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Effect of biogenic crusts on biomass estimation in arid regions by satellite imagery


The overall aim of the proposed research is to examine current remote sensing methods to interpret correctly vegetation cover in arid and semi-arid regions that are affected by microphytic communities. This is important for early detection of drought and for developing correct rangeland management and value estimation approaches. The objectives are: to study the spectral reflectance characteristics of several types of microphytic communities; to study the spatial distribution of the biogenic crusts across the desert transition zone; to study the temporal variation of the spectral reflectance caused by biogenic crusts in different seasons; to re-examine the current methods of interpretation of vegetation indices acquired by the VEGETATION instrument, including procedure for Maximum Value Composite; to explain the mechanism of biogenic crust genesis under natural conditions, different system of land use and under protective regime; to explain interrelations between microphytic communities and higher vegetation on different succession stages. Field studies will be conducted to understand the spectral reflectance characteristics of several types of microphytic communities across desert transition zones in Kazakhstan and Turkmenistan. The study areas will be monitored concurrently by satellites to enable the evaluation of the satellites to detect such effects. An attempt will be made to explain and quantify desert artifacts on the Normalized Difference Vegetation Index (NDVI), used to quantify the state of crops over large areas, as well as a possible desert encroachment and state of natural desert rangelands. The hypotheses to be tested are: Under arid and semi-arid conditions where natural higher vegetation is sparse and covers less than 30%, the photosynthetic signal in the satellite image is caused mainly by non-vascular plants. A notable signal occurs when the microphytes are wet. As a result the NDVI can rise up to 0.30 although no photosynthetic activity of higher plants is observed.
It is assumed that the higher spectral signal from microphytes occurs across desert transition zones. In more humid regions the microphytes are masked by the spectral signal of higher plants and in more arid regions the surface is mainly covered by inorganic desert vanish such as patina. The NDVI desert artifacts which have been observed in the Sahel as well as in the Negev, Kyzylkum and Karakum Deserts could be explained by microphytic photosynthetic activity. The role of microphytic communities changes on different stages of plant successions from positive (stabilization of the sand massives) to oppressive one in climax successions.


Ben-Gurion University of the Negev
Sede Boker Campus
84990 Midreshet Ben-gurion

Participants (4)

Institute for Desert Research of the Academy of Sciences of Turkmenistan

744000 Ashgabat
Kazakh State Scientific Production Center of Land Management

480008 Almaty
Kazakh State University Al-Farabi

480078 Almaty
Martin Luther University of Halle

06108 Halle