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1. Hurricanes fertilize mangrove forests in the Gulf of Mexico (Florida Everglades, USA)

   https://doi.org/10.1073/pnas.1908597117  

   Castañeda-Moya, Edward; Rivera-Monroy, Victor H.; Chambers, Randolph M.; Zhao, Xiaochen; Lamb-Wotton, Lukas; Gorsky, Adrianna; Gaiser, Evelyn E.; Troxler, Tiffany G.; Kominoski, John S.; Hiatt, Matthew (February 2020, Proceedings of the National Academy of Sciences)

   Hurricanes are recurring high-energy disturbances in coastal regions that change community structure and function of mangrove wetlands. However, most of the studies assessing hurricane impacts on mangroves have focused on negative effects without considering the positive influence of hurricane-induced sediment deposition and associated nutrient fertilization on mangrove productivity and resilience. Here, we quantified how Hurricane Irma influenced soil nutrient pools, vertical accretion, and plant phosphorus (P) uptake after its passage across the Florida Coastal Everglades in September 2017. Vertical accretion from Irma’s deposits was 6.7 to 14.4 times greater than the long-term (100 y) annual accretion rate (0.27 ± 0.04 cm y⁻¹). Storm deposits extended up to 10-km inland from the Gulf of Mexico. Total P (TP) inputs were highest at the mouth of estuaries, with P concentration double that of underlying surface (top 10 cm) soils (0.19 ± 0.02 mg cm⁻³). This P deposition contributed 49 to 98% to the soil nutrient pool. As a result, all mangrove species showed a significant increase in litter foliar TP and soil porewater inorganic P concentrations in early 2018, 3 mo after Irma’s impact, thus underscoring the interspecies differences in nutrient uptake. Mean TP loading rates were five times greater in southwestern (94 ± 13 kg ha⁻¹d⁻¹) mangrove-dominated estuaries compared to the southeastern region, highlighting the positive role of hurricanes as a natural fertilization mechanism influencing forest productivity. P-rich, mineral sediments deposited by hurricanes create legacies that facilitate rapid forest recovery, stimulation of peat soil development, and resilience to sea-level rise. 

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2. Stronger fertilization effects on aboveground versus belowground plant properties across nine U.S. grasslands

   https://doi.org/10.1002/ecy.3891  

   Keller, Adrienne B.; Walter, Christopher A.; Blumenthal, Dana M.; Borer, Elizabeth T.; Collins, Scott L.; DeLancey, Lang C.; Fay, Philip A.; Hofmockel, Kirsten S.; Knops, Johannes M. H.; Leakey, Andrew D. B.; et al (December 2022, Ecology)

   Abstract Increased nutrient inputs due to anthropogenic activity are expected to increase primary productivity across terrestrial ecosystems, but changes in allocation aboveground versus belowground with nutrient addition have different implications for soil carbon (C) storage. Thus, given that roots are major contributors to soil C storage, understanding belowground net primary productivity (BNPP) and biomass responses to changes in nutrient availability is essential to predicting carbon–climate feedbacks in the context of interacting global environmental changes. To address this knowledge gap, we tested whether a decade of nitrogen (N) and phosphorus (P) fertilization consistently influenced aboveground and belowground biomass and productivity at nine grassland sites spanning a wide range of climatic and edaphic conditions in the continental United States. Fertilization effects were strong aboveground, with both N and P addition stimulating aboveground biomass at nearly all sites (by 30% and 36%, respectively, on average). P addition consistently increased root production (by 15% on average), whereas other belowground responses to fertilization were more variable, ranging from positive to negative across sites. Site‐specific responses to P were not predicted by the measured covariates. Atmospheric N deposition mediated the effect of N fertilization on root biomass and turnover. Specifically, atmospheric N deposition was positively correlated with root turnover rates, and this relationship was amplified with N addition. Nitrogen addition increased root biomass at sites with low N deposition but decreased it at sites with high N deposition. Overall, these results suggest that the effects of nutrient supply on belowground plant properties are context dependent, particularly with regard to background N supply rates, demonstrating that site conditions must be considered when predicting how grassland ecosystems will respond to increased nutrient loading from anthropogenic activity. 

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3. Incorporating uncertainty in a wetland soil accretion model (NUMAN 2.0) to test generality across coastal environmental settings of south Florida

   https://doi.org/10.1016/j.ecss.2025.109407  

   Biswas, P; Twilley, R R; Rovai, A; Christensen, A; Shribman, Z; Kameshwar, S (June 2025, Estuarine, Coastal and Shelf Science)

