Microbial respiration, microbial biomass and activity are highly sensitive to forest tree species and seasonal patterns in the Eastern Mediterranean Karst Ecosystems

Soil microbial biomass and functions are the most affected soil components by environmental changes. Therefore, determining the factors affecting soil microorganisms is very important for forest management. This study was conducted to determine the influence of forest type and seasonal variations on microbial biomass and activities in soil. For this, a total of 360 soil samples were collected (120 from each of the Black Pine, Lebanon Cedar, and Oriental Beech) during four seasons of the year in the Eastern Mediterranean Karst Mountain of Taurus, Turkey. Soil samples were used to determine soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (Cₘᵢc), microbial biomass nitrogen (Nₘᵢc), and microbial respiration (MR). With these data, the metabolic quotient (MR/Cₘᵢc ratio) and microbial quotient (qCO₂ = Cₘᵢc/SOC ratio) were calculated. Soil Cₘᵢc and Nₘᵢc were significantly higher in Cedar (789.5 ± 438 μg C g⁻¹; 305.26 ± 93 μg N g⁻¹) than in the Beech (691.8 ± 246 μg C g⁻¹; 148.18 ± 43 μg N g⁻¹) and Pine forests (659.4 ± 224 μg C g⁻¹; 130.1 ± 22 μg N g⁻¹). Microbial properties were highly sensitive to forest tree species and seasonal patterns, which can be further used as potential indicators of the effects that forest management practices may have on SOC dynamics. The three forest types showed significant differences in the seasonal Cₘᵢc and Nₘᵢc patterns, with maximum values occurring in the fall and minimum in the winter season. However, averaged across forest species, SOC did not vary among different seasons. The qCO₂ was higher in Cedar forest in the winter season and lower in the Beech forest during the spring season. These findings show that Cedar forest could be more conducive to higher microbial activity and overall soil quality than the Beech and Pine forests.