● Ant morphological traits (dry mass, head length, body size and leg length) increased with elevation.

Understanding the responses of species to changing climates is becoming increasingly urgent. Investigating the effects of climate change on the functional traits of species at the intraspecific level is particularly important. We used elevation gradients as proxies for climate change to explore the intraspecific responses of two ground-dwelling ant species, Ectomomyrmex javanus and Odontoponera transversa, from 100 to 700 m.a.s.l. within a subtropical evergreen broadleaf forest. Our study addressed the specific relationships among environmental factors, trait variations, and trophic levels. Key functional traits such as dry mass, head length, body size, and leg length exhibited a general increase with elevation. Using stable isotope signatures (δ¹³C and δ¹⁵N), we quantified shifts in diets and trophic positions along the elevation gradients. Notably, our data revealed a significant elevation-related increase in Ant δ¹³C, whereas δ¹⁵N exhibited no such correlation. Moreover, Ant δ¹³C values of E. javanus demonstrated a negative correlation with mean annual temperature (MAT), and the δ¹³C values of both species correlated positively with soil C:N ratio. Having revealed that the individual traits and δ¹³C signatures of ground-dwelling ants exhibit significant negative correlations with temperature, our findings suggest that climate warming has the potential to cause intraspecific variation in the functional traits and diets of ground-dwelling ants and possibly other insect species.

● Arsenic characteristics in earthworms and soils across 47 sites in China were studied.

The total arsenic (As) and As species of earthworm body tissues and surrounding soils were investigated in 47 locations (16 forested lands and 31 agricultural lands) at a national scale across China using inductively coupled plasma-mass spectrometer (ICP-MS) and high-performance liquid chromatography-inductively coupled plasma-mass spectrometer (HPLC-ICP-MS). Earthworm body tissues had an average total As concentration of 6.21 mg kg⁻¹, significantly lower than the soil As concentration of 12.99 mg kg⁻¹. The ratio of arsenite to arsenate (As^III/As^V ratio) in earthworm body tissues (67%) was significantly higher compared to that in surrounding soils (19%). HPLC-ICP-MS analysis detected small amounts of organic As forms, such as arsenobetaine (2.9%), dimethylarsinic acid (1%), and monomethylarsonic acid (0.3%), mainly in earthworm tissues from certain locations. The total As content and As^III/As^V ratio in earthworm tissues exhibited a strong positive correlation with soil NO₃⁻ content. This field study enhances our understanding of As concentration and speciation in earthworm body tissues across China, contributing valuable insights into the biogeochemical cycle of As and its biological risks in diverse soil ecosystems. These findings provide crucial evidence for policymakers to formulate strategies addressing and mitigating soil As pollution and associated health risks.

● Nitrogen fertilizers’ effects on protists in three paddy field soils were analyzed.

Protists are one of the most diverse and dominant microbial groups and they play critical roles in the soil ecosystem. Although nitrogen fertilizers have a profound impact on protist communities, still less is known about how different nitrogen fertilizer types affect protist community composition in different soil types. Here we investigated the effects of six inorganic nitrogen fertilizers (urea, ammonium nitrate, ammonium sulfate, potassium nitrate, ammonium chloride, and diammonium hydrogen phosphate) and an organic fertilizer (a mixture of rice husk and cow manure) on protist community composition in three paddy field soils using a high-throughput sequencing method. The effect of the fertilizers on the functional groups of protists, namely consumers (predators and decomposers), photoautotrophs, and parasites (plant pathogens and animal parasites) was also analyzed. The results showed that nitrogen fertilizers had distinctive effects on the beta diversity of the protists, while we also observed that the same fertilizer had slightly different effects depending on the soil type. Amoebozoa and Rhizaria were the most affected protist taxonomical groups, while predatory protists were the main functional groups that were affected by nitrogen fertilizers. Random forest analysis showed that most of the fertilizer-affected protists were predators, among which Cercozoa was the most affected taxa. In conclusion, our results provide important insights into the impact of nitrogen fertilizers on soil protist communities.

● Conservation tillage increases soil microarthropod abundance at the global scale.

