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Species
Rhamnus cathartica L.
IUCN
NCBI
EOL Text
"Notes: Western Ghats, Cultivated, Native of Tropical America"
Habit: Shrub or tree
More info for the terms: bog, competition, cover, density, litter, peat, shrub, shrubs
Common buckthorn seedlings can occur at high densities near adult conspecifics, and seedling mortality rates may be relatively low in some areas. Seedlings may establish best in areas with shallow litter or bare soil.
Common buckthorn seedlings, sometimes in high densities, are often observed near parent shrubs in invaded areas [6,74,144,175,243] (see stand structure), and densities of common buckthorn seedlings beneath parent shrubs may be higher than in surrounding areas [144,175,243]. Common buckthorn seedling density beneath a dense common buckthorn stand near Saskatoon averaged 110.8 seedlings/m² at the end of the first growing season; by early spring the following year it had increased to 123.7 seedlings/m². Seedling density was lower (~74 seedlings/m²) in a sample quadrats adjacent to a game trail where the soil was very compacted, but even there common buckthorn dominated the ground layer [6]. In Sifton Bog and the Medway Valley in London, Ontario, researchers recorded over 900 common buckthorn seedlings/m² in some quadrats beneath large female trees but usually <5 seedlings/m² beneath male trees (Norman and others unpublished data cited by [175]). Common buckthorn seedlings were common throughout 4 study sites in west-central Minnesota, and seedling abundance increased exponentially with abundance of overstory common buckthorn [243]. In central New York, common buckthorn seedlings were positively associated with fruiting adult plants on 4 old-field plots and on 2 of 4 plantation plots (P<0.05) [144].
Mature common buckthorn shrubs may have positive or neutral effects on common buckthorn seedling growth and survival. At the Warner Nature Center in east-central Minnesota, common buckthorn seedlings growing near mature conspecifics exhibited greater growth and survival than seedlings far from mature shrubs in similar light environments [118], possibly due to increased fertility from common buckthorn leaf litter [115]. In a garden in Europe, common buckthorn seedling mortality rates were not significantly different (P>0.05) under common buckthorn shrubs and other shrub species [119].
While a common buckthorn canopy does not appear to reduce seedling establishment and growth, it may inhibit seedling persistance. Researchers recorded densities of 20 to 200 large (3- to 12-inch (7-30 cm) tall) common buckthorn seedlings/m² beneath the female trees near London, Ontario; however, few taller seedlings were recorded (Norman and others unpublished data cited by [175]). Many common buckthorn seedlings were observed growing under parent trees at the University of Wisconsin Arboretum; however, common buckthorn saplings seemed not to survive under parent trees, while saplings around the canopy perimeters did [74]. Differences among studies may be due to differences in stand structure and corresponding light levels experienced by the seedlings, or difference in other site characteristics that can influence common buckthorn seedling establishment, survival, and growth.
Common buckthorn seedling emergence may be better on bare soil than on soil with a dense litter or herbaceous layer, although persistence may be similar among microsites. In field tests, a higher percentage of common buckthorn seed germinated on bare soil than on soil with a dense litter or herbaceous layer. While germination was better on bare soil, survival to the next spring was similar among treatments with bare soil, bare and scratched soil, and dense herbaceous cover [74]. Fewer common buckthorn seedlings were observed in sites with thick red oak leaf litter than in sites with less leaf litter at Eagle Lake Park, Minnesota. Common buckthorn seedling emergence, height, and biomass decreased with increasing litter depth in both field (open oak woodlands) and greenhouse studies, but litter depths up to 2 inches (5.1 cm) did not prevent seedling emergence and survival [18].
Photos by S. Kelly Kearns |
The effects of litter on common buckthorn seedling establishment may be related to reduced light and lower temperatures associated with litter. Regression analyses showed that common buckthorn seedling density decreased with lower light transmittance in both greenhouse and field studies, and increasing soil temperature increased common buckthorn seedling establishment in the greenhouse [18]. See Shade tolerance for more information on the effects of light on common buckthorn seedling establishment and growth.
Other site characteristics may influence common buckthorn seedling establishment and persistence. A regression model found a positive correlation between common buckthorn seedling density and soil cation exchange capacity and percent clay (P<0.05), both of which are related to soil water holding capacity [131]. Preliminary results suggest that North American soil biota may impact common buckthorn growth. European soil biota did not have a negative effect on common buckthorn, except in low light. North American soil biota had a large negative effect on common buckthorn in all light levels, which was consistent on common buckthorn individuals from 4 different populations [115].
Seedling mortality: Reported mortality rates of common buckthorn seedlings vary among studies and observations, likely a result of differences in site characteristics and plant and animal community compositions. Studies comparing establishment and survival of European shrub species found common buckthorn was among the species with the lowest mortality rates [80,119]. Researchers in London, Ontario, recorded high densities of common buckthorn seedlings under parent plants but noted that most seedlings died in their first summer, probably from drought, predation, and/or deep shade (Norman and others unpublished data cited by [175]). In Madison County, New York, common buckthorn seedlings in maple forest plots experienced higher mortality rates (>60%) than those in old field and plantation plots (~30% mortality). Causes of mortality were uncertain [143].
Mortality of common buckthorn seedlings may result from a variety of causes, including desiccation, frost, fungal pathogens, herbivory, and competition for resources from other plant species [65,119,143,175]. Common buckthorn seedling mortality due to frost damage has been observed in old fields in New York [65] and on peat soils in Europe [71]. Observations of common buckthorn seedlings in Ontario suggest that seedlings that emerged in spring were mature enough to withstand frost damage the following winter [175].
