Investigating sources of measured forest-atmosphere ammonia fluxes using two-layer bi-directional modelling

K. Hansen; E Personne; C. A. Skjoth; B. Loubet; Andreas Ibrom; R. Jensen; L. L. Sorensen; E. Boegh

doi:10.1016/j.agrformet.2017.02.008

Investigating sources of measured forest-atmosphere ammonia fluxes using two-layer bi-directional modelling

K. Hansen^*, E Personne, C. A. Skjoth, B. Loubet, Andreas Ibrom, R. Jensen, L. L. Sorensen, E. Boegh

^*Corresponding author af dette arbejde

Arctic Research Centre

Publikation: Bidrag til tidsskrift/Konferencebidrag i tidsskrift /Bidrag til avis › Tidsskriftartikel › Forskning › peer review

Abstract

Understanding and predicting the ammonia (NH ₃) exchange between the biosphere and the atmosphere is important due to the environmental consequences of the presence of reactive nitrogen (N _r) in the environment. The dynamics of the natural sources are, however, not well understood, especially not for forest ecosystems due to the complex nature of this soil-vegetation-atmosphere system. Furthermore, the high reactivity of NH ₃ makes it technically complex and expensive to measure and understand the forest-atmospheric NH ₃ exchange. The aim of this study is to investigate the NH ₃ flux partitioning between the ground layer, cuticle and stomata compartments for two temperate deciduous forest ecosystems located in Midwestern, USA (MMSF) and in Denmark (DK-Sor). This study is based on measurements and simulations of the surface energy balance, fluxes of CO ₂ and NH ₃ during two contrasted periods of the forest ecosystems, a period with full developed canopy (MMSF) and a senescent period for the DK-Sor site, with leaf fall and leaf litter build-up. Both datasets indicate emissions of NH ₃ from the forest to the atmosphere. The two-layer NH ₃ compensation point model SURFATM-NH ₃ was used in combination with a coupled photosynthesis-stomatal conductance model to represent seasonal variation in canopy physiological activity for simulating both net ecosystem CO ₂ exchange rates (R ² = 0.77 for MMSF and R ² = 0.84 for DK-Sor) and atmospheric NH ₃ fluxes (R ² = 0.43 for MMSF and R ² = 0.60 for DK-Sor). A scaling of the ground layer NH ₃ emission potential (Г _g) was successfully applied using the plant area index (PAI) to represent the build-up of a litter layer in the leaf fall period. For a closed green forest canopy (MMSF), unaffected by agricultural NH ₃ sources, NH ₃ was emitted with daytime fluxes up to 50 ng NH ₃-N m ⁻² s ⁻¹ and nighttime fluxes up to 30 ng NH ₃-N m ⁻² s ⁻¹. For a senescing forest (DK-Sor), located in an agricultural region, deposition rates of 250 ng NH ₃-N m ⁻² s ⁻¹ were measured prior to leaf fall, and emission rates up to 670 ng NH ₃-N m ⁻² s ⁻¹ were measured following leaf fall. For MMSF, simulated stomatal NH ₃ emissions explain the daytime flux observations well, and it is hypothesized that cuticular desorption is responsible for the observed NH ₃ emissions at night. During leaf fall in DK-Sor, ground fluxes dominate the NH ₃ flux with a mean emission rate of 150 ng NH ₃-N m ⁻² s ⁻¹. This study shows that forests potentially comprise a natural source of NH ₃ to the atmosphere, and that it is crucial to take into account the bi-directional exchange processes related to both the stomatal, cuticular and ground layer pathways in order to realistically simulate forest–atmosphere fluxes of NH ₃.

Originalsprog	Engelsk
Tidsskrift	Agricultural and Forest Meteorology
Vol/bind	237-238
Sider (fra-til)	80-94
Antal sider	15
ISSN	0168-1923
DOI	https://doi.org/10.1016/j.agrformet.2017.02.008
Status	Udgivet - maj 2017

Adgang til dokumentet

10.1016/j.agrformet.2017.02.008

Andre filer og links

Link to publication in Scopus

Citationsformater

@article{7da40409c42b4e09a76d78e1f8c5cf7f,

title = "Investigating sources of measured forest-atmosphere ammonia fluxes using two-layer bi-directional modelling",

