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 M.C. Bustamante, UnB (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. Our research will focus on the following LBA research questions:

CD–Q3a How do pools and fluxes of carbon and nutrients (in soils) of pasture/cropland change over time and what factors determine carbon gain or loss?

TG-Q1 How are fluxes of trace gases and aerosols between ecosystems (both upland and wetland) and the atmosphere of Amazônia affected by land cover and land use change?

TG-Q2 What is the (climatically driven) seasonal and inter-annual variability of trace gas and aerosol fluxes between the atmosphere and different land use and land cover types?

TG-Q3 Are losses and gains of carbon from Amazônian ecosystems in forms other than carbon dioxide (e.g. carbon monoxide, methane, volatile organic carbon, organic aerosol) of sufficient magnitude to influence ecosystem carbon balance?

ND–Q1 How do stocks, cycling rates and budgets of carbon and important elements nitrogen, phosphorus, potassium, calcium, magnesium, and aluminum change under different land covers and land uses?

ND–Q4 How do changes in land use and climate alter the stocks, processes and fluxes of dissolved and particulate organic matter, nutrients, and trace gases from the uplands across the riparian zones and floodplains and down the channels of river corridors?

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) 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