Publications

Elevated temperature and CO2 strongly affect the growth strategies of soil bacteria

The trait-based strategies of microorganisms appear to be phylogenetically conserved, but acclimation to climate change may complicate the scenario. To study the roles of phylogeny and environment on bacterial responses to sudden moisture increases, we determine bacterial population-specific growth rates by 18 O-DNA quantitative stable isotope probing ( 18 O-qSIP) in soils subjected to a free-air CO 2 enrichment (FACE) combined with warming. We find that three growth strategies of bacterial taxa – rapid, intermediate and slow responders, defined by the timing of the peak growth rates – are phylogenetically conserved, even at the sub-phylum level. For example, members of class Bacilli and Sphingobacteriia are mainly rapid responders. Climate regimes, however, modify the growth strategies of over 90% of species, partly confounding the initial phylogenetic pattern. The growth of rapid bacterial responders is more influenced by phylogeny, whereas the variance for slow responders is primarily explained by environmental conditions. Overall, these results highlight the role of phylogenetic and environmental constraints in understanding and predicting the growth strategies of soil microorganisms under global change scenarios.

Clay Differentiation in Initially Homogeneous Substrates upon Long-term Field Experiments

No abstract is provided for this article.

Plant-mediated effects on extracellular enzyme activities in distinct soil aggregate size classes in field

No abstract is provided for this article.

Response of bacterial and fungal composition in tailings to Mn pollution

Nonlinear temperature sensitivity of enzyme kinetics explains canceling effect—a case study on loamy haplic Luvisol

The temperature sensitivity of enzymes responsible for organic matter decomposition in soil is crucial for predicting the effects of global warming on the carbon cycle and sequestration. We tested the hypothesis that differences in temperature sensitivity of enzyme kinetic parameters V max and K m will lead to a canceling effect: strong reduction of temperature response of catalytic reactions. Short-term temperature response of V max and K m of three hydrolytic enzymes responsible for decomposition of cellulose (β-glucosidase, cellobiohydrolase) and hemicelluloses (xylanase) were analyzed in situ from 0 to 40°C. The apparent activation energy varied between enzymes from 20.7 to 35.2 kJ mol(-1) corresponding to the Q 10 values of the enzyme activities of 1.4-1.9 (with V max - Q 10 1.0-2.5 and K m - Q 10 0.94-2.3). Temperature response of all tested enzymes fitted well to the Arrhenius equation. Despite that, the fitting of Arrhenius model revealed the non-linear increase of two cellulolytic enzymes activities with two distinct thresholds at 10-15°C and 25-30°C, which were less pronounced for xylanase. The nonlinearity between 10 and 15°C was explained by 30-80% increase in V max . At 25-30°C, however, the abrupt decrease of enzyme-substrate affinity was responsible for non-linear increase of enzyme activities. Our study is the first demonstrating nonlinear response of V max and K m to temperature causing canceling effect, which was most strongly pronounced at low substrate concentrations and at temperatures above 15°C. Under cold climate, however, the regulation of hydrolytic activity by canceling in response to warming is negligible because canceling was never observed below 10°C. The canceling, therefore, can be considered as natural mechanism reducing the effects of global warming on decomposition of soil organics at moderate temperatures. The non-linearity of enzyme responses to warming and the respective thresholds should therefore be investigated for other enzymes, and incorporated into Earth system models to improve the predictions at regional and global levels.

Carbon balance and C pools in the former agricultural lands of Russia

Carbon input by plants into the soil. Review

The methods used for estimating below-ground carbon (C) translocation by plants, and the results obtained for different plant species are reviewed. Three tracer techniques using C isotopes to quantify root-derived C are discussed: pulse labeling, continuous labeling, and a method based on the difference in 13C natural abundance in C3 and C4 plants. It is shown, that only the tracer methods provided adequate results for the whole below-ground C translocation. This included roots, exudates and other organic substances, quickly decomposable by soil microorganisms, and CO2 produced by root respiration. Advantages due to coupling of two different tracer techniques are shown. The differences in the below-ground C translocation pattern between plant species (cereals, grasses, and trees) are discussed. Cereals (wheat and barley) transfer 20%—30% of total assimilated C into the soil. Half of this amount is subsequently found in the roots and about one-third in CO2 evolved from the soil by root respiration and microbial utilization of rootborne organic substances. The remaining part of below-ground translocated C is incorporated into the soil microorganisms and soil organic matter. The portion of assimilated C allocated below the ground by cereals decreases during growth and by increasing N fertilization. Pasture plants translocated about 30%—50% of assimilates below-ground, and their translocation patterns were similar to those of crop plants. On average, the total C amounts translocated into the soil by cereals and pasture plants are approximately the same (1500 kg C ha—1), when the same growth period is considered. However, during one vegetation period the cereals and grasses allocated beneath the ground about 1500 and 2200 kg C ha—1, respectively. Finally, a simple approach is suggested for a rough calculation of C input into the soil and for root-derived CO2 efflux from the soil. Kohlenstoffeintrag in Böden durch Pflanzen In diesem Review werden Methoden zur Einschätzung der Translokation von Kohlenstoff (C) in Böden durch Pflanzen und entsprechende Ergebnisse für unterschiedliche Pflanzengruppen diskutiert. Drei Methoden unter Verwendung von C-Isotopen als Tracer für wurzelbürtigen C werden vorgestellt: Pulsmarkierung, kontinuierliche Markierung und die Methode, die auf dem Unterschied in der natürlichen 13C-Abundanz von C3- und C4-Pflanzen basiert. Es wird gezeigt, dass nur die Tracer-Methoden adäquate Ergebnisse zur unterirdischen Translokation des gesamten wurzelbürtigen Kohlenstoffs liefern. Die Vorteile der Kopplung von zwei unterschiedlichen Tracer-Methoden werden gezeigt. Die Unterschiede im Muster der unterirdischen C-Translokation zwischen den Pflanzengruppen (Getreide, Weidegräser und Bäume) werden untersucht und in Tabellen zusammengefasst. Getreide (Weizen und Gerste) bringen 20%—30% des gesamten assimilierten C unter die Bodenoberfläche. Die Hälfte dieser Menge wird anschließend in den Wurzeln wiedergefunden. Ein Drittel verlässt den Boden als CO2, das durch Wurzelatmung und mikrobielle Veratmung der wurzelbürtigen organischen Substanzen entsteht. Der Rest des durch die Wurzeln in den Boden eingebrachten C wird in die mikrobielle Biomasse und in die organische Bodensubstanz eingebaut. Der Anteil des assimilierten C, der in den Boden durch Getreide eingebracht wird, verringert sich im Laufe der Pflanzenentwicklung und mit steigender N-Düngung. Die Weidegräser transportieren sogar 30%—50% des assimilierten C in den Boden, aber die Relation zwischen den einzelnen Pools bzw. Flüssen ist ähnlich wie beim Getreide. Sowohl Getreide als auch Weidegräser transportieren durchschnittlich ca. 1500 kg C ha—1 in den Boden bei Voraussetzung gleich langer Wachstumsperioden. Bei Berücksichtigung einer vollen Vegetationsperiode transportieren die Weidegräser ca. 600 kg C ha—1 mehr in den Boden als Getreidekulturen. Eine einfache Methode zur groben Kalkulation der durch Pflanzen in den Boden eingebrachten C-Mengen und des wurzelbürtigen CO2-Effluxes aus dem Boden wird vorgeschlagen.

