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Monoliths of temperate loess grassland and temperate semi-desert sand grassland have been exposed to elevated CO 2 (700 μmol mol −1 ) and present ambient CO 2 concentration in a 6-year open top chamber (OTC) experiment. In loess grassland elevated CO 2 increased both biomass and vegetation cover, whereas there was no similar effect found in semi-desert grassland. The content of glomalin related soil protein (GRSP) increased in both loess and sand grasslands under CO 2 enrichment (early summer aspect). The increase was higher in the case of easily extractable fraction (EEG), representing 14.7 and 22.2% of the chambered control’s EEG, for loess and sand grassland respectively. In the case of total glomalin the increase was much lower 7.9% (loess) and 2.6% (sand). On the basis of differences between elevated and ambient CO 2 treatment we could conclude that elevated CO 2 promoted C-deposition in xeric temperate grassland in early summer. Increases of EEG indicate an efficient partitioning of the recently fixed carbon to the soil.

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Long-term effects of the elevated atmospheric CO 2 on biosphere have been in focus of research since the last few decades. In this experiment undisturbed soil monoliths of loess grassland were exposed to an elevated CO 2 environment (two-times the ambient CO 2 level) for a period of six years with the aid of the open top chamber method. Control without a chamber and CO 2 elevation was applied as well. Elevated CO 2 level had very little impact on soil food web. It did not influence either root and microbial biomass or microbial and nematode community structure. The only significant response was that density of the bacterial feeder genus Heterocephalobus increased in the chamber with elevated CO 2 concentration. Application of the open top chambers initiated more changes on nematodes than the elevated CO 2 level. Open top chamber (OTC) method decreased nematode density (total and plant feeder as well) to less than half of the original level. Negative effect was found on the genus level in the case of fungal feeder Aphelenchoides , plant feeder Helicotylenchus and Paratylenchus . It is very likely that the significantly lower belowground root biomass and partly its decreased quality reflected by the increased C/N ratio are the main responsible factors for the lower density of the plant feeder nematodes in the plots of chambers. According to diversity profiles, MI and MI(2–5) parameters, nematode communities in the open top chambers (both on ambient and elevated CO 2 level) seem to be more structured than those under normal circumstances six years after start of the experiment.

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Community Ecology
Authors:
M.K. Singh
,
Z. Tuba
,
F. Jordán
,
I. Scheuring
, and
J. Podani

K. J. Gaston and J. I. Spicer (eds.) 2004. Biodiversity: An Introduction (Second Edition). Blackwell Science Ltd, a Blackwell Publishing Company, Padstow, Cornwall, 191 pp. ISBN 1-4051-1857-1, paperback, price: USD 49.95, GBP 19.99; U. Sommer and B. Worm (eds.) 2002. Competition and Coexistence. Ecological Studies, Vol. 161. Springer Verlag, Berlin, 221 pp. (with 69 figures, 5 in color, and 2 tables). ISBN 3-540-43311-2, hardback, price: EUR 69.95; J. Kolbek, M. Šrùtek and E. O. Box. (eds.) 2003. Forest Vegetation of Northeast Asia. Geobotany 28. Kluwer Academic Publishers, Dordrecht, xii+462 pp. ISBN 1-4020-1370-1, hardback, price: EUR 200.00;

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Cereal Research Communications
Authors:
Sz. Fóti
,
Sz. Czóbel
,
J. Balogh
,
J. Nagy
,
A. Juhász
,
Z. Nagy
,
S. Bartha
, and
Z. Tuba
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Remnants of the former semiarid forest-steppe vegetation of Hungary are suspected to undergo degradation processes because of recent land-use changes. Secondary succession towards closing of the vegetation starts with shrub invasion, mainly with species of the shrub layer of loess steppe oak forest. Soil respiration (SR) activity of the intercanopy loess grassland community was followed occasionally along of six years period, as well as the spatial patterns of SR and soil water content (SWC) with three direct measuring campaigns. Dependence of SR on SWC-soil temperature was statistically significant for the six years period, but the rest of the variance should be explained by other factors, as found for normalized difference vegetation index. In the spatial analysis, significant differences were found in the ranges of semivariograms according to the seasonal variation of soil moisture content. Larger scale patches were found under summer water stress (4 m for SR, 2.6 m for SWC) and autumn senescence (3.8 m for SR, 1.3 m for SWC) periods than under well-watered, peak performance summer circumstances (0.8 m for SR, 0.6 m for SWC). This suggests that homogeneity of patterns is typical at good water supply, while coarse-grained patches prevail under drought stress.

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Grassland ecosystems in the Carpathian Basin may be particularly vulnerable to current and predicted changes in precipitation, and ecosystem responses to potential effects of water are not well understood. To examine how water addition can affect the species composition and structure, and CO 2 -flux of a Central European natural steppe plant community, grassland monoliths were irrigated for three consecutive years at Gödöllő, from 2002 through 2004. The loess grassland studied by ex situ is a characteristic plant association of Hungary and similar vegetation can be found in other temperate regions. The treatment consisted of spray irrigation during night-time only in the growing season as well as aboveground biomass removal twice per year. Interannual and intraannual dynamics of species richness, Shannon Diversity, percentage cover, and different functional groups (monocots/dicots; plant life forms; social behaviour types; C 4 /C 3 plants), and Net Ecosystem CO 2 Exchange in treated and untreated permanent plots, were studied simultaneously. To measure NEE and water vapour at stand level a self-developed, portable, non-destructive open chamber system (d=60cm) was used. The majority of the examined parameters varied considerably among years at both irrigated and control, but concerning carbon fluxes water addition effects were evident in dry periods only. At the treated plots, in general species richness, Shannon Diversity, the number of plant life forms and social behaviour types, the ratio of dicots and C 4 plants declined with addition of water. Our study proved that decline in species richness and Shannon diversity is not necessarily followed by the reduction of stand physiological (synphysiological) processes.

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