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

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

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

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

Percentage of vital root tips colonized with mycorrhizal fungi.

<p>Percentage of vital root tips colonized with mycorrhizal fungi.</p

Gross N turnover rates (mg N m^-2 day^-1) (n = 8) and N pool sizes (mg N m^-2) (N = 48) in intact beech seedling-soil-mesocosms.

<p>Blue: NW exposure (control treatment); Red: SW exposure (climate change treatment). The June sampling represents the onset of the growing season after full development of leaves, while the August sampling was conducted in the middle of the growing season after 39 days of rainfall exclusion at SW. Gross rates of N turnover were calculated based on ¹⁵N tracing and pool dilution approaches following homogeneous labelling of the intact soil with double-labelled ¹⁵N/¹³C-glutamine, ¹⁵NH₄⁺, or ¹⁵NO₃^-. Thickness of process arrows and nitrogen pool signatures is representative for respective turnover rates and pool sizes. Processes and pools significantly affected by the climate change treatment are indicated by bold letters with asterisks. Different indices show significant differences between June and August for a given treatment/exposure.</p

Ammonia oxidizing bacteria and nitrification rates.

<p>Abundance of genes encoding for ammonia monooxygenase of ammonia oxidizing bacteria in bulk soil (AOB, left panel) and relationships between AOB gene abundance and gross rates of nitrification (right panel). Blue colour: control treatment (NW exposure). Red colour: climate change treatment (SW exposure).</p

Total plant N uptake (mg N m^-2 day^-1).

<p>Total plant N uptake (mg N m^-2 day^-1).</p