IV. Alps-Adria Conference, 1st March, 2005 Portoroz, Slovenia

CARBON BALANCE OF GRASSLANDS IN HUNGARY

Nagy Z., Csintalan Zs., Balogh J, Czóbel Sz. Fóti Sz.&, Tuba Z., Department of Botany & Plant Physiology, Szent István University, Hungary

- Carbon balance of grasslands in Hungary is measured continously at two sites at the present

- Measurement techniques: eddy covariance and chamber methods

- Cumulative values of net ecosystem exchange

- Effects of extreme events, the 2003 drought

FLUXES

eddies,

carrying heat, momentum, water vapor and trace gases

3D sonic anemometerOpen path IRGA

10-20Hz

1GB storage card ~ for one month data

Covariances; products of deviations from the means

CO2

360 ppm

U

CO2

355 ppm CO2

355 ppm CO2

360 ppm

U

I II

w(t)(t)ρ(t)F xx

mol/m3 * m/s-3

-1

1

3

0 30 60 90time (seconds)

vert

ical

win

d sp

eed

(m

s-1

)

Bugac site, 46.69°N, 19.60°E, Hungarian Plainsextensive semiarid sandy grassland used as pastureMeasurements from July 2002

20

02

-07

-01

20

02

-10

-01

20

03

-01

-01

20

03

-04

-01

20

03

-07

-01

20

03

-10

-01

20

04

-01

-01

20

04

-04

-01

20

04

-07

-01

20

04

-10

-01

Cu

mu

lati

ve

NE

E (

mo

l C

.m-2

)

-25

-20

-15

-10

-5

0

5

10

Gap filled cumulative NEESink activity, tolerance to drougth, but becoming source due to drough from the mid of the summer

Seasonal and diurnal dynamics of NEE

Large variation between years in the length and productivity of the growing seasons

Mátra Mountains, Szurdokpüspöki, Hungary 300 m asl, 47.85°N, 19.73°E, brown forest soil of high clay content Measurements from June, 2003

Gap filled cumulative NEESink activity, less tolerant to drougth

2003

. 06.

01.

2003

. 07.

01.

2003

. 08.

01.

2003

. 10.

01.

2003

. 11.

01.

2003

. 12.

01.

2004

. 02.

01.

2004

. 03.

01.

2004

. 04.

01.

2004

. 06.

01.

2004

. 07.

01.

2004

. 08.

01.

2004

. 10.

01.

2003

. 05.

01.

2003

. 09.

01.

2004

. 01.

01.

2004

. 05.

01.

2004

. 09.

01.

NE

E (

mol

CO

2m-2

)

-10

-5

0

5

10

3 6 9 12 15 18 21 24

June, 2003

July, 2003

Aug, 2003

Sept, 2003

Oct, 2003

Nov, 2003

Dec, 2003

Jan, 2004

Feb, 2004

Mar, 2004

Apr, 2004

May, 2004

June, 2004

July, 2004

Aug, 2004

Sept, 2004

-14 -12 -10 -8 -6 -4 -2 0 2 4

µmol CO2.m-2.s-1

The contrasting weather patterns between the two years determined the source-sink relation of this grassland. The potential role of extensively managed grasslands in the vegetation's carbon balance on a larger (i.e. regional) scale can be in their recovery potential.

Seasonal and daily dynamics of NEE -Profound effect of drought

-- Total respiration was less affected by drought than assimilation (months: August in 2003 an 2004). In this way there might be a positive feedback between drought and source activity from grasslands, triggered by heat and drought waves.