Looking to the future: the ugly, the bad, and the good

Climate change and global warming is something we have all heard of (regardless of whether or not you “believe it”…which we won’t get into today). It is a reality that we all face, humans and animals and plants alike. We know that climate change is causing more extreme weather patterns and events, general global warming at unprecedented rates, and countless stressors on the natural world. 

However, today, as per usual with my blog, I will be focusing on two invasive plants, kudzu and Japanese honeysuckle, and their relationships to climate change.

Over the course of this blog, we have discussed numerous impacts of kudzu and honeysuckle, most of which focused on smaller-scale issues. But the time has come to dive into the heavy stuff, the issues that are wide-reaching and, in my opinion, the most important in terms of the future. In this post, I will be looking into the future at the good, the bad, and the ugly that climate change may bring out of these invasive plants.

When considering impacts of climate change on invasive species, I think Hellmann et al. (2008) put it best. Her three final points of impact were: (1) the effects on the distribution of invasive species, (2) how climate change may affect the impact of existing invasive species, and (3) the “altered effectiveness of control strategies”. Here, we will discuss these three points in relation to our favorite invasive plants, kudzu and honeysuckle.

The Ugly: Increased invasive distribution

The idea of kudzu being able to expand its distribution because of climate change goes back to the early 1990s, when the “southern menace” was seen thriving in northern states such as Maryland, Delaware, Pennsylvania, New Jersey and New York (Alderman, 1998). Kudzu had been long established in the American south, so much so that it became somewhat entrenched in the culture. As Figure 1 shows, there were businesses named after the plant. This spread in distribution of kudzu is shown in Figure 2, with predicted range in 2100, only 80 years from now. An article published in 2010 by Bradley et al., uses modeling to predict how climate change will increase the range of kudzu. They concluded that under the most extreme climate change models (that is, what will happen if nothing is done to slow it down), that kudzu will establish itself north into Ohio, Pennsylvania, New York, and New England states within the next 80 years.

Figure 1: Kudzu Grill in Sandersville, Georgia. Image pulled from Alderman, 1998.

Figure 2: These images depict current vs future (year 2100) range of kudzu. The future map is modeled using predictive models of climate change by Bradley et al., 2010.

Similarly to kudzu, honeysuckle is also expected to increase its reach across the country because of global warming and the increased area of habitable environments. Both these species’ ranges are controlled by minimum temperatures, that is how cold it gets in the winter. But with this temperature rising globally, it stands to reason the restrictions on these invasives ranges will be lifted. That being said, honeysuckle will begin colonizing higher elevations than it had previously, impacting the mountainous forested areas of the Appalachians (Lemke et al., 2011). Not only will it expand vertically along mountains, but it is also expected to spread northwest through Mississippi, Tennessee, Kentucky, and Arkansas, and eastward towards Alabama and Virginia (Wang et al., 2012).

The Bad: Ecological & atmospheric impacts of this increased range

Now that we’ve talked about how these species may spread into the future due to global warming, let’s talk about how these expansions may (or may not) impact the ecosystems they are establishing in. A 2013 study by Hickman and Lerdau showed that kudzu invasions in these “Mid-Atlantic” ecosystems discusses above, could be briefly put off due to several factors such as length of growing, soil type, and level of establishment. Invasives species have what we call and “invasion front”, which is exactly what it sound like; this is the area at which the species is only just beginning its establishment. Regions at this invasion front are less susceptible to full establishment and are therefore at least somewhat protected from full invasion like is what seen in the south.

While direct impacts maybe withheld for some time in these frontier regions, impacts of kudzu once fully established, goes far beyond just killing the things it engulfs. A 2010 study by Hickman et al. showed that the presence of kudzu drastically increases local nitric oxide emissions and consequently increases ozone levels in these areas. Without getting too far in the weeds, kudzu impacts the nitrogen cycle of an area by having incredibly high rates of use of nitrogen (up to 500% higher than areas without kudzu!). This increased impact on nitrogen in the soil means that emissions of nitric oxide from the soil of invaded areas increases by 100%. To put it in perspective, the authors of this paper, with their findings, suggest that this input of nitrogen gas and consequent increased ozone should be included when thinking about overall climate models. That is how big of an impact this one plant species can have.

The Good: How does all this impact management into the future?

