A simulation experiment of vegetation and soils postpyrogenic restoration in Russia

Abstract

Russian forests have abundant natural resources and perform global ecological functions, as a carbon dioxide sink. As a result of climate warming (as one of the possible scenarios) forest fire hazard increases [1].

Pyrogenic factor is increasingly the cause of damage to a large area of natural landscapes, including both terrestrial and aquatic ecosystems. Being of the relatively rare natural phenomenons in the past, the fires are moving into the category of catastrophic and unpredictable events, which in the recent years connected with modern climatic changes and with the problems of environmental management of forestry. The main substantial matter of pyrogenic effects on the border of atmospere-lithospere is soil organic matter, which changes under the fire effect radically and participates in regulation of ecosystem exogenic stability. Therefore, it is necessary to estimate a balance and dynamics of carbon stocks in forest ecosystems as a result of wildfires. This problem can be solved by means of a system of carbon and nitrogen biological cycle models in forest ecosystems, which has already been used for a comparative analysis of wildfires impact on forest areas in Russia and Canada.

Objects of the research are postpyrogenic soils characterized by formation of specific charcoal horizon with increased portion of postfire organic matter near Togljatty city (Samara region, Russia) affected by spontaneous forest fires in 2010 [2].

Carrying out the computational experiments with the ecosystem model EFIMOD can be useful in terms of probabilistic short-term forecasts creation of 5-10-15 years and in-situ observations tests. Simulation of the cumulative effects of repeated fire cycles over 140-years showed that one fire did not affect growing stock but decreased SOM by about 10%, and that three fires reduced the growing stock by 9% and decreased SOM by about 30%. Forest fires led to the significant loss of soil carbon (C), as well as nitrogen (N) which is a principal limiting factor in forest ecosystems of boreal and temperate ecozones. The effect of repeated fire cycles on land degradation is similar to that of soil erosion, through the loss of soil C and N. From a silvicultural perspective, the effect of fires is generally considered positive (e.g., promotion of seedlings establishment, removing of fuel from soil surface), however, this study concluded that repeated fire cycles can have a negative effect on forest ecosystems by reducing long-term soil productivity.

Modeling the dynamics of forest ecosystems succession and reforestation processes is an important part of studying wildfires impact on soil cover, because it represents an essential element of forestry activities designing focused on maintaining of the forest ecosystems stability.

This study was a contribution to the RussianScience Foundation, prject No 17-16-01030

Key words: soils, wildfires, postfire soil development, ash, , EFIMOD