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Title: Transient vegetation dynamics in a tropical coastal wetland: Sea‐level rise, glycophyte retreat, and incipient loss in plant diversity
Abstract Aim and Questions

Sea‐level rise has been responsible for extensive vegetation changes in coastal areas worldwide. The intent of our study was to analyze vegetation dynamics of a South Florida coastal watershed within an explicit spatiotemporal framework that might aid in projecting the landscape's future response to restoration efforts. We also asked whether recent transgression by mangroves and other halophytes has resulted in reduced plant diversity at local or subregional scales.

Location

Florida’'s Southeast Saline Everglades, USA.

Methods

We selected 26 locations, representing a transition zone between sawgrass marsh and mangrove swamp, that was last sampled floristically in 1995. Within this transition zone, leading‐ and trailing‐edge subzones were defined based on plant composition in 1995. Fifty‐two site × time combinations were classified and then ordinated to examine vegetation–environment relationships using 2016 environmental data. We calculated alpha‐diversity using Hill numbers or Shannon–Weiner index species equivalents and compared these across the two surveys. We used a multiplicative diversity partition to determine beta‐diversity from landscape‐scale (gamma) diversity in the entire dataset or in each subzone.

Results

Mangrove and mangrove associates became more important in both subzones: through colonization and establishment in the leading edge, and through population growth combined with the decline of freshwater species in the trailing edge. Alpha‐diversity increased significantly in the leading edge and decreased nominally in the trailing edge, while beta‐diversity declined slightly in both subzones as well as across the study area.

Conclusions

Recent halophyte encroachment in the Southeast Saline Everglades continues a trend evident for almost a century. While salinity is an important environmental driver, species’ responses suggest that restoration efforts based on supplementing freshwater delivery will not reverse a trend that depends on multiple interacting factors. Sea‐level‐rise‐driven taxonomic homogenization in coastal wetland communities develops slowly, lagging niche‐based changes in community structure and composition.

 
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Award ID(s):
2025954
NSF-PAR ID:
10510056
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ;
Publisher / Repository:
International Association for Vegetation Science
Date Published:
Journal Name:
Journal of Vegetation Science
Volume:
35
Issue:
3
ISSN:
1100-9233
Page Range / eLocation ID:
e13267
Subject(s) / Keyword(s):
coastal tropical wetland transient vegetation dynamics Florida's Southeast Saline Everglades USA, glycophyte retreat halophytes encroachment incipient loss in plant diversity mangroves and associates' transgression sea-level rise wetland restoration through freshwater delivery
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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