Effects of intensive harvesting on nutrient capitals of three forest types in New England

Effects of whole-tree clearcutting are being studied in three major forest types in the northeastern United States: a spruce-fir forest in central Maine, a northern hardwood forest in New Hampshire, and a central hardwood forest in Connecticut. At each site we sampled total and extractable nutrient capitals, inputs and outputs of nutrient ions in precipitation and streamflow, nutrient removals in harvested products, and nutrient accumulation in regrowth. Depending upon location, combined losses of nutrients in harvested products and increased leaching to streams were in the ranges of 374–558 kg ha⁻¹ for Ca, 135–253 kg ha⁻¹ for K, 50–65 kg ha⁻¹ for Mg, 248–379 kg ha⁻¹ for N, and 19–54 kg ha⁻¹ for P. Opportunities for replacing these losses over the next rotation are best for N. Data on inputs in precipitation versus outputs in streamflow indicate that, once effects of harvest subside, most N in precipitation will stay within the forest. By contrast, Ca shows a net output of 8–15 kg ha⁻¹ year⁻¹ from uncut watersheds, and the added leaching losses due to harvest may have a serious impact on Ca capital. This is especially the case for the Connecticut site, where total site capital for Ca is only about 4000 kg ha⁻¹.     

The influence of storm characteristics on sulfate in precipitation

The effects of storm dynamics on precipitation chemistry were examined using an atmospheric budget for SO₄ ^? . One hundred storms occurring between 1975 and 1978 at Hubbard Brook Experimental Forest in New Hampshire were used as test data. Concentrations of major ions were usually greater in convective storms than in continuous or layer storms. For example the geometric mean concentrations of SO₄ ^? in convective and continuous storms were 4.1 and 1.1 mg L^?1, respectively. Higher SO₄ ^? concentrations also occurred when surface wind directions were south or southwest. The summer maximum in convective activity along with the seasonal dependence of surface wind directions and the seasonal atmospheric chemistry cycle can account for the summer maximum in SO₄ ^? concentrations observed in the northeastern United States.     

Input-Output Budgets of Inorganic Nitrogen for 24 Forest Watersheds in the Northeastern United States: A Review

Input-output budgets for dissolved inorganic nitrogen (DIN) are summarized for 24 small watersheds at 15 locations in the northeasternUnited States. The study watersheds are completely forested, free of recent physical disturbances, and span a geographical region bounded by West Virginia on the south and west, and Maine on the north and east. Total N budgets are not presented; however, fluxes of inorganic N in precipitation and streamwater dominate inputs and outputs of N at these watersheds. The range in inputs of DIN in wet-only precipitation from nearby National Atmospheric Deposition Program (NADP) sites was 2.7 to 8.1 kg N ha^-1 yr^-1 (mean = 6.4 kg N ha^-1 yr^-1; median = 7.0 kg N ha^-1 yr^-1). Outputs of DIN in streamwater ranged from 0.1 to 5.7 kg N ha^-1 yr^-1 (mean = 2.0 kg N ha^-1 yr^-1; median = 1.7 kg N ha^-1 yr^-1). Precipitation inputs of DIN exceeded outputs in streamwater at all watersheds, with net retention of DIN ranging from 1.2 to 7.3 kg N ha^-1 yr^-1 (mean = 4.4 kg N ha^-1 yr^-1; median = 4.6 kg N ha^-1 yr^-1). Outputs of DIN in streamwater were predominantly NO₃-N (mean = 89%; median = 94%). Wet deposition of DIN was not significantly related to DIN outputs in streamwater for these watersheds. Watershed characteristics such as hydrology, vegetation type, and land-use history affect DIN losses and may mask any relationship between inputs and outputs. Consequently, these factors need to be included in the development of indices and simulation models for predicting 'nitrogen saturation' and other ecological processes.     

Analysis of Nitrogen Dynamics in the Lye Brook Wilderness Area,Vermont, USA

Nitrogen (N) deposition and its impact on terrestrial and aquatic ecosystems is a concern facing federal land managers at the Lye Brook Wilderness in Vermont and other protected aras throughout the northeastern United States. In this study, we compared N production in soils with N concentrations and outputs in leachates to determine how forest cover types differ in regulating N losses. Also, precipitation inputs and modeled estimates of streamwater outputs were used to calculate a watershed N budget. Most ammonium and nitrate were produced in organic soils with deciduous cover. Softwood stands had low net nitrification rates and minimal N leaching. A comparison of watershed inputs and outputs showed a net gain in total dissolved N (5.5 kg ha^-1 yr^-1) due to an accumulation of dissolved inorganic N. The Lye Brook Wilderness ecosystem has N budgets similar to other forested ecosystems in the region, and appears to be assimilating the accumulating N. However seasonal losses of nitrate observed in mineral soils and streamwater may be early warnings of the initial stages of N saturation.     

Use of Stable Isotope Ratios for Evaluating Sulfur Sources and Losses at the Hubbard Brook Experimental Forest

Water, Air, &; Soil Pollution - Anthropogenic S emissions have been declining in eastern North America since the early 1970s. Declines in atmospheric S deposition have resulted in decreases in...     

Growth decline in red spruce and balsam fir relative to natural processes

Average annual growth of 3,001 red spruce (Picea rubens Sarg.) trees on plots randomly located across northern New England and upstate New York shows a regionally consistent decline starting soon after 1960. Depending on location, basal-area increment in 1980 was 13 to 40% less than in the peak growth year around 1960. The growth decline occurs in all size and age classes and is independent of elevation. Balsam fir (Abies balsamea (L.) Mill.) also shows a growth decline, but the start varies by tree age. The growth decline in both species is explainable at least in part by natural growth processes, complicating the task of evaluating the effects of atmospheric deposition.     

Acid pulses from snowmelt at acidic cone pond,New Hampshire

A study was undertaken to examine whether ‘acid pulses’ from snowmelt created permanent changes in a pond's chemistry. Water samples were collected from clearwater acidic Cone Pond in the White Mountain National Forest, New Hampshire. The pond, inlet, and outlet were intensively sampled throughout winter and early spring 1983–84. Thaws brought more H⁺ into upper waters of the pond, but most was gone within a week. In contrast, SO₄ ^2? and Al showed dilution with increased streamflow into the pond, and NO₃ ^? was only detected in ice, slush, and surface waters. Bottom waters were anoxic throughout the winter and had pH 6.0 compared to 4.7 for most of the water column. Alkalinity at the bottom rose from 0 in November 1983 to 190 μeq L^?1 in April 1984. Between November and April the pond gained Al but lost SO₄ ^2? and H⁺. Most of the Al gain came after ice-out when loading through the inlet increased, but during the final snowmelt a temporary increase in Al concentration was also seen throughout the water column.     

The detection of a population of submillimeter-bright, strongly lensed galaxies

Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valuable at submillimeter wavelengths for the study of the statistical and individual properties of dusty star-forming galaxies. However, the identification of gravitational lenses is often time-intensive, involving the sifting of large volumes of imaging or spectroscopic data to find few candidates. We used early data from the Herschel Astrophysical Terahertz Large Area Survey to demonstrate that wide-area submillimeter surveys can simply and easily detect strong gravitational lensing events, with close to 100% efficiency.