Microbial diversity drives carbon use efficiency in a model soil

Arbuscular Mycorrhizal Fungi and Soil Quality Indicators in Eucalyptus genotypes With Different Drought Tolerance Levels

Silviculture has great importance worldwide, and the use of Eucalyptus species, which account for 75% of the local planted forest in Brazil, is one of the factors that contributes to the success of this activity in the country. Despite its adaptability, the yield of Eucalyptus is often affected by climate change, particularly water deficiency. Plants have developed strategies to mitigate water stress, for example, through their association with mycorrhizal fungi. The genus Eucalyptus, particularly in the plant domain, establishes symbioses with arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi (ECMF). The influence of Eucalyptus species on AMF and soil quality indicators is not well understood. Our aim was to conduct a preliminary evaluation of the various responses of soil AMF communities and soil nutrient dynamics in the presence of Eucalyptus species with different degrees of drought tolerance. A field experiment was established containing six Eucalyptus species, E. brassiana, E. camaldulensis, E. citriodora, E. cloeziana, E. grandis, and E. urophylla, all of which were planted in large plots. Soil and root samples were taken when the plants were 1.7 and 2.2 years old. We found that Eucalyptus species with low (E. grandis and E. urophylla) and intermediate drought tolerance (E. citriodora and E. cloeziana) showed stronger correlations with the AMF community than Eucalyptus species with high drought tolerance (E. brassiana and E. camaldulensis). Differences were also found between Eucalyptus species for AMF spore numbers and root colonization percentages, which was most evident for E. urophylla. The microbiological attributes found to be most responsive to Eucalyptus species were soil enzyme activities, AMF spore numbers, root colonization percentages, and fungal abundance. Soil organic carbon, phosphorus, potassium, zinc, copper, and iron were the main chemical drivers related to the soil AMF community structure in the presence of E. brassiana.

Microbial diversity drives pyrene dissipation in soil

Soil microbial diversity is an essential driver of multiple ecosystem functions and services. However, the role and mechanisms of microbial diversity in the dissipation of persistent organic pollutants in soil are largely unexplored. Here, a gradient of soil microbial diversity was constructed artificially by a dilution-to-extinction approach to assess the role of soil microbial diversity in the dissipation of pyrene, a high molecular weight polycyclic aromatic hydrocarbon (PAH), in a 42-day microcosm experiment. The results showed that pyrene dissipation (98.1%) and the abundances of pyrene degradation genes (the pyrene dioxygenase gene nidA and the gram-positive PAH-ring hydroxylating dioxygenase gene PAH-RHDα GP) were highest in soils with high microbial diversity. Random-forest machine learning was combined with linear regression analysis to identify a range of keystone taxa (order level) associated with pyrene dissipation, including Sphingobacteriales, Vampirovibrionales, Blastocatellales, Myxococcales, Micrococcales and Rhodobacterales. The diversity of these keystone taxa was significantly and positively correlated with the abundance of pyrene degradation genes and the removal rate of pyrene. According to (partial) Mantel tests, keystone taxa diversity was the dominant factor determining pyrene dissipation compared with total microbial diversity. Moreover, co-occurrence network analysis revealed that diverse keystone taxa may drive pyrene dissipation via more positive interactions between keystone species and with other species in soil. Taken together, these findings provide new insights on the regulation of keystone taxa diversity to promote the dissipation of PAH in soil.

Rare-earth metal oxide nanoparticles decouple the linkage between soil bacterial community structure and function by selectively influencing potential keystone taxa

Excessive production and application of rare-earth metal oxide nanoparticles warrants assessment of their environmental risks. Little is known about the impact of these nanoparticles on soil bacterial communities. We quantified the effects of nano-Gd₂O₃ and nano-La₂O₃, at the different concentrations and exposure regimes, on soil bacterial community structure and function as well as the structure-function relationship. Further, we constructed and analyzed a co-occurrence network to identify and characterize potential keystone taxa that were related to the enzyme activities and responded to the increasing concentrations of nanoparticles. Both nano-Gd₂O₃ and nano-La₂O₃ significantly altered the bacterial community structure and function in a concentration-dependent manner; however, these negative effects were observed on day 1 or day 7 but not on day 60, indicating that these effects were transient and the bacterial communities can mitigate the effect of these nanoparticles over time. Interestingly, the nanoparticle exposure decoupled the relationship between the structure and function of the soil bacterial communities. The decoupling was due to changes in the composition and relative abundances of potential keystone taxa related to bacterial community functions. Altogether, we provide insights into the interactions between the rare-earth metal oxide nanoparticles and soil bacterial communities. Our results facilitate the environmental risk assessment and safe usage of rare-earth metal oxide nanoparticles.

