Southeastern Vermont Research Articles

Future forest composition under a changing climate and adaptive forest management in southeastern Vermont, USA

Global change represents the greatest challenge facing forest managers today. The uncertainty and variability of potential future impacts of shifting climatic and disturbance regimes has led resource managers to seek out alternative approaches to sustain the long-term delivery of forest ecosystem services. We use a spatially explicit forest landscape simulation model, LANDIS-II, to examine and evaluate a range of long-term effects of current and adaptive forest management under three projected climate scenarios within a forested landscape in southeastern Vermont, USA. We found that land-use legacies and the inertia associated with long-term forest successional trajectories are likely to be the dominant driver of future forest composition and biomass conditions for the next 100 years. Nevertheless, climate is projected to have a greater influence on species composition and aboveground biomass over the next 200 years. Eastern hemlock (Tsuga canadensis) and red spruce (Picea rubens) are likely to experience reductions in aboveground biomass and a compression of relative dominance on the landscape. American beech (Fagus grandifolia) and sugar maple (Acer saccharum) are projected to persist within the landscape and are likely to continue to occupy a prominent compositional position in the forests of this region. Extreme climate warming under RCP 8.5 projections resulted in compositional shifts and reductions in landscape-scale aboveground biomass (120.09 ± 4.51 Mg·ha-1) at the end of the 200 year simulation when compared to RCP 4.5 (150.55 ± 1.04 Mg·ha-1) and current climate projections (147.90 ± 0.79 Mg·ha-1). These findings highlight the expected lag effects of a changing climate, which present significant challenges and opportunities as managers seek to sustain critical ecosystem services in the region.

Determining ages of multiple muscovite-bearing foliations in phyllonites using the 40Ar/39Ar step heating method: Applications to the Alleghanian orogeny in central New England

New ^40^Ar/^39^Ar data from chlorite-grade phyllonites in central New England demonstrate the effectiveness of the ^40^Ar/^39^Ar step heating method to date bulk separates containing multiple age populations of white mica. Detailed optical and scanning electron microscope (SEM) petrography of phyllonites collected along the Westminster West fault zone separating the Connecticut Valley Gaspé trough from the Bronson Hill anticlinorium shows that white mica and chlorite defining younger cleavages are recrystallized. The phyllonites are the product of retrograde shearing of higher-grade phyllites west of the fault zone. Samples dominated by two age populations outside of the fault zone yield minimum cooling ages and maximum growth ages. However, at low metamorphic grade, ^40^Ar/^39^Ar dating of white micas from the fault zone yields crystallization ages rather than cooling ages, constraining the timing of the latest movement of the fault zone. ^40^Ar/^39^Ar analyses using the step heating method indicate that west of the fault zone, muscovite cooling ages cluster at ∼365 Ma, suggesting cooling from Devonian (Acadian) metamorphism. To the east, ^40^Ar/^39^Ar analysis yields a muscovite cooling age of ∼318 Ma, suggesting cooling from a younger metamorphic event. In contrast, age steps from samples on the margins of the fault zone climb from minima of ∼306 Ma to \>340 Ma, reflecting a mixture of phyllonitic micas ≤306 Ma with relict Acadian muscovite cooling ages. A sample from the core of the fault zone yields a white mica age ∼300 Ma. These results illustrate the usefulness of the ^40^Ar/^39^Ar step heating method on bulk mineral separates regardless of complications arising from multiple age populations. Moreover, the data suggest that the boundary between the Connecticut Valley Gaspé trough (CVGT) and the Bronson Hill anticlinorium was likely a site of significant strain localization in late Pennsylvanian to early Permian times. These results imply that Late Paleozoic (Alleghanian) deformation, so well documented in coastal and southern New England, was transmitted across the composite Avalon-Ganderia crustal block to the boundary with Laurentian crust (underlying the CVGT) as far north as southeastern Vermont.

