Mediterranean vineyard soil seed bank characterization along a slope/disturbance gradient: Opportunities for land sharing

Abstract

The Mediterranean region is predicted to experience more intense rainfall events separated by severe droughts due to climate change. In agrosystems, the intensification of rainfall on dry bare soils will lead to an increase in runoff and erosion rates, especially on slopes. A common method to reduce erosion is to cover the soil with vegetation. To save costs, this vegetation could be provided by the soil seed bank. Vineyards situated on slopes are part of the typical Mediterranean landscape; thus, developing vegetation cover inside vineyards could be a solution to fight growing erosion risks in addition to providing other valuable services. However, the relationship between slope, erosion and seed loss can vary. Another key ingredient in the development of spontaneous vegetation cover is the spatial dispersal of seeds from one place to another, but the amount of seeds displaced depends on their respective dispersal modes. In this study, we sampled the soil seed bank at two sites characterized by either a low or high frequency of vegetation removal. The soil seed bank was sampled along a transect starting upslope of the vineyards to the bottom of neighboring agricultural ditches. Germination trials were carried out to define the soil seed bank in terms of species and seed density. Each identified species was linked with a main dispersal mode. Our main objective was to assess the effect of vegetation cover on seed loss inside a vineyard, as well as the potential differences in the soil seed bank along our transect and the influence of dispersal mode on those differences. Despite previous contradictory literature, vegetation did not seem to protect interrows from seed loss caused by runoff. Overall, our results support the use of the soil seed bank to provide spontaneous vegetation cover to limit present and future erosion rates and advocate for relaxing vegetation removal operations.