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Phenological, growth and reproductive responses to climate variability and experimental warming in eight arctic plant species Clark, Karin M.

Abstract

Phenology, growth and reproductive measures were taken on a suite of eight low arctic plant species, Oxytropis nigrescens (Pall.) Fischer, Ledum decumbens (Ait.) Lodd., Vaccinium Vitis-idaea L. var. Minus Lodd., Betula glandulosa Michx., Salix L. spp., Saxifraga tricuspidata Rottb., Eriophorum vaginatum L. and Carex aquatilis Wahlenb. var. stans (Drej.) Boott, over a period of six years (1997-2002) at the Tundra Ecosystem Research Station, Daring Lake, Northwest Territories, Canada. These data were related to climatic conditions and measures of previous season's allocation using Canonical Correlation Analysis (CANCOR). Temperature and snowmelt date were the climatic variables most correlated with spring phenology; whereas, temperature, rainfall and snowmelt are most correlated with growth and reproduction. The spring phenology of vernal flowering plants was less influenced by snowmelt than that of aestival flowering plants. Most species showed decreased time to flower with warmer temperatures yet snowmelt and precipitation patterns modified responses. Climatic relationships to growth and reproductive responses were species specific. Two of the study species, B. glandulosa, and C. aquatilis var. stans, showed negative correlations between the previous and current year's allocation to growth and reproduction. Correlations between previous season's reproductive investment and spring phenology were apparent in four of the study species, O. nigrescens, Salix spp., E. vaginatum and S. tricuspidata, A subset of three of the species, L. decumbens, V. Vitis-idaea and E. vaginatum was experimentally warmed using open-topped chambers for two years (2001-2002). Phenological, growth and reproductive responses were compared to unwarmed plots. Under warmer temperatures spring phenology was advanced such that the time from snowmelt to flowering contracted approximately five days for all species. However, timing of the end of the flowering phase remained unchanged. Growth of the two evergreen shrubs increased with warming while that of the sedge was decreased. Reproductive effort and success were essentially unchanged except for V. Vitis-idaea where number of flowers was reduced in the first year of warming. In general, the phenological results of the experimental manipulation confirmed those of the observational data; prefloration interval was shortened with increased temperature. The experimental and observational methods of study proved to be complementary approaches to understanding the complex responses of plants to a changing climate.

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