Characterization of vegetation community dynamics in areas affected by construction waste along the urban fringe

摘要

The effects of urban sprawl, at the expense of green natural areas, and the increasing anthropogenic pressure on these areas, lead to significant changes in land cover composition and structure. One of the threats and hazardous aspects of the urban sprawl is the disposal of construction site waste (CW) at the cities' fringes and by the roadsides. The analysis of vegetation community structure over space and time in such areas may contribute to the understanding of community dynamics at the urban fringe following modern human intervention. Therefore, the purpose of this study was to characterize the composition and structure of vegetation communities in construction waste and rubble areas at the city of Haifa's fringe. A control undisturbed site, and sites that were disturbed 20, 40 and 60 years prior to the study were selected and studied. The results indicate that superficially there is no difference among the communities. A closer analysis, however, reveals that there is a significant segregation in species assembly between the control and the damaged sites, and that this difference becomes more significant as time passes. Initially, recently disturbed sites were characterized by a higher abundance of ruderal species, where mean number of ruderal species was 1.75/sampling quadrate, compared to 0.08 species/sampling quadrate. As time passes, the number of exotic species increased from 0.09 species/ sampling quadrate at the 20 year disturbed site to 1.02 at the 60 year sites. Additionally, cover of climber species in the sites significantly increased with time, and other local life form groups declined in richness. Further, we have found that the impact of the CW is spreading beyond the area that it was found and into the open and undeveloped area that surround the city.