RESUMEN
Coastal zones are characterized by the interactions between continents and oceans and, therefore, between fresh and salt surface and groundwater. The wetlands of coastal zones represent transitional ecosystems that are affected by these conditions, although little is known about the hydrogeochemistry of wetlands, especially coastal wetlands. In the present study, the hydrogeochemical characterization of coastal freshwater herbaceous wetlands in the Ciénaga del Fuerte Protected Natural Area in Veracruz, Mexico, in the American tropics was carried out per plant community. Four herbaceous wetlands (alligator flag, saw grass, cattail, and floodplain pasture) were monitored to understand the origin of the water feeding these ecosystems, the hydrogeochemical composition of groundwater, and the relationship between the groundwater and ecology of these ecosystems during dry and rainy seasons. The results indicate that Ciénaga del Fuerte is located in a regional discharge area and receives local recharge, so it is fed by both regional and local flows. The chemical composition varied temporally and spatially, creating unique conditions that determined the habitat occupied by the hydrophytic vegetation. The spatiotemporal behaviour of groundwater is one factor that, along with the hydroperiod, determines wetland dynamics and affects wetland biota (ecohydrogeochemistry). Generalist plant communities established in zones of local recharge, whereas other more specialized and/or plastic communities inhabited zones receiving regional flows with greater ion concentrations. This information forms the basis for establishing an appropriate scale (municipal, state, or larger regions) for the sustainable management of goods and services provided by the wetlands.
RESUMEN
Wetlands are interconnected with the larger surrounding landscape through the hydrological cycling of water and waterborne substances. Therefore, the borders of individual wetlands may not be appropriate landscape system boundaries for understanding large-scale functions and ecosystem services of wetlandscapes (wetland network - landscape systems), and how these can be impacted by climate and land-use changes. Recognizing that such large-scale behaviours may not be easily predicted by simple extrapolation of individual wetland behaviours, we here investigate properties of 15 Swedish wetlandscapes in the extensive (22 650 km2) Norrström drainage basin (NDB) comprising as many as 1699 wetlands. Results based on wetland survey data in combination with GIS-based ecohydrological analyses showed that wetlands located in wetlandscapes above a certain size (in the NDB: ~250 km2) consistently formed networks with characteristics required to support key ecosystem services such as nutrient/pollutant retention and biodiversity support. This was in contrast to smaller wetlandscapes (<250 km2), which had smaller and less diverse wetlands with insufficient throughflow to significantly impact large-scale flows of water and nutrients/pollutants. The existence of such wetlandscape-size thresholds is consistent with scale-dependent flow accumulation patterns in catchments, suggesting likely transferability of this result also to other regions.
RESUMEN
It is a generally accepted theory that ecological functions are enhanced with increased diversity in plant communities due to species complementarity effects. We tested this theory in a mesocosm study using freshwater submerged plant beds to determine if increasing species number caused overyielding and species complementarity. We applied a maximum of four species in the plant beds corresponding to the typical species number in natural freshwater plant beds. We found no clear effects of species number (1-4) on biomass production and thus no conclusive overyielding and complementarity effect. This may be explained by low species differentiation among the four species in plant traits relevant for resource acquisition in freshwater, or that other species interactions, e.g. allelopathy, were inhibiting overyielding. The existing knowledge on species complementarity in aquatic plant communities is sparse and inconclusive and calls for more research.