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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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Long‐term root dynamics of subtropical mangroves following Hurricanes Wilma and Irma in the Florida Everglades, USA
Abstract Hurricanes are among the most destructive natural disturbances in mangroves, altering community structure and ecological processes. Despite their impacts, few studies have assessed changes in belowground root processes (i.e., biomass, production, decomposition) following major hurricanes. Here, we quantified and compared changes in mangrove root processes in the Florida Coastal Everglades before (pre‐hurricane period: 2000–2004) and after post‐hurricane periods (post‐Wilma, May 2012; immediate‐post‐Irma, March 2018; post‐Irma, March 2023). We assessed spatiotemporal patterns in root dynamics across four mangrove sites (upstream, midstream, downstream, and estuary mouth) along a well‐defined soil phosphorus fertility gradient in the Shark River estuary. Root biomass carbon stocks were highest in the immediate‐post‐Irma and post‐Irma periods. The midstream site had the highest root C stocks, whereas the downstream site had the lowest across periods. Root size class distribution shifted considerably post‐hurricane, with fine roots accounting for 32% (post‐Wilma) to 66% (immediate‐post‐Irma and post‐Irma) of the total root C stocks across sites. However, root production did not vary among periods at any site, although estimates were higher midstream compared to upstream or downstream. Root total nitrogen and P were ~1.3 times higher in the post‐Irma period compared to other periods, with root P consistently increasing from upstream to the estuary mouth. Fine root turnover rates were lower post‐hurricane compared to pre‐hurricane across sites. Root decay rates declined post‐Irma at all sites, except at the midstream site. Our findings suggest that P‐rich sediments deposited by hurricanes can enhance belowground C allocation by increasing root biomass and nutrient uptake, while reducing root turnover to facilitate forest recovery. These responses underscore the strong phenotypic plasticity and resilience of mangrove roots in P‐limited carbonate settings, highlighting their critical role in C sequestration, resilience, and ecosystem stability as climate‐related disturbances and sea‐level rise intensify.
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- PAR ID:
- 10650783
- Publisher / Repository:
- Ecological Society of America
- Date Published:
- Journal Name:
- Ecosphere
- Volume:
- 16
- Issue:
- 11
- ISSN:
- 2150-8925
- Subject(s) / Keyword(s):
- Florida Coastal Everglades Hurricane Irma Hurricane Wilma mangroves P availability root biomass root decomposition root productivity
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/ecs2.70450