Herbivory may be a major cause of common buckthorn seedling mortality on some sites. In old fields in central New York, survival of common buckthorn seedlings was 5 times lower for seedlings growing under herbs than those growing in the open. During the growing season, herbivory by rodents (especially meadow voles) was the main source of mortality in both microsite types. Over winter, frost heaving caused 62% of seedling mortality in open microsites and 40% under herbs, while herbivory caused 60% of mortality of under herbs. Overall survivorship during the study was greatest in the open. The probability that seeds of common buckthorn landing in the open would produce seedlings that survived until the end of the 1st growing season was 0.23 and until the beginning of the 2nd season was 0.15. The probability that seeds under herbs would produce seedlings that survived to the end of the 1st growing season was 0.00012 and until the beginning of the 2nd season was 0.00007 [65]. Common buckthorn seedlings may be more vulnerable to herbivory in old fields than in plantations or sugar maple forests [143].
More info for the terms: allelopathy, litter, natural, nonnative species, presence, severity, shrubs, succession, tree
Invasive populations of common buckthorn may impact plant community composition and structure, leaf litter decomposition, nutrient cycling, and soil biota. See Influence on succession and plant community dynamics for more information on these topics. Knight and others [116] suggest that the magnitude and direction of effects of common buckthorn on native plants and animals in invaded ecosystems in North America are not well understood, and more research is needed in this area. Isolating and quantifying the effects of common buckthorn invasion is complicated by the impacts of other changes in invaded communities including anthropogenic disturbances, the presence of other nonnative invasive plants, Dutch elm disease, white-tailed deer overpopulation, nonnative earthworm invasion, altered flooding regimes, and climate change [3,82,97,116]. Although Dirr [48] has seen Dahurian buckthorn "literally consume waste areas", no information was available as of this writing (2010) on the impacts of Dahurian buckthorn on native communities.
Invasive populations of common buckthorn may impact native animals, especially birds. Although birds consume common buckthorn fruits and the shrubs provide nesting sites (see Birds), similar native shrubs likely provide better nesting sites. On a site in an urban reserve outside Chicago, American robin nests in common buckthorn experienced higher rates of predation than nests in hawthorns. Common buckthorn lacks the sharp thorns that characterize hawthorn, which may increase nest predation. Predation of wood thrush nests was lower in common buckthorn than in native viburnum, but predation was similar to that in hawthorns and native tree species such as maples, hophornbeam, and plums [190].
Common buckthorn is considered a poisonous plant in the United States and Canada [175], and Dahurian buckthorn is also said to be toxic if ingested [43]. Common buckthorn bark, leaves, and fruits are strongly purgative when consumed. Other effects include nausea, stomach cramps, gastroenteritis, diarrhea, and irritation of the gastrointestinal mucosa to the point of bleeding. Poisoning is rare but has been reported in Europe. Consumption of common buckthorn in sufficient quantity causes poisoning in cattle, reduces milk quantity and quality, and even affects the meat [175]. Following an outbreak of an idiopathic neurological disease in horses in Illinois, common buckthorn was identified as a possible cause, and a study was undertaken to assess its toxicity in mice. Researchers found that compounds in common buckthorn interfered with glycogen metabolism, causing abnormal changes in liver cells. The authors concluded that common buckthorn could not be ruled out as a cause of the neurologic disorder in the horses, and that further research was needed to determine whether liver injury in mice would progress [132]. No additional studies on this topic were found as of 2010.
Common buckthorn is an overwintering host for 2 invasive crop pests, oat crown rust (Puccinea coronata) and the soybean aphid (Aphis glycines). Oat crown rust infestations tend to be more severe in oat crops located near common buckthorn plants, and removal of common buckthorn in the vicinity of oat fields has long been recommended for reducing the severity of rust infection [175]. The nonnative soybean aphid first appeared in Wisconsin in 2000, and within 4 years, it spread to 21 states and 3 Canadian provinces, putting more than 60 million acres (24 million ha) of soybean at risk to crop injury. Common buckthorn occurs over much of this area. In China and Japan, the most common overwintering hosts for the soybean aphid are Dahurian buckthorn and Japanese buckthorn (Rhamnus japonica). Dahurian buckthorn would likely be a primary host for soybean aphid in North America; however, Dahurian buckthorn is so uncommon in the soybean production areas that it is unlikely to be an important host [176]. Heimpel and others [91] provide a detailed discussion on the interactions of common buckthorn and the soybean aphid, discuss how these 2 organisms are components of an extensive invasional meltdown in North America, and discuss management issues surrounding these and 9 other cofacilitating Eurasian species.
Based on perceived or observed impacts, common buckthorn has been classified as a pest plant in several states and provinces:
Pest plant classification of common buckthorn in several US locations | ||
Location | Classification | Definition |
Minnesota | Restricted noxious weed | Importation, sale, and transportation of plants or propagating parts is illegal in the state [151] |
Missouri | Category A-3 plant | Plant species that are invading and disrupting native plant communities in 10 or fewer Missouri counties [152] |
Tennessee | Watch List B | Nonnative plant species that are severe problems in surrounding states but not yet reported in Tennessee as of 2001 [213] |
Vermont | Class B noxious weed | Nonnative species that are known to occur in Vermont and are considered to pose a serious threat. The movement, sale, and/or distribution of these plants are prohibited [223] |
Eastern Region | Category 1 plant | Nonnative, highly invasive plants which invade natural habitats and replace native species [216] |
In a survey of 60 land managers in Wisconsin, common buckthorn was one of the most frequently reported nonnative plants, and it was ranked among those having the greatest impact (3rd out of 66). It was perceived to be difficult to control and spreading on both recently disturbed and relatively undisturbed sites [179]. Common buckthorn was considered a "high" priority on the Ottawa National Forest in northern Michigan, where it occurred on 14 known sites with a total known infested area of 3 acres as of May 2005 [217]. Common buckthorn was rated among the "3 most important established and widespread invasive plants that warrants research" by 13% of land managers surveyed in the Midwest (Iowa, Illinois, Indiana, Michigan, Minnesota, Missouri, Ohio, and Wisconsin); however, less than 7% of researchers surveyed included common buckthorn in the top 3 [180]. Common buckthorn is one of several plants "voted as" invasive by the Massachusetts Invasive Plant Advisory Group [141].