Aboveground and Belowground Plant Traits Explain Latitudinal Patterns in Topsoil Fungal Communities From Tropical to Cold Temperate Forests

Soil fungi predominate the forest topsoil microbial biomass and participate in biogeochemical cycling as decomposers, symbionts, and pathogens. They are intimately associated with plants but their interactions with aboveground and belowground plant traits are unclear. Here, we evaluated soil fungal communities and their relationships with leaf and root traits in nine forest ecosystems ranging from tropical to cold temperate along a 3,700-km transect in eastern China. Basidiomycota was the most abundant phylum, followed by Ascomycota, Zygomycota, Glomeromycota, and Chytridiomycota. There was no latitudinal trend in total, saprotrophic, and pathotrophic fungal richness. However, ectomycorrhizal fungal abundance and richness increased with latitude significantly and reached maxima in temperate forests. Saprotrophic and pathotrophic fungi were most abundant in tropical and subtropical forests and their abundance decreased with latitude. Spatial and climatic factors, soil properties, and plant traits collectively explained 45% of the variance in soil fungal richness. Specific root length and root biomass had the greatest direct effects on total fungal richness. Specific root length was the key determinant of saprotrophic and pathotrophic fungal richness while root phosphorus content was the main biotic factor determining ectomycorrhizal fungal richness. In contrast, spatial and climatic features, soil properties, total leaf nitrogen and phosphorus, specific root length, and root biomass collectively explained >60% of the variance in fungal community composition. Soil fungal richness and composition are strongly controlled by both aboveground and belowground plant traits. The findings of this study provide new evidence that plant traits predict soil fungal diversity distribution at the continental scale.

Priming effects in Chernozem induced by glucose and N in relation to microbial growth strategies

Input of easily available C and N sources increases microbial activity in soil and may induce priming effects (PE)—short-term changes in SOM decomposition after substrate addition. The relationship between the origin of priming and growth characteristics of the microbial community is still unclear. We related real and apparent PEs induced by glucose and N addition with growth strategies of soil microorganisms. Two concentrations of uniformly labeled 14C glucose with and without N were added to Chernozem, and the released 14CO2 and CO2 efflux were monitored over a 300h period. The shift in strategies after glucose addition was monitored by microbial growth kinetics based on the estimation of maximal specific growth rate. The production of unlabelled extra CO2 induced by glucose was completed after 3 days and amounted to about 15–19% of the microbial biomass-C. The presence of real or apparent PE depended on the level of added C and N. An apparent positive PE was observed when the amount of applied glucose-C was 13 times lower than the amount of microbial biomass-C, i.e. under C-limiting conditions. Apparent PE was accompanied by a higher maximal microbial specific growth rate, i.e. by a shift towards r-strategy features. The absence of a priming effect was observed under N-limiting conditions at an eightfold excess of glucose-C versus microbial biomass-C. A large excess of glucose and N lowered maximal specific growth rates of soil microorganisms and had a negative priming effect. Accordingly, slow-growing microorganisms (K-strategists) switched from SOM mineralization to glucose uptake, probably due to preferential substrate utilization. Analysis of microbial growth kinetics was an efficient approach for evaluating short-term changes in the response of microorganisms to substrate addition; this approach is therefore suitable for assessing transitions between K and r strategies.

Die unterschätzte Rolle des Recyclings intakter Metabolite für die Umsatzraten der organischen Bodensubstanz

