The blue carbon habitats are comprised of species of mangroves, seagrass, and marshes in the Gulf... more The blue carbon habitats are comprised of species of mangroves, seagrass, and marshes in the Gulf of Mexico (GoM), which grow profusely chiefly in estuaries, storing substantial sedimentary organic carbon of 605.5 to 615.4 Tg C. We have integrated new carbon investigations of buried organic carbon in Mexican mangroves, Louisiana marshes and seagrasses throughout the Gulf of Mexico to elucidate a new comparison of GoM carbon stock and portions of a flux estimate with Atlantic coastal carbon and other areas. We note the hydrospheric carbon flows from the watersheds into the GoM estuaries bring enriched carbon dioxide into the GoM basin. The mangroves' new results demonstrate sedimentary storage of the greatest amount of carbon (310.8Tg in first meter) in GoM mangroves, although seagrasses (greater than mangroves in extent) store 184.9Tg in their first meter. There is high variability up to 2100 Mgha-1 storage. GoM mangroves store carbon up to 6 m in depth, so the conservative amount reported is only a fraction of the storage in the comparative top meter. Marshes show highest carbon salt marsh storage in Louisiana, followed by lesser storage in Florida, Texas, then Mexico and equaling total marsh stock of 109.8-119.7Tg. The southeastern Mexican mangroves, experiencing higher winter temperatures than Florida and fewer extreme storms, especially show high productivity and very deep sediment Corg storage. This deep buried Carbon is not reflected in our estimates of the first meter of sediment. Partial fluxes for present new data are discussed as well as constraints on the carbon cycle of these ecosystems such as widespread anthropogenic destruction of blue carbon. Comparison of stocks with the Atlantic Coastal stock of North American is carried out. These sets of investigations were first assembled at the Botanical Society of America Symposium on Blue Carbon in the Gulf of Mexico.
A remote-sensing-based model to estimate evaporative fraction (EF)the ratio of latent heat (LE; e... more A remote-sensing-based model to estimate evaporative fraction (EF)the ratio of latent heat (LE; energy equivalent of evapotranspiration-ET-) to total available energyfrom easily obtainable remotely-sensed and meteorological parameters is presented. This research specifically addresses the shortcomings of existing ET retrieval methods such as calibration requirements of extensive accurate in situ micrometeorological and flux tower observations or of a large set of coarse-resolution or model-derived input datasets. The trapezoid model is capable of generating spatially varying EF maps from standard products such as land surface temperature (T s) normalized difference vegetation index (NDVI) and daily maximum air temperature (T a). The 2009 model results were validated at an eddy-covariance tower (Fluxnet ID: US-Skr) in the Everglades using T s and NDVI products from Landsat as well as the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors. Results indicate that the model accuracy is within the range of instrument uncertainty, and is dependent on the spatial resolution and selection of end-members (i.e. wet/dry edge). The most accurate results were achieved with the T s from Landsat relative to the T s from the MODIS flown on the Terra and Aqua platforms due to the fine spatial resolution of Landsat (30 m). The bias, mean absolute percentage error and root mean square percentage error were as low as 2.9% (3.0%), 9.8% (13.3%), and 12.1% (16.1%) for Landsat-based (MODIS-based) EF estimates, respectively. Overall, this methodology shows promise for bridging the gap between temporally limited ET estimates at Landsat scales and more complex and difficult to constrain global ET remote-sensing models.
Carbon dioxide exchange between the atmosphere and forested subtropical wetlands is largely unkno... more Carbon dioxide exchange between the atmosphere and forested subtropical wetlands is largely unknown. Here we report a first step in characterizing this atmosphericecosystem carbon (C) exchange, for cypress strands and pine forests in the Greater Everglades of Florida as measured with eddy covariance methods at three locations (Cypress Swamp, Dwarf Cypress and Pine Upland) for 2 years. Links between water and C cycles are also examined at these three sites, as are methane emission measured only at the Dwarf Cypress site. Each forested wetland showed net C uptake from the atmosphere both monthly and annually, as indicated by the net ecosystem exchange (NEE) of carbon dioxide (CO 2). For this study, NEE is the difference between photosynthesis and respiration, with negative values representing uptake from the atmosphere that is retained in the ecosystem or transported laterally via overland flow (unmeasured for this study). Atmospheric C uptake (NEE) was greatest at the Cypress Swampp (−900 to −1000 g C m 2 yr −1), moderate at the Pine Upland (−650 to −700 g C m 2 yr −1) and least at the Dwarf Cypress (−400 to −450 g C m 2 yr −1). Changes in NEE were clearly a function of seasonality in solar insolation, air temperature and flooding, which suppressed heterotrophic soil respiration. We also note that changes in the satellite-derived enhanced vegetation index (EVI) served as a useful surrogate for changes in NEE at these forested wetland sites.
