Arboriculture & Urban Forestry 34(6): November 2008 Arboriculture & Urban Forestry 2008. 34(6):393–394. 393 ARBORICULTURAL ABSTRACTS 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) PATTERN AND DIVERGENCE OF TREE COMMUNITIES IN TAIPEI’S MAIN URBAN GREEN SPACE C.Y. Jim and Wendy Y. Chen Urban vegetation increasingly contributes to nature conservation and ecosystem services, but lacking understanding of site varia- tions has restricted such uses. This study analyzed the spatial pattern and differentiation of tree communities in three major green landscape types (urban parks, riverside parks and street verges) in Taipei city. In each landscape type, 10 representative tree communities were studied. Statistical tests for ecological communities were employed: Jaccard and Q species similarity indices, two-way indicator species analysis (TWINSPAN), and new species fidelity, landscape fidelity and composite Q indices. Significant recent increase in Taipei’s green spaces was traced. The study area contained 164 tree species, but few were shared by the three landscape types and none by 30 communities. Na- tive evergreen broadleaf species with large final dimensions were dominant. Urban parks registered the highest species rich- ness, landscape fidelity, rare species and urban endemics. Such exclusive species constitution deviated notably from riverside parks and street verges, with relatively simple and converging intra-site species ingredients. Pronounced species differentiation between urban parks reflected diversified site topography, natu- ral woodland inheritance, woodland creation, and past landscape fashion. TWINSPAN classified the communities into nine groups each with signature characteristics. Inherent site varia- tions offered main determinants of tree heterogeneity, superim- posed by human modification to satisfy pre-determined site functions. A hybrid urban park with high species diversity and nature contents is advocated by amalgamating conventional but polarized designs of country and urban parks. The findings could inform management of urban forest, urban nature conservation, and ecological services of urban green spaces. (Landscape and Urban Planning 2008. 84(3–4):312–323) A DOUBLE-HURDLE MODEL OF URBAN GREEN AREAS VALUATION: DEALING WITH ZERO RESPONSES Salvador del Saz-Salazar and Pau Rausell-Köster Due to the widespread support for public parks and open spaces in urban areas, there is an increasing need to analyse the social benefits that are generated by such amenities. The city of Va- lencia (Spain) has a large park that can be considered its green backbone due to its transversal layout running along 9 of the 19 districts into which the city is divided. A contingent valuation survey was therefore conducted in order to obtain the non- market benefits derived from the use of this park by the inhab- itants of Valencia. In addition, to deal with the large number of zero responses obtained, a Double-Hurdle model was applied. The results show that this model is more appropriate than other, simpler approaches. They also show that willingness to pay is positively related with the respondent’s income and education, as was expected. Another interesting finding is that willingness to pay is also affected by the section of the park in which the interview was conducted. The information gathered form this study is of interest to decision-making with regard environmen- tal issues. (Landscape and Urban Planning 2008. 84(3–4):241– 251) UBANIZATION PRESSURES ON THE NATURAL FORESTS IN TURKEY: AN OVERVIEW Erdog ˘an Atmis ¸, Sezgin Özden, and Wietze Lise Forests used to be the main field of interest for rural communi- ties, but now they attract the attention of urbanites too. The forest–public relationship is important as forests protect water resources, preserve the soil and increase its productivity, provide positive effects on climate and health in general, and can be used for recreation and tourist purposes. This study aims at assessing how the current rapid urbanization process in Turkey affects forests. Urban requirements such as biomass for heating, educa- tion facilities, settlements, recreation, tourism, and employment exert various pressures on the forest. In this study we assessed these pressures and suggest that forest legislations should be developed to respond to expectations of urbanites from forests, new recreation areas should be developed and urbanites’ interest in and knowledge of the forests should be increased, where all ©2008 International Society of Arboriculture
November 2008
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