N2 Fixation in Feather Mosses is a Sensitive Indicator of N Deposition in Boreal Forests

Abstract. The productivity of boreal forests is considered to be limited by low nitrogen (N) availability. Increased atmospheric N deposition has altered the functioning and N cycling of these N-sensitive ecosystems. The most important components of N pools and fluxes were measured in a boreal Scots pine stand in Hyytiälä, Southern Finland. The measurement at the site allowed direct estimations of nutrient pools in the soil and biomass, inputs from the atmosphere and outputs as drainage flow and gaseous losses from two micro-catchments. N was accumulating to the system with a rate of 7 kg N ha−1 yr−1. Nitrogen input as atmospheric deposition was 7.4 kg N ha−1 yr−1. Dry deposition and organic N in wet deposition contributed over half of the input in deposition. Total outputs were 0.4 kg N ha−1 yr−1, the most important outputs being N2O emission to the atmosphere and organic N flux in drainage flow. Nitrogen uptake and retranslocation were as important sources of N for plant growth. Most of the uptaken N originated from decomposition of organic matter, and the fraction of N that could originate directly from deposition was about 30%. In conclusion, atmospheric N deposition fertilizes the site considerably.

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Too Much of a Good Thing? Inorganic Nitrogen (N) Inhibits Moss-Associated N2 Fixation But Organic N Can Promote It

10.21203/rs.3.rs-1022519/v1 ◽

2021 ◽

Author(s):

Yinliu Wang ◽

Signe Lett ◽

Kathrin Rousk

Keyword(s):

Boreal Forests ◽

Inorganic Nitrogen ◽

N Deposition ◽

Ecosystem Functions ◽

Organic N ◽

Inorganic N ◽

Atmospheric N Deposition ◽

Moss Species ◽

The Impact ◽

N Additions

Abstract Moss-associated nitrogen (N2) fixation is one of the main inputs of new N in pristine ecosystems that receive low amounts of atmospheric N deposition. Previous studies have shown that N2 fixation is inhibited by inorganic N (IN) inputs, but if N2 fixation in mosses is similarly affected by organic N (ON) remains unknown. Here, we assessed N2 fixation in two dominant mosses in boreal forests (Pleurozium schreberi and Sphagnum capillifolium) in response to different levels of N, simulating realistic (up to 4 kg N ha−1 yr−1) and extreme N deposition rates in pristine ecosystems (up to 20 kg N ha−1 yr−1) of IN (NH4NO3) and ON (alanine and urea). We also assessed if N2 fixation can recover from the N additions. In the realistic scenario, N2 fixation was inhibited by increasing NH4NO3 additions in P. schreberi but not in S. capillifolium, and alanine and urea stimulated N2 fixation in both moss species. In contrast, in the extreme N additions, increasing N inputs inhibited N2 fixation in both moss species and all N forms. Nitrogen fixation was more sensitive to N inputs in P. schreberi than in S. capillifolium and was higher in the recovery phase after the realistic compared to the extreme N additions. These results demonstrate that N2 fixation in mosses is less sensitive to organic than inorganic N inputs and highlight the importance of considering different N forms and species-specific responses when estimating the impact of N inputs on ecosystem functions such as moss-associated N2 fixation.

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Effect of chronic ammonium nitrate addition on the ectomycorrhizal community in a black spruce stand1This article is one of a selection of papers from the 7th International Conference on Disturbance Dynamics in Boreal Forests.

Canadian Journal of Forest Research ◽

10.1139/x11-176 ◽

2012 ◽

Vol 42 (7) ◽

pp. 1204-1212 ◽

Cited By ~ 6

Author(s):

Sergio Rossi ◽

Adam Bordeleau ◽

Daniel Houle ◽

Hubert Morin

Keyword(s):

Ammonium Nitrate ◽

Boreal Forests ◽

Black Spruce ◽

N Deposition ◽

Fungal Species ◽

Root Tip ◽

Soil Conditions ◽

Root Tips ◽

Atmospheric N Deposition ◽

Host Trees

Observed modifications of ectomycorrhizal (ECM) communities have been connected to the increased N depositions of the 20th century. Because of their narrow niche width, small disturbances of soil conditions can produce greater effects on the fungal species than on their host trees. This study investigated the ECM community in a black spruce ( Picea mariana (Mill.) BSP) stand subjected to long-term additions of 9 and 30 kg N·ha–1·year–1 of ammonium nitrate, representing 3 and 10 times the atmospheric N deposition at the site, respectively. Root tip vitality and ECM presence were detected on samples collected from the organic horizon and ECM were classified into morphotypes according to their morphological and anatomical characters. In the control, 80.6% of the root tips were vital, 76.5% of them showing ECM colonization. Higher root tip vitality and mycorrhization were observed in the treated plots. Forty-one morphotypes were identified, most of them detected at the higher N inputs. Results diverging from the expectations of a reduction in ECM presence and diversity could be related to a higher growth rate of the trees following fertilization. The repeated application of small N doses could have been a better imitation of natural inputs from atmospheric deposition and could have provided more reliable responses of ECM to treatment.

