The influence of soil age on ecosystem structure and function across biomes

Advancing the comprehensive understanding of soil organic carbon priming effect: definitions, mechanisms, influencing factors, and future perspectives

The soil carbon (C) priming effect (PE), an important phenomenon in soil C cycle research, has garnered extensive attention in recent years. Soil C PE refers to the stimulation or inhibition of the original soil organic C (SOC) decomposition rate by newly added organic matter in the soil. Its mechanism of action involves the activity of soil microorganisms. Fresh organic matter input provides an additional source of energy and nutrients for soil microorganisms, prompting changes in microbial community structure and activity, which in turn affects SOC decomposition. Easily decomposable organic matter may stimulate rapid microbial growth and metabolic activity of microorganisms, thereby the decomposition accelerating of original SOC and producing a positive PE, whereas recalcitrant organic matter may lead microorganisms to preferentially utilise the newly added C source, thereby inhibiting original SOC decomposition and producing a negative PE. There are numerous factors influencing soil C PE, including organic matter properties such as chemical composition, C:N ratio, and lignin content; soil environmental factors such as temperature, humidity, and pH value; and land-use patterns and vegetation types. Research on soil C PE is crucial for an in-depth understanding of the soil C cycle, the accurate assessment of dynamic changes in the soil C pool, and the development of sustainable soil management strategies. This study introduces the definition, change mechanism, influencing factors, and research methods of soil C PE and elaborates on the status and deficiencies of PE research, which is helpful for predicting soil C responses to global climate change and provides a scientific basis for improving soil fertility and reducing greenhouse gas emissions.

Postglacial bioweathering, soil nutrient cycling, and podzolization from palaeometagenomics of plants, fungi, and bacteria

Warming-induced glacier retreat exposes bare rocks and glacial sediments, facilitating the establishment of soils. The dynamic interplay between climate, vegetation cover, and soil formation is poorly understood as time-series data are lacking. Here, we present postglacial soil formation during the past 23,000 years inferred from ancient DNA shotgun analyses of Lake Lama sediments targeting plants, soil-associated fungi, and bacteria showing postmortem damage signatures that verify their ancient origin. In the Late Glacial, we reveal basaltic weathering with high abundances of lichens, carbon, and arsenic cyclers, shifting to mycorrhizae domination and N cycling in the Holocene. We reconstruct podzolization starting with spruce forest migration in the Holocene, resulting in soil acidification and increased iron cycling. Our reconstruction of soil formation also contributes basic knowledge for the design of carbon-capture strategies using basalt weathering.

An Optimized Aerogel-Based Apheresis Device for Targeted Lipid Clearance in Elderly Hyperlipidemia Patients

Elderly patients with hyperlipidemia often exhibit resistance to conventional hypolipidemic treatments, underscoring the need for more effective strategies to address lipid imbalances in this high-risk group. This study introduces LipClean, an aerogel-based apheresis device specifically designed to remove harmful plasma lipids. LipClean is constructed using hydrophilic cellulose fibers, which serve as a supramolecular platform for synthesizing hydrophobic conjugated polymers through a Sonogashira-Hagihara reaction. These conjugated polymers are then cross-linked with the cellulose fibers via phosphorylation, generating an aerogel monolith with an interpenetrating network of hydrophilic fibers and hydrophobic polymers. Unlike bilayer aerogels that separate hydrophilic and hydrophobic layers, LipClean's interpenetrating structure is precisely engineered through polymer design and gradient cross-linking. This optimization enhances both bodily fluid flow and lipid adsorption while minimizing the removal of essential plasma components and ensuring unobstructed cell passage. In preclinical testing, LipClean significantly reduced triglyceride and cholesterol levels in an elderly rat model of hyperlipidemia and normalized lipid levels in blood samples from hypertensive patients. Importantly, purified blood maintained normal levels of blood cells and physiological and biochemical indicators after apheresis, highlighting LipClean's potential for managing hyperlipidemia-related disorders. This study, therefore, underscores the importance of interdisciplinary collaboration in driving medical device innovation.

