations between temperature and precipitation such that the two modes shift toward high precipitation if temperatures are low (e.g., [~]1400 and [~]1000 mm at <18{degrees}C). Consequently, rapid cooling at 5200{+/-}100 YBP facilitated widespread Tsuga declines because cooling did not coincide with increased precipitation. Abundance declined as local climates departed from optimal temperature and precipitation combinations. Recovery only followed as effective precipitation increased by >150 mm over the past 4000 years. A regionally calibrated model of the relationship of Tsuga pollen percentages to temperature and precipitation explains 70-75% of the variance in the percentages at eight study sites. Iteratively excluding each site from the model shows that accurately representing the major features of the climate niche enables the model to predict the mid-Holocene decline and other past changes at the excluded site (site-level RMSE = 2.1-5.6%). Similar multivariate climate dynamics closely modulated the species abundance throughout the Holocene with no evidence of additional large-scale disturbances.

ecology↗

bioRxiv2017

Widespread sampling biases in herbaria revealed from large-scale digitization

O_LINon-random collecting practices may bias conclusions drawn from analyses of herbarium records. Recent efforts to fully digitize and mobilize regional floras offer a timely opportunity to assess commonalities and differences in herbarium sampling biases.\nC_LIO_LIWe determined spatial, temporal, trait, phylogenetic, and collector biases in [~]5 million herbarium records, representing three of the most complete digitized floras of the world: Australia (AU), South Africa (SA), and New England (NE).\nC_LIO_LIWe identified numerous shared and unique biases among these regions. Shared biases included specimens i) collected close to roads and herbaria; ii) collected more frequently during spring; iii) of threatened species collected less frequently; and iv) of close relatives collected in similar numbers. Regional differences included i) over-representation of graminoids in SA and AU and of annuals in AU; and ii) peak collection during the 1910s in NE, 1980s in SA, and 1990s in AU. Finally, in all regions, a disproportionately large percentage of specimens were collected by a few individuals. These mega-collectors, and their associated preferences and idiosyncrasies, may have shaped patterns of collection bias via founder effects.\nC_LIO_LIStudies using herbarium collections should account for sampling biases and future collecting efforts should avoid compounding these biases.\nC_LI

plant biology↗