Obwohl Sorption an Mineraloberflachen als dominierender Prozess zur Erklarung des langsamen Umsatzes mineralassoziierter organischer Bodensubstanz (OBS) dient, widerspricht diese Idee einer zunehmenden Zahl an Inkubationsstudien, die zeigen, dass fur niedermolekulare Substanzen nicht nur die mikrobielle Aufnahme kompetitivier als die Sorption ist, sondern auch sorbierte Substanzen in hohem Mase desorbiert und mikrobiell verwertet werden konnen. Dabei wurde gezeigt, dass sich die Verstoffwechselung desorbierter Substanzen zugunsten eines erhohten Recyclings verschiebt. Dies wirft die Frage auf, ob Recycling von intakten Metaboliten, d.h. unter Erhalt des Kohlenstoffgerustes, generell ein bisher stark unterschatzter Prozess ist, der die relativ hohen 14C Alter der OBS teilweise erklaren kann. Nach Applikation hoher Toxindosen konnte nachgewiesen werden, dass die nachfolgende Reetablierung der mikrobiellen Gemeinschaft zu grosem Anteil auf Recycling der Nekromasskomponenten der Vorgeneration basiert. Intaktes Metabolitrecycling ist jedoch unter steady-state Bedingungen nur auserst schwierig von der direkten Stabiliserung zu unterscheiden. Um diesen Prozess im Fliesgleichgewicht nachzuweisen muss 1) ein Biomolekul untersucht werden, dessen Biosyntheseweg so aufwandig ist, dass Recycling einen deutlichen Vorteil fur die Zelle im Vergleich zur Neusynthese darstellt, 2) dieses Biomolkul in lebenden Zellen in einer anderen Form gebunden sein, als die zu recycelnde Einheit in der Bodenlosung, so dass beide Zustandsformen unterschieden werden konnen und 3) dieses Biomolekul positionsspezifisch isotopenmarkiert zugegeben werden, so dass uber einen identischen Einbau der Positionen die Intaktheit des Kohlenstoffgerustes nachgewiesen werden kann. Am Beispiel der Alkylketten von Fettsauren, die in mikrobiellen Zellen primar als Phospholipide in den Membranen gebunden sind, soll dieses Prinzip veranschaulicht werden. Eine erste Abschatzung des intakten Recyclings von Alkylketten durch Mikroorganismen in Boden zeigt, dass von den 0.03% der basierend auf Alkyl-Kohlenstoff neugebildeten PLFA mehr als 75% aus intaktem Recycling dieser Ketten hervor gingen. Obwohl der Beitrag des Recyclings intakter Metabolite zur Umsatzzeit der gesamten OBS aufgrund der geringen Anzahl bisher untersuchter Metabolite noch nicht final quantifiziert werden kann, untermauern die hier vorgestellten Ergebnisse jedoch die hohe Relevanz dieses Prozesses fur die Dynamik der OBS.

Microbial processing of plant residues in the subsoil – The role of biopores

Most subsoil carbon (C) turnover occurs in biopore hotspots such as root channels and earthworm burrows. Biopores allocate large C amounts into the subsoil, where a vast capacity for long-term C sequestration is predicted. We hypothesise that organic matter (OM) cycling in biopores depends on their origin. Earthworm and root biopores were induced under field conditions and were sampled from the subsoil (45–75 and 75–105 cm) after two years of biopore formation. The effects of biopore formation on OM decomposition were studied by biomarkers: neutral sugars, cutin and suberin-derived lipids, lignin-derived phenols and free lipids. The degradation stage of OM was biopore type-specific but was only governed by the soil depth in root biopores. Degradation of OM increased from earthworm biopores to root biopores and bulk soil. Hemicelluloses (GM/AX ratio) were more strongly degraded than lignin side-chains (relative change from initial values). Two years of microbial processing during biopore formation increased the GM/AX ratio in earthworm biopores from 0.65 to 1.05 and in root biopores from 0.15 to 1.35 (both relative to source biomasses). Root biopores and bulk soil had the highest GM/AX ratios (1.2–1.3), hinting to rapid processing of plant residues and accumulation of microbial residues. The regular, frequent OM inputs by earthworms stimulated microbial growth and processing of mostly bioavailable OM and, thus, relatively enriched more persistent OM (e.g. lignin). Syringyl subunits of lignin underwent low (ratio changed from 0.35 to 0.55 relative to initial input) and vanillyl subunits underwent almost no processing in earthworm biopores indicating the preferential microbial utilisation of the easily available compounds frequently replenished by earthworm activity. After two years of decomposition of the root detritus, mainly structural plant material was enriched in root biopores. Short periods (6 months) of earthworm activity effectively recharged the highly processed OM in root biopores with fresh OM. In total, deep-rooting catch crops and short-term earthworm activities promote C accumulation in the subsoil followed by biopore-specific microbial processing predominantly governed by the C input frequency. As root biopores are up to 40 times more common than earthworm biopores, they dominate the OM input into subsoils. Such C inputs create several years lasting hotspots for preferential root growth and nutrient mobilisation in the subsoil. We conclude that root- and earthworm-derived biopores are vertical pathways for plant C from the soil surface into the subsoil and for intensive processing of litter C and sequestration of microbial necromass.

