Lukas Kohl

• PhD
• Senior Researcher at University of Eastern Finland

Aerenchymatic transport is an important mechanism through which plants affect methane (CH4) emissions from peatlands. Controlling environmental factors and the effects of plant phenology remain, however, uncertain. We identified factors controlling seasonal CH4 flux rate and investigated transport efficiency (flux rate per unit of rhizospheric pore...

Arctic wetlands are known methane (CH4) emitters but recent studies suggest that the Arctic CH4 sink strength may be underestimated. Here we explore the capacity of well-drained Arctic soils to consume atmospheric CH4 using >40,000 hourly flux observations and spatially distributed flux measurements from 4 sites and 14 surface types. While consumpt...

Methane emissions from plant foliage may play an important role in the global methane cycle, but their size and the underlying source processes remain poorly understood. Here, we quantify methane fluxes from the shoots of Scots pine trees, a dominant tree species in boreal forests, to identify source processes and environmental drivers, and we eval...

Plant-mediated CH 4 transport (PMT) is the dominant pathway through which soil-produced CH 4 can escape into the atmosphere and thus plays an important role in controlling ecosystem CH 4 emission. PMT is affected by abiotic and biotic factors simultaneously , and the effects of biotic factors, such as the dominant plant species and their traits, ca...

Shoot‐level emissions of aerobically produced methane (CH4) may be an overlooked source of tree‐derived CH4, but insufficient understanding of the interactions between their environmental and physiological drivers still prevents the reliable upscaling of canopy CH4 fluxes. We utilised a novel automated chamber system to continuously measure CH4 flu...

Background and Aims Methane (CH4) fluxes at peatland plant surfaces are net results of transport of soil-produced CH4 and within-plant CH4 production and consumption, yet factors and processes controlling these fluxes remain unclear. We aimed to assess the effects of seasonality, environmental variables, and CH4 cycling microbes on CH4 fluxes from...

Peat pore network architecture is a key determinant of water retention and gas transport properties, and has therefore been hypothesized to control redox conditions in and greenhouse gas emissions from peat soils. Yet, experimental proof of the impact of the pore network structure on biogeochemical reactions remains scarce. Here, we report on a 13...

Background and Aims Methane (CH4) fluxes at peatland plant surfaces are the net result of transport of soil-produced CH4 and within-plant CH4 production and consumption, yet factors and processes controlling these fluxes remain unclear. We aimed to assess the effects of environmental variables, seasonality and CH4 cycling microbes in CH4 fluxes fro...

The fluids at black schist-rich bedrock in the Fennoscandian shield have been shown to carry extensive methane (Kietäväinen and Purkamo 2015, Kietäväinen et al. 2017). The sources of methane, abiotic, microbial, thermogenic, or their mixtures, are not well understood (Etiope and Sherwood Lollar 2013, Douglas et al. 2017). While previous field and l...

Methane (CH4) fluxes at plant surfaces are the net result of transport of soil-produced CH4 and within-plant CH4 production and consumption, yet factors and processes controlling these fluxes remain unclear. We conducted high-frequency automated CH4 flux measurements from shoots of Carex rostrata (sedge), Menyanthes trifoliata (forb) and shrubs (Be...

The transport processes of methane (CH 4) in tree stems remain largely unknown, although they are critical in assessing the whole-forest CH4 dynamics. We used a physically based dynamic model to study the spatial and diurnal dynamics of stem CH 4 transport and fluxes. We parameterised the model using data from laboratory experiments with Pinus sylv...

Nutrient pollution has increased plant litter nutrient concentrations in many ecosystems, which may profoundly impact litter decomposition and change the chemical composition of litter inputs to soils. Here, we report on a mesocosm experiment to study how variations in the nitrogen (N) and phosphorus (P) concentrations in Fagus sylvatica (European...

Peatlands are globally significant carbon stocks and may become major sources of the greenhouse gases (GHGs) carbon dioxide and methane in a changing climate and under anthropogenic management pressure. Diffusion is the dominant gas transport mechanism in peat; therefore, a proper knowledge of the soil gas diffusion coefficient is important for the...

Peatlands are globally significant carbon stocks and may become major sources of greenhouse gasses (GHG) carbon dioxide and methane in changing climate and under anthropogenic management pressure. Diffusion is the dominant gas transport mechanism in peat, and therefore, a proper knowledge of the soil gas diffusion coefficient is important for the e...

Plants are recognized as sources of aerobically produced methane (CH4), but the seasonality, environmental drivers and significance of CH4 emissions from the canopies of evergreen boreal trees remain poorly understood. We measured the CH4 fluxes from the shoots of Pinus sylvestris (Scots pine) and Picea abies (Norway spruce) saplings in a static, n...

Peatlands are important natural sources of atmospheric methane (CH4) emissions. The production and emission of CH4 are strongly influenced by the diffusion of oxygen into the soil and of CH4 from the soil to the atmosphere, respectively. This diffusion, in turn, is controlled by the structure of macropore networks. The characterization of peat pore...

Authorship conflicts are a common occurrence in academic publishing, and they can have serious implications for the careers and well-being of the involved researchers as well as the collective success of research organizations. In addition to not inviting relevant contributors to co-author a paper, the order of authors as well as honorary, gift, an...

