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Abstract Climate‐driven ecosystem shifts occur through turnover in the foundation species which structure the landscape. Therefore, to predict the fate of areas undergoing climate‐driven ecosystem shifts, one approach is to characterize ecological and evolutionary responses of foundation species along dynamic environmental gradients. One such gradient is the ecotone between tidal marshes and maritime forests in coastal areas of the US Mid‐Atlantic region where accelerated sea‐level rise and coastal storms of increased frequency and intensity are driving forest dieback and inland marsh migration. Mid‐Atlantic tidal marshes are structured by marsh grasses which act as foundation species, and these grasses exhibit trait variation across their distribution from established marsh interior to their inland migration front. We conducted a reciprocal transplant experiment withSpartina patens, a dominant high marsh grass and foundation species, between established populations in the high marsh and range edge populations in the forest understory at three Mid‐Atlantic sites. We monitored environmental conditions in marsh and forest understory habitats, measured plant traits (above‐ and belowground biomass, specific leaf area, leaf N and C concentrations) in transplanted and reference non‐transplanted individuals, and used microsatellite markers to determine the genetic identity of transplants to quantify clonality between habitats and sites. Individuals transplanted into the forest understory exhibited a plastic shift in resource allocation to aboveground structures associated with light acquisition, with shifts in transplants making them more morphologically similar to reference individuals sampled from the forest habitat. Clonal diversity and genetic distance among transplants were relatively high at two of three sites, but individuals at all sites exhibited trans‐habitat plasticity regardless of clonal diversity or a lack thereof. Individuals grown in the forest understory showed lower vegetative and reproductive fitness. Nevertheless, the trait plasticity exhibited by this species allowed individuals from the forest that were transplanted into the marsh to recoup significant biomass in only a single growing season. We predict high plasticity will facilitate the persistence of colonizingS. patensindividuals under suboptimal forest shade conditions until forest dieback increases light availability, ultimately promoting continued inland migration of this foundation species under sea‐level rise.
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Retreating coastal forest supports saltmarsh invertebrates
Abstract As sea‐level rise converts coastal forest to salt marsh, marsh arthropods may migrate inland; however, the resulting changes in arthropod communities, including the stage of forest retreat that first supports saltmarsh species, remain unknown. Furthermore, the ghost forest that forms in the wake of rapid forest retreat offers an unknown quality of habitat to marsh arthropods. In a migrating marsh in Virginia, USA, ground‐dwelling arthropod communities were assessed across the forest‐to‐marsh gradient, and functional use of ghost forest and high marsh habitats was evaluated to determine whether marsh arthropods utilized expanded marsh in the same way as existing marsh. Diet and body condition were compared for two marsh species found in both high marsh and ghost forest (the detritivore amphipod,Orchestia grillus, and the hunting spider,Pardosa littoralis). Community composition differed among zones along the gradient, driven largely by retreating forest taxa (e.g., Collembola), marsh taxa migrating into the forest (e.g.,O. grillus), and unique taxa (e.g., Hydrophilinae beetles) at the ecotone. The low forest was the most inland zone to accommodate the saltmarsh speciesO. grillus, suggesting that inland migration of certain saltmarsh arthropods may co‐occur with early saltmarsh plant migration and precede complete tree canopy die‐off. Functionally,O. grillusoccupied a larger trophic niche in the ghost forest than the high marsh, likely by consuming both marsh and terrestrial material. Despite this, both observed marsh species primarily consumed from the marsh grass food web in both habitats, and no lasting differences in body condition were observed. For the species and functional traits assessed, the ghost forest and high marsh did not show major differences at this site. Forest retreat and marsh migration may thus provide an important opportunity for generalist saltmarsh arthropods to maintain their habitat extent in the face of marsh loss due to sea‐level rise.
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- Award ID(s):
- 1832221
- PAR ID:
- 10611143
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Ecosphere
- Volume:
- 15
- Issue:
- 1
- ISSN:
- 2150-8925
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Ghost forests, consisting of dead trees adjacent to marshes, are a striking feature of low-lying coastal and estuarine landscapes, and they represent the migration of coastal ecosystems with relative sea-level rise (RSLR). Although ghost forests have been observed along many coastal margins, rates of ecosystem change and their dependence on RSLR remain poorly constrained. Here, we reconstructed forest retreat rates using sediment coring and historical imagery at five sites along the Mid-Atlantic coast of the United States, a hotspot for accelerated RSLR. We found that the elevation of the marsh-forest boundary generally increased with RSLR over the past 2000 yr, and that retreat accelerated concurrently with the late 19th century acceleration in global sea level. Lateral retreat rates increased through time for most sampling intervals over the past 150 yr, and modern lateral retreat rates are 2 to 14 times faster than pre-industrial rates at all sites. Substantial deviations between RSLR and forest response are consistent with previous observations that episodic disturbance facilitates the mortality of adult trees. Nevertheless, our work suggests that RSLR is the primary determinant of coastal forest extent, and that ghost forests represent a direct and prominent visual indicator of climate change.more » « less
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/ecs2.4743