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N2 fixation associated with the bryophyte layer is suppressed by low levels of nitrogen deposition in boreal forests

The Science of The Total Environment ◽

10.1016/j.scitotenv.2018.10.364 ◽

2019 ◽

Vol 653 ◽

pp. 995-1004 ◽

Cited By ~ 4

Author(s):

Maija Salemaa ◽

Antti-Jussi Lindroos ◽

Päivi Merilä ◽

Raisa Mäkipää ◽

Aino Smolander

Keyword(s):

Nitrogen Deposition ◽

N2 Fixation ◽

Boreal Forests ◽

Low Levels

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Soil oxygen within boreal forests across an age gradient

Canadian Journal of Soil Science ◽

10.4141/s05-004 ◽

2006 ◽

Vol 86 (1) ◽

pp. 1-9 ◽

Cited By ~ 21

Author(s):

N. Fenton ◽

S. Légaré ◽

Y. Bergeron ◽

D. Paré

Keyword(s):

Water Table ◽

Boreal Forests ◽

Forest Floor ◽

Black Spruce ◽

Methodological Issue ◽

Mineral Soil ◽

Forest Region ◽

Feather Mosses ◽

Spruce Stands ◽

Potential Factors

Globally, soil anoxia and water table rise play a role in the development of peatlands from forests. Cited causes have included a diversity of internal and external mechanisms, including Sphagnum and feather mosses, hardpan development, and peatland expansion. The objectives of this study were to examine water table depth in black spruce stands of the Clay Belt of Quebec and Ontario, and to associate changes with potential stand scale causal factors (primarily biological). A methodological issue, the link between oxygen zone and water table, was also addressed. Within stands less than 100 yr post-fire, oxygen zone and water table position were only loosely related, and no other potential factors were significantly correlated. Across a chronosequence of stands, while oxygen zone thickness in the soil profile was relatively constant, its position relative to the mineral soil changed, as it rose from the mineral soil into the forest floor. Forest floor thickness was the dominant explanatory factor in oxygen zone position, suggesting that in these forests other postulated mechanisms are less important. At the landscape level, the movement of the oxygen zone into the forest floor has important consequences for the long-term productivity of this intensively exploited forest region. Key words: Water table, black spruce, paludification, forest floor, Clay Belt, Sphagnum

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Atmospheric deposition of nutrients and excess N formation in the North Atlantic

Biogeosciences ◽

10.5194/bg-7-777-2010 ◽

2010 ◽

Vol 7 (2) ◽

pp. 777-793 ◽

Cited By ~ 35

Author(s):

L. M. Zamora ◽

A. Landolfi ◽

A. Oschlies ◽

D. A. Hansell ◽

H. Dietze ◽

...

Keyword(s):

Atmospheric Deposition ◽

North Atlantic ◽

N2 Fixation ◽

Transport Model ◽

N Deposition ◽

Atmospheric N Deposition ◽

N Accumulation ◽

The North ◽

The North Atlantic ◽

Main Thermocline

Abstract. Anthropogenic emissions of nitrogen (N) to the atmosphere have been strongly increasing during the last century, leading to greater atmospheric N deposition to the oceans. The North Atlantic subtropical gyre (NASTG) is particularly impacted. Here, upwind sources of anthropogenic N from North American and European sources have raised atmospheric N deposition to rates comparable with N2 fixation in the gyre. However, the biogeochemical fate of the deposited N is unclear because there is no detectable accumulation in the surface waters. Most likely, deposited N accumulates in the main thermocline instead, where there is a globally unique pool of N in excess of the canonical Redfield ratio of 16N:1 phosphorus (P). To investigate this depth zone as a sink for atmospheric N, we used a biogeochemical ocean transport model and year 2000 nutrient deposition data. We examined the maximum effects of three mechanisms that may transport excess N from the ocean surface to the main thermocline: physical transport, preferential P remineralization of sinking particles, and nutrient uptake and export by phytoplankton at higher than Redfield N:P ratios. Our results indicate that atmospheric deposition may contribute 13–19% of the annual excess N input to the main thermocline. Modeled nutrient distributions in the NASTG were comparable to observations only when non-Redfield dynamics were invoked. Preferential P remineralization could not produce realistic results on its own; if it is an important contributor to ocean biogeochemistry, it must co-occur with N2 fixation. The results suggest that: 1) the main thermocline is an important sink for anthropogenic N deposition, 2) non-Redfield surface dynamics determine the biogeochemical fate of atmospherically deposited nutrients, and 3) atmospheric N accumulation in the main thermocline has long term impacts on surface ocean biology.

