Thresholds of GeoDiversity: Concepts and methods for identifying Desert Boundaries in Heterogeneous Spatio-temporal patterns
Desert thresholds are narrow zones of spatial instability (irreversible transition) between semi-arid and arid regions. Identifying shifts in these zones are indicators of Climate change and Desertification. However, this task is difficult due to of the high spatio-temporal diversity of vegetation, soil and bare rock patterns in these regions. We have employed three concepts for this purpose:
- Concept I: Boundary stability and shifts during extreme rainfall fluctuations are indicators to areas which lost their response potential versus areas which maintain resilience. This was assessed for the years 1991 and 1992 where the first represents the lowest and the second the highest 60 record (Figure 1).
- Concept II: Boundaries in Life-forms’ compositions (Shrubs, Dwarf-shrubs, Herbaceous growth) along the climatic gradient (Figure 2). Dwarf shrubs distributions are key indicators for shifts in their two transition zones: their competition with grasses at the lower rainfall edge (200-250 mm/year) versus their ‘invasion’ into disturbed shrub areas at the higher rainfall edge (350-450 mm/year).
- Concept III: Boundaries in potential pattern instability. Implementation of morphological dilation and erosion of existing patterns as inferred from Landsat Images would allow quantification of the magnitude of potential change. Zones of high potential pattern change are “Thresholds of Geo- diversity”. Differences between the computed potentials are indicators of the reversability of surface conditions. The approach is implemented along the climatic gradient between the Judean Mountains and the Dead Sea in central Israel using mid-resolution Landsat TM data and assessed with reference to lithological, soil and phytogeographical boundaries as delineated from existing maps (Figures 3&4)
- Shoshany, M., Kutiel, P. and Lavee, H., 1994, Remote Sensing of vegetation cover along a climatological gradient. ISPRS Journal of Photogrammetry and Remote Sensing. 49, 1-8.
- Shoshany, M., Kutiel, P. and Lavee, H., 1995, Seasonal vegetation cover changes as indicators of soil types along a climatological gradient: a mutual study of environmental patterns and controls using remote sensing. Int. J. of Remote Sensing, 16, 2137 - 2151.
- Kutiel, P., Lavee, H., and Shoshany, M., 1995, The influence of a climatic gradient upon vegetation dynamicsalongaMediterraneanaridtransect.J.of Biogeography.22,1065-1071.
- Shoshany M. Kutiel P. & Lavee H. ,1996, Monitoring temporal vegetation cover changes in Mediterranean and arid ecosystem using a remote sensing technique: case study of the Judean mountain and the Judean desert. Journal of Arid Environment, 32, 1-13.
- Shoshany, M., and Svoray, T., 2002, Multi-date adaptive spectral unmixing and its application for the analysis of Ecosystems’ transition along a climatic gradient. Remote Sensing of the Environment. 81, 1-16
- Shoshany, M., 2012b, Desert Threshold Identification by Maximizing Potential Instability in Soil and Shrubs' Patterns: A remote sensing study. Land Degradation and Development, 23, 331- 338.
These Studies utilized the techniques developed in earlier works:
- Shoshany M. and Degani A., 1992, Shoreline detection by digital image processing of aerial photography. Journal of Coastal Research, 8 (1), 29-34.
- Shoshany, M., Aminov, R., and Goldreich, Y., 1994, The extraction of roof tops from thermal ￼￼￼imagery for analyzing the urban heat island structure. Geocarto International 9(4). 61-69.