Head: Lukina N.V.

Date: 2019-2020

Abstract: The development of the concept of biogeochemical carbon cycles is one of the most important scientific problems of fundamental nature and of great practical importance. The Paris Climate Conference, at which the delegations of 196 countries adopted the new agreement of the United Nations Framework Convention on Climate Change, confirms the extremely high relevance of assessing the contribution of forests to the sequestration of greenhouse gases. On the territory of Russia there is a mosaic of various succession stages of forests, due to the combined effect of natural and anthropogenic factors. However, the results of studies on the basis of which it is possible to draw certain conclusions about the relationship between the succession status of forests and the patterns of accumulation and dynamics of soil carbon in them are clearly not enough.

At the stage of project implementation in the period 2016-2018 we carried out:

1. comparative assessments of the level of accumulation of soil carbon in mixed coniferous-deciduous forests of the Center of the Russian Plain and the North-Western Caucasus, taking into account their succession status and in the taiga forests of north-west Russia;
2. estimates of the annual removal of organic carbon with soil waters in the northern taiga (Murmansk region) and mixed coniferous-broadleaf (Bryansk region) forests in comparison with data obtained from other studies using a similar methodology in middle taiga forests (Republic of Karelia) and coniferous deciduous forests (Moscow region);
3. estimates of the combined influence of external factors (increase in nitrogen compounds from the atmosphere, climate change, fires and forest management regimes) on phytomass production, dynamics of carbon and nitrogen stocks in forest ecosystems, including soils, and the species composition of forest stand, taking into account the taiga forests of north-west Russia and their comparison with the results of such assessments in conifer-broadleaved forests using the EFIMOD model.

This project 2019-2020 aims to solve actual problems in order to develop ideas about the relationship between the successive status of forests and carbon accumulation in forest soils. Analysis of contemporary foreign and domestic works suggests that for a deep understanding of the relationship between forest succession status and accumulation of soil carbon in forests to the most important modern research directions include:

• assessment of the role of vegetation and soil biota in the dynamics of soil carbon;
• assessment of the openness of biogeochemical cycles in forests at different stages of succession;
• model estimates and forecasts, including the combined influence of anthropogenic, biotic and abiotic factors on the accumulation of soil carbon in forests during their successional development.

Scientific objectives of the project:

1. to assess the nutrient mechanisms of carbon and nitrogen accumulation in forest soils, taking into account the mosaic pattern of forests at different stages of succession: biota (fungi and macrosprofagi), (c) regulation by woody plants of the amount of precipitation penetrating through the forest canopy and the volume of soil water;
2. to assess the changes in the openness / closure of carbon and nitrogen cycles during the successive development of forests, taking into account their mosaic structure;
3. to forecast the dynamics of accumulation of soil carbon and nitrogen, taking into account the combined influence of biogenic mechanisms, climate change and forest management regimes at different stages of succession. The objects of research were selected in coniferous-broadleaved plain (Bryansk region and Moscow region) and mountain (North-West Caucasus) forests, as well as in northern taiga forests (Murmansk region) at different stages of succession development. At each stage of the succession, the dominant elements of the forest cover mosaic in the subcrown spaces of the trees and in the windows will be highlighted, taking into account the basic concepts of the mosaic pattern of forest biogeocenoses and their individual components.

The scientific novelty of new scientific problems lies in the fact that:

1. the contribution of biogenic mechanisms, such as the influence of the quality of plant litter, soil fungi and macroscophophages, the regulation of various kinds of precipitation under tree canopy by woody plants, to the variation of soil carbon accumulation in the dominant components of the mosaic of forests at different stages of their succession development.
2. an assessment of the closure / openness of carbon and nitrogen cycles during the successive development of forests, taking into account their mosaic patterns based on isotope analysis and taking into account carbon and nitrogen inflows with precipitation and their removal with soil waters, will be given.
3. a prognosis of soil carbon dynamics will be given taking into account the combined effect of biogenic mechanisms, climate change and forest management regimes at different stages of succession using mathematical modeling methods.