Assessing rangeland capability in Iran using landscape function indices based on soil surface attributes

To identify the functioning of the soil-landscape system and its effects on plant growth for native rangeland the relationships between soil properties and landscape function analysis (LFA) indices and between plant growth characteristics and LFA indices were investigated. The results interpreted based on statistical analysis and expert knowledge. This research was carried out for a semi-arid rangeland in the Lar aquifer in Iran. Land stratification allowed the study area to be subdivided into Land Units, according to specified criteria including landform attributes (slope, aspect, and altitude), and vegetation type. A factorial model on the basis of a completely randomized design was used to analyse the data collected from 236 land units. The landscape function indices including nutrient cycling index, infiltration index, stability index, and landscape organization index were derived by various integrations of soil surface attributes. Landscape attributes differed from one another in their effects on the different landscape function indices. Increasing slope gradient significantly reduced all landscape function indices as well as soil organic carbon and total nitrogen percentages. Slope class exhibited highly significant interaction effects with vegetation type factors for stability, nutrient cycling, and landscape organization indices. Aspect did not significantly affect stability, infiltration, and landscape organization indices, but significantly affected the nutrient cycling index. The Duncan test indicated that north aspect (shady side) had the highest mean value (28.42) and south aspect the lowest mean value (25.57) for nutrient cycling index. These results are consistent with the effects of aspect on total soil nitrogen and soil organic carbon percentage for which the north aspect had the highest values. The values declined in the sequence east, west, and south aspects, respectively. This research indicates that the nature of native rangeland plant communities and their measures of production are closely related to nutrient cycling index.