DOI: 10.5061/dryad.rxwdbrv5n
title: Data from: Soils from cold and snowy temperate deciduous forests release more nitrogen and phosphorus after soil freeze–thaw cycles than soils from warmer, snow-poor conditions

description: Effects of global warming are most pronounced in winter. A reduction in
 snow cover due to warmer atmospheric temperature in formerly cold
 ecosystems, however, could counteract an increase in soil temperature by
 reduction of insulation. Thus, soil freeze-thaw cycles (FTC) might
 increase in frequency and magnitude with warming, potentially leading to a
 disturbance of the soil biota and release of nutrients. Here, we assessed
 how soil freeze-thaw magnitude and frequency affect short-term release of
 nutrients in temperate deciduous forest soils by conducting a three
 factorial gradient experiment with ex-situ soil samples in climate
 chambers. The fully-crossed experiment included soils from forests
 dominated by Fagus sylvatica (European beech) that originate from
 different winter climate (mean coldest month temperature range ΔT &gt;
 4 K), a range of FTC magnitudes from no (T = 4.0 °C) to strong (T = -11.3
 °C) soil frost, and a range of FTC frequencies (f = 0–7). We hypothesized
 that higher FTC magnitude and frequency, respectively, will increase the
 release of nutrients. Furthermore, soils from cold climates with
 historically stable winter soil temperatures due to deep snow cover will
 be more responsive to FTC than soils from warmer, more fluctuating winter
 soil climates. FTC magnitude and, to a lesser extent, also FTC frequency
 resulted in increased nitrate, ammonium, and phosphate release almost
 exclusively in soils from cold, snow-rich sites. The hierarchical
 regression analyses of our three-factorial gradient experiment revealed
 that the effects of climatic origin (mean minimum winter temperature)
 followed a sigmoidal curve for all studied nutrients and was modulated
 either by FTC magnitude (phosphate) or by FTC magnitude and frequency
 (nitrate, ammonium) in complex two- and, for all studied nutrients, in
 threefold interactions of the environmental drivers. Compared to initial
 concentrations, soluble nutrients were predicted to increase to
 250 % for nitrate (up to 16 µg NO3-N kg-1DM), to 110 %
 for ammonium (up to 60 µg NH4-N kg-1DM), and to 400 % for
 phosphate (2.2 µg PO4-P kg-1DM) at the coldest site for strongest
 magnitude and highest frequency. Soils from warmer sites showed little
 nutrient release and were largely unaffected by the FTC treatments except
 for above-average nitrate release at the warmest sites in response to
 extremely cold FTC magnitude. We suggest that currently warmer forest
 soils have historically already passed the point of high responsiveness to
 winter climate change, displaying some form of adaptation either in the
 soil biotic composition or in labile nutrient sources. Our data suggests
 that previously cold sites, which will lose their protective snow cover
 during climate change, are most vulnerable to increasing FTC frequency and
 magnitude, resulting in strong shifts in nitrogen and phosphorus release.
 In nutrient poor European beech forests of the studied Pleistocene
 lowlands, nutrients released over winter may be leached out, inducing
 reduced plant growth rates in the following growing season. Here, we
 provide the raw data of a three-factorial regression experiment and the
 R-Code used in the hierarchical regression analysis of this raw data in
 Kreyling et al.: Soils from cold and snowy temperate deciduous forests
 release more nitrogen and phosphorus after soil freeze-thaw cycles than
 soils from warmer, snow-poor conditions.
description: for details see publication Kreyling et al.
description: The R-script reads in the provided raw data and contains the full
 hierarchical regression analysis as presented in the published paper
 including additional R-packages and creation of the figures. The raw data
 is the same dataset as used in the publication.