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Volume 102, Issue 6 e03320
Article

Mangrove growth response to experimental warming is greatest near the range limit in northeast Florida

Samantha K. Chapman

Corresponding Author

Samantha K. Chapman

Department of Biology and Center for Biodiversity and Ecosystem Stewardship, Villanova University, Villanova, Pennsylvania, 19085 USA

E-mail: [email protected]

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Ilka C. Feller

Ilka C. Feller

Smithsonian Environmental Research Center, Edgewater, Maryland, 21037 USA

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Gabriela Canas

Gabriela Canas

Guana Tolomato Matanzas National Estuarine Research Reserve, Ponte Vedra, Florida, 32082 USA

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Matthew A. Hayes

Matthew A. Hayes

Department of Biology and Center for Biodiversity and Ecosystem Stewardship, Villanova University, Villanova, Pennsylvania, 19085 USA

Australian Rivers Institute - Coast & Estuaries, Griffith University, Gold Coast, Queensland, 4222 Australia

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Nicole Dix

Nicole Dix

Guana Tolomato Matanzas National Estuarine Research Reserve, Ponte Vedra, Florida, 32082 USA

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Mark Hester

Mark Hester

University of Louisiana Lafayette, Lafayette, Louisiana, 70504 USA

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Jim Morris

Jim Morris

Baruch Institute for Marine & Coastal Research, University of South Carolina, Columbia, South Carolina, 29208 USA

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J. Adam Langley

J. Adam Langley

Department of Biology and Center for Biodiversity and Ecosystem Stewardship, Villanova University, Villanova, Pennsylvania, 19085 USA

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First published: 04 March 2021
Citations: 16

Corresponding Editor: Steven Pennings.

Abstract

Shrubs are invading into grasslands around the world, but we don’t yet know how these shrubs will fare in a warmer future. In ecotonal coastal wetland ecosystems, woody mangroves are encroaching into herbaceous salt marshes owing to changes in temperature, precipitation, and sediment dynamics. Increasing mangrove biomass in wetlands often increases carbon storage, which is high in these productive ecosystems, but little is known about how mangrove growth will change in response to warming. To address this knowledge gap, we deployed warming experiments at three coastal wetland sites along a latitudinal gradient in northeast Florida where Avicennia germinans, black mangroves, are encroaching into salt marshes. We achieved air temperature warming (+1.6°C during the day) at all three sites and measured stem elongation, canopy height and area changes, and leaf and node number. After 2 yr of warming, we found that mangrove growth rate in height increased due to warming. Warming increased stem elongation by 130% over unwarmed control plots after 1 yr at the northern site. Mangrove growth in canopy area did not respond to warming. Site differences in growth rate were pronounced, and mangrove growth in both height and area were lowest at the northern site, despite greater impacts of warming at that site. We also found that area-based relative growth rate was five times higher across all treatments than height-based relative growth rate, indicating that mangroves are growing wider rather than taller in these ecotonal environments. Our findings indicate that the growth effect of experimental warming depends on site characteristics and growth parameter measured. We also propose that differential mangrove growth across the three sites may be driven by biotic factors such as the identity of the salt marsh species into which mangroves are encroaching. Our results suggest that, as seen in other ecosystems, wetland plants may respond most strongly to warming at their poleward range edge.

Data Availability Statement

Data are available (Chapman et al. 2021) in Figshare: https://doi.org/10.6084/m9.figshare.13678999.v1