C and N biogeochemical cycling in soils

(soil formation, soil organic matter stabilization, soil responses to productivity-driven perturbations)

Some of these projects investigate the relationships between litter quality and amount, the activity and distribution of fungi, and the distribution of forest plants. Field based experiments are designed to studying how litter composition and quantity in temperate forests and woody plant encroachment into subtropical grasslands impacts soil development, soils organic matter dynamics and chemistry.

Our research addresses fundamental processes controlling carbon storage in soil fractions within natural and managed ecosystems. To accomplish this we utilize molecular chemistry, microbial activity assays, and stable isotope techniques on soil fractions. Currently, we have funding by USDA and NSF to study these issues.

For Example, our most recent funding from DOE deals with how soil carbon responds to elevated atmospheric CO2.   To date, most field-scale CO2 enrichment studies have been unable to detect significant changes in soil C against the relatively large, spatially heterogeneous pool of existing soil organic matter, leading some to conclude that the potential for increased soil C is limited. A further concern is that any CO2-stimulated increases in soil C will be allocated primarily to rapidly cycling, labile pools with little, if any, long-term stabilization.

Filley and collaborators propose to address a series of unanswered questions regarding the accrual of soil C and its potential longevity at the sweetgum Free Air CO2 Enrichment (FACE) experiment at Oak Ridge National Laboratory (ORNL). The measurable linear increase in soil organic C that has been observed with repeated sampling at the ORNL  FACE, coupled with the 13C label present in the elevated CO2 treatment provides a unique opportunity to investigate both soil C responses to atmospheric CO2 enrichment in this deciduous forest and fundamental questions regarding the cycling, turnover, and stabilization of specific soil C pools derived from distinct plant biopolymer components.

 

The team will use a physicochemical fractionation approach, stable C isotopes, longterm incubations, and compound specific isotope analysis of selected biopolymer components to evaluate the dynamics, sources, and stability of functionally meaningful soil C pools and their response to atmospheric CO2 enrichment, with the ultimate goal of providing information that can be used to help validate, parameterize, and improve terrestrial C cycle models and provide policymakers with the tools necessary to determine safe levels of greenhouse gases for the Earth system.