Soil properties determine how Lasius flavus impact on topsoil organic matter and nutrient distribution in central Germany

Abstract

Yellow meadow ant (Lasius flavus) mound building activity alters the physico-chemical properties of grassland soils. In this study, L. flavus mediated changes were assessed along vegetation and soil type differences within four plots located on two study sites. Fine soil, cold- (readily soluble) and hot-water extractable (labile) organic matter (OM) and nutrient fractions of four L. flavus mounds (0–5 cm and 5–10 cm sampling depth) and four control locations (0–5 cm sampling depth) each, were quantified. All three fractions were further assessed in the horizons of each soil type and complemented by measures of aboveground biomass and vegetation indices related to plant species and composition (Ellenberg indicator values, Shannon-Diversity and Evenness).The surface area covered by L. flavus mounds and mound density exhibited site and plot related differences, attributed to differences in the soil moisture and -fertility regime, as well as to aboveground biomass. The mound building activity led to a depletion of fine soil, readily soluble and labile OM and sulfur stocks, while mineral-derived fine soil nutrient stocks (calcium (Ca), magnesium, potassium, iron and phosphorous) were higher in the mounds. Effects of L. flavus activity were most pronounced in a Haplic Stagnosol and an Umbric Leptosol (calcaric), possibly due to stronger contrasts between topsoil and subsoil OM, as well as lower Ca stocks in comparison to the other soils (Stagnic Luvisol and Stagnic Leptosol).This interplay of nutrient depletion and enrichment introduced through the bioturbation by L. flavus, may create a topsoil providing suitable habitat conditions for the establishment of plant species adapted to poor organic nutrient availability. Thus, promoting and preserving L. flavus mounds may be an important tool to establish resource heterogeneity and hence floral diversity in Central European grasslands.