INDEPENDENT AND CONTRASTING EFFECTS OF ELEVATED CO2 AND N-FERTILIZATION ON ROOT ARCHITECTURE IN PINUS PONDEROSA
David T. Tingey, Mark G. Johnson, and Donald L. Phillips
The effects of elevated CO2 and N-fertilization on the architecture of Pinus ponderosa fine roots and their associated mycorrhizal symbionts were measured over a 4-year period using minirhizotron tubes. The study was conducted in open-top field-exposure chambers located near Placerville, Calif. A replicated (3 replicates), 3 × 3 factorial experimental design with three CO2 concentrations [ambient air (354 μmol mol−1), 525 μmol mol−1, and 700 μmol mol−1] and three rates of N-fertilization (0, 100, and 200 kg ha−1 year−1) was used. Elevated CO2 and N treatment had contrasting effects on the architecture of fine roots and their associated mycorrhizae. Elevated CO2 increased both fine root extensity (degree of soil exploration) and intensity (extent that roots use explored areas) but had no effect on mycorrhizae. In contrast, Nfertilization had no effect on fine root extensity or intensity but increased mycorrhizal extensity and intensity. To better understand and model the responses of systems to increasing CO2 concentrations and N deposition/fertilization it is necessary to consider these contrasting root architectural responses. (Trees—Structure and Function 2005. 19(1):43–50)
IMPACT OF THE LEAF MINER CAMERARIA OHRIDELLA ON WHOLE-PLANT PHOTOSYNTHETIC PRODUCTIVITY OF AESCULUS HIPPOCASTANUM: INSIGHTS FROM A MODEL
Andrea Nardini, Fabio Raimondo, Mauro Scimone, and Sebastiano Salleo
The leaf miner Cameraria ohridella causes premature defoliation of Aesculus hippocastanum trees. In order to assess the whole-plant loss of productivity caused by the parasite, we monitored seasonal changes of leaf gas exchange and leaf area losses in horse chestnut trees freely infested or chemically treated to prevent moth infestation (controls). Data were integrated in a model and the annual loss of net primary productivity (NPP) was calculated for infested trees with respect to controls. Measurements showed marked vertical stratification of C. ohridella attacks, with lower crown strata being more infested than higher ones. Leaf gas exchange was maximum between May and early June, but it strongly decreased starting from mid-June even in controls. Model calculations showed that NPP loss of infested trees was about 30% on an annual basis (when the first moth attack is recorded at the end of April). Model simulations showed that postponing the start day of attack would have important positive effects on plants NPP. For example, if the start day of attack was postponed to 20 May, the annual loss of NPP would be about 15%. Our study suggests that A. hippocastanum trees attacked by C. ohridella are not facing serious risks of decline, especially if methods are adopted to postpone the start day of attack (e.g., removal of fallen leaves in autumn). Our data do not support the view that plants need to be totally protected from the parasite by application of insecticides. (Trees—Structure and Function 2004. 18(6):714–721)
DEFINING THE SUSTAINABLE PARK: A FIFTH MODEL FOR URBAN PARKS
Galen Cranz and Michael Boland
How can parks contribute to the overarching project of helping cities become more ecologically sustainable? The history of urban parks in America reveals more concern with social problems than with ecological sustainability. Four types of city parks have been identified—the Pleasure Ground, the Reform Park, the Recreation Facility, and the Open Space System—and each of them respond to social issues, not ecological ones. Yet today, ecological problems are becoming one of our biggest social concerns, so a new urban park type focused on social solutions to ecological problems would be consistent with this pattern. Using the same social and physical criteria that described the previous four models, Part I describes a fifth model, the Sustainable Park, which began to emerge in the late 1990s. Part II postulates three general attributes of this new kind of park: (1) self-sufficiency in regard to material resources and maintenance, (2) solving larger urban problems outside of park boundaries, and (3) creating new standards for aesthetics and landscape management in parks and other urban landscapes. It also explores policy implications of these attributes regarding park design and management, the practice of landscape architecture, citizen participation, and ecological education. (Landscape Journal 2004. 23(2):102–120)
A NON-INVASIVE ACOUSTIC TOOL REVEALING DECAY IN TREES
D. Rioux
A non-invasive sonic tomography apparatus was developed on the basis of the fact that waves produced by tapping sensors with a small hammer move more slowly through decayed or altered wood than through sound wood. Data were analyzed using software that reconstitutes in two dimensions, the internal structure of the tree. Evaluations were made of 27 cross-sections from ten white oak (Quercus alba) and three hickory trees (Carya spp). The trees were felled to assess the actual decayed areas. Ten cross-sections were found to have no decay and were correlated by the sonic tomography analysis. When decay was present, differences between data obtained by the apparatus and actual values were on the average 5%. These results suggest that such a method could become an essential working tool in urban forestry. (Phytoprotection 2004. 85(2):68–70)
THE USE OF PROFILE DIAGRAMS FOR MIXED STANDS IN URBAN WOODLANDS—THE MANAGEMENT PERSPECTIVE
Anders Busse Nielsen and Jens Balsby Nielsen
In the emerging paradigm of urban forestry, objectives are often to develop mixed stands with complex structures. Such stands cannot easily be described in words and numbers. A logical alternative would seem to describe the structure of such mixed stands by use of image-based management tools. However implementing new management goals and using image-based tools challenges professionals, educated and trained within the age-class forestry tradition, to use their knowledge in a creative way. This paper describes how professionals contextualize from hand-drawn profile diagrams when planning the management of mixed stands. The appropriateness of profile diagrams in this context is further discussed. The study was carried out as a case study focusing on the planning and development of long-term management goals for two young, mixed stands for recreational use. We used explorative, in-depth interviews to identify the perspective on profile diagrams, as experienced by five individuals with different academic backgrounds as well as varying years of experience. The interviewees revealed that personal experiences and mental images played a key role forming an intuitive understanding of the subject stands through the profile diagrams. Further, they recognized this approach themselves, often referring to other stands to make comparisons. The types of references used could be divided into three distinct categories: specific, generic, and metaphoric. With regard to the ongoing move from age-class forestry to multifunctional management of mixed stands, this aid to dialogue might be the most relevant way in which profile diagrams can contribute to the implementation of new management paradigms. (Urban Forestry and Urban Greening 2005. 3(3–4):163–175)
THE URBAN FOREST IN BEIJING AND ITS ROLE IN AIR POLLUTION REDUCTION
Jun Yanga, Joe McBride, Jinxing Zhou, and Zhenyuan Sun
Tree planting has been proposed by the municipal government as a measure to alleviate air pollution in Beijing, the capital of China. This study examines that proposal. It is based on the analyses of satellite images and field surveys to establish the characteristics of current urban forest in the central part of Beijing. The influence of the urban forest on air quality was studied using the Urban Forest Effects Model. The results show that there are 2.4 million trees in the central part of Beijing. The diameter distribution of the trees is skewed toward small diameters. The urban forest is dominated by a few species. The condition of trees in the central part of Beijing is not ideal: about 29% of trees were classified as being in poor condition. The trees in the central part of Beijing removed 1261.4 tons of pollutants from the air in 2002. The air pollutant that was most reduced was PM10 (particulate matters with an aerodynamic diameter smaller than 10 μm), the reduction amounted to 772 tons. The carbon dioxide (CO2) stored in biomass form by the urban forest amounted to about 0.2 million tons. Future research directions to improve our understanding of the role of individual tree species in air pollution reduction are discussed. (Urban Forestry and Urban Greening 2005. 3(2):65–78)
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