Browsing by Author "Seyfferth, Angelia L."
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Item Contrasting roles of rice root iron plaque in retention and plant uptake of silicon, phosphorus, arsenic, and selenium in diverse paddy soils(Plant and Soil, 2024-02-20) Linam, Franklin A.; Limmer, Matt A.; Seyfferth, Angelia L.Background and aims Iron (Fe) plaque on rice roots is a mixture of Fe oxide and oxyhydroxide minerals thought to protect rice from high levels of arsenic (As) in flooded paddy soils. Silicon (Si), phosphorus (P), and selenium (Se) also exist as oxyanions in rice paddies, but the impacts of Fe plaque on uptake of these nutrients are unknown. Methods We used natural variation in paddy soil chemistry to test how Si, P, As, and Se move from porewater to plaque to plant via multiple techniques. In a pot study, we monitored Fe plaque deposition and porewater chemistry in 5 different soils over time and measured plaque/plant chemistry and Fe plaque mineralogy at harvest. We normalized oxyanion concentrations by Fe to determine the preferential retention on plaque or plant uptake. Results Low phosphorus availability increased root Fe-oxidizing activity, while Fe, Si, P, As, and Se concentrations in plaque were strongly correlated with porewater. Plaque did not appreciably retain Si and Se, and the oxyanions did not compete for adsorption sites on the Fe plaque. Conclusion Root Fe plaque seems to protect rice from As uptake, does not interfere with Si and Se uptake, and roots adapt to maintain P nutrition even with retention of porewater P on plaque.Item High methane concentrations in tidal salt marsh soils: Where does the methane go?(Global Change Biology, 2023-11-30) Capooci, Margaret; Seyfferth, Angelia L.; Tobias, Craig; Wozniak, Andrew S.; Hedgpeth, Alexandra; Bowen, Malique; Biddle, Jennifer F.; McFarlane, Karis J.; Vargas, RodrigoTidal salt marshes produce and emit CH4. Therefore, it is critical to understand the biogeochemical controls that regulate CH4 spatial and temporal dynamics in wetlands. The prevailing paradigm assumes that acetoclastic methanogenesis is the dominant pathway for CH4 production, and higher salinity concentrations inhibit CH4 production in salt marshes. Recent evidence shows that CH4 is produced within salt marshes via methylotrophic methanogenesis, a process not inhibited by sulfate reduction. To further explore this conundrum, we performed measurements of soil–atmosphere CH4 and CO2 fluxes coupled with depth profiles of soil CH4 and CO2 pore water gas concentrations, stable and radioisotopes, pore water chemistry, and microbial community composition to assess CH4 production and fate within a temperate tidal salt marsh. We found unexpectedly high CH4 concentrations up to 145,000 μmol mol−1 positively correlated with S2− (salinity range: 6.6–14.5 ppt). Despite large CH4 production within the soil, soil–atmosphere CH4 fluxes were low but with higher emissions and extreme variability during plant senescence (84.3 ± 684.4 nmol m−2 s−1). CH4 and CO2 within the soil pore water were produced from young carbon, with most Δ14C-CH4 and Δ14C-CO2 values at or above modern. We found evidence that CH4 within soils was produced by methylotrophic and hydrogenotrophic methanogenesis. Several pathways exist after CH4 is produced, including diffusion into the atmosphere, CH4 oxidation, and lateral export to adjacent tidal creeks; the latter being the most likely dominant flux. Our findings demonstrate that CH4 production and fluxes are biogeochemically heterogeneous, with multiple processes and pathways that can co-occur and vary in importance over the year. This study highlights the potential for high CH4 production, the need to understand the underlying biogeochemical controls, and the challenges of evaluating CH4 budgets and blue carbon in salt marshes.Item How manganese affects rice cadmium uptake and translocation in vegetative and mature plants(Plant and Soil, 2024-04-19) Hu, Ruifang; Limmer, Matthew A.; Seyfferth, Angelia L.Background and aims Rice is prone to Cd uptake under aerobic soil conditions primarily due to the OsNramp5 Mn transport pathway. Unlike Cd, Mn availability in rice paddies decreases as redox potential increases. We tested whether increasing Mn concentrations in solution would decrease Cd accumulation in rice through competition between Mn and Cd for uptake and/or suppression of OsNramp5 expression. Methods Rice was grown to maturity under Mn concentrations that spanned three orders of magnitude (0.30 to 37 μM) that corresponded to free Mn2+ activities of 10–7.9 to 10–5.0 M while free Cd2+ activity was held as constant as achievable (10–10.2 to 10–10.4 M). Plant biomass and elemental concentrations were measured in roots and shoots at each stage. Fold changes in the expression of OsNramp5, OsCd1, OsHMA3, OsCCX2, and OsYSL6 genes in vegetative and grain-filling stages of rice plants were determined. Results Competition between Mn and Cd for root uptake and accumulation in shoots was observed at the highest concentration of Mn tested. OsNramp5 expression was significantly higher in rice plants at the vegetative stage compared to the grain-filling stage, while OsCd1 and OsHMA3 showed the opposite. Solution Mn concentrations previously thought to be tolerable by rice grown to the vegetative stage led to Mn toxicity as plants matured. Conclusions Mn competes with Cd during uptake into rice with OsNramp5 expression unaffected. Different translocation paths may occur for Mn and Cd within the rice plant and over the rice life cycle, with OsCCX2 correlated with shoot Cd concentration.Item Hyperspectral Reflectance for Measuring Canopy-Level Nutrients and Photosynthesis in a Salt Marsh(Journal of Geophysical Research: Biogeosciences, 2022-11-04) Vázquez-Lule, Alma; Seyfferth, Angelia L.; Limmer, Matt A.; Mey, Paul; Guevara, Mario; Vargas, RodrigoSalt marsh ecosystems are underrepresented in process-based models due to their unique location across the terrestrial–aquatic interface. Particularly, the role of leaf nutrients on canopy photosynthesis (FA) remains unclear, despite their relevance for regulating vegetation growth. We combined multiyear information of canopy-level nutrients and eddy covariance measurements with canopy surface hyperspectral remote sensing (CSHRS) to quantify the spatial and temporal variability of FA in a temperate salt marsh. We found that FA showed a positive relationship with canopy-level N at the ecosystem scale and for areas dominated by Spartina cynosuroides, but not for areas dominated by short S. alterniflora. FA showed a positive relationship with canopy-level P, K, and Na, but a negative relationship with Fe, for areas associated with S. cynosuroides, S. alterniflora, and at the ecosystem scale. We used partial least squares regression (PLSR) with CSHRS and found statistically significant data–model agreements to predict canopy-level nutrients and FA. The red-edge electromagnetic region and ∼770 nm showed the highest contribution of variance in PLSR models for canopy-level nutrients and FA, but we propose that underlying sediment biogeochemistry can complicate interpretation of reflectance measurements. Our findings highlight the relevance of spatial variability in salt marshes vegetation and the promising application of CSHRS for linking information of canopy-level nutrients with FA. We call for further development of canopy surface hyperspectral methods and analyses across salt marshes to improve our understanding of how these ecosystems will respond to global environmental change. Plain Language Summary Canopy photosynthesis in salt marshes contributes to the carbon stored in these ecosystems; however, its relationship with canopy-level nutrients has been underrepresented in models. Reflectance from near surface remote sensing could be a cost-effective nondestructive tool to monitor canopy photosynthesis and associated nutrients in salt marshes. We combined canopy-level nutrient information with hyperspectral canopy reflectance to represent the spatial and temporal variability of canopy photosynthesis in a salt marsh in the Mid-Atlantic cost of the U.S. We found that local variability such as different salt marsh species have an influence on the relationship between canopy photosynthesis and associated nutrients, in consequence the most limiting nutrients for photosynthesis were phosphorus, potassium, and sodium. We propose that underlying sediment biogeochemistry can potentially obscure the expected relationships between plant nutrients and photosynthesis in remote sensing of coastal wetlands. These results open the possibility to use similar reflectance information from airborne or spaceborne platforms to explore these relationships at broader scales. Key Points - Local environmental variability influences the relationship of canopy nutrients with canopy photosynthesis in a salt marsh ecosystem - Sediment biogeochemistry can obscure expected relationships between plant nutrients and photosynthesis in remote sensing of coastal wetlands - Canopy surface hyperspectral remote sensing is a promising technique for studying vegetation dynamics of salt marshesItem Physiochemical Controls on the Horizontal Exchange of Blue Carbon Across the Salt Marsh-Tidal Channel Interface(Journal of Geophysical Research: Biogeosciences, 2023-06-06) Fettrow, Sean; Jeppi, Virginia; Wozniak, Andrew; Vargas, Rodrigo; Michael, Holly; Seyfferth, Angelia L.Tidal channels are biogeochemical hotspots that horizontally exchange carbon (C) with