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TitleImproving a biogeochemical model to simulate surface energy, greenhouse gas fluxes, and radiative forcing for different land use types in northeastern United States
AuthorDeng, J; Xiao, J; Ouimette, A; Zhang, YORCID logo; Sanders-DeMott, R; Frolking, S; Li, C
SourceGlobal Biogeochemical Cycles vol. 34, issue 8, e2019GB006520, 2020 p. 1-23,
Alt SeriesNatural Resources Canada, Contribution Series 20200404
PublisherBlackwell Publishing Ltd.
Mediapaper; on-line; digital
File formatpdf; html
AreaNew Hampshire; United States of America
Lat/Long WENS -70.9667 -70.9167 43.1833 43.1000
Subjectsgeochemistry; Nature and Environment; Science and Technology; Agriculture; land use; biogeochemistry; models; computer simulations; climate effects; ecosystems; vegetation; Greenhouse gases; cumulative effects; Climate change; Forests
Illustrationsflow diagrams; tables; time series; plots
ProgramCanada Centre for Remote Sensing Optical methods and applications
Released2020 07 27
AbstractLand use changes exert important impacts on climate, primarily through altering greenhouse gas (GHG) and surface energy fluxes. Biogeochemical models have incorporated a relatively complete suite of biogeochemical processes to simulate GHG fluxes. However, these models often lack detailed processes of surface energy exchange, limiting their ability to assess the impacts of land use change on climate. In this study, we incorporated processes of surface energy exchange into a widely used biogeochemistry model, DeNitrification-DeComposition (DNDC), so that it can quantify both GHG and energy fluxes between the biosphere and the atmosphere. When tested against field observations for the three dominant land use types (forest, hayfield, and cornfield) in the northeastern United States, the improved DNDC successfully captured the observed fluxes of outgoing shortwave radiation, latent heat, sensible heat, net ecosystem exchange of CO2, and their differences among the three land use types. To evaluate the differences in radiative forcing among these land use types, we conducted 100-year simulations and converted the modeled GHG fluxes to radiative forcing using an atmospheric impulse response model. Our results show that the 100-year cumulative differences in net radiative forcing are 3.35 nW m-2 between the hayfield and forest (slight warming) and 43.2 nW m-2 between the cornfield and forest (warming) per hectare land use difference. The cooling effects of increased albedo after the conversion of forest to hayfield or cornfield (observed and modeled in recent years) are gradually offset by the warming effects of the increasing release of GHG as the forest becomes older.
Summary(Plain Language Summary, not published)
This study focuses on the impact of changes in land use on climate. Land use changes can affect the climate by altering the release of greenhouse gases (GHGs) and how energy flows between the Earth's surface and the atmosphere. While biogeochemical models have been developed to simulate GHG fluxes, they often lack the ability to account for detailed processes related to energy exchange between the land surface and the atmosphere.
To address this, the researchers enhanced a widely used biogeochemistry model called DeNitrification-DeComposition (DNDC) to include processes related to surface energy exchange. They tested this improved model using data from different types of land use in the northeastern United States, such as forests, hayfields, and cornfields. The model successfully replicated observations of various fluxes, including energy and GHGs.
The study's simulations over a 100-year period revealed differences in radiative forcing, a measure of how land use changes impact the Earth's energy balance. The results indicated that converting forests to hayfields or cornfields can initially lead to cooling effects due to increased reflectivity (albedo). However, these cooling effects are gradually outweighed by warming effects caused by the release of GHGs as forests age.
Understanding these complex interactions between land use changes, energy fluxes, and GHG emissions is crucial for addressing climate change. It provides valuable insights for land management and policy decisions to mitigate the impact of human activities on the environment.

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