We have two great challenges to rehabilitating and maintaining the ecosystems in the Back Woods…controlling non native invasive plant species and the limitations on using prescribed fire (another post for the future). Our battle with one invasive plant species, air potato (Dioscorea bulbifera), has been the subject of many blog posts in past. This time in three parts we will take a broader look at the topic of invasives in the Back Woods. Part I covers invasive vine species, part II herbs and shrubs, and part III trees.
In these posts you will see reference to Category I and Category II invasive species. These designations are defined as follows by the Florida Exotic Pest Plant Council (FLEPPC).
Invasive exotic plants are termed Category I invasives when they are altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives. This definition does not rely on the economic severity or geographic range of the problem, but on the documented ecological damage caused. Category II invasive exotics have increased in abundance or frequency but have not yet altered Florida plant communities to the extent shown by Category I species. These species may become Category I if ecological damage is demonstrated.
The battle in the Back Woods against non native invasive plant species is ongoing. Even with extensive professional contractual spraying, hundreds of volunteer hours of mechanical removal, and countless additional follow up herbicide treatments many non native invasive plant species still have a foothold in the Back Woods. Many of these invasive species may be eliminated and reintroductions more easily eradicated but, a few key species will likely be a management concern for years to come. Invasive species compete with our native species for growing space and resources. Some can actually change the ecological function of the forest affecting hydrology and fire frequency. Controlling these species is a critical component in our restoration efforts. A common but interesting side effect of some of the treatments has been the release of other species previously less noticeable. Treating and removing smothering masses of air potato as well native grape vine (Vitis rotundifolia) opens up the canopy allowing more light and water to the ground. This has had the desired effect of opening up the growing space for many native herbs and shrubs but also released masses of another invasive species, the skunk vine (Paederia foetida), everywhere. This vine is but one of many of our nemeses in the battle for the Back Woods.
Vines top our list of least welcome invaders. Without fire as a disturbance to interrupt their growth; unchecked they can quickly cover cleared areas, smother midstory vegetation, and climb into the canopy of trees. This growth not only alters the structure of the vegetation of the forest, it increases the possibility of tree loss should we have a wildfire. Vines climbing into the canopy are termed “ladder fuels” which can carry fire into the canopy and destroy otherwise fire tolerant tree species such as longleaf pine (Pinus palustris.) Some of our viney invaders include air potato (Dioscorea bulbifera), skunk vine (Paederia foetida) , and Japanese climbing fern (Lygodium japonicum).
- Air potato is a very persistent species. This Category I invasive species produces aerial tubers call bulbils along the vines. Bulbils, some no larger than the end of your fingernail, can be produced by the hundreds and each one can produce a new vine unless removed or destroyed. Removing or treating the vines and picking up and disposing of bulbils are key to controlling the vine. Fortunately for us, reintroduction of air potato is usually limited to bulbils floating in on water or vines encroaching from neighboring properties. Water does not come into the property from other sources so, if we can control the vine at our borders we may eventually be able to significantly curtail air potato growth in the Back Woods.
- Skunk vine was introduced to Florida at the turn of the 20th century as a potential fiber crop (the stem is very rubbery and strong) and quickly escaped cultivation to become a Category I invasive species. This vine was spotty through out our little woods and only found extensively in only a couple of places near the wetland. As noted earlier, after some significant removal of other competing vines the skunk vine started popping up in more places. It can regenerate from broken stems and it spreads readily from seed. We are tackling this invasive with herbicide and mechanical removal and have to take great care not to spread it ourselves in the removal process. Those tough rubbery stems also make for very difficult removal from the canopy. It may be possible for skunk vine seed to be carried in by birds which can be a source of continued reintroduction.
- Japanese climbing fern, a Category I invasive species, found its way to Florida in the 1930’s as an ornamental plant. Established first in the northern parts of the state it has been making its way southward. [A related fern species the old world climbing fern (Lygodium microphyllum) was introduced in the south and is progressing northwards. It is considered potentially the most threatening species to Florida’s natural areas. A battle line has been drawn at Interstate 4 to prevent the old world climbing fern from invading the sensitive ecosystems of the Green Swamp (the source of four of our local rivers and drinking waters) and from moving further north.] Japanese climbing fern can grow just about anywhere but we find it mainly along the margins of the wetlands and wetter flatwoods areas. With frond that can grow up to 90 feet this fern can easily reach the top of the pine canopy and shade out vegetation below. This species is only spotty throughout the Back Woods. Key to its control is to eliminate it before spores are produced in the fall. Spores spread from even great distances may present a continued source of reintroduction.
- One native species, muscadine or wild grape (Vitis rotundifolia), has a place on our nuisance species list. Even this native species can become problematic. Unregulated by any disturbance such as fire, the growth of grape vines can have similar ecologically altering effects as non native vines. You may notice that we use many of the same control measures for grape vines that we do for the non native species. Rest assured though, the grape has a place in our forest ecosystems. You find a sign describing the plant along the trail at a particularly large example of their woody vines…and of course in the midst of summer you find me grazing on their wonderful fruit!
Next week… in the middle of our list of bothersome plants are a few non native invasive herbs and shrubs.
If you are looking for a great work out we are always looking for intrepid volunteers to help out in our battle against invasives.