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''Celastrus orbiculatus'' is a woody vine of the family
Celastraceae The Celastraceae (staff-vine or bittersweet) are a family of 97 genera and 1,350 species of herbs, vines, shrubs and small trees, belonging to the order Celastrales. The great majority of the genera are tropical, with only ''Celastrus'' (the sta ...
. It is commonly called Oriental bittersweet, as well as Chinese bittersweet, Asian bittersweet, round-leaved bittersweet, and Asiatic bittersweet. It is native to China, where it is the most widely distributed ''Celastrus'' species, and to Japan and Korea. It was introduced into
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...
in 1879, and is considered to be an
invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species adv ...
in eastern North America. It closely resembles the native North American species, ''
Celastrus scandens ''Celastrus scandens'', commonly called American bittersweet or bittersweet, is a species of ''Celastrus'' that blooms mostly in June and is commonly found on rich, well-drained soils of woodlands. It is a sturdy perennial vine that may have tw ...
'', with which it will readily hybridize.


Description

The defining characteristic of the plant is its vines: they are thin, spindly, and have silver to reddish brown bark. They are generally between in diameter. However, if growth is not disturbed, vines can exceed and when cut, will show age rings that can exceed 20 years. When ''Celastrus orbiculatus'' grows by itself, it forms thickets; when it is near a tree the vines twist themselves around the trunk as high as 40 feet. The encircling vines have been known to strangle the host tree to death or break branches from the excess weight, which is also true of the slower-growing American species, ''C. scandens''. The leaves are round and glossy, long, have toothed margins and grow in alternate patterns along the vines. Small green flowers produce distinctive red seeds which are encased in yellow pods that break open during autumn. All parts of the plant are poisonous.


Range and habitat

Due to systematic disturbances to eastern forests for wood production and recreation, Oriental bittersweet has naturalized to landscapes, roadsides, and woodlands of eastern North America. In the United States it can be found as far south as Louisiana, as far north as Maine, and as far west as the Rocky Mountains. It prefers mesic woods, where it has been known to eclipse native plants.


Cultivation

''Celastrus orbiculatus'' is cultivated as an ornamental plant. In the UK it has gained the
Royal Horticultural Society The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening charity. The RHS promotes horticulture through its five gardens at Wisley (Surrey), Hyde Hall (Essex), Harlow Carr (Nor ...
's
Award of Garden Merit The Award of Garden Merit (AGM) is a long-established annual award for plants by the British Royal Horticultural Society (RHS). It is based on assessment of the plants' performance under UK growing conditions. History The Award of Garden Merit ...
.


''Celastrus orbiculatus'' as an invasive species

Oriental bittersweet is a strong
competitor Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indivi ...
in its environment, and its dispersal has endangered the survival of several other species. One attribute that contributes to the success of this species is having attractively colored fruit. As a result, it is eaten by mammals and birds, which excrete the seeds to different locations. The introduction of Oriental bittersweet into new areas threatens the local flora because the native plants then have a strong competitor in the vicinity. The species is native to Eastern Asia, but was introduced to the US for aesthetic purposes. It has been used in floral arrangements, and because of improper disposal the plant has been recklessly introduced into areas, affecting the ecology of over 33 states from
Georgia Georgia most commonly refers to: * Georgia (country), a country in the Caucasus region of Eurasia * Georgia (U.S. state), a state in the Southeast United States Georgia may also refer to: Places Historical states and entities * Related to the ...
to
Wisconsin Wisconsin () is a state in the upper Midwestern United States. Wisconsin is the 25th-largest state by total area and the 20th-most populous. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake M ...
, and parts of the Appalachians. The organism grows primarily in the perimeter of highly vegetative areas, allowing it to readily access the frontier of resources. Oriental bittersweet's ability to grow in a variety of environments has proven to be detrimental to many plant species along the Appalachian mountains and is moving more towards the West as time progresses. Oriental bittersweet employs multiple invasive and dispersal strategies allowing it to outcompete the surrounding plant species in non-native regions. This is a strong reason why the control of the species presents difficulties to manage. The plant's invasion has created diverse ecological, managerial, and agricultural complications making it a focus of
environmental conservation *Environmental protection *Nature conservation Nature conservation is the moral philosophy and conservation movement focused on protecting species from extinction, maintaining and restoring habitats, enhancing ecosystem services, and protec ...
efforts.