Time and climate roles in driving soil carbon distribution and stability in particulate and mineral-associated organic matter pools

Understanding the accumulation and stability of soil organic matter (SOM) pools as a function of time (i.e., soil age) and climate (i.e., precipitation and temperature) represents a crucial challenge. This study aims at investigating the effect of both climate and time on SOM distribution into particulate and mineral-associated organic matter (POM and MAOM, respectively), using two chronosequences located along a climate gradient. The contribution of POM and MAOM to soil organic carbon (SOC) storage differs between the climo-chronosequences and with depth. The ratio between MAOM and POM pools (MAOM/POM) ranges from 0.9 to 2.0 and from 1.4 to 3.5 in the wetter and cooler and in the drier and warmer chronosequence, respectively. Regardless of the chronosequence, the MAOM/POM ratio increases with depth, highlighting a more important role of the mineral-associated fraction in carbon storage in deeper soils. The concentration of organic carbon in mineral-associated (MAOC) and particulate (POC) pools along the soil profile in the wetter and cooler chronosequence is 2× and 3× higher, respectively, than in soils from the drier and warmer one. In particular, in the wetter and cooler chronosequence, MAOC and POC concentrations decrease with soil age. In the drier and warmer chronosequence, only POC concentration decreases with soil age, whereas MAOC concentration generally increases. The thermal stability of the MAOM fraction increases with soil age and depth only in the drier and warmer climatic conditions, whereas no differences with depth occur in the wetter and cooler chronosequence. Furthermore, the MAOM energy density decreases with soil depth and age in both chronosequences. Independently of the chronosequence, POM represents the most labile pool with higher energy density. In conclusion, time and climate play a different role in SOC distribution between the pools and on their relative stability. Soil age drives MAOM stability in drier and warmer conditions, whereas a wetter and cooler climate determines a higher SOC accumulation in both pools, although these greater carbon stocks are negatively correlated with their stability.

Practical applications of soil microbiota to improve ecosystem restoration: current knowledge and future directions

Soil microbiota are important components of healthy ecosystems. Greater consideration of soil microbiota in the restoration of biodiverse, functional, and resilient ecosystems is required to address the twin global crises of biodiversity decline and climate change. In this review, we discuss available and emerging practical applications of soil microbiota into (i) restoration planning, (ii) direct interventions for shaping soil biodiversity, and (iii) strategies for monitoring and predicting restoration trajectories. We show how better planning of restoration activities to account for soil microbiota can help improve progress towards restoration targets. We show how planning to embed soil microbiota experiments into restoration projects will permit a more rigorous assessment of the effectiveness of different restoration methods, especially when complemented by statistical modelling approaches that capitalise on existing data sets to improve causal understandings and prioritise research strategies where appropriate. In addition to recovering belowground microbiota, restoration strategies that include soil microbiota can improve the resilience of whole ecosystems. Fundamentally, restoration planning should identify appropriate reference target ecosystem attributes and - from the perspective of soil microbiota - comprehensibly consider potential physical, chemical and biological influences on recovery. We identify that inoculating ecologically appropriate soil microbiota into degraded environments can support a range of restoration interventions (e.g. targeted, broad-spectrum and cultured inoculations) with promising results. Such inoculations however are currently underutilised and knowledge gaps persist surrounding successful establishment in light of community dynamics, including priority effects and community coalescence. We show how the ecological trajectories of restoration sites can be assessed by characterising microbial diversity, composition, and functions in the soil. Ultimately, we highlight practical ways to apply the soil microbiota toolbox across the planning, intervention, and monitoring stages of ecosystem restoration and address persistent open questions at each stage. With continued collaborations between researchers and practitioners to address knowledge gaps, these approaches can improve current restoration practices and ecological outcomes.

Amino acid-sulphur decomposition in agricultural soil profile along a long-term recultivation chronosequence

The significance of sulphur (S) availability for crop yield and quality is highlighted under the global S deficiency scenario. However, little is known about the temporal trend in belowground organic S mineralisation when restoring land to productive agricultural systems, particularly for the deeper soil parts. Therefore, we investigated the decomposition of 35S-labelled methionine in surface (0-30 cm) and subsurface soil (30-60 cm and 60-90 cm) over a 48-year recultivation chronosequence (sampled after1, 8, 14, 24 and 48 years). Soil total sulphur (TS) significantly (p < 0.05) increased in surface soil but not in subsurface soils after 48 years of recultivation. Overall, the immobilisation of 35S-methionine (35S-MB) in subsurface soils relative to year 1 significantly decreased over the chronosequence but did not change in the surface samples. The 35S-MB values in subsurface soils were positively corrected with soil carbon (C) stoichiometry (Pearson correlation, p < 0.05), suggesting the immobilisation of methionine was likely constrained by microbial C demand in deep soil. Compared to year 1, 35S-SO42- released from 35S-methionine significantly declined throughout the older (≥ 8 years) soil profiles. Significant (p < 0.05) changes in the organic 35S partition (35S immobilisation and 35S released as sulphate) were observed in year 8 after the soil was recultivated with N-fixing alfalfa or fertilisers. Whereas, after that (≥ 14 years), soil organic S partition remained affected when conventional tillage and agricultural crops dominated this site. Indicating that the effect of recultivation on organic S decomposition depends on the manner of recultivation management. Our study contributes to an improved understanding of amino acid S and organic S mineralisation under severe anthropogenic disturbance.