Draft Genome Sequence of Leifsonia poae Strain BS71, Isolated from a Drought Microcosm

We report the draft genome sequence of Leifsonia poae strain BS71. This bacterium was isolated from a low soil moisture content model soil microcosm inoculated with forest soil that had been subject to chronic warming.

Mechanism of bio-electrokinetic remediation of pyrene contaminated soil: Effects of an electric field on the degradation pathway and microbial metabolic processes

In this study, the mechanism of bio-electrokinetic (BIO-EK) remediation to improve the degradation of pyrene was evaluated based on an analysis of the intermediate products and the microbial community. The results show that BIO-EK remediation has a higher pyrene degradation efficiency on pyrene and its intermediate products than the bioremediation and electrokinetic (EK) remediation processes. A series of intermediate products were detected. According to the type of the intermediate products, two degradation pathways, biological metabolism and electrochemical oxidation, are proposed in the BIO-EK remediation of pyrene. Furthermore, the primary microbial taxa involved in the pollutant degradation changed, which led to variations in the functional gene components. The abundant and functional genes related to metabolism were specifically analyzed. The results indicate that the electric field promotes the expression of metabolisms associated with 14 carbohydrates, 13 lipids, 13 amino acids, five energies, and in particular, 11 xenobiotics. These results suggest that in addition to the promotion effect on the microbial metabolism caused by the electric field, BIO-EK remediation can promote the degradation of pollutants due to the coexistence of a microbial metabolic pathway and an electrochemical oxidation pathway.

Direct evidence for the role of microbial community composition in the formation of soil organic matter composition and persistence

The largest terrestrial carbon sink on earth is soil carbon stocks. As the climate changes, the rate at which the Earth's climate warms depends in part on the persistence of soil organic carbon. Microbial turnover forms the backbone of soil organic matter (SOM) formation and it has been recently proposed that SOM molecular complexity is a key driver of stability. Despite this, the links between microbial diversity, chemical complexity and biogeochemical nature of SOM remain missing. Here we tested the hypotheses that distinct microbial communities shape the composition of SOM, and microbial-derived SOM has distinct decomposition potential depending on its community of origin. We inoculated microbial communities of varying diversities into a model soil matrix amended with simple carbon (cellobiose) and measured the thermal stability of the resultant SOM. Using a Rock-Eval® ramped thermal analysis, we found that microbial community composition drives the chemical fingerprint of soil carbon. While diversity was not a driver of SOM composition, bacteria-only communities lead to more thermally labile soil C pools than communities with bacteria and fungi. Our results provide direct evidence for a link between microbial community structure, SOM composition, and thermal stability. This evidence demonstrates the relevance of soil microorganisms in building persistent SOM stocks.

Evaluation of cornstalk as bulking agent on greenhouse gases emission and bacterial community during further composting

The aim of current work was to explore the impact of Cornstalk (CS) on greenhouse gaseous emission and maturation during further composting and analyzed its impact on bacterial diversity. Three kinds of immature fertilizers were collected from chicken, pig and dairy manure namely T1, T2 and T3 as control, T4, T5 and T6 were added CS into T1 to T3 and adjusted C/N to 25 namely treatment. The results illustrated that gases (N2O, CH4 and NH3) emission of CS added treatments decreased by 6.39%-24.68%, 10.60%-23.23% and 13.00%-19.58%, respectively. But the CS amendment increased CO2 emission by 15.53%-30.81%. The mineralization of carbon and nitrogen was mainly correlated to Firmicutes, Actinobacteria, Proteobacteria and Bacteroidota, CS amendment increased abundance by 22.28%, 17.79%, 1.48% and 35.90%, respectively. The strategy of employing CS would be the most feasible approach for recycling of immature manure, considering its compost quality and environmental from farm.

