Interactions between canopy gaps created by single-tree selection method and humus layer thickness (Case study: Alandan forest, Sari, Mazandaran province)

This research investigated the effect of canopy gaps created by single-tree selection method on humus layer depth within a managed oriental beech (Fagus orientalis Lipsky) stand in Hyrcanian region. To accomplish this, 16 gaps were selected in 4 classes (small, medium, large and very large) with 4 replications for each sample in a beech stand in Alandan district, Sari (Mazandaran province). Humus layer depth was measured in center and cardinal points of the gaps. In addition, humus was sampled based on composite samples for chemical experiments. The results showed a significant difference of humus thickness among gaps. The correlation coefficients indicated that the total N, P, K, organic carbon and C/N ratio were decreased with increasing humus depth. Humus layer depth in gap center was lower than that in the edge of gap, and the highest humus thickness was observed in the northern geographical aspect. In general, the result of study revealed that canopy gaps created by single-tree selection method affect the humus layer depth after 8 years, which in turn indicates the important role of gaps within forest ecosystems.