Response of bacterial ecological and functional properties to anthropogenic interventions during maturation of mine sand soil

Soil formation is a complex process that starts from the biological development. The ecological principles and biological function in soil are of great importance, whereas their response to anthropogenic intervention has been poorly understood. In this study, a 150-day microcosmic experiment was conducted with the addition of sludge and/or fermented wood chips (FWC) to promote the soil maturation. The results showed that, compared to the control (natural development without anthropogenic intervention), sludge, FWC, and their combination increased the availability of carbon, nitrogen, and potassium, and promoted the soil aggregation. They also enhanced the cellulase activity, microbial biomass carbon (MBC) and bacterial diversity, indicating that anthropogenic interventions promoted the maturation of sand soil. Molecular ecology network and functional analyses indicated that soil maturation was accomplished with the enhancement of ecosystem functionality and stability. Specifically, sludge promoted a transition in bacterial community function from denitrification to nitrification, facilitated the degradation of easily degradable organic matter, and enhanced the autotrophic nutritional mode. FWC facilitated the transition of bacterial function from denitrification to ammonification, promoted the degradation of recalcitrant organic matter, and simultaneously enhanced both autotrophic and heterotrophic nutritional modes. Although both sludge and FWC promoted the soil functionality, they showed distinct mechanistic actions, with sludge enhancing the physical structure, and FWC altering chemical composition. It is also worth emphasizing that sludge and FWC exhibited a synergistic effect in promoting biological development and ecosystem stability, thereby providing an effective avenue for soil maturation.

Soil organic matter dynamics and stability: Climate vs. time

Climate and time are among the most important factors driving soil organic carbon (SOC) stability and accrual in mineral soils; however, their relative importance on SOC dynamics is still unclear. Therefore, understanding how these factors covary over a range of soil developmental stages is crucial to improve our knowledge of climate change impact on SOC accumulation and persistence. Two chronosequences located along a climate gradient were investigated to determine the main interactions among time (age) and climate (precipitation and temperature) on SOC stability and stock with depth. Considering a common depth (0-15 or 0-30 cm), in the drier chronosequence, the older soil showed the highest SOC stock, while the younger exhibited the lowest carbon accumulation. Considering the whole profile, the SOC stock increased with age. In the wetter chronosequence, the younger soil showed the highest SOC stock considering a common depth, whereas, when the entire profile is taken into account, the older one accumulated 2-3 times more SOC than the others. In both chronosequences, significant stocks of SOC (∼42 %) were accumulated below 30 cm. Soil organic matter stability, assessed by thermal analysis and heterotrophic respiration, increases with depth and age only in the drier chronosequence. Soils from the wetter chronosequence were instead characterized by a greater quantity of labile and/or not-stabilized SOC; here, the amorphous Fe/Al-rich secondary mineral weathering products showed an essential predictor function of SOC storage, although they do not seem to be involved in SOC stabilization mechanisms. Otherwise, the interaction of SOC with fine particles, short-range order minerals, and organo-metal complexes represent the significant stabilization mechanisms in soils from drier climate. The results highlighted how the age factor plays an unassuming role in geochemical processes influencing SOC dynamics; however, climate determines different trajectories of soil development and SOC dynamics for a given soil age. Thus, soil age shows a key role in SOC stabilization especially in drier climatic conditions, while wetter conditions determine an accumulation of a higher yet more labile amount of SOC.

Geologically younger ecosystems are more dependent on soil biodiversity for supporting function

Soil biodiversity contains the metabolic toolbox supporting organic matter decomposition and nutrient cycling in the soil. However, as soil develops over millions of years, the buildup of plant cover, soil carbon and microbial biomass may relax the dependence of soil functions on soil biodiversity. To test this hypothesis, we evaluate the within-site soil biodiversity and function relationships across 87 globally distributed ecosystems ranging in soil age from centuries to millennia. We found that within-site soil biodiversity and function relationship is negatively correlated with soil age, suggesting a stronger dependence of ecosystem functioning on soil biodiversity in geologically younger than older ecosystems. We further show that increases in plant cover, soil carbon and microbial biomass as ecosystems develop, particularly in wetter conditions, lessen the critical need of soil biodiversity to sustain function. Our work highlights the importance of soil biodiversity for supporting function in drier and geologically younger ecosystems with low microbial biomass.

