Changes in Soil Total and Microbial Biomass Nitrogen in Deforested and Eroded Areas in the Western Black Sea Region of Turkey.

The microbial biomass in soil is an active and living constituent of organic matter. It is both a storage pool and a source of plant nutrients that can be used as required. In addition, each microbial indicator evaluates soil quality and health from different perspectives, which are not necessarily very different. This study was conducted to compare some physical, chemical, and biochemical characteristics of the soils of forest (S_F) and deforested (S_DE) areas located on the slopes of the Kirazlıköprü area, which was previously deforested due to dam construction in Bartın province in northwestern Turkey. Soil samples were taken from the topsoil surface (0–5 cm) to determine the microbial soil characteristics of the S_F and S_DE sites. The soil microbial biomass N (N_mic) was determined by chloroform fumigation extraction, and the C_mic/N_mic ratio and N_mic/N_total percentage were calculated using the original values. Total N, N_mic and C_mic/N_mic values are higher in the forest area. The lowest and highest total N (N_total) contents in the S_F and S_DE soils varied between 1.50 and 3.47 g kg⁻¹ and 0.91 and 1.46 g kg⁻¹, respectively. Similarly, the N_mic contents of the S_F and S_DE soils varied between 75.56 and 143.42 μg g⁻¹ and 10.40 and 75.96 μg g⁻¹, respectively. A statistical analysis revealed that the mean N_total and mean N_mic values differed (p < 0.05) in the S_F and S_DE soils. The mean C_mic/N_mic values in the S_F and S_DE soils were 8.79 (±1.65) and 5.64 (±1.09), respectively, and a statistical difference was found between the fields (p < 0.05). Our findings indicate that the soil microbial community structure varies according to the site. As a result, it can be concluded that deforestation and erosion due to dam construction in the area led to the removal of plant nutrients from the soil; deterioration in the amount and activity of microbial biomass; and, consequently, soil losses and degradation of soil quality. [ABSTRACT FROM AUTHOR]