Rhamnus Cathartica Research Articles

How much care does a shrub-feeding hairstreak butterfly, Satyrium spini (Lepidoptera: Lycaenidae), need in calcareous grasslands?

Many butterfly target species are associated with early successional stages of grasslands. The Blue-spot Hairstreak, Satyrium spini (Denis & Schiffermuller, 1775), is a target species of grasslands. However, it feeds on Common Buckthorn (Rhamnus cathartica), which is associated with late successional stages of grasslands. If S. spini would also be restricted to late seral stages, there might be a management dilemma due to the contrasting requirements of S. spini and other target species. The aim of this study was to determine the oviposition preference of S. spini in calcareous grasslands, and to give management recommendations to promote this species. Therefore, we studied the oviposition microhabitats of S. spini at three representative patches of the Diemel Valley (Central Germany) by comparing environmental conditions on occupied and control host plants. In total we surveyed 1,889 host plants. Altogether we found 148 batches of S.spini on them containing 396 eggs. Most of the eggs were on plants that grew under the warmest conditions. Females preferred to lay eggs on small (< 1.3 m) shrubs of Rh. cathartica fully exposed to the sun growing on steep south- and west-facing slopes. This butterfly showed no difference in its preference for bushes growing in hedges or solitarily. About 80% of the batches of eggs were laid on the upper surface of a twig fork close to the surface of the ground (< 1 m). Our study showed that S. spini is a species characteristic of mid-successional stages of calcareous grasslands. The survival of suitable habitats for S. spini depends on regular management. To achieve this we recommend traditional rough grazing with sheep and goats, which creates open grasslands with small Rhamnus plants. In addition, the shrubs in tall hedges bordering calcareous grasslands should be subjected to cutting on a rotating basis.

The Forests of Isle Royale National Park: Can We Preserve This Pristine Wilderness in the Face of Climate Change?

Isle Royale National Park (IRNP) is an archipelago in west central Lake Superior. In 2010, the National Park Service Great Lakes Inventory and Monitoring Network initiated a long-term monitoring program at IRNP with the goals being to: (1) determine the current forest structure, (2) assess how succession and climate change will impact species assemblages, and (3) develop realistic management targets related to climate change impacts on IRNP forests. Five forest types were identified, with three of these (sugar maple (Acer saccharum Marsh.)/birch, eastern white cedar (Thuja occidentalis L), and balsam fir (Abies balsamea (L.) Mill.)) being climax types with little likelihood of succeeding into any other type over the next two to three decades. Two forest types (white spruce (Picea glauca (Moench) Voss),/trembling aspen (Populus tremuloides Michx.), and paper birch (Betula papyrifera Marsh.)) were in a state of transition. The long-term (> 50 year) successional pathways of all five forest types will be influenced by climate change, species' migration abilities, and disease. Many dominant species currently on the island, including balsam fir, black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.), and white spruce, are expected to become extirpated, while the abundance of other common species, including paper birch and trembling aspen, is expected to decline. The 21 km distance between the mainland and the islands will prohibit timely immigration of new species onto the island in the face of climate change. Immigration will likely be led by avian-dispersed species (Prunus spp., exotic Lonicera spp., and Rhamnus cathartica, another exotic species) with dispersal of other taxa relying on stochastic events or human transport. Managers should consider assisted migration to ensure that species assemblages remain congruent; otherwise, stable ecosystems dominated by a few non-native taxa may result. This is especially relevant on the eastern side of the island where balsam fir forests dominate in shallow, bedrock-derived soils.

Rhamnus cathartica: Notes on Its Early History in North America

Rhamnus cathartica (Common Buckthorn) is a well-established invasive species in North America. We searched early records of the species to help refine this species' history in North America. This note presents strong evidence of Common Buckthorn's entry to North America prior to the 19th century and suggests it was originally imported for medicinal, not ornamental, purposes. We then briefly discuss aspects of its expansion across North America to about the mid-19th century, when it was promoted as a hedge-forming plant. Such information is useful for reconstructing Common Buckthorn's invasion history (including reasons for its success), as well as for understanding human-invasive species interactions in general.