Role of genes encoding microbial carbohydrate-active enzymes in the accumulation and dynamics of organic carbon in subtropical forest soils

Microbial anabolism and catabolism regulate the accumulation and dynamics of soil organic carbon (SOC). However, very little attention has been paid to the role of microbial functional traits in the accumulation and dynamics of SOC in forest soils. In this study, nine forest soils were selected at three altitudes (600 m, 1200 m, and 1500 m) and three soil depths (0-15 cm, 15-30 cm, and 30-45 cm) located in Jiugong Mountain. Vertical traits of functional genes encoding microbial carbohydrate-active enzymes (CAZymes) were observed using metagenomic sequencing. Soil amino sugars were used as biomarkers to indicate microbial residue carbon (MRC). The results showed that GH1 (β-glucosidase: 147.49 TPM) and GH3 (β-glucosidase: 109.09 TPM) were the dominant genes for plant residue decomposition, and their abundance increased with soil depth and peaked in the deep soil at 600 m (GH1: 147.89 TPM; GH3: 109.59 TPM). The highest abundance of CAZymes for fungal and bacterial residue decomposition were GH18 (chitinase: 30.81 TPM) and GH23 (lysozyme: 58.02 TPM), respectively. The abundance of GH18 increased with soil depth, while GH23 showed the opposite trend. Moreover, MRC accumulation was significantly positively correlated with CAZymes involved in the degradation of hemicellulose (r = 0.577, p = 0.002). Compared with the soil before incubation, MRC in the topsoil at the low and middle altitudes after incubation increased by 4 % and 8 %, respectively, while MRC in the soils at 1500 m tended to decrease (p > 0.05). The mineralization capacity of SOC at 1500 m was significantly higher than that at 1200 m and 600 m (p < 0.05). Our results suggested that microbial function for degrading plant residue components, especially hemicellulose and lignin, contributed greatly to SOC accumulation and dynamics. These results were vital for understanding the roles of microbial functional traits in C cycling in forest.

Pedogenesis of typical zonal soil drives belowground bacterial communities of arable land in the Northeast China Plain

Belowground bacterial communities play essential roles in maintaining ecosystem multifunction, while our understanding of how and why their distribution patterns and community compositions may change with the distinct pedogenetic conditions of different soil types is still limited. Here, we evaluated the roles of soil physiochemical properties and biotic interactions in driving belowground bacterial community composition across three typical zonal soil types, including black calcium soil (QS), typical black soil (HL) and dark brown soil (BQL), with distinct pedogenesis on the Northeast China Plain. Changes in soil bacterial diversity and community composition in these three zonal soil types were strongly correlated with soil pedogenetic features. SOC concentrations in HL were higher than in QS and BQL, but bacterial diversity was low, and the network structure revealed greater stability and connectivity. The composition of the bacterial community correlated significantly with soil pH in QS but with soil texture in BQL. The bacterial co-occurrence network of HL had higher density and clustering coefficients but lower edges, and different keystone species of networks were also detected. This work provides a basic understanding of the driving mechanisms responsible for belowground bacterial biodiversity and distribution patterns over different pedogenetic conditions in agroecosystems.

Nematodes and their bacterial prey improve phosphorus acquisition by wheat

Plant growth is greatly influenced by the rhizosphere microbiome, which has been traditionally investigated from a bottom-up perspective assessing how resources such as root exudates stimulate microbial growth and drive microbiome assembly. However, the importance of predation as top-down force on the soil microbiome remains largely underestimated. Here, we planted wheat both in natural and in sterilized soils inoculated with the key microbiome predators - bacterivorous nematodes - to assess how plant performance responds to top-down predation of the soil microbiome and specific plant growth-promoting bacteria, namely phosphate-solubilizing bacteria. We found that nematodes enriched certain groups (e.g. Actinobacteria, Chloroflexi, and Firmicutes) and strengthened microbial connectance (e.g. Actinobacteria and Proteobacteria). These changes in microbiome structure were associated with phosphate-solubilizing bacteria that facilitated phosphorus (P) cycling, leading to greater P uptake and biomass of wheat in both soils. However, the enhancement varied between nematode species, which may be attributed to the divergence of feeding behavior, as nematodes with weaker grazing intensity supported greater abundance of phosphate-solubilizing bacteria and better plant performance compared with nematodes with greater grazing intensity. These results confirmed the ecological importance of soil nematodes for ecosystem functions via microbial co-occurrence networks and suggested that the predation strength of nematodes determines the soil bacteria contribution to P biogeochemical cycling and plant growth.

