Moisture availability constrains Moisture availability constrains soil trace gas fluxes in an soil trace gas fluxes in an

eastern Amazonian regrowth eastern Amazonian regrowth forestforest

Steel Vasconcelos, Daniel Zarin, Eric Davidson, Steel Vasconcelos, Daniel Zarin, Eric Davidson, Francoise Ishida, Elisana Santos, Maristela Araújo, Francoise Ishida, Elisana Santos, Maristela Araújo,

Débora Aragão, Lívia Rangel-Vasconcelos, Francisco Débora Aragão, Lívia Rangel-Vasconcelos, Francisco Oliveira, William McDowell, Claudio CarvalhoOliveira, William McDowell, Claudio Carvalho

University of FloridaUniversity of FloridaWoods Hole Research CenterWoods Hole Research Center

Instituto de Pesquisa Ambiental da AmazInstituto de Pesquisa Ambiental da AmazônianiaUniversidade Federal Rural da AmazUniversidade Federal Rural da Amazôniania

University of New HampshireUniversity of New HampshireEmbrapa AmazEmbrapa Amazônia Orientalnia Oriental

COCO22 ,, NN22OO, and , and CHCH44 greenhouse gases greenhouse gases

NONO precursor of O precursor of O33

Gas production and consumption strongly Gas production and consumption strongly linked to the availability of soil moisturelinked to the availability of soil moisture

Limited understanding of the mechanisms that Limited understanding of the mechanisms that control variation in soil trace gas emissionscontrol variation in soil trace gas emissions

►Rainfall, litterfall, and decomposition Rainfall, litterfall, and decomposition confounding factors in observational studiesconfounding factors in observational studies

►Very few manipulative studies in tropical Very few manipulative studies in tropical forestsforests

IntroductionIntroduction

► Quantify the impacts of Quantify the impacts of soilsoil moisture moisture

availability availability on trace gas fluxes in a regrowth on trace gas fluxes in a regrowth

forest stand in eastern Brazilian Amazoniaforest stand in eastern Brazilian Amazonia

ObjectiveObjective

► Pará State, BrazilPará State, Brazil

► Regrowth forest (13 Regrowth forest (13 years old in 2000)years old in 2000)

► Rainfall = 2540 mmRainfall = 2540 mm

► TTair air = 24 – 27 = 24 – 27 ooCC

► OxisolOxisol

Study areaStudy area

► Treatments = control, irrigation, and litter removalTreatments = control, irrigation, and litter removal► Replicates = 4Replicates = 4► Plot size = 20 m x 20 mPlot size = 20 m x 20 m

Experiment layoutExperiment layout

S T A T I O N R O A D

1 2 3

4 5 10

9

12

1413

11

20 m 10 m

6

N

30 m

TreatmentTreatment

Dry-season irrigation (5 mm d-1)

COCO22 NO, NNO, N22O, CHO, CH44

TechniqueTechnique IRGAIRGA Chemiluminescence Chemiluminescence

Gas chromatographyGas chromatography

Collars per Collars per plotplot

33 22

FrequencyFrequency bi-weeklybi-weekly bi-monthlybi-monthly

MeasuremenMeasurement datest dates

6060 1818

Trace gas measurementsTrace gas measurements

Statistical analysisStatistical analysis

► Repeated measure analysisRepeated measure analysis: treatment, : treatment, date, and treatment x date effectsdate, and treatment x date effects

► Contrast analysisContrast analysis: season (wet vs. dry) and : season (wet vs. dry) and treatment within season effectstreatment within season effects

Irrigation increases soil water Irrigation increases soil water availabilityavailability

Rai

nfa

ll(m

m)

0

20

40

60

80

100

120

Date

01/00 07/00 01/01 07/01 01/02 07/02 01/03

So

il su

ctio

n(M

Pa)

-0.10

-0.08

-0.06

-0.04

-0.02

0.00

controlirrigation

Irrigation increases soil respirationIrrigation increases soil respiration

► COCO22 efflux during the dry season efflux during the dry season

► Irrigation maintained wet season RIrrigation maintained wet season Rsoilsoil levels levels

► Soil COSoil CO22 pulse events pulse events

Date

01/00 07/00 01/01 07/01 01/02 07/02 01/03

So

il C

O2

eff

lux

( m

ol

m-2

s-1

)

0

2

4

6

8

controlirrigation

Irrigation does not affect NO effluxIrrigation does not affect NO efflux

Date

10/99 04/00 10/00 04/01 10/01 04/02 10/02 04/03

So

il N

O e

fflu

x(

g N

m-2

h-1

)

02468

101214 control

irrigation

Irrigation increases NIrrigation increases N22O effluxO efflux

► Wet season efflux > dry season effluxWet season efflux > dry season efflux

► Irrigation > control Irrigation > control

Date

10/99 04/00 10/00 04/01 10/01 04/02 10/02 04/03

So

il N

2O e

fflu

x

(g

N m

-2 h

-1)

-5

0

5

10

controlirrigation

Irrigation increases CHIrrigation increases CH44 efflux efflux

controlirrigation

Date

10/99 04/00 10/00 04/01 10/01 04/02 10/02 04/03

So

il C

H4

eff

lux

(mg

CH

4 m

-2 d

-1)

-10

0

10

20

► Wet season efflux > dry season effluxWet season efflux > dry season efflux

► Irrigation efflux > control effluxIrrigation efflux > control efflux

► Moisture availability constrains COMoisture availability constrains CO22, N, N22O, and CHO, and CH44

emissions during the dry season emissions during the dry season

► The substantial impacts of soil moisture on soil The substantial impacts of soil moisture on soil

COCO2 2 efflux may have important implications for soil efflux may have important implications for soil

respiration modelling approachesrespiration modelling approaches

ConclusionConclusion

Next step: examining mechanismsNext step: examining mechanisms

Treatments:

control (C)

root exclusion (NR)

litter removal (NL)

litter removal + root exclusion (NLNR)

Root respiration = C – NR

Microbial respiration litter = C – NL

Microbial respiration soil = C – NLNR

Trenching experimentTrenching experiment

► OsórioOsório Oliveira, Glebson Souza, Evandro Silva Oliveira, Glebson Souza, Evandro Silva

(MANFLORA field assistants) (MANFLORA field assistants)

► Raimundo da Silva (Estação Experimental de Raimundo da Silva (Estação Experimental de

Castanhal – UFRA)Castanhal – UFRA)

► The Andrew W. Mellon Foundation and the

Conselho Nacional de Desenvolvimento Científico

e Tecnológico (CNPq), Brazil for the grants

AcknowledgementsAcknowledgements