LC-16  Abstract

The Effects of Rainfall Exclusion on Canopy Phenology, Water Dynamics, Carbon, Nutrients, and Survival of Plants of the Cerrado – “Projeto Seca-Cerrado”

Eric A. Davidson --Woods Hole Research Center (WHRC)
Carlos Augusto Klink -- Depto. de Ecologia, Instituto de Biologia, Universidade de Brasília (UnB)

            In recent years severe droughts have become common in tropical regions and may become more frequent in the future.  Recent images of large, extensive fires in the Amazonian and Cerrado regions remain fresh in our memories.  Although characterized as a biome with vegetation that explores deep soil to obtain nutrients and water, the cerrado has suffered from land use change over a large geographic area which has brought changes in the structure and function of this ecosystem.  Models that predict climate change show that substitution of native vegetation by monocultures of pasture plants can change precipitation patterns and the frequency dry periods in central Brazil.   These climatic changes can alter the balance between woody plants with deep roots and herbaceous and grass species with shallow roots.  The increase of global temperatures and a concomitant decrease in precipitation may increase the dominance of grasses to the detriment of deep-rooted woody vegetation in the cerrado.  The cerrado vegetation has the capacity to extract water and nutrients from deep soil layers during the long dry season, which permits the foliage to continue to transpire.  Recharge of soil water after a long drought is necessary for maintenance of the ecosystem.  During periods of prolonged drought, such as the last El Nino event of 1997/1998, this recharge of soil water did not occur, resulting in pronounced hydrologic stress.  The vertical distribution of carbon inputs by roots, and hence the stocks of soil carbon, could be substantially affected.  In this research project, we propose to test these predictions in the cerrado by provoking an experimental reduction in rainfall in an area of natural cerrado in the Reserva Ecológica do IBGE (protected from fire for more than 20 years) using a constructed cover over the vegetation with a removable top.  To understand the effects of rainfall exclusion on the structure and function of the vegetation, we are studying canopy phenology, growth and mortality of woody plants, production and quality of litter, nitrogen mineralization, microbial biomass, retranslocation of nutrients by woody species, production and distribution of roots, and soil respiration.  These measurements will be correlated with measures of soil water, using the same methodology that we have used to study soil water in deep soil shafts.  We will compare results from the experimental plot with an adjacent control plot.  

List of researchers and students participating in the “seca-cerrado” project in the IBGE Reserve (RECOR), Brasilia.  All are formally registered in IBGE (RECOR).




Carlos Klink

General coordinator

Dept. of Ecology, UnB

Mercedes Bustamante

Nutrient cycling

Dept. of Ecology, UnB

Flavia Pinto

Deep soil water dynamics; coarse root biomass; also responsible for general logistics

Assistant researcher, IPAM

Roberto Aduan

Soil respiration, decomposition and litter-fall

Ph.D. student, Dept. of Ecology, UnB, under Carlos Klink

Julio Resende

Phosphorous cycle in Cerrado soils

Ph.D. student, Dept. of Ecology, UnB, under Carlos Klink, Mercedes Bustamante, Daniel Markewitz (University of Georgia) and Eric Davidson (WHRC)

Alexandre Pinto

Trace-gases evolution

Ph.D. student, Dept. of Ecology, UnB, under Mercedes Bustamante

Rafael Oliveira

Isotopes and plant functional types

Ph.D. student, University of California, under Todd Dawson (co-advisor in Brazil: Carlos Klink)

Tomas Domingues

Oxigen isotopes

Ph.D. student, University of Utah, under Jim Ehleringher

Gina Cardinot

Plant water relations

Assistant researcher, IPAM, under Daniel Nepstad (WHRC)

Eddie Lenza

Plant demography and phenology

Ph.D. student, Dept. of Ecoloby, UnB, under Carlos Klink

Dulce Silva

Specific leaf area and leaf area index of Cerrado plants

Ph.D. . student, Dept. of Ecology, UnB, under Carlos Klink

Thiago André

Fine root biomass

Undergraduate student of biology, UnB, under Carlos Klink and Flavia Pinto

Liliane Bezerra

Deep soil water dynamics

M.Sc. student, Dept. of Ecology, UnB, under Carlos Klink

Luiz Martinelli, Plinio Camargo, Susan Trumbore

Soil carbon isotopes

CENA-USP, University of California


Other sources of financial support: