Submerged macrophyte zonation in a Mediterranean salt marsh: a facilitation effect from established helophytes?

Abstract

Abstract. The relationship between communities of submerged annual macrophytes (predominately Chara spp.) and environmental characteristics is studied in three habitats with different dominant perennial species (Arthrocnemum, Juncus, Scirpus) and areas of bare soil. The distribution of submerged annual macrophytes is significantly dependent on two independent environmental factors: a dominant gradient of flooding/salinity, and a secondary gradient of nutrients related exclusively to the combined abundance of helophytes of the genus Scirpus (S. maritimus and S. litoralis). The results suggest that these emergent helophytes (1) are able to modify water column parameters (such as concentration of nitrates, phosphates, potassium, and bicarbonates) which are important for the communities of submerged macrophytes, and (2) play a fundamental role in the generation of secondary sources of environmental variability which, superimposed on the main gradient of flooding/salinity, favours the appearance of new compositional equilibria in such communities. The existence of a process of facilitation is discussed by which the emergent helophytes induce changes in nutrient availability that would favour relatively nutrient‐demanding charophyte species (such as Chara connivens and Nitella hyalina), altering the established relationships with other coexisting charophytes (such as Chara canescens and C. galioides) that dominate in the absence of the facilitating species. Nevertheless, the increased nutrient concentration associated to the presence of helophytes would not introduce significant changes in the total biomass of submerged aquatic macrophytes.

The impact of vertic soil cracks on submerged macrophyte diaspore bank depth distribution in Mediterranean temporary wetlands

“…During the dry period the study area shows abundant cracks in the soil (as deep as at 0-20 cm; Clemente et al, 1998), covering 15-25% of the soil surface. In the study area, NaCl is the dominant salt (Espinar et al, 2002) and wind dispersion of soil is very common during dry seasons. The wind transports clay, silt, submerged macrophyte litter, and fine salt crystal, which together accumulate in some areas to form what are locally named ''polveros.''…”

Long-Term Monitoring of the Flooding Regime and Hydroperiod of Doñana Marshes with Landsat Time Series (1974–2014)

“…The flooding gradient has been identified as a major driver for the distribution of emergent helophytes and submerged macrophytes [75]. Submerged macrophytes do play a major role in the marsh metabolism [38].…”

Ecological similarities between two Mediterranean wetlands: Sidi Boughaba (North-West Morocco) and the Doñana National Park (South-West Spain)

“…4), although up to 42.5% has been previously reported (Serrano, 1992). The highest concentration of organic matter (42%) in the Merja Sidi Boughaba was associated with an area of extensive growth of Typha angustifolia, similarly to how higher concentrations of sediment organic matter have been associated with the presence of large emergent macrophytes in the Doñana marshland (Espinar et al, 2002;Reina et al, 2006). This large accumulation of organic matter in the sediment is indicative of highly productive systems, as expected for a shallow water body such as this with a permanent or semi-permanent regime that receives very high solar irradiance: the annual mean for global radiation in these southern Mediterranean sites is about 1750-1850 kW h m -2 , while this value is almost half for the coastal dunes of The Netherlands or Denmark (www.meteonorm.com).…”