So, I know the catch phrase in the title of this post is backwards from the classic western film title. I did that because I like to end on a positive, or at least as much of a positive as I can with this topic. With everything that I talked about above, how in the world are we going to manage something that seems to be the run-away train of plants.

Well, first let’s start with kudzu. There was a recent study that showed that kudzu in and around New York City didn’t fair so well over time. This study looked at 20 years of data and saw that on 32% of kudzu population persisted around this area (Hoffberg & Mauricio, 2016). This suggests that this plant may not be unstoppable after all. The northern states of invasion concern that I talked about before, may not be facing as dire a situation as the south as seen over the decades. It seems that kudzu may be reaching its northern most limits, and these limits are not as heavily impacted as may have been feared. With this being said, maybe it is possible to more easily manage the northern populations and curb the environmental impacts of kudzu for these areas.

As for honeysuckle, certain management techniques have been proven successful at curbing the spread of this species. The most effective way to reduce invasion is to convert land into public land ownership (Wang et al., 2012). However, this is not a feasible option, so this study suggest that replanting of native species and repeated fire disturbance are techniques that reduce the impact and invasiveness of honeysuckle.

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This post hit on some very heavy issues that are on the mind of scientists and civilians around the globe. While this blog focuses on a relatively narrow niche of topics (literally only two invasive plant species here in the US), the topics covered here can be generalized and applied to places all over the world in different ways.

So I urge any readers of this blog to not just focus on these two plants and how they impact your life, but to take the issues discussed here and think about how it may impact areas and peoples you are not connected to. Zooming into the small-scale that I did during this blog is useful to get your mind around certain issues that seem overwhelming otherwise. But keeping in mind a larger-scale perspective allows us to just begin to understand the importance of these issues in terms of our whole natural world.

Citations:

Alderman, D. H. (1998). The changing south: A vine for postmodern times: An update on kudzu at the close of the twentieth century. Southeastern Geographer, 38(2), 167-179.

Bradley, B. A., Wilcove, D. S., & Oppenheimer, M. (2010). Climate change increases risk of plant invasion in the Eastern United States. Biological Invasions, 12(6), 1855-1872.

Hellmann, J. J., Byers, J. E., Bierwagen, B. G., & Dukes, J. S. (2008). Five potential consequences of climate change for invasive species. Conservation biology, 22(3), 534-543.

Hickman, J. E., Wu, S., Mickley, L. J., & Lerdau, M. T. (2010). Kudzu (Pueraria montana) invasion doubles emissions of nitric oxide and increases ozone pollution. Proceedings of the National Academy of Sciences, 107(22), 10115-10119.

Hickman, J. E., & Lerdau, M. T. (2013). Biogeochemical impacts of the northward expansion of kudzu under climate change: the importance of ecological context. Ecosphere, 4(10), 1-15.

Hoffberg, S. L., & Mauricio, R. (2016). The persistence of invasive populations of kudzu near the northern periphery of its range in New York City determined from historical data1, 2. The Journal of the Torrey Botanical Society, 143(4), 437-442.

Lemke, D., Hulme, P. E., Brown, J. A., & Tadesse, W. (2011). Distribution modelling of Japanese honeysuckle (Lonicera japonica) invasion in the Cumberland Plateau and Mountain Region, USA. Forest Ecology and Management, 262(2), 139-149

Wang, H. H., Wonkka, C. L., Grant, W. E., & Rogers, W. E. (2012). Potential range expansion of Japanese honeysuckle (Lonicera japonica Thunb.) in southern US forestlands. Forests, 3(3), 573-590.

Kudzu vs. Honeysuckle: Helping the "little guy" win

Competition, it’s something that many of us have experienced in one way or another in our lives. Whether it was for a little league tournament, video games, or a family game night, competition is something that everyone has experienced in one way or another in their lives. But competition is not a solely human experience. This phenomenon is something we see everywhere in the natural world. Lions fighting hyenas for food, gorillas competing for territory, or plants battling it out for water and light. These are just a tiny few in a seemingly endless list of competitive interactions we see in nature.

