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ND-04 Abstract

Carbon and Nutrient Stocks, Soil Water Dynamics, and Trace Gas Fluxes in Abandoned Pastures and Agroforestry Systems in the Central Amazon

Erick C.M. Fernandes — World Bank (US-PI)
Elisa Wandelli — CPAA (Embrapa) (SA-PI)


We propose studies in three theme areas of LBA: carbon storage; nutrient dynamics; and

trace gas fluxes. Training of Brazilian collaborators and graduate students is an

important goal. We propose to evaluate soil biogeochemical processes on degraded pastures

and in six-year-old agro-silvopastoral systems at the EMBRAPA-CPAA experiment site located

54 km from Manaus on BR 174 and adjacent to the primary forest site used by INPA. The

degraded pastures are on the widely distributed clayey Oxisol (clayey, kaolinitic,

isohyperthermic, Xanthic Hapludox).

Carbon Stocks. Our preliminary data from recent work in the Amazon show dramatic

increases in biomass accumulation in both native and exotic tree and grass species with

modest additions of P and Ca to soils. To assess these priming effects of nutrients, we

will measure total system carbon (woody biomass, understory herbaceous biomass, litter

fall, surface litter, roots, fine root dynamics and soil) in fertilized and non fertilized

pasture chronosequence (2 years to 25 years). Similar measurements will be done in four,

well-characterized six-year-old agro-silvopastoral (ASP) systems that were established on

degraded pastures. Analyses of C stocks and pools will provide us with data for predictive

models of vegetation regrowth and carbon dynamics as a function of management


Nutrient Dynamics. We will measure nutrient stocks and cycling and water dynamics

in both the fertilized and non-fertilized pasture chronosequence and ASP systems. Although

the focus of the study will be on P and Ca as major limiting nutrients, the need for

nutrient additions will be based on analysis of soil nutrient levels and nutrient

availability, coupled with yield projections and nutrient budgets for the systems. We will

also measure (a) soil moisture and surface temperature and the resulting soil fauna

(decomposer) populations, (b) chemical characteristics (lignin, cellulose, polyphenols,

and other nutrients) of the litter, and (c) litter decomposition and nutrient release

patterns in the fertilized and non fertilized pasture and ASP systems. We expect to obtain

a better understanding of the response of the various components of the decomposers to

changes in microclimate, litter quality, and soil nutrient status and thus improve our

ability to predict rates of decomposition and hence nutrient release patterns in different

pasture and ASP use scenarios.

Our measurements of above and below-ground productivity linked to the physical,

chemical and biological factors will provide information on processes controlling carbon

and nutrient dynamics in abandoned pastures and the management alternatives to

rehabilitate abandoned pasture land. The detailed characterization of the soils,

vegetation, management and environmental variables at our site will facilitate

extrapolation of the results to other sites.

Research Team Responsibilities

  • John Duxbury: Soil carbon and biogeochemistry

  • Erick Fernandes: Nutrient cycling, above and below-ground productivity

  • Regerio Perin: Managed pastures.

  • Neliton Silva: Soil fauna and Insect ecology

  • Wilhelmus Sombroek: Soil taxonomy and soil nutrient dynamics.

  • Susan Riha: Soil water and nutrient dynamics and modeling

  • Elisa Wandelli: Forest ecology and secondary species succession.

Preferred Site

We hope to work in degraded and abandoned pastures in the Manaus region and on

agroforestry systems at the EMBRAPA-CPAA experiment station located on the road from

Manaus to Boa Vista (BR 174).


1. Pasture Chronosequence selection - June to August 1998

2. Site & pasture chronosequence characterization- August to December, 1998

Site instrumentation and on-site laboratory installation - August to December 1998

Above and belowground productivity measurement, pasture chronosequence and ASP systems

- Sept. 1998 to Dec. 2000. [Aboveground biomass,

litterfall, root cores, soil samples, soil C pools, ]

Litter decomposition Assays, ASP systems and pasture chronosequence

Sept. 98 to Dec. 2000

Soil fauna assays, all systems - Dec 98 to Dec. 2000

Last Updated: May 18, 1998

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