The characterisation by liquid chromatography of lake pigments prepared from European buckthorn (Rhamnus cathartica L.)

PurposeThe purpose of this paper is to prepare, analyse and measure the colour values of the lake pigments obtained from the reaction of Al3+, Fe2+ and Sn2+ metal salts with the natural dyes present in European buckthorn (Rhamnus cathartica L.).Design/methodology/approachA reversed‐phase high performance liquid chromatography (HPLC) with diode‐array detection method was utilised for the identification of buckthorn lake pigments. The extraction of dyes from the lake pigments was carried out with 37% hydrochloric acid/methanol/water (2:1:1; v/v/v) solution.FindingsAccording to the results of the HPLC analysis of the lake pigments, it was determined that rhamnetin, kaempferol, and emodin were present in the acid hydrolysed plant extract and in the lake pigment that was precipitated by Sn(II), quercetin‐3‐arabinosid, rhamnetin, and emodin were present in the non‐hydrolysed plant extract, and kaempferol, rhamnetin, isorhamnetin, and emodin were found in the lake pigment that was precipitated by Al(III). Rhamnetin and emodin were present in the lake pigment that was precipitated by Fe(II).Research limitations/implicationsIn the present context for the preparation of buckthorn lake pigments, a simple and practical method is presented. In addition, the analysis of the lake pigments was performed by reversed phase HPLC (RP‐HPLC) with diode array detector (DAD).Practical implicationsThe paper describes the preparation of lake pigments and their qualitative analysis. This method can be used to determine the origins of the dyestuffs used in historical art pieces.Originality/valueThe paper describes the development of methods for the analysis and the preparation of European buckthorn lake pigments.

Architectural strategies ofRhamnus cathartica(Rhamnaceae) in relation to canopy openness

While phenotypic plasticity is considered the major means that allows plant to cope with environmental heterogeneity, scant information is available on phenotypic plasticity of the whole-plant architecture in relation to ontogenic processes. We performed an architectural analysis to gain an understanding of the structural and ontogenic properties of common buckthorn ( Rhamnus cathartica L., Rhamnaceae) growing in the understory and under an open canopy. We found that ontogenic effects on growth need to be calibrated if a full description of phenotypic plasticity is to be obtained. Our analysis pointed to three levels of organization (or nested structural units) in R. cathartica. Their modulation in relation to light conditions leads to the expression of two architectural strategies that involve sets of traits known to confer competitive advantage in their respective environments. In the understory, the plant develops a tree-like form. Its strategy here is based on restricting investment in exploitation structures while promoting major vertical exploration and is probably key to species survival in the understory. Under an open canopy, the second strategy leads the plant to adopt a shrub-like shape. It develops densely branched exploitation structures and flowers abundantly and rapidly. This strategy perfectly matches its aggressive behaviour observed in full sunlight. We propose, as hypotheses, that these two light-related strategies are implicated in the ability of R. cathartica to outcompete the surrounding vegetation in a range of environmental conditions.

Re-investigation of the Anthraquinone Pool of Rhamnus spp.: Madagascin from the Fruits of Rhamnus cathartica and R. intermedia

As a continuation of our ongoing studies aimed at revealing the presence of oxyprenylated anthraquinones in plants belonging to the genus Rhamnus, in this paper we describe the extraction and HPLC separation of madagascin (3-isopentenyloxyemodin) from the fruits of R. cathartica L. and R. intermedia Steud. and Hochst. The title compound is described herein for the first time as a component of fruit extracts of Rhamnus species.

