JXB Advance Access originally published online on March 19, 2008
Journal of Experimental Botany 2008 59(6):1431-1439; doi:10.1093/jxb/ern051
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
Different growth responses of C3 and C4 grasses to seasonal water and nitrogen regimes and competition in a pot experiment
1State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Xiangshan, Beijing 100093, China
2Graduate University of Chinese Academy of Science, Yuquanlu, Beijing 100049, China
* To whom correspondence should be addressed. E-mail: swan{at}ibcas.ac.cn
Understanding temporal niche separation between C3 and C4 species (e.g. C3 species flourishing in a cool spring and autumn while C4 species being more active in a hot summer) is essential for exploring the mechanism for their co-existence. Two parallel pot experiments were conducted, with one focusing on water and the other on nitrogen (N), to examine growth responses to water or nitrogen (N) seasonality and competition of two co-existing species Leymus chinensis (C3 grass) and Chloris virgata (C4 grass) in a grassland. The two species were planted in either monoculture (two individuals of one species per pot) or a mixture (two individuals including one L. chinensis and one C. virgata per pot) under three different water or N seasonality regimes, i.e. the average model (AM) with water or N evenly distributed over the growing season, the one-peak model (OPM) with more water or N in the summer than in the spring and autumn, and the two-peak model (TPM) with more water or N in the spring and autumn than in the summer. Seasonal water regimes significantly affected biomass in L. chinensis but not in C. virgata, while N seasonality impacted biomass and relative growth rate of both species over the growing season. L. chinensis accumulated more biomass under the AM and TPM than OPM water or N treatments. Final biomass of C. virgata was less impacted by water and N seasonality than that of L. chinensis. Interspecific competition significantly decreased final biomass in L. chinensis but not in C. virgata, suggesting an asymmetric competition between the two species. The magnitude of interspecific competition varied with water and N seasonality. Changes in productivity and competition balance of L. chinensis and C. virgata under shifting seasonal water and N availabilities suggest a contribution of seasonal variability in precipitation and N to the temporal niche separation between C3 and C4 species.
Key words: Chloris virgata, competition, growth, Leymus chinensis, nitrogen seasonality, water seasonality
Received 19 November 2007; Revised 29 January 2008 Accepted 4 February 2008