Characterizing saltmarsh vegetation using in situ observations and UAV data: a case study in the Venice lagoon

The geomorphological system, dynamics and spatial distribution of plant species of coastal salt marshes are poorly understood. They are unique systems, which must always grow in height in order to be at peace with the sea level rise. For this reason, the vegetation present as well as the accumulation of organic matter in the marsh accretion process is of utmost importance. There is a lack of information on the spatial distribution with which it is possible to gather information on the existing dynamics in this ecosystem, especially because it has a great variety of species and species associations. By using the spatial distribution of species, vegetation biomass and in situ observations in a study area, much of these dynamics and functioning can be understood. The present work presents results of data obtained by in situ sampling and data collected by UAVs in the San Felice marsh (Venice lagoon, Italy). The study area hosts at least twelve species of halophytes grouped in six main associations. Samples were collected in September 2021, providing spatially georeferenced data and samples on the distribution of vegetation associations, above- and below-ground biomass, vegetation height, bulk density and soil organic carbon content. The results suggest (i) the importance of the spatial distribution of the different plant associations as a function of elevation above mean sea level, (ii) the importance of studying the carbon stock capacities in relation to the soil elevation, (iii) a positive correlation between soil elevation and bulk density values. In addition, the results show the importance of studying salt marshes using different sources of information obtained by remote sensing.