This post is part of a series that highlights sections of our forest management plan for Otter Point Woods.
Invasive plants are bad plants. Okay, that definition is overly simplistic, but it does capture the general idea. Invasive plants are generally non-native or alien to a particular ecosystem and, most importantly, cause harm to the environment, economy, or human health (USFS, MISIN). Here are a few of the ones I’m most concerned about in our woods:
Reed canary grass (Phalaris arundinacea) poses the greatest management challenge of any plant species that is currently present on the property. This aggressive, cool-season grass is widespread across the property in open areas and along trail edges. It is also common in the forest understory in some parts of the property, particularly farther west on the property. Reed canarygrass is a major threat to the ecological integrity of wetland ecosystems by outcompeting other plants, homogenizing habitat structure, and altering hydrology, nutrient cycling, and carbon storage (WDNR). The grass is a prolific colonizer of open and disturbed sites and spreads by seed, stem fragments, and rhizomes. There is some confusion about whether this grass species is native to the region; it is suspected that non-native varieties or crosses of native and non-native varieties have contributed to the species’ heightened aggressiveness (USFS).
This species is notoriously difficult to control. Although several options are available (e.g., mowing, burning, herbicides, tree planting), treatments typically need to be repeated for several years to restore native vegetation (WDNR). In the near term, management at Otter Point Woods will likely focus on restricting the expansion of reed canarygrass to new areas. Reed canarygrass is well-poised to expand into areas where the forest canopy cover is reduced; areas containing substantial amounts of ash are most likely to have forest canopy removed either through forest harvest in advance of emerald ash borer or from actual pest mortality. When possible, managing light conditions is the most effective way to reduce reed canarygrass expansion. Reed canarygrass may need to be controlled around tree plantings to reduce competition with the desired species; mowing is probably the most effective control method in these situations, particularly when it is timed to limit seed development. Targeted use of herbicides or other control methods may be necessary in some instances.
Other Bad Plants
Beyond this, there are currently few issues with invasive plant species on the property. Many non-native species are present on the property (such as clover, plantain, lilac, black walnut), but these species do not have invasive characteristics. Species that have been noted as being of concern are:
- Non-native honeysuckle (Lonicera spp.) plants appear to have been established for quite a long time in some places. Several (~10) large shrubs have been found dispersed across the property. These plants appear in isolated locations as large shrubs and do not seem to be expanding quickly.
- Japanese barberry (Berberis thunbergii) is likely present in isolated locations on the property. A few individual plants were found and treated (cut and basal application of herbicide) west of the field. It may be present on the north end of the property, and several large patches are present nearby on adjacent parcels to the north. Many plants are established in full shade along an old road, with heavy seed production occurring in the fall.
- Boxelder (Acer negundo) is a native species common to the bottomland forest type present across much of the property. However, the species is sometimes considered invasive because of its ability to outcompete more desirable vegetation (IPAUS). Cut trees can stump and root sprout, so it may be necessary to apply herbicide to the stump of cut trees or kill sprouts through repeated cutting or burning with a propane torch (eXtension).
There are many invasive species that have been identified in the Upper Peninsula (KISMA) and these species are often spread when their seeds become attached to a persons’s boots or clothing and then fall off in another location. Given the low landscape position of the property and commonality of flooding, it is likely that high water levels are a key driver of seed movement for invasive plant species. For example, Japanese barberry is most common in or immediately adjacent to the low-lying and flood-prone areas in original channel of the Sturgeon River (i.e., where the river flowed prior to 1913), while honeysuckle plants seem to be common along sandy river banks. Even with control of existing invasive species, the property’s location within the watershed may make it vulnerable to future invasions of these and other invasive plants that may be introduced upstream. Common buckthorn (Rhamnus cathartica) and glossy buckthorn (Frangula alnus) are important species of concern, as these species are present elsewhere in the western U.P. and would be highly competitive on the property given the soil and site conditions.
We will be monitoring our invasive plants to ensure that existing populations do not spread and to detect new plant species that may be of concern. If the plant cannot be identified, we’ll contact a forest scientist, ecologist, or botanist to identify the plant, determine if it is native or non-native, and make recommendations for its removal, if necessary. Invasive plant species will be removed with mechanical or, if necessary, chemical treatments, with appropriate precautions taken to protect soil and water resources