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Nitrogen balance of a boreal Scots pine forest

Biogeosciences ◽

10.5194/bg-10-1083-2013 ◽

2013 ◽

Vol 10 (2) ◽

pp. 1083-1095 ◽

Cited By ~ 40

Author(s):

J. F. J. Korhonen ◽

M. Pihlatie ◽

J. Pumpanen ◽

H. Aaltonen ◽

P. Hari ◽

...

Keyword(s):

Scots Pine ◽

Boreal Forests ◽

N2o Emission ◽

N Deposition ◽

Organic N ◽

N Availability ◽

N Saturation ◽

Atmospheric N Deposition ◽

Drainage Flow ◽

Nutrient Pools

Abstract. The productivity of boreal forests is considered to be limited by low nitrogen (N) availability. Increased atmospheric N deposition has altered the functioning and N cycling of these N-sensitive ecosystems by increasing the availability of reactive nitrogen. The most important components of N pools and fluxes were measured in a boreal Scots pine stand in Hyytiälä, Southern Finland. The measurements at the site allowed direct estimations of nutrient pools in the soil and biomass, inputs from the atmosphere and outputs as drainage flow and gaseous losses from two micro-catchments. N was accumulating in the system, mainly in woody biomass, at a rate of 7 kg N ha−1 yr−1. Nitrogen input as atmospheric deposition was 7.4 kg N ha−1 yr−1. Dry deposition and organic N in wet deposition contributed over half of the inputs in deposition. Total outputs were 0.4 kg N ha−1 yr−1, the most important outputs being N2O emission to the atmosphere and organic N flux in drainage flow. Nitrogen uptake and retranslocation were equally important sources of N for plant growth. Most of the assimilated N originated from decomposition of organic matter, and the fraction of N that could originate directly from deposition was about 30%. In conclusion, atmospheric N deposition fertilizes the site considerably, but there are no signs of N saturation. Further research is needed to estimate soil N2 fluxes (emission and fixation), which may amount up to several kg N ha−1 yr−1.

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Atmospheric deposition of nutrients and excess N formation in the North Atlantic

Biogeosciences Discussions ◽

10.5194/bgd-6-9849-2009 ◽

2009 ◽

Vol 6 (5) ◽

pp. 9849-9889 ◽

Cited By ~ 2

Author(s):

L. M. Zamora ◽

A. Landolfi ◽

A. Oschlies ◽

D. Hansell ◽

H. Dietze ◽

...

Keyword(s):

Atmospheric Deposition ◽

North Atlantic ◽

N2 Fixation ◽

Transport Model ◽

N Deposition ◽

Atmospheric N Deposition ◽

N Accumulation ◽

The North ◽

The North Atlantic ◽

Main Thermocline

Abstract. Anthropogenic emissions of nitrogen (N) to the atmosphere have been strongly increasing during the last century, leading to greater atmospheric N deposition to the oceans. The North Atlantic subtropical gyre (NASTG) is particularly impacted. Here, upwind sources of anthropogenic N from North American and European sources have raised atmospheric N deposition to rates comparable with N2 fixation in the gyre. However, the biogeochemical fate of the deposited N is unclear because there is no detectable accumulation in the surface waters. Most likely, deposited N accumulates in the main thermocline instead, where there is a globally unique pool of N in excess of the canonical Redfield ratio of 16 N:1 phosphorus (P). To investigate this depth zone as a sink for atmospheric N, we used a biogeochemical ocean transport model and year 2000 nutrient deposition data. We examined the maximum effects of three mechanisms that may transport excess N from the ocean surface to the main thermocline: physical transport, preferential P remineralization of sinking particles, and nutrient uptake and export by phytoplankton at higher than Redfield N:P ratios. Our results indicate that atmospheric deposition may contribute 13–19% of the annual excess N input to the main thermocline. Modeled nutrient distributions in the NASTG were comparable to observations only when non-Redfield dynamics were invoked. Preferential P remineralization could not produce realistic results on its own; if it is an important contributor to ocean biogeochemistry, it must co-occur with N2 fixation. The results suggest that: 1) the main thermocline is an important sink for anthropogenic N deposition, 2) non-Redfield surface dynamics determine the biogeochemical fate of atmospherically deposited nutrients, and 3) atmospheric N accumulation in the main thermocline has long term impacts on surface ocean biology.

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