Conservation tillage is crucial for preserving soil structure and fertility. However, the effects of no tillage on the abundance of soil microarthropods (Acari and Collembola) remain unclear, with contrasting results reported. To assess the global impact of no tillage, we compiled a data set consisting of 59 publications, from which we extracted 167 observations for microarthropod abundance, 193 observations for Acari abundance, and 176 observations for Collembola abundance. Our findings revealed significant increases in soil microarthropods (27.1%), Acari (22.1%), and Collembola (32.3%) compared to conventional tillage under no tillage. The impact varied with soil texture, precipitation, and soil nutrient availability. Furthermore, to assess the impact of reduced tillage, we extracted 46 observations for microarthropod abundance, 64 observations for Acari abundance, and 27 observations for Collembola abundance. Reduced tillage also showed positive effects, with a 28.4% increase in soil microarthropods and a 53.7% increase in Acari compared to conventional tillage. Our research demonstrates the beneficial effects of no tillage and reduced tillage on soil microarthropod abundance. However, the positive effect of conservation tillage on soil microarthropods differed in magnitude Collembola and Acari. Conservation tillage should be encouraged, particularly in regions with poor soil nutrients and high precipitation, to prevent further decline in soil microarthropod abundance.

● A new COX1 primer for soil nematode metabarcoding was designed, and this primer outperforms other commonly used COX1 primer pairs in species recovery and quantity of PCR products.

Microscopic nematodes play important roles in soil ecosystems and often serve as bioindicators of soil health. The identification of soil nematodes is often difficult due to their limited diagnostic characters and high phenotypic plasticity. DNA barcoding and metabarcoding techniques are promising but lack universal primers, especially for mitochondrial COX1 gene. In this study a degenerated COX1 forward primer COIFGED was developed. The primer pair (COIFGED/JB5GED) outperforms other four commonly used COX1 primer pairs in species recovery and quantity of polymerase chain reaction (PCR) products. In metabarcoding analysis, the reads obtained from the new primer pair had the highest sequencing saturation threshold and amplicon sequence variant (ASV) diversity in comparison to other COX1 as well as 18S rRNA primers. The annotation of ASVs suggested the new primer pair initially recovered 9 and 6 out of 25 genera from mock communities, respectively, outperformed other COX1 primers, but underperformed the widely used 18S NF1/18Sr2b primers (16 out of 25 genera). By supplementing the COX1 database with our reference sequences, we recovered an additional 6 mock community species bringing the tally closer to that obtained with 18S primers. In summary, our newly designed COX1 primers significantly improved species recovery and thus can be supplementary or alternative to the conventional 18S metabarcoding.

● The nitrogen (N) and phosphorus (P) addition promotes the abundance of soybean soil nematodes.

With global warming, the increasing of industrial and agricultural activities and demand for fossil fuels, large amounts of nitrogen and phosphorus compounds are released into the atmosphere, resulting in an annual increase in nitrogen and phosphorus deposition. The nematodes, as one of the main functional groups of soil organisms, occupy multiple trophic levels in soil detritus food networks. However, few studies on the effects of nitrogen and phosphorus on soil nematodes, and the results are uncertain. This experiment was conducted in soybean farmland and four treatments included control, nitrogen addition, phosphorus addition, and N + P addition. The results showed that both phosphorus and N + P addition significantly increased the abundance of soil nematodes, but that had no effects on soil nematodes richness. Redundancy analysis showed that nitrate nitrogen, soil moisture content, and pH were environmental factors driving different dietary changes in soil nematode communities. The effect of phosphorus addition on the abundance of nematode communities mainly affects ammonium nitrogen. Our findings revealed that nitrogen addition when phosphate fertilizer is added to soybean farmland will have a certain positive effect on the soil underground food web, which provides a basis for better explaining the effect of nitrogen and phosphorus addition on soybean farmland.

● The unique gut habitat led to a core intestinal microbiome in diverse soil ecosystems.

