SOIL MICROBIAL FEEDBACKS TO CLIMATE WARMING AND ATMOSPHERIC N DEPOSITION

Nitric oxide (NO) is an important trace gas and regulator of atmospheric photochemistry. Theory suggests moist soils optimize NO emissions, whereas wet or dry soils constrain them. In drylands, however, NO emissions can be greatest in dry soils and when dry soils are rewet. To understand how aridity and vegetation interact to generate this pattern, we measured NO fluxes in a California grassland, where we manipulated vegetation cover and the length of the dry season and measured [δ15-N]NO and [δ18-O]NO following rewetting with15N-labeled substrates. Plant N uptake reduced NO emissions by limiting N availability. In the absence of plants, soil N pools increased and NO emissions more than doubled. In dry soils, NO-producing substrates concentrated in hydrologically disconnected microsites. Upon rewetting, these concentrated N pools underwent rapid abiotic reaction, producing large NO pulses. Biological processes did not substantially contribute to the initial NO pulse but governed NO emissions within 24 h postwetting. Plants acted as an N sink, limiting NO emissions under optimal soil moisture. When soils were dry, however, the shutdown in plant N uptake, along with the activation of chemical mechanisms and the resuscitation of soil microbial processes upon rewetting, governed N loss. Aridity and vegetation interact to maintain a leaky N cycle during periods when plant N uptake is low, and hydrologically disconnected soils favor both microbial and abiotic NO-producing mechanisms. Under increasing rates of atmospheric N deposition and intensifying droughts, NO gas evasion may become an increasingly important pathway for ecosystem N loss in drylands.

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Management scheme influence and nitrogen addition effects on soil CO2, CH4, and N2O fluxes in a Moso bamboo plantation

Forest Ecosystems ◽

10.1186/s40663-021-00285-0 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Junbo Zhang ◽

Quan Li ◽

Jianhua Lv ◽

Changhui Peng ◽

Zhikang Gu ◽

...

Keyword(s):

Global Warming ◽

Microbial Biomass Carbon ◽

Ghg Emissions ◽

Nitrogen Addition ◽

N Deposition ◽

Moso Bamboo ◽

Atmospheric N Deposition ◽

Soil Microbial ◽

Management Scheme ◽

Set Up

Abstract Background It is still not clear whether the effects of N deposition on soil greenhouse gas (GHG) emissions are influenced by plantation management schemes. A field experiment was conducted to investigate the effects of conventional management (CM) versus intensive management (IM), in combination with simulated N deposition levels of control (ambient N deposition), 30 kg N·ha− 1·year− 1 (N30, ambient + 30 kg N·ha− 1·year− 1), 60 kg N·ha− 1·year− 1 (N60, ambient + 60 kg N·ha− 1·year− 1), or 90 kg N·ha− 1·year− 1 (N90, ambient + 90 kg N·ha− 1·year− 1) on soil CO2, CH4, and N2O fluxes. For this, 24 plots were set up in a Moso bamboo (Phyllostachys edulis) plantation from January 2013 to December 2015. Gas samples were collected monthly from January 2015 to December 2015. Results Compared with CM, IM significantly increased soil CO2 emissions and their temperature sensitivity (Q10) but had no significant effects on soil CH4 uptake or N2O emissions. In the CM plots, N30 and N60 significantly increased soil CO2 emissions, while N60 and N90 significantly increased soil N2O emissions. In the IM plots, N30 and N60 significantly increased soil CO2 and N2O emissions, while N60 and N90 significantly decreased soil CH4 uptake. Overall, in both CM and IM plots, N30 and N60 significantly increased global warming potentials, whereas N90 did not significantly affect global warming potential. However, N addition significantly decreased the Q10 value of soil CO2 emissions under IM but not under CM. Soil microbial biomass carbon was significantly and positively correlated with soil CO2 and N2O emissions but significantly and negatively correlated with soil CH4 uptake. Conclusion Our results indicate that management scheme effects should be considered when assessing the effect of atmospheric N deposition on GHG emissions in bamboo plantations.

