Recipient Organization
MICHIGAN STATE UNIV
(N/A)
EAST LANSING,MI 48824
Performing Department
PLANT SOIL MICROBIAL
Non Technical Summary
Many western forests are under frequent stress from drought, and at risk from catastrophic wildfires. Wildfires cause immediate losses of forest productivity via mortality and stem damage, but the severity of effects on soil can also compromise critical ecosystem services and forest productivity in the future by decreasing soil health, especially in forests that lack ecological adaption to high-severity burns. This project will provide foundational knowledge about how soil processes respond to fire, by investigating relationships between soil heating and its direct and indirect effects on soil properties that contribute to soil health. The over-arching hypothesis is that burn severity and soil heating determine the magnitude of impact on soil health, as well as its pattern, timeframe, and level of rebound. Specifically, this project will (1) define relationships between soil burn severity and soil heating, and (2) determine how soil properties and the resilience of soil health change as a function of temperature and duration of heating, and across gradients of soil burn severity. We will then (3) apply our data to improve and validate research and management tools, by expanding a new model that predicts biological response to soil heating, validating model predictions in wildfire sites. Results will be communicated to managers through a guide relating pre-fire site characteristics and burn severity to risks to soil health and associated ecosystem services. Improving scientific understanding of these relationships is essential for managing soils, which are a non-renewable resource and the foundation of ecosystem productivity.
Animal Health Component
30%
Research Effort Categories
Basic
40%
Applied
30%
Developmental
30%
Goals / Objectives
The major goals of this project are to:Characterize relationships among fire characteristics, burn severity, and soil heating;Determine the resistance and resilience of biological, chemical, and physical indicators of soil health to fire, burn severity, and soil heating;Develop understanding of causal relationships and correlations that support continued improvement of tools that guide forest and fire management decisions.
Project Methods
For Goal 1: We will use a combination of outdoor table-top burns with instrumented calorimeters and laboratory cone calorimeter experiments to provide controlled, replicated measurements, as well as leveraging past and ongoing field measurements at wildfire sites in California from the Fire Behavior Assessment Team to represent the range and variability of soil heating that occurs in natural conditions. To collect bulk samples for the manipulative heating and burning experiments, we will obtain woody fuels, litter and duff, and mineral topsoils from Forest Service lands near our previous study sites in California. We will conduct three replicated outdoor "burn table" experiments in Year 1 at UNR (where Co-PD Hanan's lab is located), using these samples and measuring soil temperature continuously at 5.0 cm, 10.0 cm and 15.0 cm. After fire extinction, we will take photos and record soil burn severity indicators and categorical descriptors at each calorimeter (NPS 2003, Lewis et al. 2006, Parsons et al. 2010, Jain et al. 2012). We will measure depth and surface cover of forest floor residue (ash, char, & uncombusted material), and collect this material to determine mass and chemical characteristics. Subsamples of this material and mineral soil by depth will be analyzed in the laboratory for physical, chemical and biological characteristics. We will also conduct controlled surface heating experiments at MSU using irradiance levels representing the high range of soil heating in wildfire conditions, which we are unlikely to attain in the burn table experiments. We will measure mass loss, C emission (CO2, CO), and water vapor loss continuously using the cone calorimeter, and will collect the heated soils to determine impacts to physical, chemical and biological characteristics.We will then collect field measurements and data from active wildfire sites in California by partnering with Co-PD Dickinson and the Fire Behavior Assessment Team. We will combine FBAT's data (leveraging existing data, and new data collected during this study) with our burn table experiments to evaluate relationships between severity level and soil heating, informed with data on fuel and fire characteristics. The FBAT sites provide co-located pre-fire, active-fire, and post-fire measurements and data on fuels, fire behavior, and fire effects, including burn severity and soil heating. We will characterize soil temperature regimes for each sampling location.For Goal 2: We will use laboratory procedures to characterize soil physical, chemical and biological properties for each soil sample (from controlled burning and heating experiments, and from field sites). This includes total C and N concentrations, organic matter (OM) and ash content, along with a suite of USDA recommended soil health analyses (Stott 2019). These include indicators for soil C sequestration, structural stability, microbial activity, carbon food source, bioavailable nitrogen, microbial community structure, and hydrological function (Stott 2019). We will also quantify additional properties that help interpret soil functional responses, including: pH, extractable N and P, Sulfur (S), cations (Ca, Mg, K) (NRCS 2014, James et al. 2018), soil water repellency and infiltration rates to evaluate hydrophobicity (Leelamanie et al. 2008, Robichaud et al. 2008), and Munsell color to evaluate oxidation in mineral soils. Measuring aggregate stability will aid in evaluating changes to soil structure that influence erosion risk. We will assess pyrogenic C (PyC) because it is an important component of post-fire forest C and our understanding of its role in soil processes is still developing (Miesel et al. 2015, Maestrini et al. 2017). We are interested in sulfur (S) cycling because it can be limiting in forest soils, especially for sites that experience an increase in N availability, which is a common transient effect of fire (Neary et al. 2008). Analyses will include analytical replicates, controls, blanks and reference materials per standard procedures. All methods are established procedures with necessary resources available. We will also collect mid-infrared spectra (FTIR) from all mineral soil samples, and will use partial least squares regression (PLSR) to develop predictive models to quantify soil C, PyC, and other chemical metrics on these samples (Baldock et al. 2013). To determine the effects of soil heating and burn severity on soil process rates, we will conduct a suite of laboratory incubations with subsets harvested destructively at a series of timepoints, until final measurements at day 300.For Goal 3: We will expand a new model (SheFire) that predicts microbial impact from soil heating data. We will also apply the new FBAT data to validate FOFEM predictions in the field, and to calibrate remotely-sensed and ground-based severity, providing our data to improve future tools. To quantify the immediate and short-term microbial responses to heating, we will develop the new response functions for SheFire by measuring soil microbial indicators in mineral samples before and after the burn table experiment, and following a 1-week post-burn incubation, using samples from the three depths in the soil profile corresponding to temperature sensor locations. We will determine microbial biomass (Fierer 2003), extractable organic C and N (EOC, EON), fungal:bacterial ratios (Frostegård et al. 1993), and potential extracellular enzyme activities for enzymes that degrade organic polymers and mineral-associated organic matter (Sinsabaugh et al. 2003). We will determine short-term microbial responses to heating via 3-week incubations, measuring respiration daily. Collectively, these data will allow us to estimate how microbial abundance, functional composition, and exoenzyme activity respond to heating and interact to influence soil respiration after fire.