Allelopathy: Secondary compounds, particularly emodin, have been found in many buckthorn species including common buckthorn [116]. It has been suggested that these compounds may contribute to invasion success. For example, emodin may deter insects and other herbivores from eating common buckthorn leaves, bark, and fruits, protect plants from pathogens and high light levels, have allelopathic effects on nearby plants, affect soil microorganisms, and affect fruit consumption and digestion by birds (Izhaki 2002 as cited by [116]).
Evidence for allelopathy from common buckthorn exudates is not consistent. Archibold and others [6] found no reduction in germination of crop seeds exposed to leachates from common buckthorn leaves. Conversely, Seltzner and Eddy (2003 as cited by [116]) found that common buckthorn leaf exudates reduced alfalfa (Medicago sativa) seed germination by 42%, and fruit exudates reduced germination to <1%; and Vincent (2006 as cited by [175]) found that common buckthorn fruit extracts reduced germination in crop seeds, and common buckthorn fruit debris reduced growth of crop seedlings. It has been suggested that emodin in common buckthorn fruits could adversely affect growth of native plants beneath common buckthorn canopies and that these effects may vary seasonally as well as among individual common buckthorn trees (Wilson personal communication cited by [116]). A review by Knight and others [116] suggests that more research is needed to understand the ecological significance of secondary chemicals in common buckthorn.
No information was available regarding allelopathy in Dahurian buckthorn (as of 2010).
Common Buckthorn is occasional to locally common in central and northern Illinois; it is less common or absent in the southern section of the state (see Distribution Map). This species is undoubtedly more widespread than official records indicate; it was introduced from Eurasia as a hedge and landscaping plant. Habitats include disturbed woodlands, woodland borders, thickets, fence rows, vacant lots, and miscellaneous waste areas. Common Buckthorn has the capacity to displace native plants in their natural habitats.
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | Copyright © 2002-2014 by Dr. John Hilty |
Source | http://www.illinoiswildflowers.info/trees/plants/cm_buckthorn.htm |
More info for the terms: density, fresh, litter, presence
Some fresh common buckthorn seed is germinable and does not require scarification or stratification for germination [2,69,175,215]; however, seeds must be extracted from fruits for germination to occur [6,74], and scarification may increase germination rate [74,175]. Germination rates are higher for seeds that have overwintered in the field than for fresh seeds [6,175,204]. Common buckthorn seedling emergence is inhibited by a litter or herbaceous layer [18,65,118] and is increased by soil disturbance [18,65,74].
Common buckthorn seedlings do not emerge from intact fruits. Seeds dispersed in fruits may not germinate until the following spring, probably after the fruit has decayed or been consumed by animals [6]; this allows the entire growing season for seedling establishment. Seeds that overwintered in the field did not germinate with the pulp left on. With pulp removal, germination percentages ranged from 76% to 92%. Mean time to germination was about 42 days, and germination peaked at 34 to 40 days [6,74]. Dupont and others (1997 cited by [175]) suggested that the role of frugivores was more to remove the pulp of the fruit than to break dormancy or scarify seed during passage through the digestive system.
Effects of passage of common buckthorn seeds through an animal's digestive system are unclear, though it may hasten germination. Acid scarification of common buckthorn seeds has shown variable effects on germination (e.g., [65,74,116]). Leaching seeds in running water for 2 hours, exposure to concentrated sulfuric acid for 1 minute, or rubbing seeds between 2 layers of fine sandpaper increased both the rapidity and percentage of common buckthorn germination (Govinthasamy and Cavers unpublished data cited by [175]).
Some fully mature common buckthorn seeds lack dormancy [215], and several authors [2,69,175,215] report some germination of fresh seeds. Cold stratification may not be required for germination; however, total percent germination and germination rate were higher for seeds that were either exposed to cold temperatures in the laboratory [175,215] or that overwintered under field conditions [6,175,204] than for fresh or unstratified seeds. This may be why some authors recommend prechilling or state that common buckthorn requires cold stratification [13,175]. Fresh, undried seeds of common buckthorn germinated without stratification when exposed to alternating temperature regimes [215].
Percent germination and germination rate of fresh common buckthorn seed exposed to different alternating temperature regimes [215] | ||||
Temperature regime (°C) | 3/25 | 20/30 | 3/15 | 3/20 |
Maximum germination | 22-45% | 86-95% | 0 | 0 |
Time to reach 50% of maximum | 6 to 11 weeks | 2.5 to 3.5 weeks | -- | -- |
Germination of common buckthorn and native Carolina buckthorn were compared in a greenhouse study. Germination percentage for common buckthorn was 48% after 0 days of cold stratification, was greatest (85%) after 42 days of cold stratification, and declined slightly after 112 days of stratification. Mean daily germination of common buckthorn consistently exceeded that of Carolina buckthorn [204].
Common buckthorn has higher seedling emergence rates in bare soil than in the presence of herbaceous plants [65,74] or leaf litter [18,74]. Removal of surface litter with prescribed spring fires increased common buckthorn seedling density [18]. Soil disturbance and/or leaf litter removal may produce a flush of common buckthorn germination by stirring up dormant, buried seed and exposing it to light. Ela (1981 unpublished report cited by [74]) found that large numbers of common buckthorn seedlings established in areas where the soil was disturbed in the process of clearing Bell's honeysuckle from a site. In field tests, more common buckthorn seed germinated on bare soil than on soil with a dense litter layer (allowing no light to reach the soil surface) or herbaceous layer (allowing approximately 10% of the ambient light to reach the soil surface), although variation was high and differences were not significant. More common buckthorn seedlings established than the total number of seeds that were planted, probably because common buckthorn seeds already in the soil germinated after removal of the leaf litter [74]. Average cumulative emergence from early May to late June for common buckthorn was 28%, 7%, and 23% in plots with bare soil, 1-year-old herbs, or 15-year-old herbs, respectively. This suggests that early-successional herbs may have inhibited common buckthorn emergence [65]. Bisikwa [18] reported that increased depths of surface litter decreased seedling emergence and establishment of common buckthorn in both field and greenhouse experiments in Minnesota (see Seedling establishment for more details).
