Recent studies and global meta-analyses suggest that soil fauna is a key driver of litter decomposition. However, most research has focused on lowland ecosystems, leaving tropical mountain regions underexplored. Our study investigated the influence of the taxonomic and functional structure of soil fauna communities on litter decomposition in successional upper Andean tropical forests. We conducted two reciprocal translocation experiments: one examining 15 litter species (2525 litterbags) and another analyzing macrofauna exclusion (336 litterbags). We also performed extensive soil fauna sampling across four climatic seasons (6999 individuals) and measured body size traits for 93% of the morphospecies. We analyzed the role of soil fauna attributes (richness, abundance, body size) on litter decomposition at the species and ecosystem levels in four sites of successional upper Andean tropical forests in Colombia. Our findings indicated that soil fauna has little influence on decomposition, yet the effect varies by species, suggesting specific affinities between soil fauna and litter substrates. The lack of influence of soil fauna richness, abundance, and body size can be attributed to the dominance of small-sized fauna in upper Andean tropical forests. The contribution of soil macrofauna to decomposition was higher in mature forests, but this effect was weak over time. Further studies should explore indirect effects and microbial interactions to better understand soil faunaʼs role in decomposition. Our study highlights that the influence of soil fauna on decay rates is context-dependent and should not be generalized across all ecosystems.
This study examines the effects of different organic carrier materials, chicken manure, mill mud, and cow manure on the long-term viability and metabolite profiles of rhizobacterial strains Mesorhizobium sp. and Rhizobium sp. Over one year, growth curve analysis revealed significant differences in bacterial proliferation. Mill mud supported the most robust growth, with a doubling of 11 days, compared to chicken and cow manure, which exhibited growth saturation after five to eight months. Non-targeted 1H-NMR metabolite profiling revealed distinct sugar and amino acid profiles across carriers. Mill mud exhibited a broader range of sugars, including sucrose, maltose, and mannose, while chicken and cow manure primarily contained monosaccharides like glucose, xylose, and mannitol. Amino acids such as lysine and glutamate were higher in chicken manure, followed by cow manure and mill mud. Plant growth-promoting metabolites were detected in all carriers, with Mesorhizobium sp. and Rhizobium sp. enhancing their production by up to 200% in mill mud and cow manure. Both bacterial strains utilized sugars from the carriers, with Mesorhizobium sp. showing more consistent sugar metabolism. These findings suggest that mill mud is an effective carrier for sustaining rhizobacterial viability and enhancing metabolite production, benefiting biofertilizer formulations and soil health.
As an essential base for agricultural products in Baiquan County China, the black soil inthe Northeast region had soil nutrient contentsup to several times that of ordinary soil. However, over-exploitation and utilization in recent years led to a decline in the quality of black soil. Therefore, it is strategic significance to study the improvement of soil quality by different shelterbelts. In order to explore the interaction between soil microbial and nutrients, the soils under four shelterbelts (pure Pinus sylvestris forest, pure Larix gmelinii forest, mixed Pinus sylvestris forest and mixed Larix gmelinii forest) were used as the research materials in Baiquan County, Heilongjiang Province, China. The changes of soil physicochemical properties and soil microbial function genes were studied, and their interaction patterns were analyzed by Redundancy analysis (RDA). The results showed that the concentration changes of TOC (total organic carbon), TN (total nitrogen),
The alkaline phosphatase (phoD) gene-encoding bacterial communities (phoD-harbouring communities, hereafter) play crucial roles in organic phosphorus (Po) mineralisation across global terrestrial ecosystems. However, their geographic distribution and driving factors remain unclear, largely due to the mosaic temperature and humidity patterns and the lack of comprehensive high-resolution sampling data across the Qinghai-Tibet Plateau. We addressed this gap using amplicon sequencing techniques and analyses of soil properties as well as plant biomass. Plant biomass, soil organic carbon (C), Po content, C:P ratio, alkaline phosphatase (ALP) activity, and the richness and abundance of key soil phoD-harbouring taxa were higher in warmer, more humid regions, such as the southeastern plateau than the northeastern plateau, while soil pH followed an inverse trend. Soil pH and Po content emerged as the key factors shaping the geographic distribution of phoD-harbouring communities. Acidic soils were associated with higher C:P ratios, community richness, ALP activity, and Po content than alkaline soils. Our findings suggest that warmer, more humid regions promote soil acidification, which in turn drive changes in phoD-harbouring communities, enhance ALP activity, and stimulate Po mineralisation. This study provides new insights into the geographic distribution of phoD-harbouring communities and their role in Po mineralisation across the Qinghai-Tibet Plateau.