The principal objective of this study is to investigate the radiative influences produced by phyt... more The principal objective of this study is to investigate the radiative influences produced by phytogenic aerosols over a forested area in eastern Canada where measured aerosol concentrations resulted from a-pinene and b-pinene oxidation processes. The studied forest ecosystem produced moderate amounts of biogenic hydrocarbons, with isoprene and pinene mixing ratios reaching 1.6 parts per billion. Once oxidized, these pinene levels gave rise to maximum phytogenic aerosol concentrations of circa 5000 particles per cm 3. The amount of diffuse and attenuated solar irradiance resulting from the interaction of aerosols with incoming irradiance was quantified using a one-dimensional spectral radiative transfer model and measured aerosol sized distributions and concentrations. Results show that aerosols in the atmospheric boundary layer contributed to only moderate levels of diffuse irradiance but generated substantial attenuation of the incoming solar irradiance stream. For the irradiance levels measured in eastern Canada during cloudless days in July and with aerosol concentrations in the range of 2000 to 5000 particles per cm 3 , average daytime solar irradiance attenuation amounted to 0.04 W m À2 with a diffuse component of 0.01 W m À2. The maximum solar irradiance extinction reached 0.2 W m À2. Assuming a uniform spatial aerosol distribution, this negative radiative influence could offset substantial fractions of the regional thermal forcing resulting from increased levels of greenhouse gases such as carbon dioxide. It is concluded that greater radiative influences (cooling) could be present over regions dominated by hydrocarbon productive forest ecosystems.
Above canopy measurements of carbon dioxide fluxes and sensible and latent heating were obtained ... more Above canopy measurements of carbon dioxide fluxes and sensible and latent heating were obtained with an open path eddy covariance system positioned on the tower at 26-m. Additionally, measurements of solar irradiance, wind speed, air temperature and humidity were made every half hour.
This is the AmeriFlux version of the carbon flux data for the site US-Skr Shark River Slough (Tow... more This is the AmeriFlux version of the carbon flux data for the site US-Skr Shark River Slough (Tower SRS-6) Everglades. Site Description - The Florida Everglades Shark River Slough Mangrove Forest site is located along the Shark River in the western region of Everglades National Park. Also referred to as site SRS6 of the Florida Coastal Everglades LTER program, freshwater in the mangrove riverine floods the forest floor under a meter of water twice per day. Transgressive discharge of freshwater from the Shark river follows annual rainfall distributions between the wet and dry seasons. Hurricane Wilma struck the site in October of 2005 causing significant damage. The tower was offline until the following October in order to continue temporally consistent measurements. In post-hurricane conditions, ecosystem respiration rates and solar irradiance transfer increased. 2007- 2008 measurements indicate that these factors led to an decline in both annual -NEE and daily NEE from pre-hurrican...