Microbial communities and their enzymes facilitate degradation of recalcitrant polymers in anaerobic digestion

Microbial consortia efficiently degrade complex biopolymers found in the organic fraction of municipal solid waste (OFMSW). Through enzyme production and division of labor during anaerobic digestion, microbial communities break down recalcitrant polymers and make fermentation products, including methane. However, microbial communities remain underutilized for waste degradation as it remains difficult to characterize and predict microbial interactions during waste breakdown, especially as cultivation conditions change drastically throughout anaerobic digestion. This review discusses recent progress and opportunities in cultivating natural and engineered consortia for OFMSW hydrolysis, including how recalcitrant substrates are degraded by enzymes as well as the critical factors that govern microbial interactions and culture stability. Methods to measure substrate degradation are also reviewed, and we demonstrate the need for increased standardization to enable comparisons across different environments.

Ecotoxicological risk assessment of wastewater irrigation on soil microorganisms: Fate and impact of wastewater-borne micropollutants in lettuce-soil system

The implementation of the new Water Reuse regulation in the European Union brings to the forefront the need to evaluate the risks of using wastewater for crop irrigation. Here, a two-tier ecotoxicological risk assessment was performed to evaluate the fate of wastewater-borne micropollutants in soil and their ecotoxicological impact on plants and soil microorganisms. To this end, two successive cultivation campaigns of lettuces were irrigated with wastewater (at agronomical dose (not spiked) and spiked with a mixture of 14 pharmaceuticals at 10 and 100 µg/L each) in a controlled greenhouse experiment. Over the two cultivation campaigns, an accumulation of PPCPs was observed in soil microcosms irrigated with wastewater spiked with 100 μg/L of PPCPs with the highest concentrations detected for clarithromycin, hydrochlorothiazide, citalopram, climbazole and carbamazepine. The abundance of bacterial and fungal communities remained stable over the two cultivation campaigns and was not affected by any of the irrigation regimes applied. Similarly, no changes were observed in the abundance of ammonium oxidizing archaea (AOA) and bacteria (AOB), nor in clade A of commamox no matter the cultivation campaign or the irrigation regime considered. Only a slight increase was detected in clade B of commamox bacteria after the second cultivation campaign. Sulfamethoxazole-resistant and -degrading bacteria were not impacted either. The irrigation regimes had only a limited effect on the bacterial evenness. However, in response to wastewater irrigation the structure of soil bacterial community significantly changed the relative abundance of Acidobacteria, Chloroflexi, Verrucomicrobia, Beta-, Gamma- and Deltaprotebacteria. Twenty-eight operational taxonomic units (OTUs) were identified as responsible for the changes observed within the bacterial communities of soils irrigated with wastewater or with water. Interestingly, the relative abundance of these OTUs was similar in soils irrigated with either spiked or non-spiked irrigation solutions. This indicates that under both agronomical and worst-case scenario the mixture of fourteen PPCPs had no effect on soil bacterial community.

Phytoplankton biodiversity is more important for ecosystem functioning in highly variable thermal environments

The 21st century has seen an acceleration of anthropogenic climate change and biodiversity loss, with both stressors deemed to affect ecosystem functioning. However, we know little about the interactive effects of both stressors and in particular about the interaction of increased climatic variability and biodiversity loss on ecosystem functioning. This should be remedied because larger climatic variability is one of the main features of climate change. Here, we demonstrated that temperature fluctuations led to changes in the importance of biodiversity for ecosystem functioning. We used microcosm communities of different phytoplankton species richness and exposed them to a constant, mild, and severe temperature-fluctuating environment. Wider temperature fluctuations led to steeper biodiversity-ecosystem functioning slopes, meaning that species loss had a stronger negative effect on ecosystem functioning in more fluctuating environments. For severe temperature fluctuations, the slope increased through time due to a decrease of the productivity of species-poor communities over time. We developed a theoretical competition model to better understand our experimental results and showed that larger differences in thermal tolerances across species led to steeper biodiversity-ecosystem functioning slopes. Species-rich communities maintained their ecosystem functioning with increased fluctuation as they contained species able to resist the thermally fluctuating environments, while this was on average not the case in species-poor communities. Our results highlight the importance of biodiversity for maintaining ecosystem functions and services in the context of increased climatic variability under climate change.