Brood Production byXylosandrus germanus(Coleoptera: Curculionidae) and Growth of Its Fungal Symbiont on Artificial Diet Based on Sawdust of Different Tree Species

ABSTRACT The ambrosia beetle Xyhsandrus germanus (Blanford) (Coleoptera: Curculionidae) is among the most important exotic pests of orchards and nurseries in the United States. It attacks a wide range of hosts and is difficult to control using conventional insecticides. As part of our studies on the biology and control of X. germanus, we are trying to optimize conditions for rearing beetle progeny to adulthood in the laboratory. In this study we tested the brood production by X. germanus reared on artificial diet based on sawdust from American beech (Fagus americana L.), black walnut (Juglans nigra. L.), European buckthorn (Rhamnus cathartica L.), and red oak (Quercus rubra L.). We also tested the growth of different strains of the beetle fungal symbiont, Ambrosiella hartigii Batra, on these sawdust diets. Among the sawdust types tested, we found significantly higher average number of progeny produced on diet made with sawdust from European buckthorn (43.9 ± 1.6) compared with those made with American bee...

Seeing the forest for the invasives: mapping buckthorn in the Oak Openings

Landsat TM and ETM+ satellite images from 2001 to 2011 were used to map the extent and change of the invasive shrubs common and glossy buckthorn (Frangula alnus and Rhamnus cathartica) at Irwin Prairie State Nature Preserve (IPSNP), and throughout Oak Openings, a 1,500 km2 region, located in NW Ohio, USA and SE Michigan near Lake Erie. In the Oak Openings, buckthorn directly threatens native biodiversity and habitat health of this globally rare ecosystem. Buckthorn that forms as dense shrub thicket in the understory is often obscured from satellite view by other canopy and is not spectrally dissimilar enough to be characterized using multispectral images. To address this, time series tasseled cap greenness images of land surface areas dominated by buckthorn thicket (which exhibit early leaf-out, late senescence) was used to identify areas covered by thicket with a heterogeneous background. A time series of vegetation index values was calculated from 49 Landsat images and combined with in-situ observations to define the land surface phenology of buckthorn thicket and other vegetation types. The phenological differences among land surfaces dominated by distinct vegetation types in the Oak Openings Region were used to map the extent of buckthorn thicket using a supervised classification method. Buckthorn thicket was identified in 0.43 % of the classified pixels (940 ha) in the 2007–2011 imagery and in 0.31 % (690 ha) of the 2001–2006 images. A Kappa test of the 2007–2011 classification yielded a value of 0.73 with 88 % overall accuracy of presence or absence of thicket based on 60 samples throughout the Oak Openings. The areal extent of buckthorn thicket increased by 39 % (255 ha) in the study area over the time period from 2001 to 2011.

Forest dynamics at Minnesota's prairie-forest border driven by invasive buckthorn (Rhamnus cathartica) and native bur oak (Quercus macrocarpa)1

Wyckoff, P. H., R. Greiman, A. Krueger, and L. Luce. (Biology Discipline, University of Minnesota, Morris, MN 56267). Forest dynamics at Minnesota's prairie-forest border driven by invasive buckthorn (Rhamnus cathartica) and native bur oak (Quercus macrocarpa). J. Torrey Bot. Soc. 139: 311–322. 2012.—Quercus macrocarpa Michx. (bur oak) is the key pioneer species as forests establish at the prairie-forest ecotone in western Minnesota, but invasive Rhamnus cathartica L. (European buckthorn) is an abundant and increasing secondary tree. Here we contrast microsite utilization and growth as a function of light and soil moisture for Q. macrocarpa and R. cathartica saplings at an ecotonal forest in an effort to establish the roles these two species are likely to play in near-term forest dynamics. Compared to Q. macrocarpa, R. cathartica saplings are found, on average, in darker microsites (P < 0.001) with higher soil moisture (P < 0.001), though the range of light levels at which saplings were seen to occur is much larger for Q. macrocarpa than for R. cathartica. We fit a variety of models which predict sapling growth and compared fits using AICc. With our best fitting models, light, size, and soil moisture together explain approximately half of the variation in growth among R. cathartica saplings and two-thirds of the variation in Q. macrocarpa. Most similar studies utilize models that include an a priori assumption that growth will asymptote with increasing light availability, but we find no evidence to support the use of asymptotic models. All top ranked models include light and sapling size, but the calculated importance of both light and soil moisture is dependent on the choice of growth metric, a disturbing finding given the variety of metrics utilized in the sapling growth literature. For neither species does the addition of soil moisture significantly improve growth models if the growth metric used is absolute radial stem growth increment, but soil moisture becomes important when absolute basal area increment is the growth metric for Q. macrocarpa, and when relative growth increment is used for either species. Limited success of R. cathartica in light, dry microsites suggests that the invasive tree may be near its climatic limit at our ecotonal forest site. At the same time, the relative success of the species in the dark understory of our warm dry forest suggests that near-term warming, with an expected increase in continental-climate drought, is unlikely to limit R. cathartica across the bulk of forests it has invaded in North America.

