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ND-07 Abstract

Effects of Land Use Changes on the Functioning of Soils and Watersheds of Central Brazil Savannas: Impacts on Nutrient and Carbon Cycles and Trace Gas Exchange

Mercedes Bustamante — UnB - Universidade de Brasília (SA-PI)
Richard G. Zepp — US EPA (US-PI)

We propose

to assess the effects of land use on: 1) the stocks and cycling rates of carbon

and nutrient cycling and related ancillary data (microbial biomass; soil

temperature, soil moisture, etc.); 2) soil-atmosphere fluxes of trace carbon and

nitrogen gases (CO2, CH4, CO, N2O, and NO); and 3) the composition and quantity

of nutrients and organic matter entering small streams via gallery forests.

We will

quantify rates of carbon and nutrient cycling and characterize soil organic

matter (SOM) and litter quality at both native and converted sites.  We

plan to study the influence of fertilization and management practices (tillage,

no-tillage, cover crops, irrigation) on the carbon balance in pastures and

cropland.  These experiments will include measurements of soil-atmosphere

fluxes of trace carbon and nitrogen gases (CO2, CH4, CO, N2O, NO), different SOM

fractions, litter quality, N cycling, and P fractions.  To provide data and

relationships needed for regional trace gas and nutrient dynamics models we will

measure relevant ancillary data, including changes in soil temperature,

moisture, incident solar radiation, and the size and diversity of the soil

microbial community.  To assess land use changes on gallery forests and

aquatic systems, streams that drain watersheds dominated by natural vegetation,

agriculture, and urban lands, will be selected.  Chemical analyses of water

collected from surface runoff collectors, soil lysimeters, and groundwater

piezometer located within the gallery forest, and directly from the stream, will

be used to evaluate nutrient cycling within the forest buffers and the stream.

The goal will be to develop predictive models that relate the landscape metrics,

determined by analysis of spatial land cover databases, to the various chemical

and physical parameters.



Research Team

Responsibilities



 





●Roger

Burke – Watershed runoff; stream nutrient chemistry; gas fluxes



●Mercedes

Bustamante – Soil-air trace gas fluxes; nutrient pools and fluxes



●Alexandre

Nunes Cardoso –soil carbon pools and fluxes; SOM fractionation



●Daniel

Markewitz – watershed runoff; stream nutrient chemistry



●Marirosa

Molina – Nutrient pools and fluxes; microbial biomass/diversity





●Alexandre

Rosado – Nutrient pools and fluxes; microbial biomass/diversity





●Richard

Zepp – Soil-air trace gas fluxes; litter quality & decomposition





Research sites











Our

native study sites will continue to include native cerrado stricto sensu and

campo sujo and will expand to include gallery forests.  Added converted

Cerrado sites will include croplands and recently converted pastures. 

Sites include the research and ecological reserve operated by the Instituto

Brasileiro de Geografia e Estatística (IBGE) (www.recor.ibge.br)

and located 35 km south of Brasília D.F (15o 56’ S, 47o 51’ W) and pasture

sites located at the Fazenda Rio de Janeiro (15° 14’ S, 47° 42’ W)

northwest of Brasilia. 





● Soil trace gas exchange and related ancillary data (ambient and soil

temperatures, gravimetric and volumetric soil water content, solar irradiance,

microbial biomass) for the same sites and frequency included in nutrient

research



● SOM

and litter characterization at the six sites



● Nutrient pools/flux

characterization and microbial biomass for six sites (six chambers per site),

two native cerrado, two crop sites, two pasture sites with 2 intense data sets

(4 measurement sets on weekly basis) per year and monthly measurements in

intervening months.







Stream chemistry from a single location in six watersheds and along two

transects of samplers moving from the stream to three different adjacent land

use classes



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