scholarly journals Processes regulating progressive nitrogen limitation under elevated carbon dioxide: a meta-analysis

2016 ◽  
Vol 13 (9) ◽  
pp. 2689-2699 ◽  
Author(s):  
Junyi Liang ◽  
Xuan Qi ◽  
Lara Souza ◽  
Yiqi Luo
Keyword(s):  
Elevated Co2 ◽  
Meta Analysis ◽  
Co2 Enrichment ◽  
C Sequestration ◽  
N2o Emission ◽  
N Fixation ◽  
N Cycle ◽  
Biological N Fixation ◽  
Fertilization Effect ◽  
Progressive Nitrogen Limitation

Abstract. The nitrogen (N) cycle has the potential to regulate climate change through its influence on carbon (C) sequestration. Although extensive research has explored whether or not progressive N limitation (PNL) occurs under CO2 enrichment, a comprehensive assessment of the processes that regulate PNL is still lacking. Here, we quantitatively synthesized the responses of all major processes and pools in the terrestrial N cycle with meta-analysis of CO2 experimental data available in the literature. The results showed that CO2 enrichment significantly increased N sequestration in the plant and litter pools but not in the soil pool, partially supporting one of the basic assumptions in the PNL hypothesis that elevated CO2 results in more N sequestered in organic pools. However, CO2 enrichment significantly increased the N influx via biological N fixation and the loss via N2O emission, but decreased the N efflux via leaching. In addition, no general diminished CO2 fertilization effect on plant growth was observed over time up to the longest experiment of 13 years. Overall, our analyses suggest that the extra N supply by the increased biological N fixation and decreased leaching may potentially alleviate PNL under elevated CO2 conditions in spite of the increases in plant N sequestration and N2O emission. Moreover, our syntheses indicate that CO2 enrichment increases soil ammonium (NH4+) to nitrate (NO3−) ratio. The changed NH4+/NO3− ratio and subsequent biological processes may result in changes in soil microenvironments, above-belowground community structures and associated interactions, which could potentially affect the terrestrial biogeochemical cycles. In addition, our data synthesis suggests that more long-term studies, especially in regions other than temperate ones, are needed for comprehensive assessments of the PNL hypothesis.

scholarly journals Processes regulating progressive nitrogen limitation under elevated carbon dioxide: a meta-analysis

2015 ◽  
Vol 12 (20) ◽  
pp. 16953-16977 ◽  
Author(s):  
J. Liang ◽  
X. Qi ◽  
L. Souza ◽  
Y. Luo
Keyword(s):  
Climate Change ◽  
Meta Analysis ◽  
Co2 Enrichment ◽  
C Sequestration ◽  
N Fixation ◽  
N Cycle ◽  
Biological N Fixation ◽  
Fertilization Effect ◽  
Soil Pool ◽  
Progressive Nitrogen Limitation

Abstract. Nitrogen (N) cycle has the potential to regulate climate change through its influence on carbon (C) sequestration. Although extensive researches have been done to explore whether or not progressive N limitation (PNL) occurs under CO2 enrichment, a comprehensive assessment of the processes that regulate PNL is still lacking. Here, we quantitatively synthesized the responses of all major processes and pools in terrestrial N cycle with meta-analysis of CO2 experimental data available in the literature. The results showed that CO2 enrichment significantly increased N sequestration in plant and litter pools but not in soil pool. Thus, the basis of PNL occurrence partially exists. However, CO2 enrichment also significantly increased the N influx via biological N fixation, but decreased the N efflux via leaching. In addition, no general diminished CO2 fertilization effect on plant growth over time was observed. Overall, our analyses suggest that the extra N supply by the increased biological N fixation and decreased leaching may potentially alleviate PNL under elevated CO2 conditions. Moreover, our synthesis showed that CO2 enrichment increased soil ammonium (NH4+) but decreased nitrate (NO3-). The different responses of NH4+ and NO3-, and the consequent biological processes, may result in changes in soil microenvironment, community structures and above-belowground interactions, which could potentially affect the terrestrial biogeochemical cycles and the feedback to climate change.

scholarly journals Global soil nitrous oxide emissions in a dynamic carbon-nitrogen model