We analyzed the ecosystem effects of lowtemperature events (<5°C) over 4 years (2009-2012) in sub... more We analyzed the ecosystem effects of lowtemperature events (<5°C) over 4 years (2009-2012) in subtropical short and long hydroperiod freshwater marsh and mangrove forests within Everglades National Park. To evaluate changes in ecosystem productivity, we measured temporal patterns of CO 2 and the normalized difference vegetation index over the study period. Both water levels and distance from the coast influenced the ecosystem response to lowtemperature events. Photosynthetic capacity, or the maximum CO 2 uptake rate, and sensitivity to low-temperature events were much higher in mangrove forest than in freshwater marsh ecosystems. During low-temperature events photosynthetic capacity was enhanced in freshwater marsh while it declined in mangrove forests, and respiration rates declined across Everglades ecosystems. While the long hydroperiod freshwater marsh gained 0.26 g CO 2 m −2 during lowtemperature events, the mangrove forest had the greatest C lost (7.11 g CO 2 m −2 low-temperature event −1) followed by the short hydroperiod freshwater marsh (0.37 g CO 2 m −2 lowtemperature event −1). Results suggest that shifts in the frequency and intensity of weather anomalies with climate change can alter C assimilation rates in Everglades ecosystems through effects on the photosynthetic capacity of existing species, which might lead to changes in species composition and ecosystem productivity in the future. Keywords Low-temperature events. Everglades National Park. Ecosystem sensitivity. CO 2 fluxes. Eddy covariance. ARIMA models
During the 2004 growing season a field investigation was conducted in the western Florida coastal... more During the 2004 growing season a field investigation was conducted in the western Florida coastal Everglades to determine the amount of atmospheric carbon dioxide assimilated by the mangrove forests. Ecosystem-level carbon assimilation rates were determined with observing systems deployed on a tower extending several meters above the forest canopy. The results indicate that the mangrove forests are very efficient ecosystems in terms of their ability to consume atmospheric carbon dioxide. It is estimated that the mangroves consume 7-9 tons of carbon per hectare per year. Mangrove forests exhibit unusually high carbon assimilation rates in response to favorable year-round growing conditions and effective forest-atmosphere feedbacks such as high irradiance use efficiency during partly cloudy conditions. The present investigation provides important baseline knowledge of the functioning of the mangrove forests in the Everglades under the current perturbed water flow conditions. This know...
Although south Florida is subtropical with mild winters, severe cold weather can occur when the p... more Although south Florida is subtropical with mild winters, severe cold weather can occur when the polar jet stream moves towards the southern region of the US. Here, the frequency and intensity of cold events are important when considering species and ecosystem distributions across the landscape. To determine the vulnerability of Everglades ecosystems to low temperatures, we compared changes in ecosystem CO2 exchange rates in short- (25.4238, -80.5902) and long-hydroperiod (25.5497, -80.7852) freshwater marsh and in mangrove ecosystems (25.4238, -80.5902) during cold events (<5°C) over 4 years (2009 to 2012). Preliminary results suggest that water levels may be important for low temperature events, where the moisture flux serves to prevent the development of below-freezing temperatures. Generally, within the Everglades the frequency and intensity of cold events declines with water levels as you move south. As a result of the spatial patterns in temperature extremes, the short-hydro...
Despite the importance of mangrove ecosystems in the global carbon budget, the relationships betw... more Despite the importance of mangrove ecosystems in the global carbon budget, the relationships between environmental drivers and carbon dynamics in these forests remain poorly understood. This limited understanding is partly a result of the challenges associated with in situ flux studies. Tower-based carbon dioxide eddy covariance (EC) systems are installed in only a few mangrove forests worldwide and the longest EC record from the Florida Everglades contains less than 9 yr of observations. A primary goal of the present study was to develop a methodology to estimate canopy-scale photosynthetic light use efficiency in this forest. These tower-based observations represent a basis for associating CO 2 fluxes with canopy light use properties, and thus provide the means for utilizing satellite-based reflectance data for larger-scale investigations. We present a model for mangrove canopy light use efficiency utilizing the enhanced green vegetation index (EVI) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) that is capable of predicting changes in mangrove forest CO 2 fluxes caused by a hurricane disturbance and changes in regional environmental conditions, including temperature and salinity. Model parameters are solved for in a Bayesian framework. The model structure requires estimates of ecosystem respiration (R E) and we present the first-ever tower-based estimates of mangrove forest R E derived from night-time CO 2 fluxes. Our investigation is also the first to show the effects of salinity on mangrove forest CO 2 uptake, which declines 5 % per each 10 parts per thousand (ppt) increases in salinity. Light use efficiency in this forest declines with increasing daily photosynthetic active radiation, which is an important departure from the assumption of constant light use efficiency typically applied in satellite-driven models. The model developed here provides a framework for estimating CO 2 uptake by these forests from reflectance data and information about environmental conditions.
