scholarly journals Modelling the demand for new nitrogen fixation by terrestrial ecosystems

2016 ◽  
Author(s):  
◽  
I. Colin Prentice
Keyword(s):  
Net Primary Production ◽  
N Uptake ◽  
Terrestrial Ecosystems ◽  
Co2 Concentration ◽  
N Deposition ◽  
Anthropogenic Sources ◽  
N Fixation ◽  
Biological N Fixation ◽  
Global Dynamic ◽  
Geographic Patterns

Abstract. Continual input of reactive nitrogen (N) is required to support the natural turnover of N in terrestrial ecosystems. This “N demand” can be satisfied in various ways including biological N fixation (BNF) (the dominant pathway under natural conditions), lightning-induced abiotic N fixation, N uptake from sedimentary substrates, and N deposition from natural and anthropogenic sources. We estimated the global new N fixation demand (NNF), i.e. the total new N input required to sustain net primary production (NPP) in non-agricultural terrestrial ecosystems regardless of its origin, using a N-enabled global dynamic vegetation model (DyN-LPJ). DyN-LPJ does not explicitly simulate BNF; rather, it estimates total NNF using a mass balance criterion and assumes that this demand is met from one source or another. The model was run in steady state, and then in transient mode driven by recent changes in CO2 concentration and climate. A range of values for key stoichiometric parameters was considered, based on recently published analyses. Modelled NPP, and C:N ratios of litter and soil organic matter, were consistent with independent estimates. Modelled geographic patterns of ecosystem NNF were similar to other analyses, but actual estimated values exceeded recent estimates of global BNF. The results were sensitive to a few key parameters: the fraction of litter carbon respired to CO2 during decomposition, and plant type-specific C:N ratios of litter and soil. The modelled annual NNF increased by about 15% during the course of the transient run, mainly due to increasing CO2 concentration. The model did not overestimate recent terrestrial carbon uptake, suggesting that the increase in NNF demand has so far been met. Rising CO2 is further increasing the NNF demand, while the future capacity of N sources to support this is unknown.

scholarly journals Modelling the demand for new nitrogen fixation by terrestrial ecosystems

2017 ◽  
Vol 14 (7) ◽  
pp. 2003-2017 ◽  
Author(s):  
◽  
I. Colin Prentice
Keyword(s):  
Net Primary Production ◽  
N Uptake ◽  
Terrestrial Ecosystems ◽  
Co2 Concentration ◽  
N Deposition ◽  
Anthropogenic Sources ◽  
N Fixation ◽  
Biological N Fixation ◽  
Global Dynamic ◽  
Geographic Patterns

Abstract. Continual input of reactive nitrogen (N) is required to support the natural turnover of N in terrestrial ecosystems. This N demand can be satisfied in various ways, including biological N fixation (BNF) (the dominant pathway under natural conditions), lightning-induced abiotic N fixation, N uptake from sedimentary substrates, and N deposition from natural and anthropogenic sources. We estimated the global new N fixation demand (NNF), i.e. the total new N input required to sustain net primary production (NPP) in non-agricultural terrestrial ecosystems regardless of its origin, using a N-enabled global dynamic vegetation model (DyN-LPJ). DyN-LPJ does not explicitly simulate BNF; rather, it estimates total NNF using a mass balance criterion and assumes that this demand is met from one source or another. The model was run in steady state and then in transient mode driven by recent changes in CO2 concentration and climate. A range of values for key stoichiometric parameters was considered, based on recently published analyses. Modelled NPP and C : N ratios of litter and soil organic matter were consistent with independent estimates. Modelled geographic patterns of ecosystem NNF were similar to other analyses, but actual estimated values exceeded recent estimates of global BNF. The results were sensitive to a few key parameters: the fraction of litter carbon respired to CO2 during decomposition and plant-type-specific C : N ratios of litter and soil. The modelled annual NNF increased by about 15 % during the course of the transient run, mainly due to increasing CO2 concentration. The model did not overestimate recent terrestrial carbon uptake, suggesting that the increase in NNF demand has so far been met. Rising CO2 is further increasing the NNF demand, while the future capacity of N sources to support this is unknown.

scholarly journals Residual effect of clover-rich leys on soil nitrogen and successive grain crops

2008 ◽  
Vol 17 (1) ◽  
pp. 73 ◽  
Author(s):  
A. NYKÄNEN ◽  
A. GRANSTEDT ◽  
L. JAUHIAINEN
Keyword(s):  
Field Experiments ◽  
Clayey Soil ◽  
N Uptake ◽  
Residual Effect ◽  
Red Clover ◽  
N Leaching ◽  
N Fixation ◽  
Mineral N ◽  
Total N ◽  
Biological N Fixation

