Land Cover in the Nizzana Sandy Arid Ecosystem. Mapping Surface Properties with Multi-Spectral Remote Sensing Data

Importance of biocrusts in dryland monitoring using spectral indices

“…However, in contrast to previous studies, which propose the coverage of cyanobacteria-dominated biocrusts to be the main factor controlling differences in albedo between the Egyptian and Israel border (Karnieli & Tsoar, 1995;Burgheimer et al, 2006;Karnieli, 2003;, this effect was less important than the effect of vegetation cover on surface albedo. In our study vegetation cover explained 67% of albedo variance (Table 2), supporting these studies which question the relevance of biocrust coverage in the albedo contrast at the Israel-Egyptian border (Otterman, 1996;Hill, Udelhoven, Jarmer, & Yair, 2008). Moreover, and in contrast to the spectral response of homogenous cyanobacteria upon watering of the crusts (Fig.…”

“…A possible factor explaining the differences between our results and previous studies conducted in the Negev may be the differences in vegetation composition between the two regions. Similar to the NDVI and EVI, relative importance of biocrust effects on albedo, when compared with vegetation effects, increase as leaf thickness and light absorption decrease from succulent to non-succulent plants (Table S.1), which are the dominant vegetation at the Negev (Otterman, 1996;Hill et al, 2008).…”

Remote Sensing of Biological Soil Crusts at Different Scales

“…Maps of endmember abundances F j provide the convenience and intercomparability of standard land cover metrics (e.g., NDVI) while retaining benefits of physically based estimates, and they can be edited and recombined to produce thematic maps. Hill et al (2008), for example, could successfully demonstrate that SMA was capable to differentiate between important surface materials (sand, biocrusts, and mineral crusts with different silt/clay contents) on reflectancecalibrated high-spatial-resolution true-color air photos after these had been stratified into areas with and without higher plant coverage. When SMA was applied to hyperspectral imagery, the analysis of mixing residuals (which usually indicate components not represented by the set of endmembers) proved that, in addition to the occurrence of biocrusts, also senescent and woody plants were an essential part of the composite reflectance of the Nizzana dune system in Israel (Hill et al 1999), thereby confirming the results of Otterman (1996).…”

Imaging spectroscopy of changing Earth's surface: a major step toward the quantitative monitoring of land degradation and desertification

“…As an example, Hill et al [27] have successfully used this approach to map areas affected by soil degradation and erosion under subhumid conditions in Mediterranean France. Hill et al [29] have also demonstrated that spectral unmixing of reflectance signatures permits the successful identification and spatial differentiation of soil substrates and biological crusts in sandy arid ecosystems. More recently, Ben-Dor and Banin [6,7] used the full reflective spectrum to predict soil organic matter and other mineralogical and chemical soil properties based on multivariate statistics.…”

“…2), with its improved analytical capacity visà-vis lithological, soil and dry plant properties, could contribute substantially, with the support of the science community in promoting its Earth observation capabilities, to solve a number of environmental issues. The implementation of such a dedicated system in space is further justified through the success of long-term retrospective monitoring studies, the need to derive qualitative and quantitative indicators of surface properties [8,29], and the necessity to foster integrated approaches, which link surface process models with quantitative approaches in the analysis of remotely sensed data.…”