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Microbial respiration per unit microbial biomass depends on soil litter carbon-to-nitrogen ratio

Biogeosciences Discussions ◽

10.5194/bgd-11-15037-2014 ◽

2014 ◽

Vol 11 (10) ◽

pp. 15037-15051 ◽

Cited By ~ 5

Author(s):

M. Spohn

Keyword(s):

Microbial Biomass ◽

Microbial Respiration ◽

N Deposition ◽

Microbial Biomass C ◽

Atmospheric N Deposition ◽

Central Process ◽

Soil Microbial ◽

C Cycle ◽

Nitrogen Ratio ◽

Litter Nitrogen

Abstract. Soil microbial respiration is a central process in the terrestrial carbon (C) cycle. In this study I tested the effect of the carbon-to-nitrogen (C : N) ratio of soil litter layers on microbial respiration in absolute terms and per unit microbial biomass C. For this purpose, a global dataset on microbial respiration per unit microbial biomass C – termed the metabolic quotient (qCO2) – was compiled form literature data. It was found that the qCO2 in the soil litter layers was positively correlated with the litter C : N ratio and negatively related with the litter nitrogen (N) concentration. The positive relation between qCO2 and litter C : N ratio resulted from an increase in respiration with the C : N ratio in combination with no significant effect of the litter C : N ratio on the soil microbial biomass C concentration. The results suggest that soil microorganisms respire more C both in absolute terms and per unit microbial biomass C when decomposing N-poor substrate. Thus, the findings indicate that atmospheric N deposition, leading to decreased litter C : N ratios, might decrease microbial respiration in soils.

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Fertilizing riparian forests: nutrient repletion across ecotones with trophic rewilding

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2017.0439 ◽

2018 ◽

Vol 373 (1761) ◽

pp. 20170439 ◽

Cited By ~ 6

Author(s):

Joseph K. Bump

Keyword(s):

Climate Warming ◽

Terrestrial Ecosystems ◽

N Deposition ◽

Riparian Forests ◽

Resource Subsidies ◽

Atmospheric N Deposition ◽

Flux Approximation ◽

Limiting Nutrient ◽

Moose Population

Trophic rewilding maintains that large mammals are functionally important to resource subsidies and nutrient repletion, yet this prediction is understudied. Here, I report on the potential magnitude and variability of nitrogen that moose populations move from aquatic to terrestrial ecosystems. My aim is to provide justified approximations of the role of moose in the flux of a limiting nutrient across ecotones and to illustrate how this role is linked to wolf predation and climate warming. Using Isle Royale and northeastern Minnesota, USA as contrasting focal systems, I found that the long-term annual N gain for riparian forests likely ranges from 1 to 10 kg N ha –1 yr –1 , depending on the heterogeneity of moose movements. For these systems, this range is equivalent to approximately 4–30% of net annual N mineralization, approximately 62–625% of annual N runoff, approximately 28–333% of annual atmospheric N deposition and approximately 31–312% of the N sequestered by trees. The N flux approximation is most sensitive to moose population levels and, as such, is influenced by wolves, climate warming and disease. The potential for other terrestrial ungulates that feed on aquatic plants to provide significant nutrient repletion across ecotones is unknown but important to examine in the context of trophic rewilding. The extent to which predators influence ungulate abundance indirectly impacts this nutrient repletion. This article is part of the theme issue ‘Trophic rewilding: consequences for ecosystems under global change’.

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0419 - Climate warming enhances reliance of functioning on soil microbial community diversity

10.26226/morressier.5b5199beb1b87b000ecee5c9 ◽

2018 ◽

Author(s):

Lauren Hale

Keyword(s):

Microbial Community ◽

Climate Warming ◽

Soil Microbial Community ◽

Community Diversity ◽

Microbial Community Diversity ◽

Soil Microbial

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ATMOSPHERIC N DEPOSITION TO THE COASTAL AREA OF THE BLACK SEA: SOURCES, INTRA-ANNUAL VARIATIONS AND IMPORTANCE FOR BIOGEOCHEMISTRY AND PRODUCTIVITY OF THE SURFACE LAYER

Proceedings of International Conference "Managinag risks to coastal regions and communities in a changinag world" (EMECS'11 - SeaCoasts XXVI) ◽

10.31519/conferencearticle_5b1b945160eed9.16985540 ◽

2017 ◽

Author(s):