Exposure to light may enhance germination of common buckthorn seed in disturbed soil; however, a review by Qaderi and others [175] suggests there is no light requirement for common buckthorn seed germination. Greenhouse experiments comparing 4 light intensities found the lowest germination percentages occurred in the highest light intensity (100%), greatest germination at the 50% level (P<0.001), and germination at 25% and 12.5% full daylight was intermediate [74]. In another study, common buckthorn seeds took 23 to 59 days to germinate in light or dark, with 44% germination in light and 24% germination in dark [153].
Prolonged flooding may be detrimental to common buckthorn germination. A slight decline in germination was noted in seeds following immersion for 2 weeks. The mean germination rate for these seeds was 77%, with a mean time to emergence of 44 days. No germination occurred in seeds that were immersed for 2 months [6]. The highest germination rates occurred in moist but not saturated soil [74].
The preference is light shade to full sun and moist to slightly dry conditions. This adaptable woody plant tolerates different kinds of soil; it is can reseed itself aggressively and become a pest.
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | Copyright © 2002-2014 by Dr. John Hilty |
Source | http://www.illinoiswildflowers.info/trees/plants/cm_buckthorn.htm |
Common Buckthorn is occasional to locally common in central and northern Illinois; it is less common or absent in the southern section of the state (see Distribution Map). This species is undoubtedly more widespread than official records indicate; it was introduced from Eurasia as a hedge and landscaping plant. Habitats include disturbed woodlands, woodland borders, thickets, fence rows, vacant lots, and miscellaneous waste areas. Common Buckthorn has the capacity to displace native plants in their natural habitats.
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | Copyright © 2002-2014 by Dr. John Hilty |
Source | http://www.illinoiswildflowers.info/trees/plants/cm_buckthorn.htm |
More info for the terms: alliance, alvar, association, cover, density, fen, frequency, importance value, interference, invasive species, mesic, natural, peat, reclamation, resistance, shrub, shrubs, succession, tree, xeric
- Common buckthorn general site characteristics
- Dahurian buckthorn general site characteristics
- Climate
- Elevation, topography, and soil depth
- Soil nutrients, mineralogy, and parent material
- Soil moisture and texture
- Soil disturbance
Common buckthorn general site characteristics: In its native range, common buckthorn occurs on hillsides, mountain tops, and valleys [120]. It grows in well-drained sand, clay, or poorly drained calcareous or alkaline soils, and it prefers neutral or alkaline soils. In Great Britain, common buckthorn may be more abundant at the foot of chalk escarpments than on the slope [71]. In Great Britain, common buckthorn often occurs in shrublands and wetlands on limestone soils, and as an understory shrub in open woodlands on limestone soils. It is particularly frequent in areas with big outcrops of calcareous rock, especially chalk and oolite, or in large alkaline fens, and it avoids dry exposed places on the chalk. Common buckthorn occurs on all soil types in Europe but grows best on limestone soils with pH 6.5 to 8.5. On alkaline fen peat it tolerates very high soil moisture, with the water table at or above soil level in winter and falling a few decimeters in summer. Humus content of fen peat averages 68% at 8 inches (20 cm); average calcium carbonate content in upper 8 inches is 0.25% [71]. In central Europe, common buckthorn occurs on dry and very dry calcareous slopes, floodplains, and in partially dried swamps [130].
Common buckthorn's distribution extends northward through the greater part of Europe to 60° 48' in Norway and 61° 41' in Sweden and is present sparingly at high altitudes in northern Africa. It is typically a lowland species and is an "index plant" for elevation zones up to 1,100 feet (335 m) in Great Britain; up to 5,300 feet (1,600 m) in Switzerland; and up to 5,900 feet (1,800 m) in Morocco [71].
In North America, distribution of common buckthorn seems to correspond with high human population density [74], and common buckthorn frequently occurs in human-modified environments including pastures [55,74,194,209,225] and field edges [12], along fence rows [55,74,209,225], roadsides [12,74,138,194,209,225], railroads [12,225], in vacant lots [225], hedgerows [35,194], clearings [225], "waste places" [138], woodlots and disturbed woods [35,74], cultivated areas, and around dwellings [74].
Common buckthorn is a wide ranging species, its environmental tolerances are great in terms of temperature, moisture, and substrate, and it is found in a "vast array" of plant communities [74]. In wildlands it is most common in disturbed areas [154,155], though it can establish in relatively undisturbed sites [50]. It is most commonly observed along rivers, streams [12,49,74,123,225], and ravines [209], in open woods [55,74,138,225], woodland edges [138,209,225], rocky woods [194], shrublands, hillsides, damp places, and nearly any habitat except where there is extreme shading or dryness [74]. It seems to have an affinity for disturbed, fertile, calcium-rich, open, moist areas [74], but it can tolerate both dry and partially flooded conditions [203].
Within these broad designations, common buckthorn is found most often on fertile, sunny, moist, and disturbed sites [74]. In a study of 25 fragments of riparian forest in an urban-rural gradient along the Assiniboine River in southern Manitoba, common buckthorn was most prevalent in urban and suburban sites with a high proportion of edge habitat, and it was rarely found in rural sites or reference (relatively undisturbed) forests [155]. Common buckthorn was significantly more likely to occur in urban and suburban sites (P<0.005) and was characterized as an opportunistic species and an indicator of disturbed forest; it was positively associated with disturbance measures (such as cover of garbage) and negatively associated with native and overall plant diversity [154]. Common buckthorn was found in both intact (forest, open woods, streams, wetlands) and disturbed (fields, pastures, roadsides, ditches, train tracks, urban sites) sites in forest fragment patches within and around Ottawa. It was not strongly associated with forested, agricultural, or urban landscapes [50]. Observations by Delanoy and Archibold [45] in the Saskatoon area indicate that common buckthorn density decreases with distance from the city and the South Saskatchewan River, and that it is mostly restricted to coulees and similar valley side features where colluvial deposits provide moist, yet well-drained conditions. Some of the densest common buckthorn stands in the area occur on river terraces within the city limits [45].
