Tal Svoray 
  
The synergy of optical data with microwave backscattering model for the 
retrieval of soil and vegetation conditions in heterogeneous Mediterranean 
environment 
Tal SVORAY, Maxim SHOSHANY 
Bar-Ilan University, Israel 
Geography Department 
savorat(a)popeve.cc.biu.ac.il 
KEY WORDS: Remote Sensing, SAR, Mediterranean, Biomass, Semi-empirical modeling. 
ABSTRACT 
Estimation of soil moisture and vegetation biomass over wide regions is needed for a better understanding of 
ecological conditions and for monitoring desertification processes in fragile environments such as the Mediterranean 
region. Satellite remote sensing, with appropriate processing, could be very well suited for this task. In this work, we 
provide a multi-temporal analysis of backscatter characteristics of four major vegetation formations in Mediterranean 
regions. This analysis together with a description of the relationship between volumetric soil moisture and ERS-2 
SAR data from Mediterranean soils enabled us to adapt the water-cloud model of Attema and Ulaby (1978) to 
Mediterranean vegetation canopies. The application of the adapted model in heterogeneous plots was possible by the 
use of vegetation formation pixel fractions from Landsat TM data. The results have shown considerably good 
agreement between predicted and measured green biomass in both homogenous and heterogeneous plots. 
1 INTRODUCTION 
Regions with Mediterranean climate are being located in transition zones between humid and arid climates. In the 
Mediterranean basin these climatic conditions, together with the long and intensive use of the land, have resulted in 
complex environments. A better understanding of ecological processes in this sensitive zone and more effective 
landuse management require detailed quantitative information of vegetation and soil properties over wide regions. 
Radar remote sensing from satellites is very well suited to this task. However, currently, modeling vegetation with 
radar data is mainly being utilized for spatially homogenous vegetation layers such as: agricultural crops; forests; and 
wide grasslands and it is very limited for applications in heterogeneous areas such as exist in the Mediterranean 
region. This report contributes to increase the knowledge of using SAR data in a Mediterranean region. The objectives 
of this study are: (i) to generalize a soil moisture model for various soils along a semi-humid to semi-arid climatic 
gradient; (ii) to adapt a backscatter semi-empirical model to the conditions of the study area as representative to the 
Mediterranean region; (iii) to invert the adapted model in order to derive herbaceous vegetation green biomass 
estimations from the ERS-2 SAR backscatter. 
2 DATA 
The study area is a semi-arid phyto-geographical zone 
along a rainfall gradient with annual average between 450 
mm and 250 mm, located in the central of Israel along the 
eastern coast of the Mediterranean basin. The dominant = \ = 5 eon 
rock formation is chalk with patches of Calcrete and the i |/ 
dominant soil is Brown  Rendzina (Haploxerolls). m. 
Vegetation in this area varies from shrublands and garigue \ l. Syra 
(dominated by Quercus  calliprinos and Phillyrea Mediterranean Sea / 
latifolia), through dwarf shrubs (dominated by 
Sarcopoterium spinosum) to open areas with diverse | Israël 
grasslands vegetation (dominated by Gramineae). The 
spatial patterns represent wide range of transitional stages 
between areas of high homogeneity of mainly tall shrubs 
and grasslands with different compositions of the three 
vegetation formations. This diversity of patterns is a result 
of a long history of human activity (since the late bronze, 
approximately 5500 years ago). At the present, land use in 
this area is composed of agricultural crops and rangelands 
with controlled grazing pressures. The study area is 
characterized by wide range of "regeneration and Figure 1. The study area within a regional context. 
degradation patterns” of patches representing various 
soil-vegetation relationships, which may allow 
generalization of the methods to wider areas of transition 
between Mediterranean and arid regions. 
30° Eq 45° E\ | 
  
  
Saudi Arabia 
  
  
322 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part Bl. Amsterdam 2000. 
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