86 Arboricultural Abstracts ARBORICULTURAL ABSTRACTS PLANT COMMUNITIES OF SELECTED URBANIZED AREAS OF HALIFAX, NOVA SCOTIA, CANADA K. Turner, L. Lefler, and B. Freedman This study was designed to compare plant biodiversity and community indicators among urban residential areas and more-natural habitats in the vicinity of Halifax, Nova Scotia. Six house lots were examined in each of three age categories of residential neighborhoods (>80 years, 30–50 years, and <10 years), and these were compared to four forested plots in semi-natural urban parks and four in a natural forest. The residential areas represented broad stages of successional de- velopment of “urban forest,” while the stands of semi-natural and natural forest are representative of the original habitats that have been converted into residential land use. In general, the observed plant species richness was much higher in the residential areas, but these habitats were strongly dominated by non-indigenous species, whereas the natural and semi- natural habitats supported native taxa. This obvious differ- ence between residential areas and semi-natural/natural habi- tats was confirmed by cluster analysis and principal compo- nents analysis, both of which separated the sample sites into two groups of plant communities. Neighborhood age and proximity of the residential sites had little influence on these multivariate analyses, suggesting that site-specific manage- ment practices (such as horticultural choices of landowners) had a strong influence on plant-community structure. Woody vegetation (trees and shrubs) in the semi-natural and natural forest had a higher basal area and stored more biomass and carbon than in residential habitats. However, there was a successional progression in the urban forest, in that older habitats stored much more woody carbon than younger ones. Although well-vegetated residential neighborhoods provide important environmental services, their striking dominance by exotic species, as well as their lower carbon storage in vegetation, contribute to an impoverishment of ecological integrity. This circumstance could be partially mitigated by changing horticultural management to encourage naturaliza- tion, particularly through the planting of indigenous species. (Landscape and Urban Planning 2004. 71(2–4):191–206) DIFFERENTIAL SECTORIALITY IN LONG-DISTANCE TRANSPORT IN TEMPERATE TREE SPECIES: EVIDENCE FROM DYE FLOW, 15N TRANSPORT, AND VESSEL ELEMENT PITTING Colin M. Orians, Margret M.I. van Vuuren, Nancy L. Harris, Benjamin A. Babst, and George S. Ellmore The capture of patchily distributed nutrients by tree roots has received extensive research, but the fate of those nutrients has not. We performed experiments to determine whether nutri- ent transport within tree species is preferentially transported from specific roots to specific branches. Saplings of five spe- cies with contrasting growth requirements were examined: two Betula species (B. papyrifera and B. lenta), Populus tremuloides, and two Acer species (A. saccharum and A. ru- brum). To quantify patterns of long-distance transport, we examined the accumulation of safranin-O dye and 15N in branches when these tracers were applied to isolated lateral roots (dye and 15N) and to the main root system (15N). Because transport of nutrients between sectors requires flow through intervessel pit pairs of adjacent xylem vessel ele- ments, we quantified the area of intervessel pits, the number of pits per unit vessel wall area, and the percentage of vessel wall area as pits in Acer and Betula. We found that the two Betula species were integrated (tracers applied to isolated roots were likely to accumulate in all branches), while P. tremuloides and the two Acer species were sectorial (tracer accumulation was more concentrated in particular branches). Betula had the largest number of intervessel pits per unit vessel wall area and the largest percentage of vessel wall area as pits. The high density of bordered pits may explain the ease of tracer movement throughout the two Betula species. Greater integration may allow certain trees (e.g., Betula) to exploit nutritionally patchy environments such as rocky soils and may alter plant–herbivore interactions. (Trees—Structure and Function 2004. 18(5):501–509) NATURE IN THE RETAIL ENVIRONMENT: COMPARING CONSUMER AND BUSINESS RESPONSE TO URBAN FOREST CONDITIONS Kathleen L. Wolf Most research addressing public response to the urban forest has occurred in residential settings; little is known about con- sumer response to trees in retail places. This study evaluated ©2006 International Society of Arboriculture
March 2006
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