Agricultural land use is a leading cause of habitat degradation and loss of biodiversity. Post-agricultural sites (areas where agriculture has been abandoned) provide promising opportunities for recovery of biodiversity, however, many plant species fail to recolonize these habitats and remain trapped in areas without a history of agriculture (remnant sites). This may be caused by an inability of plant seedlings to grow or establish in post-agricultural sites or in post-agricultural soils. To test for establishment limitation in the field, we used a large-scale experiment in the longleaf pine savanna ecosystem where 27 post-agricultural sites abandoned >60 years ago are directly adjacent to remnant sites. We added seeds of 12 species indicative of remnant habitats to both remnant and post-agricultural sites and determined number of established species ~2 years later. To test altered soil conditions as a specific mechanism of post-agricultural establishment limitation, we collected soils from remnant and post-agricultural plots at 10 of our sites and grew 7 species in both soil types in the greenhouse.
Results/Conclusions
In both the lab and the field we found no evidence for establishment or growth limitation in post-agricultural sites compared to remnant sites. In response to our seed additions in the field, we found that a greater abundance and richness of sown species established in post-agricultural sites, opposite to what we predicted. In the greenhouse we found that the growth and survival of each species was not significantly different when grown in remnant and post-agricultural soils, and this was true for both full soil treatment (abiotic and biotic factors) and an inoculated soil treatment (only biotic factors). Our results show that if seeds arrive in our post-agricultural sites they can establish just as well in remnant sites as post-agricultural sites and that post-agricultural land use legacies on soil do not affect growth and survival. This suggests that dispersal limitation is a more important mechanism preventing plant species from returning to post-agricultural habitats and that recovery of these habitats would benefit from seed additions.