Soil type determines the magnitude of soil fertility changes by forest-to-pasture conversion in Western Amazonia

The deforestation of tropical forests raises environmental concerns worldwide. Removing the pristine forest impacts the soil, consequently affecting the environmental services it provides. Within this context, the main goal of this study was to determine how the conversion of the tropical rainforest to pasture affects soil fertility across an extended range of soil heterogeneity, including different soil types. We sampled 13 sites, among forests, recent pastures (≤7-year-old), and old pastures (≥10-year-old), on Acrisols, Ferralsols, Plinthosols, and Luvisols, across a ± 800 km geographical range in the Western Brazilian Amazon. Soils were classified taxonomically, and their superficial layer's chemical and physical properties (0-10 cm) were analyzed. Furthermore, we tested the sensibility of Actinobacteria and Proteobacteria to detect changes in these soil properties based on their ecological habitat. An inter-regional gradient of soil fertility was observed, and the sampling sites were clustered mostly by soil type and associated land use than by spatial distance. The Sum of bases, Ca + Mg, base saturation, Al saturation, and pH were consistently affected by land use, increasing after conversion to pasture, at different degrees and with a more pronounced effect on oxidic soils. The Sum of bases was the only property that increased significantly among the study sites (R_adj = 0.860, p < 0.001), being able to detect the effect of anthropic land use on a larger coverage of soil types. Finally, the Actinobacteria:Proteobacteria ratio was also sensitive to the impact of forest-to-pasture conversion, with a higher ratio observed in pasture systems, and it was positively correlated with soil pH (rho = 0.469, p < 0.001). Our results consistently show that the forest-to-pasture conversion leads to strong alterations in the soil environment, with varying intensities depending on soil type.

Soil biodiversity supports the delivery of multiple ecosystem functions in urban greenspaces

While the contribution of biodiversity to supporting multiple ecosystem functions is well established in natural ecosystems, the relationship of the above- and below-ground diversity with ecosystem multifunctionality remains virtually unknown in urban greenspaces. Here we conducted a standardized survey of urban greenspaces from 56 municipalities across six continents, aiming to investigate the relationships of plant and soil biodiversity (diversity of bacteria, fungi, protists and invertebrates, and metagenomics-based functional diversity) with 18 surrogates of ecosystem functions from nine ecosystem services. We found that soil biodiversity across biomes was significantly and positively correlated with multiple dimensions of ecosystem functions, and contributed to key ecosystem services such as microbially driven carbon pools, organic matter decomposition, plant productivity, nutrient cycling, water regulation, plant-soil mutualism, plant pathogen control and antibiotic resistance regulation. Plant diversity only indirectly influenced multifunctionality in urban greenspaces via changes in soil conditions that were associated with soil biodiversity. These findings were maintained after controlling for climate, spatial context, soil properties, vegetation and management practices. This study provides solid evidence that conserving soil biodiversity in urban greenspaces is key to supporting multiple dimensions of ecosystem functioning, which is critical for the sustainability of urban ecosystems and human wellbeing.

Soils in warmer and less developed countries have less micronutrients globally

Soil micronutrients are capital for the delivery of ecosystem functioning and food provision worldwide. Yet, despite their importance, the global biogeography and ecological drivers of soil micronutrients remain virtually unknown, limiting our capacity to anticipate abrupt unexpected changes in soil micronutrients in the face of climate change. Here, we analyzed >1300 topsoil samples to examine the global distribution of six metallic micronutrients (Cu, Fe, Mn, Zn, Co and Ni) across all continents, climates and vegetation types. We found that warmer arid and tropical ecosystems, present in the least developed countries, sustain the lowest contents of multiple soil micronutrients. We further provide evidence that temperature increases may potentially result in abrupt and simultaneous reductions in the content of multiple soil micronutrients when a temperature threshold of 12-14°C is crossed, which may be occurring on 3% of the planet over the next century. Altogether, our findings provide fundamental understanding of the global distribution of soil micronutrients, with direct implications for the maintenance of ecosystem functioning, rangeland management and food production in the warmest and poorest regions of the planet.

The neglected role of micronutrients in predicting soil microbial structure

Predicting the distribution patterns of soil microbial communities requires consideration of more environmental drivers. The effects of soil micronutrients on composition of microbial communities are largely unknown despite micronutrients closely relating to soil fertility and plant communities. Here we used data from 228 agricultural fields to identify the importance of micronutrients (iron, zinc, copper and manganese) in shaping structure of soil microbial communities (bacteria, fungi and protist) along latitudinal gradient over 3400 km, across diverse edaphic conditions and climatic gradients. We found that micronutrients explained more variations in the structure of microbial communities than macronutrients in maize soils. Moreover, micronutrients, particularly iron and copper, explained a unique percentage of the variation in structure of microbial communities in maize soils even after controlling for climate, soil physicochemical properties and macronutrients, but these effects were stronger for fungi and protist than for bacteria. The ability of micronutrients to predict the structure of soil microbial communities declined greatly in paddy soils. Machine learning approach showed that the addition of micronutrients substantially increased the predictive power by 9-17% in predicting the structure of soil microbial communities with up to 69-78% accuracy. These results highlighted the considerable contributions of soil micronutrients to microbial community structure, and advocated that soil micronutrients should be considered when predicting the structure of microbial communities in a changing world.

