Nitrogen deposition: how important is it for global terrestrial carbon uptake?

Abstract. Global carbon budget studies indicate that the terrestrial ecosystems have remained a~large sink for carbon despite widespread deforestation activities. CO2-fertilization, N deposition and re-growth of mid-latitude forests are believed to be key drivers for land carbon uptake. In this study, we assess the importance of N deposition by performing idealized near-equilibrium simulations using the Community Land Model 4.0 (CLM4). In our equilibrium simulations, only 12–17% of the deposited Nitrogen is assimilated into the ecosystem and the corresponding carbon uptake can be inferred from a C : N ratio of 20:1. We calculate the sensitivity of the terrestrial biosphere for CO2-fertilization, climate warming and N deposition as changes in total ecosystem carbon for unit changes in global mean atmospheric CO2 concentration, global mean temperature and Tera grams of Nitrogen deposition per year, respectively. Based on these sensitivities, it is estimated that about 242 PgC could have been taken up by land due to the CO2 fertilization effect and an additional 175 PgC taken up as a result of the increased N deposition since the pre-industrial period. Because of climate warming, terrestrial ecosystem could have lost about 152 PgC during the same period. Therefore, since preindustrial times terrestrial carbon losses due to warming may have been approximately compensated by effects of increased N deposition, whereas the effect of CO2-fertilization is approximately indicative of the current increase in terrestrial carbon stock. Our simulations also suggest that the sensitivity of carbon storage to increased N deposition decreases beyond current levels, indicating climate warming effects on carbon storage may overwhelm N deposition effects in the future.

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Nitrogen deposition: how important is it for global terrestrial carbon uptake?

Biogeosciences ◽

10.5194/bg-10-7147-2013 ◽

2013 ◽

Vol 10 (11) ◽

pp. 7147-7160 ◽

Cited By ~ 24

Author(s):

G. Bala ◽

N. Devaraju ◽

R. K. Chaturvedi ◽

K. Caldeira ◽

R. Nemani

Keyword(s):

Nitrogen Deposition ◽

Carbon Storage ◽

Climate Warming ◽

N Deposition ◽

Carbon Uptake ◽

Terrestrial Carbon ◽

Co2 Fertilization ◽

Current Increase ◽

Community Land Model ◽

Global Mean

Abstract. Global carbon budget studies indicate that the terrestrial ecosystems have remained a large sink for carbon despite widespread deforestation activities. CO2 fertilization, N deposition and re-growth of mid-latitude forests are believed to be key drivers for land carbon uptake. In this study, we assess the importance of N deposition by performing idealized near-equilibrium simulations using the Community Land Model 4.0 (CLM4). In our equilibrium simulations, only 12–17% of the deposited nitrogen is assimilated into the ecosystem and the corresponding carbon uptake can be inferred from a C : N ratio of 20 : 1. We calculate the sensitivity of the terrestrial biosphere for CO2 fertilization, climate warming and N deposition as changes in total ecosystem carbon for unit changes in global mean atmospheric CO2 concentration, global mean temperature and Tera grams of nitrogen deposition per year, respectively. Based on these sensitivities, it is estimated that about 242 PgC could have been taken up by land due to the CO2 fertilization effect and an additional 175 PgC taken up as a result of the increased N deposition since the pre-industrial period. Because of climate warming, the terrestrial ecosystem could have lost about 152 PgC during the same period. Therefore, since pre-industrial times terrestrial carbon losses due to warming may have been more or less compensated by effects of increased N deposition, whereas the effect of CO2 fertilization is approximately indicative of the current increase in terrestrial carbon stock. Our simulations also suggest that the sensitivity of carbon storage to increased N deposition decreases beyond current levels, indicating that climate warming effects on carbon storage may overwhelm N deposition effects in the future.

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A model based investigation of the relative importance of CO2-fertilization, climate warming, nitrogen deposition and land use change on the global terrestrial carbon uptake in the historical period

Climate Dynamics ◽

10.1007/s00382-015-2830-8 ◽

2015 ◽

Vol 47 (1-2) ◽

pp. 173-190 ◽

Cited By ~ 28

Author(s):

N. Devaraju ◽

G. Bala ◽

K. Caldeira ◽

R. Nemani

Keyword(s):

Land Use ◽

Land Use Change ◽

Nitrogen Deposition ◽

Climate Warming ◽

Historical Period ◽

Carbon Uptake ◽

Relative Importance ◽

Terrestrial Carbon ◽

Co2 Fertilization ◽

Model Based

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Competing effects of nitrogen deposition and ozone exposure on northern hemispheric terrestrial carbon uptake and storage, 1850–2099

Biogeosciences ◽

10.5194/bg-18-3219-2021 ◽

2021 ◽

Vol 18 (10) ◽

pp. 3219-3241

Author(s):

Martina Franz ◽

Sönke Zaehle

Keyword(s):

