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Amur honeysuckle (Lonicera maackii), a woody shrub native to northeastern Asia, is a common invasive species in many urban, suburban, and rural environments in North America. Honeysuckle negatively impacts native plant communities, and prolonged removal efforts are required to slow its spread and prevent reestablishment. However, intensive management is not always feasible for homeowners and small landowners, so the potential for small-scale honeysuckle removal followed by a passive approach is highly desirable. To test the potential for small-scale honeysuckle removal to initiate observable native plant recruitment, we established a long-term, small-scale study within a well-established honeysuckle infestation located in a 12.1 ha suburban patch of oak-hickory forest in Shawnee County, Kansas. We annually cleared 10 plots of all honeysuckle and maintained 10 adjacent, uncleared plots for the duration of the study. Native plant numbers increased within 1 y in the removal plots, and this increase continued across years. However, the vast majority of individuals consisted of aggressive and early successional species, and no significant differences in the effective number of common or dominant native species were observed between 2017 and 2020. Our results suggest that small-scale suppression of honeysuckle in well-established honeysuckle populations will likely lead to recolonization by a small number of species that may remain dominant for several years. Therefore, in areas with well-established honeysuckle populations, small-scale management of honeysuckle growth will likely be insufficient to ensure that even a moderate sample of native species becomes established. [ABSTRACT FROM AUTHOR]

Climate change significantly impacts species composition, competition, range, and variability. Invasive species, such as the Amur honeysuckle, Lonicera maackii (Ruprecht) Maximowicz (Caprifoliaceae), which is native in western Asia, are rapidly expanding, and altering forest ecosystems in the United States. I attempt to provide a framework for initially understanding the effects of climate change on L. maackii and its relationship with the native wildlife. To assess the influence of global climate change on invasive species, such as L. maackii, and to help direct future research and understanding of the complexity of ecosystems with invasive species like L.maackii, I suggest direction for future research to address important knowledge gaps on the ecological impacts of L. maackii. For instance, effects of L. maackii on native plants have been documented to a great extent but, little is known about the influence of L. maackii on native wildlife species, specifically leaf-litter invertebrates, and amphibians. Studies show that the Amur honeysuckle impacts native wildlife species with pressures such as increased bird nest predation due to it being low to the ground and bushy in appearance, leading to decreased nesting success and population sinks in some bird species. The Amur honeysuckle provides cover to small mammals against predators and alters the microclimate and chemical composition of nearby waters of amphibian habitats making them more susceptible to predators. Lonicera maackii has both a positive and negative relationship with pollinators on crop fields. Lonicera maackii's fruit also lacks nutritional substance and its effect on the ecosystem is widely unknown. I review how basic ecological principles can be used to predict the response of honeysuckle to climate change and its future impact on native wildlife. [ABSTRACT FROM AUTHOR]

The ecology of headwater streams is tightly linked to the riparian zone through organic matter subsidies which are highly susceptible to alteration due to biological invasion. Lonicera maackii is a non-native shrub that is a highly successful invader of headwater stream riparian zones in the American Midwest. We assessed effects on benthic macroinvertebrates across a gradient of invasion intensity from references sites with minimal invasion to a site that had a very heavy invasion. Benthic macroinvertebrates were sampled throughout the year and compositional differences were assessed using Non-metric Multidimensional Scaling ordination, and by comparing the prevalence of sensitive (Ephemeroptera, Plectoptera, and Trichoptera: EPT) and tolerant (Chironomidae) macroinvertebrate taxa. We found strong evidence of variation among macroinvertebrate communities across the invasion gradient (ANOSIM R = 0.215, P = 0.004) and particularly strong separation between one of our reference sites with minimal invasion and the site with the heaviest invasion. Analysis of EPT taxa indicated a significant overall effect and pairwise comparisons indicated that the site with the heaviest invasion had the lowest percentage of sensitive taxa (P < 0.05). Our analysis of chironomids did not yield a statistically discernable effect, although the pattern of the data suggest higher dominance in the site with the heaviest invasion. These stream-scale results bolster prior laboratory and field experiments and provide evidence that terrestrial invasion of L. maackii impacts the benthic community present in headwater streams. These results provide impetus to re-focus stream management recommendations to include practices that control invasive plants in riparian forests. [ABSTRACT FROM AUTHOR]