Peatlands are important natural sources of atmospheric methane (CH4) emissions. The emissions are strongly influenced by the diffusion of oxygen into the soil and of CH4 from the soil to the atmosphere. This diffusion, in turn, is controlled by the structure of macropore networks. The characterization of peat pore structure and connectivity through...

House dust is an important medium for exposure to persistent pollutants, such as metals. Detailed characterization of metal composition is needed to identify sources and potential health impacts of exposure. In this study we show that specific metals in dust dominate in different locations within residential homes in a mid-size Canadian city (Fort...

Authorship conflicts are a common occurrence in academic publishing, and they can have serious implications on the careers and well-being of the involved researchers, as well as the collective success of research organizations. In addition to not inviting relevant contributors to co-author a manuscript, the order of authors, as well as honorary, gi...

Plant shoots can act as sources or sinks of trace gases including methane and nitrous oxide. Accurate measurements of these trace gas fluxes require enclosing of shoots in closed non-steady-state chambers. Due to plant physiological activity, this type of enclosure, however, leads to CO2 depletion in the enclosed air volume, condensation of transpi...

Plant shoots can act as sources or sinks of trace gases including methane and nitrous oxide. Accurate measurementsof these trace gas fluxes require enclosing of shoots in closed non-steady state chambers. Due to plant physiological activity, this type of enclosures, however, lead to CO2 depletion in the enclosed air volume, condensation of transpir...

Plant litter chemistry is altered during decomposition but it remains unknown if these alterations, and thus the composition of residual litter, will change in response to climate. Selective microbial mineralization of litter components and the accumulation of microbial necromass can drive litter compositional change, but the extent to which these...

Volatile organic compounds (VOCs) play an essential role in climate change and air pollution by modulating tropospheric oxidation capacity and providing precursors for ozone and aerosol formation. Arctic permafrost buries large quantities of frozen soil carbon, which could be released as VOCs with permafrost thawing or collapsing as a consequence o...

Studies that quantify plant methane (CH4) emission rely on the accurate measurement of small changes in the mixing ratio of CH4 that coincide with much larger changes in the mixing ratio of volatile organic compounds (VOCs). Here, we assessed whether 11 commonly occurring VOCs (e.g. methanol, α- and β-pinene, Δ3-carene) interfered with the quantita...

Studies that quantify plant methane (CH4) emission rely on the accurate measurement of small changes CH4 concentrations that coincide with much larger changes in the concentration of volatile organic compounds (VOCs). Here, we assessed if 11 commonly occurring VOCs (e.g., methanol, α- and β-pinene, ∆3-carene) interfered with CH4 concentrations meas...

Plain Language Summary Wildfires release large amounts of toxic pollutants like heavy metals and polycyclic aromatic hydrocarbons. So far, it remains unknown if and how long these pollutants stay in local houses after a fire. We collected house dust samples from 64 houses in Fort McMurray (Alberta, Canada), where a wildfire forced the evacuation of...

Since 2012, the scallop fishery in Port au Port Bay, Newfoundland, Canada has experienced a drastic decline, while no decline was observed in adjacent St. George's Bay. Local fishermen have raised concerns about an abandoned oil exploration well in the Port au Port Bay. This study investigated the potential impact of petroleum hydrocarbons on sedim...

Warmer climates have been associated with reduced bioreactivity of soil organic matter (SOM) typically attributed to increased diagenesis; the combined biological and physiochemical transformation of SOM. Additionally, cross site studies have indicated that ecosystem regime shifts, associated with long-term climate warming, can affect SOM propertie...

Second Deep Carbon Observatory Summer School; Yellowstone National Park, Montana and Wyoming, 23–28 July 2016

In 2013 the scallop fishery in Port au Port Bay, Newfoundland began to drastically decline. The cause of this decline is still unknown; however, several abandoned oil exploration wells that were leaking an oily substance have been identified around the bay. This project investigated whether the decline of the scallop fishery could be related to con...

Present-day serpentinization generates groundwaters with conditions (pH > 11, Eh < -550mV) favorable for the microbial and abiotic production of organic compounds from inorganic precursors. Elevated concentrations of methane, C2-C6 alkanes, acetate, and formate were detected at these sites, but the microbial or abiotic origin of these compounds rem...

Soil microbial biomass is a key source of soil organic carbon (SOC), and the increasing proportion of microbially derived SOC is thought to drive the enrichment of 13 C during SOC decomposition. Yet, little is known about how the d 13 C of soil microbial biomass differs across space or time, or with the composition of the microbial community. Varia...

Ultra-basic reducing springs at continental sites of serpentinization act as portals into the biogeochemistry of a subsurface environment with H2 and CH4 present. Very little, however, is known about the carbon substrate utilization, energy sources, and metabolic pathways of the microorganisms that live in this ultra-basic environment. The potentia...

Glucans like cellulose and starch are a major source of carbon for decomposer food webs, especially during early- and intermediate-stages of decomposition. Litter quality has previously been suggested to notably influence decomposition processes as it determines the decomposability of organic material and the nutrient availability to the decomposer...

Fluvial ecosystems process large quantities of dissolved organic matter as it moves from the headwater streams to the sea. In particular, hyporheic sediments are centers of high biogeochemical reactivity due to their elevated residence time and high microbial biomass and activity. However, the interaction between organic matter and microbial dynami...