Eric K. Miller

Lead Migration in Forest Soils: Response to Changing Atmospheric Inputs

Decreased use of leaded gasoline has caused a rapid reduction in atmospheric Pb deposition to terrestrial and aquatic ecosystems of the northeastern United States. In forest soils, the response to decreased Pb deposition has been more rapid than was anticipated based on previous studies of Pb cycling in forested ecosystems. To better understand the observed ecosystem response, we estimated both short-(25 y) and long-term (190 y) time series of the regional average atmospheric Pb concentrations in precipitation, cloudwater, and air. We combined these time series with modeled wet and dry deposition velocities to calculate the time-dependent Pb flux at different elevations in montane forests of the northeastern United States

Nitrogen deposition, distribution and cycling in a subalpine spruce-fir forest in the Adirondacks, New York, USA

Nitrogen inputs, fluxes, internal generation and consumption, and outputs were monitored in a subalpine spruce-fir forest at approximately 1000-m elevation on Whiteface Mountain in the Adirondacks of New York, USA. Nitrogen in precipitation, cloudwater and dry deposition was collected on an event basis and quantified as an input. Throughfall, stemflow, litterfall and soil water were measured to determine fluxes within the forest. Nitrogen mineralization in the forest floor was estimated to determine internal sources of available N. Lower mineral horizon soil water was used to estimate output from the ecosystem. Vegetation and soil N pools were determined.During four years of continuous monitoring, an average of 16 kg N ha−1 yr−1 was delivered to the forest canopy as precipitation, cloudwater and dry deposition from the atmosphere. Approximately 30% of the input was retained by the canopy. Canopy retention is likely the result of both foliar uptake and immobilization by bark, foliage and microorganisms. Approximately 40 kg of N was made available within the forest floor from mineralization of organic matter. Virtually all the available ammonium (mineralized plus input from throughfall) is utilized in the forest floor, either by microorganisms or through uptake by vegetation. The most abundant N component of soil water solutions leaving the system was nitrate. Net ecosystem fluxes indicate accumulation of both ammonium and nitrate. There is a small net loss of organic N from the ecosystem. Some nitrate leaves the bottom of the B horizon throughout the year. Comparisons with other temperate coniferous sites and examination of the ecosystem N mass balance indicate that N use efficiency is less at our site, which suggests that the site is not severely limited by N.

Atmospheric deposition to forests along an elevational gradient at Whiteface Mountain, NY, U.S.A.

Abstract Atmospheric deposition rates of pollutants are known to be greater at high elevations than at low elavations in the same region, but the pattern of the deposition rate increase with elevation has not been established. This study was conducted to estimate nutrient and pollutant transfer rates from the atmosphere to forests along an elevational gradient at a site in the Adirondack Mountains of NY, U.S.A. Widely used models of cloud droplet, dry aerosol and gas phase SO 2 and HNO 3 deposition processes were modified for use in this application. An extensive data set describing the elevational variation in forest canopy composition and structure and microclimatic variables was assembled from measurements made by us during seven years of research activities at Whiteface Mountain, NY. Model estimates of total atmospheric deposition of S and N increased by factors of 4 and 5, respectively, over the elevational range 600–1275 m. Steep gradients in wind speed and cloud immersion frequency contributed to a nearly exponential increase in ion deposition by cloud water interception, which was responsible for most of the increase in total ion deposition rates with elevation. An additional factor contributing to increased deposition rates at high elevations was an increasing percentage of total leaf area attributable to coniferous vegetation, which is more effective at scavenging aerosol particles and cloud droplets than broad-leaved vegetation. Dry deposition contributed 13% and cloud water 61% of the 29.5 kg N ha −1 yr −1 estimated total N deposition at 1275 m elevation as opposed to 22 and 5% of the 7 kg N ha −1 yr −1 total N deposition estimated for surrounding low-elevation (600 m) forests. The dry deposition component accounted for 5% and the cloud water component 64% of the estimated 31 kg S ha −1 yr −1 total deposition at 1275 m elevation, in comparison with a 21% dry and 5% cloud contribution to the 8.4 kg S ha −1 yr −1 estimated deposition to low-elevation forests.

MAJOR-ELEMENT CYCLING IN A HIGH-ELEVATION ADIRONDACK FOREST: PATTERNS AND CHANGES, 1986-1996

High-elevation forests in the northeastern United States have received large amounts of atmospheric deposition of pollutants that may alter natural element cycling and retention rates in a variety of ways. This study examined atmospheric deposition of N, S, and base cations (Ca2+, Mg2+, K+, Na+), and their impact on element cycling, in a high-elevation forest on Whiteface Mountain, New York, USA. Ten years of element cycling data (1986–1996) showed that at our study site (1050-m elevation) precipitation and cloud water contributed most of the atmospheric deposition relative to dry deposition. Input–output budgets revealed a net retention of N in this forest. In contrast, annual variations in outputs of K+ were roughly balanced by atmospheric inputs. Potassium output seemed to be strongly related to and dependent on K+ inputs. There was a net loss of Ca2+, Mg2+, and SO42− from the site. Calcium and SO42− outputs were related to one another and to water inputs to the forest. Net loss of 2.9 kg S·ha−1·yr−1 w...