abstract = "Understanding and predicting the ammonia (NH 3) exchange between the biosphere and the atmosphere is important due to the environmental consequences of the presence of reactive nitrogen (N r) in the environment. The dynamics of the natural sources are, however, not well understood, especially not for forest ecosystems due to the complex nature of this soil-vegetation-atmosphere system. Furthermore, the high reactivity of NH 3 makes it technically complex and expensive to measure and understand the forest-atmospheric NH 3 exchange. The aim of this study is to investigate the NH 3 flux partitioning between the ground layer, cuticle and stomata compartments for two temperate deciduous forest ecosystems located in Midwestern, USA (MMSF) and in Denmark (DK-Sor). This study is based on measurements and simulations of the surface energy balance, fluxes of CO 2 and NH 3 during two contrasted periods of the forest ecosystems, a period with full developed canopy (MMSF) and a senescent period for the DK-Sor site, with leaf fall and leaf litter build-up. Both datasets indicate emissions of NH 3 from the forest to the atmosphere. The two-layer NH 3 compensation point model SURFATM-NH 3 was used in combination with a coupled photosynthesis-stomatal conductance model to represent seasonal variation in canopy physiological activity for simulating both net ecosystem CO 2 exchange rates (R 2 = 0.77 for MMSF and R 2 = 0.84 for DK-Sor) and atmospheric NH 3 fluxes (R 2 = 0.43 for MMSF and R 2 = 0.60 for DK-Sor). A scaling of the ground layer NH 3 emission potential (Г g) was successfully applied using the plant area index (PAI) to represent the build-up of a litter layer in the leaf fall period. For a closed green forest canopy (MMSF), unaffected by agricultural NH 3 sources, NH 3 was emitted with daytime fluxes up to 50 ng NH 3-N m −2 s −1 and nighttime fluxes up to 30 ng NH 3-N m −2 s −1. For a senescing forest (DK-Sor), located in an agricultural region, deposition rates of 250 ng NH 3-N m −2 s −1 were measured prior to leaf fall, and emission rates up to 670 ng NH 3-N m −2 s −1 were measured following leaf fall. For MMSF, simulated stomatal NH 3 emissions explain the daytime flux observations well, and it is hypothesized that cuticular desorption is responsible for the observed NH 3 emissions at night. During leaf fall in DK-Sor, ground fluxes dominate the NH 3 flux with a mean emission rate of 150 ng NH 3-N m −2 s −1. This study shows that forests potentially comprise a natural source of NH 3 to the atmosphere, and that it is crucial to take into account the bi-directional exchange processes related to both the stomatal, cuticular and ground layer pathways in order to realistically simulate forest–atmosphere fluxes of NH 3.",

keywords = "Ammonia, Biosphere atmosphere exchanges, Compensation point, Deciduous forest, Measurements, Modelling, INTENSIVELY MANAGED GRASSLAND, IASI SATELLITE-OBSERVATIONS, NET ECOSYSTEM EXCHANGE, AIR-QUALITY MODEL, COMPENSATION POINT, REACTIVE NITROGEN, DECIDUOUS FOREST, OILSEED RAPE, PHYSIOLOGICAL-PARAMETERS, STOMATAL CONDUCTANCE",

author = "K. Hansen and E Personne and Skjoth, {C. A.} and B. Loubet and Andreas Ibrom and R. Jensen and Sorensen, {L. L.} and E. Boegh",

year = "2017",

month = may,

doi = "10.1016/j.agrformet.2017.02.008",

language = "English",

volume = "237-238",

pages = "80--94",

journal = "Agricultural and Forest Meteorology",

issn = "0168-1923",

publisher = "Elsevier BV",

}

TY - JOUR

T1 - Investigating sources of measured forest-atmosphere ammonia fluxes using two-layer bi-directional modelling

AU - Hansen, K.

AU - Personne, E

AU - Skjoth, C. A.

AU - Loubet, B.

AU - Ibrom, Andreas

AU - Jensen, R.

AU - Sorensen, L. L.

AU - Boegh, E.

PY - 2017/5

Y1 - 2017/5

N2 - Understanding and predicting the ammonia (NH 3) exchange between the biosphere and the atmosphere is important due to the environmental consequences of the presence of reactive nitrogen (N r) in the environment. The dynamics of the natural sources are, however, not well understood, especially not for forest ecosystems due to the complex nature of this soil-vegetation-atmosphere system. Furthermore, the high reactivity of NH 3 makes it technically complex and expensive to measure and understand the forest-atmospheric NH 3 exchange. The aim of this study is to investigate the NH 3 flux partitioning between the ground layer, cuticle and stomata compartments for two temperate deciduous forest ecosystems located in Midwestern, USA (MMSF) and in Denmark (DK-Sor). This study is based on measurements and simulations of the surface energy balance, fluxes of CO 2 and NH 3 during two contrasted periods of the forest ecosystems, a period with full developed canopy (MMSF) and a senescent period for the DK-Sor site, with leaf fall and leaf litter build-up. Both datasets indicate emissions of NH 3 from the forest to the atmosphere. The two-layer NH 3 compensation point model SURFATM-NH 3 was used in combination with a coupled photosynthesis-stomatal conductance model to represent seasonal variation in canopy physiological activity for simulating both net ecosystem CO 2 exchange rates (R 2 = 0.77 for MMSF and R 2 = 0.84 for DK-Sor) and atmospheric NH 3 fluxes (R 2 = 0.43 for MMSF and R 2 = 0.60 for DK-Sor). A scaling of the ground layer NH 3 emission potential (Г g) was successfully applied using the plant area index (PAI) to represent the build-up of a litter layer in the leaf fall period. For a closed green forest canopy (MMSF), unaffected by agricultural NH 3 sources, NH 3 was emitted with daytime fluxes up to 50 ng NH 3-N m −2 s −1 and nighttime fluxes up to 30 ng NH 3-N m −2 s −1. For a senescing forest (DK-Sor), located in an agricultural region, deposition rates of 250 ng NH 3-N m −2 s −1 were measured prior to leaf fall, and emission rates up to 670 ng NH 3-N m −2 s −1 were measured following leaf fall. For MMSF, simulated stomatal NH 3 emissions explain the daytime flux observations well, and it is hypothesized that cuticular desorption is responsible for the observed NH 3 emissions at night. During leaf fall in DK-Sor, ground fluxes dominate the NH 3 flux with a mean emission rate of 150 ng NH 3-N m −2 s −1. This study shows that forests potentially comprise a natural source of NH 3 to the atmosphere, and that it is crucial to take into account the bi-directional exchange processes related to both the stomatal, cuticular and ground layer pathways in order to realistically simulate forest–atmosphere fluxes of NH 3.

