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Interactive effects of elevated CO 2 , P availability and legume presence on calcareous grassland: results of a glasshouse experiment
Author(s) -
STÖCKLIN J.,
KÖRNER CH.
Publication year - 1999
Publication title -
functional ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 154
eISSN - 1365-2435
pISSN - 0269-8463
DOI - 10.1046/j.1365-2435.1999.00308.x
Subject(s) - forb , legume , biology , grassland , zoology , calcareous , phosphorus , growing season , interaction , agronomy , botany , chemistry , organic chemistry
1. We investigated the interactive effects of elevated CO 2 , supply of phosphorus (P) and legume presence in model communities of calcareous grassland. Half of the communities contained six graminoids and eight non‐legume forb species. In the other half, four non‐legume forbs were replaced by legumes. 2.Ecosystem responses . Above‐ground phytomass (>5 cm) hardly responded to elevated CO 2 alone. However, when P and legumes were combined, the CO 2 effect on above‐ground community phytomass in year two was a stimulation of 45% ( P <0·001). Below‐ground community dry matter was stimulated by elevated CO 2 alone by + 36% ( P <0·01), but was only + 20% ( P <0·05) when legumes were present and P was added. At the final (late season) harvest the mean effect of elevated CO 2 on total above‐ and below‐ground phytomass was + 23% ( P <0·001) and revealed no significant interactions among treatment combinations, because above‐ and below‐ground effects of CO 2 enrichment had opposite directions. 3.Functional group responses . When legumes were absent, graminoids increased their total above‐ and below‐ground phytomass in elevated CO 2 by 60% ( P <0·001) but there was no increase when legumes were present. The response of forbs to CO 2 was not significant, irrespective of co‐treatment. Legumes, however, were significantly stimulated by P supply and their CO 2 response was much larger when P was added (+ 55%, P <0·01 vs + 25%, NS). 4.Species responses . CO 2 effects on species ranged from highly positive (+ 143%) to moderately negative (– 43%). 5. Our results demonstrate that the effect of CO 2 enrichment in such natural grassland communities will be low on above‐ground phytomass and largely below‐ground if no additional nutrients are provided. N 2 ‐fixing legumes appear to be crucial for the community response to elevated CO 2 but legume responsiveness is largely controlled by P availability.