However, by this point, I think it’s clear that I will not be discussing lions or gorillas in this blog, but rather the intricate world of competition amongst plants. One characteristic of invasive species of any flora or fauna is its competitive advantage over native inhabitants. So, in this blog I will dive into the competitive advantages of the widely spread invasives, kudzu and honeysuckle, as well as the consequences of this competition on the ecosystem as a whole.

Competitive advantages

Both honeysuckle and kudzu are known to be highly successful invasives in the US, as is evident from their widespread range. This invasiveness can be caused by numerous factors, however one of the key differences between native species and invasives is the ability to out-compete the other. Honeysuckle, for instance, has been shown to bud earlier, hold onto its leaves longer in the fall, and hold-up better during freeze-snaps in springtime than its potential native competitors (McEwan et al, 2009). The three factors basically mean that honeysuckle has a longer period of time with leaves present than its neighbors and therefore can out-compete them to higher amounts of sunlight.

Similarly to honeysuckle, the battle for light is won by kudzu over native plants. Kudzu, we all know, is a vine that can cover pretty much anything in its path, once it gets a foothold (as is seen in Figure 1). With this ability to spread and cover entire landscapes, any native plant that would have previously grown there is no longer able to succeed. Additionally, kudzu has been shown to be able to withstand biomass removal (and even come back stronger afterwards), and kudzu seedlings can survive several weeks with no light (Frye et al, 2012).

Figure 1: Photo of kudzu entirely covering a house. (credit: Jonathon Van Buren)

Impacts of this competition on biodiversity

As you can imagine, this ability to over-grow anything below it, has dire consequences for the overall health and biodiversity of the effected ecosystem. For example, a 2008 study showed that a more mature (and therefore larger and more established) honeysuckle plant resulted in a significant decrease in the both density and species richness of herbaceous plants, seedlings and saplings growing under and around these invasive shrubs (Hartman & McCarthy, 2008). This pattern can be seen in Figure 2, however the bottom-most graph in that figure depicts a difference between honeysuckle and kudzu.

As was discussed earlier, kudzu grows over anything in its path, including full grown trees. We see that honeysuckle does not have this direct impact on overstory, or treetops in Figure 2. So, while kudzu indiscriminately takes over, on a surface level, honeysuckle does not impact the more mature trees.

Figure 2: From Hartman & McCarthy, 2008. Without diving into the details, we can see from this figure that the understory density (seen in the top three graphs) significantly decreased as the honeysuckle bushes matured and grew. This is because the amount of light reaching the understory and the overall accessibility of the understory is prevented by the thick clustering of honeysuckle branches above it. We also see that the overstory (tree tops) is not impacted by the honeysuckle, because this invasive is a shrub and does not reach heights to effect trees.

You may be asking, why does this biodiversity matter? Honeysuckle is a beautiful, sweet-smelling shrub and kudzu does create quite a lush, green blanket. Well, this biodiversity goes beyond the direct impact to native plants. There are other organisms that rely on natural, native ecosystems to survive. Once this balance is thrown off, animals that prefer native plants to survive on will be displaced. What once may have been an intricate collage of plants and animals, will become a monotonous landscape of invasives.

So, what now?

I know that these posts can seem a bit daunting and negative, but I always want to leave things off on a hopeful note! Because these plants have been studied for decades now, we have a pretty good understanding of how to try to control them. So not all hope is lost!

For honeysuckle, we know that they grow in both forested and open areas. However, they prefer higher light areas. This being said, avoiding the thinning of the forest canopy and forest fragmentation will lessen the likelihood of honeysuckle taking over that area (Luken et al, 1997). Clipping honeysuckle has been shown to have an impact on growth of the shrub. In forests, this technique may be all it takes to control honeysuckle. However, in more open areas, where honeysuckle prefers, clipping plus the use of herbicide have been shown to be a decent control (Luken & Mattimiro, 1991).

Kudzu is a bit trickier. It’s thought that the only plants that can truly compete with this vine are other invasives (such as Chinese privet and our beloved honeysuckle)(Blaustein, 2001). However, it has also been shown that planting certain grasses in the fall can help control kudzu once it is weakened (Everest et al, 1999). Biocontrol (aka bringing in things to eat the vine) has also proven to be a useful mechanism for controlling the spread of kudzu (Frye et al, 2013).