Wildland areas in urban settings commonly serve as fronts from which invasives can spread into other, more natural environments surrounding cities, and are therefore important places to monitor invasive species [226]. Along the Wisconsin River, increased edge habitat, higher road densities, and altered flood regimes seemed to facilitate shrub invasions, whereas unfragmented forest and intact flood regime limited invasion. Frequency and density of shrubs ≥1.6 feet (0.5 m) tall were measured in 100-year floodplain forests along 9 reaches of the Wisconsin River. Both common and glossy buckthorn were present, though common buckthorn was more frequently observed. Common and glossy buckthorn, which were not identified separately in the study results, occurred in 13% of plots and averaged 0.48 stem/m². They were more frequent and more abundant in reaches in south-central Wisconsin (an area with greater anthropogenic disturbance) than in reaches in north-central or southwestern Wisconsin (P<0.0001), and more frequent (P=0.0134) and abundant (P=0.0311) near roads [174].
Dahurian buckthorn general site characteristics: In its native range in China, Dahurian buckthorn occurs below 5,900 feet (1,800 m) in forests on slopes, forest margins, thickets, and wet places along canals [242]. According to Stephens [202], Dahurian buckthorn seldom escapes cultivation in North America except in the northern part of its nonnative range in North Dakota and, as of 1973, one location in South Dakota. It is rarely found in waste places and along roadsides in Rhode Island and Connecticut [138]. Dahurian buckthorn appears to grow well in any type of soil, especially when moist [202]; however, it may also grow well on dry soils (USDA FS 1948 as cited by [74]).
Very little additional information regarding site preferences for Dahurian buckthorn was found in the available literature as of 2010. Most of the following information applies to common buckthorn unless otherwise indicated.
Climate: Common buckthorn and Dahurian buckthorn are both described as very hardy and durable shrubs or trees. They can be grown under cultivation from USDA hardiness zone 3 (average minimum temperatures ranging from -40 to -30 °F (-40 to -34 °C)) to zone 6 (average minimum temperatures ranging from -10 to 0 °F (-23 to -18 °C)) or 7 (average minimum temperatures ranging from 0 to 10 °F (-18 to -12 °C)) [48].
In North America common buckthorn occurs in a wide range of climatic conditions [74], growing in nearly any climate except those in arid regions [202]. The climate within its primary, worldwide range of distribution is humid continental, where humid conditions occur throughout the year, summers are cool, temperatures average over 50 °F (10 °C) during at least 4 months, and the mean temperature of the warmest month is under 72 °F (22 °C). Common buckthorn seldom occurs in areas where the average January temperature falls below 0 °F (-18 °C); and most of common buckthorn's range lies within the 60 °F to 75 °F (20-24 °C) (July) isotherms [74]. However, a review by Qaderi and others [175] notes that common buckthorn populations in Canada tolerate temperature extremes from 104 °F (40 °C) (the highest temperature in Toronto) to - 53 °F (-47 °C) (the lowest temperature in Saskatoon). Stem samples of common buckthorn collected in midwinter and exposed to temperatures as low as -11 °F (-24 °C) showed 100% survival [205].
Common buckthorn tolerates a wide range of moisture conditions. Average annual precipitation in much of common buckthorn's range is between 20 and 40 inches (508-1,020 mm). The eastern portion of its native range and the western portion of its nonnative range, which includes North Dakota, Montana, Manitoba, and Saskatchewan, are drier (10-20 inches (250-510 mm) annual precipitation); and some parts within its US range are wetter, receiving 40 to 60 inches (1,020-1,500 mm) of annual rainfall [74].
In an effort to determine potential geographic extent of common buckthorn's spread in North America, Gourley [74] compared the distribution of common buckthorn outside cultivation in North America to climate, soil, and geological information in those areas. To the north, common buckthorn's range appeared to be limited by duration of temperatures too cold for flowering and seed set, possible winter-kill temperatures, and acidic soils. To the west, common buckthorn's range extends to the semiarid Great Plains and Rocky Mountains. The precise limits of common buckthorn's distribution probably involve a complex of factors [74].
In the early 1900s common buckthorn and Dahurian buckthorn were planted as potential shelterbelt species in Mandan, North Dakota, in the northern Great Plains. The test site was semiarid, with temperature extremes ranging from -63 °F to 121 °F (-53 to 49 °C), frost-free periods ranging from 89 to 161 days, and mean annual precipitation ranging from 9.39 to 24.20 inches (238.5-614.7 mm). Of 100 common buckthorn individuals planted in 1918, 100% survived 10 years and 98% survived 32 years. Common buckthorn was described as extremely cold and drought hardy, with only minor winter injury. Of 39 Dahurian buckthorn individuals planted on the site in 1929, 100% survived 1 year, and 33% survived 5 to 32 years. Dahurian buckthorn was described as cold and drought hardy, with only minor winter injury, although its stems and branches were easily broken by drifted snow [63]. Another study in the northern Great Plains reports 67.9% survival of 15 planted Dahurian buckthorn individuals after 5 years [62].
Elevation, topography, and soil depth: Few sources provide information on the elevational range of common buckthorn, and no information was available for Dahurian buckthorn (as of 2010). Common buckthorn may be an abundant shrub in disturbed settings within the eastern white pine-oak forest alliance of the northeastern United States, which occurs at elevations below 3,000 feet (915 m). In the northern glaciated portion of the range, the forest occurs on outwash plains or moraines, as well as along mid- and lower slopes and within protected ravines, and on protected ridges or upper slopes of shale, sandstone or other sedimentary rock, occasionally underlain by metamorphic or igneous rock. Along the unglaciated plateau, this community occurs on rolling topography underlain by sandstone [166]. The majority of common buckthorn at the University of Wisconsin Arboretum occurs in low-lying areas at 850 to 870 feet (260-265 m) near Lake Wingra [74]. One record reported a common buckthorn plant at 5,100 feet (1,550 m) in north-central Colorado, but it may have been cultivated [87]. In China, common buckthorn occurs in valleys and on slopes between 3,940 and 4,600 feet (1,200-1,400 m) [242]. In northern Africa it is restricted to high altitudes [71].
