DEGRADATION OF AN ARID ENVIRONMENT: EARTH FISSURES IN CENTRAL ARIZONA.

摘要

The surficial desertification and degradation characteristics of major elements of the natural environment (vegetation, drainage, and morphology) associated with the development of earth fissures were investigated. Three appropriate fissure sites within a general study area located southeast of Phoenix, Arizona were carefully selected to minimize cultural influences.; Data for analysis were collected from satellite imagery and aerial photography, and from ground level surveys. Traditional remote sensing analysis techniques were employed to identify degradational characteristics which appear on the various remotely-sensed data bases. Remote sensing techniques were incorporated into the investigation to provide an overall, comprehensive view to enhance the spatial arrangement of anomalies suggestive of degradational characteristics. On-site data collection involved taking calculated transects across the various fissures to provide micro-scale information suggestive of degradational characteristics. These ground surveys involved the collection of physical measurements of individual fissures; apparent plant stress information; gross thermal characteristics; erosional characteristics and anomalies; and apparent surficial changes in the natural drainage, morphology, and vegetation.; The results of analysis indicate that the occurrence of true desertification does not exist, but that degradation clearly exists, primarily in the form of erosion, and is the result of earth fissure development. Erosion was found to occur in two ways: that which is commonplace beginning at fissures and migrating up-slope, and that which washes soil from around plant roots. In addition, minor selective changes in the vegetation, drainage, and morphology were clearly identified and proven to be the result of earth fissure development. It is concluded that erosion can not be effectively halted and, as a result, will spread widely resulting eventually in desertification.