A zooplankton-N:P-ratio indicator for lakes

We develop the conceptual and empirical basis for a multi-level ecosystem indicator for lakes. The ratio of total N to total P in lake water is influenced or regulated by a variety of ecosystem processes operating at several organizational levels and spatial scales: atmospheric, terrestrial watershed, lake water, and aquatic community. The character of the pelagic zooplankton assemblage is shown to be well correlated with lake water N:P ratio, with species assemblages arrayed along the N:P gradient in accordance with resource supply theory. Features of specific zooplankton assemblages or deviations from expected assemblages can provide information useful for lake managers, such as the efficiency of pollutant transfer and biomagnification of toxins, loss of cool-water refuge areas, degree of zooplanktivory and food web simplification related to changes in fisheries, and assemblage changes due to anthropogenic acidification. Evaluation of the influence of watershed land use, forest cover and vegetation type, atmospheric deposition, and basin hydrology on the supply of N and P to lake ecosystems provides a means to couple changes in the terrestrial environment to potential changes in aquatic ecosystems. Deviations of lake water N:P values from expected values based on analysis of watershed and lake basin characteristics, including values inferred from appropriate diatom microfossil deposits, can provide an independent validation and baseline reference for assessing the extent and type of disturbance. Therefore, the N:P ratio of lake water can serve as a potentially useful and inexpensively obtained proxy measure for assessing changes or shifts in the biological and nutrient status of lakes.

Boreal Forests and Global Change

Boreal forests form Earths largest terrestrial biome. They are rich in ecosystem and landscape diversity, though characterized by relatively few plant species, as compared to other forested regions. The long term viability and sustainability of boreal forests is influenced by many factors. They are subject to interruptions at intervals by large-scale natural disturbances, and increasingly by human activities. Boreal ecosystem development is typically a slow process; hence rapid changes in the global environment may invoke complex responses. Many industrial nations border, or lie within, boreal regions, deriving much of their economic wealth and culture from the forests. The response of boreal forests to changes in the global environment - whether caused by direct human activity or by indirect changes such as the anticipated changes in climate - are therefore of considerable international interest, both for their policy implications and their scientific challenges. This book which contains almost 50 peer-reviewed papers from a world-wide group of experts assembled under the auspices of IBFRA, the International Boreal Forest Research Association, covers topics which will stimulate further research and the development of constructive policies for improved management and conservation of global boreal forest resources.

Elemental concentrations in fresh snowfall across a regional transect in the northeastern U.S.: Apparent sources and contribution to acidity

Fresh snowfall was collected on the surface of 8 lakes across a 350 km west-east transect from northeastern New York state to the coast of Maine after a single storm. In addition, every snowfall event during the winter of 1993 was collected on a single lake near the center of the transect. Across the transect, midwestern sources appear to dominate Pb and Cd concentrations, while Sb appears to be derived from midwestern sources as well as local and/or industrial East Coast sources. In all samples, the highest Na, Cl and Mg concentrations reflect a marine influence, but at some transect sites roadspray aerosol appears to contribute to Na and Cl concentrations. The regional pattern of Ca, K, Mn and Sr concentrations and Mn/Sr ratios indicate that woodsmoke may be an important winter source of these elements at some sites. In all samples, H+ is strongly correlated with NO3− (R2 = 0.97) and mean NO3−/SO42− molar ratios of 6.4 for transect samples, and 4.7 for temporal samples, are higher than mean NO3−/SO42− reported for other precipitation studies in the same region. The contribution of NO3− to the snowpack greatly exceeds that of SO42−, and may be a major source of acidity in aquatic ecosystems during snowmelt.

MERGANSER: an empirical model to predict fish and loon mercury in New England lakes

MERGANSER (MERcury Geo-spatial AssessmeNtS for the New England Region) is an empirical least-squares multiple regression model using mercury (Hg) deposition and readily obtainable lake and watershed features to predict fish (fillet) and common loon (blood) Hg in New England lakes. We modeled lakes larger than 8 ha (4404 lakes), using 3470 fish (12 species) and 253 loon Hg concentrations from 420 lakes. MERGANSER predictor variables included Hg deposition, watershed alkalinity, percent wetlands, percent forest canopy, percent agriculture, drainage area, population density, mean annual air temperature, and watershed slope. The model returns fish or loon Hg for user-entered species and fish length. MERGANSER explained 63% of the variance in fish and loon Hg concentrations. MERGANSER predicted that 32-cm smallmouth bass had a median Hg concentration of 0.53 μg g(-1) (root-mean-square error 0.27 μg g(-1)) and exceeded EPAs recommended fish Hg criterion of 0.3 μg g(-1) in 90% of New England lakes. Common loon had a median Hg concentration of 1.07 μg g(-1) and was in the moderate or higher risk category of >1 μg g(-1) Hg in 58% of New England lakes. MERGANSER can be applied to target fish advisories to specific unmonitored lakes, and for scenario evaluation, such as the effect of changes in Hg deposition, land use, or warmer climate on fish and loon mercury.

Effect of nitrogen and light on nutrient concentrations and associated physiological responses in birch and fir seedlings

We grew seedlings of two co-occurring high elevation tree species in controlled light and nitrogen (N) environments to examine the effect on foliar N and P concentrations and the resulting correlation with photosynthesis and growth. Foliar N concentrations in both heart-leaf paper birch (Betula cordifolia) and balsam fir (Abies balsamea) seedlings were greater in low light treatments than in high light treatments. P concentrations, however, were lower in birch and fir foliage grown in low light than in high light. N-availability had no effect on foliar N in birch but tended to increase N concentration in fir needles at all but 100% ambient light. N-availability had no effect on P concentration in fir seedlings, but high N decreased foliar P in birch. There was a positive relationship between foliar N-concentration (mg g−1) and mass-based maximum photosynthetic rate (Asat) in birch seedlings and a corresponding growth response to increased N-availability (suggesting N-limitation). Fir photosynthesis exhibited a positive correlation up to 22 mg g−1 – N and a negative correlation above that point, suggesting that high N concentrations may be detrimental to photosynthesis in the fir seedlings. There was no significant effect of N-treatment on growth.