Jg. Ehrenfeld, INVASION OF DECIDUOUS FOREST PRESERVES IN THE NEW-YORK METROPOLITAN REGION BY JAPANESE BARBERRY (BERBERIS-THUNBERGII DC), Journal of the torrey botanical society, 124(2), 1997, pp. 210-215
Japanese barberry has become a common component of understory vegetati
on in deciduous forests throughout central and northern New Jersey and
adjacent areas of Pennsylvania and New York. A survey was carried out
by soliciting data from the public concerning the occurrence of the p
lant in forest preserves in the New York metropolitan region. The resu
lting information showed that this exotic species is present within th
e forest interior in at least 43 protected forest areas. In the majori
ty of these areas, the species occurs in extensive patches of moderate
to very high density. Although known to some resource managers, the s
pread of this exotic species into intact forest has not previously bee
n reported. The widespread growth of B. thunbergii may threaten the ab
ility of small to moderate-sized forest reserves to serve as a refuge
for native plant species.