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TG-07 Abstract

Soil Biogeochemistry of Carbon, Nutrients, and Trace Gases in the Amazon Region of Brazil: Field Studies and Models of Natural and Managed Conditions

Michael M. Keller — USDA Forest Service (US-PI)
William Zamboni de Mello — Universidade Federal Fluminense (SA-PI)


We propose studies in three theme areas of LBA Ecology: carbon storage and exchange;

nutrient dynamics; and trace gas fluxes. We propose to work in undisturbed and logged

forest and in pastures in the area of the Tapajós National Forest south of Santarém,

Pará where we will contrast soil biogeochemical processes on sandy Ultisols and clay


CARBON STORAGE AND EXCHANGE. We will measure litter-fall and fine root biomass,

productivity, and decomposition on two common soil types in both logged and undisturbed

old- growth forest. We will provide a multi-year record of CO2 exchange between

the soil and the atmosphere for old growth forest and logged forests on two soil types, as

well as for old and young pastures using different management approaches. For old-growth

forest, we will deploy automated soil enclosures to determine the largest component of

ecosystem respiration thereby providing a critical check on eddy covariance estimates of

carbon exchange.

NUTRIENT DYNAMICS. We will compare nutrient stocks and cycling in litter and roots

on two contrasting soils. Analysis of nutrient retranslocation and experimental

fertilization of root-ingrowth cores will allow us to identify nutrient limitations.

TRACE GAS FLUXES. We will obtain a continuous multi-year record of soil atmosphere

CO2, N2O, NO, and CH4 fluxes from old-growth forest,

logged forest, and pasture using automated and manual enclosures. These measurements will

be complemented by gas concentration profile measurements obtained continuously from

towers for N2O and CH4 at 30-minute intervals in both undisturbed

and logged forest. Data screened for suitable atmospheric conditions will allow us to

estimate ecosystem fluxes for N2O and CH4. We will evaluate the

linkage between ecosystem productivity and N-oxide emissions in both pastures and forests

through measurements and simulations using DNDC.

Our coordinated measurements will link above- and belowground productivity and nutrient

cycles to trace gas exchange. Coordinated measurements and experimental manipulations will

allow us to gain a mechanistic understanding of the soil processes controlling carbon,

nutrient and trace gas dynamics. Measurements at a variety of temporal and spatial scales

will be synthesized using the framework of the DNDC biogeochemical model modified for

forest conditions. The understanding generated by this effort will be linked to ecosystem

productivity, a factor that may aid extrapolation beyond our research site.

Research Team Responsibilities

  • Patrick Crill: Trace gas and carbon measurements

  • William de Mello: Trace gases, nutrient cycling

  • Michael Keller: Trace gases, below-ground carbon cycling

  • Changsheng Li: Models of ecosystem production, soil biogeochemistry and trace gases

  • Whendee Silver: Below ground carbon and nutrient dynamics

  • Edzo Veldkamp: Trace gases, nutrients and productivity in pastures

Preferred Site

We hope to work on old-growth forest sites and logged forest sites in the Tapajós

National Forest south of Santarém, Pará and in pasture sites in the surrounding region.


We are assuming we can begin field activities in mid 1998 and that logging will occur

in July-December 1999.

  • Litterfall Collection, Undisturbed Forest - June 1998 to Dec. 2000

  • Litterfall Collection, Logged Forest - July 1999 to Dec. 2000

  • Litter Decomposition Assays - Sept. 1998 to Aug. 2000

  • Sequential Root Coring, Undisturbed Forest - June 1998 to May 1999

  • Sequential Root Coring, Logged Forest - July 1999 to Dec. 1999

  • Trench Plots (Root Decomposition) - Dec. 1999 to June 2000

  • Pasture Clipped Plots - June 1998 to May 2000

  • Trace Gas, Manual Enclosures (all land uses) - July 1998 to Dec. 2000

  • Trace Gas, Automated Enclosures, Undisturbed Forest - August 1998 to Dec. 2000

  • Trace Gas, Tower Profiles, Undisturbed Forest - July 1998 to Dec. 2000

Last Updated: May 18, 1998

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