The following is a list of citations, links and abstracts of peer reviewed studies on woody invasive species of concern in the Great Lakes Region and their management, published between January 1 and March 31, 2021. You may be able to receive a personal-use copy of any copyrighted article by contacting the primary author. Subscribe to the Woody Invasive Research Digest to get an email when a new digest is posted!
- Open Access: No
- Keywords: Tree-of-heaven, Ailanthus altissima, ecology, species interactions, impacts
- Full Abstract: Ailanthus altissima, the invasive forest tree commonly known as the tree-of-heaven, has been associated with decreased levels of plant species richness and native species diversity. However, this relationship with resident plants has been inconsistently found and the tree’s influence on the seedbank has yet to be studied. To further understand the long-term impact of this tree, ten paired invaded-uninvaded sites were identified in Virginia, USA in a variety of different-aged stands. The herbaceous and woody understories for each plot were inventoried and soil samples were collected and grown out for 34 weeks in a greenhouse. All plants were identified to the most detailed taxonomic level possible. In total, 35 woody understory species, 62 herbaceous understory taxa, and 77 seedbank taxa were identified. The relationship between A. altissima presence and i) the proportion of individual plants that are native, ii) the proportion of species that are native, iii) the native diversity, and iv) the nonnative diversity were analyzed. In addition, models including the invasion age were also considered. We show that A. altissima invasions were associated with a decrease in the proportion of native plants and species in the understory, but not in the seedbank. Nonnative woody diversity also increased with A. altissima presence. Additionally, the impact on the nativity of the woody understory became more extreme over time. We end by discussing the benefits of both managing A. altissima invasions early to limit its overall impact and including the management of other nonnative plants in A. altissima restoration plans.
Citation & Link: Eisenhaure, S.E., McCarthy, H.C., O’del, J.N., Giguere, H., Symonds, C.J., Lee, T.D. 2021. Effects of turf, leaf litter, and soil compaction on emergence and establishment of invasive glossy buckthorn (Frangula alnus). Forest Ecology and Management, 484.
- Open Access: No
- Keywords: Glossy buckthorn, Frangula alnus, germination, establishment, species interactions.
- Full Abstract: Perennial invasive plants can be controlled by damaging established vegetative individuals or by preventing establishment of new plants from seed. Less information is available about the latter. We examined how seedling establishment of glossy buckthorn (Frangula alnus), a non-native shrub that invades forests in eastern North America, is affected by four soil surface treatments – grass-dominated turf, oak leaf litter, pine leaf litter, soil compaction – relative to an untreated control (tilled soil). Data on seedling emergence, survival, growth, and reproduction were collected from 1.5 m2 plots (six per treatment) over two years at the Kingman Research Farm, Madbury, NH, USA. Overall, buckthorn success from seed was inhibited by grass turf and facilitated by oak litter, while pine litter effects were complex and soil compaction had no effect. Specifically, relative to control, the turf treatment reduced buckthorn seedling emergence (year 2 only), increased mortality over two years, reduced density of living buckthorn, and prevented fruiting. Oak litter resulted in greater buckthorn seedling height relative to control, while pine litter, although reducing seedling emergence (year 1 only), increased both seedling height and the proportion of plants fruiting in year 2. Across all treatments and control, buckthorn seedling emergence was greatest in June, declining thereafter. Of the four treatments, only grass turf offered some promise of resisting invasion. The mechanism of resistance by turf is not known, but likely involves either more intense competition or higher levels of herbivory associated with turf. The mechanism, as well as the logistics and cost of turf establishment in logged areas, require further exploration.
Citation & Link: Erdélyi, A., Hartdégen, J., Malatinszky,A., Vadász, C. 2021. Silvicultural practices as main drivers of the spread of tree of heaven (Ailanthus altissima (Mill.) Swingle. Proceedings of the First International Electronic Conference on Biological Diversity, Ecology and Evolution, Session: Invasive Species and Diversity.
