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Management Recommendations These suggestions are going two focus on two main topics: 1) Oak Regeneration and 2) Forest Health (monitoring of tree health and the reduction of non-native invasive plant species). These suggestions are based on a forester’s perspective so it will be important for the City of Iowa City and the Friends of Hickory Hill to determine together what the long-term goals for the vegetation in the park are, before management decisions can be made. Oak Regeneration Looking at the historical and current inventory information on this park oak (mostly white oak and bur oak along with some black and red) and some shagbark hickory were likely the most common tree species on this property between the mid 1800’s and the early 1900’s. As the vegetation in the park has developed in recent years there is very little to almost no new oak regeneration developing. There are some younger stands of shagbark hickory that began developing in the mid 1900’s (Stands 3, 11, and 12). Most of this is due to the fact that there has most likely been little disturbance in this park since the early 1930’s to promote sun-loving species such as oak. Instead species such as bitternut hickory, white ash, black cherry, hackberry, and basswood (that are more adaptive to shade and faster growing) have established in the understory of most of the established oak stands. The bottom line is that the majority of the oak in the park are over mature and some are in declining health, and if nothing is done soon to reverse this trend in some locations the amount of oak in the park will most likely decline in the near future. The best way to promote oak regeneration is to create openings around established oaks that can produce acorns. The two main areas in the park where there are large established white oak are stand 1 and stand 6. Also, there are a few large oaks on the north edge of field 8 that have already been cleared around, and there is actually some new oaks coming in the adjacent grass field to the north. Consider allowing any new oaks and shagbark hickory to invade the edge of this grass field, and protect some of these new oak seedlings from the deer using cages.  The two main options for creating openings in established stands of oak include prescribed fire and mechanical removal of understory vegetation. Prescribed fire can be a good tool to remove/kill some understory vegetation in these stands, but if it is not used correctly it can severely damage or kill the large mature oaks. Since this park is within the city limits smoke management would be a significant concern of any prescribed fire. The are a number of folks within Iowa City (some are members of the Friends of Hickory Hill Park) that have significant knowledge of prescribed burning that can be utilized for assistance. **VERY IMPORTANT: If ever burning, be sure to have a burning plan, a permit from the City of Iowa City, assistance, create firebreaks around the burn area, notify the local fire department, local police and sheriff, and neighbors before the fire is set. The practice of burning in forested areas is fairly new in Iowa, and the benefits and methods are still being investigated. As more information on this practice becomes available I will pass it along to you. If the city decides to consider prescribed burning use it a few years then evaluate the stands to see if there is a need to mechanically remove some of the understory. If prescribed burning is not an option or it only eliminates some competition remove the understory trees (elm, white ash, bitternut hickory, basswood, ironwood, black cherry, and hackberry) to create a more open-woodland like area and to encourage the natural reseeding of desirable species such as oak. **Note: Do not do this work between March and October 1 to avoid wounding any existing oaks during the removal activities. Wounding oaks at this time can make them more susceptible to the fungus that causes the disease oak wilt.** Removal of the less desirable trees will open the area up to more sunlight, and will allow oak and shagbark hickory seedlings to get established. Remove all non oak and shagbark hickory species less than 4 inches in diameter and treat the stumps with a herbicide labeled for this use to prevent re-sprouting. Do not remove any live butternut during these activities. Trees being eliminated that are larger than 4 inches should be killed standing by cutting flaps or a double girdle with a chainsaw all the way around the trunk and treating these wounds with a herbicide labeled for such use. Chemicals used in performing these practices must be applied according to authorized use, label direction, and other federal or state policies and requirements. Evaluate the new open areas every year the first few years to see if any new oak and shagbark hickory are becoming established. If there is no new oak regeneration within the first 3 or 4 years consider planting some seedlings with cage protection for deer.   