The effect of environmental and pedogenic factors on soil diversity in Kerman and Lalehzar regions

Abstract
Background and objectives: Study of soil diversity leads to an increase of awareness of the conditions and factors creating of diversity in the region. During soil evolution, soil development occurred by progressive and regressive pedogenic pathways, and exogenic and endogenic factors, processes and conditions and consequently, it leads to the formation of diversity soils. Effect and intensity of exogenic (environmental) and endogenic (pedogenic processes) factors on soil diversity is distinct in different environments. This study explores the efficiency of diversity indices in expression of soil diversity in environments with external and internal factors.
Materials and methods: The landforms differentiation was done by Google Earth Software and field excursion and then, 23 profiles were drilled, described and sampled. Some soil properties including pH, EC, CEC, soil texture, percentage of gypsum, lime and organic matter were measured and the soils were classified by using soil temperature and moisture regime and USDA (2014). Separation of two study areas; Kerman and Lalehzar, was done by using digital elevation map and hydrological properties and also, ENVI and ARCMAP softwares. Based on the indices of Domartin, Gower and Jaccard, dissimilarity of soil forming factors of climate, topography and parent material was identified in Kerman and Lalehzar regions, respectively. The diversity indices of richness, evenness, Shannon and Simpson were calculated. Then, comparison of soil diversity in two study regions was carried out by using the classical statistics in a specified confidence limits. Finally, the relationship between sample size and landforms area was used for identification of the relative importance of internal and external resources in soil diversity.
Results: The results showed the presence of different and diverse soils in both areas. Sharp difference of soil forming factors climate, topography and parent material has led to formation of different soils in two study areas. Histosols and Mollisols are locally composed in Lalehzar region. The results showed that soil diversity increase according to soil taxonomy hierarchy in USDA system. In different landforms, the maximum diversity was observed in piedmont plain and in soil family level. Despite the ability of Shannon and Simpson indices to display soil diversity based on taxonomic hierarchy, Simpson index has statistically more performance than to Shannon index. The Simpson diversity index was significantly difference in two study areas. The ratio of bi/b obtained 1.26 for Kerman and 0.46 for Lalehzar, that is stated the effect of inherent and environmental factors on soil evolution in Kerman and Lalehzar, respectively.
Conclusion: In large spatial scale, the effect of environmental factors on soil evolution is more clear than inherent factors and with decreasing of spatial scale, the effect of inherent factors is specified. Diversity indices are powerful in the presentation of quantitatively soil diversity and provide useful information for soil mapping and optimum soil management.