Assumptions about Consumption in the Archaeology of Late Nineteenth-Century Farmsteads

Farming is typically associated with rural environments. The Dubois Site in Albany, New York, however, presented an opportunity to look at a farmstead close to a growing urban center during the second half of the 19th century. The excavations of the Dubois Site are discussed and the results are compared to the more rural Porter Site, a contemporary 19th-century farmstead. The comparison examines how the different contexts might have impacted consumption and production at the two farms, as well as the treatment of the farmstead landscapes. The two New York sites are then contrasted with four contemporary farm sites in southeastern Vermont. The results indicate that some farmers, although rural, were fully immersed in the late 19th-century market in terms of consumption and production. In contrast, data from the Vermont sites indicate that some farmers remained tied to local markets and did not participate in the wider national market.

Magnitude and geometry of reactive fluid flow from direct inversion of spatial patterns of geochemical alteration

Time-integrated equations governing tracer mass-balance provide a framework for interpreting spatial patterns of mineralogical, elemental, and isotopic alteration in rocks caused by reactive fluid flow, and linear inverse theory allows quantitative estimates of the magnitude and three-dimensional (3D) geometry of fluid flow. We demonstrate the inverse technique with a simple model system that involves fluid advection and fluid-rock oxygen isotope exchange only. Analytic forward models of reactive transport enable patterns of isotope alteration to be calculated exactly, and inversions of the resulting spatial patterns of synthetic isotope composition demonstrate the effectiveness of our approach. For a field application of the inverse method, we consider regional metamorphic rocks from the Waits River Formation, southeastern Vermont, that expose a mineralogical and stable isotopic record of reactive fluid flow over an area of ≈120 km². Spatial patterns of prograde changes in whole-rock CO₂, δ¹⁸O, and δ¹³C allow a direct inversion for the magnitude and 3D geometry of reactive flow at the time of final prograde mineral reaction. Consistency tests suggest that the inverse estimate is primarily controlled by patterns of CO₂ changes, and resolution tests indicate that the smallest features in the inverse flux field that can be reliably detected have an east-west dimension of ≈5 km and a north-south dimension of ≈14 km. The regionally-averaged time-integrated fluid flux vector returned by the inversion has a magnitude of 2.2×10⁴ mol fluid/cm² rock, trends 255° in the horizontal plane, and is directed upward at 32° from the horizontal. The geometry of terrain-scale reactive flow was largely controlled by regional structure. Reactive fluids that entered the study area appear to have been tectonically-driven horizontally from the east at a depth ≈0.5 to 2.0 km beneath the present level of exposure.

Three-dimensional geometry of metamorphic fluid flow during Barrovian regional metamorphism from an inversion of combined petrologic and stable isotopic data

Research Article| July 01, 2002 Three-dimensional geometry of metamorphic fluid flow during Barrovian regional metamorphism from an inversion of combined petrologic and stable isotopic data Boswell A. Wing; Boswell A. Wing 1Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, Maryland 21218, USA Search for other works by this author on: GSW Google Scholar John M. Ferry John M. Ferry 1Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, Maryland 21218, USA Search for other works by this author on: GSW Google Scholar Geology (2002) 30 (7): 639–642. https://doi.org/10.1130/0091-7613(2002)030<0639:TDGOMF>2.0.CO;2 Article history received: 15 Nov 2001 rev-recd: 25 Mar 2002 accepted: 28 Mar 2002 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Boswell A. Wing, John M. Ferry; Three-dimensional geometry of metamorphic fluid flow during Barrovian regional metamorphism from an inversion of combined petrologic and stable isotopic data. Geology 2002;; 30 (7): 639–642. doi: https://doi.org/10.1130/0091-7613(2002)030<0639:TDGOMF>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Inverse calculations reveal the three-dimensional geometry of time-integrated fluid flux over a 120 km2 area during peak Barrovian regional metamorphism in southeastern Vermont. Prograde changes in whole-rock CO2, 18O, and 13C and calculated fluid compositions at the peak of metamorphism were inverted assuming tracer mass balance to obtain the time-integrated fluid flux in three dimensions. Peak metamorphic fluid flow was spatially nonuniform with flux magnitudes ranging from ∼0 to 3·105 mol fluid/cm2 rock and flux directions ranging from vertical (upward and downward) to horizontal. Averaged over the entire study area, the magnitude of the time-integrated metamorphic fluid flux vector is ∼3.4·104 mol fluid/cm2 rock. The average flux vector trends 45° to the southwest and points upward at 36° from the present horizontal, parallel to formation boundaries on a regional scale. Fluids in the terrain carried ∼3·103 mol CO2/cm2 rock toward Earth's surface during the peak of metamorphism. Results suggest that local cross-layer transport processes are secondary to terrain-scale metamorphic fluid flow in driving prograde decarbonation reactions. Regional structure exerts a first-order control on the gross geometry of peak metamorphic fluid flow. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Nitrogen saturation in a high elevation New England spruce-fir stand