AB - Understanding and predicting the ammonia (NH 3) exchange between the biosphere and the atmosphere is important due to the environmental consequences of the presence of reactive nitrogen (N r) in the environment. The dynamics of the natural sources are, however, not well understood, especially not for forest ecosystems due to the complex nature of this soil-vegetation-atmosphere system. Furthermore, the high reactivity of NH 3 makes it technically complex and expensive to measure and understand the forest-atmospheric NH 3 exchange. The aim of this study is to investigate the NH 3 flux partitioning between the ground layer, cuticle and stomata compartments for two temperate deciduous forest ecosystems located in Midwestern, USA (MMSF) and in Denmark (DK-Sor). This study is based on measurements and simulations of the surface energy balance, fluxes of CO 2 and NH 3 during two contrasted periods of the forest ecosystems, a period with full developed canopy (MMSF) and a senescent period for the DK-Sor site, with leaf fall and leaf litter build-up. Both datasets indicate emissions of NH 3 from the forest to the atmosphere. The two-layer NH 3 compensation point model SURFATM-NH 3 was used in combination with a coupled photosynthesis-stomatal conductance model to represent seasonal variation in canopy physiological activity for simulating both net ecosystem CO 2 exchange rates (R 2 = 0.77 for MMSF and R 2 = 0.84 for DK-Sor) and atmospheric NH 3 fluxes (R 2 = 0.43 for MMSF and R 2 = 0.60 for DK-Sor). A scaling of the ground layer NH 3 emission potential (Г g) was successfully applied using the plant area index (PAI) to represent the build-up of a litter layer in the leaf fall period. For a closed green forest canopy (MMSF), unaffected by agricultural NH 3 sources, NH 3 was emitted with daytime fluxes up to 50 ng NH 3-N m −2 s −1 and nighttime fluxes up to 30 ng NH 3-N m −2 s −1. For a senescing forest (DK-Sor), located in an agricultural region, deposition rates of 250 ng NH 3-N m −2 s −1 were measured prior to leaf fall, and emission rates up to 670 ng NH 3-N m −2 s −1 were measured following leaf fall. For MMSF, simulated stomatal NH 3 emissions explain the daytime flux observations well, and it is hypothesized that cuticular desorption is responsible for the observed NH 3 emissions at night. During leaf fall in DK-Sor, ground fluxes dominate the NH 3 flux with a mean emission rate of 150 ng NH 3-N m −2 s −1. This study shows that forests potentially comprise a natural source of NH 3 to the atmosphere, and that it is crucial to take into account the bi-directional exchange processes related to both the stomatal, cuticular and ground layer pathways in order to realistically simulate forest–atmosphere fluxes of NH 3.

KW - Ammonia

KW - Biosphere atmosphere exchanges

KW - Compensation point

KW - Deciduous forest

KW - Measurements

KW - Modelling

KW - INTENSIVELY MANAGED GRASSLAND

KW - IASI SATELLITE-OBSERVATIONS

KW - NET ECOSYSTEM EXCHANGE

KW - AIR-QUALITY MODEL

KW - COMPENSATION POINT

KW - REACTIVE NITROGEN

KW - DECIDUOUS FOREST

KW - OILSEED RAPE

KW - PHYSIOLOGICAL-PARAMETERS

KW - STOMATAL CONDUCTANCE

UR - http://www.scopus.com/inward/record.url?scp=85012041130&partnerID=8YFLogxK

U2 - 10.1016/j.agrformet.2017.02.008

DO - 10.1016/j.agrformet.2017.02.008

M3 - Journal article

SN - 0168-1923

VL - 237-238

SP - 80

EP - 94

JO - Agricultural and Forest Meteorology

JF - Agricultural and Forest Meteorology

ER -

Investigating sources of measured forest-atmosphere ammonia fluxes using two-layer bi-directional modelling

Abstract

Adgang til dokumentet

Andre filer og links

Fingeraftryk

Citationsformater