Phages Affect Soil Dissolved Organic Matter Mineralization by Shaping Bacterial Communities

Viruses are considered to regulate bacterial communities and terrestrial nutrient cycling, yet their effects on bacterial metabolism and the mechanisms of carbon (C) dynamics during dissolved organic matter (DOM) mineralization remain unknown. Here, we added active and inactive bacteriophages (phages) to soil DOM with original bacterial communities and incubated them at 18 or 23 °C for 35 days. Phages initially (1–4 days) reduced CO2 efflux rate by 13-21% at 18 °C and 3–30% at 23 °C but significantly (p < 0.05) increased by 4–29% at 18 °C and 9–41% at 23 °C after 6 days, raising cumulative CO2 emissions by 14% at 18 °C and 21% at 23 °C. Phages decreased dominant bacterial taxa and increased bacterial community diversity (consistent with a "cull-the-winner" dynamic), thus altering the predicted microbiome functions. Specifically, phages enriched some taxa (such as Pseudomonas, Anaerocolumna, and Caulobacter) involved in degrading complex compounds and consequently promoted functions related to C cycling. Higher temperature facilitated phage-bacteria interactions, increased bacterial diversity, and enzyme activities, boosting DOM mineralization by 16%. Collectively, phages impact soil DOM mineralization by shifting microbial communities and functions, with moderate temperature changes modulating the magnitude of these processes but not qualitatively altering their behavior.

Arbuscular mycorrhiza enhances rhizodeposition and reduces the rhizosphere priming effect on the decomposition of soil organic matter

Arbuscular mycorrhizal fungi (AMF) represent an important route for plant carbon (C) inputs into the soil. Nonetheless, the C input via AMF as well as its impact on soil organic matter (SOM) stabilization and C sequestration remains largely unknown. A mycorrhizal wild type progenitor (MYC) and its mycorrhiza defective mutant (reduced mycorrhizal colonization: rmc) of tomato were continuously labeled with 13CO2 to trace root C inputs into the soil and quantify rhizosphere priming effects (RPE) as affected by AMF symbiosis and N fertilization. Mycorrhizal abundance and 13C incorporation into shoots, roots, soil and CO2 were measured at 8, 12 and 16 weeks after transplanting. AMF symbiosis decreased the relative C allocation (% of total assimilated C) to roots, in turn increased the net rhizodeposition. Positive RPE was recorded for both MYC and rmc plants, ranging from 16–71% and 25–101% of the unplanted control, respectively. Although net rhizodeposition was higher for MYC than rmc plants 16 weeks after transplanting, the RPE was comparatively lower. This indicated a higher potential for C sequestration by plants colonized with AMF (MYC) because the reduced nutrient availability restricts the activity of free-living decomposers. Although N fertilization decreased the relative C allocation to roots, rhizosphere and bulk soil, it had no effect on the absolute amount of rhizodeposition to the soil. The RPE and N-cycling enzyme activities decreased by N fertilization 8 and 12 weeks after transplanting, suggesting a lower microbial N demand from SOM mining. The positive relationship between enzyme activities involved in C cycling, microbial biomass C and SOM decomposition underlines the microbial activation hypothesis, which explains the RPE. We therefore concluded that AMF symbiosis and N fertilization increase C sequestration in soil not only by increasing root C inputs, but also by lowering native SOM decomposition and RPE.

