Water and carbon fluxes in forested and crop areas

in Brazil

Humberto Rocha

Chicago, Illinois/US, 12-13 Jun 2012

1.Description of climate and croplands

2.Measurements of ET, GEP and albedo

3.Deforestation feedback in rainfall

4.Peak flows and load discharge in cropland streams

3

1. Climate

Critical patterns of water availability

Fonte: ANA – Conjuntura Recursos Hídricos do Brasil

Sugar cane

Soybean

Corn

Rice

2. Main crops – area,

productivity

The forest protection code legislation (1965) statements:

Legal reserve (RL)Permanent Protected Areas (APP)

Law enforcement (2005)

3. Flux tower sites in forested areas

Flux tower over sugar cane, cerrado and eucaliptus plantation (MogiGuaçu watershed – state of São Paulo)

ET and GEP across a forest-cerrado biome transition

30 60 90 120 150 180 210 240 270 300 330 3600

0.2

0.4

0.6

0.8

1

Pc P

cm

ax-1

30 60 90 120 150 180 210 240 270 300 330 3600

0.2

0.4

0.6

0.8

1

No. days since dry season starts

GEP

GEP

max

-1

Gross Ecosystem Productivity (fraction of max) with days since start of dry season

Equatorial forests

Tropical seasonal forests

Savanna & Pasture

Evapotranspiration (fraction of max) Equatorial forests

Tropical seasonal forests

Savanna & Pasture

CO2 fluxes: annual sum is prone to uncertainties Miller 2004, Ecol Appl; Goulden 2004 Ecol Appl, 2006 JGRSaleska 2003, Science; Hutyra 2007 JGR

Reco

GPP

Reco ~ nighttime flux

GPP ~ daytime flux – Reco

•High numbers are observed in the

tropics• Miller 2004, Ecol Appl

... but leads to a reasonable interpretation of seasonality

Reco u*filtered

Dry season

sink

Wet season

loss

CO2 flux – tropical forest Santarem (k83 site)

Wet season 68%at 3m

Dry season 84%at 7m

Soil moisture pumped from trees at different depths (% of daily totals)

Soil moisture measurement

with Time Domain

Reflectometry

The ability of forest vegetation to reach soil moisture and depend on its variability is a key step

to understand the ecosystem resilience

Previous modelling sudies suggested that large scale deforestation in Amazonia may lead to a reduction in rainfall and impact the ecosystem, but the investigation over small areas is still a less known matter.

This numerical experiment used:BRAMS atmospheric model w/3 nested grids (64,32,08 km of horizontal resolution)

Rainfall inhibition

Rainfall enhancement

Changes varied from 10 to 30

%

Deforestation strip

Global Solar Albedo over sugar cane plantation – measurements in 3 different harvest types (Cabral et al 2011, and unpublished data)

1997-1999 – harvest in Apr/May, dry leaves burning, manual harvest (unpublished)

2001-2002 harvest in Sep/Out, green harvest w/ mulching (unpublished)

2005-2007 harvest in Apr/May, burning dry leaves, mechanical harvest (Cabral et al 2011)

Harvest

(bars)

0 3 6 9 12 15 18 21 24hora do dia

1 8

2 0

2 2

2 4

2 6

2 8

3 0

Tem

pe

ratu

ra d

o a

r ac

ima

da

cop

a (

oC

)

M é d ia no pe ríod o ch uvoso

cana-de-açúcar

Cerrado

eucalipto

Measured mean ET and above canopy temperature (Source: Tatsch, J. (2012) PhD thesis USP and unpublished data)

ET simulatied w/ modified-SiB2 model)

Rainfall runoff modelling (DBHM/SiB2) at MogiGuaçu watershed. Source: Tatsch, J. (2012) PhD thesis USP

Current Land Cover APP_reforest (Permanent Protected areas)

Eucaliptusintermediate

Cerradolower

sugar canehigher

Final statements

Brazil ranks 8th in global economy - Agrobusiness ~ 1/3 GDP and ½ jobsVery competitive ethanol (10 units of energy/1 unit of

fossil fuel used)Large potential crop expansion with strong concern on

environmental sustainability

University of São Paulo seeks for partnerships which helps to quantify the ecosystem services and identify ways for their economical internalization with regional and global benefits

Thanks – contact HUMBERTO@MODEL.IAG.USP.BR