Emission of Nitrogen Gas, Nitrous Oxide, and Carbon Dioxide on Rehydration of Dry Feathermosses

Startsev, N. A.; Lieffers, Victor J.

doi:10.2136/sssaj2004.0376

Cited by 4 publications

(5 citation statements)

References 26 publications

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“…An important finding in terms of the N balance of the ecosystem was that, during the first 4 years of the experiment, 15 N losses from the moss layer were not compensated for by a corresponding increase in recovery rates in any other compartment. These losses accounted for more than 30% of the total 15 N applied and suggest that N losses from the moss layer in gaseous forms are very likely (Startsev and Lieffers, 2007 ; for a further discussion of this aspect see paragraph ‘Leaching losses and putative flows’ below). In contrast, the largely constant recovery rates found from 2010 onwards point to a conservative N cycling with marginal 15 N losses from the N pool of the ecosystem in the long term (Tye et al, 2005 ).…”

Section: Discussionmentioning

confidence: 99%

“…In contrast to the observed accumulation of N, the first 4 years of the experiment (2007–2010) also exhibited a considerable loss of 15 N. Tracer mass balances suggest that this loss was attributable to a leak of N from the moss layer in gaseous forms (Startsev and Lieffers, 2007 ). High N losses from bryophyte layers due to denitrification have been found for different species and ecosystems, and increase with increasing humidity (e.g., with water saturation of the moss layer after precipitation events), temperature, and N deposition (Laverman et al, 2000 ; Opelt and Berg, 2004 ; Lenhart et al, 2015 ).…”

Section: Discussionmentioning

confidence: 99%

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Bryophytes and Organic layers Control Uptake of Airborne Nitrogen in Low-N Environments

et al. 2017

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The effects of atmospheric nitrogen (N) deposition on ecosystem functioning largely depend on the retention of N in different ecosystem compartments, but accumulation and partitioning processes have rarely been quantified in long-term field experiments. In the present study we analysed for the first time decadal-scale flows and allocation patterns of N in a heathland ecosystem that has been subject to airborne N inputs over decades. Using a long-term 15N tracer experiment, we quantified N retention and flows to and between ecosystem compartments (above-ground/below-ground vascular biomass, moss layer, soil horizons, leachate). After 9 years, about 60% of the added 15N-tracer remained in the N cycle of the ecosystem. The moss layer proved to be a crucial link between incoming N and its allocation to different ecosystem compartments (in terms of a short-term capture, but long-term release function). However, about 50% of the 15N captured and released by the moss layer was not compensated for by a corresponding increase in recovery rates in any other compartment, probably due to denitrification losses from the moss layer in the case of water saturation after rain events. The O-horizon proved to be the most important long-term sink for added 15N, as reflected by an increase in recovery rates from 18 to 40% within 8 years. Less than 2.1% of 15N were recovered in the podzol-B-horizon, suggesting that only negligible amounts of N were withdrawn from the N cycle of the ecosystem. Moreover, 15N recovery was low in the dwarf shrub above-ground biomass (<3.9% after 9 years) and in the leachate (about 0.03% within 1 year), indicating still conservative N cycles of the ecosystem, even after decades of N inputs beyond critical load thresholds. The continuous accumulation of reactive forms of airborne N suggests that critical load-estimates need to account for cumulative effects of N additions into ecosystems.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Bryophytes and Organic layers Control Uptake of Airborne Nitrogen in Low-N Environments

et al. 2017

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“…Once hydrolyzed, the elevated pH following urea hydrolysis (Malhi et al 1992) likely created conditions that promoted some volatilization of NH 3 from substrates with inherently high pH or low buffering capability (Fan and Mackenzie 1993). Volatilization of NH 3 or denitrification (Startsev and Lieffers 2007) may explain the 19% of added N that could not be accounted for in either the substrate or leachate in the growth chamber experiment.…”

Section: Discussionmentioning

confidence: 99%

“…It is also possible that fracturing of the substrate during handling might have increased water channeling through the litter, thereby make the leaching less effective during the larger watering events. Continuously moist conditions may have increased the nutrients immobilization rate in the substrate (Compton and Boone 2002) or promoted denitrification (Startsev and Lieffers 2007) as under those conditions N transfer to the leachate was low.…”

