Data for: Plant thresholds and community composition of coastal marsh-forest ecotones in the US Northeast

Sea level rise is causing coastal salt marshes to migrate upslope into coastal forests and other terrestrial ecosystems.  However, the factors that control marsh migration rates are not well understood, particularly in the US Northeast, where this phenomenon has received little attention. To determine the relationship between environmental variables and plant species composition in marsh migration zones, we examined plant coverage and environmental data for three sites experiencing marsh upslope migration in New Jersey, New York, and Massachusetts that varied in slope from 1-3%. We found that only 10% of the variation in plant community composition was explained by inundation time, while models containing multiple predictor variables, including edaphic variables, explained much greater levels of variance. Random forest models predicting native halophyte presence /had accuracies of 69 – 84%, with salinity, flooding duration, and light availability as key predictors. The most accurat..., Site Descriptions
Three sites in the northeast exhibiting forest retreat along the marsh-forest ecotone were chosen for study, including Waquoit Bay (WB), Massachusetts (41.5562°, -70.5057°), part of the Waquoit Bay National Estuarine Research Reserve. The site has a tidal range of 0.61 m and an ecotone-upland slope of 3.45% ± 0.46. The second site, Pine Neck, is part of Pine Neck Preserve in East Quogue, NY (40.8422°, -72.5644°) and is managed by the Nature Conservancy. This site has a tidal range of 0.78 m and an ecotone-upland slope of 2.12% ± 0.58. The southernmost site selected was Egg Harbor, part of the Tuckahoe Wildlife Management Area (39.3259°, -74.6502°) in southern New Jersey. This site has a tidal range of 1.14 m and has the lowest slope of the three, 1.80% ± 0.64. Soils along the marsh-upland border transitioned from muck (classified as Freetown and Swansea muck) or Transquaking peat at low elevations to sandy soils (Carver coarse sand, Deerfield loamy sand, Plymouth loamy..., , # Data for: Plant thresholds and community composition of coastal marsh-forest ecotones in the US Northeast

[https://doi.org/10.5061/dryad.5tb2rbpcm](https://doi.org/10.5061/dryad.5tb2rbpcm)

Data includes the following files: Ecotone_PlantSpp-EnvData.csv, EggHarborSamplingPoints.zip, PineNeckSamplingPoints.zip, WaquoitSamplingPoints.zip, EggHarborWatershed.zip, PineNeck_Watershed.zip, WaquoitWatershed_final.zip, EggHarborUpperBorder.zip, PineNeckUpperBorderWaypoints.zip, WaquoitUpperMarshBoundary.zip,EggHarborTreeline_C_points.zip, EggHarborTreeline_D_points.zip, EggHarborTreeline_E_Points.zip, PineNeckTreeline_B_Points.zip, PineNeckTreeline_C_Points.zip, PineNeckTreeline_D_Points.zip, Waquoit_Treeline2_Points.zip, Waquoit_Treeline3_Points.zip, and Waquoit_Treeline4_points_v2.zip.

## Description of the data and file structure

The three zipped files: EggHarborSamplingPoints.zip, PineNeckSamplingPoints.zip, and WaquoitSamplingPoints.zip are shapefiles for sampling points at Egg Harbor...,