ABSTRACT
The association between soil type and terrain is a fundamental concept in pedology. A soil’s position relative to landform has been a recognized factor in soil formation from the very earliest scientific work on the distribution of soils (e.g., see Dokuchaev’s works dating back to 1879, Jenny, 1941). The shape of the land affects how water and sediment are transported, deposited and stored as well as the aspect of the landform, which affects insolation. These landform processes in turn affect moisture balance, plant growth, and geochemistry, leading to great diversity in soils even over relatively short distances. An understanding of these processes and how they lead to soil diversity is the main basis for the qualitative mapping of soils by traditional soil survey techniques (Hudson, 1992). Such approaches typically involve field investigations and the application of a conceptual model to delineate like soils on the landscape. Worldwide, such soil surveys have greatly enhanced our understanding of soil diversity, and have provided an essential tool for land use management and soil conservation. However, in unmapped or coarsely mapped areas (such as the dry lands region of central Asia) traditional soil survey techniques may not be the best approach to increase the resolution of information, particularly when an inventory of a specific soil property is sought such as soil organic carbon (SOC). Maps made by these techniques are labor intensive and typically take up to decades to complete for large areas. Moreover, the traditional soil survey is a model of general soil diversity, not of individual soil properties. The soil survey is often not the optimal way to predict individual soil physical and geochemical properties (Webster and Beckett, 1968).
