Time course of the ¹³C label in plant-soil compartments of <i>Croton macrostachyus</i> and <i>Podocarpus falcatus</i> during the one year chasing period.

<p>Shown are <b>(a)</b> leaves of <i>C. macrostachyus</i>, <b>(b)</b> leaves of <i>P. falcatus</i>, <b>(c)</b> weighed sum of soluble mono and disaccharides in tree phloem sap at 1.3 m and 0.5 m above ground of <i>C. macrostachyus</i>, <b>(d)</b> weighed sum of soluble mono and disaccharides in tree phloem sap at 1.3 m and 0.5 m above ground of <i>P. falcatus</i>, <b>(e)</b> 16∶1ω5 NLFA in adhering and bulk soil under <i>C. macrostachyus</i>, <b>(f)</b> 16∶1ω5 NLFA in adhering and bulk soil under <i>P. falcatus</i>, <b>(g)</b> soil CO₂ efflux under <i>C. macrostachyus</i>, <b>(h)</b> soil CO₂ efflux under <i>P. falcatus</i> For the sake of clarity of the figure, we omitted to show the δ¹³C values for the control of soluble sugars in tree phloem sap and the 16∶1ω5 NLFA in adhering and bulk soil. The former was −25.53±0.85‰ for <i>C. macrostachyus</i> and −25.36±0.33 ‰ for <i>P. falcatus</i>, and the latter was −27.7±1.4‰ for <i>C. macrostachyus</i> and −29.3±1.1‰ for <i>P. falcatus.</i> For leaves and soil CO₂ efflux data are means ± standard deviation (n = 5). No replicates were taken for phloem sap extraction and soil cores for analysis of 16∶1ω5 NLFA in adhering and bulk soil to keep impact of destructive sampling to the plant-soil system to a minimum.</p

Time course of excess of ¹³C in total foliage biomass of <i>Croton macrostachyus</i> and <i>Podocarpus falcatus</i> during the one year chasing period.

<p>Data are means ± standard deviation (n = 5). Parameters are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045540#pone-0045540-t002" target="_blank">Table 2</a>.</p

Main characteristics of the experimental trees.

*<p>labeled tree;</p>†<p>control tree.</p

Time course of cumulative excess of ¹³C in soil CO₂ efflux under C<i>roton macrostachyus</i> and <i>Podocarpus falcatus</i> during the one year chasing period.

<p>Data are means ± standard deviation (n = 5). The curves are fitted with a double exponential function for <i>C. macrostachyus</i> and a single exponential function for <i>P. falcatus</i>. Parameters are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045540#pone-0045540-t002" target="_blank">Table 2</a>.</p

Results of the fit of exponential functions on the excess of ¹³C in leaves and the cumulative excess of ¹³C in soil CO₂ efflux related to time after labeling.

<p>Shown are the amount of labeled carbon that was recovered in a given compartment as parameters <i>a</i> and <i>c</i>, being expressed as the relative size of a fast and a slow pool, the mean residence time (MRT) and the half life of both pools, and the coefficient of determination (<i>R²</i>). Please note that the size of the pools refer to the percentage of the overall assimilated ¹³C.</p>†<p>No separation between fast and slow pool could be made.</p

Change in the apparent amount of CO₂ (mol) in chambers of <i>Croton macrostachyus</i> and <i>Podocarpus falcatus</i> during the ¹³CO₂-labeling period.

<p>The decline in the amount of CO₂ reflects the predomination of photosynthesis over leaf and stem respiration. The arrow shows the release of 12.3 mmol ¹³CO₂ m⁻³ chamber volume.</p

Properties of the microbial community.

<p>Total amount of PLFAs, fungi∶bacteria ratios and statistical results for the first three principal components derived from a PCA with relative abundances of all PLFA biomarkers. Values are mean values (± standard error) over all sites and for each horizon per site. Letters in parentheses indicate significantly different (P<0.05) groups between horizons derived from ANOVA and Tukey-HSD tests.</p

Climate and Vegetation.

<p>Climate data are derived from WorldClim database including mean annual temperature (MAT), maximum temperature of the warmest month (Tmax), minimum temperature of the coldest month (Tmin) mean annual range in temperature (MART) and mean annual precipitation (MAP).</p

Differences in microbial community composition in different horizons in arctic soils.

<p>Principal component analysis (PCA) with relative abundances of all PFLA biomarkers. Colors indicate different horizon categories: organic topsoil (O) is dark grey, mineral topsoil (A) is light grey, mineral subsoil (B) is white, and cryoturbated material (J) is black. Symbols indicate sites: circles Cherskiy, diamonds Logata, and triangles Tazovsky. Symbols are the mean values of the coordinates for the individual categories, derived from the PCA with individual samples (n = 101). Error bars are SE. Colors of PLFA markers indicate general markers (grey), gram-positive markers (red), gram-negative markers (orange), bacterial markers (blue) and fungal markers (green).</p

Direct and indirect drivers of extracellular enzyme activities.

<p>Structural equation models for extracellular enzyme activities, cellobiohydrolase (CBH; a, d), leucine-amino-peptidase (LAP; b, e) and phenoloxidase (POX; c,f). Graphs on the left show regular soil (organic topsoil, mineral topsoil, mineral subsoil), right panel shows cryoturbated material. Black boxes and arrows indicate significant factors and paths. Boxes and arrows in grey were removed from the model because either the paths (arrows) were not significant, or the factors (boxes) had no direct or indirect effect on the enzyme activity. The boxes with C, N and Clay are the contents of organic carbon, nitrogen, and clay. Microbial biomass (MicBM) was calculated as total amount of PLFAs. PC1, PC2 and PC3 are the first three axes of PCAs with relative abundances of all PLFAs. PCAs for regular soil and cryoturbated material have been done individually. Arrow width indicates the strength of the effect and reflects the scaled estimates, which are also given as the numbers beside the respective arrows. The numbers below the boxes with the respective enzymes show R² and indicate how much of the variance in enzyme activity is explained by the model.</p