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Differential phosphorus and nitrogen effects drive species and community responses to elevated CO 2 in semi‐arid grassland
Author(s) -
Grünzweig José M.,
Körner Christian
Publication year - 2003
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 - 10.1111/j.1365-2435.2003.00797.x
Subject(s) - nutrient , agronomy , phosphorus , biology , biomass (ecology) , grassland , arid , nitrogen , productivity , zoology , ecology , chemistry , organic chemistry , macroeconomics , economics
Summary1 Productivity of dryland communities is often co‐limited by water and nutrients. Since atmospheric CO 2 enrichment induces water savings by plants, elevated CO 2 and nutrients could interact to reduce growth limitation, irrespective of the direct influence of CO 2 on photosynthesis. We studied CO 2 effects in model communities from the semi‐arid Negev of Israel with 17 mostly annual C 3 species at three CO 2 concentrations and three nutrient treatments. 2 Community biomass increased at elevated (440 and 600 µL L −1 ) compared to pre‐industrial CO 2 (280 µL L −1 ) by 34% on average in the low‐nutrient control, by 45% in the high P and by 50% in the high NPK treatment. Less evapotranspiration at elevated CO 2 increased soil water content by 30–40% on average. Significant CO 2 –fertilization interactions indicated that plant responses to CO 2 enrichment were constrained by nutrient availability. 3 Responses of biomass and water‐use efficiency (dry‐matter accumulation per cumulative evapotranspiration) to CO 2 enrichment were non‐linear and were saturated at 440 µL L −1 at low nutrient and high P supply. CO 2 effects were further increased up to 600 µL L −1 only under full NPK fertilization. 4 The overall CO 2 effect on biomass depended on the differential response of plant functional groups, with the P‐dependent legume response dominating at low nutrient and high P supply, and the N‐dependent grass response dominating at high NPK. With the exception of grasses, species responded differently to combinations of CO 2 enrichment and nutrient addition, even within functional groups. 5 Biomass production was co‐limited by CO 2 and nutrients in this semi‐arid seasonal community, with both effects possibly mediated by water availability. Nutrient losses associated with desertification will thus diminish potential gains in biomass due to elevated CO 2 . Growth stimulation by CO 2 enrichment beyond close‐to‐current concentrations will only be seen under nutrient‐rich conditions in semi‐arid and possibly other drought‐stressed grasslands.