Evolution of soil organic matter qualitative composition under different land-use types in the Yaroslavl oblast (European Russia) over longstanding period

Abstract

The paper describes the postagrogenic transformation of soil organic matter (SOM). For this purpose, the results of chemodestructive fractionation (CDF), the content of chlorophylls a and b, pheophetins and carotenoids were used for the first time. To assess the state of soil algae, Margalef’s pigment index (PI) was calculated. Soils humus horizons of arable lands and fallow ones of the Poshekhonsky district of the Yaroslavl oblast of the Russian Federation were selected as objects of research. The objects were grouped into two groups that differ in the type of land use. In one of them the soil for 30–40 years remained arable (arable-arable group), other soils arable land over the same time period were transferred to the fallow (arable-fallow group). It was found that the conversation of arable soils to fallows led to: improving the state of soil algocenosis (a value of Margalef’s PI decreased), increasing of both total organic carbon and amount of soil organic matter (SOM) easily oxidized fraction, strengthening of hydrolytic processes that reduced content of carotenoids and chlorins (in particular, pheophetins and chlorophylls a and b) in SOM. When the content of total organic carbon did not exceed 1%, the conversion of arable soils to the fallows did not cause a noticeable change in the studied characteristics of soil organic matter qualitative composition.