High rates of nitrogen (N) deposition were first postulated as a cause of N saturation (i.e. the availability of NH4-N and NO3-N in excess of total combined plant and microbial nutritional demand) and spruce mortality during the 1980s. To test this hypothesis, N addition plots were established in 1988, in a high elevation spruce-fir forest in southeastern Vermont, an area of relatively low N deposition (5.4 kg N bulk deposition ha−1 year−1). To test how the form of applied N may influence forest growth and N-cycling, four replicated treatment plots received either NH4Cl-N, NaNO3-N, or a combination of both N forms at rates ranging from 15.7 to 31.4 kg N ha−1 year−1. The N additions were applied in three equal doses each year between June and August from 1988 to 1994. In addition to N treatments, two control plots were also established. Between 1988 and 1990, annual in situ net N mineralization and net nitrification in the forest floor, litterfall and forest floor mass and elemental concentration, foliar elemental concentration, and basal area growth by species were measured on each plot. In July 1994, basal area growth by species, net N mineralization potential and net nitrification potential in the forest floor, and foliar and forest floor elemental concentration were again measured on all plots. Inter-treatment and intra-treatment basal area growth changed substantially between 1988 and 1994. Spruce, fir, and birch trees on the N addition plots receiving <20 kg N ha−1 year−1 had the highest rate of growth between 1988 and 1990 and then had the highest rate of decline between 1991 and 1994. Spruce, fir, and birch trees on the N addition plots receiving >25 kg N ha−1 year−1 showed moderate rates of decline from 1988 to 1994. Numerous birch and maple sprouts were noted on the sites with the highest rates of decline, but no spruce or fir seedlings were observed. In July 1994, net N mineralization potential was highest on the control plots and net nitrification potential of the forest floor was highest on the plots receiving 15.7 kg N ha−1 year−1. A strong positive correlation existed between forest floor %N and net nitrification potential. Foliar %N was positively correlated with added N and negatively correlated with the change in net basal area growth. Foliar Ca:Al concentrations may also be negatively related to changes in net basal area growth. Our results suggest that N saturation has caused foliar nutrient imbalances on the N addition plots, and that the stands may be changing in species composition and structure. No long-term effects of N-form additions on N saturation and forest health were observed. Continued N additions may change the stands from a slow growing and slow N-cycling coniferous forest, to a fast N-cycling and fast growing deciduous forest.

On the Distributional History of the Arctic-Alpine Moss Cyrtomnium hymenophylloides (Mniaceae) in North America

On the Distributional History of the Arctic-Alpine Moss Cyrtomnium hymenophylloides (Mniaceae) in North America

Applications of single-grain zircon evaporation analyses to detrital grain studies and age discrimination in igneous suites

