01

23

4

DBH (cm)

dam

age/

mor

talit

y lo

sses

(t b

iom

ass/

ha/y

r)

Brown (1997), quadratic allometry, (total = 6.9 t/ha/yr)Brown (1997), exponential allometry (total = 7.1 t/ha/yr)

10 35 60 85 110

135

160

185

size-class (cm)

tree

s/ha

0 50 100 150 200

0.001

0.010

0.100

1.000

10.000

km 83:y = 2.26 + -0.0236 * x(0.124) (0.000912)

R ² = 0.9767RSE = 0.2 on 16 df

km 67:y = 1.87 + -0.0169 * x(0.106) (0.000886)

R ² = 0.9682RSE = 0.16 on 12 df

Overview

Motivating questions: (1) What is the present status of Amazonia as a source or a sink for atmospheric carbon dioxide? (2) What are the ecological and climatic controls on the interannual carbon balance in the Amazon basin? (3) What is the effect of selective harvest on forest carbon cycling and atmospheric exchange?Approaches: (1) ground-based biometry (woody tree increment and litterfall), combined with (2) whole-system CO2 fluxes (eddy covariance) at the local scale in an old-growth Amazonian rainforest (Tapajos National Forest, km 67, Santarem, PA, figure 1). Also: (3) measurement of continental-scale boundary-layer CO2 gradients (from continental interior to margin).Preliminary Results (Biometry): Dendrometers were installed in December 1999 (figure 2) based on results of the initial tree survey in July 1999 (figure 3), which included about 260 species in 50 families. The initial survey indicates that the tree size structure is slightly biased towards large trees relative to the selective harvest site at km 83. The dendrometry sample was random-stratified to guarantee adequate representation of each taxonomic group and to capture the disproportionally high biomass contained in the largest trees. Three months of monitoring indicate that growth rates are relatively even across size classes, but are dominated by a few taxonomic families, and by the tallest trees (figure 4A). The projected mean annual DBH increment in live trees is 0.44 cm yr -1 (data not shown), or 4 Mg carbon ha-1 yr -1. However, during the study period tree damage/mortality reduced the stock of live tree carbon at an annual rate of 3.5 Mg carbon ha-1 (data not shown). The absolute frequency of tree damage/mortality is dominated by the smallest size class (figure 4B), but is distributed evenly across canopy status and taxa. Methods analysis on this preliminary data set is shown in figure 4C. Two standard allometries for tropical forests (one quadratic and one exponential) yield total annualized biomass increments differing by less than five percent. A comparison between two dendrometer designs suggests possible measurement artifacts in the first year after installation.

Through continued monitoring, it is anticipated that more will be learned about the variability in the interannual and seasonal cycles of carbon sequestration in trees.

Natal

Figure 1 : Map of transects, including all trees >35cm DBH. Circles are proportional to DBH.

0 500 1000

-500

050

0

N

tower

meters

Biometry plots upwind of flux tower, with locations & sizes of all trees >35cm DBH

Km 67

Rio

Tap

ajós

Km 83

Santarém

Rio A

mazonas

Measuring carbon balances in the Amazon basin: I. Woody vegetation dynamics in an old-growth tropical rainforest

S. R. Saleska1†, L. Hutyra1, E. Hammond-Pyle1, E.G.T. Guimarães2, S.C. Wofsy1 1Dept. of Earth & Planetary Sciences, Harvard University; 2FFT

†corresponding author: srs@io.harvard.edu

Figure 2. Dendrometry study. Spring-mounted dendrometer bands were installed on trees at breast height, allowing precise estimates of tree diameter growth rates. We banded 1000 trees (out of the ~2600 inventoried). Tree biomass increase is calculated from DBH increase using allometric relations (e.g. Brown et al. 1997). Buttressed trees (see right) were banded above the buttress using a ladder. Twenty percent of the banded trees have a second band installed (see above) for comparison between different dendrometer designs.

Figure 1. Site location and biometry study design. The site is located ~70 km south of Santarém, Pará, Brazil, in the Tapajós National Forest (“km 67 site”), the location of the eddy-flux tower. Three transects (50 m x 1000 m) were laid out in the tower footprint, toward the predominant winds (east). A fourth transect runs perpendicular. Large trees (diameter at breast height, DBH > 35 cm) located within 25 m of either side of each transect line were identified, tagged, and measured. Smaller trees (between 10 and 35 cm DBH) were also identified, tagged, and measured in a narrower swath, 5 m of either side of each transect line. A total of ~950 large trees (indicated by circles above), and 1650 small trees (not shown) were identified.

Figure 3. Site characteristics.

Figure 4. Preliminary results of dendrometry (tree survey conducted July 1999; dendrometers installed December 1999; dendrometer measurements conducted February-May, 2000).

