Published online by Cambridge University Press: 20 January 2017
Flea beetles (Aphthona spp.) were released in the Little Missouri National Grasslands (LMNG) in western North Dakota in 1999 to control leafy spurge. The changes in leafy spurge density and soil seedbank composition were evaluated on two ecological sites 10 yr (2009) after Aphthona spp. release to monitor the effectiveness of the insects on weed control and the associated changes in plant communities. In 2009, leafy spurge stem density averaged 2 and 9 stems m−2 (0.19 to 0.84 ft−2) in the loamy overflow and loamy sites, respectively, compared with 110 and 78 stems m−2, respectively, in 1999. Leafy spurge constituted nearly 67% of the loamy overflow seedbank in 1999, compared with 2% in 2009. In the loamy seedbank, the weed represented nearly 70% in 1999, compared with approximately 15% in 2009. As leafy spurge abundance was reduced, native species richness and seed count increased 10 yr after Aphthona spp. release. Late seral species represented 17% of the loamy overflow seedbank in 2009, an increase from 5% in 1999. However, Kentucky bluegrass, a nontarget weedy species, increased more than 250% in the loamy overflow seedbank. Late seral species were 38% of the loamy seedbank in 2009, compared with 13% in 1999. The number of native species increased from 31 in 1999 to 39 in 2009 in the loamy overflow seedbank, but only changed from 32 to 34 species in the loamy site during the same period. The reestablishment of native species has been slow, but seedbank analysis indicates the number and type of species found before the leafy spurge infestation have increased. Planting native species in selected areas may have reduced the lag time in these species return to the seedbank and reduced invasion from other nondesirable species, such as Kentucky bluegrass.
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