All of these control methods require persistence. Honeysuckle has been shown to come back with a vengeance if cut and then abandoned (Luken & Mattimiro, 1991). So, if clipping is the solution, it is suggested that this happens at least once a year, but more often if possible. Kudzu requires more than 2 or 3 years of biocontrol (Frye et al, 2012) but this is known to be a very effective method, if done correctly. All of these controls disrupt the competitive advantage these invasives have and give the native plants a fighting chance to survive.

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So, while competition is a natural part of the world, whether that be our family game night becoming heated, or a gorilla defending its territory, it can be a destructive force is left unchecked. The competitive advantage of invasive plants can be compared to an older and younger sibling wrestling, the little one doesn’t stand a chance. But we can at least try our best to give the little guy (in this case our native plants) any advantage we can.

References:

Blaustein, R. J. (2001). Kudzu’s invasion into Southern United States life and culture. The Great Reshuffling: Human dimensions of invasive species, 55-62.

Everest, J. W., Miller, J. H., Ball, D. M., & Patterson, M. (1999). Kudzu in Alabama history, uses, and control. Alabama A&M and Auburn Universities, Alabama Cooperative Extension System ANR-65.

Frye, M., Hough-Goldstein, J., & Kidd, K. (2012). Response of Kudzu (Pueraria montana var. lobata) Seedlings and Naturalized Plants to Simulated Herbivory. Invasive Plant Science and Management, 5(4), 417–426. https://doi.org/10.1614/IPSM-D-12-00001.1

Frye, M., & Hough-Goldstein, J. (2013). Plant Architecture and Growth Response of Kudzu (Fabales: Fabaceae) to Simulated Insect Herbivory. Environmental Entomology, 42(5), 936–941. https://doi.org/10.1603/EN12270

Hartman, K., & McCarthy, B. (2008). Changes in forest structure and species composition following invasion by a non-indigenous shrub, Amur honeysuckle (Lonicera maackii). The Journal of the Torrey Botanical Society, 135(2), 245–259. https://doi.org/10.3159/07-RA-036.1

Luken, J., & Mattimiro, D. (1991). Habitat-Specific Resilience of the Invasive Shrub Amur Honeysuckle (Lonicera Maackii) During Repeated Clipping. Ecological Applications, 1(1), 104–109. https://doi.org/10.2307/1941852

Luken, J., Kuddes, L., Tholemeier, T., & Haller, D. (1997). Comparative Responses of Lonicera maackii (Amur Honeysuckle) and Lindera benzoin (Spicebush) to Increased Light. The American Midland Naturalist, 138(2), 331-343. doi:10.2307/2426826

McEwan, R., Birchfield, M., Schoergendorfer, A., & Arthur, M. (2009). Leaf phenology and freeze tolerance of the invasive shrub Amur honeysuckle and potential native competitors. The Journal of the Torrey Botanical Society, 136(2), 212–220. https://doi.org/10.3159/08-RA-109.1

Kudzu vs. Honeysuckle: Changing Populations

Kudzu and honeysuckle are two of the most prevalent and well-known invasive plants in the US. We know some key things about how these plants impact the natural ecosystem and their overall range. However, these plants are changing their patterns and population dynamics, evolving to expand ranges, and impacting other species along the way. New studies and information allow for control and management techniques to improve. In this post I will discuss how kudzu and honeysuckle populations are changing and how these changes impact both the environment they invade and those in charge on trying to manage said invasions.

How they’re changing as a population

Kudzu is clearly a highly invasive plant. We see it across the southeast; along highways, in neighborhoods, etc. This invasiveness is due to many different characteristics. One of these is that there is little to no natural predator to this plant in the US. In a 2014 study in China, a team of researchers took kudzu specimens from the invaded Southeast US and specimens that were from the native populations of China. In this study they found that the invasive plants had much lower resistance to herbivory in China than the native Chinese plants (Yang et al., 2014). This supports the idea that the invasive species has evolved in its new range without the need to be resistant to any predators. We all only have so much energy in a day to do the things we need to do. Plants are no different; because invasive kudzu does not give energy to herbivory resistance, it can spend this energy in areas like growth and reproduction.

Figure 1: This figure was taken from Yang et al. 2014. It demonstrates that invasive kudzu in the US were less resistant to herbivory than the native plants in China. This shows that the invasive species have potentially evolved to lack this resistance due to the lack of natural predator in the US.