- Open Access: Yes
- Keywords: Tree-of-heaven, Ailanthus altissima, control, management, spread, cultural control, forestry, international
- Full Abstract: The impacts of anthropogenic disturbances on the spread of invasive species is one of the central issues of invasion biology. In our study, we aimed to investigate the relationship between certain silvicultural activities and the spread of Tree of Heaven (Ailanthus altissima) in calcareous sand forests (Peszéri-erdő, Central Hungary). We applied full-cover mapping (25 × 25 m grid) and BACI design to monitor the effects of clear-cuttings and selective thinnings on the prevalence and abundance of A. altissima in several stands (in total 26 ha). We also investigated young and middle-aged artificial reforestations (4 to 26 yrs.), where stump deposits were made (in total 30 ha). Our results indicate that silvicultural practices may significantly contribute to the spread of A. altissima. One or two years after the accomplishment of selective thinning or clear-cutting, the increase in both the small-scale prevalence and the total abundance of A. altissima was significantly higher compared to control stands. Stump deposits proved to be deterministic in the spread of A. altissima. A decrease in the abundance of A. altissima was observable only in one forest stand where verticillium wilt infection was detected, indicating a biological opportunity to control the spread of A. altissima.
- Open Access: No
- Keywords: Black locust, Robinia pseudoacacia, tree-of-heaven, Ailanthus altissima, management, control, effectiveness, physical control, girdling, international
- Full Abstract: Robinia pseudoacacia L. has been widely planted worldwide for a variety of purposes, but it is an aggressive invader in many regions. To control invasion by the species, we examined the effectiveness of girdling young trees to ground level to kill trees and preclude sprout development through comparison among girdling, clearcut and control treatments on the Tama river terrace, Tokyo. More than 99% of R. pseudoacacia trees were killed by girdling. The number of sprouts that developed from roots and stumps after girdling was distinctly reduced compared with that observed after clearcutting. We also conducted girdling of young trees of Ailanthus altissima (Mill.) Swingle, which shows similar developmental and ecological characteristics to R. pseudoacacia, and the two species are often sympatric. More than 98% of A. altissima trees were killed, but a higher number of sprouts developed from A. altissima stumps compared with that from R. pseudoacacia stumps. These results indicate that girdling young trees to ground level is an effective method of controlling R. pseudoacacia by killing the stem and precluding sprout development. The girdling method is simple to apply and imposes a low burden on the surrounding environment.
Citation & Link: Lalk, S., Hartshorn, J. & Coyle, D.R. 2021. Invasive woody plants and their effects on arthropods in the United States: Challenges and opportunities. Annals of the Entomological Society of America, 114(2): 192-205.
- Open Access: Yes
- Keywords: Tree-of-heaven, Ailanthus altissima, Norway maple, Acer platanoides, common buckthorn, Rhamnus cathartica, Russian olive, Elaeagnus angustifolia, autumn olive, Elaeagnus umbellata, Callery pear, Pyrus calleryana, ecology, impacts, pollinators, species interactions, research needs, literature review
- Full Abstract: Invasive plant introductions are increasing globally, and trends in human activity suggest these increases will continue. Although we know much about interactions between invasive herbaceous plants and arthropod communities, there is a dearth of knowledge examining interactions between invasive woody plants and arthropod communities. What information does exist shows that invasive woody plant relationships with mutualists (e.g., pollinators), herbivores, twig- and stem-borers, leaf-litter and soil-dwelling arthropods, and other arthropod groups are complex and hint at multiple factors influencing effects. These relationships warrant additional attention to allow better prioritization of species for research and regulatory review. Chinese tallow tree, e.g., is renowned for its attractiveness to honeybees, whereas reduced pollinator populations are found among other invasive woody plants such as privet. The unknown driving mechanisms and interactions that create these differences represent a substantial gap in knowledge and warrant additional research. Our objectives are to review current knowledge regarding invasive woody plants and their interactions with various arthropod groups in the United States, outline future research needs, and present a call to action regarding invasive woody plant research.
- Open Access: No
- Keywords: Asian bittersweet, Celastrus orbiculatus, history, introduction, species biology, ecology, management, literature review, international
- Full Abstract: Celastrus orbiculatus Thunb. is an invasive alien liana native to northern regions of Japan, Korea, China and Russia. Since its intentional North American introduction in the 1870s, it is now found across eastern Canada and United States. Through an extensive adventitious root system and twining growth habit, C. orbiculatus smothers and girdles surrounding vegetation, drastically altering the environment and ecosystem processes. C. orbiculatus continues to be distributed as an ornamental. In addition, birds and small mammals consume its prolific fruit and facilitate novel introductions. C. orbiculatus is susceptible to glyphosate and triclopyr. Once established, however, management intensity is compounded by its extensive root system and continual resprouting and root-suckering. The climatic requirements across eastern Canada, ease of dispersal and rapid growth suggest that C. orbiculatus will continue to spread across its introduced range.
Citation & Link: Postma, M. 2020. Assessing the introduction and age of the Acer platanoides (Norway maple) invasion within Wilket Creek ravine in Toronto, Ontario. Master’s Capstone in Restoration Forestry, Daniels Faculty of Architecture, Landscape and Design, University of Toronto. 34pp.
- Open Access: Yes
- Keywords: Norway maple, Acer platanoides, introduction, history, case study, student research, Great Lakes Basin
- Full Abstract: After over a century of disturbance the property that encompasses the Toronto Botanical Garden and the Wilket Creek ravine in Toronto, Ontario has fallen victim to the invasive Norway maple (Acer platanoides). The objectives of this study were to improve the overall knowledge of Norway maple invasions within the Wilket Creek ravine, to determine when and where Norway maples were introduced in the study area, and to improve the overall understanding of Norway maple age dynamics within the property. The results show that Norway maple was introduced into the Wilket Creek ravine in the 1940s and 50% of the sampled Norway maple within the study were established between 1980s and 2000s (18 and 40 years old). The results also show that Norway maple regeneration is present in almost all wooded areas. To control Norway maple, it is recommended to implement an intensive management plan that includes mechanical and chemical control methods, strict invasive species policy, and the development of public education and outreach programs to halt the regeneration and growth of the invasive tree species.
Citation & Link: Rathfon, R.A., Greenler, S.M., Jenkins, M.J. 2021. Effects of prescribed grazing by goats on non-native invasive shrubs and native plant species in a mixed-hardwood forest. Restoration Ecology, e13361.
- Open Access: No
- Keywords: Multiflora rose, Rosa multiflora, management, control, effectiveness, selectivity, physical control, grazing, goats
- Full Abstract: Invasion of non‐native shrubs comprises a serious economic and ecological problem in North American forests. Prescribed grazing by goats may offer an effective alternative to traditional methods of control, but has received little study in forest settings. In a 5‐year field experiment, we varied the stocking of goats and number of grazing periods to determine effects of prescribed grazing on both invasive shrubs and native plant species. Specifically, we examined how varied stocking levels and grazing periods affect: (1) the cover and height of invasive shrub and native woody species (2) the cover and diversity of herbaceous species, and (3) the density of native tree seedlings. Data were analyzed with linear mixed‐effects models. We found that prescribed grazing by goats significantly reduced the cover and height of invasive shrubs, regardless of goat stocking or duration. Generally, the greatest reductions in invasive shrub cover occurred in treatments with two grazing periods, regardless of goat stocking. While we observed mostly neutral or positive effects on the herbaceous layer, all grazing treatments reduced the cover and height of native understory woody species. While changes were not significant, we observed a general decline in the aggregate height of native tree species regeneration. Our results suggest that prescribed grazing by goats provides an effective and environmentally friendly treatment for heavy invasions of non‐native shrubs such as Rosa multiflora, but grazing needs to be followed by focused mechanical or chemical treatments to maintain control while allowing the regeneration of native tree species.
Citation & Link: Woods, M.J., Attea, G.K., McEwan, R.W. 2021. Resprouting of the woody plant Pyrus calleryana influences soil ecology during invasion of grasslands in the American Midwest. Applied Soil Ecology, 166.
- Open Access: No
- Keywords: Callery pear, Pyrus calleryana, ecology, impacts, management, physical control, mowing
- Full Abstract: Biological invasion of woody plants into grasslands is a widespread phenomenon that threatens the cultural value, biodiversity, and ecosystem function of these unique systems. In the American Midwest, grasslands are increasingly threatened by invasion of the tree Pyrus calleryana (Callery pear) which is particularly challenging to manage and has strong potential to alter ecosystem function. Mowing is a standard practice for maintaining Midwestern grasslands; however, P. calleryana exhibits an aggressive sprout response to cutting and the ecological implications of this behavior are not well understood. We measured the response of soil moisture and pH, and soil enzyme activities representing labile carbon cycling (β-glucosidase), recalcitrant carbon cycling (peroxidase and phenol oxidase), nitrogen cycling (leucine aminopeptidase) and phosphorus cycling (phosphatase) to determine how P. calleryana trees that are untreated and single stemmed alter nutrient cycling compared to their cut and resprouting counterparts. We found lower β-glucosidase activity and higher peroxidase activity underneath single stemmed trees than underneath those which had resprouted, indicating that there may be lower nutrient availability underneath untreated trees accounting for differences in enzyme activity. Generally, invasive species leaf litter has faster decay rates than native species, which results in higher activities of enzymes that degrade labile materials in soil underneath the plants. Because soils underneath P. calleryana do not follow this pattern, it is possible that its leaf material is not as labile as other common invaders. We also found that increasing P. calleryana basal diameter was associated with reductions in soil pH, which indirectly increased peroxidase and phenol oxidase activities, enzymes which are indicative of recalcitrant C sources such as lignin. This demonstrates that P. calleryana may alter carbon cycling by altering the C inputs to the soil system from its leaf litter. Taken together, P. calleryana may reduce plant richness and promote further invasion by lowering the availability of labile carbon and lowering soil pH, indicating that this invasion may be soil-mediated and self-reinforcing. Further, we recommend continued mowing as a treatment for P. calleryana invasion to ameliorate the impacts of its invasion even though there will likely be a sprout response to treatment.
