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Along low-elevation coastlines, sea-level rise (SLR) threatens to salinate ecosystems. To understand the effects of SLR and freshwater management on landscape carbon (C) exchange, we measured the net ecosystem exchange (NEE) of CO2 between subtropical wetland ecosystems and the atmosphere along a dynamic salinity gradient. Ecosystems were representative of freshwater marl prairies, brackish ecotones, and saline scrub mangrove forests in the southeastern Everglades. Patterns in NEE explained the landward movement of coastal wetlands, a process observed over the last 70 years. The capacity to capture C was greatest along the coast in the scrub mangrove (−294 ± 0.02 g C m−2 y−1) and declined inland into marl prairies (−47 ± 0.03 g C m−2 y−1). Low resilience to current conditions was evident in marl prairies, a result of the legacy impacts of water diversion throughout the greater Everglades. Although the southeastern Everglades captured approximately 115 metric tons of C in 2021, if the ecotone continues to advance at 25 m y−1 over the next century, we project a 12 % increase (16 mt C y−1) in net CO2 capture. Results emphasize that initial functional responses to changes in conditions may not accurately represent long-term outcomes and highlight the role of brackish ecotone communities as the frontline for climate- and management-induced shifts in coastal ecosystem structure and function. This is the first study to use disequilibrium dynamics to understand landscape-level transitions and their implications for C capture.
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The magnitude and pace of photosynthetic recovery after wildfire in California ecosystems
Wildfire modifies the short- and long-term exchange of carbon between terrestrial ecosystems and the atmosphere, with impacts on ecosystem services such as carbon uptake. Dry western US forests historically experienced low-intensity, frequent fires, with patches across the landscape occupying different points in the fire-recovery trajectory. Contemporary perturbations, such as recent severe fires in California, could shift the historic stand-age distribution and impact the legacy of carbon uptake on the landscape. Here, we combine flux measurements of gross primary production (GPP) and chronosequence analysis using satellite remote sensing to investigate how the last century of fires in California impacted the dynamics of ecosystem carbon uptake on the fire-affected landscape. A GPP recovery trajectory curve of more than five thousand fires in forest ecosystems since 1919 indicated that fire reduced GPP by 157.4 ± 7.3 g C m − 2 y − 1 ( mean ± SE, n = 1926 ) in the first year after fire, with average recovery to prefire conditions after ∼ 12 y. The largest fires in forested ecosystems reduced GPP by 393.8 ± 15.7 g C m − 2 y − 1 ( n = 401) and took more than two decades to recover. Recent increases in fire severity and recovery time have led to nearly 9.9 ± 3.5 MMT CO 2 (3-y rolling mean) in cumulative forgone carbon uptake due to the legacy of fires on the landscape, complicating the challenge of maintaining California’s natural and working lands as a net carbon sink. Understanding these changes is paramount to weighing the costs and benefits associated with fuels management and ecosystem management for climate change mitigation.
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- Award ID(s):
- 1735040
- PAR ID:
- 10451405
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 120
- Issue:
- 15
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1073/pnas.2201954120
