Camels Hump Research Articles

Threshold Increases in Soil Lead and Mercury from Tropospheric Deposition Across an Elevational Gradient

Atmospheric deposition is the primary mechanism by which remote ecosystems are contaminated, but few data sets show how fluxes change and control soil metal burdens at the landform scale. We present mercury (Hg), lead ((210)Pb and total Pb), and cosmogenic beryllium-7 ((7)Be) measurements in organic (O) soil horizons at high-resolution elevation intervals of ∼60 m from 540 to 1160 m on Camels Hump in northern Vermont, USA. Across this gradient, average O horizon Hg ranges from 0.99 mg m(-2) in the low elevation deciduous forest zone to 7.6 mg m(-2) in the higher elevation coniferous forest at 1030 m. We measure two pronounced threshold increases in soil metal burdens above 801 and 934 m, corresponding to the two most common altitudes of cloud base, which coincide with changes in vegetation species. Lead-210, a unique tracer of tropospheric deposition, also increased from 3200 Bq m(-2) to 11500 Bq m(-2) in O horizons, exhibiting threshold responses at the same elevations as Hg and total Pb. Concentrations of (210)Pb and Hg in foliage double from 760 to 900 m elevation, indicating enhanced deposition across the transition from deciduous to coniferous forest. In contrast, (7)Be is constant across the entire elevational gradient because of its upper atmospheric source. This indicates that the effects of orographic precipitation have a smaller control on soil contaminant burdens than the coupled cloudwater deposition-vegetation scavenging effect in the presence of upwind sources. By measuring soil contaminants and unique tracers of atmospheric deposition, we show that tropospheric fluxes of Hg and Pb are higher by a factor of 2 in high-elevation coniferous forests than in adjacent lowlands. Total O horizon Hg and Pb burdens increase by over 4-fold with elevation because of the compounding effects of enhanced deposition and longer metal residence times at higher elevations (>50 years).

Species shifts in response to climate change: Individual or shared responses?1,2

Abstract Individual species are expected to shift their distributions in response to global climate change. Species within existing communities may respond to climate change individualistically, resulting in the formation of novel communities, or may instead shift as intact communities. We examined whether montane plant communities in the northeastern United States have shifted their elevational range as intact assemblages or individualistically in response to recent regional climatic and environmental change. We used non-metric multidimensional scaling (NMDS) to examine changes in plant community composition and species distributions using vegetation surveys repeated five times between 1964 and 2006 across an elevational gradient (549–1158 m) on Camels Hump Mountain, Vermont, USA, in conjunction with an analysis of local climate change. We found evidence that species elevational distributions and community compositions have shifted in response to a 0.49 °C per decade warming. These species responses were...

Using stable and radioactive isotopes to trace atmospherically deposited Pb in montane forest soils.

Atmospheric deposition of lead (Pb) throughout the 1900s resulted in elevated amounts of this toxic metal even in remote forest soils of the northeastern United States. Soils can act as a net sink for metals and thus minimize groundwater and surface water contamination. Recent studies utilizing forest floor temporal data and models of total Pb in precipitation, surface soils, and streams have estimated the time scale of Pb release from soils. However, due to the limited availability and spatial variability of forest floor survey data, other methods for quantifying anthropogenic Pb movement are needed. This study uses the isotopic composition (206Pb/207Pb) of soil Pb and measurements of 210Pb and 226Ra to directly trace the transit of atmospherically deposited Pb in the soil profile. We also report on the recovery of an enriched 207Pb dose applied in 1984 to the surface of a soil plot in the coniferous forest at Camels Hump in Vermont. The isotopic composition of soil Pb in low elevation deciduous forests suggests that approximately 65% of the original atmospheric Pb load has migrated from the forest floor to the upper 10 cm of the mineral soil. Higher elevation sites with coniferous vegetation have thicker forest floors, which have prevented significant amounts of Pb from entering the mineral soil. After 17 years, the soil organic horizon in the coniferous zone prevented any penetration of the applied Pb into the mineral soil. Using 210Pb budgets in different soil compartments, we determine forest floor response times for atmospherically delivered Pb to be approximately 60 years in the low elevation deciduous forest zone and 150 years for the high elevation spruce-fir forest zone at Camels Hump. According to its distribution in the soil profile, we conclude that a dispersed release of anthropogenic Pb to groundwater and surface water is possible this century. Our results also offer independent confirmation of Pb deposition models previously generated for the region.