Microbial utilization of litter carbon under the effect of extreme weather events

No abstract is provided for this article.

Source determination of lipids in bulk soil and soil density fractions after four years of wheat cropping

Preservation of soil organic matter (SOM) is strongly affected by occlusion within aggregates and by association of SOM with minerals. Protection of organic carbon (C) due to adsorption to mineral surfaces can be assessed by investigation of SOM in soil density fractions. Apart from the physical properties the preservation of SOM is affected by its chemical composition. While for bulk organic C this was demonstrated for numerous soils, SOM density fractions have been scarcely studied regarding their molecular composition. Lipids as a compound class that can derive from plants, microorganisms and contamination by products from incomplete combustion or fossil carbon were not investigated in density fractions so far. We hypothesized that molecular proxies deriving from lipid composition yield a large potential to elucidate the sources of organic matter entering soil, and in combination with density fractions they enable the identification of incorporation and preservation pathways of SOM. We determined distribution patterns of aliphatic hydrocarbons and fatty acids as two representative groups for total lipids in soil density fractions. The fatty acids showed a predominant input of plant-derived poly unsaturated short chain and saturated long chain fatty acids in free particulate organic matter (fPOM). The microorganism-derived compounds such as unsaturated short chain fatty acids were largely abundant in fPOM and especially in occluded particulate organic matter (oPOM 1.6). The proportion of plant-derived components like long chain fatty acids increased with increasing density of the fractions, whereas the abundance of short chain fatty acids decreased in the same direction as indicated by the ratio of long chain vs. short chain fatty acids. The main portion of soil lipids (60% of total lipids) was recovered in the mineral (Min) fraction, which denotes the strongest protection of lipids adsorbed to mineral surfaces. For the aliphatic hydrocarbons the contribution of plant- and microorganism-derived components was the largest in fPOM. Short chain alkanes as part of the aliphatic hydrocarbons showed contamination of soil by an incompletely burned plant biomass or fossil carbon. These contaminants were the most abundant in fPOM and subsequently attributed to particles with a low density, which derived probably from soot. However, a large contribution of fossil C was found in the Min fraction as well, which is thought to be attributed to degraded soot particles being adsorbed to minerals. We demonstrated at the molecular level that the incorporation of individual C sources varies with the density fractions. It was found that microorganism-derived compounds were most abundant in fPOM and oPOM 1.6 fractions, whereas plant-derived long chain biopolymers were enriched in mineral dominated fractions (oPOM 2.0 and especially Min). Thus, preservation of plant-derived lipids in soil is strongly attributed to the association with minerals. Based on lipid composition in density fractions we evaluated several molecular proxies, which help to elucidate the sources of SOM.

Priming effect stimulates carbon release from thawed permafrost

This dataset is composed of two datasets, Dataset1 includes geographic location, soil layer thickness, soil organic carbon, bulk density, soil organic carbon density, basal mirobial respiration, cumulative priming effect and relative priming effect across 24 sampling sites on the Tibetan Plateau. Dataset2 includes CO2 emission rate and δ13C values across 24 sampling sites during the 60-day incubation. At each site, both CO2 emission rate and δ13C values of three parallel samples were measured for 9 times on days 1, 2, 4, 9, 15, 22, 30, 45, and 60.

