Tuesday, 2 May 2023: 5:45 PM
Scandinavian Ballroom Salon 1-2 (Royal Sonesta Minneapolis Downtown )
It is well established that plant canopies exhibit increased light use efficiency (LUE) under higher
diffuse fraction, given constant total radiation. However, Southern pine forests have been largely
overlooked in these studies, despite the fact that nearly one-third of forested land in the United States
can be classified as Southern pine. Since this ecoregion contributes significantly to the national scale
terrestrial carbon sink and experiences high aerosol loading and cloudiness, increasing understanding
of diffuse light fertilization (DLF) could improve our ability to predict the climate mitigation potential
of Southeastern forests. Here we have determined the sensitivity of gross primary productivity (GPP) to
diffuse light by building remotely sensed LUE models that include increasingly explicit inputs of
diffuse light, from simple approximations, to actual measurements from a diffuse radiometer, across 4
Ameriflux registered Southern pine eddy covariance sites. Our results show that including diffuse light
measurements increased R2 and decreased RMSE values regardless of species or management stage,
illustrating a strong influence of DLF in Southern pine ecosystems. Additionally, we examined if the
magnitude of the diffuse fertilization effect remained consistent across variation in phenology and LAI,
as determined by locally installed Normalized Difference Vegetation Index (NDVI) sensors and
Sentinel-2 observations of enhanced vegetation index (EVI).
diffuse fraction, given constant total radiation. However, Southern pine forests have been largely
overlooked in these studies, despite the fact that nearly one-third of forested land in the United States
can be classified as Southern pine. Since this ecoregion contributes significantly to the national scale
terrestrial carbon sink and experiences high aerosol loading and cloudiness, increasing understanding
of diffuse light fertilization (DLF) could improve our ability to predict the climate mitigation potential
of Southeastern forests. Here we have determined the sensitivity of gross primary productivity (GPP) to
diffuse light by building remotely sensed LUE models that include increasingly explicit inputs of
diffuse light, from simple approximations, to actual measurements from a diffuse radiometer, across 4
Ameriflux registered Southern pine eddy covariance sites. Our results show that including diffuse light
measurements increased R2 and decreased RMSE values regardless of species or management stage,
illustrating a strong influence of DLF in Southern pine ecosystems. Additionally, we examined if the
magnitude of the diffuse fertilization effect remained consistent across variation in phenology and LAI,
as determined by locally installed Normalized Difference Vegetation Index (NDVI) sensors and
Sentinel-2 observations of enhanced vegetation index (EVI).
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