Section: Discussionmentioning

confidence: 99%

N-transfer through aspen litter and feather moss layers after fertilization with ammonium nitrate and urea

et al. 2008

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When fertilizer is broadcast in boreal forest stands, the applied nutrients must pass through a thick layer of either feather moss or leaf litter which covers the forest floor. In a growth chamber experiment we tested the transfer of N through living feather moss or aspen litter when fertilized with urea ((NH 2 ) 2 CO) or NH 4 NO 3 at a rate of 100 kg ha −1 and under different watering regimes. When these organic substrates were frequently watered to excess they allowed the highest transfer of nutrients through, although 72% of the applied fertilizer was captured in the substrates. In a field experiment we also fertilized moss and aspen litter with urea ((NH 2 ) 2 CO) or NH 4 NO 3 at a more operationally relevant rate of 330 kg ha −1 . We captured the NO 3 − or NH 4 + by ion exchange resin at the substrate-mineral soil interface. In contrast to the growth chamber experiment, this fertilizer rate killed the moss and there was no detectable increase in nutrient levels in the aspen litter or feather moss layers. Instead, the urea was more likely transferred into the mineral soil; mineral soil of the urea treatment had 1.6 times as much extractable N compared to the NH 4 NO 3 treatment. This difference between the growth chamber and field studies was attributed to observed fertilizerdamage to the living moss and possibly damage to the litter microflora due to the higher rate of fertilization in the field. In addition, the early and substantial rainfall after fertilization in the field experiment produced conditions for rapid leaching of N through the organic layers into the mineral soil. In the field, only 8% of the urea-N that was applied was captured by the ion exchange resin, while 34% was captured in for the NH 4 NO 3 fertilization. Thus, the conditions for rapid leaching in the field moved much of the N in the form of urea through the organic layers and into the mineral soil before it was hydrolyzed.

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“…Accordingly, these locations varied in the amount of plant debris input and its quality. Startsev and Lieffers [68] showed that decomposing litter generally trapped in the bryophyte layer contributed to the total CO 2 production, and provided bryophytes with a source of easily available nutrients and carbohydrates. In our study, the total amount of plant debris input was greater in the southern treed areas where trees were bigger and more productive, which was also an important factor in southern treed peat plateaus.…”

Section: Quantitative Relationships Between Nce and Er And Climate Vamentioning

confidence: 99%

Surface CO2 Exchange Dynamics across a Climatic Gradient in McKenzie Valley: Effect of Landforms, Climate and Permafrost

Startsev

Bhatti

Jassal

2016

Forests

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Abstract:Northern regions are experiencing considerable climate change affecting the state of permafrost, peat accumulation rates, and the large pool of carbon (C) stored in soil, thereby emphasizing the importance of monitoring surface C fluxes in different landform sites along a climate gradient. We studied surface net C exchange (NCE) and ecosystem respiration (ER) across different landforms (upland, peat plateau, collapse scar) in mid-boreal to high subarctic ecoregions in the Mackenzie Valley of northwestern Canada for three years. NCE and ER were measured using automatic CO 2 chambers (ADC, Bioscientific LTD., Herts, England), and soil respiration (SR) was measured with solid state infrared CO 2 sensors (Carbocaps, Vaisala, Vantaa, Finland) using the concentration gradient technique. Both NCE and ER were primarily controlled by soil temperature in the upper horizons. In upland forest locations, ER varied from 583 to 214 g C·m −2 ·year −1 from mid-boreal to high subarctic zones, respectively. For the bog and peat plateau areas, ER was less than half that at the upland locations. Of SR, nearly 75% was generated in the upper 5 cm layer composed of live bryophytes and actively decomposing fibric material. Our results suggest that for the upland and bog locations, ER significantly exceeded NCE. Bryophyte NCE was greatest in continuously waterlogged collapsed areas and was negligible in other locations. Overall, upland forest sites were sources of CO 2 (from 64 g·C·m −2 ·year −1 in the high subarctic to 588 g C·m −2 ·year −1 in mid-boreal zone); collapsed areas were sinks of C, especially in high subarctic (from 27 g· C· m −2 year −1 in mid-boreal to 86 g·C·m −2 ·year −1 in high subarctic) and peat plateaus were minor sources (from 153 g· C· m −2 · year −1 in mid-boreal to 6 g·C·m −2 ·year −1 in high subarctic). The results are important in understanding how different landforms are responding to climate change and would be useful in modeling the effect of future climate change on the soil C balance in the northern regions.

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Emission of Nitrogen Gas, Nitrous Oxide, and Carbon Dioxide on Rehydration of Dry Feathermosses

Cited by 4 publications

References 26 publications

Bryophytes and Organic layers Control Uptake of Airborne Nitrogen in Low-N Environments

Bryophytes and Organic layers Control Uptake of Airborne Nitrogen in Low-N Environments

N-transfer through aspen litter and feather moss layers after fertilization with ammonium nitrate and urea

Surface CO2 Exchange Dynamics across a Climatic Gradient in McKenzie Valley: Effect of Landforms, Climate and Permafrost

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