Exotic invasive plant species (EIPS) may succeed in part because they release allelochemicals that are novel to native plants (Novel Weapons Hypothesis). Plant allelopathic effects may increase under abiotic and biotic stresses based on The Stress Hypothesis of Allelopathy (TSHA). Lonicera maackii is an aggressive EIPS in the Midwestern USA, able to affect native flora by means of allelopathy. We aimed to test the role of intraspecific competition, as biotic stress, and expected future climate conditions (i.e. intense floods in spring; hotter and drier conditions in summer), as abiotic stress, on the performance and allelopathic potential of L. maackii. We grew L. maackii plants, collected from the field (field plants) or germinated from seeds in a greenhouse (seedlings), with or without intraspecific competition and under simulated present and expected future (1) spring (intense flooding vs no flooding) and (2) summer conditions. We subsequently measured plant performance variables, such as Fv/Fm (an indicator of plant stress), plant biomass, and concentration of pigments, carbon and nitrogen; and allelopathic potential (i.e. the effect of L. maackii leaf extracts and conditioned substrates on the germination of two herb species). In accordance with TSHA, intense flooding stressed L. maackii (Fv/Fm < 0.7), reduced its biomass, and increased its allelopathic potential. In summer, L. maackii plants were more stressed (lower average Fv/Fm) under future summer conditions and intraspecific competition than under present conditions without competitors, but they had similar allelopathic potential. This suggests the presence of a stress threshold from which allelopathic potential does not increase further. Intraspecific competition more negatively affected the performance of seedlings (e.g. plant mass reduction) than field plants, but only increased the allelopathic potential of the latter. Our results indicated that the negative effects of intense flooding on L. maackii performance could be counteracted by the benefit gained in plant–plant competition by means of increased allelopathic potential. The complex role of abiotic and biotic conditions on L. maackii performance and allelopathy are also discussed. [ABSTRACT FROM AUTHOR]

• Amur honeysuckle increases soil moisture. • White-tailed deer decrease soil pH and moisture. • Peroxidase and phenol oxidase activity is higher with lower pH. • White tailed deer increase peroxidase and phenol oxidase activities. Forest soils sustain productivity and ecosystem function through nutrient cycling and by acting as a carbon stock. By retaining carbon, these soils delay its release into the atmosphere as a greenhouse gas. Forest disturbances may alter the ability of soil to recycle nutrients and decrease its potential to act as a carbon stock. In the Midwestern US, many forests are experiencing two simultaneous disturbances likely to permanently alter the soil ecosystem: invasion by the exotic shrub Amur honeysuckle (Lonicera maackii) and dense populations of white-tailed deer (Odocoileus virginianus). To capture how these disturbances are impacting nutrient cycling, we measured potential soil enzyme activity and soil physicochemical properties in a fully factorial deer and honeysuckle removal experiment, where initial removal occurred three years prior to soil sampling. We measured β-glucosidase, phenol oxidase and peroxidase activities, which are associated with carbon cycling, and phosphatase activity which is associated with phosphorus cycling. We also measured soil pH, moisture, and texture to determine if honeysuckle and/or deer are changing the habitat of microorganisms, which may indirectly alter enzyme release. Using structural equation modeling, we then compared direct and indirect effects between combinations of honeysuckle and deer presence/absence, soil characteristics, and enzyme activities. Honeysuckle presence increased soil moisture and pH, but these relationships were weak. Additionally, deer presence directly increased phenol oxidase and peroxidase activities and altered the environment to be more conducive for phenol oxidase and peroxidase activities by decreasing pH. Neither deer nor honeysuckle presence altered β-glucosidase or phosphatase activity. Since we could detect changes in soil enzyme activity when deer were excluded independently of honeysuckle, it is likely that soil microorganisms can recover from overabundant deer within shorter time periods and thus the effect of deer may be reversible. In a Midwestern US forest invaded by both Amur honeysuckle and overabundant deer, removing or reducing deer presence could reduce C emissions, but more research is needed to further elucidate how honeysuckle alters nutrient cycling. [ABSTRACT FROM AUTHOR]

