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Seed production and seed quality in a calcareous grassland in elevated CO 2
Author(s) -
THÜRIG BARBARA,
KÖRNER CHRISTIAN,
STÖCKLIN JÜRG
Publication year - 2003
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1046/j.1365-2486.2003.00581.x
Subject(s) - forb , graminoid , biology , grassland , biomass (ecology) , plant community , shoot , nutrient , agronomy , botany , zoology , ecology , ecological succession
In diverse plant communities the relative contribution of species to community biomass may change considerably in response to elevated CO 2 . Along with species‐specific biomass responses, reproduction is likely to change as well with increasing CO 2 and might further accelerate shifts in species composition. Here, we ask if, after 5 years of CO 2 exposure, seed production and seed quality in natural nutrient‐poor calcareous grassland are affected by elevated CO 2 (650 μ L L −1 vs 360 μ L L −1 ) and how this might affect long‐term community dynamics. The effect of elevated CO 2 on the number of flowering shoots (+ 24%, P < 0.01) and seeds (+ 29%, P = 0.06) at the community level was similar to above ground biomass responses in this year, suggesting that the overall allocation to sexual reproduction remained unchanged. Compared among functional groups of species we found a 42% increase in seed number ( P < 0.01) of graminoids, a 33% increase ( P = 0.07) in forbs, and no significant change in legumes (− 38%, n.s.) under elevated CO 2 . Large responses particularly of two graminoid species and smaller responses of many forb species summed up to the significant or marginally significant increase in seed number of graminoids and forbs, respectively. In several species the increase in seed number resulted both from an increase in flowering shoots and an increase in inflorescence size. In most species, seeds tended to be heavier (+ 12%, P < 0.01), and N‐concentration of seeds was significantly reduced in eight out of 13 species. The fraction of germinating seeds did not differ between seeds produced in ambient and elevated CO 2 , but time to germination was significantly shortened in two species and prolonged in one species when seeds had been produced in elevated CO 2 . Results suggest that species specific increases in seed number and changes in seed quality will exert substantial cumulative effects on community composition in the long run.