207Pb 206Pb ages determined by evaporation of single zircon grains from rocks of the New England Appalachians in the USA permit an assessment of the applicability of this method to rocks that have been strongly disturbed by orogenesis. Tests conducted on highly metamorphosed and deformed orthogneisses of known protolith age, whose U-Pb upper intercept zircon ages obtained through isotope dilution methods show profound post-crystallization discordance, demonstrate that the evaporation method is successful in recovering protolith ages. Uncertainties are ±10–15 My for rocks of Paleozoic age or older. Preliminary results suggest that the method is particularly useful for provenance studies of sedimentary rocks and in the discrimination among groups of rocks that are known to differ in age but are otherwise difficult to separate on the basis of field or petrographic characteristics. 207Pb 206Pb ages of detrital zircon grains from two metasedimentary units from opposite sides of the New England Appalachians reveal the distinct provenances of these rocks. The Missisquoi Formation in southeastern Vermont, USA, is comprised, in part, of detritus derived from the 1.0–1.2 Ga Grenvillian province of Laurentia; whereas this component is conspicuously absent from the Plainfield Formation in easternmost Connecticut. The detrital zircon age data suggest that the Missisquoi Formation accumulated peripheral to the Laurentian craton during the early Paleozoic, whereas the Plainfield Formation detritus was supplied by non-Laurentian, ossibly West African, sources during the Late Proterozoic or early Paleozoic. In southern Vermont, the evaporation method successfully distinguishes between two groups of augen gneisses with ages of ~960 Ma and ~ 1120 Ma, which were first recognized through isotope dilution methods. Collectively, these results indicate that the dating of single zircon grains by the evaporation method can be widely exploited in the study of complexly deformed and strongly metamorphosed rocks.

The origin of correlated variations in in-situ [formula omitted] and elemental concentrations in metamorphic garnet from southeastern Vermont, USA

CO 2 laser-heating in a fluorinating atmosphere was used to obtain 18O 16O analyses of coexisting garnet, staurolite, muscovite, chlorite, and quartz from a sample of the Gassetts schist, southeastern Vermont, USA. Garnet and quartz δ 18 O v- smow values vary on a millimeter scale while values for other minerals are uniform within analytical uncertainties. Garnets exhibit 18O 16O zoning with core δ 18 O values of 10.9 ± 0.3‰ and rim values of 10.1 ± 0.2. The depletion of 18O in garnet rims correlates with reversals in cation zonation and intracrystalline textural unconformities. Quartz plucked from a garnet core yields a δ 18 O of 14.8‰ while vein quartz δ 18 O values vary from 14.3 ± 0.2 in centers to 13.8 ± 0.1 at margins. Staurolite, muscovite, and chlorite have mean δ 18 O values of 10.8, 11.9, and 10.3, respectively. Two parageneses are distinguished on the basis of the mineral δ 18 O and expected isotope partitioning and on the basis of textures. One consists of garnet cores, staurolite, muscovite, and quartz included in garnet. Garnet rims, chlorite, and vein quartz comprise the other. Quantitative models which explain the lower bulk δ 18 O of the garnet-rim assemblage show that garnet textural unconformities represent resorption during infiltration of externally derived aqueous fluid. Chlorite grew by this hydration reaction and was the principal storage site for low 18O 16O oxygen. Low- δ 18 O garnet rims later grew at the expense of chlorite with little change in modal abundances of staurolite and muscovite. Retention of pre-infiltration δ 18 O in muscovite precludes significant diffusion of oxygen in this phase and indicates that the total duration of external fluid flow was ≤ 10 5 years.

Characteristics of Northern Hardwood Trees Used by Cavity-Nesting Birds

Characteristics of Northern Hardwood Trees Used by Cavity-Nesting Birds

Polymetamorphic garnet zoning from southeastern Vermont

<h3>Abstract</h3> Histological studies providing cellular insights into tissue architecture have been central to biological discovery and remain clinically invaluable today. Extending histology to three dimensions would be transformational for research and diagnostics. However, three-dimensional histology is impractical using current techniques. We have customized sample preparation, synchrotron X-ray tomographic parameters, and three-dimensional image analysis to allow for complete histological phenotyping using whole larval and juvenile zebrafish. The resulting digital zebrafish can be virtually sectioned and visualized in any plane. Whole-animal reconstructions at subcellular resolution also enable computational characterization of the zebrafish nervous system by region-specific detection of cell nuclei and quantitative assessment of individual phenotypic variation. Three-dimensional histological phenotyping has potential use in genetic and chemical screens, and in clinical and toxicological tissue diagnostics. <h3>One Sentence Summary</h3> Synchrotron X-ray micro-tomography can be used to rapidly create 3-dimensional images of fixed and stained specimens without sectioning, enabling computational histological phenotyping at cellular resolution.