The invasive shrub, Lonicera maackii, is known to change forest ecosystem communities and functions; however, few have studied the potential for this prolific invader to return after forest restoration. We studied the forest understory, canopy, seed bank, and incoming L. maackii seed rain in a riparian urban forest five to nine years after L. maackii removal and restoration efforts. We found the restored areas maintained a native canopy, but by nine years post-management efforts, L. maackii was becoming more important along multiple transects due to many small individual seedlings. The restored areas had greater herbaceous cover and species richness when compared to the control area (L. maackii -dominated). Lonicera maackii was not common in the seed bank during the study but was more prevalent in the seed rain of the restored forest with a tree canopy than in the restored open field without a tree canopy. While our results support the premise that removing L. maackii returns the community to a more native state, the study also shows that the native state would not last without additional minor intervention. Monitoring beyond ten years post-removal will be key to telling the whole reinvasion story, but management efforts every five to ten years could suffice to keep a restored forest dominated by native species. [ABSTRACT FROM AUTHOR]

Riparian forests are a functionally important interface between terrestrial and aquatic communities, facilitating the transfer of subsidies that support aquatic biota and ecosystem processes. Invasion of the non-native shrub Amur honeysuckle (Lonicera maackii) in forests of the Midwestern United States has resulted in the formation of a dense monospecific shrub-layer along many headwater streams, substantially altering both the composition and structure of riparian plant communities. We investigated the effects of L. maackii on the chemistry of throughfall (rain that has passed through a plant canopy) in a riparian forest. During the growing season of 2015, throughfall collections were made in areas with no plant canopy (Open), a native forest canopy (Upper canopy), and within the forest but immediately under L. maackii shrubs (Honeysuckle). The Honeysuckle treatment intercepted 28-64% more throughfall compared to the Upper canopy treatment, resulting in lowered throughfall volume under the shrubs. The Honeysuckle treatment had substantially greater total carbon and total organic carbon concentration in throughfall compared to other throughfall treatments (P < 0.01). Total nitrogen and dissolved nitrogen deposition was up to 66% reduced under Honeysuckle treatments compared to a 45% reduction from Upper Canopy collections. In summary, these findings contribute to the growing scientific literature demonstrating that invasion by the exotic shrub L. maackii can capture incoming rainwater and alter the chemistry of throughfall, impacting cross-system nutrient subsidies and riparian function. [ABSTRACT FROM AUTHOR]

Summary: For many of the shrub species invading temperate deciduous forests, extended leaf phenology contributes substantially to annual carbon gains, helping to make possible rapid growth and spread. We carried out a pair of proof‐of‐concept studies to evaluate the susceptibility of such shrubs to foliar herbicide treatment during the period of delayed senescence, i.e. well after it is typically attempted. We first evaluated leaf‐level physiology in four species that lose leaves late in autumn; photosynthetic rates were comparable (80–111%) to those reported for the same species in summer. While preliminary, this finding provides a strong indication that diverse shrub taxa remain susceptible to control into late autumn. In addition, we conducted a field trial involving one of these species (Lonicera maackii) to directly evaluate the effectiveness of foliar treatment in November; applications included glyphosate and two concentrations of aminocyclopyrachlor plus metsulfuron methyl. Treatments killed (72%) or severely injured (14%) target plants, inducing greater cambial damage in plants that retained greater fractions of their canopy or had smaller canopy widths; there were no statistically significant differences among application types. This study demonstrated that late autumn can be a viable period in which to treat weedy species that delay senescence strongly, such as the many invasive Lonicera species in North America. Given that climate change and urbanisation are further delaying senescence in invasive plant populations, our study serves as a call for further investigation into what promises to be an increasingly viable opportunity for weed control in deciduous forests. [ABSTRACT FROM AUTHOR]

Lonicera maackii (Amur honeysuckle) is a non‐native species that has invaded forest stands throughout the eastern United States. This research examined using aerially applied glyphosate in autumn 2013 to control L. maackii in oak‐hickory forest stands in Missouri, U.S.A. We targeted the spraying time period when L. maackii was still green and most native plants were dormant. Across treatment units, the mean difference in L. maackii stem density significantly declined (p = 0.004) by 5.4 stems per plot from spring 2013 to summer 2014 when compared to control units which increased by 1.8 stems per plot. Treated units with a high initial infestation level of L. maackii (>50% cover) had a significant (p = 0.004) decline in the mean difference in L. maackii cover of −50.0% per plot between spring 2013 and summer 2014 compared to an average increase of 9.2% in the controls. Similar results were found for treated units with a low initial infestation level of L. maackii (10–50% cover). Mortality of native overstory and understory trees post‐treatment was negligible. In the ground layer of forest stands with a low initial L. maackii infestation level, native non‐spray‐sensitive forb cover per plot significantly increased (p = 0.023) relative to controls between summer 2013 and summer 2014 while native spray‐sensitive species cover significantly decreased (p = 0.021) during the same period. These results suggest that an aerial application of glyphosate can provide an L. maackii control option, but with trade‐offs in compositional shifts in the native ground‐layer vegetation. [ABSTRACT FROM AUTHOR]