Moist Soils Reduce the Effectiveness of Glyphosate on Cut Stumps of Buckthorn

ABSTRACT: Application of glyphosate to cut stumps is broadly viewed as an effective way to control invasive woody shrubs like the buckthorn species (Rhamnus cathartica L. and Frangula alnus Mill.). Since the primary cost associated with this control method is labor, identifying factors that improve efficacy is important. The objective of this research was to determine the effect of glyphosate concentration and soil moisture on the control of buckthorn using the cut-stump method. More than 600 mature buckthorn plants were cut and treated with glyphosate at concentrations between 0 and 41% active ingredient during October in soils varying from dry to moist. While increased glyphosate concentration improved control rates, soil moisture played a dominant role. In moist soils, the impact of glyphosate concentration was insignificant (z=-1.723, p=0.085), and between 40% and 60% of treated buckthorn plants escaped control at all glyphosate concentrations. In dry soils, however, control rates increased significan...

Anthraquinone chemical fingerprint: Madagascin from the fruits of Rhamnus L. Spp.

Prenylation is the chemical or enzymatic addition of a terpenyl moiety to an accepting molecule that occurs in nature in plant families like Rutaceae, Asteraceae, Apiaceae, Clusiaceae, Fabaceae. As a continutation of our studies [1-3] we report herein the determination of madagascin from the fruits of Rhamnus cathartica L., R. fallax Boiss., R. intermedia Steud. & Hochst., and R. rupestris Royle. The title compound is described for the first time as a component of fruit extracts and is noteworthy to underline that this compound was found only in Rhamnus cathartica L. and R. intermedia Steud. & Hochst., at 14.31 and 4.63 g/g of fruit (dry weight), respectively.

Contrasting natural regeneration and tree planting in fourteen North American cities

Field data from randomly located plots in 12 cities in the United States and Canada were used to estimate the proportion of the existing tree population that was planted or occurred via natural regeneration. In addition, two cities (Baltimore and Syracuse) were recently re-sampled to estimate the proportion of newly established trees that were planted. Results for the existing tree populations reveal that, on average, about 1 in 3 trees are planted in cities. Land uses and tree species with the highest proportion of trees planted were residential (74.8 percent of trees planted) and commercial/industrial (61.2 percent) lands, and Gleditsia triacanthos (95.1 percent) and Pinus nigra (91.8 percent). The percentage of the tree population planted is greater in cities developed in grassland areas as compared to cities developed in forests and tends to increase with increased population density and percent impervious cover in cities. New tree influx rates ranged from 4.0trees/ha/yr in Baltimore to 8.6trees/ha/yr in Syracuse. About 1 in 20 trees (Baltimore) and 1 in 12 trees (Syracuse) were planted in newly established tree populations. In Syracuse, the recent tree influx has been dominated by Rhamnus cathartica, an exotic invasive species. Without tree planting and management, the urban forest composition in some cities will likely shift to more pioneer or invasive tree species in the near term. As these species typically are smaller and have shorter life-spans, the ability of city systems to sustain more large, long-lived tree species may require human intervention through tree planting and maintenance. Data on tree regeneration and planting proportions and rates can be used to help determine tree planting rates necessary to attain desired tree cover and species composition goals.