marsh platforms, but the physiochemical drivers controlling these dynamics are poorly understood. We hypothesized that C-bearing iron (Fe) oxides precipitate and immobilize dissolved organic carbon (DOC) during ebb tide as the soils oxygenate, and dissolve into the porewater during flood tide, promoting transport to the channel. The hydraulic gradient physically controls how these solutes are horizontally exchanged across the marsh platform-tidal channel interface; we hypothesized that this gradient alters the concentration and source of C being exchanged. We further hypothesized that trace soil gases (i.e., CO2, CH4, dimethyl sulfide) are pushed out of the channel bank as the groundwater rises. To test these hypotheses, we measured porewater, surface water, and soil trace gases over two 24-hr monitoring campaigns (i.e., summer and spring) in a mesohaline tidal marsh. We found that Fe2+ and DOC were positively related during flood tide but not during ebb tide in spring when soils were more oxidized. This finding shows evidence for the formation and dissolution of C-bearing Fe oxides across a tidal cycle. In addition, the tidal channel contained significantly (p < 0.05) more terrestrial-like DOC when the hydraulic gradient was driving flow toward the channel. In comparison, the channel water was saltier and contained significantly (p < 0.05) more marine-like DOC when the hydraulic gradient reversed direction. Trace gas fluxes increased with rising groundwater levels, particularly dimethyl sulfide. These findings suggest multiple physiochemical mechanisms controlling the horizontal exchange of C at the marsh platform-tidal channel interface. Plain Language Summary Tidal salt marshes store large amounts of carbon belowground in soils, but there is also a significant amount of carbon flowing into and out of these ecosystems via tidal channels. We investigated the carbon flowing between the channel bank and surface water in a salt marsh in Delaware. We found that soil minerals (i.e., iron oxides) control the mobility of carbon as iron oxides retain carbon during ebb tides and release carbon during flood tides as the minerals dissolve. The gradient between the groundwater and surface water elevation (i.e., hydraulic gradient) controls the flow direction for dissolved carbon, altering the concentration and source of carbon found in the tidal channel across tidal cycles. In addition, gases trapped in channel banks are pushed out of the soils as the tide rises. These findings will improve our understanding of carbon cycles in these critical carbon sinks. Key Points - Physiochemical mechanisms control horizontal exchange of carbon across marsh-tidal channel interfaces, affecting lateral carbon flux - Dissolution and reprecipitation of carbon-bearing Fe oxides during flood and ebb tides control the horizontal mobility of carbon - Hydraulic gradients control the carbon character in the tidal channel, and rising tides push greenhouse gases out of the channel bankItem Rice husk and husk biochar soil amendments store soil carbon while water management controls dissolved organic matter chemistry in well-weathered soil(Journal of Environmental Management, 2023-04-15) Linam, Franklin; Limmer, Matt A.; Ebling, Alina M.; Seyfferth, Angelia L.Rice agriculture feeds over half the world's population, and paddy soils impact the carbon cycle through soil organic carbon (SOC) preservation and production of carbon dioxide (CO2) and methane (CH4), which are greenhouse gases (GHG). Rice husk is a nutrient-rich, underutilized byproduct of rice milling that is sometimes pyrolyzed or combusted. It is unresolved how the incorporation of these residues affects C dynamics in paddy soil. In this study, we sought to determine how untreated (Husk), low-temperature pyrolyzed (Biochar), and combusted (CharSil) husk amendments affect SOC levels, GHG emissions, and dissolved organic matter (DOM) chemistry. We amended Ultisol paddy mesocosms and collected SOC and GHG data for three years of rice grown under alternate wetting and drying (AWD) conditions. We also performed a greenhouse pot study that included water management treatments of nonflooded, AWD, and flooded. Husk, Biochar, and CharSil amendments and flooding generally increased SOC storage and CH4 emissions, while nonflooded conditions increased N2O emissions and nonflooded and CharSil treatments increased CO2 emissions. All amendments stored ∼0.15 kg C m−2 y−1 more SOC than CH4 emissions (as CO2 equivalents), but the combustion of husk to produce CharSil resulted in the net release of CO2 which negates any SOC storage. UV–visible absorption/fluorescence spectroscopy from the pot study suggests that nonflooded treatment decreased DOM aromaticity and molecular size. Our data show that