The soil nitrogen cycle is primarily driven by microbial communities and provides reactive nitrogen for all organisms. With the increasing impact of human activities and climate change, biogeographical explicit patterns of soil microbial nitrogen-cycling genes and their associations with nitrogen fluxes are still unknown at the global scale. By conducting a global analysis of 1198 soil metagenomic samples, we verified that agricultural land displayed lower microbial richness and diversity values than did the other habitats. We generated a global map of the genetic potential of N cycle processes in soil and revealed that denitrification and dissimilatory nitrate reduction processes are greater in agricultural centers than in non-agricultural areas and are mainly driven by the mean annual temperature and nitrogen fertilizer application. Soil nitrous oxide (N2O) emissions are greater in agricultural land than in other habitats and are mainly driven by nitrogen fertilizer application, which is consistent with the genetic potential of N2O synthesis. Our study improves the theoretical framework for predicting global soil nitrogen cycling potential under complex variables and highlights the influence weight of human activities and climate factors. We strongly emphasize the importance of rationally applying nitrogen fertilizers to balance agricultural production, ecological health and climate change.
Granulating fluffy straw into high-density particles is an innovative approach for uniformly incorporating straw into plough layers. However, massive granulated straw incorporation probably causes microbial nutrient limitation, decreasing straw-C accrual and crop yield. Whether nutrient supplement increases straw-C accumulation remains unclear. In this study, we conducted one-year of micro-plot experiments incorporating massive granulated straw with initial C:N ratio (GS) and adjusted the C:N ratio by nutrient supplement (GSN) in infertile upland and paddy. After one year,GS incorporation greatly improved the surface (0–20 cm layer) soil organic C by 91% and 80% in upland and paddy, respectively, compared to their control. In upland, GS led to lower lignin phenols but higher amino sugars than paddy owing to its stronger microbial anabolism. In upland, GSN incorporation decreased soil organic C by 11.3% than GS by reducing lignin phenols and amino sugars. However, GSN incorporation increased organic C by 2.2% in paddy, via promoting microbial necromass accumulation. GSN incorporation improved crop yield by 26.6% in upland and 12.0% in paddy than GS. Collectively, granulated straw incorporation effectively enhances organic C and crop yield but that responses to nutrient supplement depend on soil properties. Tailored nutrient management is crucial to optimizing C sequestration and productivity in diverse soils.
The transformation of mountainous karst forests into urban parks requires a detailed evaluation of its impact on existing ecosystems, particularly in terms of the interplay between soil characteristics and plant diversity. In this study, we examined the species diversity of woody plants and soil characteristics within three established urban parks in Guiyang, China. We analyzed how habitat modification and the age of these parks influence soil properties and the diversity of woody plants. Our study revealed that soil levels of organic carbon, nitrogen, phosphorus, and potassium in artificial green spaces were significantly lower than in remnant forests. Woody plant alpha-diversity exhibited a negative correlation with potassium in remnant forests, but with phosphorus in artificial spaces. Interestingly, the associations between plant α-diversity and soil organic carbon and nitrogen were not significant in older parks, but were evident in newer ones. Furthermore, nitrogen, phosphorus, and potassium content significantly influenced woody plant composition across these parks. Habitat type and soil properties impacted the compositional diversity of woody plants more than park age, with phosphorus exerting the most substantial effect. In order to balance human recreational activities with the conservation of native ecosystems, it is essential to develop strategic management plans that prioritize soil enrichment and the maintenance of biodiversity in urban mountain parks.
