Vegetation change in semi-permanent or ephemeral montane marshes (lagoons) of the New England Tablelands Bioregion

Abstract

The vegetation communities within semi-permanent or ephemeral montane marshes colloquially known as lagoons are an under investigated wetland type of the New England Tablelands Bioregion (NETB) yet they are listed (Upland Wetlands) on both state and federal acts as endangered. Lack of survey and analysis of plot data has meant that the variation in vegetation due to zonation, seasonality and unpredictable wetting and drying cycles are poorly understood. Here, 317 full floristic 2 × 2-m plots were placed across 13 lagoons. The plot data were classified to allow description of native and novel vegetation types using the hierarchical EcoVeg schema. The updated classification includes one Division and Macrogroup with 15 Alliances and 47 Associations. Permanent 50-m transects with a 1 × 1-m plot at every 5 m (10 per transect) were placed within lagoons. Five lagoons were resurveyed annually for 3 years. Within transects, each plot was assigned an Association after each survey period. Approximately one third of transect plots changed in vegetation type each year, often at the Alliance level. Over the 3-year period the number of Associations reduced by ~30% across transects associated with increasing drought and drying out of the wetlands. Transitional environments with the greatest level of hydrological periodicity had the greatest variety of Associations recorded. Highly dynamic systems with increased temporal turnover are likely to require increased sampling effort both spatially and temporally than more stable vegetated systems. The constant changing nature of these communities poses significant issues for management and conservation planning, including benchmarking and offsetting, which may require novel solutions.