Arboriculture & Urban Forestry 34(4): July 2008 Arboriculture & Urban Forestry 2008. 34(4):267–268. 267 ARBORICULTURAL ABSTRACTS PREDICTING OPPORTUNITIES FOR GREENING AND PATTERNS OF VEGETATION ON PRIVATE URBAN LANDS Austin Troy, J. Grove, J. O’Neil-Dunne, S. Pickett, and M. Cadenasso This paper examines predictors of vegetative cover on private lands in Baltimore, Maryland. Using high-resolution spatial data, we generated two measures: “possible stewardship,” which is the proportion of private land that does not have built structures on it and hence has the possibility of supporting vegetation, and “realized stewardship,” which is the proportion of possible stew- ardship land upon which vegetation is growing. These measures were calculated at the parcel level and averaged by US Census block group. Realized stewardship was further defined by pro- portion of tree canopy and grass. Expenditures on yard supplies and services, available by block group, were used to help un- derstand where vegetation condition appears to be the result of current activity, past legacies, or abandonment. PRIZM™ mar- ket segmentation data were tested as categorical predictors of possible and realized stewardship and yard expenditures. PRIZM™ segmentations are hierarchically clustered into 5, 15, and 62 categories, which correspond to population density, so- cial stratification (income and education), and lifestyle clusters, respectively. We found that PRIZM 15 best predicted variation in possible stewardship and PRIZM 62 best predicted variation in realized stewardship. These results were further analyzed by regressing each dependent variable against a set of continuous variables reflective of each of the three PRIZM groupings. Hous- ing age, vacancy, and population density were found to be criti- cal determinants of both stewardship metrics. A number of life- style factors, such as average family size, marriage rates, and percentage of single-family detached homes, were strongly re- lated to realized stewardship. The percentage of African Ameri- cans by block group was positively related to realized steward- ship but negatively related to yard expenditures. (Environmental Management 2007. 40(3):394–412) CONTRASTING BELOW- AND ABOVEGROUND RESPONSES OF TWO DECIDUOUS TREES TO PATCHY NITRATE AVAILABILITY Vit Gloser, Katherine Libera, and Colin M. Orians We investigated how patchy nitrate availability influences growth and functioning of plant roots and generates, through vascular constraints on long-distance transport, aboveground heterogeneity in plant growth and chemistry. We examined two broadleaf tree species, Acer rubrum L. and Betula papyrifera Marsh. Plants were grown either in a split-root setup where a single root received full nutrient supply and the rest of the root system received all nutrients except nitrogen (patchy treatment), or in a single pot with full nutrient supply (homogeneous treat- ment). In both species, fine roots proliferated in the nitrogen patch, but B. papyrifera produced twice as much fine root bio- mass in response to patchy nitrate availability as did A. rubrum. There was no difference between treatments in nitrogen uptake rate in either species. In general, specific water uptake was higher in A. rubrum than in B. papyrifera, especially in the nitrogen-rich side pot. When nitrate availability was patchy, ni- trate reductase activity in roots and leaves was unaffected in either species. In A. rubrum, but not in B. papyrifera, patchy nitrate supply resulted in aboveground heterogeneity, with leaves above the N-fertilized roots being larger and having a higher relative chlorophyll concentration than those inserted in the op- posite quarter of the stem. (Tree Physiology 2008. 28:37–44) ACCUMULATION OF DEICING SALTS IN SOILS IN AN URBAN ENVIRONMENT Mary Ann Cunningham, Eric Snyder, Daniel Yonkin, Morgan Ross, and Toren Elsen Examining rates of deicing salt accumulation and leaching in urban soils is important for understanding the distribution and movement of salt in the environment. We examined autumn concentrations of deicing salts in soils in a moderately dense urban landscape in eastern New York State. The study area contrasted to the isolated, rural highways examined in previous studies. While NaCl was the most abundantly applied salt, Mg2+ (apparently from MgCl2, a secondary deicing salt) was the most abundant salt cation in soils. Moderate Na+ levels, and equiva- lent concentrations at depth and in surface samples, indicate that leaching of Na+ is rapid in this system. Leaching may ameliorate toxicity for land plants but accelerate inputs to aquatic systems. In contrast to rural highway studies, where salt levels declined rapidly with distance to pavement, Na+ remained elevated at the maximum distance measured. Airborne salt dispersal and dense networks of pavement likely contribute to widespread elevated salt levels. This semi-urban setting had salt levels high enough to be toxic to terrestrial plants and soil protozoa. Even moderate levels of development can have dramatic effects on salt inputs into soils and aquatic systems. (Urban Ecosystems 2008. 11(1): 17–31) WHAT DO FORESTERS THINK ABOUT URBAN FORESTRY, URBAN PEOPLE, AND CITIES? Robert M. Ricard and Maureen H. McDonough Urban residents affect forest policy and hence forest manage- ment decisions and outcomes. In addition, urban forestry has become more visible, integrated, and influential in the Society of American Foresters (SAF). However, little is known about what foresters think urban people know about forestry, what emphasis foresters believe should be placed on urban forestry compared with traditional forestry, and what foresters think about the pur- poses of urban forestry. Results of a nationwide mail survey of SAF members suggest that urban forestry is well accepted as a community of interest by respondents, that respondents lean more toward loving cities than hating them, and that respondents ©2008 International Society of Arboriculture
July 2008
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