Breaks in the Cycle: Dissolved Organic Nitrogen in Terrestrial Ecosystems

Neff, Jason C.; Chapin, Frederic; Vitousek, Peter M.

doi:10.2307/3868065

Cited by 58 publications

(80 citation statements)

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“…Under high N availability conditions, isotopically depleted N is preferentially lost from the ecosystem through the processes of NH 3 volatilization, denitrification and leaching of NO 3 − , which results in an enrichment of soil N pools in 15 N and subsequent increases in leaf δ 15 N. Conversely, plants growing under low N availability conditions are likely to depend on mycorrhizal fungi for N acquisition than at high N availability, plant N obtained via mycorrhhizal fungi is depleted in 15 N [35], [36]. The observed increase in plant and soil δ 15 N with decreasing MAP suggests the arid and semi-arid regions are more open in terms of their N cycling relative to those that are more humid [5], with higher N losses relative to turnover [2].…”

Section: Discussionmentioning

confidence: 99%

Variation in the Stable Carbon and Nitrogen Isotope Composition of Plants and Soil along a Precipitation Gradient in Northern China

et al. 2012

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Water availability is the most influential factor affecting plant carbon (δ 13C) and nitrogen (δ 15N) isotope composition in arid and semi-arid environments. However, there are potential differences among locations and/or species in the sensitivity of plant δ 13C and δ 15N to variation in precipitation, which are important for using stable isotope signatures to extract paleo-vegetation and paleo-climate information. We measured δ 13C and δ 15N of plant and soil organic matter (SOM) samples collected from 64 locations across a precipitation gradient with an isotherm in northern China. δ 13C and δ 15N for both C3 and C4 plants decreased significantly with increasing mean annual precipitation (MAP). The sensitivity of δ 13C to MAP in C3 plants (-0.6±0.07‰/100 mm) was twice as high as that in C4 plants (−0.3±0.08‰/100 mm). Species differences in the sensitivity of plant δ 13C and δ 15N to MAP were not observed among three main dominant plants. SOM became depleted in 13C with increasing MAP, while no significant correlations existed between δ 15N of SOM and MAP. We conclude that water availability is the primary environmental factor controlling the variability of plant δ 13C and δ 15N and soil δ 13C in the studied arid and semi-arid regions. Carbon isotope composition is useful for tracing environmental precipitation changes. Plant nitrogen isotope composition can reflect relative openness of ecosystem nitrogen cycling.

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Section: Discussionmentioning

confidence: 99%

Variation in the Stable Carbon and Nitrogen Isotope Composition of Plants and Soil along a Precipitation Gradient in Northern China

et al. 2012

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“…The anthropogenic reactive N emission has increased from 15 Tg N a −1 in 1860 to 165 Tg N a −1 in early 1990 s, and more that 70% of the reactive N deposited back to the terrestrial and aquatic ecosystems [2]. The current global atmospheric deposition of N is approximately 25 to 40 Tg N a −1 [3] and is expected to double in the next 25 years [4]. N deposition, as well as increasing concentration of carbon dioxide and ongoing land use/land cover change, has been the well documented issues of global change, altering the biogeochemistry of ecosystems [5].…”

Section: Introductionmentioning

confidence: 99%

Sinks for Inorganic Nitrogen Deposition in Forest Ecosystems with Low and High Nitrogen Deposition in China