Effects of flooding on phosphorus and iron mobilization in highly weathered soils under different land-use types: Short-term effects and mechanisms

The strong affinity of phosphorus (P) to iron (Fe) oxides and hydroxides in highly weathered tropical soils limits P availability and therefore plant productivity in tropics. In flooded soils, however, P fixed by Fe oxides and hydroxides can be released into more available forms because of Fe3+ reduction to Fe2+. These P dynamics in flooded soils are well documented for rice paddies. Such effects are much less studied in other land-use types influenced by seasonal flooding, especially in the tropics during heavy monsoon rains. The aim of this study was to investigate the P mobilization during flooding leading to anaerobic conditions in topsoil and subsoil depending on land-use type. Samples were collected in highly weathered Acrisols from four replicate sites under natural rainforest, jungle rubber, rubber and oil palm plantations in Sumatra, Indonesia. Topsoil and subsoil were taken to ensure a wide range of soil organic matter (SOM) and P contents. Soils were incubated under anaerobic, flooded conditions at 30±1°C for 60days. Our results confirmed the hypothesis that soil flooding mobilizes P and increases P availability. Two distinct and opposite periods were observed during the flooding. During the first three weeks of flooding, the dissolved P (DP) concentration peaked, simultaneously with the peak of dissolved Fe2+ (DFe2+) and dissolved organic carbon (DOC). After three weeks, P availability in soils decreased, although Fe-P (PNaOH) and available P (PNaHCO3) did not reach the initial, pre-flooding levels. The impacts of flooding on P and Fe forms was strong in the topsoil, where P dissolution and availability were generally higher under forest and, to a lesser extent, under jungle rubber. A positive correlation between DOC and DFe2+ (R2 =0.42) in topsoil indicates that the intensity of microbially-mediated Fe3+ reduction is limited by the amount of available carbon (C) as an energy source for microorganisms and as electron donor. Microbial mineralization of organic P from SOM also increases P availability, and this process requires available C. This interpretation was supported by the strong correlation (R2 =0.58) between available P and DOC, as well as between DP and DOC (R2 =0.56) in topsoil. The increasing pH in topsoil and subsoil after flooding of all land-use types may also influence the P release over time. In summary, the increase of available P and DP during flooding is due to three main mechanisms: (1) P release via the microbially-mediated reductive dissolution of Fe3+ oxides; (2) P release during SOM mineralization and (3) solubility of Fe phosphate due to increasing pH. These mechanisms are relevant not only in riparian areas, where flooding occurs, but also in soils waterlogged after regular heavy rainfalls during the wet season. Therefore, we speculate that the P turnover is faster in compacted soils under plantations because of regular changes of oxic and anoxic conditions. Consequently, more P is pumped by the vegetation and then removed from plantations due to yield export.

Microbial Carbon Use Efficiency and Growth Rates in Soil: Global Patterns and Drivers

Carbon use efficiency (CUE) of microbial communities in soil quantifies the proportion of organic carbon (C) taken up by microorganisms that is allocated to growing microbial biomass as well as used for reparation of cell components. This C amount in microbial biomass is subsequently involved in microbial turnover, partly leading to microbial necromass formation, which can be further stabilized in soil. To unravel the underlying regulatory factors and spatial patterns of CUE on a large scale and across biomes (forests, grasslands, croplands), we evaluated 670 individual CUE data obtained by three commonly used approaches: (i) tracing of a substrate C by 13 C (or 14 C) incorporation into microbial biomass and respired CO 2 (hereafter 13 C‐substrate), (ii) incorporation of 18 O from water into DNA ( 18 O‐water), and (iii) stoichiometric modelling based on the activities of enzymes responsible for C and nitrogen (N) cycles. The global mean of microbial CUE in soil depends on the approach: 0.59 for the 13 C‐substrate approach, and 0.34 for the stoichiometric modelling and for the 18 O‐water approaches. Across biomes, microbial CUE was highest in grassland soils, followed by cropland and forest soils. A power‐law relationship was identified between microbial CUE and growth rates, indicating that faster C utilization for growth corresponds to reduced C losses for maintenance and associated with mortality. Microbial growth rate increased with the content of soil organic C, total N, total phosphorus, and fungi/bacteria ratio. Our results contribute to understanding the linkage between microbial growth rates and CUE, thereby offering insights into the impacts of climate change and ecosystem disturbances on microbial physiology with consequences for C cycling.