Arboriculture & Urban Forestry 34(4): July 2008 Table 1. Species importance values (IV) in percentages for the 1935 and the 2005 census.z (continued ) Dominance rank 3. Prunus spp. N 3 4. Acer spp. 5. Robinia pseudoacacia Dry Ridge, 2005 1. Quercus rubra 2. Quercus velutina 3. Quercus alba 4. Prunus serotina 5. Quercus prinus 6. Liriodendron tulipifera 7. Quercus coccinea 8. Betula lenta 9. Morus alba 10. Tilia cordata 11. Aesculus hippocastanum 12. Robinia pseudoacacia 13. Fraxinus americana 14. Carya cordiformis 15. Populus deltoides 16. Prunus avium IV is the sum of relative density, relative frequency, and relative dominance. In the 1935 census, some taxa were identified only to genus. Integers denote the ecologic dominance rank of each species as measured by the IV method. z Loeb (1982) questioned the reliability of the New York City Department of Parks and Recreation’s (NYCDPR) forest re- cords. Loeb (1982) compared three tree map studies: the NYC- DPR’s topographic map series at Seton Falls Park in northern Bronx using forest records prepared in 1936 by the NYCDPR, his personal research in 1979, and a tree map prepared by Quinn Associates, Philadelphia, Pennsylvania, in 1981. Loeb surveyed a 5 ha (12.5 ac) portion of Seton Falls Park Forest and concluded that there were errors in identifications, tree diameter measure- ments, and “oversights in recording of species on the maps of the park.” Loeb (1982) concluded, “Totally accurate arboreal spe- Table 2. Density per ha of saplings (trees of diameter at breast height less than 7.6 cm [3 in]) at three sites in 2005, Inwood Park, New York. Species Morus alba Acer platanoides Fraxinus spp. Acer saccharum Carya cordiformis Liriodendron tulipifera Quercus alba Celtis occidentalis Quercus prinus Tilia cordata Prunus serotina Quercus rubra Sassafras albidum Prunus avium Betula lenta Acer rubrum Crataegus spp. Pyrus calleryana Pyrus malus Moist Valley South Slope Dry Ridge 350 200 250 400 100 150 150 50 100 50 150 50 100 100 50 3500 450 450 250 850 50 50 400 50 700 100 350 150 50 250 50 350 100 350 250 cies lists cannot be made from these records because some minor groups of species may not be included and misidentifications can cause the inclusion of species that were not present. Reliable statements of population density and dominance changes can only be made for dominant taxa.” To address Loeb’s concerns in this study, all species of oaks (Quercus) and all species of maples (Acer) were lumped as genera when comparing across years, so that past species misidentifications would not be an issue. The trees identified within each quadrat in 2005 in the three sites mentioned were compared with trees identified within the same quadrats at the same sites located on the WPA map (City of New York, Department of Parks, Topographical Division 1935). Density (percent of total trees), frequency (percent of all points of occurrence across quadrats), relative dominance (per- cent total basal area), and importance value (IV, sum of relative density, relative frequency, and relative dominance) were calcu- lated for all arborescent species in 1935 and 2005. Tree species were listed in decreasing order of IV (Kent and Coker 1992). Change in tree size (dbh) was subjected to two-way analysis of variance with date (1935, 2005), the three study sites, and the interaction term as effects (Sokal and Rohlf 1995). Shannon diversity (Pielou 1975) was calculated for the arborescent taxa in each study site for 1935 and 2005. Data were merged from the 1935 and 2005 census and correspondence analysis (Manly 2006) was used to ordinate the three study sites and the nine most dominant genera of trees. Saplings (dbh less than 7.6 cm [3 in]) were sampled in 25 2 m × 4 m (6.6 ft × 13.2 ft) quadrants placed in the lower right corner of each 10 m × 10 m (33 ft × 33 ft) quadrant in 2005. No sapling data are available for 1935. Nomenclature follows Gleason and Cronquist (1991). RESULTS AND DISCUSSION At the Moist Valley in 1935 and in 2005, tulip poplar (Lirioden- dron tulipifera), red oak (Quercus rubra), and sugar maple (Acer ©2008 International Society of Arboriculture 1 1 43 7 7 11 8 7 3 3 3 2 1 1 1 1 1 1 Relative density 7.5 (95.0) 2.5 (97.5) 2.5 (100) 43.0 (43.0) 7.0 (50.0) 7.0 (57.0) 11.0 (68.0) 8.0 (76.0) 7.0 (83.0) 3.0 (86.0) 3.0 (89.0) 3.0 (92.0) 2.0 (94.0) 1.0 (95.0) 1.0 (96.0) 1.0 (97.0) 1.0 (98.0) 1.0 (99.0) 1.0 (10.0) Relative frequency 11.5 (92.3) 3.9 (96.2) 3.9 (100) 28.4 (28.4) 9.0 (37.3) 9.0 (46.3) 14.9 (61.2) 10.5 (71.6) 4.5 (76.1) 4.5 (80.6) 4.5 (85.1) 4.5 (89.6) 1.5 (91.0) 1.5 (92.5) 1.5 (94.0) 1.5 (95.5) 1.5 (97.0) 1.5 (98.5) 1.5 (100) Relative dominance 1.5 (98.2) 1.2 (99.5) 0.5 (100) 47.0 (47.0) 13.2 (60.2) 11.8 (72.0) 1.4 (73.4) 4.9 (78.2) 11.1 (89.4) 3.6 (92.9) 2.5 (95.5) 0.5 (95.9) 1.0 (96.9) 1.3 (98.2) 0.8 (98.9) 0.7 (99.6) 0.2 (99.8) 0.2 (100) 0.02 (100) 247 Importance value 20.5 (285.54) 7.6 (293.11) 6.9 (300.00) 118.4 (118.37) 29.2 (147.52) 27.8 (175.30) 27.3 (202.58) 23.3 (225.88) 22.6 (248.48) 11.1 (259.53) 10.0 (269.53) 7.9 (277.47) 4.5 (281.93) 3.8 (285.71) 3.3 (288.98) 3.2 (292.16) 2.7 (294.82) 2.7 (297.48) 2.5 (300.00)
July 2008
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