Carbohydrates and Biomass_Loranger2017

Carbohydrates and Biomass_Loranger2017.txt = Tab-delimited text file. Non-structural carbohydrate concentrations and biomass of plant parts (roots, stems, leaves) of tree seedlings at alpine treeline elevation in the French Alps. Seedlings were planted in spring 2013 and harvested in autumn 2013 and spring 2014. ID = Sample ID from carbohydrate extraction Season = sampling season: S13 = September 2013, M14 = May 2014 Block = experimental block Treat = treatments: C = Control = bare-ground plots; Sh = shading = covered by shade roofs; V = full vegetation, V2 = intermediate vegetation Species: Lar = Larix decidua; Pic = Picea abies; Sor = Sorbus aucuparia; Pin = Pinus cembra; Pinu = Pinus uncinata Ind = seedling number in the plot Part = seedling part: L = leaves, S = stem, R = roots MassSm = mass of extraction sample (mg) MassPt = mass of seedling part (mg) Glu = glucose concentration (mg/g) Fru = fructose concentration (mg/g) Sac = saccharose concentration (mg/g) Mal = maltose concentration (mg/g) Total_SC = total soluble sugar concentration (mg/g) Starch = starch concentration (mg/g) Total_NSC = total non-structural carb. Concentration (mg/g

Mortality_Loranger2017_13-14

Mortality_Loranger2017_13-14.csv = Comma-delimited CSV. Seedling mortality in tree seedlings at alpine treeline elevation in the French Alps. Seedlings were planted in spring 2013 and mortality was registered in September 2013 and April-May 2014, after snowmelt. The first registration was April 16th in Block 1, in the other blocks the registration was later, as snow melted later. Season = grouping of data collections into two seasons: May14 = Spring (16 April to late May) 2014, Sept 13 = 2 Sept 2013 Block = experimental block Treat = treatments: C = Control = bare-ground plots; Sh = shading = covered by shade roofs; V = full vegetation, V2 = intermediate vegetation. Species: Lar = Larix decidua; Pic = Picea abies; Sor = Sorbus aucuparia; Pin = Pinus cembra; Pinu = Pinus uncinata Planted = number of seedlings planted DeadOn = number of dead seedlings not counting those damaged by breakage or herbivory DeadAl = number of dead seedling

Data from: Competitor or facilitator? The ambiguous role of alpine grassland for the early establishment of tree seedlings at treeline

Alpine treelines are expected to move upslope with a warming climate. However, so far treelines have responded inconsistently and future shifts remain difficult to predict since many factors unrelated to temperature, such as biotic interactions, affect responses at the local scale. Especially during the earliest regeneration stages, trees can be strongly influenced by alpine vegetation via both competition and facilitation. We aimed to understand the relative importance of these two types of interaction in different vegetation structures for treeline regeneration dynamics. Effects of herbaceous alpine vegetation on seedling emergence and first-year performance were studied in a field experiment in the French Alps (2100 m a.s.l.) with five important European treeline tree species: Larix decidua, Picea abies, Pinus cembra, Pinus uncinata and Sorbus aucuparia. Total emergence and locally-germinated seedling survival were not affected, but for seedlings planted at two months of age, negative vegetation impacts dominated for all response parameters: first-year survival, growth and carbohydrate accumulation. However, in the winter half-year, evergreen tree seedlings increased carbohydrate reserves under the protection of senescent herbs. Also, responses of locally-germinated seedlings suggest facilitative vegetation effects in the first two months after emergence. Thus, the interaction switched between competition and facilitation according to ontogenetic stage and seasons. Still, the net outcome after one year was negative, but species differed in their susceptibilities. Because initial establishment is the first bottleneck determining whether treelines remain stable or move upslope, understanding establishment, including site-, life-stage and species-specific processes, is essential for understanding observed treeline spatial patterns and dynamics. When developing predictive models of treeline dynamics, all these ‘local’ aspects should be incorporated in addition to more global drivers like changes in temperature

Seedling emergence and survival_Loranger2017

Emergence and survival_Loranger2017.csv = Comma-delimited CSV. Emergence of tree seedlings from seeds and subsequent survival through the first growing season at alpine treeline elevation in the French Alps. Seeds were sown in autumn 2013 and emergence and survival/mortality were registered weekly throughout the growing season in 2014. Date = date of monitoring FreeDays = number of days after snowmelt Block = experimental block Treat = treatments: C = Control = bare-ground plots; Sh = shading = covered by shade roofs; V = full vegetation, V2 = intermediate vegetation. Species: Lar = Larix decidua; Pic = Picea abies; Sor = Sorbus aucuparia; Pinc = Pinus cembra; Pinu = Pinus uncinata Row = row in plot Sown = number of seeds sown Dead = number of dead seedlings Alive = number of surviving seedlings Germ_All = number of germinated seedlings (including subsequently dead ones

Responses of Tree Seedlings near the Alpine Treeline to Delayed Snowmelt and Reduced Sky Exposure

Earlier snowmelt changes spring stress exposure and growing-season length, possibly causing shifts in plant species dominance. If such shifts involve trees, this may lead to changes in treeline position. We hypothesized that earlier snowmelt would negatively affect the performance of tree seedlings near the treeline due to higher spring stress levels, but less so if seedlings were protected from the main stress factors of night frosts and excess solar radiation. We exposed seedlings of five European treeline tree species: Larix decidua, Picea abies, Pinus cembra, Pinus uncinata, and Sorbus aucuparia to two snow-cover treatments (early and late melting, with about two weeks difference) combined with reduced sky exposure during the day (shading) or night (night warming), repeated in two years, at a site about 200 m below the regional treeline elevation. Physiological stress levels (as indicated by lower Fv/Fm) in the first weeks after emergence from snow were higher in early-emerging seedlings. As expected, shade reduced stress, but contrary to expectation, night warming did not. However, early- and late-emerging seedlings did not differ overall in their growth or survival, and the interaction with shading was inconsistent between years. Overall, shading had the strongest effect, decreasing stress levels and mortality (in the early-emerging seedlings only), but also growth. A two-week difference in snow-cover duration did not strongly affect the seedlings, although even smaller differences have been shown to affect productivity in alpine and arctic tundra vegetation. Still, snowmelt timing cannot be discarded as important for regeneration in subalpine conditions, because (1) it is likely more critical in very snow-rich or snow-poor mountains or landscape positions; and (2) it can change (sub)alpine vegetation phenology and productivity, thereby affecting plant interactions, an aspect that should be considered in future studies

Appendix B. Detailed list of all traits considered for this manuscript with detailed references.

Detailed list of all traits considered for this manuscript with detailed references

Appendix A. Species pool of the Jena Experiment (Thuringia, Germany) with inclusion status in the analyses.

Species pool of the Jena Experiment (Thuringia, Germany) with inclusion status in the analyses

Appendix C. Details on the imputation analyses used in this manuscript.

Details on the imputation analyses used in this manuscript

Appendix D. Correlation matrix of the different community properties of the communities in the Jena Experiment.

Correlation matrix of the different community properties of the communities in the Jena Experiment