Lonicera maackii is native to Northeastern Asia and considered as an invasive plant in North America. In this study, the complete chloroplast genome of L. maackii was obtained by high-throughput next-generation sequencing technology. The chloroplast genome was 155,318 bp in length and had typical quadripartite structures comprising a large single copy, a small single copy, and a pair of inverted repeat regions of 89,202, 18,680, and 23,718 bp long, respectively. The genome contained 80 protein-coding genes, four rRNA genes and 30 tRNA genes. Phylogenetic tree revealed that L. maackii was grouped with other Caprifoliaceae species, L. japonica, Patrinia saniculifolia, and Kolkwitzia amabilis.

Lonicera maackii (Amur honeysuckle) is known to dominate the shrub layer of forests, resulting in a dramatic decrease in ground cover, species diversity, and changes in ecosystem processes such as decomposition. Land managers have been removing L. maackii for some time now, but few studies have examined the potential for reinvasion of a restored site. We measured the plant community and ecosystem function in a restored forest and field (L. maackii removal and seeding of native plants) and in a control forest (L. maackii dominating), along an urban riparian stretch, five through seven years after L. maackii restoration. We found that removing L. maackii, along with modest efforts to re-introduce native grasses and forbs, can result in a shift in the plant community and some ecosystem properties and processes. Restored sites had higher species richness, greater available soil nitrogen, and faster nitrogen mineralization rates. We also found lower soil pH and that more soil organic matter accumulated over time in the restored treatments. While we found that removal of L. maackii and seeding of native plants can lead to a change in some ecosystem processes within ten years in riparian forests, we encourage scientists and managers to continue efforts on longer-term studies to better understand ecosystem structure and function after removal of the invader. [ABSTRACT FROM AUTHOR]

Selection of proper sampling methods for measuring a community of interest is essential whether the study goals are to conduct a species inventory, environmental monitoring, or a manipulative experiment. Insect diversity studies often employ multiple collection methods at the expense of researcher time and funding. Ants (Formicidae) are widely used in environmental monitoring owing to their sensitivity to ecosystem changes. When sampling ant communities, two passive techniques are recommended in combination: pitfall traps and Winkler litter extraction. These recommendations are often based on studies from highly diverse tropical regions or when a species inventory is the goal. Studies in temperate regions often focus on measuring consistent community response along gradients of disturbance or among management regimes; therefore, multiple sampling methods may be unnecessary. We compared the effectiveness of pitfalls and Winkler litter extraction in an eastern temperate forest for measuring ant species richness, composition, and occurrence of ant functional groups in response to experimental manipulations of two key forest ecosystem drivers, white-tailed deer and an invasive shrub (Amur honeysuckle). We found no significant effect of sampling method on the outcome of the ecological experiment; however, we found differences between the two sampling methods in the resulting ant species richness and functional group occurrence. Litter samples approximated the overall combined species richness and composition, but pitfalls were better at sampling large-bodied (Camponotus) species. We conclude that employing both methods is essential only for species inventories or monitoring ants in the Coldclimate Specialists functional group. [ABSTRACT FROM AUTHOR]

To evaluate the effects of Amur honeysuckle ( Lonicera maackii) removal on arthropod abundance and taxon richness, we sampled arthropods in seven removal plots and seven control plots in urban parkland in Louisville, Kentucky, in the first and third years after removal. We found no differences in overall abundance between invaded and removal plots in the first year after management, although removal plots had 12%-16% higher taxon diversity than invaded plots. Three years after management, invaded plots had 46% higher ground-dwelling arthropod abundance and 31% higher taxon richness, partly explained by other shrubs in managed plots. Herbivores were 91% more abundant in removal plots. Our results suggest that honeysuckle removal can have small effects on the entire arthropod community, but an increase in herbivore abundance should be expected following removal of this unpalatable invasive species. [ABSTRACT FROM AUTHOR]