Fluid Inclusion Evidence of Silurian Evaporites in Southeastern Vermont

Fluid inclusions were studied in some 300 samples of quartz, taken from quartz pods, lenses, and veins occurring in the biotite, garnet, and staurolite-kyanite zones of metamorphosed Paleozoic and Pre-cambrian rocks in eastern Vermont. Most of the samples were taken from conformable quartz pods within a 200-km 2 area of detailed study on the east flank of the Chester and Athens mantled gneiss domes in the southeastern part of the state (Fig. 1). This area is dominated by a steeply dipping sequence of garnet-zone metamorphic rocks of Silurian-Devonian age which occurs stratigraphically above the Taconic unconformity (Fig. 1). The lower part of the Silurian-Devonian section in this area consists of a transgressive marine sequence, which begins with conglomeratic quartzite, dolomitic carbonate, and minor schist and amphibolite of the basal Shaw Mountain Formation, and it is overlain by interbedded metapelites and dolomatic carbonates of the Northfield and Waits River Formations. The Geologic Map of Vermont (Doll and others, 1961) and details field investigations by Hepburn (1972), Rosenfeld (1954, 1968), and Thompson (1950) provided the regional geological framework for the present study. Within the field area, conformable quartz pods averaging several centimetres in length are abundant in Silurian-Devonian pelitic rocks of garnet zone or higher metamorphic grade. Where the same rock units are less metamorphosed, conformable quartz pods are rare or absent, and crosscutting quartz veins and lenses are common. This suggests that the conformable quartz pods in the study area developed during garnet one metamorphism. Fluid inclusions were looked for but not found in numerous grains of rock quartz; the present quartz pod sites therefore appear to have been loci of fluid-phase activity during the regional metamorphism.

Fluid inclusion evidence for Silurian evaporites in southeastern Vermont: Summary

Fluid inclusion evidence for Silurian evaporites in southeastern Vermont: Summary

Paleomagnetism of rocks from the White Mountain plutonic-volcanic series in New Hampshire and Vermont

Samples were collected at 17 sites in gabbros, monzonites, and diorites of the White Mountain plutonic-volcanic series in New Hampshire and Vermont. No useful information was obtained from the diorites. The main mass of the White Mountain series has been dated at 180 m.y. After partial demagnetization by alternating fields to remove unstable components of magnetization, the directions of magnetization became very well grouped; both normal and reversed directions are present. The mean direction and parameters for 12 sites are D = 358½°, I = 59°, R = 11.9, and K = 110, yielding a paleomagnetic pole at 85½°N and 124½°E with p = 4½°, m = 6°. Samples were taken from two sites in the gabbro of the Mount Ascutney intrusive in southeastern Vermont. This instrusive is younger than the rocks of the White Mountain plutonic-volcanic series and has been dated by K-Ar at 125 to 135 m.y. These sites gave paleomagnetic pole positions which are in agreement with other Upper Jurassic-Cretaceous pole positions from North America.