Note on Herbicides: The label is the law! You must follow the label exactly. If any instructions in this plan are contrary to the label that is in your possession, then contact the DNR Forester for consultation. Herbicides must be used in accordance with their labels.   Tree Health Through the summer (a couple times) each year take a walk through the main tree stands (1, 2, 3, 4, 5, 6, parts of 9, 10, 11 and 12) to see if any trees are showing problems. Symptoms to look for during your walks include: small or distorted leaves, browning, yellowing, or wilting leaves, dieing branches or trees, or trees that just do not look right. With the presence of oak in stands (1, 3, 4, 5, 6, 7, parts of 9, and 10) there is the potential of having a problem with a disease called oak wilt. This is a disease found in Iowa on oaks, and it is caused by a fungus. The trees in Iowa most commonly impacted by this disease are species such as red and black oak, but it can infect white and bur oak also. If red, northern pin, or black oak are infected by the fungus that causes this disease they usually die within the summer they are infected. White oak and bur oak can often take a number of years before they succumb to this disease after infection. The key for you in this situation is to continue to monitor for problems such as this, and to contact the District Forester’s office if problems are found. One way to avoid the potential transfer of the fungus that causes oak wilt problems is to not prune or wound oaks between March 1st and October each year. The best time to prune oaks is during the dormant season.   Currently, in Iowa we are starting to see a symptom on white oaks called “tatters” (see below). This problem has become more common in Eastern Iowa over the last 5 to 10 years, and the cause has not been determined yet (see enclosed pest alert on tatters). In some parts of Iowa we have begun to lose large white oaks, and in some cases these trees have been tattered over the last few years. It is not time to panic, but it will be important to continue to monitor stands 1, 4, and 6 for possible changes. If you see any major changes in the health of the oak give me a call, and I will come out and evaluate the situation.  Any vines on desirable trees in any of the stands that are getting up into the crown and competing for light should be cut.  Invasive Species Alert
Monitoring, reducing, and eliminating invasive species in the park now will help promote the natural beauty of the area. By taking an aggressive approach now to manage undesirable invasive species, you will significantly reduce the potential negative impact that invasive species could have on the park. There has already been a significant effort to slow-down the spread of garlic mustard in the park. This will be a very long-term battle. It is important that while battling garlic mustard that some of the significant woody exotic invasive plants found in the park are not ignored. Woody plants such as exotic honeysuckle and European cranberrybush viburnum are becoming significant in some stands. Other species such as barberry, buckthorn, privet, multi-flora rose, and tree-of-heaven are also threats to the park and can be found in some locations already. Consider identifying some priority stands such as stand 1, 6, 12, 11, 4, 3, and 5 in order and going after non-native invasive plants found in those stands. There are a few methods that can be utilized to manage these plants, please contact me for more specific management information. Below are shrub and tree species observed during my walk through the park: Shrubs gooseberry (Ribes species) dogwood (Cornus species) *barberry (Berberis species) *multi-flora rose *exotic honeysuckle (Lonicera species) hazelnut (Corylus americana) wild plum (Prunus americana) *autumn olive (Elaeagnus umbellata) chokecherry (Prunus virginiana) *privet (Ligustrum species) *buckthorn (Rhamnus species) *European cranberrybush viburnum (Viburnum opulus) elderberry (Sambucas canadensis) sumac (Rhus species) *non-native exotic shrubs Trees pagoda dogwood (Cornus alternifolia) black cherry (Prunus serotina) black oak (Quercus velutina) red oak (Quercus rubra) white oak (Quercus alba) basswood (Tilia americana) cottonwood (Populus deltoides) black walnut (Juglans nigra) ironwood (Ostrya virginiana) Eastern redcedar (Juniperus virginiana) bitternut hickory (Carya cordiformis) willow (Salix species) hackberry (Celtis occidentalis) shagbark hickory (Carya ovata) white ash (Fraxinus americana) mulberry (Morus species) bur oak (Quercus macrocarpa) boxelder (Acer negundo) honeylocust (Gleditsia tricanthos) sugar maple (Acer saccharum) aspen (Populus species) butternut (Juglans cinerea) river birch (Betula nigra) red elm (Ulmus rubra) American elm (Ulmus americana) silver maple (Acer saccharinum) hawthorn (Crataegus species) *catalpa (Catalpa species) sycamore (Platanus occidentalis) *tree-of-heaven (Ailanthus altissima) * Non-native species Literature Cited Hirokawa, K.E. 2003. Hickory Hill Past, Present and Future: A Vegetation Analysis and Management Plan. Thesis. University of Iowa. |