2015 ◽  
Vol 12 (21) ◽  
pp. 6405-6427 ◽  
Author(s):  
Y. Huang ◽  
S. Gerber
Keyword(s):  
Nitrous Oxide ◽  
Elevated Co2 ◽  
N Uptake ◽  
N2o Emission ◽  
Nitrous Oxide Emissions ◽  
N Fixation ◽  
N Availability ◽  
Plant N Uptake ◽  
Biological N Fixation ◽  
N2o Fluxes

Abstract. Nitrous oxide (N2O) is an important greenhouse gas that also contributes to the depletion of stratospheric ozone. Due to its high temporal and spatial heterogeneity, a quantitative understanding of terrestrial N2O emission and its variabilities and responses to climate change are challenging. We added a soil N2O emission module to the dynamic global land model LM3V-N, and tested its sensitivity to mechanisms that affect the level of mineral nitrogen (N) in soil such as plant N uptake, biological N fixation, amount of volatilized N redeposited after fire, and nitrification-denitrification. We further tested the relationship between N2O emission and soil moisture, and assessed responses to elevated CO2 and temperature. Results extracted from the corresponding gridcell (without site-specific forcing data) were comparable with the average of cross-site observed annual mean emissions, although differences remained across individual sites if stand-level measurements were representative of gridcell emissions. Processes, such as plant N uptake and N loss through fire volatilization that regulate N availability for nitrification-denitrification have strong controls on N2O fluxes in addition to the parameterization of N2O loss through nitrification and denitrification. Modelled N2O fluxes were highly sensitive to water-filled pore space (WFPS), with a global sensitivity of approximately 0.25 TgN per year per 0.01 change in WFPS. We found that the global response of N2O emission to CO2 fertilization was largely determined by the response of tropical emissions with reduced N2O fluxes in the first few decades and increases afterwards. The initial reduction was linked to N limitation under higher CO2 level, and was alleviated through feedbacks such as biological N fixation. The extratropical response was weaker and generally positive, highlighting the need to expand field studies in tropical ecosystems. We did not find synergistic effects between warming and CO2 increase as reported in analyses with different models. Warming generally enhanced N2O efflux and the enhancement was greatly dampened when combined with elevated CO2, although CO2 alone had a small effect. The differential response in the tropics compared to extratropics with respect to magnitude and sign suggests caution when extrapolating from current field CO2 enrichment and warming studies to the globe.

Tillage effects on N2O emission from soils under corn and soybeans in Eastern Canada

2008 ◽  
Vol 88 (2) ◽  
pp. 153-161 ◽  
Author(s):  
E G Gregorich ◽  
P. Rochette ◽  
P. St-Georges ◽  
U F McKim ◽  
C. Chan
Keyword(s):  
Nitrous Oxide ◽  
Agricultural Soils ◽  
N2o Emission ◽  
N Fixation ◽  
Eastern Canada ◽  
N Losses ◽  
Biological N Fixation ◽  
No Till ◽  
Tillage System ◽  
Glycine Max L

The ways in which agricultural soils are managed influence the production and emission of nitrous oxide (N2O). A field study was undertaken in 2003, 2004, and 2005 to quantify and evaluate N2O emission from tilled and no-till soils under corn (Zea maysL.) and soybeans (Glycine max L. Merr) in Ontario. Overall, N2O emission was lowest in 2003, the driest and coolest of the 3 yr. In 2004, the significantly larger annual N2O emission from no-till soils and soils under corn was attributed to an episode of very high N2O emission following the application of fertilizer during a period of wet weather. That the N loss by N2O emission occurred only in no-till soils and was large and long-lasting (~4 wk) confirms the strong effect that management has in reducing fertilizer N losses. In 2005, tilled soils had significantly larger N2O emission than no-till soils, most of which was emitted before the end of June. Because the tilled soils were better aerated , nitrification was likely the primary process contributing to the larger emission. Relatively low N2O emission from soybeans suggests biological N fixation does not appear to contribute substantially to the annual N2O emission. Further study of methods to reduce N2O emission in agricultural systems should focus on improving N use efficiency within a particular tillage system rather than looking to differences between tillage systems. Key words: Tillage, corn, soybeans, nitrogen, nitrous oxide, biogenic gas emission, nitrification, denitrification, fertilization

scholarly journals Global soil nitrous oxide emissions in a dynamic carbon–nitrogen model

2015 ◽  
Vol 12 (3) ◽  
pp. 3101-3143 ◽  
Author(s):  
Y. Y. Huang ◽  
S. Gerber
Keyword(s):  
Nitrous Oxide ◽  
Elevated Co2 ◽  
Pore Space ◽  
Stratospheric Ozone ◽  
Co2 Enrichment ◽  
Field Studies ◽  
Global Scale ◽  
N2o Emission ◽  
Nitrous Oxide Emissions ◽  
Moisture Regime

