The variability of humus forms in relation to forest cover and soil ecology in different altitudes

Humus systems are the largest part of organic carbon stock and play an important role in forest ecological processes. Elevation by influencing on the biological and non-biological properties of the forest ecosystem is an important factor for assessing the changes in the trees and distribution of humus systems. In this study, the morphological and chemical characteristics of humus forms in three altitudinal levels (500, 1000, and 1500 m.a.s.l.) and three transects which were 1000 meters apart were investigated. In each transect, 3 plots with 400 m2 area were sampled, and in each plot 5 profiles of humus (in total of 135 profiles) were examined in the central Hyrcanian forest. Humus and samples were taken and transferred to the laboratory for chemical analysis. The results showed that the presence of Iron wood (Scientific name??) and ash (Scientific name??) trees mull humus forms and soil nitrogen stock decreased by elevation increasing. Hornbeam (Scientific name??) and maple (Scientific name??) trees, organic layers' nitrogen, mesomull and leptoamphi humus forms demonstrated strong correlation with the 1000 m elevation. The number of beech trees, carbon in soil and organic layers, organic layers' thickness and humus Amphi forms showed a strong relationship with each other as well as with elevation increasing.  The effect of elevation on the composition of the trees coverage is accompanied by the variability in morphology and chemical characteristics of humus forms, so that by identifying tree species in every altitude, we can recognize the quantitative and qualitative properties of humus and soil.