Chronic nitrate additions dramatically increase the export of carbon and nitrogen from northern hardwood ecosystems

Pregitzer, Kurt S.; Zak, Donald R.; Burton, Andrew J.; Ashby, Jennifer A.; MacDonald, Neil W.

doi:10.1023/b:biog.0000025737.29546.fd

Cited by 196 publications

(171 citation statements)

References 53 publications

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“…In accordance with our hypothesis regarding DOC concentration in mineral B horizon, DOC approximately doubled in both sampling years in response to both N treatments, N1 and N2. These findings were in accordance with other reports on the effects of N addition on mineral horizon DOC across a range of ecosystem types (Guggenberger, 1994;Pregitzer et al, 2004). As there were no treatment effects in O horizon leachates, the increased DOC in mineral soil requires an explanation other than increased leaching of DOC from the overlying O horizon.…”

Section: Discussionsupporting

confidence: 92%

“…This finding was in accordance with some lysimeter studies (Currie et al, 1996;Raastad and Mulder, 1999) but stood in contrast to others (Guggenberger, 1994;Pregitzer et al, 2004). The variability in response of DOC to N addition has not been uniformly explained.…”

Section: Discussionsupporting

confidence: 90%

“…In the Harvard Forest experiment in eastern North America, Currie et al (1996) did not find a significant increase in the concentration of DOC in the forest floor after seven years of ammonium nitrate, NH 4 NO 3 , application. Conversely, in mature sugar maple dominated stands, the leaching of DOC through mineral soil increased (more than three times more than the control) and leaching of dissolved organic nitrogen (DON) increased (more than six times more than the control) after the addition of 30 kg NO 3 -N ha −1 yr −1 for eight years (Pregitzer et al, 2004). In the study by Pregitzer et al (2004), the effect of elevated N deposition on leaching of DOC and DON in mineral B horizon was tested experimentally across a gradient of N availability, temperature and N deposition.…”

Section: Introductionmentioning

confidence: 94%

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The impact of four decades of annual nitrogen addition on dissolved organic matter in a boreal forest soil

2013

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Addition of mineral nitrogen (N) can alter the concentration and quality of dissolved organic matter (DOM) in forest soils. The aim of this study was to assess the effect of long-term mineral N addition on soil solution concentration of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in Stråsan experimental forest (Norway spruce) in central Sweden. N was added yearly at two levels of intensity and duration: the N1 treatment represented a lower intensity but a longer duration (43 yr) of N addition than the shorter N2 treatment (24 yr). N additions were terminated in the N2 treatment in 1991. The N treatments began in 1967 when the spruce stands were 9 yr old. Soil solution in the forest floor O, and soil mineral B, horizons were sampled during the growing seasons of 1995 and 2009. Tension and non-tension lysimeters were installed in the O horizon (n = 6), and tension lysimeters were installed in the underlying B horizon (n = 4): soil solution was sampled at two-week intervals. Although tree growth and O horizon carbon (C) and N stock increased in treatments N1 and N2, the concentration of DOC in O horizon leachates was similar in both N treatments and control. This suggests an inhibitory direct effect of N addition on O horizon DOC. Elevated DON and nitrate in O horizon leachates in the ongoing N1 treatment indicated a move towards N saturation. In B horizon leachates, the N1 treatment approximately doubled leachate concentrations of DOC and DON. DON returned to control levels, but DOC remained elevated in B horizon leachates in N2 plots nineteen years after termination of N addition. We propose three possible explanations for the increased DOC in mineral soil: (i) the result of decomposition of a larger amount of root litter, either directly producing DOC or (ii) indirectly via priming of old SOM, and/or (iii) a suppression of extracellular oxidative enzymes

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Section: Discussionsupporting

confidence: 92%

Section: Discussionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 94%

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The impact of four decades of annual nitrogen addition on dissolved organic matter in a boreal forest soil

2013

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“…First, the additional soil C in fertilized plots may reflect larger fluxes of DOC from the forest floor into mineral soil. Some N fertilization studies in the north temperate zone have also observed increased DOC production with N fertilization (Guggenberger 1994;Pregitzer et al 2004). Transport of C from the forest floor via DOC is a well-documented source of C to mineral soil (Baisden 2005;Guggenberger et al 1994).…”

