Scheme of the microbial nitrogen cycle under different climate change conditions.

<p>(A) comparison between NW and SW at ambient climate change (T1), (B) comparison between NW and SW at ambient/roof-intensified summer drought (T2) and (C) comparison between NW and SW after rewetting (T3, T4). Decreased N turnover processes under climate change indicated by significantly lower transcripts at SW compared to NW are shown in grey (P <0.05).</p

Thermal profiles and primer used for real-time PCR quantification of different functional genes and transcripts.

a<p>Touchdown: −1°C per cycle.</p><p>Thermal profiles and primer used for real-time PCR quantification of different functional genes and transcripts.</p

Gravimetric soil moisture related to water holding capacity (WHC), total N and C contents as well as extractable N and C pools of soil of soils at NW and SW, sampled in June (T1), after 39 days drought in August (T2), 24 and 72 hours after rewetting in August (T3, T4) and in September (T5) (n = 8, standard deviation of the mean in parentheses).

<p>Asterisks indicate significant differences between NW and SW at the respective sampling times (Student's T test), whereas lower case letters indicate differences among the sampling period for the respective site (multivariate ANOVA). Significant differences between the factors site and sampling time calculated by multivariate ANOVA are indicated by P values <0.05 (bold letters).</p><p>Gravimetric soil moisture related to water holding capacity (WHC), total N and C contents as well as extractable N and C pools of soil of soils at NW and SW, sampled in June (T1), after 39 days drought in August (T2), 24 and 72 hours after rewetting in August (T3, T4) and in September (T5) (n = 8, standard deviation of the mean in parentheses).</p

Transcript abundance of functional genes involved in the nitrogen cycle (<i>chiA</i>, <i>apr</i>, <i>amoA</i> AOA, <i>nirK</i>, <i>cnor</i> and <i>nosZ</i>) are shown for NW (black bar) and SW (grey bar) in June (T1), after 39 days drought in August (T2), 24 and 72 hours after rewetting in August (T3, T4) and in September (T5) (n = 8, error bars represent standard deviation of the mean).

<p>Asterisks indicate significant differences between NW and SW at the respective sampling times (Student's T test), whereas lower case letters indicate differences among the sampling period for the respective site (multivariate ANOVA). Significant differences between the factors site and sampling time calculated by multivariate ANOVA are indicated by P values <0.05 (bold letters).</p

Soil temperature differences (5 cm depth) between beech-soil-mesocosms incubated at SW exposure (warm-dry microclimate, climate change treatment) and at NW exposure (cool-moist microclimate, control treatment).

<p>Data represent mean values of five temperature probes per treatment directly installed horizontally in soil of transferred beech-soil-mesocosms. Arrows indicate the three sampling campaigns. The period between the sampling in June and August equals the roof period of 39 days.</p

Metabolites (total amino acids, total soluble proteins, NO₃^-) extracted from fine roots of beech seedlings in June.

<p>Blue colour represents the control treatment (NW exposure), red colour represents the climate change treatment (SW exposure). Error bars denote standard errors of the mean (n = 4 per time and treatment). Amino acid and NO₃^- metabolite levels were significantly lower in beech seedlings of the climate change treatment.</p

Gravimetric soil moisture related to water holding capacity (WHC) as determined from labelled (n = 48) and unlabelled (n = 4 to 8) beech-soil-mesocosms in June (ambient conditions at both exposures), August (intensified drought at SW exposure due to roof) and September (final harvest).

<p>Asterisks indicate significant differences (p<0.05) between NW and SW exposure at the respective harvest. Different indices indicate significant differences between different sampling dates and labelled and unlabelled beech-soil-mesocosms.</p

¹⁵N recovery (n = 8) in beech seedlings (sum of fine roots, coarse roots, stem and leaves).

<p>Data were collected in September, i.e., three months after isotope labelling with glutamine, NH₄⁺ or NO₃^- and indicate recovered % of isotopic excess, i.e., after subtracting ¹⁵N natural abundance. Blue: NW exposure (control treatment); red: SW exposure (climate change treatment). ¹⁵N recovery was highest after nitrate labelling both for SW and NW as indicated by different indices. The climate change treatment always reduced ¹⁵N recovery, as indicated by p<0.05.</p

Dynamics of volumetric soil moisture in 5 cm depth (mean values of n = 5 measurements) in intact beech-soil-mesocosms of the control treatment (NW exposure, cool-moist microclimate) and climate change treatment (SW exposure, warm-dry microclimate) in the growing season 2011, i.e., 1 year after implementation of treatments by transferring beech seedling-soil-mesocosms within NW exposure or to SW exposure in summer 2010.

<p>Arrows indicate sampling campaigns (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158823#pone.0158823.g001" target="_blank">Fig 1</a>).</p

Modelled potential distribution of beech forests on calcareous soils in Europe (green colour) under current climatic conditions (left panel).

<p>I.e., For the SRES A2 scenario, we computed a potential distribution of 7.2 million ha in the year 2080 (right panel), i.e., a reduction to 22% of the current distribution. Made with Natural Earth under CC0 license.</p