Similar vegetation trends were observed for marshes as noted in upland areas ; aerial imagery ( 2015 - 2021 ) shows increased productivity in the long-term and satellite imagery ( 2019-2022 ) shows decreases in vegetative health in the short-term . We also note there were several areas in satellite imagery showing significant decreases with high correlations . A likely cause of this downward trend in recent productivity is an 18-week moderate drought in 2022 which impacted growth early in the growing season and into late June . Much of the literature suggests fresh groundwater flow through the marsh and rainfall dilutes porewater salinity in marsh sediments which reduces salinity stress on marsh vegetation ( Xin et al , 2022 ). While most marsh grasses generally adapted to high salinity environments , the production of biomass is higher under reduced salinity conditions ( Linthurst and Seneca , 1981 ; Wieski and Pennings , 2014 ). A reduction in freshwater flow from ground and rainwater through the marsh , conditions of which occur during periods of drought , has the potential to reduce the productivity of marsh vegetation . Likewise , infrequent introduction of fresh rainwater into soil pore spaces can also impact vegetative growth in the marsh . Further research on the effects of drought and tidal influence on marshland vegetation in the Lowcountry and continued analysis of conditions of marshes within the watershed is needed to better understand these linkages .
UVVR analysis of aerial imagery from 2021 shows that areas in the central portion of the Kiawah River have particularly low vegetative cover , while areas in the eastern and western portions are mostly vegetated . This analysis provides an indicator for sections of the marsh with high vegetation which are more resilient to changes and retain marsh sediments ( Ganju et al ., 2017 ; Ganju et al ., 2020 ). Areas with low vegetation ratios are correlated with deficiencies in the net sediment budget , however , the ecological benefit of unvegetated areas to estuarine organisms should be considered . Mud flats , for example , generally do not contain much vegetation , but provide feeding areas for wading birds and recruitment sites for oyster reefs . Some of the areas in the central portion of the Kiawah River have remained mud flats and prime oyster beds since the 1850s . Growth of mudflats and observations of newly formed bare soil areas will be of concern in future observations . Analysis of marsh sections over time will provide additional insight into the changing status of marsh sections , with other indicators , such as oyster reef abundance , providing us with more information about the ecological integrity of the marsh .
Tidal Salt Marsh
Jackie Guzy