An Artificial Oasis in a Deadly Desert: Practices and Enlightenments

Building highway and its biological protection system in a drought-affected shifting-sand desert is a great challenge. This challenge was completed by the construction of the Taklimakan Desert Highway Shelterbelt (TDHS)—the longest of its kind in the world (436 km). The TDHS can serve as a model for highway construction and desertification control using eco-friendly and cost-effective approaches in other desert regions. Notably, we proved that local saline groundwater irrigation offers potential advantages and opportunities for the growth of halophytes and sandy soil development in hyper-arid desert environments. Here, we systematically (1) summarize the project, its results, and vital technical issues of saline water irrigation; (2) address soil hydrological processes that play a crucial role in maintaining those systems; and (3) highlight useful insights for soil development, plant survival, and soil–plant–water–biota synergy mechanisms. Indeed, the TDHS project has provided a proof of concept for restoration and desert greening initiatives.

Pedogenesis shapes predator-prey relationships within soil microbiomes

Pedogenesis determines soil physicochemical properties and many biodiversity facets, including belowground microbial bacteria and fungi. At the local scale, top-down predation by microbial protists regulates the soil microbiome, while the microbiome also affects protistan communities. However, it remains unknown how pedogenesis affects protistan communities and the potential protist-microbiome predator-prey relationships. With 435 soil samples representing different stages of pedogenesis ranging in soil age from centuries to millennia, we examined the influence of pedogenesis on the main protistan groups, and the interrelationships between protistan predators and microbial prey biomass. We revealed an enrichment in the diversity of total protists across pedogenesis and increasing richness of phototrophic protists in the medium compared with the early stages of pedogenesis. The richness of predatory protists accumulated throughout pedogenesis, which was more strongly determined by microbial biomass than environmental factors. Predator-prey associations were stronger in the young and the medium soils than in the older soils, likely because prey biomass accumulated in the latter and might be no longer limit predators. Together, our work provides evidence that pedogenesis shapes predatory protists differently than their prey, leading to shifts in predator-prey relationships. This knowledge is critical to better understand how soil food webs develop across soil development which might lead to changes in ecosystem functions.

Cross-biome antibiotic resistance decays after millions of years of soil development

Soils harbor the most diverse naturally evolved antibiotic resistance genes (ARGs) on Earth, with implications for human health and ecosystem functioning. How ARGs evolve as soils develop over centuries, to millennia (i.e., pedogenesis), remains poorly understood, which introduces uncertainty in predictions of the dynamics of ARGs under changing environmental conditions. Here we investigated changes in the soil resistome by analyzing 16 globally distributed soil chronosequences, from centuries to millennia, spanning a wide range of ecosystem types and substrate age ranges. We show that ARG abundance and diversity decline only after millions of years of soil development as observed in very old chronosequences. Moreover, our data show increases in soil organic carbon content and microbial biomass as soil develops that were negatively correlated with the abundance and diversity of soil ARGs. This work reveals natural dynamics of soil ARGs during pedogenesis and suggests that such ecological patterns are predictable, which together advances our understanding of the environmental drivers of ARGs in terrestrial environments.

A Pantropical Overview of Soils across Tropical Dry Forest Ecoregions

Pantropical variation in soils of the tropical dry forest (TDF) biome is enormously high but has been poorly characterized. To quantify variation in the global distribution of TDF soil physical and chemical properties in relation to climate and geology, we produced a synthesis using 7500 points of data with gridded fields representing lithologic, edaphic, and climatic characteristics. Our analyses reveal that 75 TDF ecoregions across five biogeographic domains (Afrotropical, Australasian, Indo-Malayan, Neotropical, and Oceanian) varied strongly with respect to parent material: sediment (57%), metamorphic (22%), volcanic (13%), and plutonic (7%). TDF ecoregions support remarkably high variability in soil suborders (32), with the Neotropical and Oceanian realms being especially diverse. As a whole, TDF soils trend strongly toward low fertility with strong variation across biogeographic domains. Similarly, the exhibited soil properties marked heterogeneity across biogeographic domains, with soil depth varying by an order of magnitude and total organic C, N, and P pools varying threefold. Organic C and N pool sizes were negatively correlated with mean annual temperature (MAT) and positively correlated with mean annual precipitation (MAP). By contrast, the distribution of soil P pools was positively influenced by both MAT and MAP and likely by soil geochemistry, due to high variations in soil parent material across the biogeographic domains. The results summarized here raise important questions as to how climate and parent material control soil biogeochemical processes in TDFs.

