Past agricultural activity and current vegetation cover are consistent predictors of invasion and spread of Sericea at local and landscape scales

Background/Question/Methods

Invasibility of plant communities at local scales is affected by factors that alter resource availability such as resident species composition, species diversity, and disturbances at local scales. However, at larger scales the number of invading individuals and other factors such as land use, habitat type and topography may be more predictive of invasion. We conducted a field invasion experiment and analyzed large-scale distribution patterns of the invasive legume Lespedeza cuneata (Sericea) in eastern Kansas to explore 1) How attributes of the recipient community, invader propagule pressure, and disturbance affect Sericea establishment in restored and non-restored abandoned land and 2) How land use history, habitat type, and topography predict Sericea invasion at landscape to regional scales. We conducted an incomplete factorial experiment where restored and non-restored plots were seeded with high and low levels of Sericea propagule pressure. Some high seeded plots were moderately disturbed to determine if Sericea invasion was enhanced by physical disruption of the plant community. Secondly, surveys of Sericea populations were conducted across a varied-land use landscape at Ft. Riley Reservation in 2002 and in 2011 to investigate rates of Sericea invasion in relation to plant community composition and land use histories.

Results/Conclusions

In experimentally restored plots, Sericea establishment was significantly reduced by 93% and 99% relative to non-restored plots at high and low propagule pressure respectively (p<0.001 and p<0.001). Furthermore, disturbance had no effect on Sericea invasion in restored plots. Preliminary analysis of Sericea distribution at Ft. Riley reveals that while abandon crop land makes up 33% of Ft. Riley’s land cover, 64% of the increase in area of invaded land from 2002-2011 was in this land type. In contrast, while tallgrass prairie makes up 38% of the land area, it contained only 25% of the increase in area of invaded land over the same time period. Both studies show that native prairie vegetation is more resistant to invasion than other grassland land use types suggesting that agricultural activity without active restoration to native vegetation leaves land particularly susceptible to Sericea invasion. Furthermore, these factors are consistent at local and landscape scales making them particularly relevant for statewide efforts to control Sericea invasion.