Two mire species respond differently to enhanced ultraviolet-B radiation: effects on biomass allocation and root exudation.
Increased ultraviolet-B (UV-B) radiation arising from stratospheric ozone depletion may influence soil microbial communities via effects on plant carbon allocation and root exudation. Eriophorum angustifolium and Narthecium ossifragum plants, grown in peatland mesocosms consisting of Sphagnum peat, peat pore water and natural microbial communities, were exposed outdoors to enhanced UV-B radiation simulating 15% ozone depletion in southern Scandinavia for 8 wk. Enhanced UV-B increased rhizome biomass and tended to decrease the biomass of the largest root fraction of N. ossifragum and furthermore decreased dissolved organic carbon (DOC) and monocarboxylic acid concentration, which serves as an estimate of net root exudation, in the pore water of the N. ossifragum mesocosms. Monocarboxylic acid concentration was negatively related to the total carbon concentration of N. ossifragum leaves, which was increased by enhanced UV-B. By contrast, enhanced UV-B tended to increase monocarboxylic acid concentration in the rhizosphere of E. angustifolium and its root : shoot ratio. Microbial biomass carbon was increased by enhanced UV-B in the surface water of the E. angustifolium mesocosms. Increased UV-B radiation appears to alter below-ground biomass of the mire plants in species-specific patterns, which in turn leads to a change in the net efflux of root exudates.
Rinnan
Riikka
R
Department of Terrestrial Ecology, Institute of Biology, University of Copenhagen, Øster Farimagsgade 2D, DK-1353 Copenhagen K, Denmark. riikkar@bi.ku.dk
Gehrke
Carola
C
Michelsen
Anders
A
D000704:Analysis of Variance; D018533:Biomass; D002244:Carbon / Q000378:metabolism; D029785:Cyperaceae / Q000254:growth & development / Q000528:radiation effects*; D019684:Magnoliopsida / Q000254:growth & development / Q000528:radiation effects*; D009930:Organic Chemicals / Q000032:analysis; D018517:Plant Roots / Q000254:growth & development / Q000528:radiation effects; D014466:Ultraviolet Rays
D009930:Organic Chemicals; D002244:Carbon