Citation & Link: Zaya, D.N., Leicht-Young, S.A., Pavlovic, N.B., Ashley, M.V. 2021. Heterospecific pollination by an invasive congener threatens the native American bittersweet, Celastrus scandens, PLOS One.
- Open Access: Yes
- Keywords: Asian bittersweet, Celastrus orbiculatus, species interactions, impacts, Great Lakes Basin
- Full Abstract:Invasive plants have the potential to interfere with native species’ reproductive success through a number of mechanisms, including heterospecific pollination and hybridization. This study investigated reproductive interactions between a native North American woody vine (American bittersweet, Celastrus scandens) and an introduced congener (oriental bittersweet, C. orbiculatus). The decline of C. scandens in the eastern portion of its range is coincident with the introduction and spread of C. orbiculatus, and the two species are known to hybridize. The relationship between proximity and floral production of conspecific and heterospecific males on fertilization and hybridization rates was measured at a field site in northwestern Indiana, USA where both species occur and reproduce. We found that the invasive vine had an extreme advantage in both male and female floral production, producing nearly 200 times more flowers per staminate plant and 65 times more flowers per pistillate plant than the native. Using nuclear microsatellite DNA markers we found that hybridization rates were asymmetric; 39% of the C. scandens seeds tested were hybrids, compared to only 1.6% of C. orbiculatus seeds. The asymmetric hybridization rates were likely not solely due to greater abundance of C. orbiculatus pollen because experimental hand crosses revealed that C. scandens had a higher rate (41%) of heterospecific fertilization than C. orbiculatus (2.4%). We previously reported that few hybrids were observed in the wild, and hybrids had greatly reduced fecundity. Thus, in our system, the threat posed by heterospecific pollen is not replacement by hybrids or introgression, but rather asymmetric reproductive interference. Reproductive interference extended to distances as great as 100 meters, thus, efforts to conserve the native species must reduce its exposure to C. orbiculatus over a relatively large spatial scale.
- Open Access: Yes
- Keywords: Wineberry, Rubus phoenicolasius, plant biology, genetics, international
- Full Abstract: Rubus phoenicolasius Maxim. is a traditional Tibetan medicine and widely used in the clinical pharmacology. In current study, the complete chloroplast genome of R. phoenicolasius was reported. The total length of the genome was 155,144 bp with the GC content of 37.9%. We predicted 130 genes in the genome including 84 protein-coding genes, 37 tRNA genes, 8 rRNA genes and 1 pseudogene. 17 genes
were duplicated in the IR regions including 7 tRNA, 4 rRNA and 6 protein-coding genes. Phylogenomic analysis revealed that R. phoenicolasius forms a strong supported branch with R. amabilis and R. coreanus under the Rosaceae clade.
Citation & Link: Zhang, T., Sun, J., Xu, L., Yang, Y., Zhan, Z., Xing, Y., Zhao, R., Li, S., Zhang, D., & Kang, T. 2021. The complete mitochondrial genome of Euonymus alatus (celastraceae, Euonymus L.), Mitochondrial DNA Part B, 6(1): 182-184.
- Open Access: Yes
- Keywords: Winged burning-bush, Euonymus alatus, plant biology, genetics, international
- Full Abstract: The complete mitochondrial genome of medicinal plant, Euonymus alatus, was sequenced for the first time. The genome sequence is 1,045,106 bp in length (GenBank accession number MW009108), with 44.98% GC contents. There are 72 genes in the genome, including 41 known protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), and three ribosomal RNAs (rRNAs). The phylogenetic trees of 28 species are constructed using the maximum-likelihood method. The information will provide references for phylogenetic research.