flooding and amendment of Husk and Biochar maximized C storage in the highly weathered rice paddy soil under study despite Husk increasing CH4 emissions. Water management affected dissolved organic matter chemistry more strongly than amendments, but this requires further investigation. Return of rice husk that is untreated or pyrolyzed at low temperature shows promise to close nutrient loops and preserve SOC in rice paddy soils. Graphical abstract available at: https://doi.org/10.1016/j.jenvman.2023.117936Item Socio-Technical Changes for Sustainable Rice Production: Rice Husk Amendment, Conservation Irrigation, and System Changes(Frontiers in Agronomy, 2021-10-22) Runkle, Benjamin R. K.; Seyfferth, Angelia L.; Reid, Matthew C.; Limmer, Matthew A.; Moreno-García, Beatriz; Reavis, Colby W. Reavis; Peña, Jasquelin; Reba, Michele L.; Adviento-Borbe, M. Arlene A.; Pinson, Shannon R. M.; Isbell, ChrisRice is a staple food and primary source of calories for much of the world. However, rice can be a dietary source of toxic metal(loid)s to humans, and its cultivation creates atmospheric greenhouse gas emissions and requires high water use. Because rice production consumes a significant amount of natural resources and is a large part of the global agricultural economy, increasing its sustainability could have substantial societal benefits. There are opportunities for more sustainable field production through a combination of silicon (Si) management and conservation irrigation practices. As a Si-rich soil amendment, rice husks can limit arsenic and cadmium uptake, while also providing plant vigor in drier soil conditions. Thus, husk addition and conservation irrigation may be more effective to attenuate the accumulation of toxic metal(loid)s, manage water usage and lower climate impacts when implemented together than when either is implemented separately. This modified field production system would take advantage of rice husks, which are an underutilized by-product of milled rice that is widely available near rice farm sites, and have ~10% Si content. Husk application could, alongside alternate wetting and drying or furrow irrigation management, help resolve multiple sustainability challenges in rice production: (1) limit arsenic and cadmium accumulation in rice; (2) minimize greenhouse gas emissions from rice production; (3) decrease irrigation water use; (4) improve nutrient use efficiency; (5) utilize a waste product of rice processing; and (6) maintain plant-accessible soil Si levels. This review presents the scientific basis for a shift in rice production practices and considers complementary rice breeding efforts. It then examines socio-technical considerations for how such a shift in production practices could be implemented by farmers and millers together and may bring rice production closer to a bio-circular economy. This paper's purpose is to advocate for a changed rice production method for consideration by community stakeholders, including producers, millers, breeders, extension specialists, supply chain organizations, and consumers, while highlighting remaining research and implementation questions.Item Unraveling the Mechanisms of Fe Oxidation and Mn Reduction on Mn Indicators of Reduction in Soil (IRIS) Films(Environmental Science and Technology, 2023-04-25) Limmer, Matt A.; Linam, Franklin A.; Evans, Abby E.; Seyfferth, Angelia L.Indicators of reduction in soil (IRIS) devices are low-cost soil redox sensors coated with Fe or Mn oxides, which can be reductively dissolved from the device under suitable redox conditions. Removal of the metal oxide coating from the surface, leaving behind the white film, can be quantified and used as an indicator of reducing conditions in soils. Manganese IRIS, coated with birnessite, can also oxidize Fe(II), resulting in a color change from brown to orange that complicates the interpretation of coating removal. Here, we studied field-deployed Mn IRIS films where Fe oxidation was present to unravel the mechanisms of Mn oxidation of Fe(II) and the resulting minerals on the IRIS film surface. We observed reductions in the Mn average oxidation state when Fe precipitation was evident. Fe precipitation was primarily ferrihydrite (30–90%), but lepidocrocite and goethite were also detected, notably when the Mn average oxidation state decreased. The decrease in the average oxidation state of Mn was due to the adsorption of Mn(II) to the oxidized Fe and the precipitation of rhodochrosite (MnCO3) on the film. The results were variable on small spatial scales (<1 mm), highlighting the suitability of IRIS in studying heterogeneous redox reactions in soil. Mn IRIS also provides a tool to bridge lab and field studies of the interactions between Mn oxides and reduced constituents.