The bush honeysuckles, including Lonicera maackii, have been promulgated as horticultural prizewinners, publicized as horticultural plunderers, and occupied every step in between. Fast-spreading, relatively agnostic in terms of growing conditions, and showy, its fixed position as a decorative plant has become the root of a larger challenge. This article is a brief look at the extensive literature surrounding this ambivalent shrub. [ABSTRACT FROM AUTHOR]

Riparian forests and streams are interlinked by cross-system subsidies and alterations of the terrestrial environment can have substantial effects on aquatic biota and ecosystem function. In the Midwestern USA, the exotic shrub Lonicera maackii (Amur honeysuckle) has successfully invaded many riparian habitats, creating near-monocultures in some locations. This terrestrial invasion has strong potential to modify cross-system subsidies and impact stream ecosystems. We removed L. maackii from a riparian forest to assess impacts on the aquatic environment. In August 2010, removal occurred along a 150 m stream reach, 10 m downstream of a non-removal reach, before natural leaf senescence. Over 74 days, in-stream leaf litter [organic matter (OM)] was collected weekly from plots located in riffles (five/reach). Benthic algal biomass, above stream canopy cover, and macroinvertebrate density were measured for 18 months. L. maackii removal was associated with decreased canopy cover and a significant increase in total in-stream leaf OM in early autumn ( P < 0.05). Removal also differentially influenced the timing and abundance of specific leaf litter genera within the stream ( P < 0.05). Macroinvertebrate density was significantly higher in the removal reach, especially during autumn 1 year after removal ( P = 0.0294). In both reaches, macroinvertebrate density peaks lagged behind benthic algal biomass peaks. In summary, the removal of an invasive riparian shrub influenced the timing, deposition, quality and abundance of leaf litter habitat into a headwater stream, ostensibly driving bottom-up effects on aquatic primary producer biomass and the macroinvertebrate community. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We studied the genetic structure of populations of the invasive shrub Amur honeysuckle ( Lonicera maackii) in 41 woodlots in an agricultural landscape in a recently invaded area in southwest Ohio. Using six polymorphic microsatellite loci, we found high allelic diversity and high heterozygosity in all populations and low to moderate levels of genetic differentiation among populations. We also found significant positive correlations between geographic distance and (1) Nei's genetic distance and (2) the coefficient of genetic differentiation (F/(1 − F) among all possible pairs of populations. These relationships were stronger when we tested the correlations of each of five putative source populations against the remaining non-source populations; and were especially strong when only the populations located within 30 km of each putative source were included in the analyses. Genetic analysis also revealed the existence of four distinct clusters that were not equally distributed across the study area, with high levels of admixture within populations. In particular, our findings indicate that the individuals present in six newly established populations in Darke county are made up of individuals belonging to multiple clusters, suggesting that these new populations were colonized from multiple nearby source populations. From these findings, we infer that the genetic structure of these L. maackii populations is determined by a combination of long-distance dispersal events and shorter distance diffusion from neighboring uninvaded woodlots, as well a history of multiple introductions into Ohio, and a predominantly outcrossing mating system. [ABSTRACT FROM AUTHOR]

While negative impacts of invasive species on native communities are well documented, less is known about how these communities respond to the removal of established populations of invasive species. With regard to invasive shrubs, studies examining native community response to removal at scales greater than experimental plots are lacking. We examined short-term effects of removing Lonicera maackii (Amur honeysuckle) and other non-native shrubs on native plant taxa in six mixed-hardwood forests. Each study site contained two 0.64 ha sample areas-an area where all non-native shrubs were removed and a reference area where no treatment was implemented. We sampled vegetation in the spring and summer before and after non-native shrubs were removed. Cover and diversity of native species, and densities of native woody seedlings, increased after shrub removal. However, we also observed significant increases in L. maackii seedling densities and Alliaria petiolata (garlic mustard) cover in removal areas. Changes in reference areas were less pronounced and mostly non-significant. Our results suggest that removing non-native shrubs allows short-term recovery of native communities across a range of invasion intensities. However, successful restoration will likely depend on renewed competition with invasive species that re-colonize treatment areas, the influence of herbivores, and subsequent control efforts. [ABSTRACT FROM AUTHOR]