Response to abiotic factors

Oriental bittersweet can be found growing in areas that are high and steep. When placed in 10 different sites with varying light intensity and
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
concentration, Oriental bittersweet was found to have higher aboveground
biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bio ...
as well as a lower
mortality rate Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of d ...
in comparison to its congener species, ''
Celastrus scandens ''Celastrus scandens'', commonly called American bittersweet or bittersweet, is a species of ''Celastrus'' that blooms mostly in June and is commonly found on rich, well-drained soils of woodlands. It is a sturdy perennial vine that may have tw ...
'' (American bittersweet). This species is able to outcompete other species by more effectively responding to
abiotic In biology and ecology, abiotic components or abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Abiotic factors and the phenomena associated with them under ...
conditions such as sunlight. In diverse abiotic conditions (such as varying sunlight intensity and nitrogen concentrations), Oriental bittersweet has a mortality rate of 14% in comparison to the American bittersweet, which has a mortality rate of 33%. Oriental bittersweet cannot thrive as efficiently when placed in extremely wet and dry environments; however, it flourishes in moderate rainfall environments which leads to an increased growth rate. Sunlight is one of the most vital resources for Oriental bittersweet. As demonstrated by controlled experiments, Oriental bittersweet grows more rapidly in environments that fare a higher amount of sunlight. In a study where populations received above 28% sunlight, it exhibited a higher amount of growth and biomass. This study used layers of woven cloth to control the percentage of available sunlight. In this experiment, the TLL ratio (the living length of stems on each plant) increased when Oriental bittersweet was exposed to higher amounts of sunlight. If Oriental bittersweet was exposed to 2% sunlight, then the TLL ratio decreased. Oriental bittersweet can increase in biomass by 20% when exposed to 28% sunlight rather than 2%. The plant's strong response to sunlight parallels its role as an invasive species, as it can outcompete other species by fighting for and receiving more sunlight. Although growth ratios decrease when Oriental bittersweet is exposed to 2% sunlight (due to a decrease in
photosynthetic Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...
ability), it still exhibited a 90% survival rate. Experimental data has indicated that Oriental bittersweet has a strong ability to tolerate low light conditions “ranging on average from 0.8 to 6.4%
transmittance Transmittance of the surface of a material is its effectiveness in transmitting radiant energy. It is the fraction of incident electromagnetic power that is transmitted through a sample, in contrast to the transmission coefficient, which is t ...
”. In comparison to its congener American bittersweet, when placed in habitats with little light, Oriental bittersweet was found to have increased height, increased aboveground biomass, and increased total leaf mass. Oriental bittersweet, in comparison to many other competing species, is the better competitor in attaining sunlight. Temperature is another variable that plays a role in Oriental bittersweet's growth and development as an invasive species. Unlike other invasive species, high summer temperatures have been shown to inhibit plant growth. Oriental bittersweet has also been shown to be positively favored in habitats experiencing high annual precipitation. This is noteworthy as it contrasts sharply with other common invasive species such as '' Berberis thunbergii'' and ''
Euonymus alatus ''Euonymus alatus'', known variously as winged spindle, winged euonymus, or burning bush, is a species of flowering plant in the family Celastraceae, native to central and northern China, Japan, and Korea. The common name "burning bush" comes fr ...
'' which have been shown to have a decreased probability of establishment when placed in environments experiencing high annual precipitation. Compared to other invasive species analyzed in a recent study, Oriental bittersweet was more prevalent in landscapes dominated by developed areas. Open and abandoned habitats were also found to positively influence the spread of the plant compared to other invasive species. Additionally the species is heavily favored in edge habitats. This ability to live in various environmental conditions raises the concern of the plant's dispersal.


