Comparison of the abundance and diversity of soil invertebrates between managed and unmanaged compartments in the Haftkhal forests of Mazandaran

The relationship between soil invertebrates and silvicultural practices in the oriental beech forests (Fagus orientalis Lipsky), a widespread forest tree in the Hyrcanian region, is not fully understood. The diversity of soil invertebrates is a crucial variable in the ecological evaluation of managed forests. Therefore, this study aims to assess the impacts of silvicultural practices on soil invertebrates, which is essential for sustainable forest management. The soil invertebrates studied included Earthworms, Winged insects, Aranea, Pseudoscorpions, Collembola, Protura, Diplura, Diplopoda, Chilopoda, Symphyla, Pauropoda, and Isopoda. The objective was to compare the abundance and diversity of soil invertebrates between two managed (No. 8) and unmanaged (No. 36) compartments in the Haftkhal forests of Neka city, Mazandaran province.

Soil sampling was conducted in 131 ha of the studied forests using a regular random method with grid dimensions of 150 × 200 m. A cylindrical device with a cross-sectional area of 81 cm² and a depth of 10 cm was used. Twenty and thirty sampling plots were obtained in managed (No. 8) and unmanaged (No. 36) compartments, respectively. The average abundance and the average number of soil invertebrate groups per square meter were determined. Additionally, Shannon-Wiener and Simpson Indices were used to calculate soil invertebrates’ diversity, while Margalef and Sheldon indices were used to determine species richness and evenness, respectively.

The results showed that the averages of total abundance and the number of soil invertebrate groups per square meter in the managed forest (117278.70 and 7.31) had a slight decrease compared to the unmanaged forest (120167.77 and 7.62). Also, the diversity averages based on Shannon-Wiener and Simpson indices, along with the Margalef richness of soil invertebrates in the managed forest (1.890, 0.834, and 1.770), had a slight decrease compared to the unmanaged forest (1.928, 0.840, and 1.862). On the other hand, the average Sheldon evenness of soil invertebrates in the managed forest (0.935) had a slight increase compared to the unmanaged forest (0.924). Overall, road construction and exploitation operations during the two periods of the forestry plan implementation created scattered changes in the managed compartment, leading to a slight decrease in the abundance, richness, and diversity of soil invertebrates. However, the values of all the investigated variables between managed and unmanaged forests were not statistically significant (p=0.05).

This research demonstrated that forest management, utilizing the forestry method of uneven-aged mixed forest and the silviculture system of single-selection, has not significantly reduced the abundance and diversity indices of soil invertebrates in the managed forest compared to the unmanaged forest.