Short term effects of experimental eutrophication on carbon and nitrogen cycling in two types of wet grassland

Picek, T. and Kaštovská, E. and Edwards, K. and Zemanová, K. and Dušek, J. (2008) Short term effects of experimental eutrophication on carbon and nitrogen cycling in two types of wet grassland. Community Ecology, 9 (Supple). pp. 81-90. ISSN 1585-8553

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Abstract

Plant biomass production, soil chemical and microbial parameters, microbial processes of C and N cycle and gases emissions were studied in soils at two types of grasslands (wet meadows). Both sites are situated in the Czech Republic: (1) a nutrient poor sedge meadow on organic soil (Z) and (2) a mesotrophic sedge-sweet grass meadow on mineral soil (H). Eutrophication was simulated by the application of NPK fertilizer to selected permanent plots in 2006 and 2007 in amounts of 9 kg N + 4 kg P ha-1 year-1 (low dose) and 45 kg N + 20 kg P ha- year- (high dose). After two years of fertilizer application, we observed an increase in net aboveground plant production (about 9–12 kg ha-1 year- ) connected with an increase in shoot:root ratio in fertilized plots of both sites, with more pronounced changes in oligotrophic sedge meadow. Total CO2 efflux from the ecosystem measured in situ was significantly higher at fertilized plots as well as increase in total soil respiration in case of sedge meadow, but we found no significant effect of fertilization on CO2 efflux from the system at mesotrophic site. Surprisingly, other parameters, like soil microbial biomass C and N content, the rates of respiration, denitrification, nitrification, nitrogen mineralization and nitrogen assimilation were not affected by fertilization. In conclusion, an interesting finding is that despite non significant impact on aboveground component there were significant responses in belowground part which suggest that belowground processes may be suitable early warning signals. Peaty oligotrophic soil seems to be more sensitive to nutrient addition than mineral soil. However, final effect of fertilization on ecosystem C balance stays unknown and longer study is necessary to draw explicit conclusion.

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