Biotic interactions


Mutualistic interactions

A determining factor regarding Oriental bittersweet's ability to outcompete native plant species is its ability to form mutualistic associations with
mycorrhizal fungi   A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the pla ...
, specifically
arbuscular mycorrhizal fungi An arbuscular mycorrhiza (AM) (plural ''mycorrhizae'', a.k.a. ''endomycorrhiza'') is a type of mycorrhiza in which the symbiont fungus (''AM fungi'', or AMF) penetrates the cortical cells of the roots of a vascular plant forming arbuscule ...
. Oriental bittersweet growth is highly dependent on the absorption of
phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ea ...
. In a recent study, growth was found to be greater when arbuscular mycorrhizal fungi were present in soil with low phosphorus concentrations, compared to when the plant was placed in an environment with high soil phosphorus concentrations with no arbuscular mycorrhizal fungi were present. The results from this study show the importance of
symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or para ...
relationships in allowing Oriental bittersweet to effectively uptake nutrients from its surroundings. Additionally, the symbiotic relationship with mycorrhizae allows this invasive species to utilize less of its energy in root biomass to absorb necessary nutrients. This may be crucial in allowing Oriental bittersweet to act as an effective invasive species as it is able to allocate more energy to its aboveground biomass instead of its belowground biomass; a significant point regarding this plant's invasiveness relies on photosynthetic ability and reproductive capacity. The symbiotic relationship established with fungi only occurs with arbuscular mycorrhizal fungi, while no such relationship has been observed with
ectomycorrhizal An ectomycorrhiza (from Greek ἐκτός ', "outside", μύκης ', "fungus", and ῥίζα ', "root"; pl. ectomycorrhizas or ectomycorrhizae, abbreviated EcM) is a form of symbiotic relationship that occurs between a fungal symbiont, or my ...
fungi. These studies have shown that suitable mycorrhizae are a strong determining factor regarding whether a plant can survive in its environment. Studies have also shown evidence that “introduced plant species can modify
microbial A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
communities in the soil surrounding not only their own roots, but also the roots of neighboring plants, thereby altering competitive interactions among the plant species”. This may be a key invasive trait for Oriental bittersweet, as it allows the plant to negatively affect surrounding plant life by altering their underground symbiotic microbial relationships. However, further experimentation is necessary to determine whether this organism employs this trait as an invasive strategy.


Competitive interactions

One of Oriental bittersweet's invasive characteristics is its effective utilization of energy to increase plant height, thus giving it a competitive advantage over similar plants. A study conducted in 2006 showed that, in comparison to its congener American bittersweet, Oriental bittersweet had increased height, increased aboveground biomass, and increased total leaf mass. This is not to say that Oriental bittersweet outperformed American bittersweet in all criteria: in comparison to Oriental bittersweet, “American bittersweet had increased stem diameter, single leaf area, and leaf mass to stem mass ratio,” suggestive that American bittersweet focused growth on ulterior portions of the plant rather than plant characteristics emphasized by Oriental bittersweet such as stem length. This is significant as height plays a major role in allowing Oriental bittersweet to outcompete surrounding vegetation. Focusing growth on stem length allows it to be in a strong position to absorb light, while also negatively impacting surrounding plant life by creating shade-like conditions. The species' vine-like morphology has also been shown to have negative effects on surrounding plant life. For example, evidence suggests that this morphological characteristic facilitates its ability to
girdle A belt, especially if a cord or rope, is called a girdle if it is worn as part of Christian liturgical vestments, or in certain historical, literary or sports contexts. Girdles are used to close a cassock in Christian denominations, including th ...
nearby trees, creating an overall negative effect on the trees such as making them more susceptible to ice damage or damaging branches due to the weight of the plant. Additionally, studies have suggested that Oriental bittersweet is capable of siphoning away nutrients from surrounding plants. The study found this to occur in a variety of environments, suggestive of both the plant's increased relative plasticity as well as increased nutrient uptake. One study observed that the presence of Oriental bittersweet increases the alkalinity of the surrounding soil, a characteristic of many successful invasive plant species. This alters the availability of essential nutrients and hinders the nutrient uptake ability of native plants. Though the relationship between Oriental bittersweet and the alkalinity of the soil is consistent, there are a number of proposed mechanisms for this observation. The plant's significant above-ground biomass demands the preferential uptake of
nitrate Nitrate is a polyatomic ion with the chemical formula . Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are soluble in water. An example of an insolu ...
over
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous ...
, leading to soil
nitrification ''Nitrification'' is the biological oxidation of ammonia to nitrite followed by the oxidation of the nitrite to nitrate occurring through separate organisms or direct ammonia oxidation to nitrate in comammox bacteria. The transformation of ...
. It also has a high
cation-exchange capacity Cation-exchange capacity (CEC) is a measure of how many cations can be retained on soil particle surfaces. Negative charges on the surfaces of soil particles bind positively-charged atoms or molecules (cations), but allow these to exchange with ot ...
, which also supports the larger biomass. Either of these functions could explain the increased alkalinity, but further experimentation is needed to pinpoint the exact mechanism.


Hybridization

Another major threat posed by Oriental bittersweet is
hybridization Hybridization (or hybridisation) may refer to: *Hybridization (biology), the process of combining different varieties of organisms to create a hybrid *Orbital hybridization, in chemistry, the mixing of atomic orbitals into new hybrid orbitals *Nu ...
with American bittersweet. Hybridization occurs readily between American bittersweet females and Oriental bittersweet males, though the opposite is known to occur to a lesser extent. The resulting hybrid species is fully capable of reproduction. In theory, if the Oriental bittersweet invasion continues to worsen, widespread hybridization could genetically disrupt the entire American bittersweet population, possibly rendering it extinct.


Management

To minimize the effects of Oriental bittersweet's invasion into North American habitats, its growth and dispersal must be tightly managed. Early detection is essential for successful conservation efforts. To reduce further growth and dispersal, above-ground vegetation is cut and any foliage is sprayed with
triclopyr Triclopyr (3,5,6-trichloro-2-pyridinyloxyacetic acid) is an organic compound in the pyridine group that is used as a systemic foliar herbicide and fungicide. Uses Triclopyr is used to control broadleaf weeds while leaving grasses and conifers ...
, a common
herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page f ...
.
Glyphosate Glyphosate (IUPAC name: ''N''-(phosphonomethyl)glycine) is a broad-spectrum systemic herbicide and crop desiccant. It is an organophosphorus compound, specifically a phosphonate, which acts by inhibiting the plant enzyme 5-enolpyruvylshik ...
is another chemical method of control. These two herbicides are usually sprayed directly on the plants in late fall to prevent other plants from being targeted. These steps must be repeated annually, or whenever regrowth is observed. Triclopyr is non-toxic to most animal and insect species and slightly toxic to some species of fish, but it has a half-life of less than a day in water, making it safe and effective for field use. Mechanical methods have also been used, but they are not as effective due to the difficulty of completely removing the root. There is also no biological control agent available in helping control this species. Mechanical and chemical methods are being used, but they are only temporarily fixing the situation.


Phytochemicals

Bicelaphanol A is a neuroprotective dimeric-trinorditerpene isolated from the bark of ''Celastrus orbiculatus''.


Uses

Despite the modest toxicity of its fruit, some livestock browse on the leaves without effect. Its vines, which are durable and tough, are a good source of weaving material for baskets. The fibrous inner bark can be used to make strong cordage.


References


External links


Species Profile - Oriental Bittersweet (''Celastrus orbiculatus'')
National Invasive Species Information Center,
United States National Agricultural Library The United States National Agricultural Library (NAL) is one of the world's largest agricultural research libraries, and serves as a national library of the United States and as the library of the United States Department of Agriculture. Located ...
. Lists general information and resources for Oriental Bittersweet. {{Taxonbar, from=Q259033 Celastraceae