Section: Discussionmentioning

confidence: 99%

Effects of nitrogen additions on above- and belowground carbon dynamics in two tropical forests

et al. 2010

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Anthropogenic nitrogen (N) deposition is increasing rapidly in tropical regions, adding N to ecosystems that often have high background N availability. Tropical forests play an important role in the global carbon (C) cycle, yet the effects of N deposition on C cycling in these ecosystems are poorly understood. We used a field N-fertilization experiment in lower and upper elevation tropical rain forests in Puerto Rico to explore the responses of above-and belowground C pools to N addition. As expected, tree stem growth and litterfall productivity did not respond to N fertilization in either of these Nrich forests, indicating a lack of N limitation to net primary productivity (NPP). In contrast, soil C concentrations increased significantly with N fertilization in both forests, leading to larger C stocks in fertilized plots. However, different soil C pools responded to N fertilization differently. Labile (low density) soil C fractions and live fine roots declined with fertilization, while mineral-associated soil C increased in both forests. Decreased soil CO 2 fluxes in fertilized plots were correlated with smaller labile soil C pools in the lower elevation forest (R 2 = 0.65, p \ 0.05), and with lower live fine root biomass in the upper elevation forest (R 2 = 0.90, p \ 0.05). Our results indicate that soil C storage is sensitive to N deposition in tropical forests, even where plant productivity is not N-limited. The mineral-associated soil C pool has the potential to respond relatively quickly to N additions, and can drive increases in bulk soil C stocks in tropical forests.

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“…It has been hypothesized that increased soil N will stimulate the microbial processing of DOM, resulting in a net decrease in DOC that is available for export to the fluvial network as it is potentially outgassed as CO2 [10], though experiments designed to test this hypothesis have produced conflicting results [111][112][113][114], possibly indicating that N deposition alone is not responsible for changes in DOC [103]. One study points to the significance of nitrogen deposition in bogs, because bogs receive their nutrient supply almost exclusively through atmospheric deposition [114].…”

Section: Atmospheric Chemical Deposition-related Increases In Docmentioning

confidence: 99%

Trends in Levels of Allochthonous Dissolved Organic Carbon in Natural Water: A Review of Potential Mechanisms under a Changing Climate

Pagano

Bida

Kenny

2014

Water

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Over the past several decades, dissolved organic carbon (DOC) in inland natural water systems has been a popular research topic to a variety of scientific disciplines. Part of the attention has been due to observed changes in DOC concentrations in many of the water systems of the Northern Hemisphere. Shifts in DOC levels, and changes in its composition, are of concern due to its significance in aquatic ecosystem functioning and its potential and realized negative effects on waters that might be treated for drinking purposes. While it may not be possible to establish sound cause and effect relationships using a limited number of drivers, through long-term DOC monitoring studies and a variety of laboratory/field experiments, several explanations for increasing DOC trends have been proposed, including two key mechanisms: decreased atmospheric acid deposition and the increasing impact of climate change agents. The purpose of this review is three-fold: to outline frequently discussed conceptual mechanisms used to explain DOC increases (especially under a changing climate), to discuss the structure of DOC and the impact of higher levels of DOC on drinking water resources, and to provide renewed/sustained interest in DOC research that can encourage interdisciplinary collaboration. Understanding the cycling of carbon from terrestrial ecosystems into natural waters is necessary in the face of a variable OPEN ACCESSWater 2014, 6 2863 and changing climate, as climate change-related mechanisms may become increasingly responsible for variations in the inputs of allochthonous DOC concentrations in water.

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Chronic nitrate additions dramatically increase the export of carbon and nitrogen from northern hardwood ecosystems

Cited by 196 publications

References 53 publications

The impact of four decades of annual nitrogen addition on dissolved organic matter in a boreal forest soil

The impact of four decades of annual nitrogen addition on dissolved organic matter in a boreal forest soil

Effects of nitrogen additions on above- and belowground carbon dynamics in two tropical forests

Trends in Levels of Allochthonous Dissolved Organic Carbon in Natural Water: A Review of Potential Mechanisms under a Changing Climate

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