NITROGEN-FIXING AND DENITRIFYING ACTIVITIES IN SOILS OF UNDISTURBED SOUTHERN TAIGA ECOSYSTEMS

摘要

Productivity of most natural forests in the temperate zone is limited by nitrogen deficiency. This attracts interest to the study of nitrogen cycle, including nitrogen fixation and denitrification as the input and output items of the nitrogen budget in ecosystems. Taking into account that if, according to some authors [1], significant losses of mineral nitrogen are due to the development of soils, the problem of soil supply with potentially available nitrogen forms gains in importance. In this regard, most attention should be given to forest ecosystems, which have significant potential for the fixation and release of nitrogen. They play the major role in global biogeochemical cycles [2]. Nitrogen reserves in undisturbed forest biogeocenoses reflectthe capacity of natural ecosystems to accumulate and further transform nitrogen in the soil. It follows from the available literature data that nitrogen, being an essential biophilic element, most rapidly responses to changes in soil properties. The symbiotic and nonsymbiotic fixation of molecular nitrogen is one of the main sources of involving bound nitrogen into the nitrogen cycle [3], and nitrification and denitrification are the essential processes of its removal from ecosystems. The aim of this work was to assess the activities of nitrogen fixation and denitrification in soils of undisturbed southern taiga ecosystems.