The blue carbon habitats are comprised of species of mangroves, seagrass, and marshes in the Gulf... more The blue carbon habitats are comprised of species of mangroves, seagrass, and marshes in the Gulf of Mexico (GoM), which grow profusely chiefly in estuaries, storing substantial sedimentary organic carbon of 605.5 to 615.4 Tg C. We have integrated new carbon investigations of buried organic carbon in Mexican mangroves, Louisiana marshes and seagrasses throughout the Gulf of Mexico to elucidate a new comparison of GoM carbon stock and portions of a flux estimate with Atlantic coastal carbon and other areas. We note the hydrospheric carbon flows from the watersheds into the GoM estuaries bring enriched carbon dioxide into the GoM basin. The mangroves' new results demonstrate sedimentary storage of the greatest amount of carbon (310.8Tg in first meter) in GoM mangroves, although seagrasses (greater than mangroves in extent) store 184.9Tg in their first meter. There is high variability up to 2100 Mgha-1 storage. GoM mangroves store carbon up to 6 m in depth, so the conservative amount reported is only a fraction of the storage in the comparative top meter. Marshes show highest carbon salt marsh storage in Louisiana, followed by lesser storage in Florida, Texas, then Mexico and equaling total marsh stock of 109.8-119.7Tg. The southeastern Mexican mangroves, experiencing higher winter temperatures than Florida and fewer extreme storms, especially show high productivity and very deep sediment Corg storage. This deep buried Carbon is not reflected in our estimates of the first meter of sediment. Partial fluxes for present new data are discussed as well as constraints on the carbon cycle of these ecosystems such as widespread anthropogenic destruction of blue carbon. Comparison of stocks with the Atlantic Coastal stock of North American is carried out. These sets of investigations were first assembled at the Botanical Society of America Symposium on Blue Carbon in the Gulf of Mexico.
A remote-sensing-based model to estimate evaporative fraction (EF)the ratio of latent heat (LE; e... more A remote-sensing-based model to estimate evaporative fraction (EF)the ratio of latent heat (LE; energy equivalent of evapotranspiration-ET-) to total available energyfrom easily obtainable remotely-sensed and meteorological parameters is presented. This research specifically addresses the shortcomings of existing ET retrieval methods such as calibration requirements of extensive accurate in situ micrometeorological and flux tower observations or of a large set of coarse-resolution or model-derived input datasets. The trapezoid model is capable of generating spatially varying EF maps from standard products such as land surface temperature (T s) normalized difference vegetation index (NDVI) and daily maximum air temperature (T a). The 2009 model results were validated at an eddy-covariance tower (Fluxnet ID: US-Skr) in the Everglades using T s and NDVI products from Landsat as well as the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors. Results indicate that the model accuracy is within the range of instrument uncertainty, and is dependent on the spatial resolution and selection of end-members (i.e. wet/dry edge). The most accurate results were achieved with the T s from Landsat relative to the T s from the MODIS flown on the Terra and Aqua platforms due to the fine spatial resolution of Landsat (30 m). The bias, mean absolute percentage error and root mean square percentage error were as low as 2.9% (3.0%), 9.8% (13.3%), and 12.1% (16.1%) for Landsat-based (MODIS-based) EF estimates, respectively. Overall, this methodology shows promise for bridging the gap between temporally limited ET estimates at Landsat scales and more complex and difficult to constrain global ET remote-sensing models.
Carbon dioxide exchange between the atmosphere and forested subtropical wetlands is largely unkno... more Carbon dioxide exchange between the atmosphere and forested subtropical wetlands is largely unknown. Here we report a first step in characterizing this atmosphericecosystem carbon (C) exchange, for cypress strands and pine forests in the Greater Everglades of Florida as measured with eddy covariance methods at three locations (Cypress Swamp, Dwarf Cypress and Pine Upland) for 2 years. Links between water and C cycles are also examined at these three sites, as are methane emission measured only at the Dwarf Cypress site. Each forested wetland showed net C uptake from the atmosphere both monthly and annually, as indicated by the net ecosystem exchange (NEE) of carbon dioxide (CO 2). For this study, NEE is the difference between photosynthesis and respiration, with negative values representing uptake from the atmosphere that is retained in the ecosystem or transported laterally via overland flow (unmeasured for this study). Atmospheric C uptake (NEE) was greatest at the Cypress Swampp (−900 to −1000 g C m 2 yr −1), moderate at the Pine Upland (−650 to −700 g C m 2 yr −1) and least at the Dwarf Cypress (−400 to −450 g C m 2 yr −1). Changes in NEE were clearly a function of seasonality in solar insolation, air temperature and flooding, which suppressed heterotrophic soil respiration. We also note that changes in the satellite-derived enhanced vegetation index (EVI) served as a useful surrogate for changes in NEE at these forested wetland sites.