Spatial distribution of soil organic carbon (SOC), and total nitrogen (TN) contents in different aggregate fractions (DAFs) were investigated by applying multiple machine learning models (MLMs) i.e., cubist (CB), support vector regression (SVR), and random forest (RF), along with environmental variables in the framework of digital soil mapping (DSM). One hundred samples were taken from the soil surface layer (0−15 cm) in the Aji-Chai watershed, in northwestern Iran. TN and SOC were measured in three soil aggregate sizes (macro, meso, and micro-aggregates). Among the studied machine learning models (MLMs), the RF model revealed exceptional performance and the lowest uncertainty for predicting SOC and TN contents in DAFs. The R2 values for the prediction of SOC in DAFs were 0.86 for SOCmacro, 0.83 for SOCmeso, and 0.81 for SOCmicro. For the TN content in different fractions, the R2 values were ordered as 0.70 for TNmacro, 0.71 for TNmeso, and 0.73 for TNmicro, respectively. Variable importance analysis (VIA) results indicated that factors like vegetation indices such as Corrected transformed vegetation index (CTVI), and normalized difference vegetation index (NDVI), followed by topographic attributes, had a substantial impact in exploring SOC and TN contents in DAFs. In macro-aggregates, the highest SOC and TN contents were found in dense pasture, semi-dense vegetation, and orchards. Conversely, in meso- and micro-aggregates, the lowest contents were observed in rainfed agricultural lands, sparse pastures, and barren regions, respectively. The modeling results open new windows in the field of soil fertility and physics intending to link the content of SOC and TN variation in DAFs. Ultimatly, the RF model demonstrates strong predictive capabilities for SOC and TN contents in DAFs, achieving impressive R² values. Influential factors include vegetation indices and topography. The resulting prediction maps significantly enhance spatial planning and guide sustainable land management practices, effectively linking soil quality indicators to specific land-use types for improved soil health.
The upward shift of the alpine treeline driven by global climate change has been extensively observed across many mountain ecosystems worldwide. However, variations in belowground microbial communities in the treeline ecotone, as well as the influence of microtopographic factors (e.g., slope aspect) on these changes, remain unclear. Here, we collected soil samples from different aspects above or below the treeline and analyzed the microbial communities using high-throughput sequencing. Our study revealed distinct community characteristics, co-occurrence patterns, and assembly processes between bacterial and fungal communities. Especially, homogeneous selection and dispersal limitation played dominant roles in shaping bacterial and fungal communities, respectively. Keystone bacteria were more critical for maintaining network stability above the treeline, while fungi were the keystone taxa for network stability below the treeline. We also found that oligotrophic species such as Acidobacteriota, Chloroflexi, Verrucomicrobiota, and Ascomycota were predominantly enriched above the treeline, whereas copiotrophic species like Proteobacteria, Gemmatimonadota, Actinobacteriota, and Firmicutes were more abundant below the treeline. Our results uncovered that microbial communities responded greatly to treeline shift than slope aspect, and also imply that the upward shift of the alpine treeline may increase the stochasticity of microbial communities. These findings facilitate our understanding of how microbial communities in the treeline transition zones of alpine ecosystems respond to global warming and their potential effects on soil carbon dynamics.
Nitrite-dependent anaerobic methane oxidation (n-damo), performed by the bacteria associated with Candidatus Methylomirabilis oxyfera, acts as a novel methane sink in coastal wetlands. Conversion of coastal wetlands into paddy fields is a common land-use change that has profound effects on methane emissions, but its impact on n-damo process is nearly unknown. Our study adopted a space-for-time substitution method to compare n-damo activity and community of Methylomirabilis-like bacteria between natural vegetation covered by Phragmites australis, Kandelia candek, or Bruguiera sexangula and adjacent converted paddy fields in six China’s coastal wetlands. Generalized linear mixed model indicated that the activity of n-damo significantly increased by 43.6% and 165.8% after conversion of K. candek and B. sexangula wetlands into rice paddies, respectively, while the activity exhibited no significant change after conversion of P. australis wetlands. Furthermore, the abundance of Methylomirabilis-like bacteria significantly increased by 90.2%, 210.0%, and 110.1% following the conversion in wetlands covered by K. candek, B. sexangula, and P. australis, respectively. Principal co-ordinates analysis revealed significant changes in community structure of Methylomirabilis-like bacteria among vegetation types, with K. candek and B. sexangula showing a greater divergence than P. australis when compared to respective paddy fields. Path analysis indicated that land conversion resulted in changes in soil moisture content, organic carbon content, bulk density, and salinity and further affected the abundance of Methylomirabilis-like bacteria and ultimately n-damo activity. Overall, this is the first study to reveal the impact of conversion of coastal wetlands into paddy fields on n-damo activity and Methylomirabilis-like bacteria, and the impact was closely associated with the original native plant types. The results can enhance our understanding of the microbial-driven mechanisms of the impact of land conversion on methane emissions.
