Non-native urban arborescent vegetation at home sites, New York City, New York

摘要

Trees found at forty 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 cm were identified and mapped at each property. Density, relative density, frequency, relative frequency, basal area, relative dominance and importance values for all trees with a DBH greater han 7.6 cm were calculated. Black oak (Quercus velutina) and red oak (Quercus rubra) ranked first and second in relative dominance and imortance; oaks (Quercus spp.0 collectively have a relatvei dominance value of 81. Oaks are most numerous in the largest three size classes, (51 to 75 cm, 76 to 100 cm and greater than 100 cm) but comprise a small percentage of the two smaller size classes (7.5 to 25 cm, 26 to 50 cm) which presumably contain the youngest trees. Non-native trees make up seventy percent of the smallest size class category and native trees other than oaks are more numerous than oaks in the smallest two size class categories. The transition to a forest of non-native species may be a very gradual process because of the longevity of oaks.