Sheng

Fang

et al. 2014

PLoS ONE

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We added the stable isotope 15N in the form of (15NH4)2SO4 and K15NO3 to forest ecosystems in eastern China under two different N deposition levels to study the fate of the different forms of deposited N. Prior to the addition of the 15N tracers, the natural 15N abundance ranging from −3.4‰ to +10.9‰ in the forest under heavy N deposition at Dinghushan (DHS), and from −3.92‰ to +7.25‰ in the forest under light N deposition at Daxinganling (DXAL). Four months after the tracer application, the total 15N recovery from the major ecosystem compartments ranged from 55.3% to 90.5%. The total 15N recoveries were similar under the (15NH4)2SO4 tracer treatment in both two forest ecosystems, whereas the total 15N recovery was significantly lower in the subtropical forest ecosystem at DHS than in the boreal forest ecosystem at DXAL under the K15NO3 tracer treatment. The 15N assimilated into the tree biomass represented only 8.8% to 33.7% of the 15N added to the forest ecosystems. In both of the tracer application treatments, more 15N was recovered from the tree biomass in the subtropical forest ecosystem at DHS than the boreal forest ecosystem at DXAL. The amount of 15N assimilated into tree biomass was greater under the K15NO3 tracer treatment than that of the (15NH4)2SO4 treatment in both forest ecosystems. This study suggests that, although less N was immobilized in the forest ecosystems under more intensive N deposition conditions, forest ecosystems in China strongly retain N deposition, even in areas under heavy N deposition intensity or in ecosystems undergoing spring freezing and thawing melts. Compared to ammonium deposition, deposited nitrate is released from the forest ecosystem more easily. However, nitrate deposition could be retained mostly in the plant N pool, which might lead to more C sequestration in these ecosystems.

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“…For example, it has been suggested that DON plays an important role in terrestrial N cycling (Neff et al 2003). For example, it has been suggested that DON plays an important role in terrestrial N cycling (Neff et al 2003).…”

Section: Litter Leaching Experimentsmentioning

confidence: 99%

The Ecology of Energy and Nutrient Fluxes in Hemlock Forests Invaded by Hemlock Woolly Adelgid

Stadler

Müller

Orwig

2006

Ecology

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The hemlock woolly adelgid (HWA, Adelges tsugae Annand) is currently causing a severe decline in vitality and survival of eastern hemlock in North American forests. We analyzed the effects of light HWA infestation on vertical energy and nutrient fluxes from the canopy to the forest floor. Canopy throughfall, litter lysimeters, and laboratory litter microcosms were used to examine the effects of HWA-affected and unaffected throughfall on litter type, leachate, and litter chemistry. Early in the season adelgid infestation caused higher dissolved organic carbon (DOC; +24.6%), dissolved organic nitrogen (DON; +28.5%), and K (+39.3%) fluxes and lower inorganic nitrogen fluxes (-39.8%) in throughfall and in adjacent litter solutions collected beneath infested compared to uninfested trees. Needle litter collected beneath uninfested hemlock had significantly lower N concentrations compared to needles collected beneath infested trees, while no difference in N concentrations was found in birch litter. Bacteria were significantly more abundant on hemlock and birch litter beneath infested trees, while yeasts and filamentous fungi showed no consistent response to HWA throughfall. Litter microcosms showed that less DOC was leaching from birch than from hemlock needles when exposed to HWA throughfall. Overall, NH4-N and DON leachate concentrations were higher from birch than from hemlock litter. Thus, HWA-affected throughfall leads to qualitative and quantitative differences in nitrogen export from the litter layer. The N concentration of hemlock litter did not change with time, but the N concentration in birch litter increased significantly during the course of the experiment, especially when HWA-affected throughfall was applied. We suggest a nonlinear conceptual model for the temporal and vertical transition of energy and nutrient fluxes relative to progressing HWA infestation from a pure hemlock to a birch/maple-dominated forest. Progressive needle loss and changes in needle chemistry are likely to produce a humped-shaped DOC curve, while N fluxes initially decrease as infestation continues but rise eventually with hemlock decline and immigration of hardwood species. These findings suggest that it is necessary to understand the biology and specific physiological/trophic effects of exotic pests on their hosts and associated ecosystem processes in order to decipher the temporal dynamics, direction of change, and functional consequences.

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Breaks in the Cycle: Dissolved Organic Nitrogen in Terrestrial Ecosystems

Cited by 58 publications

References 0 publications

Variation in the Stable Carbon and Nitrogen Isotope Composition of Plants and Soil along a Precipitation Gradient in Northern China

Variation in the Stable Carbon and Nitrogen Isotope Composition of Plants and Soil along a Precipitation Gradient in Northern China

Sinks for Inorganic Nitrogen Deposition in Forest Ecosystems with Low and High Nitrogen Deposition in China

The Ecology of Energy and Nutrient Fluxes in Hemlock Forests Invaded by Hemlock Woolly Adelgid

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