The association of two invasive shrubs, common buckthorn (Rhamnus cathartica) and Tartarian honeysuckle (Lonicera tatarica), with oak communities in the midwestern United States

Oak forests throughout North America are declining due to changes in disturbance regimes that have led to increased competition from other tree and shrub species. We evaluated associations between oak regeneration, the occurrence of two common invasive shrubs (common buckthorn ( Rhamnus cathartica L.) and Tartarian honeysuckle ( Lonicera tatarica L.)), and forest edges in oak forests in a portion of the midwestern United States where bur ( Quercus macrocarpa Michx.), red ( Quercus rubra L.), and white oak ( Quercus alba L.) were historically dominant. We found poor recruitment of oaks in comparison to other, more shade-tolerant tree species. Results further revealed a strong stand-scale association between bur oak, open canopy conditions, high soil nutrient levels, and the presence of common buckthorn and Tartarian honeysuckle; these same site characteristics were disassociated with red and white oak. Within red and white oak stands, however, the presence of the invasive shrubs was more pronounced near forest edges. While oak recruitment is hampered throughout stands, our research suggests that predominant constraints may vary based on soil and light gradients found along forest edges.

Anthraquinone Profile, Antioxidant and Antimicrobial Properties of Bark Extracts of Rhamnus catharticus and R. orbiculatus

The anthraquinone profile, antioxidant and antimicrobial activities as well as the total phenol and total flavonoid contents were determined in methanol extracts of the barks of Rhamnus catharticus L. and R. orbiculatus Bornm. The most abundant anthraquinone derivatives in R. catharticus were physcion (67.8%) and emodin (26.2%), while R. orbiculatus contained mostly physcion (81.3%) and chrysophanol (14.6%). R. catharticus displayed better activity in the beta-carotene-linoleic acid assay, as well as chelating activity, whereas its activity in the reducing power assay was significantly lower than that of R. orbiculatus. Both methanol extracts showed antimicrobial activity against all microbial species tested (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, Aspergillus niger, Microsporum gypseum) with MIC values either equal to or lower than 2.50 mg/mL. R. catharticus and R. orbiculatus contained several anthranoid aglycones and their bark extracts demonstrated notable antioxidant and antimicrobial properties. The results obtained indicate the medicinal potential of these two species.

Genetic variability of the narrow endemic Rhamnus persicifolia Moris (Rhamnaceae) and its implications for conservation

Rhamnus persicifolia Moris is an endemic small tree belonging to the Rhamnus cathartica group, growing along mountainous streams of Central-Eastern Sardinia (Italy). ISSR markers were used to detect the genetic diversity within and among six populations representative of the species distribution range. In spite of the limited distribution of this endemic taxon, fairly high levels of genetic diversity were detected. Percentage of polymorphic bands (PPB), gene diversity ( H S and H T ) and Shannon information measure (Sh) were calculated both at population (PPB = 30.70%, H S = 0.1105, Sh = 0.1646) and at species level (PPB = 68.42%, H T = 0.2066, Sh = 0.3139). The existence of a spatial distribution of genetic diversity in R. persicifolia was revealed by a low gene flow, a fairly high level of genetic differentiation ( G ST = 0.4583) among populations and a positive correlation between genetic and geographic distances (Mantel test, r = 0.71, p = 0.016). The spatial genetic structure was also confirmed with BAPS analysis. Our results show that a certain level of isolation by distance and sex-ratio bias may explain the distribution of genetic diversity among populations. Conservation measures are suggested on the basis of the genetic diversity detected, by implementing an integrated in situ and ex situ conservation program for each population, in order to ensure effective protection for this endemic species. ► Rhamnus persicifolia an endemic tree growing in Sardinia (Italy) was studied. ► ISSR detected the genetic diversity within and among populations of the species. ► Quite high levels of genetic diversity were detected at both levels. ► A spatial genetic structure was detected with BAPS analysis. ► Measures are suggested for integrated in situ and ex situ conservation programs.