Phylotype diversity within soil fungal functional groups drives ecosystem stability

Soil fungi are fundamental to plant productivity, yet their influence on the temporal stability of global terrestrial ecosystems, and their capacity to buffer plant productivity against extreme drought events, remain uncertain. Here we combined three independent global field surveys of soil fungi with a satellite-derived temporal assessment of plant productivity, and report that phylotype richness within particular fungal functional groups drives the stability of terrestrial ecosystems. The richness of fungal decomposers was consistently and positively associated with ecosystem stability worldwide, while the opposite pattern was found for the richness of fungal plant pathogens, particularly in grasslands. We further demonstrated that the richness of soil decomposers was consistently positively linked with higher resistance of plant productivity in response to extreme drought events, while that of fungal plant pathogens showed a general negative relationship with plant productivity resilience/resistance patterns. Together, our work provides evidence supporting the critical role of soil fungal diversity to secure stable plant production over time in global ecosystems, and to buffer against extreme climate events.

Diazotrophic activity and denitrification in two long-term chronosequences of maritime Antarctica

The main goals of this study were to identify whether key processes involved in microbial soil nitrogen transformations, such as diazotrophic activity and denitrification, the chemical properties of limiting elements in the soil, and microbial community structure, differ in the different successional stages of two long term chronosequences in maritime Antarctica. Moreover, we expect the rates of diazotrophic activity and denitrification to be stimulated by increases in air temperature and moisture. To answer these questions, we selected three stages in the succession (early, mid and late) in each of two well established chronosequences: three raised beaches in Ardley Island; and the Barton Peninsula, which includes two cosmogenically dated sites and the forefield of the Fourcade glacier. In the Ardley chronosequence, higher diazotrophic activity was found in the older successional stages, concomitant with an increase in the abundance of Cyanobacteria. In the Barton chronosequence, Cyanobacteria were only present and abundant (Microcoleus) in the early successional stage, coinciding with the highest diazotrophic activity. Denitrification in the Barton chronosequence tended to be highest at the mid successional sites, associated with the highest abundance of Rhodanobacter. In the Ardley chronosequence, the lowest abundance of Rhodanobacter was linked to lower denitrification rates in the mid successional stage. In the Ardley chronosequence, significant positive effects of passive warming and water addition on diazotrophic activity were detected in the first and the second years of the study respectively. In the Barton chronosequence on the other hand, there was no response to either passive warming or water addition, probably a manifestation of the higher nutrient limitation in this site. Denitrification showed no response to either warming or water addition. Thus, the response of microbial nitrogen transformations to global change is highly dependent on the environmental setting, such as soil origin, age and climate regime.

Assessing previous land-vegetation productivity relationships on mountainous areas hosting coming Winter Olympics Games in 2022

In order to prevent land degradation in areas before hosting big events such as the Winter Olympic Games (WOG), developing strategic vegetation restoration plans is key. To evaluate four experimental areas with different degrees of human impacts located in the Chongli District, northern Hebei Province, China, where the coming WOG 2022 will take considering: i) the feedback mechanisms between vegetation and soil in the process of future vegetation restoration; ii) the vegetation productivity of land in different land-use types; iii) the management mode considering the sustainable development as the primary goal. To achieve these goals, we applied a minimum soil data set (MDS) to screen the most relevant indicators (soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), available phosphorus (AP), available potassium (AK), available nitrogen (AN), soil bulk density (BD), soil porosity (SP), pH, clay, silt, sand and gravel), and the nonlinear scoring method to establish a soil quality index (SQI). For this purpose, 400 soil samples (0-20 cm depth), the total biomass of one natural grassland (NG) and abandoned farmland (AF), and the growing stock of natural secondary forest (NF) and a larch plantation (LP). The results showed that the SQI can be established based on TN, silt, TP and gravel. Under LP and AF land-use type, vegetation showing a poor effect on the improvement of soil quality (SQIs were significantly lower than the NF and NG). It was also observed that above 1700 m, the growing stock of artificial vegetation exceeds the range of vegetation productivity (about 165 m³·h^-1) that the land can carry under the LP. We concluded that the main reason is the excessive depletion of N and P after human impacts. On the other hand, the SQI of NF and NG were higher, which is due to the significant improvement of soil quality by the conservation of the vegetation, so that no longer limited by the spatial distribution law, also showing higher vegetation productivity of land at different altitudes. This demonstrates that it is key to develop effective restoration plans considering the soil-vegetation relationship status of the NF and NG land-use types in this area in the territories used by the activities of the WOG 2022.