Direct and indirect effects can play a key role in invasions, but experiments evaluating both are rare. We examined the roles of direct competition and apparent competition by exotic Amur honeysuckle (Lonicera maackii) by manipulating (1) L. maackii vegetation, (2) presence of L. maackii fruits, and (3) access to plants by small mammals and deer. Direct competition with L. maackii reduced the abundance and richness of native and exotic species, and native consumers significantly reduced the abundance and richness of native species. Although effects of direct competition and consumption were more pervasive, richness of native plants was also reduced through apparent competition, as small-mammal consumers reduced richness only when L. maackii fruits were present. Our experiment reveals the multiple, interactive pathways that affect the success and impact of an invasive exotic plant: exotic plants may directly benefit from reduced attack by native consumers, may directly exert strong competitive effects on native plants, and may also benefit from apparent competition. [ABSTRACT FROM AUTHOR]

Premise of research. It is known that outcrossing rates and mating structure are important factors determining the genetic structure of populations. Moreover, the composition and abundance of pollinator communities visiting flowers determine the distances over which the pollen is likely to be dispersed, which in turn affects the genetic structure of plant populations. For invasive plants, high outcrossing rates produce genetically diverse propagules for the colonization of uninvaded areas and facilitate the establishment of novel gene combinations that may affect their invasive ability. Here, we examine how differences in pollinator communities visiting flowers of the invasive shrub Lonicera maackii (Caprifoliaceae), growing along the edge and in the interior of a woodlot, affect their outcrossing rates and mating structure. Methodology. Five microsatellite marker loci were used to determine the outcrossing rates, levels of biparental inbreeding, and effective number of pollen donors siring the seed crop of plants growing along the edge and in the interior of an invaded woodlot. Pivotal results. We found that L. maackii is a predominantly outcrossing plant. Despite dissimilarities in composition and abundance of pollinator communities, there were no differences in outcrossing rates and biparental inbreeding between plants along the edge of the woodlot and those in the interior. However, the seed crop of plants in the interior was sired by more pollen donors than that of plants along the edge. Our findings suggest that plants differ in their ability to sire seeds, as maternal allele frequencies are different from those that sired their seeds. Conclusions. Lonicera maackii plants showed high outcrossing rates regardless of their position in the woodlot. Differences in the number of donors siring the seed crop between plants in the interior of the woodlot and those along the edge are most likely due to disparities in the abundance and composition of the pollinator communities. [ABSTRACT FROM AUTHOR]

Little is known about local patterns and rates of woody plant invasions, and even less is known about changes in spatial patterning and factors influencing structural characteristics of individuals as invasion phase progresses from establishment to saturation. We examined age distributions and spatial patterns of Amur honeysuckle (Lonicera maackii (Rupr.) Herder) invasions and identified factors influencing life-stage characteristics of individual shrubs in six mixed hardwood forests in Indiana. Predicted age distributions indicated that Amur honeysuckle reached the exponential phase of invasion at ~10-15 years. Inhomogeneous L and cross-L functions indicated that Amur honeysuckle exhibited a clustered spatial pattern. Immature individuals (no berries) clustered around mature individuals (with berries). However, spatial relationships between honeysuckle and trees rarely exhibited a clustered pattern. Regression analyses with Amur honeysuckle diameter and height as response variables revealed that incorporating spatial autocorrelation provided a better model fit and caused otherwise significant predictor variables to become nonsignificant (P ⩾ 0.05). Our results suggest that local-scale invasion by this species follows a predictable temporal sequence of population establishment and expansion via neighborhood diffusion and the forest-scale distribution of nascent foci. Furthermore, our results highlight the importance of considering spatial autocorrelation when evaluating life-stage characteristics of invasive populations. [ABSTRACT FROM AUTHOR]

Amur honeysuckle ( Lonicera maackii) is an exotic invasive shrub that is rapidly expanding into forests of eastern North America. This species forms a dense forest understory, alters tree regeneration, negatively affects herb-layer biodiversity, and alters ecosystem function. In a second-growth forest in central Kentucky, we examined the timing and production of leaf litter and compared litter chemistry, decay rates, and microbial community colonization of Amur honeysuckle to that of two native trees, white ash ( Fraxinus americana) and hickory ( Carya spp.). The distribution of Amur honeysuckle was clumped, allowing us to compare differences in decomposition under and away from Amur honeysuckle shrubs. Amur honeysuckle leaf litter had significantly higher nitrogen, lower C:N, and lower lignin than the other species, and decomposition rates were greater than 5× faster. Despite the much higher rate of Amur honeysuckle decomposition compared with the native species ( p < 0.0001), decomposition of all species was significantly slower ( p = 0.0489) in sites located under Amur honeysuckle shrubs. Nitrogen concentration increased through time in decomposing Amur honeysuckle litter; however, total mass of N rapidly declined. We found the initial microbial community on leaf litter of Amur honeysuckle was distinct from two native species and although all microbial communities changed through time, the microbial community of Amur honeysuckle remained distinct from native communities. In summary, a distinct microbial community that may originate on Amur honeysuckle leaves prior to senescence could explain the rapid decay rates. [ABSTRACT FROM AUTHOR]