Systematic variation in the temperature dependence of bacterial carbon use efficiency

Carbon use efficiency (CUE) is a key characteristic of microbial physiology and underlies community-level responses to changing environments. Yet, we currently lack general empirical insights into variation in microbial CUE at the level of individual taxa. Here, through experiments with 29 strains of environmentally isolated bacteria, we find that bacterial CUE typically responds either positively to temperature, or has no discernible response, within biologically meaningful temperature ranges. Using a global data synthesis, we show that these results are generalisable across most culturable groups of bacteria. This variation in the thermal responses of bacterial CUE is taxonomically structured, and stems from the fact that relative to respiration rates, bacterial population growth rates typically respond more strongly to temperature, and are also subject to weaker evolutionary constraints. Our results provide new insights into microbial physiology, and a basis for more accurately modelling the effects of thermal fluctuations on complex microbial communities.

The Impact of Fertilizer Amendments on Soil Autotrophic Bacteria and Carbon Emissions in Maize Field on the Semiarid Loess Plateau

Soil autotrophic bacteria play a crucial role in regulating CO₂ fixation and crop productivity. However, the information is limited to how fertilization amendments alter soil autotrophic bacterial community, crop yield, and carbon emission efficiency (CEE). Here, we estimated the impact of the structure and co-occurrence network of soil autotrophic bacterial community on maize yield and CEE. A long-term field experiment was conducted with five fertilization treatments in semiarid Loess Plateau, including no amendment (NA), chemical fertilizer (CF), chemical fertilizer plus commercial organic fertilizer (SC), commercial organic fertilizer (SM), and maize straw (MS). The results showed that fertilization amendments impacted the structure and network of soil Calvin-Benson-Bassham (CBB) (cbbL) gene-carrying bacterial community via changing soil pH and NO₃-N. Compared with no amendment, the cbbL-carrying bacterial diversity was increased under the SC, SM, and MS treatments but decreased under the CF treatment. Soil autotrophic bacterial network contained distinct microbial modules that consisted of closely associated microbial species. We detected the higher abundances of soil cbbL-carrying bacterial genus Xanthobacter, Bradyrhizobium, and Nitrosospira. Structural equation modeling further suggested that the diversity, composition, and network of autotrophic bacterial community had strongly positive relationships with CEE and maize yield. Taken together, our results suggest that soil autotrophic bacterial community may drive crop productivity and CEE, and mitigate the atmospheric greenhouse effect.

Manganese dioxide driven the carbon and nitrogen transformation by activating the complementary effects of core bacteria in composting

This study revealed core bacterial metabolic mechanisms involved in carbon (C) and nitrogen (N) in composting with adding MnO₂. Two tests (control group (CK), adding MnO₂ (M)) were performed. The results indicated that the MnO₂ accelerated the transformation of carbon and nitrogen in composting. Core bacteria involved in the C and N conversion were identified, the complementarity effects of core bacteria were stimulated in M composting. Additionally, the influence of core bacteria on the C and N conversion could be divided into two pathways in M composting. One was that core bacteria promoted C and N conversion by accelerating the flow of amino acids into the tricarboxylic acid cycle. Another was that the complementarity effects of core bacteria increased the overall bacterial diversity, which contributed to C and N conversion. These findings showed that the addition of MnO₂ to composting was a promising application to treat agricultural organic waste.

Plant and soil biodiversity have non-substitutable stabilising effects on biomass production

The stability of plant biomass production in the face of environmental change is fundamental for maintaining terrestrial ecosystem functioning, as plant biomass is the ultimate source of energy for nearly all life forms. However, most studies have focused on the stabilising effect of plant diversity, neglecting the effect of soil biodiversity, the largest reservoir of biodiversity on Earth. Here we investigated the effects of plant and soil biodiversity on the temporal stability of biomass production under varying simulated precipitation in grassland microcosms. Soil biodiversity loss reduced temporal stability by suppressing asynchronous responses of plant functional groups. Greater plant diversity, especially in terms of functional diversity, promoted temporal stability, but this effect was independent of soil biodiversity loss. Moreover, multitrophic biodiversity, plant and soil biodiversity combined, was positively associated with temporal stability. Our study highlights the importance of maintaining both plant and soil biodiversity for sustainable biomass production.

