Transformation of soil organic matter by microarthropod communities in technogenic soils of Kuzbass

The aim of our investigation was to compare soil organic matter transformation (humification and mineralization) in technogenic substrates exposed to the presence and absence of microarthropods under different moisture conditions. We supposed that the content of humic and fulvic acids would increase in the samples protected from microarthropod colonization because more microorganisms grow in such samples. We carried out an investigation in the forest-steppe zone of Kemerovo region (in vicinities of Listvyagi village near Listvyanskii opencast coal mine (53°40' N, 86°54' E). Study sites were situated in the coil quarry abandoned about 30 years ago. One of them was situated in the pit bottom on the inner lake shore and the other - on the inner pit slope 50 m far and 20 m up from the lake. We used two kinds of soil substrate: technogenic eluvium and loess-like loam. Substrates were defaunized, passed through soil sieves and placed into textile bags with mesh 0.06 mm. One set of bags was completely made of the microarthropod-proof gauze, while bags of the other set had a window (1/4 of the total area) of a coarse gauze (1.7 mm mesh), which prevented the access of mesogeobionts but allowed soil recolonization by microarthropods. The bags were placed in the soil for 125 days. In initial substrates (control) and in exposed samples we measured the content of general organic carbon (C) and fractions of humic and fulvic acids by method of IV Tyurin. The content of organic carbon in bags of all types which were placed on the slope increased during the experiment. On the contrary, general C content decreased in the bags placed near the lake shore (compared with control samples and with samples placed on the slope). We observed an increase in fulvic acids content in experimental samples, especially from the lake shore (up to 1/3 more). The difference is especially big (twice) in the 3rd fraction of fulvic acids which is more active and has a quicker reaction to the change of soil genesis. General content of organic C decreased in technogenic eluvium bags and increased in loess-like loam bags. Humic acids content in technogenic eluvium bags decreased 2 times. Fulvic acids content increased twice in technogenic eluvium bags and had no change in loess-like loam bags. We determined that the disturbance of microarthropod community structure had negative impact on intensiveness of humification process. Our hypothesis was right that the restriction of microarthropod access to substrates leads to a change in humus fraction proportion, increasing fulvic acids content and fulvic humus formation. We proved that the presence of microarthropods shifted the process of organic substance destruction to humification. Our experiment showed that technogenic eluvium had a quicker reaction to the absence of microarthropods. This reaction is greater than in loess-like loam. During the experiment we showed that in the moist soil of the lake shore, processes of soil formation and microbial activity are higher than in slope soils. Soils of technogenic landscapes are very young and processes of soil formation in them are weakly regulated, so any kind of change in micro-and mesofaunal comunities are able to turn the humification and mineralization processes to the direction unusual for a certain latitudinal zone.

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