Programme de bourses "Echanges Universitaires"
Digital soil surveying: a case study in an arid region of Central Iran
Abstract
A major part of the earth has an arid or semiarid climate. Soils in many of these areas are threatened by degradation (salinization, gypsification, depletion of nutrients and erosion). Intensified agricultural land-use caused by an increasing human population is the main reason for the degradation of the soils. In transition countries, industrial development and urbanization add to the pressure on the fragile soil resources.
A necessary prerequisite for sustainable use and management of the soils is a good knowledge of their properties and their position in the landscape, i.e. the availability of good quality soil maps. Traditionally, soil scientists have compiled such maps by combining field and laboratory data on soils with their rather subjective (expert opinion) interpretation of aerial photographs and thematic maps about climate, geology, etc. Recently, more quantitative techniques have been introduced into soil surveys. These techniques rely on geostatistical regression modelling and on numerical classification. In addition to the information that has been used traditionally, terrain attributes derived from digital elevation models and remotely sensed spectral images are used for automated landform and soil classification and for predicting the properties of the soils at unsampled locations.
To provide accurate information for planning purposes the Iranian Soil Survey and the Soil Science Department of Isfahan University of Technology (IUT) launched a PhD study to explore the merits of these quantitative methods for soil surveys. In a pilot study a PhD student from IUT surveyed the soils at some 200 sites in a test area of the central Iranian plateau (Zayandeh Rud valley, Province of Isfahan). In addition to the survey data the student set up a DEM and classified the landforms numerically based on DEM terrain attributes, aerial photographs and remotely sensed spectral images.
During a six months visit to the Institute of Terrestrial Ecology (ITOE) of ETH Zurich, the PhD candidate and staff from ITOE will now geostatistically analyse the data from the test region, and they will compile maps of selected soil properties for the test region by using geostatistical kriging techniques. This complements the PhD project which is a first step to improve the quality of soil maps and to make quantitative predictions of soil properties for the area around the town of Isfahan which is under considerable pressure from urbanization and intensification of agriculture. The visit of the PhD student is supported financially by the Commission for Research Partnerships with Developing Countries (KFPE), the Network for International Development and Cooperation (NIDECO) of ETH Zurich, and the Institute of Terrestrial Ecology of ETH Zurich.
Contact
Andreas Papritz
Institute of Terrestrial Ecology
ETH Zurich
Grabenstrasse 3
CH-8952 Schlieren
Norair Toomanian
Soil Science Department
College of Agriculture
Isfahan University of Technology
84154 Isfahan, Iran