Geology topics

Frank E. Anderson

Publications and source records attributed to Frank E. Anderson.

5 recordsLinked to original sources

USGS2021

Carbon fluxes and potential soil accumulation within Greater Everglades cypress and pine forested wetlands

In forested wetlands, accumulation of organic matter in soil is partly governed by carbon fluxes where photosynthesis, respiration, lateral advection of waterborne carbon, fire-derived carbon emissions, and methanogenesis are balanced by changes in stored carbon. Stored carbon can eventually accumulate as soil over time if net primary productivity exceeds biomass decomposition. For this study, potential soil accumulation was estimated based on four years of continuous daily carbon cycling data and a one-dimensional mass-balance model of landscape-atmospheric exchange for cypress and pine forested wetlands in the Greater Everglades of south Florida. The mass-balance model was driven by eddy-covariance estimates of vertical net ecosystem exchange of carbon dioxide and methane. Key findings include confirmation of a basic premise of the historic Everglades restoration project; specifically, more water either from rainfall or water management encourages soil carbon accumulation and thus conservation of soils that support biologic activity and ecosystem services. For example, an anomalous wet season for south Florida that flooded the forested wetlands through the traditional dry season was followed by the most productive year for photosynthetic carbon uptake and potential soil accumulation. On the other hand, methane emissions were enhanced by the anomalous wet season and extended flooding – which confirmed a complex tradeoff to consider if wetlands are managed for both soil conservation and reduction of greenhouse gas emissions. Potential soil accumulation rates were about 1.7, 2.8, and 18 millimeters per year at the Dwarf Cypress, Cypress Swamp, and Pine Upland ecosystems, assuming soil C density values of 0.07, 0.09, and 0.02 grams of carbon per cubic centimeter, respectively. For these values of soil C density, the accumulation rates are considered a “best-case” upper limit because the lateral export of carbon in the canals and creeks that drain the study area were assumed negligible.

Florida↗

USGS2015

Carbon exchange between the atmosphere and subtropical forested cypress and pine wetlands

Carbon dioxide exchange between the atmosphere and forested subtropical wetlands is largely unknown. Here we report a first step in characterizing this atmospheric–ecosystem 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.

Florida↗

USGS2014

Differentiating transpiration from evaporation in seasonal agricultural wetlands and the link to advective fluxes in the root zone

The current state of science and engineering related to analyzing wetlands overlooks the importance of transpiration and risks data misinterpretation. In response, we developed hydrologic and mass budgets for agricultural wetlands using electrical conductivity (EC) as a natural conservative tracer. We developed simple differential equations that quantify evaporation and transpiration rates using flowrates and tracer concentrations atwetland inflows and outflows. We used two ideal reactormodel solutions, a continuous flowstirred tank reactor (CFSTR) and a plug flow reactor (PFR), to bracket real non-ideal systems. From those models, estimated transpiration ranged from 55% (CFSTR) to 74% (PFR) of total evapotranspiration (ET) rates, consistent with published values using standard methods and direct measurements. The PFR model more appropriately represents these nonideal agricultural wetlands in which check ponds are in series. Using a fluxmodel, we also developed an equation delineating the root zone depth at which diffusive dominated fluxes transition to advective dominated fluxes. This relationship is similar to the Peclet number that identifies the dominance of advective or diffusive fluxes in surface and groundwater transport. Using diffusion coefficients for inorganic mercury (Hg) and methylmercury (MeHg) we calculated that during high ET periods typical of summer, advective fluxes dominate root zone transport except in the top millimeters below the sediment–water interface. The transition depth has diel and seasonal trends, tracking those of ET. Neglecting this pathway has profound implications: misallocating loads along different hydrologic pathways; misinterpreting seasonal and diel water quality trends; confounding Fick's First Law calculations when determining diffusion fluxes using pore water concentration data; and misinterpreting biogeochemicalmechanisms affecting dissolved constituent cycling in the root zone. In addition,our understanding of internal root zone cycling of Hg and other dissolved constituents, benthic fluxes, and biological irrigation may be greatly affected.

Science of the Total Environment↗

USGS2007

Evapotranspiration rates and crop coefficients for a restored marsh in the Sacramento-San Joaquin Delta, California, USA

The surface renewal method was used to estimate evapotranspiration (ET) for a restored marsh on Twitchell Island in the Sacramento–San Joaquin Delta, California, USA. ET estimates for the marsh, together with reference ET measurements from a nearby climate station, were used to determine crop coefficients over a 3‐year period during the growing season. The mean ET rate for the study period was 6 mm day −1 , which is high compared with other marshes with similar vegetation. High ET rates at the marsh may be due to the windy, semi‐arid Mediterranean climate of the region, and the permanently flooded nature of the marsh, which results in very low surface resistance of the vegetation. Crop coefficient ( K c ) values for the marsh ranged from 0·73 to 1·18. The mean K c value over the entire study period was 0·95. The daily K c values for any given month varied from year to year, and the standard deviation of daily K c values varied between months. Although several climate variables were undoubtedly responsible for this variation, our analysis revealed that wind direction and the temperature of standing water in the wetland were of particular importance in determining ET rates and K c values.

Hydrological Processes↗

USGS2004

A project summary: Water and energy budget assessment for a non-tidal wetland in the Sacramento-San Joaquin delta

The methods used to obtain universal cover coefficient (Kc) values for a non-tidal restored wetland in the Sacramento-San Joaquin river delta, US, during the summer of the year 2002 and to investigate possible differences during changing wind patterns are described. A micrometeorological tower over the wetland was established to quantify actual evapotranspiration (ETa) rates and surface energy fluxes for water and energy budget analysis. The eddy-covariance (EC) system was used to measure the surface energy budget data in the period from May 23 to November 6, 2002. The results show that K c values should be lower during westerly than northerly wind events during the midseason period due to the reduced vapor pressure deficit.

Conference Paper↗