A. 76-day DBH increments (cm)

0.0

0.0

20

.04

0.0

60

.08

0.1

00

.12

fra

ctio

n o

f sa

mpl

e

n=13 n=2 n=1 n=1 n=1 n=1 n=2

(ii). By taxonomic family:

(iii). By canopy status:

B. 10-month (7/99-5/00) damage/mortality rates

(i). By size-class:

C. Aboveground biomass changes during initial study period.

25 50 75 100 125 150 175

0

5

10

15

20

25

DBH (cm)

tons

(bi

omas

s)/h

a

Brown (1997) quadratic (total = 303 t/ha)Brown (1997) exponential (total = 317 t/ha)

(i). Wood increment rates from dendrometry (76 days during Feb-May, 2000)

(ii). Loss rates due to damage/mortality (300 days from July ‘99 - May, 2000)

01

23

4

DBH (cm)

grow

th r

ate

(t b

iom

ass/

ha/y

r)

Brown (1997), quadratic allometry, (total = 8.1 t/ha/yr)Brown (1997), exponential allometry (total = 8.3 t/ha/yr)

10 35 60 85 110

135

160

185

(i). By size-class:

0.0

0.0

50

.10

0.1

5

DB

H in

cre

men

t(cm

)

Size class (cm)

0 50 100 150 200

n=

41

1

n=

15

3

n=

82

n=

74

n=

50

n=

37

n=

22

n=

22

n=

37

n=

17

n=

15

n=

10

n=

7

n=

8

n=

1

Ela

coca

rpa

ceae

Ste

rcu

liace

aeH

ippo

cra

teac

eae

Ver

ben

ace

aeS

ima

rou

bace

ae

Ce

last

race

ae

Ca

ryoc

ara

ceae

Mon

imia

ceae

Ru

bia

ceae

Co

nna

race

ae

Tili

ace

aeO

laca

ceae

Apo

cyn

ace

aeM

yrta

ceae

Mor

ace

ae

Bor

agi

nace

ae

Qu

iina

cea

eL

egum

ino

sae-

Pa

piL

aura

cea

eB

urse

race

ae

Lec

yth

idac

eae

Mel

asto

mat

ace

aeS

apot

acea

eA

nnon

ace

aeH

um

iriac

eae

Ebe

nace

ae

Fla

cour

tiace

aeG

utti

fera

eE

upho

rbia

ceae

Bom

bac

ace

aeM

yris

ticac

eae

Nyc

tagi

nac

eae

Sap

inda

cea

eM

alpi

ghi

ace

aeC

om

bre

tace

aeF

laco

urtic

eae

Voc

hys

iace

aeR

osa

ceae

Ana

card

iace

ae

Mel

iace

ae

Leg

umin

osa

e-C

aes

Leg

umin

osa

e-M

imo

Ce

crop

iace

ae

non

iace

ae

Ara

liace

ae

Aqu

ifolia

cea

eC

hry

sob

alan

ace

ae0.0

0.1

0.2

0.3

0.4

DB

H in

cre

men

t (c

m)

Emergent Canopy Sub-Canopy Suppressed

0.0

0.02

0.06

0.10

0.14

DB

H In

crem

ent(

cm)

n=238 n=281 n=172 n=265

(iv). By dendrometer design:

Emergent Canopy Sub-Canopy Suppressed

0.0

0.0

050

.010

0.0

150

.020

Fra

ctio

n o

f S

am

ple

n=247 n=295 n=178 n=270

0 50 100 150 200

050

100

150

200

DBH size class(cm)

Tre

es/ h

a

0 50 100 150 200

05

1015

20

DBH size class (cm)

Bio

mas

s (t

/ha)

(i). Frequency of trees (N=2596)

Bom

bac

ace

ae

Co

mbr

eta

ceae

Co

nna

race

ae

Ebe

nace

ae

Eup

horb

iace

ae

Lec

yth

idac

eae

Leg

umin

osa

e-C

aes

Leg

umin

osa

e-M

imo

Leg

umin

osa

e-P

api

Ru

bia

ceae

Sap

otac

eae

Sim

aro

uba

cea

e

0.0

0.0

50

.10

0.1

50

.20

0.2

5

% D

am

ag

e

n=2 n=1 n=1 n=1 n=2 n=3 n=2 n=3 n=1 n=3 n=1 n=1

(ii). By taxonomic family:

(iii). By canopy status:

Me

an

DB

H In

cre

me

nt(

cm)

0.0

0.0

20

.04

0.0

60

.08

0.1

0

Days

0 31 45

Chambers

Harvard

0.054

0.103

0.024

0.065

(ii). Distribution of biomass: (iv). Size class distribution, km 83 vs km 67: (iii). Allometric comparison

(v). Dendrometry Measurement: