Historic land use influences contemporary establishment of invasive plant species

The legacy of agricultural land use can have widespread and persistent effects on contemporary landscapes. Although agriculture can lead to persistent changes in soil characteristics and plant communities, it remains unclear whether historic agricultural land use can alter the likelihood of contemporary biological invasions. To understand how agricultural land-use history might interact with well-known drivers of invasion, we conducted factorial manipulations of soil disturbance and resource additions within non-agricultural remnant sites and post-agricultural sites invaded by two non-native Lespedeza species. Our results reveal that variation in invader success can depend on the interplay of historic land use and contemporary processes: for both Lespedeza species, establishment was greater in remnant sites, but soil disturbance enhanced establishment irrespective of land-use history, demonstrating that contemporary processes can help to overcome legacy constraints on invader success. In contrast, additions of resources known to facilitate seedling recruitment (N and water) reduced invader establishment in post-agricultural but not in remnant sites, providing evidence that interactions between historic and contemporary processes can also limit invader success. Our findings thus illustrate that a consideration of historic land use may help to clarify the often contingent responses of invasive plants to known determinants of invasibility. Moreover, in finding significantly greater soil compaction at post-agricultural sites, our study provides a putative mechanism for historic land-use effects on contemporary invasive plant establishment. Our work suggests that an understanding of invasion dynamics requires knowledge of anthropogenic events that often occur decades before the introduction of invasive propagules.