The 'enemy release hypothesis' argues when a species is introduced to a novel habitat, release from regulation by herbivores results in increased vigor, abundance, and distribution. The invasive Asian shrub Lonicera maackii appears to benefit from an absence of arthropod herbivores in North America. We assessed the incidence, amount, and type of herbivory occurring on L. maackii in forest edge and interior habitats and investigated differences in timing of damage. In October 2008, leaves were sampled from shrubs in forest interior and edge habitat from 8 sites in Ohio. In 2009, sampling was repeated at 3 sites in spring, summer, and fall with a distinction made between long and short branches. Leaf area removed averaged 1.83% across the 8 populations in 2008 and 3.09% across the 3 populations in 2009, with forest edge plants receiving slightly more damage than forest interior plants in 2008. Additionally, long shoots received more damage than short shoots in 2009. Damage incidence was also higher in the edge habitat and on long shoots compared to short shoots. As measured in 2009, damage accumulated steadily throughout the season. Chewing was the most prevalent type of damage (76. 8%) and low level of pathogen infection was observed (4.81%). Results indicate that levels of herbivory experienced by L. maackii are relatively consistent across sites, vary slightly with habitat and branch identity, but are likely too low to impact fitness of shrubs. These findings indicate that low amounts of arthropod herbivory occur for L. maackii across its introduced range, which may contribute to its invasive success. [ABSTRACT FROM AUTHOR]

Exotic invasive shrubs can form dense monocultures in forest understories, which can have cascading effects on ecosystem structure and function. Amur honeysuckle, an exotic shrub that forms dense canopies in eastern forests, has the potential to alter plant community structure and ecosystem functions, such as primary production and decomposition. The goal of this study was to examine foliar productivity and leaf litter decomposition in forests invaded by Amur honeysuckle ( Lonicera maackii) and to determine the extent to which the presence of this dominant exotic species may alter ecosystem function in these forests. We found that forests invaded by Amur honeysuckle had 16 times greater honeysuckle foliar biomass and 1.5 times lower total foliar biomass than forests of equivalent tree basal area, but having few honeysuckle shrubs. This suggests that productivity of native tree and shrub species may be reduced where honeysuckle density is high. Additionally, honeysuckle litter decayed four times faster and released nitrogen more rapidly than sugar maple litter, and sugar maple litter decayed 19% faster in forests invaded by Amur honeysuckle. These findings suggest that forests invaded by Amur honeysuckle may exhibit lower rates of organic matter accrual and less nitrogen retention in the forest floor. Since honeysuckle leaves develop in early spring before those of other shrubs or trees in the area, the rapid release of nitrogen from honeysuckle litter that we measured in early spring is timed to benefit this invasive species. The temporally coincident phenologies of nitrogen release during decomposition with the foliar growth needs of this shrub indicates that a potential positive feedback loop may exist between these processes that promotes continued growth and dominance of honeysuckle shrubs in these forested systems. [ABSTRACT FROM AUTHOR]

Urban forests adjacent to interstate corridors are understudied ecosystems across cities. Despite their small area, these forests may be strategically located to provide large ecosystem services due to their ability to act as a barrier against air pollutants and noise as well as to provide flood control. The woody vegetation composition and structure of forests adjacent to urban interstates is an important determinant of their ability to provide these services. However, these forest communities may be particularly susceptible to the introduction of exotic invasive species via the interstate and the surrounding city that can potentially alter current and future forest composition. The purpose of this study was to investigate the distribution of native and exotic woody vegetation and tree regeneration in forests along three interstate corridors in Louisville, KY, and to determine potential factors (e.g., traffic density) that are correlated with patterns in the woody vegetation community. We found the most important determinants of vegetation composition along these interstate corridors were the distance from the city center and the presence of an exotic invasive shrub, Amur honeysuckle ( Lonicera maackii). Compared with forested plots within 10 km of the city center, plots further from the city center had 81% lower stem density of Amur honeysuckle, 96% higher tree seedling regeneration, and 51% greater woody plant species richness. The primarily native species composition of adult trees in forests alongside urban interstates in Louisville and the regeneration of native tree species provide optimism that these forests can maintain native species while experiencing multiple impacts from the interstate as well as from the surrounding city, emphasizing their important potential for maintaining natural forest functions across the urban landscape. [ABSTRACT FROM AUTHOR]

