WETFEET: Mangrove and marsh growth responses to warming across a latitudinal gradient.csv

In the southeastern US, Avicennia germinans (black mangrove) is encroaching poleward due to warming temperatures and a decrease in annual freee events. To understand how warming will continue to impact mangrove encroachment, we deployed open-top passive warming chambers at three sites along the northeast coast of Florida encompassed by the Guana Tolomato Matanzas National Estuarine Research Reserve. At each of the 3 sites, we established 4 treatments; warmed mangrove, control mangrove, warmed marsh, and control marsh (3 sites x 4 treatments x 6 replicates). Mangrove height and canopy widths were measured in each of the 36 plots (3 sites x 2 treatments x 6 replicates) at the outset of the experiment in May 2018 and then again in November 2018 (6 months) and in May 2019 (1 year). Plant height was measured to the tallest branch. Canopy width was measured at the widest dimension and then again at the dimension perpendicular from the first measurement.In each plot, two PVC rings were placed over existing salt marsh vegetation. In August 2018, we measured the height and number of stems (stem density) of each species present in the biomass rings. All biomass was then cut at the base for allometric measurements in the lab. This process was repeated in August 2019.To assess belowground root biomass, we took 30cm soil cores from each plot using a gauge auger in May 2018 and again in May 2019. Cores were split into two sections; 0-15cm depth, and 15-30cm depth. Each section was washed free from sediment, and remaining root biomass was dried in a 60 degree C oven and weighed.<br><br>Starting in 2020, a 30 x 30 cm permanent aluminum quadrat was installed in each plot over existing salt marsh vegetation. We measured the stem density of each species present in the quadrat, and the heights of 3 stems per species. If mangrove seedlings were present in the quadrat, we measured all seedlings present. Using initial soil cores from 2018 and final soil cores from 2021, we subsampled the soil at 5cm, 15cm, and 30 cm depth along each soil core. Soil subsampled was dried, ground, and tinned for C:N analysis. C:N analysis was completed at Smithsonian Isotope Mass Spectrometry Facility.<br>