Soil invertebrates are widely distributed in the ecosystem and are essential for soil ecological processes. Invertebrate gut microbiome plays an important role in host health and has been considered as a hidden microbial repository. However, little is known about how gut microbiome in soil invertebrates respond to diverse soil ecosystems. Based on a laboratory microcosm experiment, we characterized the assembling of microbiome of soil collembolans (Folsomia candida) from six representative regions of the soil ecosystem which they inhabit. Results showed that collembolan gut microbial communities differed significantly from their surrounding soil microbial communities. A dominant core gut microbiome was identified in gut habitat. Community analyses indicated that deterministic process dominated in the community assembly of collembolan gut microbiome. The results further demonstrate a dominant contribution of host selection in shaping gut microbiome. It is also worthy to mention that pathogens, such as common agricultural phytopathogenic fungi Fusarium, were involved in core microbiome, indicating that collembolans could act as vectors of pathogens. Our results unravelled the existence of gut core microbiome of collembolans in soil ecosystems and provided new insights for understanding the crucial role of gut microbiome of soil fauna in maintaining microbial biodiversity and stability of soil ecosystems.

● Nematode identification serves as an important parameter to study their behaviour, importance and pathogenicity.

Nematodes constitute most diverse and least studied group of soil inhabiting invertebrates. They are ecologically and physiologically important, however, wide range of nematodes show harmful impact on the individuals that live within their vicinity. Plant parasitic nematodes (PPNs) are transparent, pseudocoelomate, free living or parasitic microorganisms. PPNs lack morphometric identification methods due to insufficient knowledge on morphological variations among closely related taxa. As such, molecular approaches such as DNA and protein-based information, microarray, probing, sequence-based methods and others have been used to supplement morphology-based methods for their identification. To invade the defense response of different plant species, parasitic nematodes have evolved different molecular strategies. Ascarosides and certain protein-based nematode-associated molecular patterns (NAMPs), can be perceived by the host plants, and can initiate a signaling cascade. To overcome the host confrontation and develop certain nematode feeding sites, some members can inject effectors into the cells of susceptible hosts to reprogram the basal resistance signaling. This review primarily emphasizes on an updated account of different classical and modern tools used for the identification of PPNs. Besides we also summarize the mechanism of some important signaling pathways which are involved in the different plant nematode interactions.

● Nematode abundance and footprint show unimodal patterns with precipitation levels.

Precipitation plays a crucial role in global biodiversity change across terrestrial ecosystems. Precipitation is proven to affect soil organism diversity in natural ecosystems. However, how precipitation change affects the function of the soil nematode community remains unclear in cropland ecosystems. Here, we tested soil nematode communities from different precipitation sites (300 mm to 900 mm) of the agricultural ecosystem. The abundance of total nematodes, fungivores, and plant parasites, together with the footprint of fungivores was significantly affected by mean annual precipitation (MAP) in cropland ecosystem. Plant parasites diversity and footprint showed negative relationships with MAP. The random forest suggested plant parasite footprint was the most responsive to MAP. The structural equation model revealed that MAP affected nematode abundance and footprint indirectly via soil pH; nematode diversity was affected by MAP directly. We conclude that precipitation could act as the main selection stress for nematode diversity among the large gradient of agricultural ecosystems. However, the soil pH may act as a stress factor in determining nematode community and carbon flow in the soil food web. Our study emphasized that using nematode value by trophic group would provide a deep understanding of nematode response to precipitation in cropland ecosystems.

● Impact of marshy area reclamation by various vegetations on soil nematode community was investigated.

Marshy areas are ecologically important and sensitive areas which are under immense pressure, such as reclamation by various terrestrial vegetations. However, how these vegetation types disrupt the stability of nematode community is scarce. The present study determined how the soil nematode community responded to shifting environmental states by using nematode abundances, nematode indices and metabolic footprints as indicators. In this context, we selected three types of reclaimed vegetation around a marshy land (MR) in Dachigam National Park, Kashmir, which includes grassland (GL), forest (FR) and cropland (CL) to investigate the soil nematode community. Acrobeloides, Plectus, Eudorylaimus, and Aphelenchus proved more sensitive to reclamation effect. Results revealed decrease in total nematode and bacterivore abundance. Reclamation reduced diversity in CL, whereas no effect was observed in the GL and FR as compared to MR. Channel index indicated shift from fungal decomposition to bacterial decomposition pathway in GL. The nematode faunal profile depicted grassland (GL) as the most structured ecosystem compared to MR, FR, and CL. Our results suggest that vegetation type regulates the structure, function, and stability of the soil food web, which has significant implications for managing the vegetation cover in a sustainable manner in the Dachigam National Park.