Periodical Appearance of Korscheltellus gracilis (Lepidoptera: Hepialidae)

Korscheltellus gracilis (Grote) has a 2-yr life cycle, with numbers of emerging adults in odd and even years differing by one to two orders of magnitude. Results from starch-gel electrophoresis of allozymes suggest that the odd- and even-year broods from Camels Hump Mountain, Vermont, may be the same population, with little genetic differentiation. Distribution maps of field collections and museum records show periodical abundance at the vast majority of localities, thus refuting hypotheses of recent colonization and natural abiotic catastrophe. Available evidence for competition, parasitism, and pathogens as agents of periodical abundance in K. gracilis is discussed.

Techniques for pollution monitoring in remote sites: III. Near real-time monitoring of cloud water conductivity and pH

A semi-portable flow-through cloud water monitoring system was developed for measurements of cloud water conductivity and pH in remote sites lacking AC line power. This system was tested from May to September on Camels Hump mountain, Vermont. High temporal resolution data from seven cloud events were collected during the 1991 growing season. Mean cloud water conductivity and pH for all events was 467 μmhos cm−1 and 3.2, respectively. The highest conductivity was 997 (μmhos cm−1 recorded on 19 September 1991 and the lowest pH of 2.9 was recorded during several events over the summer. Data from this system may be used to achieve a better understanding of the chemical environment in areas experiencing forest decline.

Inferences of Korscheltellus gracilis (Lepidoptera: Hepialidae) Habitat Utilization from Sticky Trap Catches on Camels Hump Mountain, Vermont

Numbers of Korscheltellus gracilis (Grote) adults caught on sticky traps are compared between: east and west aspects of Camels Hump Mountain, open canopy gaps and mature conifer stands at 1,000 m elevation, and within dense conifer stands, glades, and glade edges. Numbers trapped were significantly higher on the west aspect and in mature open understory conifer stands. More moths were trapped in glades and along glade edges than in dense conifer stands. Males were caught most often at ground level in dense conifers, at 1 and 2 m height in glades, and at 1 m on glade edges. We suggest that males fly through glades and small gaps searching for female pheromone plumes, and mated females deposit their eggs while perching between short flights.

Historical Species Loss in the Alpine Zone of Camels Hump, Vermont

Historical Species Loss in the Alpine Zone of Camels Hump, Vermont

Feeding by Korscheltellus gracilis (Lepidoptera: Hepialidae) Larvae on Roots of Spruce and Fir

Feeding habits of Korscheltellus gracilis (Grote) were determined in the laboratory and field in Vermont. Gymnospenn and angiosperm seedlings and one fern were exposed to larvae. Significant reductions in root length or volume occurred in all three taxa. Larvae removed root bark and phloem and often girdled stem bases. Feeding damage was similar to that found in high elevation spruce-fir forests on Camels Hump Mountain, VT. The feeding experiments suggest that this insect may have a negative effect on regeneration and contribute to red spruce ( Picea rubens ) and balsam fir ( Abies balsamea ) decline in the northeastern United States.

Association of Korscheltellus gracilis Larvae (Lepidoptera:Hepialidae) with Canopy Species and Forest Structure on Camels Hump Mountain in Vermont

The spatial relationships between density of Korscheltellus gracilis (Grote) larvae, canopy species, and forest structure (gaps; gap edges; dense, young tree stands; and older tree stands) were investigated. Larvae at 1,000-m elevation on Camels Hump Mountain, Huntington, VT, were associated with dense, young stands of regenerating balsam fir (Abies balsamea [L.]) and fir defining the edges of wood fern( Dryopterus campyloptera Clarkson) gaps. The consequences of these associations on life-table sampling methods and gap dynamics are discussed.

