The article is dedicated to the blessed memory of the outstanding scientist, teacher-mentor, professor, doctor of biological sciences Tatyana Alekseevna Sokolova. The scientific community knows and will always remember Tatyana Alekseevna as an authoritative specialist in the field of soil science and mineralogy. The scope of her interests in the scientific and educational system is wide and diverse. One of the fundamental areas of work is the problems of soil acidity. The presented material contains some components of the creative heritage of T.A. Sokolova in the aspect of current research and prospects for its development. In particular, attention is drawn to the nature of the acidity of highly acidic soils (pHKCl <3.3, pHH2O <4.4). The specificity of the formation of the acid-base state of these objects is shown using soils of different genesis as an example. The reasons for the low accuracy and reproducibility of the results of measuring the exchangeable acidity of highly acidic soils are revealed. Recommendations for improving the quality of measurements are given.

Anthropogenic factors of soil acidification/alkalinization change the natural protolytic balance of soils. The degree and direction of such changes are determined by the magnitude of the acid/alkaline load and soil stability - acid-base buffering capacity. The article summarizes the results of a study of the sources of buffering capacity of taiga soils in the European north-east of Russia. It is shown that the buffering capacity of soils developing in the same climatic conditions, as well as similar in lithological features, depends on the hydrological conditions of the microrelief elements, and accordingly on the composition and functioning of biocenoses. The variability of the nature and structure of soil buffering is revealed in the thickness of the most active action of biotic factors - in organogenic and eluvial horizons. The similarity of illuvial horizons of genetically different and geographically isolated soils is due to their insignificant transformation by soil processes, which is manifested in the absence or reduced content of direct products of soil formation - organic, Al-, Fe-organic compounds, minerals of the soil chlorite group. The materials can be used for soil-chemical monitoring and for predicting soil changes under the influence of pollution by acidic and alkaline compounds.