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1. Salinization, inundation and tree mortality interact to affect greenhouse gas emissions from stressed coastal forests

   https://doi.org/10.1016/j.soilbio.2023.109101  

   Seyfried, Georgia S.; Chow, Alex T.; O'Halloran, Thomas L. (September 2023, Soil Biology and Biochemistry)

   Sea level rise and intensifying storms cause salinization and freshwater inundation of coastal forest soils which can result in tree mortality and altered ecosystem carbon (C) cycling. However, it is not yet clear if increased salinity and inundation will affect greenhouse gas (GHG) emissions to feed back with climate change. To assess the impacts of in situ chronic and pulsed salinity on GHG fluxes from coastal forests, we made continuous measurements of carbon dioxide and methane fluxes from intact soil cores collected in 1) an upland forest dominated by loblolly pine (Pinus taeda) and a freshwater swamp dominated by baldcypress (Taxodium distichum) 2) adjacent forest stands within forest types experiencing high versus low salinization and associated tree mortality and 3) before and after pulsed salinity from a hurricane related storm surge. In lab mesocosms, all soil cores were exposed to three levels of rainwater addition to assess potential interactive effects between salinization and inundation. We found that chronic salinization and associated tree mortality decreased soil CO2 fluxes in loblolly, but not baldcypress forest with in situ soil inundation patterns potentially driving the site effect. Additionally, in an upland loblolly forest, pulsed salinity from a storm surge exhibited the potential to increase CH4 fluxes. Finally, the effect of rainwater inundation on CH4 fluxes was greater in low compared to high salinity stands suggesting that salinization may have suppressed the effects of rainwater inundation on CH4 fluxes. Overall, we show that complex interactions between biotic and abiotic conditions in stressed coastal forests can alter GHG emissions, highlighting a need for future research focused on understanding the mechanisms driving GHG fluxes from coastal forests under changing environmental conditions. 

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2. The Ecohydrology of Coastal Ghost Forests

   https://doi.org/10.1002/eco.70020  

   Fagherazzi, Sergio; Nordio, Giovanna; Boaga, Jacopo; Cassiani, Giorgio; Michael, Holly A; Pratt, Dannielle; Messerschmidt, Tyler C; Kirwan, Matthew L; Stotts, Stephanie (March 2025, Ecohydrology)

   ABSTRACT Sea level rise and storm surges affect coastal forests along low‐lying shorelines. Salinization and flooding kill trees and favour the encroachment of salt‐tolerant marsh vegetation. The hydrology of this ecological transition is complex and requires a multidisciplinary approach. Sea level rise (press) and storms (pulses) act on different timescales, affecting the forest vegetation in different ways. Salinization can occur either by vertical infiltration during flooding or from the aquifer driven by tides and sea level rise. Here, we detail the ecohydrological processes acting in the critical zone of retreating coastal forests. An increase in sea level has a three‐pronged effect on flooding and salinization: It raises the maximum elevation of storm surges, shifts the freshwater‐saltwater interface inland, and elevates the water table, leading to surface flooding from below. Trees can modify their root systems and local soil hydrology to better withstand salinization. Hydrological stress from intermittent storm surges inhibits tree growth, as evidenced by tree ring analysis. Tree rings also reveal a lag between the time when tree growth significantly slows and when the tree ultimately dies. Tree dieback reduces transpiration, retaining more water in the soil and creating conditions more favourable for flooding. Sedimentation from storm waters combined to organic matter decomposition can change the landscape, affecting flooding and runoff. Our results indicate that only a multidisciplinary approach can fully capture the ecohydrology of retreating forests in a period of accelerated sea level rise. 

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3. Effect of Irrigation Water Quality and Soil Compost Treatment on Salinity Management to Improve Soil Health and Plant Yield

   https://doi.org/10.3390/w16101391  

   Suvendran, Subanky; Johnson, David; Acevedo, Miguel; Smithers, Breana; Xu, Pei (May 2024, Water)

   Increasing soil salinity and degraded irrigation water quality are major challenges for agriculture. This study investigated the effects of irrigation water quality and incorporating compost (3% dry mass in soil) on minimizing soil salinization and promoting sustainable cropping systems. A greenhouse study used brackish water (electrical conductivity of 2010 µS/cm) and agricultural water (792 µS/cm) to irrigate Dundale pea and clay loam soil. Compost treatment enhanced soil water retention with soil moisture content above 0.280 m3/m3, increased plant carbon assimilation by ~30%, improved plant growth by >50%, and reduced NO3− leaching from the soil by 16% and 23.5% for agricultural and brackish water irrigation, respectively. Compared to no compost treatment, the compost-incorporated soil irrigated with brackish water showed the highest plant growth by increasing plant fresh weight by 64%, dry weight by 50%, root length by 121%, and plant height by 16%. Compost treatment reduced soil sodicity during brackish water irrigation by promoting the leaching of Cl− and Na+ from the soil. Compost treatment provides an environmentally sustainable approach to managing soil salinity, remediating the impact of brackish water irrigation, improving soil organic matter, enhancing the availability of water and nutrients to plants, and increasing plant growth and carbon sequestration potential. 

