Towards assessing climate sensitivity of microbial processes and its effect on greenhouse gas fluxes...

Stefan Gerber, Saroop Sandhu, Dipti Rai, Kanika Inglett, Patrick Inglett, Ryan Penton, and Maria

Silveirasgerber@ufl.edu

Towards assessing climate sensitivity of microbial processes and its effect on greenhouse gas

fluxes in subtropical pastures

Site location: USDA-LTAR - UF IFAS Range and Cattle Research and Education Center, Ona Florida

• Characterize the soil microbial community across different management practices and measure the corresponding greenhouse gas fluxes.

• Determine the adaptation and acclimation of the soil microbial community climate change.

• Improve a soil greenhouse gas emission model to predict greenhouse gas emissions under global change scenarios

Project start was August, 2016

Project Objectives

Consistently managed sites

Native Rangeland

Improved Pasture

Preliminary Laboratory Analyses

Initial Soil Characterization

• Management has no impact on bulk density of soil. However, bulk density is significantly different for soil horizons.

• Bh horizon has lower bulk density compared to E2 probably be due to more organic carbon present.

• Soil pH is higher in managed grassland might be due to the addition of manure from cattle grazing.

• Also, soil pH increases with depth.

Preliminary results

• Management has no impact on moisture content of soil. However, moisture content is significantly different for soil horizons.

• Managed grassland has higher aerobic respiration rate which may be due to extra nitrogen source available by manure and chemical fertilizer additions.

Preliminary results

• Enzymes–β-glucosidase–Cellobiose Dehydrogenase–N-Acetyl-β-D Glucosaminidase–Leucyl aminopeptidase

• Microbial biomass carbon and nitrogen• Total carbon and nitrogen• Anaerobic respiration• Isotope analysis• Carbon fractions

Analyses in progress

Future steps

Adressing Microbial Response• 3 Key responses - Kinetic response (e.g. Vmax) - fast

- molecular analysis to address functional (gene expressions) slower- community response – slowest

• Incorporation of key responses into a new microbial-based decomposition and greenhouse gas production module in DNDC

Conceptual/Numerical Model

Functional and community response

Kinetic Response

Sihi et al., 2016, Biogeoscience

Expect different climate response

Sihi et al., 2016

Laboratory experiment and field data – Assessing of CO2, N2O fluxes

In the field: take advantage of seasonal and interannual cycle

We’ll go out some more!