● Soil penetration resistance increases as a result of park reconstruction.

This study is based on a park in an industrial city in Ukraine. In 2019, a 2.8 ha area of the park was reconstructed. The park’s reconstruction aimed to create a comfortable environment for visitors and to improve the efficiency of ecosystem services, and thereby enhance the quality of life of citizens. The reconstruction of the park was found to cause changes in the physical properties of soils and the structure of the soil macrofauna community. The increases of soil compaction in the layers at depth 5–20 cm and the soil electrical conductivity were a consequence of technological operations during reconstruction. The park reconstruction activities can also explain 29% of the variation in the soil macrofauna community. Extracting the variation induced by the park reconstruction from the community variation induced by other causes was a major challenge. The specific changes in the community of soil macrofauna following the reconstruction of the park were revealed. The abundance of soil animal species A. rosea, A. trapezoides, H. affinis, H. rufipes, B. affinis was found to increase after the reconstruction. The earthworm A. trapezoides decreased in abundance due to the park reconstruction.

● Different primers will affect nematode annotation at different taxonomic levels.

High-throughput sequencing technology is increasingly used in the study of nematode biodiversity. However, the annotation difference of commonly used primers and reference databases on nematode community is still unclear. We compared two pairs of primers (3NDf/C_1132rmod, NF1F/18Sr2bR) and three databases (NT_v20200604, SILVA138/18s Eukaryota and PR2_v4.5 databases) on the determination of nematode community from four different vegetation types in Changbai Mountain, including mixed broadleaf-conifer forest, dark coniferous forest, betula ermanii Cham and alpine tundra. Our results showed that the selection of different primers and databases influenced the annotation of nematode taxa, but the diversity of nematode community showed consistent pattern among different vegetation types. Our findings emphasize that it is necessary to select appropriate primer and database according to the target taxonomic level. The difference in primers will affect the result of nematode taxa at different classification levels, so sequencing analysis cannot be used for comparison with studies using different primers. In terms of annotation effect in this study, 3NDf/C_1132rmod primers with NT_v20200604 database could provide more information than other combinations at the genus or species levels.

● Strong associations among soil-wood feeders and fungus growers were observed.

The community composition and activity-density of termites can influence nutrient cycling and other ecological functions. However, the spatial distribution and the activity-density of termites on a fine-scale in tropical forests are still unknown. We checked the spatial distribution patterns of the feeding groups and species of termites and their co-occurrence pattern in a 1-ha (100 m × 100 m) plot, and their correlation with the environmental factors. We used a standard protocol to collect termite assemblages and classified them into five feeding groups based on their preferred diet: fungus growers, litter feeders, soil feeders, soil-wood feeders, and wood feeders. We measured the environmental factors: soil pH, litter mass, aboveground plant biomass, and topographic position index (TPI). Soil-wood feeders showed the highest activity-density, followed by wood feeders, fungus growers, soil feeders, and litter feeders. Soil-wood feeders and fungus growers demonstated a strong correlation while litter feeders showed weak correlations with other feeding groups. Termite feeding groups and most of the termite species displayed a positive association with the high TPI and the low soil pH patches. Our results indicated that the examined environmental factors influenced the termite community assemblages and distribution patterns on a fine-scale in tropical rainforests.

• Fertilizer increased soil nematode abundance and decreased the ecological index of soil nematode community.

