How do forest fires affect soil greenhouse gas emissions in upland boreal forests? A review

New review paper by Ribeiro-Kumara et al., 2020 focuses on four different standpoints to explore the effects of fire on greenhouse gas (GHG) fluxes in boreal forests: fire severity, time after fire, physical environment, and temperature sensitivity (Q10). High-severity fires have stronger effects on soil CO2 efflux than low-severity fire. Soil CO2 efflux generally increases as a function of time after fire, with the re-establishment of vegetation cover governing the recovery of soil CO2 emissions. Fire effects on soil CO2 emissions in permafrost areas are tightly linked to fire-induced changes in SOM throughout the soil profile. The fire-severity effects on CH4 and N2O fluxes are still uncertain, since very few studies have been conducted after low-severity fires. Upland boreal forests in permafrost and nonpermafrost areas seem to act as CH4 sinks during the fire succession, although a strong trend has not yet been identified. The fire effects on CH4 fluxes may be associated with soil moisture and diffusivity conditions at the time of fire and active layer depth after fire. The direction of the N2O fluxes across a fire succession is still uncertain, while soil temperature is the most studied driver for N2O emissions.

Molecular composition of soil dissolved organic matter in recently-burned and long-unburned boreal forests

New paper by Ide et al., 2020 investigates how forest fires can change the quality of dissolved organic matter (DOM) in soils, and consequently have an influence on biogeochemical cycles in forest ecosystems. To clarify the effects of fire on the chemical composition of DOM in boreal forest soils, the molecular composition of soil DOM was compared between recently-burned and long-unburned boreal forests (6 and 156 years since the last fire, respectively) in Finnish Lapland.

Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry revealed that there were no significant differences in species, average molecular weight or the number of molecular compounds detected between the recently-burned and long-unburned forests. However, the number of compounds with condensed aromatic structures tended to be larger in the recently-burned forest, whereas the numbers of proteins and carbohydrates not shared between the two forests were significantly smaller. The study suggests that fire not only generated several species of dissolved black carbon, but also caused burned plant residues, which supplied diverse lignin-like molecules in the recently-burned forest soils and led to the number of molecular species being comparable to that in the long-unburned forest soils.

Burning experiment 2020

New attempt! Book the dates!

We are currently planning a prescribed fire (burning experiment) close to Evo, Finland.

This will be the test burning, to prepare for the bigger campaign in summer of 2021. Currently the plan is to establish experimental burning areas in 70-80 year old Scots pine stands (sandy soils), and the burning should take place between 15.05 – 15.06.2020.

We are aiming surface fires with two different intensities – two different treatments with burning temperatures around 300 degrees and 600 degrees (acheaved by biomass treatment).

The aim of the experimental burning is to test the effect of different fire intensities on GHG and BVOC emissions from the soil, on soil organic matter quantity and quality, on microbial biomass and composition, on pyrogenic carbon (char) creation, etc. Also to test different measuring equipment (temperature sensors, low cost CH4 sensors, etc.).

The experiment is planned in collaboration with Häme University of Applied Sciences (HAMK), Institute for Atmospheric and Earth System Research/Forest Sciences (Disturbance and biogeochemistry team) in University of Helsinki, University of Eastern Finland (Department of Environmental Science, Kuopio and Joensuu), LUKE (Jokioinen), Emergency Services Academy Finland (Pelastusopisto).

Wildfire effects on BVOC emissions from boreal forest floor on permafrost soil in Siberia

New paper by Zhang-Turpinen et al. studied the long-term effects of wildfire on forest floor BVOC emission rates along a wildfire chronosequence in a Larix gmelinii forest in central Siberia – how forest wildfires and the subsequent succession of ground vegetation, as well as changes in the availability of SOM along with the deepened and recovered active layer, influence BVOC emission rates.

The results showed that forest floor acted as source of a large number of BVOCs in all forest age classes. Monoterpenes were the most abundant BVOC group in all age classes. The total BVOC emission rates measured from the 23- and >100-year-old areas were ca. 2.6 times higher than the emissions from the 1-year-old area. Lower emissions were related to a decrease in plant coverage and microbial decomposition of SOM after wildfire. The results also showed that forest wildfires play an important indirect role in regulating the amount and composition of BVOC emissions from post-fire originated boreal forest floor. This could have a substantial effect on BVOC emissions if the frequency of forest wildfires increases in the future as a result of climate warming.

Long-term effects of forest fires on soil greenhouse gas emissions and extracellular enzyme activities in a hemiboreal forest

New paper by Ribeiro –Kumara et al. studied how fire-induced changes to soil properties and vegetation affect gas exchange of CO2, CH4 and N2O in the soil–atmosphere interface of hemiboreal Scots pine forests in Estonia.