Figure 2: This figure is pulled from Yang et al. 2014.  It demonstrates the higher overall biomass of the invasive kudzu from the US. In comparison to the native Chinese individuals, the invasive plants showed significantly higher biomass, both aboveground in the stems and leaves, and belowground in the roots.

In addition to this evolution to live without predators, kudzu is able to grow amongst and with those kudzu plants that are genetically unique (Kartzinel et al., 2015). This ability to intermix with genetically variable plants allows kudzu to remain genetically variable while continually growing as a population. According to Kartzinel et al. 2015, this information means that some of the most common management tools for kudzu (mowing, cutting, etc.) may inadvertently be increasing genotypic diversity.

As for our other species of interest, studies have found that invasive honeysuckle growing near the margin of its habitat (rather than at the core of its invaded area) show signs of higher fitness and survival (Figure 2 & 3) (Kilkenny & Galloway, 2015). In terms of invasiveness and population success, this is a key finding. If a plant can spread to the borders of its habitat and have even greater success than at the heart of the population, this will inherently allow for more expansion. For invasive species like kudzu and honeysuckle, this ability allows for further invasion and species success.

Figure 3: This figure is pulled from Kilkenny & Galloway, 2015. It demonstrates the improved fitness of honeysuckle individuals at the margins of the invaded area. This figure gets at the idea that invasive species could potentially benefit from spreading into new habitat, and even show higher survival rates at these outer barriers.

How these changes are affecting the ecosystem

With the spread of these invasive plants due to their continued evolution to better succeed in their environments, the impacts of these plants also become more widespread. For instance, kudzu has been shown to create less diverse communities in the areas it invades. It is an over-arching vine that shades and negatively impacts most other plants in its path. Similarly, both honeysuckle and kudzu have been shown to have negative impacts on trillium plants (a genus of plant native to much of eastern North America) (Heckel, 2004). Trillium species are a commonly studied plants because the genus has both wide-spread and rare species. This dichotomy allows researchers to compare closely related organisms with very different habitat expanses. Regardless of this variation, it has been shown that both of these invasive plants negatively impact any trillium population.

Not only do these plants impact other plants negatively, there are impacts to those animals that use resources from said invasives. For example, there was a fly species discovered that has genetically evolved from a hybridization of two species in response to a new ecosystem invaded by honeysuckle (Carroll, 2007). These flies fed on the honeysuckle to the point that they became genetically distinct from related flies and have now been deemed the Lonicera fly (after the scientific name of honeysuckle: Lonicera japonica).

On to a more charismatic fauna, white-tailed deer have been shown to be a seed disperser for honeysuckle (Guiden et al., 2015). Many of us have seen white-tailed deer munching on vegetation around our backyards or along a roadside. These deer do not discriminate as to what they eat, especially when that food source has such sweet, sugary nutrients like honeysuckle. Because of its attractiveness to deer populations, these deer eat the fruit of the honeysuckle bush and therefore ingest the seeds along with the fruit. On down the road, the seeds pass through and the deer become a disperser for this invasive honeysuckle plant. The form of dispersal is effective and yet another reason why honeysuckle is such a highly invasive species.

How we can manage these changes and impacts

So, we know how invasive these plants are. We know that they are able to change their population dynamics and evolve to better survive in new territories. Now what do we do with this knowledge and how can we implement better management? Researchers are always on the lookout for better tools for management. An example of this innovation is found in an article published that introduced a new model that simulates how invasive plants can be managed best by looking at particular species characteristics. The researcher’s example work was done with kudzu and demonstrated the ability of the model to assist with management and control methods (Aurambout & Endress, 2018). With knowing things about the species biology and dispersal along with local management practices, the model finds solutions at local and regional scales and these solutions “can be compared to identify those most effective given the level of available resources” (Aurambout & Endress, 2018). This is just one example of work being done to better understand and control these invasives.

As for ourselves, how should we think about these invasive plants in our lives? A 2011 article from the US Department of Agriculture nicely summarizes how human activities can increase invasive success (Li et al., 2011). Invasive species are known to take advantage of newly disturbed habitat. This can be related to new residential developments, infrastructure, and industries. Kudzu is a great example of this invasive tactic. Keeping this in mind, it is always a good thing to disturb the natural ecosystem as little as possible. While we may not be able to control the building of new roads or apartment complexes, we can at least keep in mind that invasive preference for these disturbed habitats is just another reason to avoid human disturbance.