Elucidating the intricate dynamics of microbial communities across soil profiles is essential for deciphering the mechanisms by which microorganisms regulate ecosystem functions. However, previous studies on soil microorganisms have predominantly centered on abundant taxa, neglecting the significant role of rare taxa in maintaining ecosystem functions. This study comprehensively analyzed the diversity and assembly processes of both rare and abundant microbial taxa in the profiles of Udic and Ustic Isohumosols in northeast China. We also explored the relative contribution of rare and abundant microbial taxa in maintaining ecosystem multifunctionality. Results showed that rare microbial taxa exhibited a higher diversity compared to abundant taxa, and rare microbial taxa occupied more central positions within networks. Furthermore, rare taxa displayed narrower ecological niche breadths and stronger phylogenetic signals, and their community assembly was predominantly governed by deterministic processes. In contrast, stochastic processes exert more pronounced influences on the assemblage of abundant taxa. Ecosystem multifunctionality was significantly reduced in deep soil horizons relative to the surface soil horizons. This is accompanied by close cooperation of microorganisms to cope with environmental stress in deep soils. This study highlights the pivotal role of rare microbial communities in shaping multifunctionality of ecosystems across the entire soil profiles.
Organic mulching is widely applied in agricultural and forest ecosystems to improve crop yields and maintain soil quality. However, its long-term impact on soil organic carbon (SOC) stability and the underlying mechanisms remain unclear. An in situ experiment was initiated in 2018 in the subtropical region of China, with the non-mulched treatment serving as the control group (0 year of mulching), to investigate the effects of mulching on the organic carbon components (particulate organic carbon, POC, and mineral-associated organic carbon, MAOC) in Phyllostachys praecox bamboo forests across different mulching durations of 1, 3, and 5 years. Our results indicated that five-year mulching decreased soil POC concentration by 13.36%, while increasing MAOC and SOC by 130.3% and 64.53%, respectively, compared to no mulching. The POC/MAOC ratio dropped, indicating improved SOC stability. Additionally, soil pH decreased with mulching duration, while bacterial and fungal diversity, available phosphorus content, and β-xylosidase activity significantly increased. Structural equation modeling indicated that POC was mainly regulated by available phosphorus and fungal communities. While MAOC was affected by soil pH, which also mediated its response by influencing enzyme activity and bacterial diversity. In bamboo forest ecosystems, long-term organic mulching enhances SOC sequestration and stability, providing insights into SOC management for sustainable forestry. Such information indicates continuous mulching can be used to improve SOC sequestration in subtropical bamboo ecosystems.