The role of soils in habitat creation, maintenance and restoration

Soils are the fundament of terrestrial ecosystems. Across the globe we find different soil types with different properties resulting from the interacting soil forming factors: parent material, climate, topography, organisms and time. Here we present the role of soils in habitat formation and maintenance in natural systems, and reflect on how humans have modified soils from local to global scale. Soils host a tremendous diversity of life forms, most of them microscopic in size. We do not yet know all the functionalities of this diversity at the level of individual taxa or through their interactions. However, we do know that the interactions and feedbacks between soil life, plants and soil chemistry and physics are essential for soil and habitat formation, maintenance and restoration. Moreover, the couplings between soils and major cycles of carbon, nutrients and water are essential for supporting the production of food, feed and fibre, drinking water and greenhouse gas balances. Soils take thousands of years to form, yet are lost very quickly through a multitude of stressors. The current status of our soils globally is worrisome, yet with concerted action we can bend the curve and create win-wins of soil and habitat conservation, regeneration and sustainable development. This article is part of the theme issue 'The role of soils in delivering Nature's Contributions to People'.

Global diversity and ecological drivers of lichenised soil fungi

Lichens play crucial roles in sustaining the functioning of terrestrial ecosystems; however, the diversity and ecological factors associated with lichenised soil fungi remain poorly understood. To address this knowledge gap, we used a global field survey including information on fungal sequences of topsoils from 235 terrestrial ecosystems. We identified 880 lichenised fungal phylotypes across nine biomes ranging from deserts to tropical forests. The diversity and proportion of lichenised soil fungi peaked in shrublands and dry grasslands. Aridity index, plant cover and soil pH were the most important factors associated with the distribution of lichenised soil fungi. Furthermore, we identified Endocarpon, Verrucaria and Rinodina as some of the most dominant lichenised genera across the globe, and they had similar environmental preferences to the lichenised fungal community. In addition, precipitation seasonality and mean diurnal temperature range were also important in predicting the proportion of these dominant genera. Using this information, we were able to create the first global maps of the richness and the proportion of dominant genera of lichenised fungi. This work provides new insight into the global distribution and ecological preferences of lichenised soil fungi, and supports their dominance in drylands across the globe.

Above- and belowground biodiversity drives soil multifunctionality along a long-term grassland restoration chronosequence

Restoring degraded land is an efficient strategy for improving biodiversity and ecosystem functioning. However, the effects of aboveground and belowground biodiversity on multiple ecosystem functions (multifunctionality) during ecological restoration are not well understood. Here, the relationships between plant and microbial communities and soil multifunctionality were assessed in a 30-year natural grassland restoration chronosequence on the Loess Plateau, China. Soil multifunctionality, in relation to the carbon, nitrogen, phosphorus, and sulfur cycles, was quantified. Soil bacterial and fungal communities were analyzed by high-throughput sequencing using the Illumina HiSeq platform. The results showed that soil multifunctionality was significantly increased with the increasing period of grassland restoration. Plant and bacterial diversity, rather than fungal diversity, were significantly and positively correlated with soil multifunctionality based on single functions, averaging, and multiple threshold approaches. Random forest and structural equation modeling analyses showed that soil multifunctionality was affected by both biotic and abiotic factors. Plant diversity and bacterial community composition had direct effects, whereas plant community composition had both direct and indirect effects on soil multifunctionality. Restoration period and soil pH indirectly affected soil multifunctionality by altering plant and bacterial communities. This work demonstrates the importance of aboveground and belowground biodiversity in driving soil multifunctionality during grassland restoration. The results provide empirical evidence that conserving biodiversity is crucial for maintaining ecosystem functions in restored areas.

The multidimensionality of soil macroecology

The recent past has seen a tremendous surge in soil macroecological studies and new insights into the global drivers of one-quarter of the biodiversity of the Earth. Building on these important developments, a recent paper in Global Ecology and Biogeography outlined promising methods and approaches to advance soil macroecology. Among other recommendations, White and colleagues introduced the concept of a spatial three-dimensionality in soil macroecology by considering the different spheres of influence and scales, as soil organism size ranges vary from bacteria to macro- and megafauna. Here, we extend this concept by discussing three additional dimensions (biological, physical, and societal) that are crucial to steer soil macroecology from pattern description towards better mechanistic understanding. In our view, these are the requirements to establish it as a predictive science that can inform policy about relevant nature and management conservation actions. We highlight the need to explore temporal dynamics of soil biodiversity and functions across multiple temporal scales, integrating different facets of biodiversity (i.e., variability in body size, life-history traits, species identities, and groups of taxa) and their relationships to multiple ecosystem functions, in addition to the feedback effects between humans and soil biodiversity. We also argue that future research needs to consider effective soil conservation policy and management in combination with higher awareness of the contributions of soil-based nature's contributions to people. To verify causal relationships, soil macroecology should be paired with local and globally distributed experiments. The present paper expands the multidimensional perspective on soil macroecology to guide future research contents and funding. We recommend considering these multiple dimensions in projected global soil biodiversity monitoring initiatives.