Abstract
The influences of intraspecific competition on plant size inequality have been well documented, but interspecific effects on this topic remain little understood. Here we examined the effects of canopy shading and fine roots of the trees (Elaeagnus angustifolia) on size inequality of the grasses (Achnatherum splendens) in a temperate savanna community in northwest China. Three study plots of 400 m2 were divided into 4-m2 quadrats, within each of which (1) canopy shading was quantified by modeling cumulative direct solar radiation (CDSR) and (2) the root effect was quantified using an empirical relationship between tree fine root density (TFRD) and relative distance to tree bases. Morphological traits were measured to represent grass size. Redundancy analysis (RDA) was conducted to examine the relative influences of grass density, CDSR and TFRD on the coefficient of variation of grass size. Results showed that no significant correlation occurred between grass density and grass size inequality. Both CDSR and TFRD had significant negative correlations with grass size inequality, suggesting that canopy shading and the presence of fine roots of trees can, respectively, increase and reduce grass size inequality. Canopy shading and TFRD played competitive roles in determining grass size inequality, where the root effect was a stronger factor than canopy shading. The tree effects can substantially alter the intensity of water stress. In response, size inequality of the grasses could be influenced through size-specific growth/mortality and slowed size divergence. These mechanisms could operate together in the savanna community.
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Acknowledgments
We would like to thank Dr. Kimberly Brosofske for enlightening discussion and linguistic checking, and an anonymous reviewer for valuable comments on the earlier versions of this paper. We also thank Zheng Huang, Bin Chen, Tselmeg Uriankhai, Wen Yu, Cheng Zhang, Qinmei Zhang, Xiaokai Liu, Jun Wang and Chi Zhang for assistance in the field investigations. This study was supported by National Natural Science Foundation of China (No. 40675040).
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Chi Xu and Mingjuan Zhang contributed equally to this paper.
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Xu, C., Zhang, M., Liu, M. et al. Interspecific effects on plant size inequality: evidence from a temperate savanna community. Plant Ecol 213, 225–235 (2012). https://doi.org/10.1007/s11258-011-0018-9
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DOI: https://doi.org/10.1007/s11258-011-0018-9