STRUCTURE AND METAMORPHISM OF THE KEENE-BRATTLE-BORO AREA, NEW HAMPSHIRE-VERMONT

Metamorphosed sedimentary and volcanic rocks, ranging in age from middle Ordovician (?) to lower Devonian, occupy about 55 per cent of the Keene-Brattleboro area of southwestern New Hampshire and southeastern Vermont. Rocks of the low-grade zone of metamorphism are present in a north-south band near the western edge of the area; rocks of the middle-grade zone occur on either side of the low-grade zone; and rocks of the high-grade zone occupy the central and eastern parts of the area. The lithology of the stratified rocks is similar to that farther north. The Bernardston formation of north-central Massachusetts is correlated with the Littleton formation. Foliated igneous rocks of middle Devonian (?) and late Devonian (?) age occupy about 45 per cent of the area. These include three plutons of the Oliverian magma series and five members of the New Hampshire magma series. The stratified rocks were severely folded, broken by a major thrust fault, and metamorphosed during the late Devonian (Acadian) orogeny. The resulting structural features in this area, trend almost north. The Bronson Hill anticline occupies most of the area. Three elongate domes, each with a plutonic core of the Oliverian magma series and a surrounding envelope of stratified rock, are present on this anticline. A pluton of Kinsman quartz monzonite occurs in a structural basin on the anticline, near the center of the area. The steeply dipping western limb of the Brattleboro syncline occupies the western one-eighth of the area. The Northey Hill thrust, a major fault of western New Hampshire, separates the Bronson Hill anticline from the Brattleboro syncline. This thrust, which cuts out the eastern limb of the Brattleboro syncline, has a stratigraphic separation of about 10,000 feet. Foliation and bedding are mutually parallel in most of the stratified rocks east of the Northey Hill thrust, whereas foliation is parallel to the axial planes of folds in most of the rocks west of the thrust. Minor folds of two ages are present west of the thrust and in a few places just east of thrust. The older minor folds are isoclinal, or nearly so, and have a well-developed axial-plane flow cleavage. The younger minor folds are more open and have an incipient to strong axial-plane slip cleavage. It is believed that the Oliverian magma series was forcefully injected as a thick composite sheet during the very early stages of the orogeny, while the enclosing rocks were essentially flat. The New Hampshire magma series was emplaced during the late stages of the orogeny. Initial movements along the Northey Hill thrust may have occurred during early stages of the orogeny, but a considerable part of the movement took place after the metamorphic intensity in the rocks along the fault had reached its maximum. The Triassic border fault, which forms the eastern border of the Triassic rocks of the Connecticut valley in Massachusetts, enters the area 1 mile east of the Connecticut River and trends northeasterly to the vicinity of Keene, where it apparently ends. The maximum stratigraphic displacement along the fault is about 15,000 feet. Numerous small high-angle normal faults are present. In three localities, graben, in which the roof of one of the plutons of the Oliverian magma series is preserved, form very striking structural features. The normal faults which bound the graben have a maximum stratigraphic separation of 3000 to 4000 feet. The age of the faulting associated with the graben, and also much of the normal faulting of western New Hampshire, is believed to be Triassic. Fluorite deposits of the Keene-Brattleboro area are also believed to be Triassic.

GNEISS DOME AT SHELBURNE FALLS, MASSACHUSETTS

The Shelburne Falls gneiss dome, in the eastern Berkshire Hills of western Massachusetts, consists of amphibolitic metavolcanics, intruded by sills and complex lit-par-lit injection zones of a quartz diorite and its associated volatiles. The dome is surrounded by the Conway schist of early Paleozoic age. The principal rock types are described. The dome surface dips outward at gentle angles, and the gneiss-schist contact is conformable, though an original unconformity is suggested in a few places. Sills or apophyses of quartz diorite in the schist are lacking. Neither the distribution of metacrysts nor the mineral composition and texture of the schist shows zoning with regard to the gneiss dome. It is concluded that the gneiss complex is older than the Conway schist, but that both the Conway schist and the gneiss have been silicified near the dome border, and chlorite, muscovite, tourmaline, and a few thin pegmatites have been introduced near this surface. It seems that these changes occurred during, or soon after, the metamorphism of the Conway sediments. At about the same time a few dikes of quartz diorite porphyry were intruded into the gneiss and the schist. At least 3 of them have been silicified, tourmalinized, and micacized. Tightly compressed, isoclinally folded amphibolite tracts in the gneiss complex, with axes of folds and lineation in various directions, contrast with gently flexed or mildly folded Conway schist in the vicinity of the dome. Axes of folds and lineation pitch off the dome for the most part, though not everywhere in the steepest directions. Inward-dipping funnel joints near the dome border, and steep fractures radiating outward from it, attest to the mechanical expansion of the crust during the doming. The association of amphibolitic metavolcanics with soda-rich igneous rocks, in the gneiss complex, resembles that of certain gneissic terranes in southeastern Vermont and southwestern New Hampshire more closely than the microcline-rich gneisses of the crest of the Berkshire Hills.