Ecosystem response to 15 years of chronic nitrogen additions at the Harvard Forest LTER, Massachusetts, USA

Magill, Alison H.; Aber, John D.; Currie, William S.; Nadelhoffer, Knute J.; Martin, Mary E.; McDowell, William H.; Melillo, Jerry M.; Steudler, Paul A.

doi:10.1016/j.foreco.2004.03.033

Cited by 397 publications

(337 citation statements)

References 55 publications

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“…In theory, N is sequestered from soils by both fungi and bacteria if the C/N ratios of the substrate for decomposition are greater than about 30:1; N is released (N mineralization) by fungi but sequestered by bacteria if the C/N ratios are between 12.5:1 and 30:1; and N is released by both fungi and bacteria if the C/ N ratios are less than about 12.5:1 (Hodge et al 2000). For example, the direct N inputs from N deposition and fertilization to canopy leaves, litterfall, and soil have been reported to increase plant leaf N concentration (Fang et al 2011;Hietz et al 2011;Zak et al 2008) and fine root N content (Magill et al 2004), which has the potential to reduce the C/N ratios of the substrate being decomposed in forest ecosystems, and thus facilitating net microbial N mineralization greatly (Hodge et al 2000;Kaye and Hart 1997).…”

Section: N Mineralizationmentioning

confidence: 99%

Effects of nitrogen deposition and fertilization on N transformations in forest soils: a review

et al. 2015

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Purpose Understanding how process-specific nitrogen (N) transformations in natural forest soils are modified by N deposition and fertilization is critically important to gain mechanistic insights on the links between global N deposition and N enrichment and loss in forest soils. Materials and methods Here we identify the general characteristics and the main mechanisms of N deposition-and fertilization-induced modifications in multiple N transformations, including N immobilization, N mineralization, nitrification (autotrophic nitrification and heterotrophic nitrification), and denitrification, in forest soils by literature survey. Results and discussion Overall, N status, soil C/N ratios, C availability, and soil pH are key factors separately and/or interactively affecting the effects of N deposition and fertilization on forest soil N transformations. In the N-limited stage, N deposition and fertilization can act as a stimulator of N mineralization by removing microbial N limitation and reducing the C/N ratios of the substrate being decomposed. In the Nunlimited stage, N added to forest ecosystems can retard N mineralization, which may primarily be a result of decreased microbial activity due to soil acidification and low C availability. The changes in N mineralization may drive a corresponding change in N immobilization, autotrophic nitrification, and denitrification. Despite the fact that ammonia-oxidizing archaea (AOA) has a higher affinity than ammonia-oxidizers (AOB) for low-concentration ammonia (NH 3 ), low NH 3 availability may still limit the rate of ammonia oxidation (autotrophic nitrification) in acidic forest soils even in the case of high NH 4 + input. Heterotrophic nitrification, however, may be favored if soil C/N ratios and pH decrease with N deposition and fertilization. The responses of denitrification and N 2 O emission to N deposition and fertilization in forests may be nonlinear, with a trend of stimulation in the short term but a decline over time, partly because soil pH has a contrast effect on denitrification capacity and N 2 O emission. Conclusions There are various effects of N deposition and fertilization on forest soil N transformations; thus, their responses to N deposition are still not well characterized and understood. N deposition-and fertilization-induced modifications in soil N transformations have important implications for N enrichment, N loss, and soil acidification in forest ecosystems. In the future, more research is required to investigate on dissimilatory nitrate reduction to ammonium (DNRA) process and link microbial community characteristics and functions of microbial extracellular enzymes with these rate processes in forest soils to narrow the uncertainty in evaluating and predicting ecosystem responses to global N deposition.