Woody Invasions of Urban Trails and the Changing Face of Urban Forests in the Great Plains, USA

Corridors such as roads and trails can facilitate invasions by non-native plant species. The open, disturbed habitat associated with corridors provides favorable growing conditions for many non-native plant species. Bike trails are a corridor system common to many urban areas that have not been studied for their potential role in plant invasions. We sampled five linear segments of urban forest along bike trails in Lincoln, Nebraska to assess the invasion of woody non-native species relative to corridors and to assess the composition of these urban forests. The most abundant plant species were generally native species, but five non-native species were also present: white mulberry (Morus alba), common buckthorn (Rhamnus cathartica), tree-of-heaven (Ailanthus altissima), honeysuckle (Lonicera spp.) and elm (Ulmus spp.). The distribution of two of the woody species sampled, common buckthorn and honeysuckle, significantly decreased with increasing distance from a source patch of vegetation (P = 0.031 and 0.030). These linear habitats are being invaded by non-native tree and shrub species, which may change the structure of these urban forest corridors. If non-native woody plant species become abundant in the future, they may homogenize the plant community and reduce native biodiversity in these areas.

Xerothermic vegetation of fallow lands in western Małopolska

In 2005-2011 the occurrence of xerothermic vegetation on fallow lands located on hills near Trzebinia and Jaworzno was studied. The Braun-Blanquet releves were performed on SE, S and SW slopes. Well-drained brown loamy soils developed on shallow sands on Triassic dolomites, lime-stone and Myślachowice conglomerate dominating at the sites. Investigations were also conducted on amid-field balks and fallow lands where in 2005 moderate agricultural activity was resumed. In general, superficial ploughing has not eliminated plant cover, but only disturbed turf and uncovered soil seed bank of former cultivation weeds.Fields 10-15 years after they had been abandoned, were dominated by the Dauco-Picridetum hieracioidis xerothermic ruderal association, with considerable share of Malva alcea and Verbascum species (V densiflorum, V. lychnitis, V. phlomoides and V. thapsus) in younger fallows. These communities were characterized by occurrence of xerothermic grasslands and warm thickets taxons from Festuco-Brometea and Trifolio-Geranietea sanguinei classes, i.a.: Achillea pannonica, Allium scorodoprasum, Bromus erectus, Centaurea stoebe, Cerinthe minor, Filipendula vulgaris, Fragaria viridis, Gentianella ciliata, Phleum phleoides, Valeriana angustifolia, Veronica spicata, Viola hirta and Thesium linophyllon.Additionally, on ploughed fallows in gaps of turf numerous annual and biennial segetal as well as ruderal species were observed. In many places thermophilous segetal association of Papaveretum argemones developed, in which a significant share of Avena fatua, Camelina microcarpa subsp. sylvestris, Consolida regalis, Lithospermum arvense and Papaver rhoeas was noted in addition to Arabidopsis thaliana, Papaver argemone and Veronica triphyllos.The oldest fallows (20-25 years after abandonment), amid-fields steep slopes and balks were covered by Geranio-Peucedanietum cervariae associations. Their physiognomy was formed by Agrimonia eupatoria, Brachypodium pinnatum and Origanum vulgare, sometimes also by Geranium sanguineum, Peucedanum cervaria and P. oreoselinum. This vegetation was in spatial contact with thermophilous thickets of Berberidion alliance with Cornus sanguinea, Crataegus monogyna, Prunus spinosa, Rhamnus cathartica, and Rosa canina.On xerothermic post-agricultural areas specific stable communities formed by thermophilous species from meadows, ruderals, grasslands and thickets occurred. A new phenomenon of recent years, related to EU benefits - superficial ploughing of fallows, not followed by regular cultivation - favours segetal vegetation. Weeds communities are regressing in Europe as an effect of modern agriculture. Post-agricultural secondary habitats are important elements that should be taken into account in studies of appearance and protection of xerothermic plants.

