The Effects of Fertilization and Time of Cutting on Regeneration and Seed Production of Dipsacus laciniatus (Dipsacacae)
M.P. Dudley
J.A.D. Parrish
S.L. Post
C. G. Helm
R.N Wiedenmann
We studied effects of fertilization and time of cutting on the regeneration of cutleaf teasel (Dipsacus laciniatus L.)at the Mascoutin Recreation Area at Clinton Lake, Dewitt County, Illinois, for two growing seasons. D. laciniatus is an exotic European invasive species that infests natural habitats across much of the United States and southern Canada. We established fourteen 5.0-m x 5.0-m paired plots, seven fertilized and seven unfertilized. Each set of paired plots was assigned one of seven cutting treatments, including no cutting, or one of six cutting times from 3 June to 10 August 2002. We measured stem height, number of heads per individual plant, number of seeds per head, and seed viability. We found no significant difference between plant heights or number of heads per individual in fertilized versus unfertilized plots. Reproductive success significantly increased when D. laciniatus had more time to grow after cutting. If cutting occurred before flower buds opened in early July, no significant difference in number of heads produced was found between cut and uncut D. laciniatus. If cutting occurred after flowers developed, then the stalk height, number of heads, seeds produced per plant, and total number of viable seeds all significantly decreased. Therefore, it appears that mowing areas containing cutleaf teasel in the Midwest may be an effective control, but only if performed after rosettes have committed to bolting, before seeds are viable, and late enough in the growing season to prevent reproductive regrowth.
Population Trends in Northern Monkshood, Aconitum noveboracense, at Four Sample Intervals Over Fifteen Years
Cathy Mabry
Cathy Henry
Connie Dettman
Aconitum noveboracense A. Gray ex Coville (northern monkshood) is a federally threatened plant species of the blue-flowered Aconitum section (Napellus) that occurs in Iowa, Wisconsin, Ohio, and New York, with most populations in Iowa. Monitoring of 12 populations in Iowa over a 15-year period showed substantial periodic variation in all population parameters, although less variation in adult density. Variation among sites was only detected for the proportion of quadrats with fruiting plants, and overall, adult and juvenile density. Our analysis provided a mixed view of the status of this species. On one hand, after a substantial decline between the 1994/95 and 2001/02 sample intervals, overall population density and density of each life stage increased and nearly recovered between the 2001/02 and 2004/05 sample intervals. Conversely, all our measures of reproduction – number of fruits/plant, proportion of quadrats with fruiting plants, number of fruits/node – indicated reduced vigor, as in the same intervals these measures declined and did not recover. Soil temperature was highly correlated with juvenile and adult density. Measuring additional biotic and abiotic factors should be incorporated into future monitoring. Local-scale abiotic factors that could influence variation in adult and juvenile density include light levels, drought, distance to cold air vents, soil moisture, nutrient levels, and humidity. Biotic factors, particularly herbivores, pollinator availability, and garlic mustard (Alliaria petiolata (M. Bieb.) Cavara & Grande), are also likely to have an impact on the IowaAconitum populations.