Both fertilizer and plant species richness may affect the soil nematode community. However, the influence of fertilizer and weed species richness interaction is unclear. Nematode abundance and biodiversity in wheat and weed plots soil treated with nitrogen, phosphate and potassium fertilizer addition and weed species richness (0, 1, 2 and 4 weed levels) were investigated in a long-term microcosm experiment established in 2010 at Kaifeng, China. The results demonstrated that fertilizer treatment increased the abundance of total nematode, bacterivores, and plant parasites whereas it decreased the total genera number, the Shannon–Wiener diversity index (H′), Margalef richness index (SR), the total maturity index (∑MI), and structure index (SI), and degraded the structure of the nematode community. In contrast, weed species richness increased these ecological indices and enhanced the structure of the nematode community. Principal component analysis (PCA) indicated that the fertilizer's effect was more significant than weed species richness. Redundancy analysis demonstrated that fertilizer affected soil nematode mainly through increasing soil available phosphorus by 4.71 times and ammonium nitrogen content by 74.03%; weed species richness increased the diversity indices of soil nematode mainly through enhancing soil moisture by 2.07%. Our results suggest weed species richness may relieve the negative effect of fertilizer on the diversity of soil nematode community.

Ÿ 24 differentially expressed proteins (DEPs) were identified by proteomic method.

Arsenic (As) is broadly distributed due to natural and anthropogenic sources, and it is toxic to organisms. This study aimed to investigate the proteomic response in earthworm exposed to As³⁺ . Earthworms were exposed to As³⁺ in soil at 5–80 mg kg^–1, and samples were collected after 60 days exposure. Two-dimensional electrophoresis (2-DE) was used to separate the proteins in earthworm homogenate, then differentially expressed proteins (DEPs) were identified using MALDI-TOF/TOF-MS analysis. After 2-DE, 36 DEPs were found and 24 of them were successfully identified. 79.2% of DEPs were upregulated compared to the control group. The maximum fold change reached 53.8 in spot 3108 in the 80 mg kg^–1 As group. Two proteins were not found in the control group but found in the As treated groups. Proteins were grouped into metabolism, signal transduction, stress-related, transport, regulation, and predicted/hypothetical protein categories based on their function. The protein–protein interaction between the DEPs indicated that serum albumin (ALB) is very important, related to 6 other proteins. Proteins were then verified by western blot, the results were in agreement with the proteomic analyses. The identification of induced or repressed proteins because of As³⁺ in earthworms is helpful to explore the underlying mechanisms of soil arsenic ecotoxicity.

• To summarize the utilities of the ecological features based on community structure of the soil ciliates for assessing the ecological restoration quality in grain for green.

A 1-year baseline survey was conducted in north-western China to evaluate the ecological restoration quality of grain for green (GFG) using soil ciliate communities. The aims of this study were focused on analyzing the changes of soil ciliate communities in four plots (A, GFG for 15 years; B, GFG for 13 years; C, layland; D, cultivated land) for GFG environmental assessment. Simultaneously we studied the effects of vegetation communities and physical-chemical variables with GFG changes on soil ciliates. A total of 114 species of ciliates were identified among the four sample sites, representing nine classes, 14 orders, 22 families and 37 genera. The community patterns of the soil ciliates were significantly correlated with the individual abundance of aboveground plants, soil water content, and soil porosity. The contents of total nitrogen were the main factor affecting the soil ciliate community composition. The species number, individual abundance, and diversity index of the ciliates was each in the order A>B>C>D; that is, the community composition of ciliates was complicated with the implementation of the GFG. It was shown that succession of ciliate community shift toward promoting the complexity with the progress of GFG. These findings demonstrate that soil ciliate communities may be used as a useful indicator to evaluate the effects of the ecological restoration quality of GFG.

• This study discovered the direct responses of soil fauna to acid deposition.