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4. Applicability and Sensitivity of Field Hydrology Modeling by the Soil Plant Air Water (SPAW) Model Under Changes in Soil Properties

   https://doi.org/10.13031/ja.15306  

   Saha, Ajoy Kumar; McMaine, John (January 2023, Journal of the ASABE)

   Highlights Changes to soil properties and precipitation scenarios significantly affect the water balance in agro-hydrology. SPAW model is sensitive to simulated runoff and infiltration, but it has limitations in responding to soil compaction and organic matter change. Increasing organic matter (1% to 5%) did not significantly affect runoff or infiltration in silty and sandy loam soil. Low precipitation generates significantly lower runoff (%) and higher infiltration. Abstract. Agricultural practices can change soil properties and the amount of runoff generated from a landscape. Modeling results could be significantly different than expected if the web soil survey or other commonly used remote sensing applications are used as model inputs without site verification. This study assessed the applicability and sensitivity of the Soil-Plant-Air-Water (SPAW) Model for simulating the runoff (%) and infiltration (%) components of the water balance for various soil physical properties, cover crop, and weather variables. Soil profiles in 135 combinations were developed with three soil classes (sandy loam, silt loam, and clay), five organic matter levels (1%, 2%, 3%, 4%, and 5%), three levels of compaction (low, medium, and high), and three topsoil layer thicknesses (7.6 cm, 11.4 cm, and 15 cm). Also, three cover crop treatments were simulated by modifying surface cover and evapotranspiration during the non-growing season. Finally, two precipitation regimes were considered (Iowa City, IA, as high precipitation and Brookings, SD, as low precipitation) to simulate runoff and infiltration. In total, 810 scenarios were run, resulting in over 300 million data points. This study confirmed that soil texture, bulk density, and topsoil thickness significantly (p<0.01) influence runoff generation and infiltration percentage based on the water balance criterion. Interestingly, the SPAW model had no significant response on runoff (%) and infiltration (%) to organic matter levels changing from 1% to 5%. This simulation demonstrates that runoff estimations can be significantly influenced by soil properties that can change due to agricultural conservation practices (ACPs) or, conversely, by compaction events. Inputs to models must account for these changes rather than relying only on historical or remote sensing inputs. Keywords: Agricultural conservation practices, Conservation agriculture, Field hydrology, Infiltration, Runoff, SPAW. 

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5. Clay soil amendment suppressed microbial enzymatic activities while increasing nitrogen availability in sandy soils

   https://doi.org/10.1002/saj2.20731  

   Poudel, Pratima; Ye, Rongzhong; Parajuli, Binaya (July 2024, Soil Science Society of America Journal)

   Abstract Conservation management practices often produced positive but limited desirable outcomes in US Southeast sandy soils, likely due to their intrinsically low clay contents that constrain the soil's capacity to preserve organic carbon (C) and nutrients. In the field, we tested the effectiveness of a novel approach, that is, clay soil amendment, to improve sandy soils. In October 2017, clay‐rich soils (25% clay) were spread at 25 metric tons ha⁻¹ and tilled onto a sandy soil (1.9% clay) in the field, which was further mixed by light tillage at 0‐ to 15‐cm depth, followed by planting winter cover crop mixtures (cereal rye, crimson clover, and winter pea). The crop rotation was cotton and corn with cover crop mixtures planted in the winter fallow season. Soils (0–15 cm) were collected in August 2021 and subjected to physio‐biochemical analyses. Clay amendment increased soil clay content to 3.4%, which improved nitrogen (N) availability by 51% but inhibited the activities of C (β‐d‐cellubiosidase [CB]; β‐xylosidase [BX];N‐acetyl‐β‐glucosaminidase [NAG]) and N (leucine aminopeptidase [LAP]) cycling enzymes, resulting in up to 78% reduction in microbial respiration. A follow‐up kinetic study on BG and LAP enzymes suggested that clay addition can have different impacts on enzymes with diverse biological origins through distinct mechanisms. Clay addition can potentially improve sandy soils by stabilizing the organic inputs in soils. However, more research is required to understand its long‐term impacts making this approach practical. 

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