Legume-based leys form the basis for crop rotations in organic farming as they fix nitrogen (N) from the atmosphere for the succeeding crops. The age, yield, C:N, biological N fixation (BNF) and total N of red clover-grass leys were studied for their influence on yields, N uptake and N use efficiency (NUE) of the two sequential cereal crops planted after the leys. Mineral N in deeper soil (30-90 cm) was measured to determine N leaching risk. Altogether, four field experiments were carried out in 1994-1998 at two sites. The age of the ley had no significant effect on the yields and N uptake of the two subsequent cereals. Surprisingly, the residual effect of the leys was negligible, at 0–20 kg N ha-1yr-1. On the other hand, the yield and C:N of previous red clover-grass leys, as well as BNF-N and total-N incorporated into the soil influenced subsequent cereals. NUEs of cereals after ley incorporation were rather high, varying from 30% to 80%. This might indicate that other factors, such as competition from weeds, prevented maximal growth of cereals. The mineral N content deeper in the soil was mostly below 10 kg ha-1 in the sandy soil of Juva, but was 5-25 kg ha-1 in clayey soil of Mietoinen.;

scholarly journals A “toy” model of biogeochemical dynamics on climate gradients

2021 ◽  
Author(s):  
Peter M. Vitousek ◽  
Jesse Bloom Bateman ◽  
Oliver A. Chadwick
Keyword(s):  
Water Balance ◽  
Plant Biomass ◽  
Potential Evapotranspiration ◽  
Net Primary Production ◽  
N Fixation ◽  
Climate Gradients ◽  
P Limitation ◽  
Biological N Fixation ◽  
Total P ◽  
P Supply

AbstractWe used a simple “toy” model to aid in the evaluation of the controls of biogeochemical patterns along a climate gradient. The model includes simplified treatments of water balance (precipitation minus Potential Evapotranspiration), leaching, weathering of cation- and P-bearing minerals, N cycling and loss, biomass production, and biological N fixation. We use δ15N as a central integrator of biogeochemical processes, because δ15N integrates multiple pathways of N input, output, and transformation in ecosystems. The model simulated the location and magnitude of a peak in δ15N on a gradient on Kohala Volcano, Hawai‘i which peaked ~  + 14 ‰ in sites receiving ~ 3.5 cm/month average precipitation (− 1300 mm/year water balance); the model also captured a peak in total P in surface soil at intermediate levels of precipitation and water balance, and other biogeochemical features on the gradient. We then applied the model to understanding the patterns of and mechanisms underlying nutrient limitation to net primary production (NPP) and plant biomass on the gradient, testing for the existence and extent of N and P limitation by simulated additions of N and/or P in the model. Both a simulated symbiotic biological N fixer and a simulated non-fixer were limited by P supply across the gradient; the non-fixer was independently limited by N supply in wetter sites. By running the toy model with and without the influence of temperature, we demonstrated that water is the most important factor shaping biogeochemical patterns on this gradient.

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.

scholarly journals A model using marginal efficiency of investment to analyze carbon and nitrogen interactions in terrestrial ecosystems (ACONITE Version 1)

2014 ◽  
Vol 7 (5) ◽  
pp. 2015-2037 ◽  
Author(s):  
R. Q. Thomas ◽  
M. Williams
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Primary Productivity ◽  
N Uptake ◽  
Terrestrial Ecosystems ◽  
N Fixation ◽  
Earth System ◽  
Area Index ◽  
Temperate Deciduous ◽  
C And N

Abstract. Carbon (C) and nitrogen (N) cycles are coupled in terrestrial ecosystems through multiple processes including photosynthesis, tissue allocation, respiration, N fixation, N uptake, and decomposition of litter and soil organic matter. Capturing the constraint of N on terrestrial C uptake and storage has been a focus of the Earth System Modeling community. However, there is little understanding of the trade-offs and sensitivities of allocating C and N to different tissues in order to optimize the productivity of plants. Here we describe a new, simple model of ecosystem C–N cycling and interactions (ACONITE), that builds on theory related to plant economics in order to predict key ecosystem properties (leaf area index, leaf C : N, N fixation, and plant C use efficiency) based on the outcome of assessments of the marginal change in net C or N uptake associated with a change in allocation of C or N to plant tissues. We simulated and evaluated steady-state ecosystem stocks and fluxes in three different forest ecosystems types (tropical evergreen, temperate deciduous, and temperate evergreen). Leaf C : N differed among the three ecosystem types (temperate deciduous < tropical evergreen < temperature evergreen), a result that compared well to observations from a global database describing plant traits. Gross primary productivity (GPP) and net primary productivity (NPP) estimates compared well to observed fluxes at the simulation sites. Simulated N fixation at steady-state, calculated based on relative demand for N and the marginal return on C investment to acquire N, was an order of magnitude higher in the tropical forest than in the temperate forest, consistent with observations. A sensitivity analysis revealed that parameterization of the relationship between leaf N and leaf respiration had the largest influence on leaf area index and leaf C : N. A parameter governing how photosynthesis scales with day length had the largest influence on total vegetation C, GPP, and NPP. Multiple parameters associated with photosynthesis, respiration, and N uptake influenced the rate of N fixation. Overall, our ability to constrain leaf area index and allow spatially and temporally variable leaf C : N can help address challenges simulating these properties in ecosystem and Earth System models. Furthermore, the simple approach with emergent properties based on coupled C–N dynamics has potential for use in research that uses data-assimilation methods to integrate data on both the C and N cycles to improve C flux forecasts.