References:

Aurambout, J., & Endress, A. (2018). A model to simulate the spread and management cost of kudzu (Pueraria montana var. lobata) at landscape scale. Ecological Informatics., 43, 146–156.

Carroll, S. (2007). Natives adapting to invasive species: ecology, genes, and the sustainability of conservation. Ecological Research, 22(6), 892–901. 

Guiden, P., Gorchov, D., Nielsen, C., & Schauber, E. (2015). Seed dispersal of an invasive shrub, Amur honeysuckle (Lonicera maackii), by white-tailed deer in a fragmented agricultural-forest matrix. Plant Ecology, 216(7), 939–950.

Heckel, C.D., "Impacts of Exotic Invasive Vines on the Ecology and Reproduction of the Endangered Trillium Reliquum" (2004). Georgia Southern University: Electronic Theses and Dissertations. 692.

Kartzinel, T.R., Hamrick , J.L., et al. (2015). Heterogeneity of clonal patterns among patches of kudzu, Pueraria montana var. lobata, an invasive plant. Annals of Botany 116(5), 739–750.

Kilkenny, F., & Galloway, L. (2016). Evolution of marginal populations of an invasive vine increases the likelihood of future spread. The New Phytologist., 209(4), 1773–1780.

Li, Z., Dong, Q., Albright, T., & Guo, Q. (2011). Natural and human dimensions of a quasi-wild species: the case of kudzu. Biological Invasions 13(10), 2167–2179.

Yang, X., Huang, W., Tian, B. et al. (2014) Differences in growth and herbivory damage of native and invasive kudzu (Peuraria montana var. lobata) populations grown in the native range. Plant Ecology, 215, 339–346.

Kudzu vs. Honeysuckle: Functional differences and their impacts

Many of us can remember those hot summer days and the sweet scent of the honeysuckle in the backyard. Similarly, we can remember driving along the highway and seeing the haunting figures of dead trees covered in thick vines of kudzu. While these are a shared experience of many people, details of these invasive impacts are unknown to most.

Most people can name at least a few invasive plants. Some of the most common to come to people’s minds are kudzu or honeysuckle. We are used to seeing these plants here and there everyday places. However, they are likely more common than we may believe.  Once a population of an invasive species is established it can spread from there to new habitats that are suitable for its survival. The ecological response to invasive species introduction varies. In this post I will cover the differences and similarities between kudzu and honeysuckle in terms of the functional differences of the two invasives.

Kudzu & Honeysuckle as model invasives

Invasive plants can be introduced for many different reasons, or sometimes for no reason at all. One example of an intentional introduction is how honeysuckle was introduced for the purpose of horticulture (Schierenbeck 2004) due to their appealing flowers (Figure 3) and heartiness in less than ideal environments. Since introduction, honeysuckle has spread to cover almost all of the eastern US as well as isolated parts of the western US (Figure 1). Unlike honeysuckle which grows as a shrub, kudzu is a vine and grows at an alarming rate per year (14-18 meters!) (Forseth 1987) (Figure 4). This invasive vine can grow happily in either shaded or sunny areas, although high levels of sunlight are preferred. Kudzu is able to grow up along the trunks of establish trees, and break through the canopy layer of the trees. Once through this barrier (and with more sunlight available) they quickly take up and suffocate everything under and around them (Forseth 1987). In 2004, it was estimated that kudzu completely covered approximately three million hectares in the Southeastern US alone (Forseth 2004). That’s 12,000 square miles, which is the size of the state of Maryland! See Figure 2 for distribution map of where kudzu if found in the US. This plant has continued to spread since 2004 and with the impacts of climate change affecting the range of both plants and animals alike, we can expect to see a northward expansion of this invasive vine.

