Tree logs for grassland restoration? Lessons from an unintentional experiment

For subtropical Brazilian grasslands, few restoration techniques are established, and seeds of native grassland species are not available on the market. Here, we evaluated the effect of physical barriers (PB) on vegetation recovery in a degraded grassland. We considered species that exhibit attributes in their diaspores that facilitate dispersal as well-dispersed species (WDS) and compared the proportion of WDS at our site to their proportion in the regional species pool. To analyze plots near and distant from the PB, we calculated the extrapolated metrics by an asymptotic estimator (double sample size of each distance). We found 74 species in the degraded area, with higher richness and Shannon diversity values closer to logs, but higher Simpson values with larger distance from logs. Almost half of the species in the degraded area are WDS, more than in the regional species pool. While effects of logs on microsite conditions may also play a role (e.g. logs accumulating organic material or increasing soil moisture, providing shade), our data indicates that the PB works as a seed trap favoring the occurrence of WDS. It seems promising to develop applications in restoration, especially when associating PB with other restoration techniques to increase availability of adequate germination and establishment conditions.