Excessive acid deposition causes soil acidification and changes the soil microhabitat, affecting the survival and reproduction of soil organisms. Folsomia candida (Collembola, Isotomidae) is used internationally as a model organism for assessing chemical toxicity in soil and it is feasible to use its avoidance response as an indicator of environmental changes as well. In this study, we used Folsomia candida avoidance behavior to assess the risks of acid deposition on soil ecosystems. Different pH (3.0, 3.5, 4.0, 4.5, 5.0, and 5.5) treatments were set up in petri dish experiments, and the avoidance behavior of Folsomia candida was measured after 12, 24, and 48 h of exposure to the pH conditions. The results indicated that (1) both the exposure duration and pH level influenced collembolan avoidance behavior. (2) After 12 h exposure, most of the insects showed avoidance behavior but without significant differences among the treatment conditions. (3) After 24 h exposure, significant avoidance behavior was observed at pH 3.0, 3.5, and 4.0. (4) After 48 h exposure, avoidance behavior was seen in all treatment conditions except for pH 5.5. This study described the direct responses of soil fauna to acid deposition and indicated that both pH and length of exposure interacted to influence the avoidance behavior of Folsomia candida. During the experimental period, the insects reacted negatively and show consistent avoidance behavior at pH 3.0, 3.5, and 4.0. Reversed avoidance behavior was apparent between pH 4.5 and 5.0 and not observed at pH 5.5, indicating that the latter was the preferred pH environment.

• We experimentally reduced litter and root inputs in forests at different latitudes.

The relative abundance of different components of the soil food web can vary tremendously in response to plant resource inputs. However, little is known about the mechanisms that plant resource regulate the energy fluxes and soil community composition. Here, we experimentally reduced litter and root inputs for two years in China at low-, mid-, and high-latitude forests to explore the effects of plant-derived resource inputs on the nematode energy flux and community composition. Litter reduction at high and mid latitudes and root removal at low latitudes reduced nematode richness but did not alter nematode abundance. Besides, Litter reduction reduced energy fluxes of bacterial-feeding nematodes at mid latitudes and energy fluxes of plant-feeding, bacterial-feeding and omnivorous-predatory nematodes at low latitudes, thus reducing the energy fluxes of total nematodes in mid- and low-latitude forests. By contrast, root removal reduced energy fluxes and relative energy flux of plant-feeding nematodes in high- and low-latitude forests. In most cases, nematode diversity in different trophic groups increased with increasing energy flux to nematodes. Taken together, our results suggest that the effects of plant resource inputs on nematode energy flux are affected by climate and plant resource type, which improves our understanding of plant-soil interactions.

Soil nematodes are the most numerous components of the soil fauna in terrestrial ecosystems. The occurrence and abundance of nematode trophic groups determine the structure and function of soil food webs. However, little is known about how nitrogen deposition and land-use practice (e.g. mowing) affect soil nematode communities. We investigated the main and interactive effects of nitrogen addition and mowing on soil nematode diversity and biomass carbon in nematode trophic groups in a temperate steppe in northern China. Nitrogen addition and mowing significantly decreased the abundance of soil nematodes and trophic diversity but had no effects on nematode richness and the Shannon-Wiener diversity. Nitrogen addition influenced soil nematode communities through decreasing soil pH. Mowing influenced soil nematode communities through decreasing soil moisture. Nitrogen addition enhanced the bacterial energy channel but mowing promoted fungal energy channel in the soil micro-food web. Our study emphasizes that ecosystem function supported by soil organisms can be greatly influenced by nitrogen deposition, and mowing cannot mitigate the negative effects of nitrogen deposition on soil food webs.

•Ÿ A one-sided negative relationship existed between tunneling beetles and earthworms.

Interspecific interactions between two spatiotemporally co-occurred species sharing a single resource are considered to be either competitive or facilitative. This study examined the possible interspecific interactions between a dung-tunneling beetle species (Onthophagus yubarinus) and an earthworm species (Aporrectodea nocturna), two major detritivores responsible for dung removal in a Tibetan alpine meadow. We conducted a two-way, factorial field experiment using replicated chambers, and measured the performances of beetles and earthworms, as well as yak dung removal, soil properties and aboveground plant biomass over two months. Earthworm presence significantly decreased the body size of beetle larvae and the weight of tunnel dung that beetle larvae live on. In contrast, beetle presence did not affect the performance of earthworms. Beetles, earthworms and their interaction significantly increased dung removal and soil organic carbon concentration at the end of the experiment. Beetles alone significantly increased soil total N and P, soluble N and P concentrations, but earthworms alone had nonsignificant effects on these nutrient variables. Beetles and earthworms additively enhanced soluble N and P concentrations, and aboveground plant biomass at the end of the experiment. These results indicate 1) there was a one-sided negative relationship between dung-tunneling beetles and earthworms, resulting from the consumption of earthworms on food resource of beetle larvae; and 2) the coexistence of beetles and earthworms facilitated dung removal interactively and plant growth additively by increasing nutrient availability.

