High drought-tolerance of an Eastern Amazon forest: results from a large scale rainfall

exclusion

High drought-tolerance of an Eastern Amazon forest: results from a large scale rainfall

exclusion

Gina CardinotGina Cardinot1,21,2, Daniel Nepstad, Daniel Nepstad2,32,3, Missy Holbrook, Missy Holbrook44 and David Ray and David Ray2,32,3Gina CardinotGina Cardinot1,21,2, Daniel Nepstad, Daniel Nepstad2,32,3, Missy Holbrook, Missy Holbrook44 and David Ray and David Ray2,32,3

The Woods HoleThe Woods Hole

Research CenterResearch Center

Funded by:

11Federal University of Rio de JaneiroFederal University of Rio de Janeiro22IPAM-Amazon Institute of Environmental ResearchIPAM-Amazon Institute of Environmental Research33Woods Hole 3Woods Hole Woods Hole 3Woods Hole RResearchesearch CeCennterter44Harvard UniversityHarvard University

Many Amazon forests are resistant to droughtMany Amazon forests are resistant to drought

to identify thresholds beyond which key aspects of forest structure and function would be altered in important ways

how is drought severity related to flammability?

how is tree mortality influenced by prolonged drought?

Goals:Goals:

What will happen to the Amazon rainforest as rainfall declines?

• A decrease in rates of stem diameter A decrease in rates of stem diameter growth. Stem increment is one of the growth. Stem increment is one of the most sensitive components of NPPmost sensitive components of NPP

• Increase tree mortalityIncrease tree mortality• A decrease in leaf water potential and A decrease in leaf water potential and

increase of xylem damage by increase of xylem damage by cavitationcavitation

• Drought-induced reduction in leaf Drought-induced reduction in leaf area may increase susceptibility to area may increase susceptibility to fire in large forest areasfire in large forest areas

leaf-level physiological measurements,

tree-level water balance determinations (e.g. sapflow)

xylem proprieties

Floresta Nacional do Tapajós map

Seca Floresta Project

(rainfall exclusion experiment)

Study Site Layout

Dry Plot

Wet Plot

Paired 1 ha plotsThe panels cover ~75% of the ground

area and drain into elevated gutters. They are left in place during the ~6 month wet season between January and July.

The treatment prevents ~50% of incoming precipitation from entering the soil.

Baseline measurements were made for 1 yr prior to throughfall exclusion, beginning in Jan 1999

Rainfall exclusion since 2000

ResultsResults

Soil Water (TDR): Surface depletion in Yr 1; depletion at depth Yr 2.

TDR probes under construction.

Deep soil waterDeep soil water

Nov/ 2000

Oct/ 2001

Dendrômetros.

1.7 Mg/ha/yr less carbon accumulation

25% of the Amazon, this would mean 170 million tons of C remaining in the atmosphere each year

Nov/ 2000

Tree mortalityTree mortality

Beginning in May 2002, the middle of the third exclusion period, mortality rates for trees 10-30cm Dbh became elevated in the treatment plot relative to the control. In November 2002 nearing the end of the dry season, trees with >30cm Dbh began to show a similar response .

Tree mortality after 3 exclusion yearsTree mortality after 3 exclusion years

Predawn- Escheweilera pedicellata (Matamatá)

-2

-1.5

-1

-0.5

0

01/2

1/00

03/0

4/00

08/0

6/00

13/0

7/00

10/0

8/00

15/0

9/00

11/0

1/00

11/3

0/00

02/0

6/01

04/0

5/01

05/3

0/01

07/3

1/01

09/2

6/01

11/2

8/01

01/2

9/02

03/2

6/02

05/2

9/02

08/0

2/02

10/0

2/02

11/2

8/02

02/0

4/03

04/0

8/03

Data

LW

P (

MP

a)

Parcela Seca Parcela Controle

Predawn-Coussarea racemosa (Caferana)

-3.5-3

-2.5-2

-1.5-1

-0.50

01/2

1/00

03/0

4/00

08/0

6/00

13/0

7/00

10/0

8/00

15/0

9/00

11/0

1/00

11/3

0/00

02/0

6/01

04/0

5/01

05/3

0/01

07/3

1/01

09/2

6/01

11/2

8/01

01/2

9/02

03/2

6/02

05/2

9/02

08/0

2/02

10/0

2/02

11/2

8/02

02/0

4/03

04/0

8/03

Data

LW

P (

MP

a)

