Skaneateles Conservation Area/Invasive species/Berberis

<< Prohibited invasive plants at the SCA

There are two barberry (Berberis) species known to be present at the Skaneateles Conservation Area (SCA):
 * Berberis thunbergii (Japanese barberry), by far the most prevalent, prohibited in New York and listed as very highly invasive
 * Berberis vulgaris (common barberry) is much less common at the SCA and listed as moderately invasive.
 * Berberis × ottawensis (Ottawa barberry) is a hybrid of the two but not known to be present in the area.

Berberis thunbergii (Japanese barberry)
Japanese barberry (Berberis thunbergii) is a deciduous shrub that can grow up to 8 feet tall, native to Japan. It can invade open and semi-open areas such as light gaps in forests, forest edges, meadows, and disturbed areas. Large infestations have been implicated in a large increase in ticks that transmit Lyme disease, possibly because they are ideal habitat for white-footed mice, which carry Borrelia burgdorferi, the spirochete bacterium that causes Lyme disease, and provide the first blood meals for blacklegged (deer) ticks, which often transmit the disease to humans.

Invasiveness ranking for Berberis thunbergii (Japanese barberry)
The New York State ranking for Berberis thunbergii, assessed in 2008, included all hybrids with other Berberis species. The relative maximum score was 91%, giving it an invasiveness rank of Very Highly Invasive.

Berberis thunbergii is prohibited by New York State law, however, according to the DEC website, the following cultivars meet the exemption qualifications of 575.8 (a)(4) and are Conditionally Exempt:
 * Berberis thunbergii 'Aurea'
 * Berberis thunbergii 'UCONNBTCP4N' Crimson Cutie&trade;
 * Berberis thunbergii 'UCONNBTB113' Lemon Cutie&trade;
 * Berberis thunbergii 'UCONNBTB048' Lemon Glow&trade;

Ecological impact (37/40)
Major, possibly irreversible, alteration or disruption of ecosystem processes (10/10):


 * Soil under Berberis thunbergii has higher pH, higher nitrification rates (conversion of ammonium to nitrate), and often higher N mineralization rates than soil under native shrubs.


 * Barberry litter is higher in N, and decomposes more rapidly (with little N immobilization), than native plant litter. These changes may lead to a positive feedback loop in which barberry increases the rate of nitrate production, which it preferentially takes up to support rapid growth and high biomass production.


 * May facilitate non-native earthworm increases, which also alters soil chemistry and function.

Significant impact in at least one layer (7/10):


 * Has been shown to significantly increase the shrub layer density and may invade areas where there is not currently a shrub layer, thus creating a new layer, possibly eliminating layers below it.

Major alteration in community composition (10/10):


 * Altered soil pH, N concentrations and N cycling increases the likelihood of additional exotic invasions, which tend to prefer soils with higher pH and nutrient availability.


 * Replaces the understory Vaccinium layers.


 * Since barberry is not a preferred deer food, deer browse pressure is increased on native plants which may prevent their recruitment.

Severe impact on other species or species groups (10/10):


 * Causes "profound effects on the microbial community of the soil" which include altered microbial community structure and function (Kourtev et al. 2002).


 * Also alters earthworm fauna.


 * Possesses spines which decrease palatability to deer (Rawinski unpub).

Biological characteristics and dispersal ability (22/25)
Abundant reproduction (4/4):


 * A single plant can produce 2000 or more fruits (each fruit is one to few-seeded) per year, although some cultivars produce much less fruit and seed.


 * Viability is high for the species but lower for some cultivars.


 * One year old seedling of some cultivars also reported to have reduced growth vigor.


 * Spreads vegetatively through horizontal branches that root freely when they touch the ground.

Numerous opportunities for long-distance dispersal (4/4):


 * Fruits are eaten by birds, small mammals and wild turkeys and transported long distances by this means.


 * The shrub is propagated by seed widely dispersed by birds. A rise in populations of the ruffed grouse and turkey, due in part to the regrowth of second generation forest, may have much to do with the dispersal of barberry seed.
 * Most seedlings are found beneath existing plants, with some found tens of meters away from nearest adult, but this is not direct evidence that there is not long-distance dispersal.

High potential for human dispersal (3/3):


 * Was commercially sold at assessment date, but now prohibited in New York State, with the exception of the cultivars listed above.


 * Can be transported indirectly through brush removal. [Particular relevance at SCA due to transfer station location.]


 * Some of the commonly grown purple- and yellow-leaf types readily produce green-leaf offspring resembling the wild type barberry, although the percentage of green-leaf offspring varied widely by genotype.

Possesses two or more characteristics that increase competitive advantage (6/6):

Invasiveness of Berberis thunbergii at the SCA
Although Japanese barberry is quite common at the Skaneateles Conservation Area, it does not appear to be one of our most prevalent invasive plants at this time. However, it is a huge problem in the more southeastern part of New York and might be expected to become more of a problem in this area due to climate change and other factors. The Invasiveness ranking system for non-native plants of New York (2008) gave Japanese barberry a relative maximum score of 91%, the third highest of SCA plants that we know of.