Introduction to the NITREX and EXMAN projects

Wright, Richard F.; Rasmussen, L.

doi:10.1016/s0378-1127(97)00120-5

Cited by 139 publications

(60 citation statements)

References 29 publications

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“…In contrast to co-ordinated regional studies such as the NITREX study in Europe (Wright and Van Breemen, 1995;Wright and Rasmussen, 1998), experimental research on nitrogen saturation in the U.S. has not generated a regionalscale evaluation of ecosystem susceptibility to nitrogen saturation (Aber et al, 1998). In particular, some complex questions remain unanswered, such as what is the time course to nitrogen saturation for forested catchments receiving the www.elsevier.com/locate/foreco Forest Ecology and Management 251 (2007) [217][218][219][220][221][222][223][224][225][226][227][228][229][230] moderate levels of nitrogen deposition in the northeastern U.S. (in contrast to higher levels of nitrogen deposition observed in Europe).…”

Section: Introductionmentioning

confidence: 99%

Natural abundance 15N in soil and litter across a nitrate-output gradient in New Hampshire

Pardo

Hemond

Montoya

et al. 2007

Forest Ecology and Management

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Section: Introductionmentioning

confidence: 99%

Natural abundance 15N in soil and litter across a nitrate-output gradient in New Hampshire

Pardo

Hemond

Montoya

et al. 2007

Forest Ecology and Management

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“…Other regional assessments of N cycling across gradients in deposition, such as the NITREX study in Europe (Wright and van Breemen, 1995;Wright and Rasmussen, 1998), have also generated useful data for interpreting broad-scale patterns in ecosystem response to N deposition. For example, this study found forest floor N status and C:N to be an important determinant of ecosystem response to N inputs Gundersen et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

Regional patterns in foliar 15N across a gradient of nitrogen deposition in the northeastern US

Pardo

McNulty

Boggs

et al. 2007

Environmental Pollution

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Recent studies have demonstrated that natural abundance 15 N can be a useful tool for assessing nitrogen saturation, because as nitrification and nitrate loss increase, d15 N of foliage and soil also increases. We measured foliar d 15 N at 11 high-elevation spruce-fir stands along an N deposition gradient in 1987e1988 and at seven paired northern hardwood and spruce-fir stands in 1999. In 1999, foliar d 15 N increased from À5.2 to À0.7& with increasing N deposition from Maine to NY. Foliar d 15 N decreased between 1987e1988 and 1999, while foliar %N increased and foliar C:N decreased at most sites. Foliar d 15 N was strongly correlated with N deposition, and was also positively correlated with net nitrification potential and negatively correlated with soil C:N ratio. Although the increase in foliar %N is consistent with a progression towards N saturation, other results of this study suggest that, in 1999, these stands were further from N saturation than in 1987e1988. Published by Elsevier Ltd.

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“…Since that time, a number of coordinated studies in Europe under the NITREX and EXMAN programs (Wright and van Breemen 1995;Wright and Rasmussen 1998) and individual experiments in the US (for example, Christ and others 1995;others 1996, 1997;McNulty and others 1996;Peterjohn and others 1996;Fenn and others 1998;Norton and Fernandez 1999) have provided much of the data necessary for an increased under-standing of the process of N saturation. In a recent article (Aber and others 1998), the results of European and North American studies were summarized into an inclusive theory where N saturation is defined as a series of nonlinear changes in key ecosystem processes in response to elevated nitrogen inputs.…”

Section: Introductionmentioning

confidence: 99%

Long-Term Nitrogen Additions and Nitrogen Saturation in Two Temperate Forests

et al. 2000

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This article reports responses of two different forest ecosystems to 9 years (1988-96) of chronic nitrogen (N) additions at the Harvard Forest, Petersham, Massachusetts. Ammonium nitrate (NH 4 NO 3 ) was applied to a pine plantation and a native deciduous broad-leaved (hardwood) forest in six equal monthly doses (May-September) at four rates: control (no fertilizer addition), low N (5 g N m -2 y -1 ), high N (15 g N m -2 y -1 ), and low N ϩ sulfur (5 g N m -2 y -1 plus 7.4 g S m -2 y -1 ). Measurements were made of net N mineralization, net nitrification, N retention, wood production, foliar N content and litter production, soil C and N content, and concentrations of dissolved organic carbon (DOC) and nitrogen (DON) in soil water. In the pine stand, nitrate losses were measured after the first year of additions (1989) in the high N plot and increased again in 1995 and 1996. The hardwood stand showed no significant increases in nitrate leaching until 1995 (high N only), with further increases in 1996. Overall N retention efficiency (percentage of added N retained) over the 9-year period was 97-100% in the control and low N plots of both stands, 96% in the hardwood high N plot, and 85% in the pine high N plot. Storage in aboveground biomass, fine roots, and soil extractable pools accounted for only 16-32% of the added N retained in the amended plots, suggesting that the one major unmeasured pool, soil organic matter, contains the remaining 68-84%. Short-term redistribution of 15 N tracer at natural abundance levels showed similar division between plant and soil pools. Direct measurements of changes in total soil C and N pools were inconclusive due to high variation in both stands. Woody biomass production increased in the hardwood high N plot but was significantly reduced in the pine high N plot, relative to controls. A drought-induced increase in foliar litterfall in the pine stand in 1995 is one possible factor leading to a measured increase in N mineralization, nitrification, and nitrate loss in the pine high N plot in 1996.

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Introduction to the NITREX and EXMAN projects

Cited by 139 publications

References 29 publications

Natural abundance 15N in soil and litter across a nitrate-output gradient in New Hampshire

Natural abundance 15N in soil and litter across a nitrate-output gradient in New Hampshire

Regional patterns in foliar 15N across a gradient of nitrogen deposition in the northeastern US

Long-Term Nitrogen Additions and Nitrogen Saturation in Two Temperate Forests

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