Figure 1: Map of where Japanese Honeysuckle is found (EDDMaps.org)

Figure 2: Map of where kudzu is found (EDDMaps.org)

Figure 3: image of honeysuckle blooming (AnnekeDeBlok/iStock/GettyImages)

Figure 4: image of kudzu near Atlanta, GA (Wikipedia)

Now, one may ask, why should we worry about invasic vines? It’s just a vine, what’s the big deal? In the same Foresth (2004) study, it was estimated that kudzu alone has caused somewhere between $100 and $500 million dollars in lost productivity of forests in the US. Therefore, understanding how invasive vines function may provide insight into how to manage, and mitigate their effects. If we know what type of habitat they prefer, maybe we can take preventative measures to halt its spread.

Do invasives function differently than native plants?

Many factors impact plant fitness, including nutrient and water availability and water use efficiency, and the plant’s morphology. Understanding these factors for invasive vines is critical for their management. The relationship between the invasive plants’ uses and the native plants’ uses of resources varies depending on resource availability. Some examples of this shift in resource allocation are a difference in the effect of limiting factors (Heberling et al. 2013; Matzek 2011), and the difference in above/below ground biomass and growth (van Kleunen et al. 2011).

Greater plasticity in invasives is another functional attribute that contribute to their success. Plasticity is defined as an individual or populations ability to shift its function in order to better survive and thrive. For instance, invasive honeysuckle has been shown to more readily make use of climbing supports and therefore increase its fitness over native plants in the same situation (Schweitzer & Larson 1999).

Additionally, invasive honeysuckle is proven to be a successful competitor in terms of its ability to take over both above ground (shading out the understory and decreasing the success of other saplings) and below ground (taking up nutrients and water and therefore decreasing the success of surrounding plants) (Schierenbeck 2004). These techniques of out-competing other species for necessary resources has resulted in a decrease in native plant fitness and consequently overall plant biodiversity in the invaded areas (Hartman & McCarthy, 2008).

As I briefly addressed earlier, climate change is expected to force plants to higher latitudes which were previously inaccessible to them. These opportunistic species are known to have a wide tolerance for unsuitable habitats, so if given the chance invasive plants will continue to utilize this shift in temperature regimes and expand their ranges. Additionally, these invasive plants are able to take necessary resources away from the native plants of a region. Because of this, these previously mentioned threats to the biodiversity of forests and overall health of an ecosystem will spread into newly invaded areas.

Conclusions & Take-aways

Some invasive species can be thought of in a positive light, like honeysuckle and its beauty. Some others are commonly known as pest species, like kuzdu. We know these species have thoroughly invaded many regions of the US, and in the face of continued spreading, its easy to give up hope in truly controlling these plants. However, there can be hope for a shift in tide of this continued invasion. Knowledge and education of the risks and impacts of these plants are some of the key factors to slow this spread. The general public must know of the threats and only then can we help combat the spread of these species. For instance, rather an allowing honeysuckle to spread (or god forbid planting it purposefully) because of the aesthetically pleasing, sweet tasting flowers, we can do our part to inhibit its growth and spread. With kudzu, although it is more commonly known as a pest-plant, one can try to not allow it to take hold in their area, and therefore hopefully stem the spread. With these steps, along with general awareness of the issues at hand, we may be able to avoid the spread of invasive species like honeysuckle and kudzu.

Citations:

Forseth, I.N., Teramura, A.H. “Field photosynthesis, microclimate and water relations of an exotic termperate liana, Pueraria lobata, kudzu” Oecologia, 71, 262-267. (1987)

Forseth, I.N., Innish, A.F. “Kudzu (Pueraria montana): history, physiology, and ecology combine to make a major ecosystem threat.” Critical Reviews in Plant Sciences, 23(5), 401-413. (2004)

Hartman, K.M., McCarthy, B.C. “Changes in forest structure and species composition following invasion by a non-indigenous shrub, Amur honeysuckle (Lonicera maackii)” Journal of the Torrey Botanical Society, 135(2), 245-259. (2008)

Heberling, J.M., and Fridley, J.D. “Resource-Use Strategies of Native and Invasive Plants in Eastern North American Forests.” The new phytologist. 200(2), 523–533. (2013)

Matzek, V. “Superior performance and nutrient-use efficiency of invasive plants over non-invasive congeners in a resource-limited environment.” Biological Invasions, 13, 3005-3014. (2011)

Schierenbeck, K.A. “Japanese Honeysuckle (Lonicera japonica) as an invasive species; history, ecology, and context.” Critical Reviews in Plant Sciences, 23(5), 391-400. (2004)

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