Plant traits explain the success of vacuum harvesting as a method of seed collection for the restoration of species-rich grasslands

Abstract

Grassland restoration is a key measure for re-establishing damaged floral communities. As seed banks are often degraded, methods are needed to overcome dispersal limitation of the remnant vegetation. One approach is to vacuum harvest seeds from donor sites. While this is a cost-effective method, individual species' traits describing reproduction methods and dispersal mechanisms may affect the success with which seeds are collected and subsequently germinate. We collected seeds using low-cost vacuum harvesters in species-rich meadows in Poland. We predicted the relative success with which seedlings emerged from this collected material with respect to their percentage cover in the donor sites on the basis of individual species' functional traits. Prolific species that rely on seed as opposed to vegetative reproduction, and those that germinate in late summer/autumn, exhibited the highest level of emergence. To a lesser extent, drought-tolerant or shade-intolerant species were well represented in the collected material. There was also weak evidence that wind-dispersed seeds would have a higher likelihood of being collected by this method. Our results suggest that vacuum harvesting is a valuable method to collect seeds for use in grassland restoration; however, it has limitations. In particular, additional methods may be needed to introduce into grassland restoration sites the propagules of species that vegetatively reproduce or seed early. The overrepresentation of species that produce large numbers of seed may potentially introduce priority effects that could also have unintended long-term implications for the structure of the floral community.