Soil extracellular enzymes play a central role in regulating soil organic carbon (SOC) dynamics. However, the effects of varying warming magnitudes and duration on permafrost soil carbon-degrading enzyme activities remain poorly understood. Here, we investigated warming effects on three representative carbon-degrading enzymes (β-1,4-glucosidase (BG), peroxidase (PER), phenol oxidase (POX)) in alpine and swamp meadows on the Qinghai-Tibet Plateau. The warming experiments were conducted using Open-top chambers at different warming magnitudes (+2.4 and +4.9 °C) and duration (3 and 6 years) in both meadows. The activity of BG increased with warming duration in alpine meadows regardless of the warming magnitude (69% and 45% for lower and higher warming treatments, respectively), although the effect was significant (p<0.05) only under 6-year warming. In contrast, warming did not significantly (p>0.05) alter BG activity in swamp meadows. Warming decreased POX activity in both alpine (62%) and swamp meadows (81%), but the effect was significant only under 6-year higher warming. Moreover, PER activity was not significantly influenced by warming in either meadow. Dissolved organic carbon and above-ground biomass were the primary factors influencing soil enzyme activities under warming in alpine meadow, while soil water content in swamp meadow. Noticeably, a negative correlation (p<0.05) was observed between SOC and oxidase/hydrolase activity in alpine meadow, suggesting the suppression of oxidase activity may benefit SOC storage under warming. Noticeably, a negative correlation (p<0.05) between SOC and oxidase/hydrolase activity was found in alpine meadow but not in swamp meadow, which was due to the difference in above-ground biomass. These findings highlight the need to consider the time-cumulative warming effects on plant growth and enzyme ratios in carbon models to improve the accuracy of model predicting of soil carbon dynamics in permafrost regions.
Slow-release nitrogen fertilizer (SNF) has potential for enhancing wheat yields in saline-alkali soils, but its mechanisms in salt tolerance remains unclear. This study utilized an enhancer-coated nitrogen fertilizer to prepare SNF and aimed to investigate its effectiveness in improving wheat resistance and increasing wheat yield in saline-alkali soil, compared to conventional nitrogen fertilizer (CNF). The two years experiment was conducted during 2020‒2022, split by four treatments: CK (299.86 kg ha‒1 CNF), T1 (299.86 kg ha‒1 SNF), T2 (239.89 kg ha‒1 SNF), and T3 (179.92 kg ha‒1 SNF), using Taimai 198 wheat. SNF significantly reduced soil conductivity and increased alkaline hydrolyzed nitrogen (AHN), urease, andprotease activities. It also enhanced soil microbial diversity, such asProteobacteria, Actinobacteria, and Gemmatimonas, etc. SNF treatments boosted osmoregulatory substances (proline, soluble sugars, K+/Na+) in wheat flag leaves under saline-alkali soil, and improved antioxidant enzyme activities, such as superoxide dismutase (SOD) and peroxidase (POD), while reducing malondialdehyde (MDA) content. In terms of wheat yield, compared to CK, T1 and T2 increased by 12.03%‒13.16% and 8.05%‒8.63%, respectively. SNF enhances wheat resistance in saline-alkali soils by improving soil properties, increasing osmoregulatory substances, and boosting antioxidant enzyme activity, leading to increased wheat yield.
Conspecific negative density dependencies (CNDDs) foster biodiversity through reducing the chances of competitive exclusion in plant communities and have therefore fascinated ecologists. A major driver of CNDDs is plant-soil feedback, and a lot of the literature assumes that the triggers of CNDDs concur with those for plant-soil feedback. Here, we suggest that a core assumption of a lot of the literature on CNDDs, that CNDDs are stronger in AM-associated than ECM-associated trees, is not quite as well supported as widely claimed. We think that dismissing this very important consideration prevents us from identifying a major gap in the literature on CNDDs. The vast majority of the literature on mycorrhiza-induced CNDDs originates from temperate systems, but the findings are extrapolated across divergent ecosystems. We then develop the argument that likely propagule limitations for arbuscular mycorrhizal trees in temperate forests might be inducing stronger CNDDs than they do at propagule sufficiency, which arbuscular mycorrhizal trees usually experience in other systems. We are thus contributing a new hypothesis in the field of mycorrhizal ecology with the potential to unify observations across scales and biomes.