Techniques for pollution monitoring in remote sites: I. Near real-time rainfall pH and depth

A flow-through system for in situ, near real-time, sequential measurements of rainfall pH and depth was developed for monitoring of precipitation in sites lacking electric power. The system is easily fabricated from readily available instruments and materials, portable, relatively inexpensive and requires minimal maintenance. It also operates independently of AC power making it ideal for use in remote areas. Initial field testing of this system on Camels Hump, Vermont, took place over the period of July to August 1990, during which twenty-seven individual storm events were monitored. The system proved to be robust and reliable, providing rainfall pH and depth information with high (programmable) temporal resolution for unattended periods of up to a week.

Survey Methods, Distribution, and Seasonality of Korscheltellus gracilis (Lepidoptera: Hepialidae) in the Green Mountains, Vermont

In 1983, large populations of Korscheltellus gracilis (Grote) were discovered in soil in the boreal zone of Camels Hump Mountain, Vt. A monitoring procedure was developed to evaluate population dynamics and abundance. The insect was most abundant at elevations of 1,000–1,150 m where red spruce and balsam fir grow and spruce decline is most evident. Flight occurs from late June through early August, and K. gracilis adults were trapped in 19 of 20 sites in the Green Mountain National Forest. They were significantly more abundant at high elevations and on even years.

Spruce–fir decline and gap dynamics on Camels Hump, Vermont

Widespread and conspicuous dieback of red spruce (Picearubens Sarg.) accompanied by asymptomatic declines in balsam fir (Abiesbalsamea (L.) Mill.) and white birch (Betulapapyrifera var. cordifolia (Regel.) Fern.) trees on Camels Hump, Vermont, prompted an investigation into the role of spruce–fir decline on gap expansion, tree health, and regeneration dynamics. Forty percent of the study area on Camels Hump was occupied by recent forest gaps in the summer of 1989. Gaps were growing northwesterly (direction 322°) at a rate of 0.8–1.2 m•year−1. Prevailing winds in the study area are from the south-southeast. Gap expansion appears to play a dominant role in continuing forest disturbance. Red spruce vigor was low in all dominance classes (53% foliar retention), while vigor of balsam fir and birch (yellow (Betulaalleghaniensis Britt.) and white) was somewhat higher. Exposure and wind flagging of different tree species within the same crown dominance classes were similar, but apical foliar damage was greater in spruce than in fir or birch. Red spruce and birch trees were older than balsam fir within comparable crown classes. Wind flagging was significantly correlated with crown exposure in red spruce and balsam fir, while diameter was the most important factor related to flagging in birch. All three species tended to die while standing. Dead balsam fir trees were twice as likely as red spruce to have been windthrown or diseased, whereas dead red spruce showed a much higher incidence of past and present insect infestation. Live birch had low levels of biotic damage. Density of red spruce seedlings was low within gaps and adjacent canopy sites. Balsam fir seedling density was significantly higher in the canopied areas, whereas birch density was marginally higher in gap areas. There were no significant differences in ages of spruce or fir seedlings growing in gaps and closed canopy areas. Birch seedlings in gaps were older and taller than those under the canopy, indicating low survivorship of birch under the forest canopy. It is likely that this forest will be predominantly composed of balsam fir and birch in the near future.

FACTORS AFFECTING RED SPRUCE REGENERATION IN DECLINING AREAS OF CAMELS HUMP MOUNTAIN, VERMONT

Scarcity of red spruce (Picea rubens Sarg.) seedlings in declining spruce‐fir forests of Camels Hump mountain, Vermont, prompted a study on some contributing factors involved in failure of spruce regeneration. Cones were shorter than those from low elevation red spruce trees from unaffected sites. Seed number in cones collected in declining areas of Camels Hump was low as were seed sizes and weights. Seed germination was at control levels only in good seed years. Capacity of seeds to form seedlings was reduced relative to that of controls, although seedling growth was normal. Coniferous litter contains presumed allelopathic substances leachable by contemporary precipitations that affect seed germination and seedling root development in red spruce, but not in balsam fir. Shield fern contains leachable substances that reduce seed germination and seedling root development in red spruce, but not balsam fir. Roots of red spruce germlings have lower capacity to penetrate through the increased forest duff depths of declining forests than do balsam fir roots. It is anticipated that substantial reproduction of red spruce will not occur in declining montane conifer forests under present conditions.

