Dynamics of humus forms and soil characteristics along a forest altitudinal gradient in Hyrcanian forest

Humus forms are good indicators of environmental conditions and thus important in forest ecological processes. Altitudinal gradients considered as natural laboratory for evaluating soil processes humus form distribution. The objective this study was to evaluate the macromorphology along an altitudinal gradient (0-2000 m a.s.l.) covered with plain forest, mixed pure forests forest-grassland ecotone, Alborz Mountains northern Iran. In total, 225 profiles were evaluated. Forest stand variables including tree density, basal area, crown height, floor physico-chemical properties biological features measured. We found that influence both distribution but different mechanisms. While (i.e., temperature, pH, CaCO3, N content, C/N microbial biomass N) significantly correlated altitude, more influenced by species composition. Particularly, abundance Mull decreased compared mountain forests, whereas frequency Amphi increased. Moreover, Oligomull Leptoamphi abundant beech while Eumacroamphi, Eumesoamphi Pachyamphi only observed forests. Such a fertility where higher values nitrogen (N), (MBN) pH at lower altitudes under altitudes.