Transgressive dune fi elds often comprise a multiplicity of landforms where vegetation processes largely affect landform dynamics, which in turn, also affect vegetation processes. These associations have seldom been studied in detail. This paper examines four separate landform types in a complex coastal transgressive dunefi eld located in the central Gulf of Mexico, in order to assess the relationships between dunefi eld habitat, local environmental factors, vegetation associations and landform evolution. Topographic surveys using tape and clinometer were conducted in conjunction with vegetation survey transects at four locations across the Doña Juana dunefi eld. Vegetation surveys allowed the estimation of relative plant cover of each plant species found along the transects. A large variety of landforms were found at the Doña Juana Dunefi eld: defl ation plains, gegenwalle (counter) ridges, transverse dune trailing ridges, blowouts and parabolic dunes, aklé (fi sh-scale shaped) dunefi elds and precipitation ridges, with plant species associations developing on these different landforms equally variable. Flood tolerant species were located in the lower parts (defl ation plain and gegenwalle ridges) whereas the older and dryer parts were covered by coastal matorral shrubs. Burial-tolerant species were dominant in the most mobile areas (blowouts and aklé dunefi eld and margin). The dune trailing ridge, with relatively milder conditions, showed the highest richness, with no dominant species. A dual interaction was found such that colonizing species both create and affect topography, and in turn, topography determines vegetation association and succession patterns. In coastal dunes, the vegetation and abiotic environment (namely the different landforms and the inherent micronevironmental variability) interact tightly and generate a complex and highly dynamic biogeomorphic system where substrate mobility and colonization processes reinforce one another in positive feedback.

Salt marshes occupying the tidal fringe of estuaries and protected coasts provide valuable ecosystem services, and remote sensing is a powerful tool for their large-scale monitoring. However, in order to apply remote sensing techniques to evaluate the ecological state of salt marshes, a deeper understanding is needed about the interactions between field biophysical parameters and the sensor's reflectance. The main objective of this work is to analyze and quantify the influence of different biophysical parameters characterizing stands of Spartina alterniflora marshes in the Bahia Blanca Estuary, Argentina, on their spectral response. Spectral reflectance at high resolution was measured in S. alterniflora canopies under natural conditions, manipulating standing biomass by means of successive harvestings. Reflectance data were acquired using a FieldSpect spectroradiometer, which measures in the visible, near-infrared, and shortwaveinfrared spectral bands. Based on these reflectance data, spectral indices such as the normalized difference vegetation index (NDVI) were calculated for each biomass condition. Biomass, leaf area index (LAI), percent canopy cover (PCC), water content, and soil properties were also evaluated. LAI, PCC, and biomass were positively correlated between each other. As a general trend, as biomass decreased, absorption in red wavelengths decreased and reflectance in nearinfrared increased. Several indices explained the variability in LAI, biomass, and PCC. For example, NDVI Rouse had a positive regression with PCC (R 2 ¼ 0.80, N ¼ 75) and LAI (R 2 ¼ 0.67, N ¼ 75). Results indicate that LAI, biomass, and PCC of Spartina alterniflora could be accurately determined from spectral data.

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The aim of this study was to identify and characterize the main plant communities in a temperate coastal wetland using high-resolution imagery. We produced a map of Samborombón Bay at 1:25,000 scale using a WorldView-2 image. An Object-based Image Analysis approach was chosen, and an unsupervised classification algorithm was applied. Overall classification accuracy was 81%, and the Kappa index was 78.1%. Six land cover types were mapped including four main natural monospecific plant communities. The lower intertidal area was dominated by mudflats without vegetation and stands of Bolboschoenus maritimus. The middle intertidal area was dominated by Sarcocornia ambigua, while, in the higher intertidal area, Sporobolus densiflorus and grasslands with Cortaderia selloana prevailed. We found four spatial patterns at a landscape scale, based on the presence and spatial distribution of the natural plant communities. This map represents a valuable tool for future studies on wetland environmental indicators. ARTICLE HISTORY