1. BIOSPHERE-ATMOSPHERE INTERACTIONS IN DRY FOREST (MT) Site description Net ecosystem CO 2 exchange measurements Meteorological and ancillary measurements Field problems Preliminary results Additional measurements

2. The study was conducted approximately 50 km NE of Sinop Mato Grosso, Brazil (11°24.75'S: 55°19.50'W), which is located in the tropical rain forest and savanna ecotone Measurements were conducted between August 1999 and July 2001 in an intact, mature transitional forest with a closed 28-30 m tall canopy. The vegetation consists of evergreen trees that are characteristic of transitional forest in Mato Grosso. Soils are sandy, well-drained nutrient-poor (dystrophic) ultisols.

5. Sonic anemometer calibration - Team training

7. Leaf photosynthesis curve measurement

8. Leaf water potential measurement

9. Monitoring litter fall and decomposition: contribution to the transitional tropical forest (cerradão) respiration Litter fall 20 litter traps were installed in a 1 ha plot close to the meteorological tower. Fallen litter was collected monthly sorted and dry mass of leaves, twigs, flowers and fruits. Litter pool Monthly, in the same plot, litter on the soil surface was collected in 20, 25cmx25cm sampling squares. Litter decomposition dynamics In the same plot, we collected the litter on the forest soil to make the decomposition estimation.

10. Field problems

12. Lightining problems

13. UFMT technician fixing datalogger

14. Monitoring lighgtining activity around the Sinop tower

15. Preliminary results

18. PAR mount installed on the tree

19. Preliminary results Over the annual cycle, the CO2 flux of the transitional forest appears to be in balance. Our composite annual estimate of net C accumulation was 0.04 tC/ha. This value is lower than estimates reported for other forest ecosystems. There are large seasonal variations in transitional forest CO2 flux due to rainfall.