Static chamber measurements of nitrous oxide (N2O) and methane (CH4) fluxes were made from five characteristic vegetation types, representing three different natural ecosystems (grasslands, deciduous forest and wetlands) in the Pannonian basin, Hungary. The main objective of the study was to determine the drivers of average seasonal, annual and interannual N2O and CH4 fluxes in these different ecosystems to enable more accurate predictions of responses to future climatic conditions. Investigations into the response of net N2O and CH4 emission rates to soil temperature and soil water content were carried out over a 2‐year period. Both N2O and CH4 fluxes covered a wide range. Yearly average N2O emissions ranged from 4.38 mg N m−2 year−1 for wetland poplar forest to 242 mg N m−2 year−1 for mountain oak forest. Yearly average soil fluxes of CH4 varied from oxidation, −106 mg CH4 m−2 year−1, for loess grassland to an emission of 129 mg CH4 m−2 year−1 for a wetland Glyceria stand. Multiple regression analyses showed that N2O fluxes from the Pannonian grasslands and oak forest were more dependent than CH4 fluxes on the key soil variables water content and temperature. The largest seasonal mean N2O emission, 319 mg N m−2 year−1, from a mountain oak forest, was observed in summer, and the largest seasonal mean CH4 emission, equivalent to an annual rate of 423 mg CH4 m−2 year−1, from a wetland Glyceria stand, was found in the spring of the wet year.

Foti Sz., Nagy Z., Balogh J., Bartha S., Acosta M., Czobel Sz., Peli R.E., Michal V.M., Tuba Z.: Small scale spatial variability and pattern of soil respiration and water content in wet and a dry temperate grasslands and bare soil. Ekologia (Bratislava), Vol. 28, No. , p. , 2009.

Soil fluxes of methane and nitrous oxide were determined for five different plant communities in Bodrogkoz, Hungary. As the direction of methane flux (emission or uptake) depends on the soil characteristics (mostly on soil moisture) bi-directional fluxes were observed in 2006 and 2007, the sink and source processes were practically balanced. Average soil nitrous oxide emission fluxes for the period of 2006-2007 was 1.2 μg N m-2 h-1 for tall vegetation while for low vegetation it was 2.4 μg N m-2 h-1. Taking into account the total atmospheric N-input, 0.7 to 1.6 per cent of deposited nitrogen is emitted from the soils in the form of N2O as an intermediate product of soil denitrification processes. Acta Biol Szeged 52(1):119-122 (2008)

The full greenhouse gas balance of nine contrasted grassland sites covering a major climatic gradient over Europe was measured during two complete years. The sites include a wide range of management regimes (rotational grazing, continuous grazing and mowing), the three main types of managed grasslands across Europe (sown, intensive permanent and semi-natural grassland) and contrasted nitrogen fertilizer supplies. At all sites, the net ecosystem exchange (NEE) of CO2 was assessed using the eddy covariance technique. N2O emissions were monitored using various techniques (GC-cuvette systems, automated chambers and tunable diode laser) and CH4 emissions resulting from enteric fermentation of the grazing cattle were measured in situ at four sites using the SF6 tracer method. Averaged over the two measurement years, net ecosystem exchange (NEE) results show that the nine grassland plots displayed a net sink for atmospheric CO2 of -240 +/- 70 g C m(-2) year(-1) (mean confidence interval at p > 0.95). Because of organic C exports (from cut and removed herbage) being usually greater than C imports (from manure spreading), the average C storage (net biome productivity, NBP) in the grassland plots was estimated at -104 +/- 73 g cm(-2) year(-1) that is 43% of the atmospheric CO2 sink. On average of the 2 years, the grassland plots displayed annual N2O and CH4 (from enteric fermentation by grazing cattle) emissions, in CO2-C equivalents, of 14 +/- 4.7 and 32 +/- 6.8 g CO2-C equiv. m(-2) year(-1), respectively. Hence, when expressed in CO2-C equivalents, emissions of N2O and CH4 resulted in a 19% offset of the NEE sink activity. An attributed GHG balance has been calculated by subtracting from the NBP: (i) N2O and CH4 emissions occurring within the grassland plot and (ii) off-site emissions of CO2 and CH4 as a result of the digestion and enteric fermentation by cattle of the cut herbage. On average of the nine sites, the attributed GHG balance was not significantly different from zero (-85 +/- 77 g CO2-C equiv. m(-2) year(-1)).

The specific objectives of this study were to determine the effects of different land use changes (extensive grazing, fertilization and irrigation) on the botanical and soil parameters, plant biomass production and CO2 gas exchanges and to provide data for model development. Experimental work has been carried out for 3 years in two characteristic semi-natural temperate grassland type of Hungary. Small grassland plots were positioned along two transects at fertilized and irrigated sites of loess steppe. At the fertilized (Isaszeg) site, mineral fertiliser was applied once a year at the beginning of the vegetation period, while top spray irrigation was operated continuously during each vegetation period at the irrigated site (Gödöllô). On the plain site an area of 6 ha of dry sand grassland was fenced off from the extensively grazing cattle herd. The shortest response of land-use change can be observed at botanical composition and partly at NEE (CO2), whereas soil parameters are significantly affected at longer time-scale. The observed changes were strongly correlated to climatic conditions, emphasized the importance of the water regime. Acta Biol Szeged 49(1-2):133-135 (2005)

Botanical (coenological) composition, leaf area index (LAI) and ecosystem CO2 exchange (synphysiological) investigations were carried out in the stands of a semi-desert sand grassland in Hungary under present-day and experimentally elevated CO2 concentrations. Present-day results prove the presence of three different types of the Festucetum vaginatae danubiale community in a little investigated area because of the high patchiness of this grassland. The types represent different stages of the secondary succession, and are different in synphysiological terms. The most striking observation is that the main factors, which determine the physiological activity, are the ratio of bare soil and the active LAI, or in other terms, stand architecture which trait also separates three types in coenological respect. The magnitude of CO2 exchange shows considerable temporal variability depending on the available soil water content. Estimated CO2 flux for the growing season in 2001 (from 01 April to 30 September) was 87.82 g CO2.m(-2), while for the dormant season of the years 2000-2001: -453.87 g CO2-m(-2), resulting in a net carbon-loss. The elevated CO2 level increased the cover values of most of the monocotyledon species. Under elevated air CO2 the generalists have disappeared, the rate of natural pioneers decreased, the rate of disturbance tolerant species, weeds and competitors increased. The consequence of the increased dominance of the monocots was detected in the physiological down-regulation of the stand scale photosynthetic CO2 assimilation. When measured at present-day 360 mumol.mol(-1) CO2 concentrations, there was no statistically significant difference between the net ecosystem CO2 assimilation rates of the sand grassland stands growing at present-day and elevated air CO2 level. Thus this grassland can not be considered as a significant carbon sink in the future high CO2. concentration.