scholarly journals A Research Road Map for Responsible Use of Agricultural Nitrogen

2021 ◽  
Vol 5 ◽  
Author(s):  
Michael Udvardi ◽  
Frederick E. Below ◽  
Michael J. Castellano ◽  
Alison J. Eagle ◽  
Ken E. Giller ◽  
...  
Keyword(s):  
Current Knowledge ◽  
N Uptake ◽  
Green Revolution ◽  
Sustainable Use ◽  
Industrial Process ◽  
Agricultural Practices ◽  
N Fixation ◽  
N Availability ◽  
Soil N ◽  
Biological N Fixation

Nitrogen (N) is an essential but generally limiting nutrient for biological systems. Development of the Haber-Bosch industrial process for ammonia synthesis helped to relieve N limitation of agricultural production, fueling the Green Revolution and reducing hunger. However, the massive use of industrial N fertilizer has doubled the N moving through the global N cycle with dramatic environmental consequences that threaten planetary health. Thus, there is an urgent need to reduce losses of reactive N from agriculture, while ensuring sufficient N inputs for food security. Here we review current knowledge related to N use efficiency (NUE) in agriculture and identify research opportunities in the areas of agronomy, plant breeding, biological N fixation (BNF), soil N cycling, and modeling to achieve responsible, sustainable use of N in agriculture. Amongst these opportunities, improved agricultural practices that synchronize crop N demand with soil N availability are low-hanging fruit. Crop breeding that targets root and shoot physiological processes will likely increase N uptake and utilization of soil N, while breeding for BNF effectiveness in legumes will enhance overall system NUE. Likewise, engineering of novel N-fixing symbioses in non-legumes could reduce the need for chemical fertilizers in agroecosystems but is a much longer-term goal. The use of simulation modeling to conceptualize the complex, interwoven processes that affect agroecosystem NUE, along with multi-objective optimization, will also accelerate NUE gains.

scholarly journals A model using marginal efficiency of investment to analyse carbon and nitrogen interactions in terrestrial ecosystems (ACONITE Version 1)

2014 ◽  
Vol 7 (2) ◽  
pp. 2525-2580 ◽  
Author(s):  
R. Q. Thomas ◽  
M. Williams
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
N Uptake ◽  
Terrestrial Ecosystems ◽  
N Fixation ◽  
Earth System ◽  
Area Index ◽  
Temperate Deciduous ◽  
C And N ◽  
Leaf N

Abstract. Carbon (C) and nitrogen (N) cycles are coupled in terrestrial ecosystems through multiple processes including photosynthesis, tissue allocation, respiration, N fixation, N uptake, and decomposition of litter and soil organic matter. Capturing the constraint of N on terrestrial C uptake and storage has been a focus of the Earth System modelling community. However there is little understanding of the trade-offs and sensitivities of allocating C and N to different tissues in order to optimize the productivity of plants. Here we describe a new, simple model of ecosystem C–N cycling and interactions (ACONITE), that builds on theory related to plant economics in order to predict key ecosystem properties (leaf area index, leaf C : N, N fixation, and plant C use efficiency) using emergent constraints provided by marginal returns on investment for C and/or N allocation. We simulated and evaluated steady-state ecosystem stocks and fluxes in three different forest ecosystems types (tropical evergreen, temperate deciduous, and temperate evergreen). Leaf C : N differed among the three ecosystem types (temperate deciduous < tropical evergreen < temperature evergreen), a result that compared well to observations from a global database describing plant traits. Gross primary productivity (GPP) and net primary productivity (NPP) estimates compared well to observed fluxes at the simulation sites. Simulated N fixation at steady-state, calculated based on relative demand for N and the marginal return on C investment to acquire N, was an order of magnitude higher in the tropical forest than in the temperate forest, consistent with observations. A sensitivity analysis revealed that parameterization of the relationship between leaf N and leaf respiration had the largest influence on leaf area index and leaf C : N. Also, a widely used linear leaf N-respiration relationship did not yield a realistic leaf C : N, while a more recently reported non-linear relationship performed better. A parameter governing how photosynthesis scales with day length had the largest influence on total vegetation C, GPP, and NPP. Multiple parameters associated with photosynthesis, respiration, and N uptake influenced the rate of N fixation. Overall, our ability to constrain leaf area index and have spatially and temporally variable leaf C : N helps address challenges for ecosystem and Earth System models. Furthermore, the simple approach with emergent properties based on coupled C–N dynamics has potential for use in research that uses data-assimilation methods to integrate data on both the C and N cycles to improve C flux forecasts.

