Chamber series and space-scale analysis of CO2 gas-exchange in grassland vegetation: A novel approach

Significant part of our work was developing a new type of CO₂ and H₂O gas exchange chambers fit for measuring stand patches. Ground areas of six chambers (ranged between 0.044–4.531 m²) constituted a logarithmic series with doubling diameters from 7.5 to 240.0 cm. We demonstrate one of the first results for stand net ecosystem CO₂ exchange (NEE) rates and temporal variability for two characteristic Central European grassland types: loess and sand. The measured mean NEE rates and their ranges in these grasslands were similar to values reported in other studies on temperate grasslands. We also dealt with the spatial scale dependence from ecophysiological point of view. Our chamber-series measurement was performed in a perennial ruderal weed association. The variability of CO₂-assimilation of this weed vegetation showed clear spatial scale-dependence. We found the lowest variability of the vegetation photosynthesis at the small-middle scales. The results of spatial variability suggest the 0.2832 m² patch size is the characteristic unit of the investigated weed association and there is a kind of synphysiological minimi-area with characteristic size for each vegetation type.This work was supported by the Hungarian Scientific Research Fund (OTKA-32586), Plant Ecological Research Group of Hungarian Academy of Sciences, Kiskunsag National Park and CARBOMONT (EVK2-2002-00549) 5^th R & D EU project. This project is also related to CARBOEUROPE-IP (GOCE-CT-2003-50-5572) and GREENGRASS 5^th Framework Research Project (EVK-2-CT-2002-00105).Dedicated to Academician Prof. Gabor Fekete on the occasion of his 75^th birthday.