Estimates of critical acid loads and exceedances for forest soils across the conterminous United States

McNulty, Steven G.; Cohen, Erika; Myers, Jennifer A. Moore; Sullivan, Timothy J.; Li, Harbin

doi:10.1016/j.envpol.2007.05.025

Cited by 72 publications

(71 citation statements)

References 19 publications

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“…Using the green line value determined for Joyce Kilmer, North Carolina, the critical load for acidity for the overstory and herb layer was 7 kg N ha -1 yr -1 . Th is is consistent with calculations made for this region by McNulty et al (2007), who made coarse estimates for critical loads for total acidity across the United States. Based on those calculations, the contribution of N to those critical loads for acidity is ~10 kg ha -1 yr -1 .…”

Section: Critical Loads Estimatessupporting

confidence: 89%

Assessment of Nitrogen deposition effects and empirical critical loads of Nitrogen for ecoregions of the United States

Pardo¹,

Robin-Abbott²,

Driscoll³

2011

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Human activity in the last century has led to a substantial increase in nitrogen (N) emissions and deposition. This N deposition has reached a level that has caused or is likely to cause alterations to the structure and function of many ecosystems across the United States. One approach for quantifying the level of pollution that would be harmful to ecosystems is the critical loads approach. The critical load is defi ned as the level of a pollutant below which no detrimental ecological effect occurs over the long term according to present knowledge.The objective of this project was to synthesize current research relating atmospheric N deposition to effects on terrestrial and aquatic ecosystems in the United States and to identify empirical critical loads for atmospheric N deposition. The receptors that we evaluated included freshwater diatoms, mycorrhizal fungi and other soil microbes, lichens, herbaceous plants, shrubs, and trees. The main responses reported fell into two categories: (1) biogeochemical, and (2) individual species, population, and community responses.The range of critical loads for nutrient N reported for U.S. ecoregions, inland surface waters, and freshwater wetlands is 1 to 39 kg N ha -1 y -1. This broad range spans the range of N deposition observed over most of the country. The empirical critical loads for N tend to increase in the following sequence for different life forms: diatoms, lichens and bryophytes, mycorrhizal fungi, herbaceous plants and shrubs, trees.The critical loads approach is an ecosystem assessment tool with great potential to simplify complex scientifi c information and effectively communicate with the policy community and the public. This synthesis represents the fi rst comprehensive assessment of empirical critical loads of N for ecoregions across the United States.

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Section: Critical Loads Estimatessupporting

confidence: 89%

Assessment of Nitrogen deposition effects and empirical critical loads of Nitrogen for ecoregions of the United States

Pardo¹,

Robin-Abbott²,

Driscoll³

2011

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“…Different ecosystems have different critical loads due to their different buffering capacities or sensitivities to acid deposition. Sulphur and nitrogen species contribute to acid deposition (Whepdale et al, 1997) while the deposition of base cations (Ca 2+ , Mg 2+ , K + and Na + ) increases the alkalinity of the surface and thus the ecosystems' buffering capacity (Watmough et al, 2005;Skeffington, 2006;McNaulty et al, 2007). To assess the effects of acid deposition on sensitive ecosystems, the atmospheric deposition of both acidic species and base cations needs to be estimated with sufficient accuracy (Environment Canada, 2005).…”

Section: Introductionmentioning

confidence: 99%

Characterization of the size-segregated water-soluble inorganic ions at eight Canadian rural sites

et al. 2008

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Abstract. Size-segregated water-soluble inorganic ions, including particulate sulphate (SO 2− 4 ), nitrate (NO − 3 ), ammonium (NH + 4 ), chloride (Cl − ), and base cations (K + , Na + , Mg 2+ , Ca 2+ ), were measured using a Micro-Orifice Uniform Deposit Impactor (MOUDI) during fourteen short-term field campaigns at eight locations in both polluted and remote regions of eastern and central Canada. The size distributions of SO 2− 4 and NH + 4 were unimodal, peaking at 0.3-0.6 µm in diameter, during most of the campaigns, although a bimodal distribution was found during one campaign and a trimodal distribution was found during another campaign made at a coastal site. SO 2− 4 peaked at slightly larger sizes in the cold seasons (0.5-0.6 µm) compared to the hot seasons (0.3-0.4 µm) due to the higher relative humidity in the cold seasons. The size distributions of NO − 3 were unimodal, peaking at 4.0-7.0 µm during the warm-season campaigns, and bimodal, with one peak at 0.3-0.6 µm and another at 4-7 µm during the cold-season campaigns. A unimodal size distribution, peaking at 4-6 µm, was found for Cl − , Na + , Mg 2+ , and Ca 2+ during approximately half of the campaigns and a bimodal distribution, with one peak at 2 µm and the other at 6 µm, was found during the rest of the campaigns. For K + , a bimodal distribution, with one peak at 0.3 µm and the other at 4 µm, was observed during most of the campaigns. Seasonal contrasts in the size-distribution profiles suggest that emission sources and air mass origins were the major factors controlling the size distributions of the primary aerosols while meteorological conditions were more important for the secondary aerosols.The dependence of the particle acidity on the particle size from the nucleation mode to the accumulation mode was not consistent from site to site or from season to season. Particles in the accumulation mode were more acidic than those in the Correspondence to: L. Zhang (leiming.zhang@ec.gc.ca) nucleation mode when submicron particles were in the state of strong acidity; however, when submicron particles were neutral or weakly acidic, particles in the nucleation mode could sometimes be more acidic. The inconsistency of the dependence of the particle acidity on the particle size should have been caused by the different emission sources of all the related species and the different meteorological conditions during the different campaigns. The results presented here at least partially explain the controversial phenomenon found in previous studies on this topic.

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“…Study watersheds were selected based on the following criteria: (a) they exceeded critical loads of acidic deposition (McNulty et al, 2007;McDonnell et al, 2014) and (b) they were included in a USDA Forest Service, regional synoptic sampling effort to identify streams in 1st order catchments with low ANC (W. A. Jackson, unpublished). The three watersheds are from west to east, North River (NR, 35°latitude, 84°longitude; Cherokee National Forest, Tennessee), Santeetlah Creek (SC, 35°latitude, 84°longitude; Nantahala National Forest, North Carolina), and the North Fork of the French Broad (FB, 35°latitude, 82°longitude; Pisgah National Forest, North Carolina) (Fig.…”

Section: Site Selectionmentioning

confidence: 99%

“…For example, some high elevation streams in the eastern U.S. continue to show signs of chronic to episodic acidity . Modeled patterns of SO 4 + nitrate (NO 3 ) deposition and ecosystem critical loads, exceeded the capacity of forest soils in approximately 17% of forested sites across the conterminous United States (McNulty et al, 2007) and numerous aquatic ecosystems in the southern Appalachians (McDonnell et al, 2014).…”

mentioning

confidence: 99%

High elevation watersheds in the southern Appalachians: Indicators of sensitivity to acidic deposition and the potential for restoration through liming

Knoepp

Vose

Jackson

et al. 2016

Forest Ecology and Management

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elevation watersheds in the southern Appalachians: Indicators of sensitivity to acidic deposition and the potential for restoration through liming" (2016 . We studied three 3rd order watersheds (North River in Cherokee National Forest, Santeetlah Creek in Nantahala National Forest, and North Fork of the French Broad in Pisgah National Forest) and selected four to six 1st order catchments within each watershed to represent a gradient in elevation (849-1526 m) and a range in acidic stream ANC values (11-50 leq L À1 ). Our objectives were to (1) identify biotic, physical and chemical catchment parameters that could be used as indices of stream ANC, pH and Ca:Al molar ratios and (2) estimate the lime required to restore catchments from the effects of excess acidity and increase base cation availability. We quantified each catchment's biotic, physical, and chemical characteristics and collected stream, O-horizon, and mineral soil samples for chemical analysis seasonally for one year. Using repeated measures analysis, we examined variability in stream chemistry and catchment characteristics; we used a nested split-plot design to identify catchment characteristics that were correlated with stream chemistry. Watersheds differed significantly and the catchments sampled provided a wide range of stream chemical, biotic, physical and chemical characteristics. Variability in stream ANC, pH, and Ca:Al molar ratio were significantly correlated with catchment vegetation characteristics (basal area, tree height, and tree diameter) as well as O-horizon nitrogen and aluminum concentrations. Total soil carbon and calcium (an indicator of parent material), were significant covariates for stream ANC, pH and Ca:Al molar ratios. Lime requirement estimates did not differ among watersheds but this data will help select catchments for future restoration and lime application studies. Not surprisingly, this work found many vegetation and chemical characteristics that were useful indicators of stream acidity. However, some expected relationships such as concentrations of mineral soil extractable Ca and SO 4 were not significant. This suggests that an extensive test of these indicators across the southern Appalachians will be required to identify high elevation forested catchments that would benefit from restoration activities.Published by Elsevier B.V.

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Estimates of critical acid loads and exceedances for forest soils across the conterminous United States

Cited by 72 publications

References 19 publications

Assessment of Nitrogen deposition effects and empirical critical loads of Nitrogen for ecoregions of the United States

Assessment of Nitrogen deposition effects and empirical critical loads of Nitrogen for ecoregions of the United States

Characterization of the size-segregated water-soluble inorganic ions at eight Canadian rural sites

High elevation watersheds in the southern Appalachians: Indicators of sensitivity to acidic deposition and the potential for restoration through liming

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