Global agricultural soils are experiencing rapid acidification due to atmospheric deposition and excessive fertilizer applications. Soil acidification deteriorates soil health and disrupts dynamics of soil microorganisms, threatening soil ecosystem function. However, the underlying mechanisms of acidification impacting community assembly of soil abundant and rare microbial taxa remain elusive. Here, we investigated the soil bacterial and fungal community compositions, functions, and assemblies of both abundant and rare taxa in agricultural soil that has undergone 16 years of acidification, spanning three pH gradients (pH 4.0, 6.5, and 8.0). Our results indicated that soil acidification differentially altered the co-occurrence patterns and driving factors of bacterial and fungal communities. In acidic soils, the assembly of bacterial communities was primarily governed by deterministic processes, whereas fungal communities were predominantly influenced by stochastic processes. Acidification increased the prevalence of deterministic processes among rare taxa compared to abundant taxa within bacterial and fungal communities. This significantly diminished the complexity and stability of soil microbial interactions, resulting in an imbalance within soil microbiomes under acidification. Additionally, acidification significantly impaired bacterial functions related to carbon and nitrogen metabolism. Overall, these findings provide insights into microbial population succession in long-term acidifying soils, and into our understanding of biological amelioration strategies for soil acidification.
Exploring methane-metabolizing microorganisms' distribution patterns and driving factors is significant for estimating the global methane budget, but our current knowledge is limited. In this study, we took a systematic soil and microbial survey along the coast of river channels in the Yellow River Delta, which included the most rapidly deposited sedimentation globally. The prokaryotes, fungi, and protists had more significant changes between two regions with distinct deposition ages than across soil depths, while the accumulation of soil organic matter was the most critical external driving force for the succession of microbial communities. The deposition ages of sedimentary soils also altered the methanogenic and methanotrophic communities, with methanogens showing a greater response to environmental gradient changes than methanotrophs. The distribution of methanogens was mainly influenced by the direct regulation of biological factors represented by fungi and indirectly regulated by environmental stresses along the sedimentation gradient. Our self-developed inter-domain ecological network platform has further investigated the inter-trophic relationships between methane-metabolizing microorganisms and other microbes. Methanogens and methanotrophs form the core species of a highly interconnected network, and there is a strong interdependence between them and fungi and protists, while other prokaryotic species are relatively independent, in addition, methanogens play a central role in species interactions as modular hubs, they tended to be associated with saprotrophic fungi in the older sedimentation region, while in the newer sedimentation region, they were more associated with bacterial groups. This study enhances our understanding of the microbial hierarchical web in coastal wetland ecosystems.
The management of phosphorus (P) is challenged by the disruption of the soil natural phosphorus cycle, primarily due to over-fertilization. However, less research has been done on how fertilization affects organic acids secreted by roots, which in turn affects bacteria harboring the pqqC and phoD genes. Employing high-throughput sequencing and quantitative PCR, we analyzed the impact of various fertilizer treatments on these bacterial communities. Our research reveals that both organic and inorganic fertilizers alter soil pH, a change that is closely linked to changes in oxalic, gluconic, and succinic acids in the soil. These secretions subsequently modify the composition of pqqC and phoD-harboring bacterial communities, thereby enhancing P solubilization. Our findings suggest that while inorganic fertilizers can increase P-solubilizing bacterial populations by elevating soil pH, organic fertilizers not only boost these bacterial communities but also maintain the P content in the soil, thereby directly supporting P utilization. After the application of organic fertilizers, the content of lactic acid and gluconic acid can not only indirectly affect the abundance of P solubilizing bacteria by increasing soil pH, but also directly increase the effective P content of the soil. Additionally, the introduction of nitrogen (N) and potassium (K) alongside P fertilization appears to fine-tune this microbial-plant interaction, paving the way for more efficient P use in agriculture. Consequently, our research provides sustainable strategies for enhancing agricultural productivity amid P management challenges.
