Alterations in soil microarthropod/microflora communities in a Mediterranean sand dune ecosystem
Coastal sand dunes are unique dynamic ecosystems characterized by strong abiotic gradients from the shore landward. The proximity to the sea generates those environmental gradients, which affect the living organisms in such an ecosystem. The effect is very well known in relation to plant, arthropod, and vertebrate communities, but there is very little knowledge on soil biotic communities. The soil microflora and mesofauna are often neglected, and little is known on the effect of those gradients on these populations. Soil biota are known for their important role in nutrient cycling and decomposition in terrestrial ecosystems. The soil inhabitants are especially important in sandy areas, where they influence the maturation and stabilization of sand dunes. The Mediterranean coastal sand dune ecosystem is characterized by harsh climate conditions and is, therefore, defined as a semi-arid habitat. The Caesarea sand dunes are a unique ecosystem in the Mediterranean region due to their state and communities, which are vanishing before our eyes for anthropogenic reasons. We examined the effect of distance from the sea on the soil microarthropod and microbial communities. The soil samples were collected from two depths in open sandy areas at five locations along a 4-km transect, from the seashore inland.
Soil microarthropod-community composition and soil microbial-community functionality in coastal sand dunes were found to be significantly affected both spatially and temporally along the environmental gradient. Both microarthropod density and microbial biomass reached maximum values during the wet season due to the interplay between abiotic parameters, i.e., soil moisture and temperature, with an increasing trend in population density and biomass from the seashore landward. The lowest microarthropod density and microbial biomass were found during the dry season, when the differences in soil physico-chemical properties along the gradient were less distinct. Microbial functional diversity was consistently higher during the wet season than during the dry season, with an increasing trend landward in the lower layer. Microarthropod diversity exhibited similar patterns, but with an increasing trend found in both layers during the wet season. Our study suggests that the shore-normal environmental gradient affects not only the vertebrates and invertebrates above the sand, but also the microarthropods and microflora of the sandy ecosystem, where the intensity of these fluctuations is season-dependent.