Arboriculture & Urban Forestry 32(1): January 2006 41 ARBORICULTURAL ABSTRACTS ADAPTIVE MANAGEMENT APPROACH TO INCREASING THE DIVERSITY OF A 30- YEAR-OLD PLANTED FOREST IN AN URBAN AREA OF JAPAN Akihiro Nakamura, Yukihiro Morimoto, and Yasuko Mizutani Thirty years have passed since the completion of land reclamation and the planting of broad-leaved evergreen trees at the Expo’70 Commemorative Park, which was developed in an urban area of Osaka, the second largest city in Japan. Canopy closure and biomass development of the forests in the park are proof of the success of the revegeta- tion of laurel forests. However, because low penetration of solar radiation to the forest floor seemed to restrict the diversity of forest floor vegetation, we carried out adaptive forest management to increase the diversity. To improve the light environment on the forest floor, we created four artificial gaps, each 15 by15 m (49.5 ft). Further, to establish a new diverse population from seed, we spread forest topsoil from a secondary forest containing a diverse seedbank over these gaps. The average gap fraction under the intact canopy was 0.09. Partial removal of trees (52% of basal area) increased the average gap fraction to 0.19 and heavy removal (more than 88% of basal area) increased it to 0.29–0.54. Species number and density of germinated seedlings became significantly greater in the gaps than under the intact canopy. Many seedlings arose in the gaps from the seedbanks that have built up over the last 30 years in the topsoil of the park forest. Only 1 year after creation of gaps, the spread of forest topsoil had resulted in the germination of six species that did not exist in the park before, indicating the possibility of creating diverse popula- tions. In the partial removal plot, the seedling density was the highest, but the seedling death rates were also large and the seedlings grew the least. Differences in the light environ- ment as determined mainly by removal intensity might affect patterns of revegetation from a seedbank. (Landscape and Urban Planning. 2005. 70(3–4): 291–300) THE URBAN FOREST IN BEIJING AND ITS ROLE IN AIR POLLUTION REDUCTION Jun Yang, Joe McBride, Jinxing Zhou, and Zhenyuan Sun Tree planting has been proposed by the municipal govern- ment 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 t 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 t. The carbon dioxide (CO2 ) stored in biomass form by the urban forest amounted to about 0.2 million t. Future research directions to improve our understanding of the role of individual tree species in air pollution reduction are discussed. (Urban Forestry & Urban Greening. 2005. 3(2):65–78) THE INFLUENCE OF WIND ON BRANCH CHARACTERISTICS OF PINUS RADIATA M.S. Watt, J.R. Moore, and B. McKinlay Measurements taken from trees growing in exposed and sheltered areas within two structurally similar forests were used to investigate the influence of wind on branch charac- teristics of mature New Zealand–grown Pinus radiata. A widely used branch model was used to remove the influence of treatment and site differences in tree stem diameter and height, so that the influence of wind on branch diameter could be examined. At site 1, average windspeed in the exposed treatment exceeded average windspeed in the sheltered treatment by 62%. When averaged across sites, mean branch diameter, branch index (mean diameter of the largest branch, in each of the four azimuthal quadrants), and largest branch diameter in exposed areas significantly exceeded values for trees in sheltered areas by 9 mm (0.4 in, 25%), 42 mm (1.7 in, 54%), and 72 mm (2.9 in, 72%), respectively. Treatment and site differences in tree stem diameter and height partially accounted for the observed increases in branch diameter. However, after these effects were removed by the model, branch diameter in exposed areas still significantly exceeded that in sheltered areas by 21 mm (0.9 in) for branch index and 44 mm (1.8 in) for the largest branch. Treatment and site variation in this residual branch diameter was almost entirely attributable to topo- graphical exposure to 1 km (0.6 mi), a variable that has been found to be strongly correlated to windspeed. Possible ©2006 International Society of Arboriculture
January 2006
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