The understanding of plant-microbe interactions in terms of core and/or keystone taxa is crucial for enhancing plant stress tolerance. Nevertheless, the investigation of this key component of microbiome associated with plants thriving in extreme environments, like non-mycorrhizal sedges on the Qinghai-Tibet Plateau, has been relatively limited. In this study, we employed frequency-abundance methods and molecular ecological network analysis to identify the core and keystone taxa of fungi and bacteria in both rhizosphere soil and root endosphere of Carex cepillacea. The results revealed a substantial number of unique taxa in both core and keystone taxa, with Sphingomonas and Gibberella representing core taxa, while Nocardioides and Truncatella serve as the keystone taxa. Specifically, there was a considerably higher proportion of exclusive taxa in the keystone taxa (bacteria: 48.8%, fungi: 55.4%) compared to that observed in core taxa (bacteria: 16.3%, fungi: 10.7%). Regarding microorganisms inhabiting rhizosphere soil, total nitrogen (TN) primarily influenced the assembly of core communities while available phosphorus (AP) played a major role in shaping the keystone communities. Within the root endosphere, both the core and keystone microbial communities were significantly more influenced by soil carbon and TN nutrients compared to other factors. It is noteworthy that certain “common core” taxa, such as Actinoplanes, Blastococcus, Penicillium, and Fusarium, exhibited high interconnectedness within the entire microbiome network. Considering the contribution of keystone taxa is significantly enhanced when they are part of the core taxa, these findings can provide a foundation for the development of microbial formulations based on key constituents of the microbiome.
Human-driven nitrogen (N) deposition profoundly affects the functional composition and energetic structure of soil food webs, which are crucial for maintaining ecosystem stability and nutrient cycling. Karst landscapes, occupying about 15% of the Earth’s surface, are particularly fragile due to shallow soils, nutrient deficiency, and well-developed underground drainage systems. In these regions, deposited N may be readily absorbed by plants and/or rapidly leached with rains; its effects on karst ecosystem processes and functions may be different from non-karst regions. Here, the effects of N deposition on the community structure and energy dynamics of soil nematodes and nutrient cycling processes, and their relationships were explored. A canopy N deposition experiment was conducted with three levels of N addition: control (0 kg N ha−1 yr−1), low (50 kg N ha−1 yr−1), and high (100 kg N ha−1 yr−1). Both low and high N additions increased plant litter production but did not alter litter stoichiometry or soil properties. High N addition significant reduced total nematode abundance and energy fluxes through bacterivores in the dry season, while in the wet season showed no significant effects, likely due to rapid nutrient leaching in karst soils. Additionally, soil carbon and nitrogen mineralization rates under N addition were more closely linked to nematode abundance than energy fluxes. This study provides valuable insights into how future changes in N deposition affecting below-ground communities and nutrient cycling in the karst region, and enhancing our understanding of the responses of this environment to global changes.
Mangroves show a biogenic response to adjust sea-level rise by accumulating sediment and carbon (vertical soil accretion), reshaping their structure and composition to minimize the effects. Additionally, the often-overlooked factors of soil nutrient availability, functional traits, and stand structure can alter the mangrove diversity-salinity-productivity link. However, how these multiple drivers interplay to maintain growth against salinity still needs to be better understood. Considering all these, we answered two questions: (QI) How do species diversity and structural heterogeneity modulate growth vs. salinity relationships? (QII) To what extent can structural heterogeneity and species diversity create optimal conditions by minimizing the adverse effects of salinity while concurrently maximizing forest growth? To comprehensively understand the interplay between structural and species diversity, nutrient availability, functional traits, and rising salinity, we examined a dataset from 60 permanent plots established in the Sundarbans mangrove forest in Bangladesh. Our results indicated that species diversity less directly contributed to forest growth than structural heterogeneity, nutrient availability (N, P, and K), and leaf area index. While forest structural and species diversity alone is unlikely to optimize growth, incorporating nutrients into the models showed a slight improvement in buffering against salinity. However, when nutrients were combined with the leaf area index, the models indicated a much stronger enhancement in the forest’s resilience to salinity through interactions with these factors, allowing continued growth. In conclusion, our study highlights the relative contributions of species and structural diversity to mangrove growth under stress and the potential roles of nutrients and functional traits. These findings are valuable for forest growth modelling, informing conservation and management strategies for mangroves, particularly in coastal plantations facing environmental changes.
