Friday, August 12, 2016
ESA Exhibit Hall, Ft Lauderdale Convention Center
James E. Cook, College of Natural Resources, UW-Stevens Point, Stevens Point, WI
Background/Question/Methods The restoration of wet (sedge) meadows typically involves the introduction of wetland-associated species. In these cases of mitigation or federal cost-sharing, the manager needs a specific level of wetland obligates on the site within 5 years. However, there is very little documentation of the specific compositional changes that take place within this period, nor is it known if there are ecological ‘losses’ associated with “directed succession”. We documented compositional dynamics, and changes in relative abundance of dominant species, in a 7 ha sedge meadow in central WI. Intense restoration measures were taken, and 23 species were seeded in 2010. In 2011 a permanent, systematic array of 103 sample points was laid out along 23 transects. In these, cover by species was occularly estimated in early fall 2011, 2012, 2014, 2015, and mid-summer, 2012. In 2012, 2014 and 2015 approximately 40 of these plots were re-inventoried. Relative cover of the dominant species, species density, total richness and percent wetland obligate were estimated. To evaluate overall compositional change, NMS ordination was utilized. To assess the significance of changes from 2011 – 2015, paired t-tests were used. Results/Conclusions
From 2011 to 2014, total fall cover increased from 35 to 75%, and then declined in 2015. Concurrently, cover contributed by wetland obligates increased from 36 to 96%; in contrast, species density declined from 7.2 to 3.0 species/quadrat (p < 0.01). The dominants were sedges, rushes or grasses. The relative abundance of the top two dominants ranged from 56% (fall, 2011) to 49% (summer, 2012) to 80% (2015). The dominant species shifted rapidly to wetland obligates (wool grass and common rush) and one of the two was dominant in 90% of the quadrats by 2015. Several relatively common species in 2011/12 declined precipitously by 2015. The ordination indicated a strong convergence of the quadrats over time. The seed bank and water appear to have been important sources of colonizers. Thus, by YR4 the system had two ‘super dominants’ emerge, a loss in species density and homogenization of composition. This accelerated succession probably has important implications in that it reduced the period of semi-open habitat. It is questionable if this simplification of the system, which appears to be highly stable, is desirable.
