250 Stalter and Kincaid: 70-Year History of Arborescent Vegetation Figure 2. Interaction graph of mean diameter at breast height (dbh) for the three sites comparing the 1935 with the 2004 to 2005 census of Inwood Park, New York. In two-way analysis of variance, interaction F2,353 = 0.24, P = 0.78. Mean dbh has increased in parallel fashion at each site. Moist Valley site. Neither of these two taxa were present at Moist Valley in 1935. Glaeser and Kincaid (2005) report a recent outbreak of a nonnative invasive tree, amur cork (Phellodendron amurense), in the forests of Queens County of New York City. This species ranked third in overall dominance and second in relative abundance in a 0.5 ha study plot in Forest Park, Queens (Glaeser and Kincaid 2005). The situation at Inwood Park bears monitoring because P. amurense, a hardy urban tree, has been planted throughout the five boroughs of New York City. Park personnel planted trees in Inwood Park from 1991 to Fall 2005 (Table 4). Only the numbers from Fall 2004 to Fall 2005 are presented in Table 4. Over 18,000 trees of 20 species were planted across approximately 33% of the area of the park during this 14 year period. Over 90% of the plantings have survived (Richard Love, pers. comm.). In two-way analysis of variance (ANOVA) (Table 5), mean dbh was significantly different between the 1935 and the 2005 census (32.3 cm [12.9 in] versus 41.8 cm [16.7 in], respectively; F1,3528.19, P0.0045), although census date explained only 2.2% of the variation in dbh (R2). Among the three study sites, Table 6. Shannon diversity and simple species diversity for trees at Inwood Park, New York, in 1935 and in 2005. Year 1935 Simple diversity Shannon diversity 2005z Simple diversity Shannon diversity 2005 Simple diversity Shannon diversity z 13 2.253 14 2.317 16 2.036 The 2005 site reflects species merged into genera (i.e., Acer, Quercus, Prunus) corresponding to the 1935 census. ©2008 International Society of Arboriculture 11 2.101 11 2.102 11 1.222 Moist Valley 10 1.976 South Slope 12 1.976 Dry Ridge 5 0.807 Figure 3. Correspondence analysis ordinating the three sites and the nine most dominant genera of trees. Data merged from the 1935 and 2004 to 2005 census. The rays indicate the direction and distance from the origin of the three sites as ordinated by generic composition (Anonymous 2007). mean dbh was not significantly different (F2,352 2.92, P 0.056). The census date × study site interaction in ANOVA was not significant (F2,352 0.24, P 0.8), which supports the visualization in Figure 2 that the three sites experienced a par- allel pattern of increase in tree size from the 1935 to the 2005 census. The correspondence analysis (CA) of Figure 3 displays the significant separation (P < 0.0001) of Dry Ridge, South Slope, and Moist Valley on the basis of the presence and abundance of the nine most dominant tree genera for the merged 1935 and 2005 census. The community data from 1935 and 2005 were merged because of their similarity. CA graphs generated for the 1935 data and independently for 2005 were nearly indistinguish- able. In the CA ordination of genera, Quercus was the most com- mon of the nine genera of trees at Dry Ridge. Prunus, a succes- sional species, is more common at Dry Ridge than at the other sites. Betula was the most evenly distributed taxon across the sites as seen by its location at the origin of the CA graph. Liri- odendron was most common at South Slope and Moist Valley. The three genera clustered at South Slope were Carya, Cornus, and Sassafras. Sassafras was found only at South Slope. Cornus, a subcanopy species, favors South Slope, was present at Moist Valley, and absent at Dry Ridge. Carya, a climax species, oc- curred at all three sites, but was most common at South Slope. Acer was common at Moist Valley and South Slope but was represented by a single tree at Dry Ridge. Fraxinus was found at all three sites but was most common in Moist Valley. Shannon diversity and simple species diversity for trees has increased slightly since the 1935 census, although less so when the 2005 data are merged into genera to conform to the 1935 census (Table 6).
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