The principal objective of this study is to investigate the radiative influences produced by phyt... more The principal objective of this study is to investigate the radiative influences produced by phytogenic aerosols over a forested area in eastern Canada where measured aerosol concentrations resulted from a-pinene and b-pinene oxidation processes. The studied forest ecosystem produced moderate amounts of biogenic hydrocarbons, with isoprene and pinene mixing ratios reaching 1.6 parts per billion. Once oxidized, these pinene levels gave rise to maximum phytogenic aerosol concentrations of circa 5000 particles per cm 3. The amount of diffuse and attenuated solar irradiance resulting from the interaction of aerosols with incoming irradiance was quantified using a one-dimensional spectral radiative transfer model and measured aerosol sized distributions and concentrations. Results show that aerosols in the atmospheric boundary layer contributed to only moderate levels of diffuse irradiance but generated substantial attenuation of the incoming solar irradiance stream. For the irradiance levels measured in eastern Canada during cloudless days in July and with aerosol concentrations in the range of 2000 to 5000 particles per cm 3 , average daytime solar irradiance attenuation amounted to 0.04 W m À2 with a diffuse component of 0.01 W m À2. The maximum solar irradiance extinction reached 0.2 W m À2. Assuming a uniform spatial aerosol distribution, this negative radiative influence could offset substantial fractions of the regional thermal forcing resulting from increased levels of greenhouse gases such as carbon dioxide. It is concluded that greater radiative influences (cooling) could be present over regions dominated by hydrocarbon productive forest ecosystems.
Above canopy measurements of carbon dioxide fluxes and sensible and latent heating were obtained ... more Above canopy measurements of carbon dioxide fluxes and sensible and latent heating were obtained with an open path eddy covariance system positioned on the tower at 26-m. Additionally, measurements of solar irradiance, wind speed, air temperature and humidity were made every half hour.
This is the AmeriFlux version of the carbon flux data for the site US-Skr Shark River Slough (Tow... more This is the AmeriFlux version of the carbon flux data for the site US-Skr Shark River Slough (Tower SRS-6) Everglades. Site Description - The Florida Everglades Shark River Slough Mangrove Forest site is located along the Shark River in the western region of Everglades National Park. Also referred to as site SRS6 of the Florida Coastal Everglades LTER program, freshwater in the mangrove riverine floods the forest floor under a meter of water twice per day. Transgressive discharge of freshwater from the Shark river follows annual rainfall distributions between the wet and dry seasons. Hurricane Wilma struck the site in October of 2005 causing significant damage. The tower was offline until the following October in order to continue temporally consistent measurements. In post-hurricane conditions, ecosystem respiration rates and solar irradiance transfer increased. 2007- 2008 measurements indicate that these factors led to an decline in both annual -NEE and daily NEE from pre-hurrican...