At the University of Wisconsin Arboretum common buckthorn is most abundant in nearly level areas and at the bases of areas with steep topography. It occurs to a limited extent in areas with 2% to 5% slope and some areas with as much as 12% slope [74]. The abundance of common buckthorn was examined at 3 locations on 3 site types (upland forests, river bluffs and ravine slopes, and floodplains) in the Thames River watershed in London, Ontario. Common buckthorn was found on all site types in each location, but was generally least abundant on upland sites [226]. In Europe common buckthorn shows a general preference for south and west slopes [71].
In the limestone woodlands at Chaumont Barrens Preserve in north-central New York, adult common buckthorn were found only on sites where soil depth exceeded 2.8 inches (7 cm), though seedlings and saplings were found at a wide range of soil depths. This suggests that common buckthorn seedlings can establish at a wide range of soil depths but cannot survive to adulthood at a soil depth less than 2.8 inches. In the calcareous pavement barrens, seedlings, saplings, and adults are found at all soil depths; one explanation for this is that the limestone bedrock contains many cracks that allow the roots of trees and shrubs to grow in seemingly little soil [188].
Soil nutrients, mineralogy, and parent material: While information on specific soil nutrient and pH preferences of common buckthorn in North America is sparse [120], several authors indicate that common buckthorn has an affinity for alkaline and calcareous soils or soils derived from limestone in both Europe and North America (e.g., [69,74,106,120,175], and there are several examples of its occurrence in such areas (e.g., [31,74,198]). Common buckthorn may have an affinity, though not a requirement, for alkaline and calcium-rich soils, and its distribution may be limited by acidic soils, deep shade, or aridity (see below) [74,131]. However, the fact that buckthorn tolerates association with conifers demonstrates some adaptability in soil requirements [74]. For example, common buckthorn is sometimes abundant in the shrub layer in disturbed settings within the eastern white pine-oak forest alliance of the northeastern United States, which occurs on acidic, nutrient-poor soils [166].
Soils under common buckthorn may have higher percentages of nitrogen and carbon, modified nitrogen mineralization rates, and modified microbial communities compared to soils without common buckthorn. See Influence on succession and plant community dynamics for more information on this topic.
Soil moisture and texture : A comprehensive review by Kurylo and others [120] indicates that soil-moisture preferences reported for common buckthorn range from dry to moist in both European and North American habitats. Some authors indicate that common buckthorn prefers moist soils in England [71], eastern Ontario [160], around Saskatoon, Saskatchewan [6], the northern Great Plains [202], west-central Minnesota [243], and the University of Wisconsin Arboretum [74,75]. Common buckthorn commonly occurs in wetland communities in the Great Lakes region (e.g., [40,52,74,133]), and it is often noted in riparian areas that experience regular spring flooding (e.g., [52,74,105,160]). Some studies have found that common buckthorn grows best on sites with high moisture availability (e.g., [74,140]). However, along the Wisconsin River, buckthorns (common and glossy combined) were more likely to occur on relatively high elevations (P=0.0446) and at distances farther from the river (P=0.0018), where flooding is less frequent [174]. Within Clark Reservation State Park in New York, common buckthorn occurs in an area with soils described as thin and drought-prone [196], and a study of common buckthorn in 28 upland, oak-dominated woodlots in southeastern Wisconsin found that common buckthorn density and importance values were highest in the more xeric bur oak communities and decreased in the more mesic sugar maple communities [131]. Site and microsite preferences may be affected by a combination of light availability, disturbance, and moisture availability (see Shade tolerance). Common buckthorn seedling densities had positive correlations with cation exchange capacity and percent clay and a negative correlation with percent organic matter and continuum index (i.e., shade) (P≤0.002). The author suggests that the bur oak savanna presents the ideal set of conditions for common buckthorn invasion and growth: relatively high light intensity and fertile, deep, humic soils [131].
In the northeastern United States, common buckthorn is classified as an upland species, suggesting that it rarely occurs in wetlands in that region. In the northern and central Great Plains, common buckthorn is classified as a facultative upland species: one that usually occurs in nonwetlands but is occasionally found in wetlands [178]. The 1996 draft revisions for wetland indicator statuses list common buckthorn as "facultative negative" in part of the Northeast Region (the Great Lakes Plain subregion of Ohio, Pennsylvania, and New York) and the whole of the North Central Region (covering Illinois, Iowa, Indiana, Michigan, Minnesota, Missouri, and Wisconsin), meaning that it is found in wetlands, but not as frequently as a facultative species [120]. Kurylo and others [120] raise some questions regarding common buckthorn based on these designations, particularly questioning whether common buckthorn populations in the northern and central Great Plains may be somehow ecologically distinct (e.g., an ecotype) from populations elsewhere within its invaded range, and whether these differences are attributable to a difference in native seed sources. For example, common buckthorn in England forms nearly monospecific stands in some fens, whereas it occurs in drier habitats in continental Europe [120].