DESICCATION OR FREEZING? MECHANISMS OF WINTER INJURY TO RED SPRUCE FOLIAGE

Selected branches of red spruce {Picea rubens Sarg.) saplings growing at 900 m in elevation on Camels Hump Mountain, Vermont, were treated with an acrylic polymer antitranspirant (Adkar Cloud Cover) in October 1989. Winter injury was subsequently apparent on first‐year foliage on 1 February 1990. Addition of antitranspirant significantly increased chloroform extractable wax (plus antitranspirant) weight and cuticle (plus antitranspirant) thickness. The treatment reduced cuticular transpiration under laboratory conditions, but did not lessen the severity of visually apparent winter injury. Xylem water potential of damaged and undamaged branches did not differ. Fresh to dry weight ratios revealed a tendency for damaged needles to desiccate rapidly following winter injury. Foliar pigment concentrations were negatively correlated with severity of winter damage. These results suggest that winter desiccation plays a minor role in inducing winter injury to red spruce foliage.

Factors Affecting Red Spruce Regeneration in Delining Areas of Camels Hump Mountain, Vermont

Scarcity of red spruce (Picea rubens Sarg.) seedlings in declining spruce-fir forests of Camels Hump mountain, Vermont, prompted a study on some contributing factors involved in failure of spruce regeneration. Cones were shorter than those from low elevation red spruce trees from unaffected sites. Seed number in cones collected in declining areas of Camels Hump was low as were seed sizes and weights. Seed germination was at control levels only in good seed years. Capacity of seeds to form seedlings was reduced relative to that of controls, although seedling growth was normal. Coniferous litter contains presumed allelopathic substances leachable by contemporary precipitations that affect seed germination and seedling root development in red spruce, but not in balsam fir. Shield fern contains leachable substances that reduce seed germination and seedling root development in red spruce, but not balsam fir. Roots of red spruce germlings have lower capacity to penetrate through the increased forest duff depths of declining forests than do balsam fir roots. It is anticipated that substantial reproduction of red spruce will not occur in declining montane conifer forests under present conditions.

A comparison of foliar wettability of red spruce and balsam fir* growing at high elevation

summaryThe contact angle method was used to determine the wettability of red spruce (Picea rubens Sarg.) and balsam fir [Abies balsamea (L.) Mill.] foliage in subalpine sites (1010–1400 m above sea level) at three locations in northern New England, USA (Camels Hump in Vermont and Mt. Moosilauke and Mt. Washington in New Hampshire).The dependence of contact angle (θ) on foliage age (t, in months) could be expressed in the form θ=θ1+θ2 e−kt. The value of the decay constant (k) ranged from 0.02 to 0.12 (month−1), depending upon location, but was independent of elevation, canopy position, and, in most cases, species. The asymptotic value of the contact angle (θ1) i.e. that approached by very old foliage, did not differ between species at some sites but was greater in fir than in spruce at others. The value of θ1 decreased with elevation in both species and tended to increase with an increase in height within the canopy. The value of the component which affected contact angle variation with age (θ2) was always greater in fir than in spruce, but was unaffected by elevation; in fir, it appeared to increase with height in the canopy. Thus, the estimated value of the initial (t= 0) contact angle (θ1+θ2) was greater in fir, increased with height in the canopy, and decreased with elevation. The overall pattern found was that (1) young foliage of spruce is more wettable than young foliage of fir, but the difference becomes smaller in older age classes; (2) young foliage near the bottom of the canopy is more wettable than near the top; and (3) foliage from a given age class and species is more wettable at higher elevations.The treatment of foliage with xylene to remove epicuticular wax decreased contact angles of fir but increased them in spruce. Scanning electron microscopy revealed that wax removal by xylene did not mimic natural wax removal. Contact angles obtained with acidified water did not vary significantly from those obtained with deionized water.