Abstract. Nitrous oxide (N2O) is an important greenhouse gas that also contributes to the depletion of stratospheric ozone. With high temporal and spatial heterogeneity, a quantitative understanding of terrestrial N2O emission, its variabilities and reponses to climate change is challenging. We added a soil N2O emission module to the dynamic global land model LM3V-N, and tested its sensitivity to soil moisture regime and responses to elevated CO2 and temperature. The model was capable of reproducing the average of cross-site observed annual mean emissions, although differences remained across individual sites if stand-level measurements were representative of gridcell emissions. Modelled N2O fluxes were highly sensitive to water filled pore space (WFPS), with a global sensitivity of approximately 0.25 Tg N year−1 per 0.01 change in WFPS. We found that the global response of N2O emission to CO2 fertilization was largely determined by the response of tropical emissions, whereas the extratropical response was weaker and different, highlighting the need to expand field studies in tropical ecosystems. Warming generally enhanced N2O efflux, and the enhancement was greatly dampened when combined with elevated CO2, although CO2 alone had a small effect. Our analysis suggests caution when extrapolation from current field CO2 enrichment and warming studies to the global scale.

A meta-analysis of elevated [CO2 ] effects on soybean (Glycine max ) physiology, growth and yield

2002 ◽  
Vol 8 (8) ◽  
pp. 695-709 ◽  
Author(s):  
Elizabeth A. Ainsworth ◽  
Phillip A. Davey ◽  
Carl J. Bernacchi ◽  
Orla C. Dermody ◽  
Emily A. Heaton ◽  
...  
Keyword(s):  
Glycine Max ◽  
Elevated Co2 ◽  
Meta Analysis ◽  
Growth And Yield ◽  
Co2 Effects

Canopy development and hydraulic function in Eucalyptus tereticornis grown in drought in CO2-enriched atmospheres

2007 ◽  
Vol 34 (12) ◽  
pp. 1137 ◽  
Author(s):  
Brian J. Atwell ◽  
Martin L. Henery ◽  
Gordon S. Rogers ◽  
Saman P. Seneweera ◽  
Marie Treadwell ◽  
...  
Keyword(s):  
Elevated Co2 ◽  
Shoot Growth ◽  
Co2 Enrichment ◽  
Atmospheric Co2 ◽  
Shoot Biomass ◽  
Eucalyptus Tereticornis ◽  
Growth Responses ◽  
Ambient Conditions ◽  
Long Distance ◽  
Pipe Model

We report on the relationship between growth, partitioning of shoot biomass and hydraulic development of Eucalyptus tereticornis Sm. grown in glasshouses for six months. Close coordination of stem vascular capacity and shoot architecture is vital for survival of eucalypts, especially as developing trees are increasingly subjected to spasmodic droughts and rising atmospheric CO2 levels. Trees were exposed to constant soil moisture deficits in 45 L pots (30–50% below field capacity), while atmospheric CO2 was raised to 700 μL CO2 L–1 in matched glasshouses using a hierarchical, multi-factorial design. Enrichment with CO2 stimulated shoot growth rates for 12–15 weeks in well-watered trees but after six months of CO2 enrichment, shoot biomasses were not significantly heavier (30% stimulation) in ambient conditions. By contrast, constant drought arrested shoot growth after 20 weeks under ambient conditions, whereas elevated CO2 sustained growth in drought and ultimately doubled the shoot biomass relative to ambient conditions. These growth responses were achieved through an enhancement of lateral branching up to 8-fold due to CO2 enrichment. In spite of larger transpiring canopies, CO2 enrichment also improved the daytime water status of leaves of droughted trees. Stem xylem development was highly regulated, with vessels per unit area and cross sectional area of xylem vessels in stems correlated inversely across all treatments. Furthermore, vessel numbers related to the numbers of leaves on lateral branches, broadly supporting predictions arising from Pipe Model Theory that the area of conducting tissue should correlate with leaf area. Diminished water use of trees in drought coincided with a population of narrower xylem vessels, constraining hydraulic capacity of stems. Commensurate with the positive effects of elevated CO2 on growth, development and leaf water relations of droughted trees, the capacity for long-distance water transport also increased.

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