Microbial diversity and activity assessment in a 100-year-old lead mine

Mining activities frequently leave a legacy of residues that remain in the area for long periods causing the pollution of surroundings. We studied on a 100 year-old mine, the behavior of potentially toxic elements (PTEs) and their ecotoxicological impact on activity and diversity of microorganisms. The PTEs contamination assessment allowed the classification of the materials as highly (reference- and contaminated-samples) and very highly polluted (illegal spill of olive mill wastes (OMW), tailings, and dumps). OMW presented the lowest enzymatic activities while tailings and dumps had low dehydrogenase and arylsulfatase activities. All the α-diversity indices studied were negatively impacted in dumps. Tailings had lower Chao1 and PD whole tree values as compared to those of reference-samples. β-diversity analysis showed similar bacterial community composition for reference- and contaminated-samples, significantly differing from that of tailings and dumps. The relative abundance of Gemmatimonadetes, Bacteroidetes, and Verrucomicrobia was lower in OMW, tailings, and dumps as compared to reference-samples. Fifty-seven operational taxonomic units were selected as responsible for the changes observed between samples. This study highlights that assessing the relationship between physicochemical properties and microbial diversity and activity gives clues about ongoing regulating processes that can be helpful for stakeholders to define an appropriate management strategy.

A holistic framework integrating plant-microbe-mineral regulation of soil bioavailable nitrogen

Soil organic nitrogen (N) is a critical resource for plants and microbes, but the processes that govern its cycle are not well-described. To promote a holistic understanding of soil N dynamics, we need an integrated model that links soil organic matter (SOM) cycling to bioavailable N in both unmanaged and managed landscapes, including agroecosystems. We present a framework that unifies recent conceptual advances in our understanding of three critical steps in bioavailable N cycling: organic N (ON) depolymerization and solubilization; bioavailable N sorption and desorption on mineral surfaces; and microbial ON turnover including assimilation, mineralization, and the recycling of microbial products. Consideration of the balance between these processes provides insight into the sources, sinks, and flux rates of bioavailable N. By accounting for interactions among the biological, physical, and chemical controls over ON and its availability to plants and microbes, our conceptual model unifies complex mechanisms of ON transformation in a concrete conceptual framework that is amenable to experimental testing and translates into ideas for new management practices. This framework will allow researchers and practitioners to use common measurements of particulate organic matter (POM) and mineral-associated organic matter (MAOM) to design strategic organic N-cycle interventions that optimize ecosystem productivity and minimize environmental N loss.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10533-021-00793-9.

Soil biodiversity enhances the persistence of legumes under climate change

Global environmental change poses threats to plant and soil biodiversity. Yet, whether soil biodiversity loss can further influence plant community's response to global change is still poorly understood. We created a gradient of soil biodiversity using the dilution-to-extinction approach, and investigated the effects of soil biodiversity loss on plant communities during and following manipulations simulating global change disturbances in experimental grassland microcosms. Grass and herb biomass was decreased by drought and promoted by nitrogen deposition, and a fast recovery was observed following disturbances, independently of soil biodiversity loss. Warming promoted herb biomass during and following disturbance only when soil biodiversity was not reduced. However, legumes biomass was suppressed by these disturbances, and there were more detrimental effects with reduced soil biodiversity. Moreover, soil biodiversity loss suppressed the recovery of legumes following these disturbances. Similar patterns were found for the response of plant diversity. The changes in legumes might be partly attributed to the loss of mycorrhizal soil mutualists. Our study shows that soil biodiversity is crucial for legume persistence and plant diversity maintenance when faced with environmental change, highlighting the importance of soil biodiversity as a potential buffering mechanism for plant diversity and community composition in grasslands.

Pavement Overrides the Effects of Tree Species on Soil Bacterial Communities

Human disturbance and vegetation are known to affect soil microorganisms. However, the interacting effects of pavement and plant species on soil bacterial communities have received far less attention. In this study, we collected soil samples from pine (Pinus tabuliformis Carr.), ash (Fraxinus chinensis), and maple (Acer truncatum Bunge) stands that grew in impervious, pervious, and no pavement blocks to investigate the way pavement, tree species, and their interaction influence soil bacterial communities by modifying soil physicochemical properties. Soil bacterial community composition and diversity were evaluated by bacterial 16S amplicon sequencing. The results demonstrated that soil bacterial community composition and diversity did differ significantly across pavements, but not with tree species. The difference in soil bacterial community composition across pavements was greater in pine stands than ash and maple stands. Soil bacterial diversity and richness indices decreased beneath impervious pavement in pine stands, and only bacterial richness indices decreased markedly in ash stands, but neither showed a significant difference across pavements in maple stands. In addition, bacterial diversity did not differ dramatically between pervious pavement and no pavement soil. Taken together, these results suggest that pavement overwhelmed the effects of tree species on soil bacterial communities, and had a greater effect on soil bacterial communities in pine stands, followed by ash and maple stands. This study highlights the importance of anthropogenic disturbance, such as pavement, which affects soil microbial communities.

