Physico-chemical properties and micromorphology of the microbiotic crusts (lichen) on loess hills in Alagol area, Golestan Province

The aim of this study was to investigate the physico-chemical, biological properties and micromorphology of the soils covered by lichen (biologic crust) in Alagol area of Golestan Province. In-three points, pairwise samples were collected from 0-10 cm depth with eight replications and also undisturbed samples for micromorphological studies in Alagol pastures. These were selected randomly and were the common borders of the uncovered and lichen covered soils. Soils samples were analyzed and some properties such as texture, organic matter, CEC, bulk density and mean weight diameter were determined. In addition the micromorphological study of some pairs of soil samples were determined by polarized microscope. Results of analysis indicated that soil organic carbon content increased markedly in the covered soils compared to the uncovered one. Aggregate stability also increased about three folds in soils covered with lichen. Micromorphological studies showed that uncovered soil had a weak and massive microstructure but soils covered by biocrusts showed strongly developed blocky microstructure. The soils covered with lichen showed two types of b-fabric, crystallitic and speckled. While the uncovered soils was dominant with crystallitic b-fabric. The soils covered with lichen showed various layers of the accumulation of carbonate the form of micritic Polysaccharide excretions of lichen bind soil particles together and increased aggregate stability.