Creative Inquiry students set up 16 Carolina Vegetation Survey (CVS) plots in the restored and unrestored section in the stream and wetland to monitor the success of the mitigation plan. CVS plots allow the students to monitor the stem count and percent cover in each plot. Realizing attempts to have minimal invasive plants in the restored section would be futile while the upstream portion of Hunnicutt Creek is heavily invaded, they expanded their survey areas. They established 25 more CVS plots in the forested parts throughout campus. The initial data showed 100% native trees in the tree strata but the herb, shrub, and vine strata are dominated by invasive plants. The main species of concern are Chinese Privet (Ligustrum senense), Thorny Olive (Elagenus pungens), English Ivy (Hedera helix), and Kudzu (Pueraria montana).
For the purpose of research, of the 25 CVS plots located upstream of the restoration area, four methods of removal were conducted to determine which option would provide best results for removing the prominent understory invasives. The methods or removal were mechanical, chemical, mechanical and chemical, and prescribed grazing.
The main target species:
Chinese Privet (Ligustrum sinense)
English Ivy (Hedera helix)
Japanese Honeysuckle (Lonicera japonica)
Kudzu (Pueraria montana)
Mimosa (Albizia julibrissin)
Multiflora Rose (Rosa multiflora)
Oregon Grape (Mahonia bealei)
Silverthorn (Elaeagnus pungens)
Wisteria (Wisteria sp.)
Mechanical removal involves use of loppers, hand saws and other hand tools to cut down plants and hand pulling. It is an environmentally friendly method of removal, however it may not be the most efficient in comparison to other methods. Caution needs to be taken when manually removing plants so that soil is not highly disturbed leading to erosion. Many invasive plants can spread via rhizomes and thus taking out the entirety of the root is imperative.
There are two common systemic herbicides (active ingredients either glyphosate or triclopyr) that are used when doing chemical control. Glyphosate absorbs into the plant tissue and carried to the roots. Being a non-selective herbicide, caution must be taken to minimize off target impacts. Triclopyr is a selective herbicide for broadleaf plants (forbs, shrubs, and trees). Basal bark application, and foliar treatment are the main treatment methods for chemical control. Timing and seasons are integral when planning to use a systemic herbicide because of their ability to translocate in the plant. Aquatic friendly herbicides are being used due to the close proximity of the stream. Proper personal protective equipment is worn including long sleeve shirts, long pants, goggles, gloves and closed toe shoes.
Mechanical plus Chemical:
Using teams of three, one person cuts the target species, one applies herbicide to the cut stump, and another drags the cut plant to a designated pile. This was intially determined the most effective method with minimal pesticide usage. The active ingredient in the herbicide is triclopyr. Triclopyr is a selective herbicide for broadleaf plants (forbs shrubs, and trees).
Prescribed Grazing :
After the goat crew has a chance to graze the understory, the Hunnicutt Creek Research Team follows up and uses the mechanical and chemical removal techniques describes above.
The two pictures below are from the summer of 2018 where the research team cleared a stream bank. This banks understory was almost all Silverthorn and Chinese Privet before the team cleared it out. Now that the invasive species are removed, the native trees have more resources available and there is a better chance for the native understory species ( such as Calycanthus floridus) to survive. The Left picture is the bank before the removal and the right picture is afterwards.