Investigation of Biodiversity of Soil Macrofauna Orders of Hornbeam Fallen Deadwood with Different Decay Rates in District 1 of Shast Kalateh Forest, Gorgan

Deadwood, at various stages of decay, serves as a diverse habitat for a wide range of species. This study investigates the diversity of macrofauna orders on fallen hornbeam deadwood with different decay classes (four classes) in district one of the Shast Kalate forest in Gorgan, Iran.

Samples were collected from 108 deadwood logs across three altitudinal ranges (200-450, 450-700, and 700-950 m a.s.l.) with three replicates for each decay class and diameter class (less than 40, 40-80, and more than 80 cm). Macrofauna were manually extracted from the deadwood and weighed to the nearest 0.001 g after identification using systematic keys. The diversity of macrofauna orders was assessed using diversity (Shannon-Wiener), evenness (Simpson), and richness (Margalef) indices.

The results revealed significant differences in mean richness, biomass diversity, and abundance of macrofauna among the different decay classes of fallen hornbeam deadwood, with higher decay intensity associated with increased macrofauna richness and diversity. The highest number of macrofauna was found in decay class four and in the 70-100 and 40-70 cm diameter classes. Macrofauna order frequency was highest in the 200-450 m altitudinal range and lowest in the 700-950 m range, with no significant difference between the first two altitudinal classes. A significant negative relationship was observed between deadwood length and macrofauna order frequency.

As altitude increased, biomass evenness increased while biomass richness decreased, suggesting that these factors counteracted each other, resulting in no significant difference in macrofauna order biomass diversity across the different altitudinal ranges.