Lonicera maackii (Rupr.) Maxim. (Amur honeysuckle) is native to Asia and an important ornamental in China. However, the anatomy of leaf abscission (shedding) in L. maackii had not been studied previously. Such work is needed not only because knowledge of the leaf abscission process is important for a horticultural species like L. maackii but also because leaf abscission is probably the least understood abscission process, as it occurs so rapidly. Therefore, our objective was to use scanning electron microscopy (SEM) to examine the progression of leaf abscission in L. maackii at the cellular level . L. maackii branches with leaves were regularly collected in Beijing, China over the 2-month period in which leaves abscise, and examined with SEM. We found that, unlike in model species, the cortex is involved in abscission, forming an 'abaxial gap.' We discovered that there is no discrete abscission zone prior to the onset of abscission and that no cell divisions precede abscission. An abscission zone did become evident well after the abscission process had begun, but its cells were enlarged, not constricted as in typical abscission zones. In the abaxial gap, intact cells separated at their middle lamella, but in the abscission zone, cell separation involved the entire wall, which is not typical. We did observe expected mechanical fission of vascular tissues. While the leaf abscission process we observed in L. maackii has similarities with model systems, aspects deviate from the expected. [ABSTRACT FROM AUTHOR]

Lonicera maackii is native to Northeastern Asia and considered as an invasive plant in North America. In this study, the complete chloroplast genome of L. maackii was obtained by high-throughput next-generation sequencing technology. The chloroplast genome was 155,318 bp in length and had typical quadripartite structures comprising a large single copy, a small single copy, and a pair of inverted repeat regions of 89,202, 18,680, and 23,718 bp long, respectively. The genome contained 80 protein-coding genes, four rRNA genes and 30 tRNA genes. Phylogenetic tree revealed that L. maackii was grouped with other Caprifoliaceae species, L. japonica, Patrinia saniculifolia, and Kolkwitzia amabilis. [ABSTRACT FROM AUTHOR]

Invasion of Amur honeysuckle (Lonicera maackii) into riparian areas of headwater streams creates strong potential for alterations of terrestrial subsidies that may drive bottom-up effects on aquatic biota. In this study, we analyzed effects of L. maackii on terrestrial subsidies in stream sites that represented a gradient of invasion intensity in temperate deciduous forests of southwestern Ohio (USA). Leaf litter biomass, terrestrial and aquatic fine woody debris (0.5–9.9 cm diameter) volume and count, and terrestrial and aquatic coarse woody debris (>9.9 cm diameter) volume were analyzed. Based on previous research, we hypothesized that sites with a higher density of L. maackii would have decreased native species subsidies due to the dense overarching structure of the invasive shrub preventing materials from entering the stream. Over the course of the study, we found no evidence of differences in native leaf biomass across the invasion gradient. There were marginally significant effects of invasion level on fine woody debris, and regression analysis revealed a significant (R-squared 0.11; P = 0.043) negative relationship between L. maackii stem density and fine woody debris volume. Coarse woody debris volume was lower in sites with heavier invasion although no statistically discernible effects were detected. Regression analysis indicated a statistically significant negative relationship between L. maackii basal area and coarse woody debris volume (R-squared 0.14; P = 0.026). These results indicate linkage between invasion intensity and terrestrial subsidies mediated through the unique physiognomy of the invasive shrub. Riparian invasion of L. maackii may alter the fundamental biology of streams through alterations to deposition of terrestrial organic matter that serves as a structuring component of smaller waterways. • In areas of heavier invasion of Amur honeysuckle (L. maackii) there was less coarse woody debris. • In areas of heavier invasion of Amur honeysuckle (L. maackii) there was less fine woody debris • These results indicate linkage between invasion and terrestrial subsidies mediated through the physiognomy of the shrub. • Riparian invasion of L. maackii may alter the biology of streams through modification of allochthonous organic matter. [ABSTRACT FROM AUTHOR]