TES: Modelling Microbes to Predict Post-Fire Carbon Cycling in the Boreal Forest across Burn Severities

Boreal

boreal

Boreal forests (sometimes called "taiga") are a mosaic of forest types — from sunny aspen groves to spruce bogs-intermingled with meadows, marshes, lakes, and rivers — in the northern high latitude regions. This ecosystem is characterized by cold weather, long winters, and permafrost.

Source: Alaska Department of Fish and Game Source

forests hold between 370-1720 Pg carbon (C) above- and belowground, making them a major stock of C globally. In North American boreal ecosystems, wildfire is the primary stand-replacing disturbance, and fires are projected to increase in frequency and severity in the future. Fires have direct effects on C stocks due to immediate losses during combustion, but also have indirect effects, through the modification of soil properties and remaining soil C, the response of vegetation communities, and changes to soil microbial communities and their activities. Changes to fire frequency and severity could affect each of these processes, and changes to fire severity or frequency have, indeed, been associated with changes in soil C storage. However, data quantifying these effects are sparse, and our understanding of the mechanisms driving them remains limited.

Recent advances in Earth system model (ESM)

earth system model (ESM)

A model that simulates how chemistry, biology, and physical forces work together. These models are similar to, but much more comprehensive than, global climate models.

Source: U.S. Department of Energy Source

representations of soil C cycling, such as the Carbon, Organisms, Rhizosphere

rhizosphere

The soil region influenced by plant roots where complex biological and ecological processes occur.

Source: EMSL Source

and Protection in the Soil Environment (CORPSE) model, have included an emphasis on explicitly representing the system in an increasingly mechanistically accurate way. In particular, this has included: representing both physically protected and unprotected C; distinguishing between rhizosphere and bulk soil; representing microbes

microbe

Microbes are tiny living things that are found all around us and are too small to be seen by the naked eye. They live in water, soil, and in the air.

Source: NIH Source

as dead or living, or as different functional types, among other developments. Because of their mechanistic nature, these models may be better prepared to represent the effects of wildfires on soil C dynamics than most current ESMs. Standard ESMs generally do not represent complex feedbacks between fire, vegetation, soils, microbes, and climate. Rather, they usually represent fires only in terms of their frequency and impacts on vegetation biomass

biomass

Material that comes from living things, including trees, crops, grasses, and animals and animal waste. Some kinds of biomass, such as wood and biofuels, can be burned to produce energy.

Source: EPA Global Climate Change Source

pools, and predict that the above-ground community follows a well- known trajectory over time, with no new steady states other than those functionally similar to the previous state.

We propose to determine whether linking belowground microbial community composition, size, and activity to aboveground properties of burn severity and plant community composition (upland jack pine and upland spruce) allows us to better model post-fire soil CO2

carbon dioxide (CO2)

An important heat-trapping gas, also known as a greenhouse gas, that comes from the extraction and burning of fossil fuels (such as coal, oil, and natural gas), from wildfires, and natural processes like volcanic eruptions.

Source: NASA Source

fluxes using the CORPSE model. We will use an integrated modelling-experimental approach, with mechanistic laboratory experiments designed to inform models of three hierarchical levels of complexity. Our objectives are as follows:

Objective 1. Quantify changes in C fluxes,

flux

The amount of some type of particle or energy crossing a unit area per unit time.

Source: NRC Library Source

microbial biomass, and microbial community composition, after simulated fires in intact soil cores across a burn severity gradient.
Objective 2. Develop and evaluate adaptations to the CORPSE model to better represent post-fire SOC dynamics across a burn severity gradient using data from Objective 1 across a hierarchy of model complexity: (1) no explicit microbial representation; (2) community-level microbial traits characterized by single scalable parameters – maximum growth rate, CUE, and total microbial biomass; (3) microbes characterized as an assemblage of multiple functional groups with different traits constrained by the observed experimental data across the microbial community.
Objective 3. Test the capacity of the adapted CORPSE model (Objective 2) to predict CO2 flux rates in burned cores from new sites.

Wildfires in boreal ecosystems represent a globally significant ecological process that is expected to be sensitive to climate change,

climate change

A change in the average conditions — such as temperature and rainfall — in a region over a long period of time.

Source: NASA Climate Kids Source

but is currently insufficiently understood and represented in models. We propose fundamental, mechanism-based and model-driven research in a globally important system with basic relevance for environmental change, addressing current modelling challenges. It will help advance understanding of Earth’s biogeochemical systems and climate while developing insights into terrestrial

terrestrial

The geographical and biological features that are associated with the Earth's solid, rocky surface, residing on or resembling the land or terrain found on our planet.

Source: NASA Source

cycling of C and nutrients, and their feedbacks with Earth’s climate system, thus strengthening scientific knowledge in ecology,

ecology

The interrelationships between living organisms and their environments.

Source: NASA earth observatory Source

biology, and biogeochemistry.

biogeochemistry

Studies the cycle of key elements like carbon, nitrogen, and phosphorus within Earth's systems. It explores how these elements interact and the factors influencing their cycles.

Source: Oak Ridge Biogeochemical Dynamics Source