A detailed survey at the University of Wisconsin Arboretum indicates that common buckthorn is most common and grows best on sites that are either open or moist or both [74,75] (see Shade tolerance). The greatest density of common buckthorn and the largest common buckthorn trees occurred in open-canopy wetlands in nearly level areas of deep, poorly to very poorly drained soils where the seasonal high water table is at or near the surface (<1 foot (0.3 m) deep). Common buckthorn also does well in wet and relatively shady areas. In one area with soils described as "extremely wet and mucky" and supporting the largest common buckthorn individuals found in the Arboretum (some measuring 37 inches (95 cm) in circumference), many of the large common buckthorn individuals have fallen over, suggesting that the trees may have grown too top-heavy for their shallow root system in this substrate [74]. Kurylo and others [120] cite evidence suggesting that common buckthorn may be limited by a high winter water table or more waterlogged parts of wetlands, preferring relatively drier microsites in some wetland areas. Drier soils in the Arboretum support common buckthorn growth, but to a more limited extent than wet areas. Prairie sites, which do not have common buckthorn, are drier upland areas with gently rolling or slightly irregular topography [74].
While common buckthorn often occurs on relatively wet sites, some evidence suggests that seedling establishment, growth, and frost resistance may be negatively impacted by prolonged flooding. At Chaumont Barrens Preserve in north-central New York, Samuels [188] suggested that the lack of common buckthorn seedlings, saplings, and adults in alvar grasslands may have been due to inhibition of common buckthorn seed germination by seasonal flooding. Common buckthorn occurs in both floodplain and basin forested wetlands dominated by silver maple in southeastern Wisconsin. The water table is at or near the soil surface most of the year in both site types, although basin soils always have 14 to 16 inches (35-40 cm) of standing water in spring, while floodplain soils are flooded every 2 to 3 years, usually in spring. Common buckthorn importance value (relative basal area+relative frequency+relative density) in the shrub layer was similar on floodplain sites (3.5) and basin sites (2.4). In the seedling layers, however, importance value was significantly greater on floodplain sites (17.9) than on basin sites (5.4) (P<0.05). Common buckthorn did not occur in the tree layer in either site type. Basin soils had significantly lower pH (6.5 versus 7.2), higher organic matter and higher calcium and magnesium content (P<0.0001) [52]. Common buckthorn individuals grown in a garden grew taller in well-drained (control) trenches than in trenches continuously flooded to a depth of 4 inches (10 cm) above the soil surface for 120 days [60]:
Common buckthorn height growth and diameter growth after 120 days under well-drained (control) or flooded conditions (n=20) [60] | ||||
Parameter | Initial height (cm) | Height growth (cm) |
Diameter growth (cm) |
Number surviving |
Control | 28.1 | 10.8* | 0.05 | 16 |
Flooded | 25.9 | 6.5 | 0.05 | 20 |
*Indicates a significant difference between flooded and control treatments (P=0.01). |
When young trees were assessed the following year, common buckthorn individuals from the flooded treatment had significantly less height and diameter growth compared to controls (P=0.001). Fewer common buckthorn individuals survived in the second year after flooding (~78%), although differences were not significant. Previously flooded common buckthorn individuals also seemed more susceptible to frost injury during the period of recovery [60]. In a greenhouse study, common buckthorn initially showed reduced photosynthetic rates upon exposure to partial flooding; although photosynthetic rate recovered, plants remained significantly smaller than controls [203].
Common buckthorn often occurs on soils with relatively high percentages of organic matter (e.g., [184]), but its distribution does not seem to be correlated with particular soil textural classes (e.g., [226]). In Canada, common buckthorn frequently occurs on clays or loams [175]. Field observations of 24 oak woods in northwestern Indiana, northeastern Illinois, and southern Wisconsin found common buckthorn occurred on deep silty clay loams that are not frequently subject to extreme drying [83]. Common buckthorn may be an abundant shrub in disturbed settings within the eastern white pine-oak forest alliance of the northeastern United States, which occurs on dry-mesic to mesic, sandy loam to sandy soils [166]. Buckthorns (common and glossy combined) were most frequent in sandy soils (P<0.0001) along the Wisconsin River [174].
Soil disturbance: Areas of the heaviest concentrations of common buckthorn in the University of Wisconsin Arboretum are consistently places of soil disturbance such as trail and wood edges, dredge spoil sites, clearings, areas where Bell's honeysuckle was removed, streambanks, areas of steep topography with high erosion potential, excavated areas, an area directly under and around utility lines and poles, and deer yards [74]. Where common buckthorn occurs on dry sites in the Arboretum, Gourley [74] speculated that soil disturbance may have allowed it to establish. Prairie sites without common buckthorn were less disturbed than those with common buckthorn. Lack of perches to facilitate bird dispersal of seeds and interference from prairie grasses may also contribute to the rarity of common buckthorn in prairies [74].
Common buckthorn and Dahurian buckthorn were planted at 6 surface coal mine reclamation sites in Wyoming and Colorado. Both species survived and grew at 4 of the 6 sites during the first year after planting [102]. Site data from 2 of those sites are given in the table below:
Site characteristics and growth and survival of common buckthorn and Dahurian buckthorn at 2 coal mine reclamation sites in Wyoming and Colorado. All sites were surface-mined. Shrubs were planted in spring of 1976 and measurements taken at the end of the 1977 growing season [102]. | |||||||
Site | Gillette | Glenrock | |||||
Elevation (feet) | 4,500 | 6,000 | |||||
Mean annual precipitation (mm) | 384.3 | 337.6 | |||||
Soil pH | Topsoil* | 6.9 | 6.3 | ||||
Subsoil | 6.7 | 5.2 | |||||
Soil texture | Topsoil | Clay loam | Sandy loam | ||||
Subsoil | Clay loam | Sandy loam | |||||
Electrical conductivity (mmhos/cm) |
Topsoil | 3.98 | 1.18 | ||||
Subsoil | 1.60 | 4.20 | |||||
Organic matter** (%) |
Topsoil | 4.32 | 1.25 | ||||
Subsoil | 3.30 | 2.00 | |||||
Survival and growth variables | Height (cm) |
Spread (cm) |
Survival (%) |
Height (cm) |
Spread (cm) |
Survival (%) |
|
Common buckthorn | 24 | 14 | 67 | 21 | 17 | 100 | |
Dahurian buckthorn | 32 | 14 | 67 | 35 | 23 | 100 | |
*Stockpiled or newly stripped, applied at depths of 6 to 18 inches. **Soils at coal mine sites have various amounts of coal particles, which contribute to organic matter readings. |
Data from 2 sites at Oak Creek are not included in the table because soil information is not clear. Common buckthorn had 100% survival and Dahurian buckthorn had 75% survival at both Oak Creek sites. Height and spread were about half as much for both species as at the other sites. Oak Creek sites were located at 7,500 feet (2,300 m) elevation, received 15.8 inches (401.7 mm) average annual precipitation, and soils were silt loams over clay loams, with a pH of 7.4 over 7.7, electrical conductivity of 2.00 mmhos/cm over 3.30 mmhos/cm, and organic matter of 6.5% to 3.7%. Neither common buckthorn nor Dahurian buckthorn survived at the Hanna or Kemmerer sites, which differed from other sites in terms of elevation (7,200-7,600 feet (2,200-2,300 m)), average annual precipitation (9.3-10.6 inches (235.2-270.5 mm)), and pH (7.3-8.0). Soils at the Hanna site also had the highest electrical conductivity (7.02 mmhos/cm), indicating a high salt content. Sites at Gillette and Glenrock were cultivated, while the other sites were planted and left to compete with the plants of natural succession [102]. Native vegetation at these sites is described in Habitat Types and Plant Communities: Western North America.