•Ÿ Earthworms increased soil macroaggregate (>2 mm and 0.25–2 mm) formation

As soil ecosystem engineers, earthworms are the main promoters of soil aggregation, a process that drives the production of ecosystem services by soils. A crucial factor in the ecosystem service of carbon sequestration is rhizodeposit carbon, which is the main energy source of soil food webs. The effects of earthworms on the distribution of rhizodeposit-carbon in soil aggregates remain unclear. Here, we conducted a ¹³CO₂ labeling experiment to determine the effects of earthworms on maize rhizodeposit carbon in soil aggregates after 14 years (2002–2016), in both conventional tillage (CT) and conservation tillage (no tillage, NT) soils. Four treatments were established in total: NTE (no tillage soil with earthworms), CTE (conventional tillage soil with earthworms), NTC (control, no tillage soil without earthworms), and CTC (control, conventional tillage soil without earthworms). Earthworms significantly enhanced the abundance of soil macroaggregates (>2000 μm and 250–2000 μm) on day 30 compared with day 2 (after labeling), especially in the NT soils. On day 30, in the presence of earthworms, the amounts of rhizodeposit carbon in the>2000 μm and 250–2000 μm soil aggregates in the NT soils were significantly higher than in those in the CT soils (P<0.05), and higher d¹³C signatures in the same size aggregates were observed in the NT soils than in the CT soils (P<0.05). These findings indicated that compared with the CT soils, with the involvement of earthworm activity, the NT soils promoted more rhizodeposit carbon transformation to the soil macroaggregates. Our results clearly indicate that soil macroaggregates formed in different tillage soils in the presence of 2 different engineers (earthworms and roots) significantly differ from those formed in the presence of only one organism (roots) in the long term.

•Relationships between environmental factors and nematode distributions at different spatial scales are assessed.

Understanding biodiversity and biogeographic distribution of soil fauna is an important topic in ecology. While nematode communities have been compared among ecosystems, knowledge remains limited about how environmental factors and nematode distributions are linked at different spatial scales. Here, we employed high-throughput sequencing to compare nematode communities in tropical (Xishuangbanna), subtropical (Ailaoshan), and cold temperate spruce-fir (Lijiang) forest ecosystems with identical spatial sampling. Relationships between nematode communities and environmental factors were analyzed using redundancy analysis (RDA). Our results showed that nematode richness and diversity peaked in Xishuangbanna; however, no significant differences were observed in other two forest ecosystems. Bacterial feeders and Omnivores / Carnivores (Om & Ca) had the lowest relative abundance, but the highest diversity, in Xishuangbanna, with the opposite pattern being detected for fungal and plant feeders. Our data also demonstrated that, for forest ecosystems, climate factors drive nematode communities distributions at the regional scale, while terrain and soil characteristics (including pH and nutrients) drive nematode communities distributions at local scales. This study improves our current understanding of key factors (environmental parameters) responsible for the biogeographical distribution of forest nematode communities at different spatial scales.

• Nematodes was investigated in a young Acacia crassicapa plantation in southern China

Aboveground litter inputs and root exudates provide basal resources for soil communities, however, their relative contributions to soil food web are still not well understood. Here, we conducted a field manipulative experiment to differentiate the effects of litter inputs and living root on nematode community composition of surface and subsoils in a young Acacia crassicapa plantation in southern China. Our results showed that both litter addition and root presence significantly enhanced soil nematode abundance by 17.3% and 35.3%, respectively. Litter addition altered nematode trophic group composition, decreased fungivore to bacterivore ratio, and enhanced maturity index and structure index, which led to a bacterial-based energy channel and a more complex food web structure. However, root presence had a limited impact on the nematode community composition and ecological indices. Despite nematodes surface assembly, soil depth did not affect nematode trophic group composition or ecological index. Our findings highlight the importance of litter inputs in shaping soil nematode community structure and regulating soil energy channel.