   Understanding the relative contributions of aboveground and belowground processes to soil accretion and carbon density may explain carbon sequestration rates in mangroves across different coastal environmental settings. We reformulated the nutrient mangrove model (NUMAN) by improving algorithms and uncertainty analysis using literature values and site-specific observations to evaluate the relative contributions of organic and inorganic sedimentation for three mangrove sites with marked soil fertility gradients reflected by nitrogen-to-phosphorus (N:P) ratios including Shark River (N:P = 28), Rookery Bay (N:P = 54–78), and Taylor Slough (N:P = 102) in south Florida. NUMAN 2.0 considers cellulose as a refractory organic-matter sub-pool and simultaneously incorporates coarse-root inputs to soil formation. The model simulation also captures root necromass accumulation. Monte Carlo (MC) simulations (N = 1000 per site) were conducted to capture uncertainty by treating five key parameters as random variables: lignin content in fine, coarse, and large roots; inorganic sediment loading; and root biomass at the surface. With robust mass balancing of organic matter, NUMAN 2.0 generates precise predictions of surface accretion and carbon density. NUMAN 2.0 simulations estimated mean (standard deviation) soil carbon sequestration rates at 130.1 (55.4) for Shark River, 72.5 (3.7) for Rookery Bay, and 130.0 (83.9) g m-2 yr-1 for Taylor Slough, compared to field values of 123.0, 86.0, and 108.8 (8.7) g m-2 yr-1 , respectively. Simulation experiments with NUMAN 2.0 suggest that belowground organic matter dominates soil formation and carbon sequestration generally in coastal environmental settings with little allochthonous input such as carbonate settings, while wood litterfall should dominate soil organic matter in top 10 cm in estuaries, and bays. 

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4. Water levels primarily drive variation in photosynthesis and nutrient use of scrub Red Mangroves in the southeastern Florida Everglades

   https://doi.org/10.1093/treephys/tpab151  

   Hogan, J Aaron; Castañeda-Moya, Edward; Lamb-Wotton, Lukas; Troxler, Tiffany; Baraloto, Christopher (November 2021, Tree Physiology)

   Ball, Marilyn (Ed.)

   Abstract We investigated how mangrove-island micro-elevation (i.e., habitat: center vs edge) affects tree physiology in a scrub mangrove forest of the southeastern Everglades. We measured leaf gas exchange rates of scrub Rhizophora mangle L. trees monthly during 2019, hypothesizing that CO2 assimilation (Anet) and stomatal conductance (gsw) would decline with increasing water levels and salinity, expecting more considerable differences at mangrove-island edges than centers, where physiological stress is greatest. Water levels varied between 0 and 60 cm from the soil surface, rising during the wet season (May–October) relative to the dry season (November–April). Porewater salinity ranged from 15 to 30 p.p.t., being higher at mangrove-island edges than centers. Anet maximized at 15.1 μmol m−2 s−1, and gsw was typically <0.2 mol m−2 s−1, both of which were greater in the dry than the wet season and greater at island centers than edges, with seasonal variability being roughly equal to variation between habitats. After accounting for season and habitat, water level positively affected Anet in both seasons but did not affect gsw. Our findings suggest that inundation stress (i.e., water level) is the primary driver of variation in leaf gas exchange rates of scrub mangroves in the Florida Everglades, while also constraining Anet more than gsw. The interaction between inundation stress due to permanent flooding and habitat varies with season as physiological stress is alleviated at higher-elevation mangrove-island center habitats during the dry season. Freshwater inflows during the wet season increase water levels and inundation stress at higher-elevation mangrove-island centers, but also potentially alleviate salt and sulfide stress in soils. Thus, habitat heterogeneity leads to differences in nutrient and water acquisition and use between trees growing in island centers versus edges, creating distinct physiological controls on photosynthesis, which likely affect carbon flux dynamics of scrub mangroves in the Everglades. 

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5. Impacts of Arctic Shrubs on Root Traits and Belowground Nutrient Cycles Across a Northern Alaskan Climate Gradient

   https://doi.org/10.3389/fpls.2020.588098  

   Chen, Weile; Tape, Ken D.; Euskirchen, Eugénie S.; Liang, Shuang; Matos, Adriano; Greenberg, Jonathan; Fraterrigo, Jennifer M. (December 2020, Frontiers in Plant Science)

   null (Ed.)

   Deciduous shrubs are expanding across the graminoid-dominated nutrient-poor arctic tundra. Absorptive root traits of shrubs are key determinants of nutrient acquisition strategy from tundra soils, but the variations of shrub root traits within and among common shrub genera across the arctic climatic gradient are not well resolved. Consequently, the impacts of arctic shrub expansion on belowground nutrient cycling remain largely unclear. Here, we collected roots from 170 plots of three commonly distributed shrub genera ( Alnus , Betula , and Salix ) and a widespread sedge ( Eriophorum vaginatum ) along a climatic gradient in northern Alaska. Absorptive root traits that are relevant to the strategy of plant nutrient acquisition were determined. The influence of aboveground dominant vegetation cover on the standing root biomass, root productivity, vertical rooting profile, as well as the soil nitrogen (N) pool in the active soil layer was examined. We found consistent root trait variation among arctic plant genera along the sampling transect. Alnus and Betula had relatively thicker and less branched, but more frequently ectomycorrhizal colonized absorptive roots than Salix , suggesting complementarity between root efficiency and ectomycorrhizal dependence among the co-existing shrubs. Shrub-dominated plots tended to have more productive absorptive roots than sedge-dominated plots. At the northern sites, deep absorptive roots (>20 cm depth) were more frequent in birch-dominated plots. We also found shrub roots extensively proliferated into the adjacent sedge-dominated plots. The soil N pool in the active layer generally decreased from south to north but did not vary among plots dominated by different shrub or sedge genera. Our results reveal diverse nutrient acquisition strategies and belowground impacts among different arctic shrubs, suggesting that further identifying the specific shrub genera in the tundra landscape will ultimately provide better predictions of belowground dynamics across the changing arctic. 

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