scholarly journals A STELLA-Based Model to Simultaneously Predict Hydrological Processes, N Uptake and Biomass Production in a Eucalyptus Plantation

Forests ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 515
Author(s):  
Ying Ouyang ◽  
Gary Feng ◽  
Heidi Renninger ◽  
Theodor D. Leininger ◽  
Prem Parajuli ◽  
...  
Keyword(s):  
Water Use ◽  
Biomass Production ◽  
Net Primary Production ◽  
N Uptake ◽  
Hydrological Processes ◽  
Modeling Tools ◽  
Eucalyptus Plantation ◽  
Simulation Scenario ◽  
Use Efficiency ◽  
N Use

Eucalyptus is one of the fastest growing hardwoods for bioenergy production. Currently, few modeling tools exist to simultaneously estimate soil hydrological processes, nitrogen (N) uptake, and biomass production in a eucalyptus plantation. In this study, a STELLA (Structural Thinking and Experiential Learning Laboratory with Animation)-based model was developed to meet this need. After the model calibration and validation, a simulation scenario was developed to assess eucalyptus (E. grandis × urophylla) annual net primary production (ANPP), woody biomass production (WBP), water use efficiency (WUE), and N use efficiency (NUE) for a simulation period of 20 years. Simulation results showed that a typical annual variation pattern was predicted for water use, N uptake, and ANPP, increasing from spring to fall and decreasing from fall to the following winter. Overall, the average NUE during the growth stage was 700 kg/kg. To produce 1000 kg eucalyptus biomass, it required 114.84 m3 of water and 0.92 kg of N. This study suggests that the STELLA-based model is a useful tool to estimate ANPP, WBP, WUE, and NUE in a eucalyptus plantation.

scholarly journals Nitrogen cycling in Sandusky Bay, Lake Erie: oscillations between strong and weak export and implications for harmful algal blooms

2018 ◽  
Vol 15 (9) ◽  
pp. 2891-2907 ◽  
Author(s):  
Kateri R. Salk ◽  
George S. Bullerjahn ◽  
Robert Michael L. McKay ◽  
Justin D. Chaffin ◽  
Nathaniel E. Ostrom
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Lake Erie ◽  
N Uptake ◽  
N Fixation ◽  
N Budget ◽  
N2o Production ◽  
N Removal ◽  
Uptake Rates ◽  
N Loading

Abstract. Recent global water quality crises point to an urgent need for greater understanding of cyanobacterial harmful algal blooms (cHABs) and their drivers. Nearshore areas of Lake Erie such as Sandusky Bay may become seasonally limited by nitrogen (N) and are characterized by distinct cHAB compositions (i.e., Planktothrix over Microcystis). This study investigated phytoplankton N uptake pathways, determined drivers of N depletion, and characterized the N budget in Sandusky Bay. Nitrate (NO3-) and ammonium (NH4+) uptake, N fixation, and N removal processes were quantified by stable isotopic approaches. Dissimilatory N reduction was a relatively modest N sink, with denitrification, anammox, and N2O production accounting for 84, 14, and 2 % of sediment N removal, respectively. Phytoplankton assimilation was the dominant N uptake mechanism, and NO3- uptake rates were higher than NH4+ uptake rates. Riverine N loading was sometimes insufficient to meet assimilatory and dissimilatory demands, but N fixation alleviated this deficit. N fixation made up 23.7–85.4 % of total phytoplankton N acquisition and indirectly supports Planktothrix blooms. However, N fixation rates were surprisingly uncorrelated with NO3- or NH4+ concentrations. Owing to temporal separation in sources and sinks of N to Lake Erie, Sandusky Bay oscillates between a conduit and a filter of downstream N loading to Lake Erie, delivering extensively recycled forms of N during periods of low export. Drowned river mouths such as Sandusky Bay are mediators of downstream N loading, but climate-change-induced increases in precipitation and N loading will likely intensify N export from these systems.

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