Dominance by the introduced tree Rhamnus cathartica (common buckthorn) may limit aboveground carbon storage in Southern Wisconsin forests

Many ecosystems are now dominated by introduced species, and because dominant species drive ecosystem properties, these changes lead to increased uncertainty in estimates of carbon storage and cycling. We examined aboveground biomass in forests dominated by the introduced tree Rhamnus cathartica (common buckthorn) relative to forests dominated by native species, and measured aboveground biomass increment over a three-year period (2005–2008). Three of the four lowest biomass levels occurred in R. cathartica-dominated forests, and biomass in these forest types was stored primarily in trees 10–20cm DBH. By contrast, forests dominated by native trees (including those with R. cathartica understories) had the six highest biomass levels, and biomass was stored primarily in trees >50cm DBH. On average, forests dominated by R. cathartica stored half as much aboveground biomass (14.6±3.3kg/m2) as forests dominated by native tree species (28.9±8.3kg/m2). R. cathartica-dominated forests also had half the aboveground biomass increment of native-dominated forests (0.28 vs. 0.60kg/m2/year). Although known anecdotally as a fast-growing species, R. cathartica growth rates declined with increasing size. Between 2005 and 2008, R. cathartica individuals <10cm DBH grew faster than native species; however, R. cathartica individuals >10cm DBH grew consistently slower than native species. Overall, our findings indicate that intrinsic size limitations on R. cathartica will lead to lower biomass stocks in forests where it acts as a canopy dominant relative to forests dominated by native tree species.

Rural housing is related to plant invasions in forests of southern Wisconsin, USA

Forests throughout the US are invaded by non-native invasive plants. Rural housing may contribute to non-native plant invasions by introducing plants via landscaping, and by creating habitat conditions favorable for invaders. The objective of this paper was to test the hypothesis that rural housing is a significant factor explaining the distribution of invasive non-native plants in temperate forests of the Midwestern US. In the Baraboo Hills, Wisconsin, we sampled 105 plots in forest interiors. We recorded richness and abundance of the most common invasive non-native plants and measured rural housing, human-caused landscape fragmentation (e.g. roads and forest edges), forest structure and topography. We used regression analysis to identify the variables more related to the distribution of non-native invasive plants (best subset and hierarchical partitioning analyses for richness and abundance and logistic regression for presence/absence of individual species). Housing variables had the strongest association with richness of non-native invasive plants along with distance to forest edge and elevation, while the number of houses in a 1 km buffer around each plot was the variable most strongly associated with abundance of non-native invasive plants. Rhamnus cathartica and Lonicera spp. were most strongly associated with rural housing and fragmentation. Berberis thumbergii and Rosa multiflora were associated with gentle slopes and low elevation, while Alliaria petiolata was associated with higher cover of native vegetation and stands with no recent logging history. Housing development inside or adjacent to forests of high conservation value and the use of non-native invasive plants for landscaping should be discouraged.

Above‐ and Belowground Impacts of European Buckthorn (Rhamnus cathartica) on Four Native Forbs

Fast‐growing European buckthorn (Rhamnus cathartica) shrubs are aggressively invading woodlands in eastern and midwestern North America. Buckthorn casts dense shade, alters soil conditions, and may be allelopathic. We used greenhouse and field experiments to investigate above‐ and belowground effects ofRhamnuson four herbaceous species native to southern Wisconsin. In the greenhouse, we assessed howRhamnusleaves and fruit affected seed germination and seedling growth relative to sugar maple (Acer saccharum) leaves. Fewer seeds ofEurybia macrophyllaandThalictrum dasycarpumgerminated underRhamnusleaves, and those that germinated were slowed. We planted seedlings of the four natives into four treatments at three sites in the field to assess how their survival, growth, and flowering respond to the separate and combined effects of light levels, buckthorn canopies, and buckthorn soils. Buckthorn consistently reduced native plant performance by diminishing survival, flowering, and growth inThalictrum, survival and flowering inEurybia, and flowering and growth inSymphyotrichum lateriflorum. Removing buckthorn canopies enhanced growth of these native species, but buckthorn soils separately inhibited growth at least as much (despite being more fertile). Buckthorn's impacts on native plants exceed effects attributable to light levels and soil fertility, suggesting allelopathy. Buckthorn reduced performance more in the uncommon species (ThalictrumandEurybia) than the common species (Geranium maculatumandSymphyotrichum). As we do not yet know how long these inhibitory soil effects persist, we need additional research to learn how best to control buckthorn's impacts on native plant communities.