Journal of Arboriculture 31(5): September 2005 269 ARBORICULTURAL ABSTRACTS USING AVIRIS DATA AND MULTIPLE-MASKING TECHNIQUES TO MAP URBAN FOREST TREE SPECIES Q. Xiao, S.L. Ustin, and E.G. McPherson Tree type and species information are critical parameters for urban forest management, benefit cost analysis, and urban planning. However, traditionally, these parameters have been derived based on limited field samples in urban forest manage- ment practice. In this study, we used high-resolution Airborne Visible Infrared Imaging Spectrometer (AVIRIS) data and multiple-spectral masking techniques to identify and map urban forest trees. Trees were identified based on their spectral character difference in AVIRIS data. The use of multiple- masking techniques shifts the focus to the target land cover types only, thus reducing confounding noise during spectral analysis. The results were checked against ground reference data and by comparison to tree information in an existing geographical information system (GIS) database. At the tree type level, mapping was accomplished with 94% accuracy. At the tree species level, the average accuracy was 70% but varied with both tree type and species. Of the four evergreen tree species, the average accuracy was 69%. For the 12 deciduous tree species, the average accuracy was 70%. The relatively low accuracy for several deciduous species was due to small tree size and overlapping among tree crowns at the 3.5 m spatial resolution of AVIRIS data. This urban forest tree species mapping method has the potential to increase data update intervals and accuracy while reducing costs compared to field sampling or other traditional methods. (Int. J. Remote Sensing. 2004. 25(24):5637–5654) MOLECULAR DIVERSITY OF NODULES OF IN ROOT GROWN WITH INOCULUM FROM POLLUTED URBAN SOILS K.P. Ridgway, L.A. Marland, A.F. Harrison, J. Wright, J.P.W. Young, and A.H. Fitter The establishment and growth of trees can be compromised by soil contamination, which can reduce populations of key microbial symbionts. We describe the colonization of gray alder (Alnus incana) by Frankia from 10 urban soils with varying degrees of organic and inorganic pollution. Princi- pal components analysis (PCA) of soil chemical profiles showed a separation of remediated and unremediated soils. Alnus incana seedlings were used as trap plants to capture the microsymbiont from soil. After 6 months’ growth, nodulation was lowest on trees grown with the most contaminated soils. Plant biomass was positively correlated with root nodule biomass and negatively correlated with polycyclic aromatic hydrocarbon (PAH) concentration. DNA was isolated from nodules for the analysis of Frankia genetic diversity. The polymerase chain reaction (PCR) was used to amplify the 16S-23S intergenic spacer (IGS) of Frankia ribosomal DNA. PCR products were subject to restriction digestion yielding 10 restriction fragment length polymorphism (RFLP) types from 72 nodules analysed. Our results demonstrate that each soil supports a distinct nodulating Frankia community. Partial 16S sequencing placed most strains in Frankia clusters 1a and 1b, which are typically Alnus incana-infecting, but sequences from several nodules obtained from a gasworks soil belonged to cluster 3, normally associated with Elaeagnus. These results show for the first time that polluted soils can be an effective source of Alnus incana-infective Frankia. Inoculation with site-adapted Frankia under greenhouse conditions could thus be an appropriate strategy to increase the symbiotic capacity of Alnus incana and to improve its chances of survival and growth when planted on polluted soils. (FEMS Microbiol. Ecol. 2004. 50(3):255–263) EXPLORING FUNCTIONAL DEFINITIONS OF MYCORRHIZAS: ARE MYCORRHIZAS ALWAYS MUTUALISMS? Melanie D. Jones and Sally E. Smith Mycorrhizas are considered to be classic mutualisms. Here, we define mutualism as a reciprocal increase in fitness of the symbionts, and we review the evidence for mycorrhizal mutualism at the community, whole-plant, and cellular scales. It is difficult to use results of most mycorrhizal studies because (1) fungal contribution to nutrient uptake is not accurately estimated, (2) increased growth is not necessarily correlated with increased plant fecundity or survival, especially in communities, and (3) benefits that occur only at certain times of year, or under specific extreme conditions, may not be detected. To produce the nonmycorrhizal controls required to study mutualism in the field, soil microflora and fauna must be severely perturbed; therefore, it is virtually impossible to evaluate effects of mycorrhizas on plant fitness under realistic conditions. Using the evidence available, we conclude that mycorrhizas can occupy various positions along the continuum from parasitism to mutualism, depending on the specific plant and fungal genotypes and their abiotic and biotic environments. Although we discuss the possibil- ity of defining mycorrhizas by some physiological charac- teristic, we conclude that mycorrhizas should be defined on a structural or developmental basis and that any require- ment to demonstrate mutualism be eliminated. (Can. J. Bot./Rev. Can. Bot. 2004. 82(8):1089–1109) ©2005 International Society of Arboriculture ALNUS INCANA FRANKIA
September 2005
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