The results showed a reduction of soil CO2 efflux at the beginning of the fire chronosequence, but no changes to CH4 or N2O fluxes related to time after fire. Soil respiration responded differently to changes in soil temperature and soil moisture across the fire chronosequence. Conversely, CH4 and N2O fluxes only responded to changes in soil temperature. Recovery of soil respiration in the long term was associated with the moderate effect of fire on enzyme activity, the above- and below-ground litter C input, and the re-establishment of overstorey vegetation. Enzyme activity and decomposition inside the litter bags were especially good indicators of the role of the microbiota on the initial recovery of soil respiration prior to the re-establishment of the vegetation

Despite its limitations, the study certainly adds to our understanding of the importance and complexity of both above- and below-ground (vegetation and microbiota) responses to fire-induced changes of soil physicochemical properties for determining the temporal variability of gas exchange.

Reducing the effects of forest management to inland waters (REFORMWATER)

REFORMWATER- Reducing the effects of forest management to inland waters, is a new project lead by Prof. J. Pumpanen (WaterWorks2017 ERA-NET Cofund, April 1, 2019 – March 3, 2022).

The aim of this project is to quantify the effects of current management practices (harvesting and subsequent ditch network maintenance) on peatland forests on the transport of dissolved organic matter to aquatic systems and consequent greenhouse gas emissions. Also alternative forest management techiques such as continuous cover forestry to reduce the DOM load to inland waters will be studied.

The project is based on field experiments where the effects of different forest management techniques on water quality will be tested. Detailed laboratory experiments for determining the effect of DOM quality on greenhouse gas production from aquatic systems will be performed.

The project is based on multidisciplinary collaboration between foresters, soil scientists and limnologists from Finland (University of Eastern Finland, University of Helsinki), Sweden (Swedish University of Agricultural Sciences, Umeå)), Estonia (University of Tartu) and Ireland (University College Dublin.

Fieldworks in Finland (Paroninkorpi), 21-22. October 2019


From 6 – 9th October 2019 FireLinks meeting in Sofia

From 06. – 07. October Work Group 3 (Fire Effects on Soil) meeting „Soils and forest fires today. Science and Society“ and from 08.-09. October First General Assembly & 2nd MC meeting were taking place in Soffia, Bulgaria.

FIRElinks (COST Action CA18135) will develop the EU-spanning network of scientists and practitioners involved in forest fire research and land management and connect communities from different scientific and geographic backgrounds, allowing the discussion of different experiences and the emergence of new approaches to fire research.

COST Action CA18135, FIRElinks

Our team members Prof. Jukka Pumpanen (University of Eastern Finland) and Dr. Kajar Köster (University of Helsinki) are members of the Management Committee (country representatives) of the new COST Action CA18135, Fire in the Earth System: Science & Society (FIRElinks).

Dr Egle Köster (University of Helsinki) and Ms Christine Ribeiro-Kumara (University of Helsinki) are acting as Management Committee Substitutes.

FIRElinks will develop the EU-spanning network of scientists and practitioners involved in forest fire research and land management with backgrounds such as fire dynamics, fire risk management, fire effects on vegetation, fauna, soil and water, and socio-economic, historical, geographical, political perception and land management approaches. It will connect communities from different scientific and geographic backgrounds, allowing the discussion of different experiences and the emergence of new approaches to fire research.

The main aim of FIRElinks is to power synergistic collaborations between European research groups and stakeholders with the objective to synthesise the existing knowledge and expertise, and to define a concerted research agenda which promotes an integrated approach to create fire-resilient landscapes, taking into account biological, biochemical and-physical, but also socio-economic, historical, geographical, sociological, perception and policy constraints. This is an urgent societal need due to expected further intensification and geographical spreading of wildfire regimes under Global Change.

Temperature sensitivity of soil organic matter decomposition after forest fire in Canadian permafrost region.

New paper by Aaltonen et al., 2019 determines how heterotrophic soil respiration (Rh), originating from the decomposition of SOM, and the Q10 of this process vary between different depths over the years following a forest fire in permafrost-affected soils. How the microbial biomass and qCO2 are affected by the fire, and what are the most important factors affecting the Q10 of SOM decomposition.

The results indicate that forest fires may facilitate the decomposition of permafrost SOM by increasing the active layer depth, but on the same time fire increased the temperature sensitivity of decomposition. The SOM in the permafrost surface was less temperature sensitive than the SOM in the soil surface. The post-fire decreases in ground vegetation were reflected in the SOM temperature sensitivity shortly after fire but seemed to return to original levels with forest succession.

The fire also increased the microbial qCO2, and these changes partly explain the lack of significant decrease in heterotrophic soil respiration after fire, as the microbes may use more C for respiration in the recently burned areas compared with the older areas. Even though fires increased the active layer depth, the decrease in SOM quality caused by fire may limit the decomposition rate to some degree.