GIS Analysis of Invasive Prosopis juliflora Dynamics in two Selected Sites from the United Arab Emirates

摘要

High resolution digital aerial photographs were used to rate the change and to evaluate the woody Prosopis juliflora dynamics in northern Unite Arab Emirates, Filayah (untreated) and Khut (treated). A time series of three different dates: 1986, 1996, and 2005 were chosen. On-screen digitizing of plant communities was conducted using interpretative elements such as shape, tone texture and shadow; production of final maps was achieved with acceptable accuracy. We built a geo-database containing layers representing different dates for both sites. We performed statistical analysis to rate changes of the following four spatial attributes: percent cover, patch density, patch size, and mean patch shape index. Finally, we conducted a GIS Overlay analysis to visualize plant dynamics and to explore possible spatial associations. Results confirm that Prosopis juliflora is a very active and dynamic invader which has the potential to threaten the local environment; as its percent cover as well as its patch density increased noticeably during the study period (1986-2005). We concluded that Prosopis juliflora seems to go through phases of expansion. First, an accelerated expansion earlier in the establishment period, then the distribution reaches a plateau. This plateau may be an optimum density of Prosopis juliflora in that region. The time period for such optimum is suggested to be 10 years from invasion.