High-intensity sheep grazing impoverishes soil seed banks in sand grasslands

Livestock grazing is the most widespread management tool for sustaining grassland biodiversity worldwide. Studying grazing effects on the vegetation composition is quite frequent, research on its effects onthe biodiversity and density of soil seed banks is scarce. We studied the effects of livestock type (e.g., sheep or cattle) and grazing intensity on the soil seed bank of species-rich sand grasslands. Altogether 25 grazed grasslands classified into four grazing intensity categories were studied; and their soil seed bank was analysed. We tested the following hypotheses: i) Diversity and density of soil seed banks are lower in sheep-grazed sites than in cattle-grazed ones. ii) Species composition, diversity, and density of the soil seed banks are more strongly affected by grazing intensity than by the livestock type. We found that sheep grazing sustained a much lower density of total seed bank regardless to grazing intensity. Livestock type mainly affected the seed bank density, while grazing intensity had a major significant effect on most of the variables. Most of the studied variables were affected by the interaction of grazing intensity and livestock type. We emphasise that i) livestock type must be carefully selected and high-intensity sheep grazing should be avoided in the long-run, and ii) for a sustainable grazing management and to meet nature conservation goals, grazing intensity and livestock type should be considered simultaneously.