Parcela Seca Parcela Controle

Leaf water potential - PredawnLeaf water potential - Predawn

C.racemosa e E. pedicellata - Estação Seca/98

0102030405060708090

Horas do dia

Sa

p f

lux

de

ns

ity

(g

/m2

/s)

matamata caferana matamata Control caferana Control

E. pedicellata Estação Seca/2002

0

10

20

30

40

50

05:3

6

09:3

6

13:3

6

17:3

6

21:3

6

01:3

6

05:3

6

09:3

6

13:3

6

17:3

6

21:3

6

01:3

6

05:3

6

09:3

6

13:3

6

17:3

6

21:3

6

01:3

6

05:3

6

09:3

6

13:3

6

17:3

6

21:3

6

01:3

6

05:3

6

09:3

6

13:3

6

17:3

6

21:3

6

01:3

6

05:3

6

09:3

6

13:3

6

17:3

6

21:3

6

Hora

Sap

flu

x d

en

sit

y (

g/m

2/s

)

Matamatá dry Matamatá Control

C. racemosa - Estação Seca/2002

0

5

10

15

20

25

05:3

6

09:3

6

13:3

6

17:3

6

21:3

6

01:3

6

05:3

6

09:3

6

13:3

6

17:3

6

21:3

6

01:3

6

05:3

6

09:3

6

13:3

6

17:3

6

21:3

6

01:3

6

05:3

6

09:3

6

13:3

6

17:3

6

21:3

6

01:3

6

05:3

6

09:3

6

13:3

6

17:3

6

21:3

6

01:3

6

05:3

6

09:3

6

13:3

6

17:3

6

21:3

6

Hora

Sap

flu

x d

ensi

ty (

g/m

2/s)

Caferana Dry Caferana Control

Sap

flu

x d

ensi

tyS

ap f

lux

den

sity

LAI

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

13

/7/2

00

0

13

/9/2

00

0

13

/11

/20

00

13

/1/2

00

1

13

/3/2

00

1

13

/5/2

00

1

13

/7/2

00

1

13

/9/2

00

1

13

/11

/20

01

13

/1/2

00

2

13

/3/2

00

2

13

/5/2

00

2

13

/7/2

00

2

13

/9/2

00

2

13

/11

/20

02

13

/1/2

00

3

13

/3/2

00

3

13

/5/2

00

3

13

/7/2

00

3

Date

LA

I

Dry plot Control Plot

Figura 12. Instrumento para as medidas de LAI.

Poecilante effusa

0.0

0.5

1.0

1.5

2.0

Early dry season Late dry seaon Rain season

Season

Ks

(Kg/

s/m

/MPa

)

seca control

Coussarea racemosa (Caferana)

0.0

0.5

1.0

1.5

2.0

Early dry season Late dry seaon Rain seasonSeason

Ks

(Kg/

s/m

/MPa

)

seca control

Escheweilera pedicelata (Matamatá)

0

0.51

1.5

22.5

3

Early dry season Late dry seaon Rain season

Season

Ks (K

g/s/

m/M

Pa)

seca control

Miconia egensis (Papaterra)

0.01.02.03.04.05.0

Early dry season Late dry seaon Rain season

Season

Ks (k

g/s/

m/M

Pa)

seca control

Xylem – specific conductivityXylem – specific conductivity

Miconia engensis (Melastomataceae)

LWP (MPa)

-7 -6 -5 -4 -3 -2 -1 0

PLC

(%)

0

20

40

60

80

100

Coussarea racemosa (Rubiaceae)

LWP (MPa)

-7 -6 -5 -4 -3 -2 -1 0

PLC

(%)

0

20

40

60

80

100

Poecilanthe effusa (Fabaceae)

LWP (MPa)

-10 -8 -6 -4 -2 0

PLC

(%)

0

20

40

60

80

100

Escheweilera pedicelata (Lecythidaceae)

LWP (MPa)

-6 -5 -4 -3 -2 -1 0

PLC

0

20

40

60

80

100

Vulnerability curvesVulnerability curves

Percent Lost of Condutivity (PLC) vs Leaf water potentialPercent Lost of Condutivity (PLC) vs Leaf water potential

The forest shows a complex responses to drought

These data also help us to refine our forest models