Appendix A. Full explanation on the method used to generate niche-extrapolated communities from field soil moisture profiles and moisture niches.

Full explanation on the method used to generate niche-extrapolated communities from field soil moisture profiles and moisture niches

Appendix B. Supplementary results from bacterial community 16S rRNA sequencing analysis.

Supplementary results from bacterial community 16S rRNA sequencing analysis

Abundance of amoA and amoB genes in soils from Stipa tenacissima grasslands along an aridity gradient in the Mediterranean

Data on the abundance of amoA and amoB genes in soils from Stipa tenacissima grasslands along a Mediterranean aridity gradient (from Spain to Tunisia). The database also includes information about different soil variables and the abiotic characteristics of the sites surveyed. All the units and information about the variables are included in the "Metadata" spreadsheet

Carbon-Degrading Enzyme Activities Stimulated by Increased Nutrient Availability in Arctic Tundra Soils

<div><p>Climate-induced warming of the Arctic tundra is expected to increase nutrient availability to soil microbes, which in turn may accelerate soil organic matter (SOM) decomposition. We increased nutrient availability via fertilization to investigate the microbial response via soil enzyme activities. Specifically, we measured potential activities of seven enzymes at four temperatures in three soil profiles (organic, organic/mineral interface, and mineral) from untreated native soils and from soils which had been fertilized with nitrogen (N) and phosphorus (P) since 1989 (23 years) and 2006 (six years). Fertilized plots within the 1989 site received annual additions of 10 g N⋅m^-2⋅year^-1 and 5 g P⋅m^-2⋅year^-1. Within the 2006 site, two fertilizer regimes were established – one in which plots received 5 g N⋅m^-2⋅year^-1 and 2.5 g P⋅m^-2⋅year^-1 and one in which plots received 10 g N⋅m^-2⋅year^-1 and 5 g P⋅m^-2⋅year^-1. The fertilization treatments increased activities of enzymes hydrolyzing carbon (C)-rich compounds but decreased phosphatase activities, especially in the organic soils. Activities of two enzymes that degrade N-rich compounds were not affected by the fertilization treatments. The fertilization treatments increased ratios of enzyme activities degrading C-rich compounds to those for N-rich compounds or phosphate, which could lead to changes in SOM chemistry over the long term and to losses of soil C. Accelerated SOM decomposition caused by increased nutrient availability could significantly offset predicted increased C fixation via stimulated net primary productivity in Arctic tundra ecosystems. </p> </div

Activation energy of potential enzyme activities.

<p>Potential enzyme activities measured at four temperatures (5, 15, 25 and 35 °C) were used to calculate activation energy for the three soil profiles collected from the two sites. </p

Stoichiometry of potential enzyme activities in the three soil profiles collected assayed at 15 °C.

<p>C, N and P represent potential enzyme activities of (BG+CB+XYL+AG), (NAG+LAP) and PHOS, respectively. Statistically significant effects found by mixed-effect ANOVA are shown in panels: F; fertilization treatment (control, low and high fertilizations), S; site (i.e., 1989 and 2006 sites), and F×S; interaction between F and S. Symbols indicate: †; <i>p</i> ≤ 0.10, *; <i>p</i> ≤ 0.05, **; <i>p</i> ≤ 0.01, ***; <i>p</i> ≤ 0.001.</p

Relationship between soil C:N ratio and corresponding ratio of potential enzyme activities.

<p>Enzyme C and N are (BG+CB+XYL+AG) and (NAG+LAP), respectively, assayed at 15 °C. </p

C and total N contents in organic, interface and mineral soil profiles.

<p>Statistically significant effects found by mixed-effect ANOVA are shown in panels: F; fertilization treatment (control, low and high fertilizations), S; site (i.e. 1989 and 2006 sites), and F×S; interaction between F and S. Symbols indicate: †; <i>p</i> ≤ 0.10, *; <i>p</i> ≤ 0.05, **; <i>p</i> ≤ 0.01.</p

Potential enzyme activities in the three soil profiles, incubated at 15 °C.

<p>The scales of y-axes for organic and interface soils are identical. Statistically significant effects found by mixed-effect ANOVA are shown in panels: F; fertilization treatment (control, low and high fertilizations), S; site (i.e., 1989 and 2006 sites), and F×S; interaction between F and S. Symbols indicate: †; <i>p</i> ≤ 0.10, *; <i>p</i> ≤ 0.05, **; <i>p</i> ≤ 0.01.</p

Microbial biomass and community composition in soil from stands of three tree species.

<p>Microbial biomass (A) C and (B) N, (C) fungal to bacterial rRNA gene ratio, and (D) fungal and (E) bacterial community composition (based on NMS ordination scores) in stands of each species. Values are means±SE and letters denote significant differences (<i>P</i> = 0.05) among tree species (upper and lower case letters refer to NMS axis 2 and 3, respectively, for bacterial community composition).</p