Microbial activity and CO2 emission from young Arctics Technosols: Effect of material type

Abstract

Arctic urban ecosystems are exposed to severe climatic conditions coinciding with anthropogenic influence. Soils in Arctic cities are dominated by constructed Technosols, whose properties and functions are distinguished from natural soils by i) composition from variety of natural and artificial materials, ii) dynamic changes of chemical and biological properties, especially during the first time after construction. The present study aimed to compare the effect of the material type used for the Technosols’ construction on the soil chemical (pH, carbon (C), nitrogen (N) stocks) and microbial (microbial biomass C (MBC), basal respiration (BR), qCO₂, community level physiological profiling (CLPP)) properties, and CO2 emission during the first spring-autumn season since the development. Technosols were created in Apatity (Russian Arctic), and the initial materials were i) peat-sand (PS), ii) peat-sand-loam (PSL), iii) peat-sand-waste (PSW) that covered PS. Natural Podzol soil under coniferous forest was considered a natural reference. After 14 months, pH decreased by 1.0 units, and carbon stocks increased by 0.5–1.5 kg C m⁻². MBC, BR, and MBC/C ratio in Technosols increased two times but remained lower than in the natural reference. Technosols created on PSL had the highest MBC, half-life time (T0.5) of organic C, and the lowest qCO2. CLPP of 14-month-old Technosols was dominated by carboxylic acid consumers, similar to natural soils, and differed from the more diverse structure described for the 2-month-old Technosols. The annual CO2 emissions from PS, PSW, PSL Technosols were 229, 277, 234 g C m⁻², whereas CO₂ assimilation into lawn above- and belowground biomass was 536, 517, 591 g C m⁻². In the current climate, all Technosols were net C sinks with the highest C offset obtained for the PSL Technosols. However, the observed high temperature sensitivity of microbial respiration illustrates that rising surface temperatures can convert Arctic Technosols from C sinks to C sources.