Spatial and Temporal Distribution of Korscheltellus gracilis Larvae (Lepidoptera: Hepialidae) in the Green Mountains, Vermont

The spatial and temporal larval distributions of the newly recognized potential pest of boreal forests, Korscheltellus gracilis (Grote), are presented. Larvae were collected from 17 of 20 areas in the Green Mountain National Forest, Vermont, and highest densities were at elevations > 1,000 m. On Camels Hump Mountain (Huntington, Vt.), larval density during the summer of 1987 was approximately 440,000 ± 36,000 per hectare. Changes in density between May and August 1987 were not detected. Larvae were clumped in space and most abundant in the upper 9 cm of soil. Data from head capsule measurements suggest at least six instars.

Cytophotometric Differentiation Of HIGH Elevation Spruces: Physiological and Ecological Implications

Red and black spruce and their hybrids can be determined by morphological indices; however, the criteria are somewhat subjective and increasingly difficult to use at higher elevations. Although the chromosome number is identical (2n = 24), red spruce has twice as much nuclear DNA (48 pg) than black spruce (24 pg) and thus the species and their hybrids can also be separated by cytophotometry. This is relevant to spruce decline studies because black spruce is much more resistant to high elevation environmental stresses, both natural and anthropogenic. It also has implications for the effect of climatic changes on the composition of high elevation spruce-fir forests because red spruce can outcompete black spruce under more mesic conditions. Four elevation transects sampling spruce on the east and west sides of Mount Washington (New Hampshire) and Camels Hump (Vermont) and a single transect on the southwest side of Whiteface Mountain (New York) were made to investigate the degree of hybridization and introgression between these two species. A positive correlation was found between increased elevation and increased black spruce genes on Mount Washington and Camels Hump. Pure black spruce was found on Mount Washington from 1356 m to 1582 m. No pure black or red spruce was found on Camels Hump although the proportion of red spruce alleles was significantly greater on Camels Hump. All trees sampled at all elevations on Whiteface Mountain were pure red spruce. Thus the proportion of black spruce alleles in high elevation spruce populations decreases from east to west. This closely parallels the increase in spruce decline which increases from east to west.

Detection of forest change in the Green Mountains of Vermont using Multispectral Scanner data

Abstract This study evaluates the potential of Landsat Multispectral Scanner (MSS) data to monitor long term changes in high-elevation coniferous forests. August 1973 and 1984 MSS data from the Green Mountains of Vermont were used. Following co-registration and standardization of data sets, colour density slices of 0.75 μm and 0·95 μm band difference images were produced. False colour composites using either (a) the 1973 0·65 μm and 0·75 μm band in conjunction with the 0.75 μm band difference data set or (b) the 1973 0·65 μm and 0·95 μm band in conjunction with the 0.95 μm band difference data set, were also produced. These images indicated that major reflectance decreases occurred for the near-infrared bands between 1973 and 1984 for much of the high-elevation forests. This includes the west-facing slope of Camels Hump, an area for which long term records documenting decreases in basal area and inferred biomass are available. It is believed that the reflectance decreases noted for the high-elevation coniferous forests are related to the forest decline process and are associated with reduction in green leaf biomass and/or the increased levels of mortality and higher amounts of dead branches accompanying this reduction in biomass.

A 21‐year record of forest decline on Camels Hump, Vermont, USA

AbstractEcological studies on Camels Hump mountain in northern Vermont document a decline of many forest tree species since 1965. A forest survey in 1986 shows a continued decline in the density, basal area and biomass of red spruce (Picea rubens) and other dominant tree species. The changes occurring between 1983 and 1986 indicate a rapid and continuing reduction in the productivity of the montane forest ecosystem.