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Section: N Mineralizationmentioning

confidence: 99%

Effects of nitrogen deposition and fertilization on N transformations in forest soils: a review

et al. 2015

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“…Based on our findings, these specific changes (i.e., increased N supply or altered composition, both resulting in higher canopy %N) should increase gross C assimilation [and presumably net C sequestration (4, 25)] and surface albedo, both representing negative feedbacks to warming. Similar effects can be expected from anthropogenic N deposition and widespread use of N fertilizers, which also serve to increase canopy %N (26). Conversely, leaf N concentrations in temperate forests are inversely related to mean annual temperature (27) and are driven down by rising CO 2 (6)(7)(8), suggesting that temperature and CO 2 increases could lead to reduced canopy albedo and a positive feedback to warming.…”

Section: Discussionmentioning

confidence: 79%

Canopy nitrogen, carbon assimilation, and albedo in temperate and boreal forests: Functional relations and potential climate feedbacks

Ollinger

Richardson

Martin

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

355

289

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The availability of nitrogen represents a key constraint on carbon cycling in terrestrial ecosystems, and it is largely in this capacity that the role of N in the Earth's climate system has been considered. Despite this, few studies have included continuous variation in plant N status as a driver of broad-scale carbon cycle analyses. This is partly because of uncertainties in how leaf-level physiological relationships scale to whole ecosystems and because methods for regional to continental detection of plant N concentrations have yet to be developed. Here, we show that ecosystem CO 2 uptake capacity in temperate and boreal forests scales directly with whole-canopy N concentrations, mirroring a leaf-level trend that has been observed for woody plants worldwide. We further show that both CO 2 uptake capacity and canopy N concentration are strongly and positively correlated with shortwave surface albedo. These results suggest that N plays an additional, and overlooked, role in the climate system via its influence on vegetation reflectivity and shortwave surface energy exchange. We also demonstrate that much of the spatial variation in canopy N can be detected by using broad-band satellite sensors, offering a means through which these findings can be applied toward improved application of coupled carbon cycle-climate models.nitrogen cycle ͉ climate change ͉ foliar nitrogen ͉ ecosystem-climate feedback ͉ remote sensing T errestrial ecosystems influence the Earth's climate through regulation of mass and energy exchange with the atmosphere. In recent years, much of the focus has been directed toward factors affecting the Ϸ1-to 2-Pg carbon (C) sink that is believed to exist in the terrestrial biosphere (1). Candidate mechanisms include forest regrowth after agricultural abandonment (2) and growth enhancement from nitrogen (N) deposition and/or elevated CO 2 (3, 4). In each case, interactions between C and N play a central role. Observations of N limitations to productivity are widespread (5), and responses to experimental CO 2 fertilization are often restricted by N availability (6-8). Although evidence of an N deposition effect on net C exchange has only recently been documented (4), the importance of N as a regulator of C assimilation is well established through the widely observed relationship between leaf-level photosynthetic capacity (A max ) and foliar N concentrations (9-11). Despite this understanding, few analyses have included continuous variation in plant N status as a driver of C cycle processes at regional to global scales. There are at least 2 reasons for this. First, because evidence for the photosynthesis-foliar N relationship comes predominantly from leaf-level observations, there is uncertainty about whether similar trends occur over whole-plant canopies or whether canopy-level factors such as leaf area index (LAI) become dominant at this scale. Second, although many ecosystem models simulate plant and soil N dynamics, there are no widely available methods for obtaining mapped foliar N estimates over ...

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“…A great number of studies on N deposition have been carried out in Europe and North America, where industrial development occur earliest (Matson et al, 1999;Galloway et al, 2003). Results have shown that in predominately N-limited temperate forests in these regions, the experimental and atmospheric N inputs had dramatically altered ecosystem processes and properties, including forest productivity, soil fertility, species composition, litter decomposition, and N loss from soils to groundwater and atmosphere Kahl et al, 1993;Magill et al, 1996Magill et al, , 2000Magill et al, , 2004Emmett et al, 1998;Fenn et al, 1998;Gundersen, 1998;Gundersen et al, 1998Gundersen et al, , 2006Hall and Matson, 2003).…”

Section: Introductionmentioning

confidence: 99%

Response of Nitrogen Leaching to Nitrogen Deposition in Disturbed and Mature Forests of Southern China

Fang

Yoh

et al. 2009

Pedosphere

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Ecosystem response to 15 years of chronic nitrogen additions at the Harvard Forest LTER, Massachusetts, USA

Cited by 397 publications

References 55 publications

Effects of nitrogen deposition and fertilization on N transformations in forest soils: a review

Effects of nitrogen deposition and fertilization on N transformations in forest soils: a review

Canopy nitrogen, carbon assimilation, and albedo in temperate and boreal forests: Functional relations and potential climate feedbacks

Response of Nitrogen Leaching to Nitrogen Deposition in Disturbed and Mature Forests of Southern China

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