Redox conditions of peat soils of drained swamp pine forests of Western Siberia

Abstract

We studied poorly drained sedge-sphagnum pine forests (Pinus sylvetris L.) in the southern taiga subzone of Western Siberia, drained by a network of open shallow channels 25 years ago at the time of the study (geographical coordinates 56°23′71″ N, 84°34′04″ E). The depth of standing swamp waters for three years of research averaged 23.2 ± 9.9 cm during the warm period. Soils – cultivated transitional (mesotrophic) type on powerful sedge-sphagnum peats. They are characterized by an acidic environment reaction – pH 4.0, a loose composition density of 0.10 g/cm3 and an ash content of 8.9–5.2%, decreasing with depth. The soil profile in the warm period is poorly differentiated into a zone of intense oxidative processes (0–10 cm) – 570–660 mV (median 610) and moderately oxidative (10– 30 cm) – 430–640 mV (median 590). The main direction (trend) of seasonal fluctuations of the redox potential (RP) is characterized by an average weekly acceleration of 7.2 mV with an average weekly deceleration of 0.23 mV from June to October. RP by the type of linear function is significantly associated: positively with the groundwater level (R2 = 0.65) and soil temperature (R2 = 0.56), negatively with volumetric humidity (R2 = 0.60). A significant second order parabola-type relationship of RP was revealed: negative – with Fe2+ (R2 = 0.48) and ammonium (R2 = 0.57), positive with Fe3+ (R2 = 0.39), multidirectional – with FeC (R2 = 0.55) and water-soluble organic carbon (R2 = 0.54). By the method of canonical analysis, it was found that the RP is determined by a set of hydrothermal indicators by 81 %. The volume humidity contributes the greatest weight to the conditioned effect. Various forms of iron cumulatively estimate the development of RP-reactions by 52 %, the dominant contribution belongs to Fe2+. The set of carbon and NH4+ determines the redox potential by 61 % with the largest weight of carbon in the set of characteristics.

Keywords

• seasonal trend
• paired regression models
• canonical analysis
• hydrothermal conditions
• fe3+–fe2+ system
• water-soluble carbon
• ammonium