Water-extractable organic matter and biological activity of Retisol of a small water-shed after snowmelt

Abstract

The aim of the study was to evaluate qualitative and quantitative characteristics of water-extractable organic matter of Retisol after snowmelt at the small watershed, as related to soil mesorelief location and biological activity.

Location and time of the study. Near Bukholovo village, Shakhovskaya municipal district, Moscow region, Russia, 09.04.2023 (sampling).

Methods. We measured pH, water-extractable organic carbon (WEOC) and nitrogen content, substrate-induced and basal soil respiration and estimated soil prokaryotes and fungi biomass using luminescent microscopy.  To characterize extracted 0rganic matter we used spectroscopy in the ultraviolet and visible ranges and fluorescence spectroscopy.

Results. In soil samples, that were collected already dry after the snowmelt and before the start of active growing, soil water content was found to increase down the slope, whereas the content of WEOC and WEON decreased with increasing moisture. Analysis of optical characteristics showed that increasing soil WEOC its extent of microbial transformation decreased. This is accompanied by the decrease in molecular mass and activity of aromatic and the donor-acceptor structures. The basal respiration increased with increased soil moisture.

Conclusions. The finding that dissolved organic matter in dried below field moisture capacity Retisol after snowmelt was inversely related to soil moisture can be explained by its active decomposition with increasing moisture, the effect of inter lysates and the absence of the influence of higher plants.