Can Microbial Ecology and Mycorrhizal Functioning Inform Climate Change Models?
EMSL Project ID
49729
Abstract
Using archived samples from forest Free Air CO2 Enrichment (FACE) experiments, fieldmeasurements from the Marcell Experimental Forest (MEF) and the Spruce and Peatland Response Under
Climatic and Environmental Change (SPRUCE) experiment, and the Mycorrhizal Status, Carbon and
Nutrient cycling (MySCaN) model, we will identify how the microbial regulation of organic nitrogen (N)
availability influences forest responses to climate change.
1. We will assess to what degree elevated CO2 increases organic N depolymerization by proteolytic and
chitinolytic bacteria throughout the mineral soil profile. We will use extracellular enzyme assays,
qPCR, and tag sequencing of bacterial protease and chitinase genes in archived soil samples from the
Duke Forest and ORNL FACE experiments. (Note: archived samples from Rhinelander FACE are not
available; Mark E. Kubiske, U.S. Forest Service, Northern Research Station, personal
communication).
2. We will estimate the source and quantify the use of organic N among ectomycorrhizal taxa by
combining existing stable isotope data from the Duke Forest FACE experiment, additional analyses
of 13C, 14C, and 15N, and a fungal culture experiment with 15N- and 13C-labeled amino acids. For
example, 14C on carbohydrate and protein fractions in fungi can partition protein sources between
current-year plant photosynthate and soil organic nitrogen; in FACE sites, similar analyses can use
both 14C and 13C. Both natural abundance and tracer 15N, 13C, and 14C levels can provide additional
information on organic N use, the recalcitrance of the assimilated N, and the depth of N sources.
3. We will further develop and validate a new model that incorporates organic nitrogen use and
mycorrhizal fungi (MySCaN). We will use existing data to: a) optimize parameter choices, b) validate
or modify the relationships used to govern C and N transfer between plants and mycorrhizal fungi,
and c) test whether the model predicts similar patterns to those seen in previous FACE studies. To test
model performance and our interpretations of isotopic patterns, output from the model will then be
used to run the NESIS model, which will predict isotopic signatures in Duke Forest and ORNL FACE
studies. NESIS will be modified to include 14C fluxes. These models will be used to gain insights
into: 1) the interactions among bacteria, free- living fungi, and mycorrhizal fungi, and 2) the relative
importance of mycorrhizal uptake of organic N of variable recalcitrance under different climate
change scenarios.
Project Details
Start Date
2017-02-27
End Date
2017-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members
Related Publications
Hobbie EA, J Chen, PJ Hanson, C Iversen, K McFarlane, NR Thorp, and KS Hofmockel. 2017. "Long-term carbon and nitrogen dynamics at SPRUCE revealed through stable isotopes in peat profiles." Biogeosciences 14:2481-2494. doi:10.5194/bg-14-2481-2017