Effect of Different Landforms on Spatial Variability and Frequency Distribution of Soil Biological Properties in Tabriz Plain

This research study was conducted in Tabriz plain with the aim of assessing the spatial variability and frequency distribution of some biological properties within and between landforms. For this purpose, a total of 98 surface soil samples (top soil) were collected according to a grid sampling design with spacing of 1000 meters between sampling points and then some biological properties (carbon biomass, microbial respiration, microbial and metabolic quotient) together with organic carbon and soil pH were analyzed. Soil variables frequency distribution showed that soil biological properties had abnormal distribution and the logarithmic transformation caused their normal distribution. Samples separation according to landform units caused their normal distribution and these properties became normal except at plain. Organic carbon and microbial respiration were moderately spatial dependent where as soil pH was strongly dependent and metabolic and microbial quotient showed no spatial dependence. Results indicated that spatial dependence of soil biological properties were much affected by non intrinsic and management factors such as land use type, tillage and irrigation. These biological variables were also strongly affected by scale and showed stronger spatial dependence by becoming larger scale. Therefore these soil properties variations could be due to changes in depositional environments or variance of pedogenic or hydrological processes in different kinds of landforms.