ARBORICULTURE ARBORICULTU URBAN FORESTRY Volume 31, Issue 1, January 2005 & CONTENTS Variety Selection. Glynn C. Percival and S. Barnes THE INFLUENCE OF CALCIUM AND NITROGEN FERTILIZATION ON THE FREEZING AND SALINITY TOLERANCE OF TWO URBAN TREE SPECIES ............................................. 10 Abstract. Two field trials were undertaken to determine the influence of fall fertilization using two commercially available, calcium-based fertiliz- ers (calcium nitrate, calcium nitrate borate) and a high-nitrogen fertilizer (N:P:K = 24:7:7), at a range of concentrations, on the freezing and salinity tolerance of two urban tree species, evergreen oak (Quercus ilex) and holly (Ilex aquifolium). In both the 2001 and 2002 field trials, fertilization with calcium nitrate and calcium nitrate borate at a concentration of 40 g/m2 (0.12 oz/ſt2 ) increased the freezing and salinity tolerance of both species as measured by leaf chlorophyll fluorescence, electrolyte leakage, and chlorophyll content. In addition, calcium fertilization at this concentration signifi- cantly increased total plant dry weight recorded at the cessation of the experiment. Application of both calcium fertilizers at concentrations of less than 40 g/m2 provided no significant protectant properties. Applications of more than 40 g/m2 proved phytotoxic to the two test species. Irrespective of concentration, applications of N:P:K (24:7:7) fertilizer did not enhance or increase susceptibility to freezing and salinity damage compared to nonfer- tilized controls. However, N:P:K (24:7:7) fertilization significantly increased leaf chlorophyll content and total plant dry weight. Results indicate that fall applications of calcium nitrate and calcium nitrate borate at 40 g/m2 can increase the freezing and salinity tolerance of evergreen oak and holly. Key Words. Evergreen Oak; Holly; Chlorophyll Fluorescence; Electrolyte Leakage; SPAD Values; Chlorophyll Content; Fertilizer. Ryan R. Jensen and Perry J. Hardin ESTIMATING URBAN LEAF AREA USING FIELD MEASUREMENTS AND SATELLITE REMOTE SENSING DATA ...........................................................................................................21 Abstract. Accurate estimation of urban leaf area is important in understanding the urban forest’s role in heat island mitigation, pollution removal, and carbon sequestration. Remotely sensed satellite data provide an alternative method to inexpensively and nondestructively estimate this impor- tant urban biophysical variable. Ceptometer measurements of leaf area index (LAI) at 143 urban sites in Terre Haute, Indiana, U.S., were modeled as a function of reflected radiance flux sensed by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). Multiple regres- sion models of LAI were compared to estimates produced by feed-forward back-propagation artificial neural networks. The most accurate estima- tion was produced by the neural network utilizing the ASTER green band and the ratio of the ASTER red and near-infrared bands. In this case, the simple correlation between the observed and predicted LAI values was moderately high (R = 0.71). The standard error of the LAI estimate was 1.35. In every case, the predictive accuracy of the neural network models exceeded the multiple regression models Examination of the parameters in the successful models indicates that the estimation of urban LAI in Terre Haute is physically predicated on the relative proportions of leaf chlo- rophyll, leaf spongy mesophyll, and indurate matter (e.g., concrete, asphalt, soil) constituting the individual picture elements of the satellitimage. Key Words. Leaf Area; Remote Sensing; Ceptometer; Leaf Area Index. Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) www.isa-arbor.com Margaret T. Mmbaga, Roger J. Sauvé, Emmanuel Nnodu, and Suping Zhou MULTIPLE DISEASE RESISTANCE TO POWDERY MILDEW, BACTERIAL BLIGHT, AND ALTERNARIABLIGHT IN LILACS (SYRINGA SPP.) ..........................................................................................1 Abstract. Fiſty-six lilac accessions were evaluated in a 4-year study for resistance to powdery mildew caused by Microsphaera syringae, bacterial blight caused by Pseudomonas syringae pv. syringae, and Alternaria blight caused by Alternaria alternata. Accessions included 39 cultivars of Syringa vulgaris, four of S. prestoniae, three of S. hyacinthiflora, two of S. josiflexa, two of S. meyeri, two of S. reticulata, and one each of S. patula, S. chinensis, S. henryi, and S. microphylla. Of these, six accessions were resistant or moderately resistant to Alternaria blight and powdery mildew, four to bacte- rial blight and Alternaria blight, and 20 to powdery mildew and bacterial blight. Two cultivars of S. meyeri, ‘Dwarf Korean’ and ‘Palibin’, were resis- tant to all three pathogens. During this study, the most serious disease of lilacs in middle Tennessee, U.S., was Alternaria blight.It caused severe leaf scorching and defoliation that began in early July. Powdery mildew and bacterial blight caused mostly superficial damage with little effect on growth. Key Words. Alternaria alternata; Disease Complex; Microsphaera syringae; Plant Health Care; Pseudomonas syringae pv. syringae; Syringa spp.; ©2005 | International Society of Arboriculture | ISSN:1935-5297
January 2005
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