Alla Varenik ◽

Sergey Konovalov ◽

Sergey Konovalov

Keyword(s):

Primary Production ◽

Black Sea ◽

Marine Ecosystem ◽

C:N Ratio ◽

N Deposition ◽

Local Source ◽

The Black Sea ◽

Coastal Zones ◽

Atmospheric N Deposition ◽

Urban Location

Atmospheric precipitations can be an important source of nutrients to open and coastal zones of marine ecosystem. Jickells [1] has published that atmospheric depositions can sup-port 5-25% of nitrogen required to primary production. Bulk atmospheric precipitations have been collected in a rural location at the Black Sea Crimean coast – Katsiveli settlement, and an urban location – Sevastopol city. Samples have been analyzed for inorganic fixed nitrogen (IFN) – nitrate, nitrite, and ammonium. Deposi-tions have been calculated at various space and time scales. The monthly volume weighted mean concentration of IFN increases from summer to winter in both locations. A significant local source of IFN has been revealed for the urban location and this source and its spatial influence have been quantified. IFN deposition with atmospheric precipitations is up to 5% of its background content in the upper 10 m layer of water at the north-western shelf of the Black Sea. Considering Redfield C:N ratio (106:16) and the rate of primary production (PP) in coastal areas of the Black Sea of about 100-130 g C m-2 year-1 we have assessed that average atmospheric IFN depositions may intensify primary production by 4.5% for rural locations, but this value is increased many-fold in urban locations due to local IFN sources.

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Canopy uptake of atmospheric N deposition at a conifer forest: part I -canopy N budget, photosynthetic efficiency and net ecosystem exchange

Tellus B ◽

10.3402/tellusb.v59i3.17018 ◽

2007 ◽

Vol 59 (3) ◽

Cited By ~ 1

Author(s):

H. Sievering ◽

T. Tomaszewski ◽

J. Torizzo

Keyword(s):

Photosynthetic Efficiency ◽

Net Ecosystem Exchange ◽

N Deposition ◽

Conifer Forest ◽

Atmospheric N Deposition ◽

N Budget ◽

Canopy Uptake

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ATMOSPHERIC N DEPOSITION TO THE COASTAL AREA OF THE BLACK SEA: SOURCES, INTRA-ANNUAL VARIATIONS AND IMPORTANCE FOR BIOGEOCHEMISTRY AND PRODUCTIVITY OF THE SURFACE LAYER

Proceedings of International Conference "Managinag risks to coastal regions and communities in a changinag world" (EMECS'11 - SeaCoasts XXVI) ◽

10.21610/conferencearticle_58b43155bc901 ◽

2017 ◽

Author(s):

Alla Varenik ◽

Sergey Konovalov ◽

Sergey Konovalov

Keyword(s):

Primary Production ◽

Black Sea ◽

Marine Ecosystem ◽

C:N Ratio ◽

N Deposition ◽

Local Source ◽

The Black Sea ◽

Coastal Zones ◽

Atmospheric N Deposition ◽

Urban Location

Atmospheric precipitations can be an important source of nutrients to open and coastal zones of marine ecosystem. Jickells [1] has published that atmospheric depositions can sup-port 5-25% of nitrogen required to primary production. Bulk atmospheric precipitations have been collected in a rural location at the Black Sea Crimean coast – Katsiveli settlement, and an urban location – Sevastopol city. Samples have been analyzed for inorganic fixed nitrogen (IFN) – nitrate, nitrite, and ammonium. Deposi-tions have been calculated at various space and time scales. The monthly volume weighted mean concentration of IFN increases from summer to winter in both locations. A significant local source of IFN has been revealed for the urban location and this source and its spatial influence have been quantified. IFN deposition with atmospheric precipitations is up to 5% of its background content in the upper 10 m layer of water at the north-western shelf of the Black Sea. Considering Redfield C:N ratio (106:16) and the rate of primary production (PP) in coastal areas of the Black Sea of about 100-130 g C m-2 year-1 we have assessed that average atmospheric IFN depositions may intensify primary production by 4.5% for rural locations, but this value is increased many-fold in urban locations due to local IFN sources.

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