Small-scale drivers: the importance of nutrient availability and snowmelt timing on performance of the alpine shrub Salix herbacea
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Alpine plant communities are predicted to face range shifts and possibly extinctions with climate change. Fine-scale environmental variation such as nutrient availability or snowmelt timing may contribute to the ability of plant species to persist locally; however, variation in nutrient availability in alpine landscapes is largely unmeasured. On three mountains around Davos, Switzerland, we deployed Plant Root Simulator probes around 58 Salix herbacea plants along an elevational and microhabitat gradient to measure nutrient availability during the first 5 weeks of the summer growing season, and used in situ temperature loggers and observational data to determine date of spring snowmelt. We also visited the plants weekly to assess performance, as measured by stem number, fruiting, and herbivory damage. We found a wide snowmelt gradient which determined growing season length, as well as variations of an order of magnitude or more in the accumulation of 12 nutrients between different microhabitats. Higher nutrient availability had negative effects on most shrub performance metrics, for instance decreasing stem number and the proportion of stems producing fruits. High nutrient availability was associated with increased herbivory damage in early-melting microhabitats, but among late-emerging plants this pattern was reversed. We demonstrate that nutrient availability is highly variable in alpine settings, and that it strongly influences performance in an alpine dwarf shrub, sometimes modifying the response of shrubs to snowmelt timing. As the climate warms and human-induced nitrogen deposition continues in the Alps, these factors may contribute to patterns of local plants persistence.
KeywordsGlobal change Herbivory Microhabitat Spring warming Reproduction
The authors are indebted to their 2013 field staff, including Günther Klonner, Sofia Häggberg, and Flurina Schnider. We would also like to thank Dr. Sophie Karrenberg and Dr. Sonja Wipf for invaluable comments which greatly improved this manuscript. This project was made possible by funding from the Swiss National Science Foundation (grant CRSI33_130409/1). CJL would also like to thank the Erasmus Mundus Master Programme in Evolutionary Biology for scholarship funding, and Dr. Herwig Stibor of the Ludwig Maximilians University for co-supervision of this research. The authors would like to dedicate this paper to our late colleague and friend, Janosch Sedlacek.
Author contribution statement
CR, JAW, JS, and AJC conceived and designed the experiment. CJL, JS and JAW performed the fieldwork. AJC, JAW, CJL and JS carried out data extraction. CJL performed labwork and statistical analysis. CJL wrote the manuscript. JAW, CR, JS and AJC reviewed and commented on the manuscript. The authors declare they have no conflict of interest and that all experiments comply with the current laws of Switzerland.
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