Ecosystem engineering by foxes is mediated by the landscape context—A case study from steppic burial mounds

In intensively used landscapes, remnant grassland fragments are often restricted to places unsuitable for agricultural cultivation. Such refuges are the ancient burial mounds called “kurgans,” which are typical landscape elements of the Eurasian steppe and forest steppe zone. Due to their hill‐like shape, loose soil structure and undisturbed status kurgans provide proper habitats for burrowing mammals. Accordingly, grassland vegetation on kurgans is often exposed to bioturbation, which can influence the habitat structure and plant species pool. In our study, we explored the effect of fox burrows and landscape context on the habitat properties and vegetation composition of small landscape elements, using kurgans as model habitats. We surveyed the vegetation of fox burrows and that of the surrounding grassland on five kurgans situated in cleared landscapes surrounded by arable lands and five kurgans in complex landscapes surrounded by grazed grasslands. We recorded the percentage cover of vascular plants, the amount of litter, and soil moisture content in twelve 0.5 m × 0.5 m plots per kurgan, in a total of 120 plots. We found that foxes considerably transformed habitat conditions and created microhabitats by changing the soil nutrient availability and reducing total vegetation cover and litter. Several grassland specialist species, mostly grasses (Agropyron cristatum, Elymus hispidus, and Stipa capillata) established in the newly created microhabitats, although the cover of noxious species was also considerable. We found that landscape context influenced the sort of species which could establish on kurgans by affecting the available species pool and soil moisture. Our results revealed that foxes act as ecosystem engineers on kurgans by transforming abiotic and biotic conditions by burrowing. Their engineering activity maintains disturbance‐dependent components of dry grasslands and increases local environmental heterogeneity.