Forest soil carbon (C) accumulates predominantly from the decomposition of plant litter, with most plant-derived C being processed by soil microbes. However, the microbial mechanisms associated with C decomposition in forests across biomes remain elusive. Using metagenomic sequencing, we explored the topsoil microbial functional group of decomposer microbial carbohydrate-active enzymes (CAZyme) and studied the C decomposition of plant- and microbial-derived components in forests across biomesfrom tropical to temperate regions. The results showed that the composition of soil microbial CAZyme families, which degrade plant- and microbial-derived components, significantly varied from warmer to colder forest biomes. Soils with higher annual temperatures and lower organic matter (OM) recalcitrance (indicated by Alky-C/O-alkyl-C: A/O) in subtropical/tropical forests supported higher proportions of CAZyme genes fundamental for the decomposition of complex plant and fungal derived biomass. In contrast, soils with lower annual temperatures and higher OM recalcitrance (e.g., A/O, organic carbon, microbial biomass) in cold temperate forests exhibited higher proportions of CAZyme genes for the degradation of bacterial-derived peptidoglycan. Such trends of microbial CAZyme families were largely explained by the relative abundance of bacterial dominant phylum members (i.e., Proteobacteria, Actinobacteria, Acidobacteria, and Bacteroidetes). Collectively, our study demonstrated the importance of functional microbiome responsible for the decomposition of plant and microbial inputs, providing a solid mechanism to understand the often-reported responses of soil organic matter decomposition and C sequestration to warming. These results are integral to understanding the contribution of soil microbiome to C fluxes under on-going climate change.
Although the contribution of biodiversity to supporting ecosystem functions is well established in soil ecosystems, previous studies have often overlooked the importance of potential multitrophic interactions in supporting ecosystem functions. This study analyzed the effects of land uses on potential multitrophic interactions and their impacts on soil ecosystem functions, using soil environmental DNA samples from five land-use types. Results showed that land use can influence soil ecosystem functions by altering the soil multitrophic biodiversity and interactions. Keystone species are crucial in shaping the soil microbial composition, mediating network interactions, and supporting the ecosystem function. This study promotes the understanding of the mechanisms behind changes in biodiversity and ecosystem services resulting from land-use changes and is beneficial to making informed trade-offs in urban planning.
Understanding the temperature sensitivity (Q10) of soil carbon (C) decomposition and the driving forces is vital for projecting soil C dynamics under climate warming. However, it is unclear of the geographic patterns in Q10 and its driving forces in water-limited regions. We measured Q10 of C decomposition and multiple facets of both C quality and microbial properties, including microbial diversity, abundance, composition, activity, and trophic strategy from two soil depths (0−10 cm, 30−50 cm) collected at 38 sites along a 2000-km transect in northern China’s deserts. Q10 ranged in 1.56−4.80 and was significantly higher in the top (3.21) than deep soil (2.61). The large variation in Q10 is directly determined by microorganisms, rather than C quality which is the ratio of microbial C decomposition rate over soil organic C content. Microbial diversity, the ratio of fungi to bacterial abundance (F:B), and mass-specific respiration (qCO2) were driving forces for spatial variation in Q10. Microbial diversity negatively impacted Q10, while higher F:B and qCO2 stimulated Q10. Higher C quality indirectly inhibited Q10 by improving microbial diversity, and decreasing F:B and qCO2. Our study demonstrates that microorganisms drive the geographic variations in Q10.
Tropical forest soils are susceptible to acidification owing to high weathering rates and low buffering capacity. Nutrient additions, particularly nitrogen (N) and phosphorus (P) inputs, can alter soil acidity; however, their long-term effects on the dynamics and underlying mechanisms of soil pH in tropical rainforests are not well understood. Here, we conducted two 13-year N and P fertilization experiments in primary and secondary tropical montane rainforests in Hainan, China. Results showed that long-term high-N addition reduced soil pH, and the effects increased with the rate and duration of N addition in both rainforests. The P-limited primary rainforest was more susceptible to N-induced soil acidification than the N-limited secondary rainforest with higher stand density during the experimental periods. Moreover, the depletion of base cations (primarily Ca2+) and the generation of exchangeable H+ were the main drivers of N-induced soil acidification. However, low- and medium-N additions, single P addition, and combined N and P addition did not significantly change soil pH or cation concentrations in both forests. These findings suggest that elevated soil N availability induced by long-term fertilization may alter soil cation composition, thus leading to soil acidification and impacting ecosystem functions in tropical forests.
