Wednesday, April 18, 2012

Apr 16, 2012: Erv's Field Notes #31

Eastern red cedar on prairie upland in western edge of the park, 2/17/12 (Kevin Kane)

Sunday, April 15, 2012, 1:30-2:30 pm. Sunny. Strong southerly wind. Temperature: 75 degrees F. The Hayden Park watershed had a good rain Saturday night. Water level in the penultimate pond of the middle wetland was at normal full pool and a flow of water was spilling into the lake for the first time since last summer. I saw a female Red-breasted Merganser on the south lake and three Variegated Meadowhawks (dragonflies) patrolling the shoreline. I also saw a small garter snake along the bike path.

Here is the information on “invasive species” that I promised in the last field note. There are several definitions of invasive species (see Wikipedia). The usual definition is: plants or animals that are introduced (non-native) and adversely affect the habitat or bio-region they invade environmentally, economically, and/or ecologically. You may have heard of the problems that Burmese phythons are causing in the Florida everglades. Examples of invasive animals in Iowa include zebra mussel and silver carp. The Ring-necked Pheasant is a non-native species that was introduced early in the 20th Century but is not considered invasive because there is no evidence that it causes adverse effects in Iowa. Examples of invasive plants in Iowa include purple loosestrife, European buckthorn, honeysuckle, smooth brome, birdsfoot trefoil, Canada thistle, and many more.

Ada Hayden Heritage Park is not devoid of invasive species. The few invasive animals we have seen are causing minimal adverse effects. The common carp causes few or no problems in the main lake but when it invades the shallow wetlands they stir up the bottom sediment and the reduced transparency of the water inhibits plant growth. Wolf Oesterreich has observed a few red-eared turtles, a species native to the southern United States whose normal distribution barely gets into southeast Iowa. These turtles are often sold as pets and then later discarded by their owners in places they don't belong.

Invasive plants in the park include Siberian elm, honeysuckle, smooth brome, crown vetch, and yellow sweet clover. If we broaden the definition, we might consider any woody plant that invades the reconstructed prairie to be invasive. Native species such as willow, cottonwood, and Eastern red cedar fall into this category. Most woody species that invade prairies can be controlled by fire. The Eastern red cedar, Juniperus virginiana, has become a problem in the grasslands of southern and western Iowa and in northern Missouri because the use of fire has been suppressed for many decades. Land managers in these areas refer to the cedar as the “green glacier” because of the way it slow creeps across the landscape. Complete eradication of Eastern red cedar poses a dilemma for managers because it is a beneficial species for wildlife.

Carl Moen has taken an interest in the reconstructed prairie next to his home in Stonebrooke and has been using mechanical means to remove invading tree saplings. Carl has prudently asked permission of parks staff before doing this. Carl, Jon Hunstock, and I recently met with Kevin Shawgo, Parks Superintendent, to discuss invasive species control. We offered our assistance in mapping the distribution of the most troublesome invasive species and then eventually to offer management advice on their control. I have obtained aerial photos of the park and delineated 68 areas to be surveyed for invasive species. This survey may take the better part of the summer to complete depending on how many volunteers we can recruit to help with this effort. Anyone wishing to help with this effort please contact me. If you are unsure of how to identify the species of concern, I am willing to spend some time training you.

My early observations suggest that Siberian elm is rapidly spreading. Removal of several large elm trees that are producing seed may need to be done. In the meantime, young elms need to be removed before they begin producing seed.

Erv Klaas

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