Vol. 51—1997 - NorthEastern Weed Science Society

75
EXOTIC URBAN ARBO SCENT VEGETATION AT HOME SITES. NEW YORK CITY, NEW YORK
Richard Stalter'
ABSTRACT
Trees found at fo home sites, Jamaica Estates, New York City, New York. were selected for study October 15 to
November 7. 1995. Trees with a DBH (diameter at breast height) greater than 7.6 em were identified and mapped at each
property. Density, relativ density, frequency. relative frequency, basal area, relative dominance and importance values for all
trees with a DBH greater an 7.6 em were calculated. Black oak (Quercus velutina) and red oak (Quercus rubra) ranked first
and second in relative do inance and importance; oaks (Quercus spp.) collectively have a relative dominance value of 81.
Seventy percent of the no -native species occur in the smallest size class category (7.5 25.0 em), while oaks are most abundant
in the three largest size cl ss categories. The transition to a forest of non-native species may be a very gradual process because of
the longevity of oaks.
INTRODUCTION
The objective of he present study is determining exotic urban tree diversity by mapping, identifying and measuring
DBH (diameter at breast eight) of trees at forty home sites at Jamaica Estates. New York City, New York (40 4TN Latitude. 73
38'W Longitude). This s dy is the first of its kind in the northeastern United States. Jamaica Estates, the site where this study
was conducted, lies on th end of the Harbor Hill Moraine, and exhibits a knob and kettle topography.' The glacial till is 3 m. to
6 m. deep and is underlai with coarse sand and gravel. The soils at the home sites are classified as Miami Stony Loam. The
upper layer of soil. exren . g from the surface depth of 20-35 em, is brown loam. Yellow loam forms the subsoil at a depth of
76 em .11
MEmODS
The forty home ires selected for study October 15 to November 7, 1995, are located at Jamaica Estates, Queens
County. New York. Crit 'a used in selecting homes for study include the owners' permission and presence of mature trees when
the homes were construct d. 1929 to 1953. Trees growing at the home sites were mapped. and the DBH of each tree was
recorded. Only trees wit a DBH greater than 7,6 em were sampled. Tree DBH wasconverted to basal area.
Density (averag number of trees per quadrat), relative density (percent density), frequency (percent quadrats occupied
by each species), relative equency and relative dominance (percent basal area). and importance value (the sum of the relative
density. relative frequenc and relative dominance) were calculated for all trees found at the home sites. Since native trees far
outnumbered introduced lanted) non-native trees. separate tables for native trees (Table 1), native planted trees. and non-native
planted trees (Table 2) w re recorded.
RESULTS
=~:o< velutina) is the most abundant tree at the home sites with the highest relative dominance value and
importance value (Table ). Red oak (Quercus rubra) ranks second in relative dominance and importance. and third in
abundance. Dogwood (C rnus florida) ranks second in abundance, and third in importance, but because of its small size has a
relative dominance value f 2.1. Most of the dogwood at the home sites has been planted. Black
]Dept. of Biological Scie ces, St. John's University. Jamaica, NY 11439