Thomas P. Rooney and David A. Rogers. 2011. Invasive Plant Science and Management: July-September, Vol. 4, No. 3, pp. 317-325.
Frequency of occurrence plant data from the 1950’s (pre-invasion) were compared to similar data collected from the same sites in the 2000’s. Garlic mustard, European buckthorn and Bell’s honeysuckle were absent from all study sites 50 years ago, yet at least one invasive plant was present in 77.7% of the stands in the 2000’s. All three species were present in 14.9% of the stands. Garlic mustard and European buckthorn were found at 47.9% of resurveyed sites, and Bell's honeysuckle was found in 40.4% of resurveyed sites. Native understory plant species density declined an average of 23.1% during the past 50 yr.
Read more at: http://www.bioone.org/doi/abs/10.1614/IPSM-D-10-00084.1