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Despite a long history of alpine meadows studies, uncertainty remains about the importance of environmental factors in structuring their assembly. We examined the functional and phylogenetic structure of 170 alpine Tibetan meadow communities in relation to elevation, soil moisture and shade. Functional community structure was estimated with both communityweighted mean (CWM) trait values for specific leaf area (SLA), plant height and seed mass and functional diversity (Rao’s quadratic index) for their traits individually and in combination (multivariate functional diversity). We found that shade induced by woody plants significantly increased the phylogenetic diversity and functional diversity of SLA of co-occurring species, suggesting that woody plants behave as “ecosystem engineers” creating a different environment that allows the existence of shade tolerant species and thereby facilitates the coexistence of plant species with different light resource acquisition strategies. We also found evidence for a clear decrease in phylogenetic diversity, CWM and functional diversity related to plant height in the two extreme, both the dry and wet, soil moisture conditions. This indicates that both drought and excess moisture may act as environmental filters selecting species with close phylogenetic relationships and similar height. Moreover, we detected significant decreases in both CWM and functional diversity for seed mass along elevational gradients, suggesting that low net primary productivity (NPP) limits seed size. Finally, because of different individual trait responses to environmental factors, the multivariate functional diversity did not change across environmental gradients. This lack of multivariate response supports the hypothesis that multiple processes, such as environmental filtering, competition and facilitation, may operate simultaneously and exert opposing effects on community assembly along different niche (e.g., water use, light acquisition) axes, resulting in no overall functional community structure change. This contrast between individual and multivariate trait patterns highlights the importance of examining individual traits linked with different ecological processes to better understand the mechanisms of community assembly.

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): Local-scale diversity patterns of vascular epiphytes along an elevational gradient in the Andes. — J. Biogeography 32 : 1799–1809. Gradstein S. R. Local-scale diversity patterns

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. The Distribution and Abundance of Animals. Hofer, U., L. Bersier and D. Borcard. 1999. Spatial organization of a herpetofauna on an elevational gradient revealed by null model

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. Hodkinson , I.D. 2005 . Terrestrial insects along elevation gradients: species and community responses to altitude . Biol. Rev. 80 : 489 – 513 . Javal , M. , G

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Fisher, B.L. 1999a. Ant diversity patterns along an elevational gradient in the Réserve Naturelle Integrate d'Andohahela, Madagascar. Fieldiana Zoology (n.s.) 94:129-147. Ant diversity patterns along an elevational gradient in

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Community Ecology
Authors: T. Romanuk, B. Beisner, A. Hayward, L. Jackson, J. Post, and E. McCauley

1999 400 557 560 Robinson, J.L. and P.S. Rand. 2005. Discontinuity in fish assemblages across an elevation gradient in a

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-sodic grassland communities along an elevation gradient. Tiscia 36:7–15. Tóth T. Community boundaries and edaphic factors in saline-sodic grassland communities along an elevation gradient

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2011 . Elevational gradients in phylogenetic structure of ant communities reveal the interplay of biotic and abiotic constraints on diversity . Ecography 34 : 364 – 371 . Magurran

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75 84 Al-Sodany, Y.M., M.N. Shahata and K.H. Shaltout. 2003. Vegetation along an elevation gradient in Al-Jabal Al-Akhdar, Libya. Ecol. Mediter. 29: 35

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. Data Analysis in Vegetation Ecology 2010 Woldu, Zerihun, Feoli, E. and L. Nigatu. 1989. Partitioning an elevation gradient

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