The soil aggregate structure as a marker of the ecological niche of the micromollusc Vallonia pulchella

The article discusses the role of the soil aggregate structure in quantifying the marginality and specialisation axes of the ecological niche of the micromollusc Vallonia pulchella (Muller 1774) that inhabits technosols. The experimental polygon consisted of 105 samples located within 7 transects (15 samples each). The distance between rows of sampling points was 3 m. The average density of V. pulchella was 1393 ind.∙m–2. The soil aggregate fraction of 1–5 mm was found to be predominant within the technosol. The spatial variation of aggregate fractions was characterised by a moderate level of the spatial dependence. It was impossible to choose an adequate covariance model from among the traditional ones to interpolate the spatial variation of aggregate fractions, and only the Matérn model was best suited. The axis of marginality and specialisation of the V. pulchella ecological niche projected in soil aggregate fractions was significantly different from a random alternative. The ecological niche of the V. pulchella was presented by integral variables, such as the axis of marginality and specialisation, which were the basis to build a map of the spatial variation of the habitat suitability index. The marginality of the V. pulchella ecological niche correlates with soil penetration resistance indicators at depths ranging from 0–5 to 20–25 cm, soil humidity, acidity, and aeration. The specialisation correlates with the soil mechanical impedance at 25–35 cm, nitrogen content, and the soil acidity regime.