Air Pollution ◽

East Asia ◽

Nitrogen Deposition ◽

Carbon Storage ◽

21St Century ◽

Detrimental Effect ◽

Carbon Uptake ◽

Terrestrial Carbon ◽

Northern Hemispheric ◽

And Storage

Abstract. Tropospheric ozone (O3) and nitrogen deposition affect vegetation growth and, thereby, the ability of the land biosphere to take up and store carbon. However, the magnitude of these effects on the contemporary and future terrestrial carbon balance is insufficiently understood. Here, we apply an extended version of the O–CN terrestrial biosphere model that simulates the atmosphere to canopy transport of O3, its surface and stomatal uptake, the O3-induced leaf injury, and the coupled terrestrial carbon and nitrogen cycles. We use this model to simulate past and future impacts of air pollution against a background of concurrent changes in climate and carbon dioxide concentrations (CO2) for two contrasting representative concentration pathway (RCP) scenarios (RCP2.6 and RCP8.5). The simulations show that O3-related damage considerably reduced northern hemispheric gross primary production (GPP) and long-term carbon storage between 1850 and the 2010s. The simulated O3 effect on GPP in the Northern Hemisphere peaked towards the end of the 20th century, with reductions of 4 %, causing a reduction in the northern hemispheric carbon sink of 0.4 Pg C yr−1. During the 21st century, O3-induced reductions in GPP and carbon storage are projected to decline, through a combination of direct air pollution control methods that reduce near-surface O3 and the indirect effects of rising atmospheric CO2, which reduces stomatal uptake of O3 concurrent with increases of leaf-level water use efficiency. However, in hot spot regions such as East Asia, the model simulations suggest a sustained decrease in GPP by more than 8 % throughout the 21st century. O3 exposure reduces projected carbon storage at the end of the 21st century by up to 15 % in parts of Europe, the US, and East Asia. Our simulations suggest that the stimulating effect of nitrogen deposition on regional GPP and carbon storage is lower in magnitude compared to the detrimental effect of O3 during most of the simulation period for both RCPs. In the second half of the 21st century, the detrimental effect of O3 on GPP is outweighed by nitrogen deposition, but the effect of nitrogen deposition on land carbon storage remains lower than the effect of O3. Accounting for the stimulating effects of nitrogen deposition but omitting the detrimental effect of O3 may lead to an overestimation of projected carbon uptake and storage.

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Potential roles of CO2 fertilization, nitrogen deposition, climate change, and land use and land cover change on the global terrestrial carbon uptake in the twenty-first century

Climate Dynamics ◽

10.1007/s00382-018-4388-8 ◽

2018 ◽

Vol 52 (7-8) ◽

pp. 4393-4406 ◽

Cited By ~ 10

Author(s):

Thejna Tharammal ◽

Govindasamy Bala ◽

Devaraju Narayanappa ◽

Ramakrishna Nemani

Keyword(s):

Climate Change ◽

Land Use ◽

Land Cover ◽

Nitrogen Deposition ◽

Land Cover Change ◽

First Century ◽

Carbon Uptake ◽

Terrestrial Carbon ◽

Co2 Fertilization ◽

Twenty First Century

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Competing effects of nitrogen deposition and ozone exposure on Northern hemispheric terrestrial carbon uptake and storage, 1850–2099

10.5194/bg-2020-443 ◽

2020 ◽

Author(s):

Martina Franz ◽

Sönke Zaehle

Keyword(s):

Air Pollution ◽

East Asia ◽

Nitrogen Deposition ◽

Carbon Storage ◽

Northern Hemisphere ◽

21St Century ◽

Ozone Exposure ◽

Carbon Uptake ◽

Northern Hemispheric ◽

And Storage

Abstract. Tropospheric ozone and nitrogen deposition affect vegetation growth and thus the ability of the land biosphere to store carbon. However, the magnitude of this effect on the contemporary and future terrestrial carbon balance is insufficiently understood. Here, we apply an extended version of the O-CN terrestrial biosphere model that simulates the atmosphere to canopy transport of O3, its surface and stomatal uptake, as well as the ozone-induced leaf injury. We use this model to simulate past and future impacts of air pollution (ozone and nitrogen deposition) against a background of concurrent changes in climate and carbon dioxide concentrations (CO2) for two contrasting representative concentration pathways (RCP) scenarios (RCP2.6 and RCP8.5). The simulations show that O3-related damage considerably reduced Northern hemispheric gross primary production (GPP) and long-term carbon storage between 1850 and the 2010s. The ozone effect on GPP in the Northern hemisphere peaks at the end of the 20th century with reductions of 4 %, causing a reduction in the Northern hemispheric carbon sink of 0.4 Pg C yr−1. During the 21st century, ozone-induced reductions in GPP and carbon storage is projected to decline through a combination of air pollution control methods that reduce tropospheric O3 and the indirect effects of rising atmospheric CO2, which reduces stomatal uptake of ozone concurrent with increases of leaf-level water-use efficiency. However, in hotspot regions such as East Asia, the model simulations suggest a sustained decrease of GPP by more than 8 % during the 21st century. Regionally, ozone exposure reduces carbon storage at the end of the 21st century by up to 15 % in parts of Europe, the US and East Asia. These estimates are lower compared to previous studies, which partially results from the explicit representation of non-stomatal ozone destruction, which considerably reduces simulated ozone uptake by leaves and incurred injury. Our simulations suggest that ozone damage largely offsets the growth stimulating effect induced by nitrogen deposition in the Northern hemisphere until the 2050s. Thus, accounting for the stimulating effects of nitrogen deposition but omitting the detrimental effect of O3 might lead to an over estimation of carbon uptake and storage.

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