Effect of Wildfire on Forest Soils in Maleshevo–Pijanec Region
Date Issued
2022-06-20
Author(s)
Abstract
For the last three decades, wildfires have been a significant problem for forests and
forestry, causing great economic and environmental damage. They are common in
Malesh and Pijanec region, as well as throughout the country. In 2021, a total of 192
wildfires were recorded in North Macedonia. The big wildfire in Maleshevo–Pijanec
region occurred in the period 2-11 August 2021, estimated at 6,378 hectares of
burned oak and pine forests area. The burnt area is mostly represented by Complex
of Mollic and Umbric Leptosol, Regosol and Leptosol with 30.8% of the territory,
followed by Complex of Mollic and Umbric Leptosol with 17.4%, Complex of Albic
Livisol and Regosol with 11.2% and Chromic Luvisol on Saprolite with 9.4%. In this
research, the effects of fire on biological, chemical and physical properties of soils
are analysed. The most affected areas after the fire show increased biological activity
and an abundance of symbiosis between plants, fungi and bacteria as a result of
increased pH and release of nutrients from the ash. The fire significantly affected the
soil fauna due to the burning of the root system, so it is severely disturbed up to 2 cm
of depth, moderately disturbed up to 8 cm, partially disturbed up to 15 cm and weakly
disturbed in the deeper soil layers. Food sources for soil fauna are significantly
reduced. Occurrence of certain types of fungi has been recorded in the burned area.
The increased biological activity and the increased amount of nutrients have enabled
the accelerated multiplication of bacteria. The fire has decreased the capacity for
cation exchange (CCE). Sandy soils show lowest CCE after the fire, of 100 meq/100
g of soil in pine stands and 180 meq/100 g of soil in oak stands. Increased soil acidity
and increased soil biological activity indicate improved nitrification, especially in burnt
acid soils. The fire decreased organic carbon (C) content in soils and caused
structural changes in aliphatic compounds, while humic acids remained unchanged.
Carbonated plant debris in large quantities are accumulated on the soil surface (to a
depth of 2 cm), where it makes up 30-40% of the soil. Burnt soils are black coloured
as a result of the coal-fired organic waste and the black ash created by incomplete
combustion. Surface accumulated ash (up to 1.5 cm of depth) contains Ca, Mg, K, Si
and P. Soil water repellency is present in the burned soils, but it is not strongly
expressed and is not a limiting factor for future revitalisation activities. The aggregate
composition is significantly changed to a depth of up to 15 cm, mainly through
changes in porosity and water retention capacity. It can be concluded that it will take
relatively long time for the soils to return to their original condition.
forestry, causing great economic and environmental damage. They are common in
Malesh and Pijanec region, as well as throughout the country. In 2021, a total of 192
wildfires were recorded in North Macedonia. The big wildfire in Maleshevo–Pijanec
region occurred in the period 2-11 August 2021, estimated at 6,378 hectares of
burned oak and pine forests area. The burnt area is mostly represented by Complex
of Mollic and Umbric Leptosol, Regosol and Leptosol with 30.8% of the territory,
followed by Complex of Mollic and Umbric Leptosol with 17.4%, Complex of Albic
Livisol and Regosol with 11.2% and Chromic Luvisol on Saprolite with 9.4%. In this
research, the effects of fire on biological, chemical and physical properties of soils
are analysed. The most affected areas after the fire show increased biological activity
and an abundance of symbiosis between plants, fungi and bacteria as a result of
increased pH and release of nutrients from the ash. The fire significantly affected the
soil fauna due to the burning of the root system, so it is severely disturbed up to 2 cm
of depth, moderately disturbed up to 8 cm, partially disturbed up to 15 cm and weakly
disturbed in the deeper soil layers. Food sources for soil fauna are significantly
reduced. Occurrence of certain types of fungi has been recorded in the burned area.
The increased biological activity and the increased amount of nutrients have enabled
the accelerated multiplication of bacteria. The fire has decreased the capacity for
cation exchange (CCE). Sandy soils show lowest CCE after the fire, of 100 meq/100
g of soil in pine stands and 180 meq/100 g of soil in oak stands. Increased soil acidity
and increased soil biological activity indicate improved nitrification, especially in burnt
acid soils. The fire decreased organic carbon (C) content in soils and caused
structural changes in aliphatic compounds, while humic acids remained unchanged.
Carbonated plant debris in large quantities are accumulated on the soil surface (to a
depth of 2 cm), where it makes up 30-40% of the soil. Burnt soils are black coloured
as a result of the coal-fired organic waste and the black ash created by incomplete
combustion. Surface accumulated ash (up to 1.5 cm of depth) contains Ca, Mg, K, Si
and P. Soil water repellency is present in the burned soils, but it is not strongly
expressed and is not a limiting factor for future revitalisation activities. The aggregate
composition is significantly changed to a depth of up to 15 cm, mainly through
changes in porosity and water retention capacity. It can be concluded that it will take
relatively long time for the soils to return to their original condition.
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