Effect of deforestation on soil organic carbon fate and pool, a case study in Mazandaran, Iran

Abstract

Deforestation and agricultural operations greatly impact soil organic carbon (SOC) and its fractions. In order to decrease carbon dioxide emissions, prevent threats to ecosystem stability, and apply efficient land use planning for sustainable soil management, it is essential to have a deep understanding of variations in soil organic carbon pools and their fractions. Soil samples were collected from six land uses of the undisturbed forest, pasture, orchard, and agricultural lands (cultivated with Oat, Maize, and three-carbon plants including wheat and soybean, which are indicated by the plant names of Oat, Maize + C3, and Maize + C3 (R) (R = rotationally)) with three replications at 0–30, 30–60, and 60–100 cm depths. The objective of this study was to evaluate the effect of land use on SOC, active carbon (AC), passive carbon (PC), dissolved organic carbon (DOC) content and pools, its fractions, carbon management index (CMI), soil respiration (SR), soil microbial biomass carbon (MBC), invertase (INV), and cellulase (CEL) enzymes activities in Dasht-e Naz region of northern Iran. Results illustrated that the different forms of organic carbon and enzyme activities were sensitive to land use change. The highest values of SOC (167.197, 39.179, 33.211 Mg ha−1), AC (24.596, 1.955, 1.637 Mg ha−1), and PC (142.6, 37.224, 31.575 Mg ha−1) pools were observed in the pasture land at all three depths. the highest value of DOC was seen in the pasture land at 0–30 and 60–100 depths and in the orchard at 30–60 cm depth. The values of SR (1.001 mg CO2 g dry soil−1 week−1), MBC (1367.7 µg organic carbon g soil−1), and CEL enzyme activity (648.04 µg glucose g dry soil−1 24 h−1) in the undisturbed forest were significantly greater relative to other land uses in 0–30 cm depth, along with significantly higher INV enzyme activity in the pasture and the orchard lands. The largest amount of SOC in 2–4.75 and 0.053–0.25 mm aggregates in all depths was related to the pasture and Maize + C3 land use, respectively. The concept of physical protection confirms the importance of aggregation in the stabilization processes of soil organic carbon, as a physical shield against microorganism attacks. The results of CMI demonstrated that the carbon storage capacity decreased due to the agricultural and orchard lands establishment in the region. Also, the change of land use towards pasture land increased the amount of organic carbon, preventing soil degradation.