Evaluation of Microbe-Driven Soil Organic Matter Quantity and Quality by Thermodynamic Theory

Microbial communities, coupled with substrate quality and availability, regulate the stock (formation versus mineralization) of soil organic matter (SOM) in terrestrial ecosystems. However, our understanding of how soil microbes interact with contrasting substrates influencing SOM quantity and quality is still very superficial. Here, we used thermodynamic theory principles and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) to evaluate the linkages between dissolved organic matter (DOM [organic substrates in soil that are readily available]), thermodynamic quality, and microbial communities. We investigated soils from subtropical paddy ecosystems across a 1,000-km gradient and comprising contrasting levels of SOM content and nutrient availability. Our region-scale study suggested that soils with a larger abundance of readily accessible resources (i.e., lower Gibbs free energy) supported higher levels of microbial diversity and higher SOM content. We further advocated a novel phylotype-level microbial classification based on their associations with OM quantities and qualities and identified two contrasting clusters of bacterial taxa: phylotypes that are highly positively correlated with thermodynamically favorable DOM and larger SOM content versus those which are associated with less-favorable DOM and lower SOM content. Both groups are expected to play critical roles in regulating SOM contents in the soil. By identifying the associations between microbial phylotypes of different life strategies and OM qualities and quantities, our study indicates that thermodynamic theory can act as a proxy for the relationship between OM and soil microbial communities and should be considered in models of soil organic matter preservation.IMPORTANCE Microbial communities are known to be important drivers of organic matter (OM) accumulation in terrestrial ecosystems. However, despite the importance of these soil microbes and processes, the mechanisms behind these microbial-SOM associations remain poorly understood. Here, we used the principles of thermodynamic theory and novel Fourier transform ion cyclotron resonance mass spectrometry techniques to investigate the links between microbial communities and dissolved OM (DOM) thermodynamic quality in soils across a 1,000-km gradient and comprising contrasting nutrient and C contents. Our region-scale study provided evidence that soils with a larger amount of readily accessible resources (i.e., lower Gibbs free energy) supported higher levels of microbial diversity and larger SOM content. Moreover, we created a novel phylotype-level microbial classification based on the associations between microbial taxa and DOM quantities and qualities. We found two contrasting clusters of bacterial taxa based on their level of association with thermodynamically favorable DOM and SOM content. Our study advances our knowledge on the important links between microbial communities and SOM. Moreover, by identifying the associations between microbial phylotypes of different life strategies and OM qualities and quantities, our study indicates that thermodynamic theory can act as a proxy for the relationship between OM and soil microbial communities. Together, our findings support that the association between microbial species taxa and substrate thermodynamic quality constituted an important complement explanation for soil organic matter preservation.

Species richness promotes ecosystem carbon storage: evidence from biodiversity-ecosystem functioning experiments

Plant diversity has a strong impact on a plethora of ecosystem functions and services, especially ecosystem carbon (C) storage. However, the potential context-dependency of biodiversity effects across ecosystem types, environmental conditions and carbon pools remains largely unknown. In this study, we performed a meta-analysis by collecting data from 95 biodiversity-ecosystem functioning (BEF) studies across 60 sites to explore the effects of plant diversity on different C pools, including aboveground and belowground plant biomass, soil microbial biomass C and soil C content across different ecosystem types. The results showed that ecosystem C storage was significantly enhanced by plant diversity, with stronger effects on aboveground biomass than on soil C content. Moreover, the response magnitudes of ecosystem C storage increased with the level of species richness and experimental duration across all ecosystems. The effects of plant diversity were more pronounced in grasslands than in forests. Furthermore, the effects of plant diversity on belowground plant biomass increased with aridity index in grasslands and forests, suggesting that climate change might modulate biodiversity effects, which are stronger under wetter conditions but weaker under more arid conditions. Taken together, these results provide novel insights into the important role of plant diversity in ecosystem C storage across critical C pools, ecosystem types and environmental contexts.