We analyzed the ecosystem effects of lowtemperature events (<5°C) over 4 years (2009-2012) in sub... more We analyzed the ecosystem effects of lowtemperature events (<5°C) over 4 years (2009-2012) in subtropical short and long hydroperiod freshwater marsh and mangrove forests within Everglades National Park. To evaluate changes in ecosystem productivity, we measured temporal patterns of CO 2 and the normalized difference vegetation index over the study period. Both water levels and distance from the coast influenced the ecosystem response to lowtemperature events. Photosynthetic capacity, or the maximum CO 2 uptake rate, and sensitivity to low-temperature events were much higher in mangrove forest than in freshwater marsh ecosystems. During low-temperature events photosynthetic capacity was enhanced in freshwater marsh while it declined in mangrove forests, and respiration rates declined across Everglades ecosystems. While the long hydroperiod freshwater marsh gained 0.26 g CO 2 m −2 during lowtemperature events, the mangrove forest had the greatest C lost (7.11 g CO 2 m −2 low-temperature event −1) followed by the short hydroperiod freshwater marsh (0.37 g CO 2 m −2 lowtemperature event −1). Results suggest that shifts in the frequency and intensity of weather anomalies with climate change can alter C assimilation rates in Everglades ecosystems through effects on the photosynthetic capacity of existing species, which might lead to changes in species composition and ecosystem productivity in the future. Keywords Low-temperature events. Everglades National Park. Ecosystem sensitivity. CO 2 fluxes. Eddy covariance. ARIMA models
During the 2004 growing season a field investigation was conducted in the western Florida coastal... more During the 2004 growing season a field investigation was conducted in the western Florida coastal Everglades to determine the amount of atmospheric carbon dioxide assimilated by the mangrove forests. Ecosystem-level carbon assimilation rates were determined with observing systems deployed on a tower extending several meters above the forest canopy. The results indicate that the mangrove forests are very efficient ecosystems in terms of their ability to consume atmospheric carbon dioxide. It is estimated that the mangroves consume 7-9 tons of carbon per hectare per year. Mangrove forests exhibit unusually high carbon assimilation rates in response to favorable year-round growing conditions and effective forest-atmosphere feedbacks such as high irradiance use efficiency during partly cloudy conditions. The present investigation provides important baseline knowledge of the functioning of the mangrove forests in the Everglades under the current perturbed water flow conditions. This know...
Although south Florida is subtropical with mild winters, severe cold weather can occur when the p... more Although south Florida is subtropical with mild winters, severe cold weather can occur when the polar jet stream moves towards the southern region of the US. Here, the frequency and intensity of cold events are important when considering species and ecosystem distributions across the landscape. To determine the vulnerability of Everglades ecosystems to low temperatures, we compared changes in ecosystem CO2 exchange rates in short- (25.4238, -80.5902) and long-hydroperiod (25.5497, -80.7852) freshwater marsh and in mangrove ecosystems (25.4238, -80.5902) during cold events (<5°C) over 4 years (2009 to 2012). Preliminary results suggest that water levels may be important for low temperature events, where the moisture flux serves to prevent the development of below-freezing temperatures. Generally, within the Everglades the frequency and intensity of cold events declines with water levels as you move south. As a result of the spatial patterns in temperature extremes, the short-hydro...
Despite the importance of mangrove ecosystems in the global carbon budget, the relationships betw... more Despite the importance of mangrove ecosystems in the global carbon budget, the relationships between environmental drivers and carbon dynamics in these forests remain poorly understood. This limited understanding is partly a result of the challenges associated with in situ flux studies. Tower-based carbon dioxide eddy covariance (EC) systems are installed in only a few mangrove forests worldwide and the longest EC record from the Florida Everglades contains less than 9 yr of observations. A primary goal of the present study was to develop a methodology to estimate canopy-scale photosynthetic light use efficiency in this forest. These tower-based observations represent a basis for associating CO 2 fluxes with canopy light use properties, and thus provide the means for utilizing satellite-based reflectance data for larger-scale investigations. We present a model for mangrove canopy light use efficiency utilizing the enhanced green vegetation index (EVI) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) that is capable of predicting changes in mangrove forest CO 2 fluxes caused by a hurricane disturbance and changes in regional environmental conditions, including temperature and salinity. Model parameters are solved for in a Bayesian framework. The model structure requires estimates of ecosystem respiration (R E) and we present the first-ever tower-based estimates of mangrove forest R E derived from night-time CO 2 fluxes. Our investigation is also the first to show the effects of salinity on mangrove forest CO 2 uptake, which declines 5 % per each 10 parts per thousand (ppt) increases in salinity. Light use efficiency in this forest declines with increasing daily photosynthetic active radiation, which is an important departure from the assumption of constant light use efficiency typically applied in satellite-driven models. The model developed here provides a framework for estimating CO 2 uptake by these forests from reflectance data and information about environmental conditions.
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Papers by Jordan Barr