Obstacles and Limitations of Remote Sensing Application in Estimating Botanical Parameters in Arid and Semi-Arid Areas

The principled use and proper management of arid and semi-arid regions, which cover a significant extent of the Earth’s drylands, require planning based on accurate and timely information on different ecosystem components, including vegetation. Considering vegetation is one of the major and important needs in the management and exploitation of arid and semi-arid regions. Since it is time consuming and costly to collect information at vast levels in dry and desert conditions by traditional ways and through ground operations, the use of new techniques in these studies is necessary. Remote sensing is one of the most effective techniques in this field. The arid and semi-arid regions have low Leaf Area Index and fairly open crowns due to reactions to environmental stresses, which makes the surface soil visible in these areas. The high effect of surface soil on spectral reflections of vegetation in arid and semi-arid regions causes mistakes in evaluating plants in these areas through remote sensing. Many studies have been carried out on introducing suitable plant indices for assessing vegetation changes in arid and semi-arid regions. The results of all these studies indicate that due to variability of vegetation and soil characteristics in different regions of arid and semi-arid regions, as well as differences in utilized satellite data in terms of sensor type, bands number, spectral range, spatial accuracy, etc. it is not possible to introduce a specific indicator for vegetation studies in all arid and semi-arid regions, but, considering the characteristics of vegetation, soil and the type of used satellite data, indicator or indicators that are meaningful according to studies can be introduced for each region. The aim of this study is to investigate the spectral reflections of vegetation in arid and semi-arid regions considering different reactions of plants in arid and semi-arid regions against environmental stresses, the openness of crown of vegetation, and the high effect of surface soil on the reflection of the vegetation in these areas, and to introduce a suitable technique for studying the vegetation of such areas.