More info for the terms: bog, density, fresh, shrubs
Few published studies on seed banking of common buckthorn were available as of 2010. Common buckthorn seed densities under mature common buckthorn individuals or stands may range from 15 seeds/m² [45] to 5,000/m² [175]. Common buckthorn seeds may remain viable in the soil for several years. Seeds in intact fruit may be viable but dormant, so fruit remaining on branches may comprise an aerial seed bank, while fallen fruits may contribute to the soil seed bank.
Flooding and seed predation may affect common buckthorn seed bank density. Four studies report a wide range of common buckthorn seed densities in the soil seed bank under mature common buckthorn. Seed banks beneath large, 26-foot-tall (8 m), fruiting trees of common buckthorn in the Sifton Bog Conservation Area in London, Ontario, all had more than 1,000 seeds/m², and some had up to 5,000 seeds/m² (Cavers and others unpublished data cited by [175]). The buried seed bank beneath mature common buckthorn shrubs in a population near Saskatoon, Saskatchewan, averaged 620 seeds/m² in the top 4 inches (10 cm) of soil and was composed entirely of common buckthorn. Common buckthorn seedlings emerged from all soil samples collected from beneath this stand [6]. In a riparian woodland near Saskatoon, Saskatchewan, on-ground fruit counts were 124 fruits/m², and density of common buckthorn seeds in the top 4 inches of soil averaged 15 seeds/m² [45]. Common buckthorn seeds placed in water in the spring retained some viability (77% germinated after 2 weeks), but seeds became nonviable after 2 months of immersion [6]. This suggests that high water levels during spring runoff could reduce common buckthorn density in the soil seed bank. In second-growth riparian forest along Little Otter Creek in Vermont, mature common buckthorn shrubs occurred in understory plots 16 to 82 feet (5-25 m) from the stream edge. Little Otter Creek is an unregulated stream that floods into the riparian forest to distances of about 328 feet (100 m) from the stream edge each spring; the riparian forest is free of standing water by mid-June. Common buckthorn seeds were not detected in the seed rain 5 m from the stream; they occurred at a density of 16,000 seeds/ha at 15 m and at a density of 8,000 seeds/ha at 25 m. Common buckthorn seeds were not detected in the soil seed bank either 5 or 25 m from the stream edge (the seed bank was not sampled at 49 feet (15 m) from the stream edge) [105].
Common buckthorn seeds may remain viable in the soil for at least 2 years [71] and possibly as long as 6 years (Ahrens 1999 as cited by [191], management guidelines by [78]). Seeds survive the winter either in the soil seed bank or in shriveled fruits on parent plants [175]. Archibold and others [6] recorded a germination rate of 88% for fresh common buckthorn seed, which was followed by a rapid loss of viability that resulted in few seeds germinating beyond 1 year of dispersal. Miller (2005 as cited by [45]) also reported that only a small fraction of the annual common buckthorn seed crop remains viable beyond the first year. In a riparian woodland near Saskatoon, Saskatchewan, total fruit production, on-ground fruit counts, and density of seeds in the top 4 inches (10 cm) of soil were reduced after 74% of fruiting stems had been killed using 2 treatments over 6 years. In untreated versus treated plots examined 1 year after the second treatment, on-ground fruit counts were 124 fruits/m² versus 1 fruit/m², and soil seed bank densities were 15 seeds/m² versus 7 seeds/m², respectively [45]. The depletion of the seed bank implies that most common buckthorn seeds do not persist beyond the first year of dispersal. However, observations in Michigan indicated dense seedling establishment following the removal of mature common buckthorn shrubs and, after hand-pulling over 125,000 seedlings from approximately 540 feet² (50 m²), the area was soon revegetated again with common buckthorn from the disturbed seed bank and missed seedlings [214].
Under field conditions, common buckthorn seeds inside intact fruits may remain viable longer than seed separated from fruits. Common buckthorn fruits were collected from trees in London, Ontario, in early April 1993. Whole undamaged fruits and washed separated seeds were placed in artificial soil in a greenhouse. The separated seeds germinated quickly with up to 80% producing seedlings in 3 weeks, but seeds in whole fruits germinated slowly and intermittently over a 5-month period (Cavers and Thomas unpublished data cited by [175]). In some years, dried fruits remained on common buckthorn trees for a year or more, and the seeds inside them remained viable. This aerial seed bank included seeds that eventually germinated more than 1.5 years after they were produced [175]. Archibold and others [6] suggested that under field conditions the rotting of common buckthorn fruit may delay germination until spring. Seeds extracted and dried to a moisture content of about 10% showed high germination and emergence rates after storage at 27 °F (-3 °C) for 3.5 years [215].