DOI: 10.5061/dryad.005sk
title: Data from: No carbon "bet hedging" in pine seedlings under prolonged summer drought and elevated CO2

description: More frequent drought episodes are expected to cause higher mortality in
 isohydric tree species such as pines, because individuals close their
 stomata early during drought in order to maintain constant needle water
 potentials. It has been suggested that trees delay the ensuing carbon
 starvation by actively storing carbon at the expense of growth (“bet
 hedging”). Because such a strategy is only adaptive in drought-prone
 regions, we hypothesise that the degree of carbon “bet hedging” should
 differ between ecotypes. We repeatedly measured the allocation of biomass,
 starch and soluble sugars to needles, stem and roots in seedlings of nine
 populations of Pinus sylvestris and Pinus nigra along a gradient from
 Central Europe to the Mediterranean. During two consecutive growing
 seasons, seedlings grown from seed were exposed to factorial combinations
 of 4 months of drought (D1, D2) and ambient/elevated CO2 (aCO2/eCO2).
 Drought-stressed pine seedlings did neither increase starch
 concentrations, nor change biomass production or experience lower
 mortality under eCO2 compared to aCO2. By the end of D2, seedlings from
 drier origin had accumulated more starch but at the same time also more
 biomass than seedlings from wetter origin. Surprisingly, seedlings
 acclimatised to dry conditions after D1 so that mortality dropped to zero
 and drought effects on needle starch (P. sylvestris) and overall starch
 (P. nigra), respectively, disappeared after D2. Synthesis. The absence of
 a trade-off between carbon storage (starch) and growth (biomass), and the
 patterns of mortality observed in seedlings growing under combined drought
 and eCO2 do not support the theory of carbon “bet hedging” in isohydric
 Pinus sylvestris and Pinus nigra. Results suggest that reduced growth and
 acclimatisation minimised seedling mortality in the second year.
 Acclimatisation might thus enable pine seedlings to resist a moderate
 increase in summer drought frequency expected in the future.
description: d18O of
 SeedlingsThe Dataset contains
 d18O values (permille) of seedling samples.Isotopes d18O
 Seedlings.csvd18O of Water from the
 Study Site (Visp and Leuk)The Dataset contains
 d18O values (permille) of Rainwater and Groundwater in the experiment (see
 Supporting Information).Isotopes d18O Water Visp and
 Leuk.csvMortality
 DataThe Dataset contains
 Mortality counts of the experiment by date and
 mesocosm.Biomass
 dataThe Dataset contains
 biomass measurements (dry weight) of multiple seedlings (up to five, see
 description below) from the experiment, as described in the
 article.NSC
 Biomass.csvNSC
 DataThe Dataset contains
 measurements of non-structural carbohydrates (soluble sugars, starch) of
 multiple seedlings (up to five, see description below) from the
 experiment, as described in the article.Stomatal Conductance
 DataThe Dataset contains
 measurements of stomatal conductance (gS) of single
 seedlings.Porometer
 Data.csvLeaf Waterpotential
 DataThe Dataset contains
 measurements of pre-dawn water potential of individual seedlings, as
 described in the article.Waterpotential.csv