Effects of irrigation on community composition and carbon uptake in Pannonian loess grassland monoliths
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 CO2-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; C4/C3 plants), and Net Ecosystem CO2 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 C4 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.
KeywordsCanopy chamber Diversity Functional groups Loess grassland Monolith Net ecosystem CO2 exchange Species composition and structure Water addition
Analysis of Variance
Leaf Area Index
Normalized Difference Vegetation Index
Net Ecosystem CO2 Exchange
Photosynthetically Active Photon Flux Density
Social Behaviour Types
Soil Water Content
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