Humus forms and the most important factors affecting its changes in mixed beech forest (case study: Shast Kalate forest of Gorgan)

This study aimed to investigate the Humus forms and the most important factors affecting its changes in mixed beech forest in Shast Kalate (Dr. Bahram Nia) experimental forest. Therefore 32 gaps with different sizes have been selected in aforementioned parcel. In each gap 5 humus profiles were considered. The same soil sampling strategy was used in an understory point 20 meters far from gap edge. Then humus form of each profile was determined based on morphological method. Results showed that totally 9 different humus forms were observed in the study area. Mull order with frequency of 70.6 % and suborder of dysmull with the frequency of 37.8% were dominant in the study area. The average thicknesses of organic horizons in gaps were 1.7, 0.3 and 0.1 cm and in understory 2.3, 0.9 and 0.48 cm for L, F and H respectively. There was a statistically significant difference between humus forms in gaps and in understory. Also gap size and land form significantly affected the humus. The average of holorganic horizon biomass in gaps was about 486 and in understory was 686 gr/m2. The results can be considered as a pattern in prediction of close-to-nature silvicultural system effects on forest humus form state.