The old acidophilous oak forest Natura 2000 habitat (H9190) in the Netherlands is rapidly deteriorating in quality due to excess nitrogen deposition, evidenced by soil acidification, leaching of base cations, and an accumulation of soil organic matter. The accumulation of organic matter suggests disruption of the decomposition process, which is driven by the interplay between fungi and microarthropods. To better understand the current role of microarthropods for decomposition and changes therein during the process of deterioration, we analyzed microarthropod communities in old oak forests and compared them to data from other forest sites from the same geographical area and a similar habitat, collected in 1994 and resampled in 2023. Relative to the reference data, we observed reductions in both abundance and species richness of microarthropods. When analyzing the data by feeding guild we found that these reductions are especially pronounced for fungivorous mites. Similar declines were found during the resampling of the reference sites. We hypothesize that nitrogen-driven declines in ectomycorrhizal fungal diversity, which are known from literature, negatively affect fungivorous mite communities, which is expected to contribute to slower decomposition and the accumulation of organic matter. Soil conditions in these oak forests are characterized by low soil pH, while oak leaves are characterized by imbalanced nutrient ratios, contributing to strong reductions in oak vitality. Restoration of these forests starts at the root of the problem, improving soil conditions and fungal diversity and abundance. Our research shows that effective restoration will also require enhancing fungivorous mite populations, potentially through soil inoculation.
Dung from cattle treated with veterinary medicines may contain residues with adverse effects on soil mesofauna dwelling below the pat. This phenomenon has been reported with use of the parasiticide ivermectin, but has not been examined for other parasiticides or for antibiotics. Here, we examined the response of eight mesofauna taxa in soil not covered by dung (bare soil), or in soil below dung from untreated cattle or from cattle treated with the antibiotic chlortetracycline (CTC), the parasiticide eprinomectin (EPM) or both EPM+CTC. Experiments were conducted on native grassland in southern Alberta, Canada in 2019 and 2020 with soil samples taken 1, 2, 4 or 8 weeks after placement of pats. Compared to bare soil, control dung generally increased numbers of mesofauna with significant increases observed for collembolans and mites (Acaridae, Mesostigmata, other Prostigmata). However, more oribatid and tydeid mites were recovered from bare soil. Significant effects of faecal residues were detected in only two cases. In 2019, fewer mesostigmatid mites and unidentified prostigmatid mites were recovered from soil beneath EPM+CTC dung compared to control dung. Our overall findings are consistent with and expand upon the small body of previous studies reporting on the toxicity of faecal residues in dung of cattle treated with macrocyclic lactone parasiticides (e.g., ivermectin, eprinomectin). Results reported here are part of a larger study using the same animals and dung collections that collectively examine the non-target effects of CTC and EPM treatments to cattle on rumen and faecal bacteria, on dung-breeding insects, on soil bacterial and fungal microbiomes, and soil mesofauna (current paper).
The quality of exogenous substrates has strong influences on the direction and magnitude of soil priming effect (PE). However,the different effects of PE induced by the molecular-structure complexity and carbon-to‑nitrogen (C:N) stoichiometry of exogenous substrates remain poorly understood, particularly regarding how the regulating mechanisms shift with the changes in edaphic factors. Here, we conducted an incubation experiment to compare the effects of exogenous substrate complexity (glucose vs. cellulose) and C:N stoichiometry (non-N, low and high C:N) on the priming effect over 110 days. Distinct temporal dynamics of priming effect measured as instantaneous rate of CO2 emission (PEr) were observed between glucose and cellulose additions, whereas similar trends occurred across C:N stoichiometry. Moreover, cumulative priming effect (PEcum) was significantly co-regulated by exogenous substrate complexity and C:N stoichiometry. In the early stage (0–25 days), glucose addition prompted greater PEcum than cellulose under non-N and high C:N, whereas the patterns were reversed under low C:N. In the later stage (25–110 days), cellulose addition consistently produced greater magnitude of PEcum than glucose across C:N stoichiometry. Moreover, low C:N increased the glucose-induced PEcum, whereas sole cellulose addition had higher PEcum than cellulose combined with N. Structural equation modeling (SEM) revealed a direct effect of soil microbial necromass on PEcum during the early stage, whereas soil enzyme activity exerted a stronger direct positive effect during the later stage. Our findings highlight that exogenous substrate complexity and C:N stoichiometry co- regulate soil priming effect, showing temporal dynamics and varied mechanistic pathways of edaphic factors at different incubation stage.
Weed management is essential for crop production but may also influence belowground biodiversity. We compared the effects of three weed management practices on soil fauna communities in a maize field in southwestern China: natural weed growth (CK), weed removal with residue retention (WR), and plastic mulching (PM). A field experiment with seven replicates was established. Results showed that both WR and PM significantly reduced soil fauna abundance, Hill q = 0 (species richness), Hill q = 1 (exp Shannon), and Hill q = 2 (1/Simpson) compared with CK, with the strongest reductions observed under PM. Soil fauna community composition also differed significantly among treatments (p < 0.05). SIMPER analysis identified Prostigmata, Astigmata, and Entomobryomorpha as the main contributors to treatment dissimilarity. These results indicate that natural weed cover supports more diverse and abundant soil fauna communities, whereas weed removal and especially plastic mulching simplify soil fauna assemblages in maize cropland. Our findings suggest that intensive weed management may involve belowground biodiversity trade-offs.
The continuous increase in atmospheric nitrogen deposition significantly affects nutrient cycling in China's dryland ecosystems, particularly soil and microbial carbon–nitrogen stoichiometry, which is closely linked to soil carbon pool stability and long-term carbon sequestration. However, a systematic understanding remains limited regarding whether nitrogen deposition induces cumulative and lagged changes in soil–microbial carbon–nitrogen coupling in drylands. This study integrated 598 experimental datasets from 70 publications across dryland ecosystems to analyze the response characteristics of soil SOC/TN and microbial MBC/MBN to nitrogen input intensity, duration, and environmental factors. Results indicate that nitrogen deposition significantly reduces SOC/TN, with the greatest decline in the topsoil (0–20 cm), and a weakening effect with increasing soil depth. In contrast, MBC/MBN generally increases, suggesting that nitrogen inputs may alleviate microbial nitrogen limitation and promote relative microbial carbon accumulation. Responses differed among ecosystems, with sandy soils exhibiting the greatest magnitude of change. Structural equation modeling further indicated that nitrogen deposition is associated with soil–microbial carbon–nitrogen coupling through changes in soil acidity, carbon fractions, and nitrogen fractions. This study highlights the potential long-term impacts of nitrogen deposition on carbon–nitrogen cycling and soil carbon stability in drylands, providing a theoretical basis for assessing dryland carbon sink functions under future nitrogen deposition scenarios.
Detritivorous macrofauna play a key role in litter decomposition through litter consumption and the breakdown of organic matter. Species may differ in the way they influence the decomposition process due to variations in their life history traits creating an important functional diversity which remain poorly explored in tropical ecosystems. Furthermore, most feeding experiments investigating this process are conducted in microcosms without soil. However, this can alter the environment and the availability of nutrients for the fauna, and in turn inducing contrasting responses to the presence of soil challenging the accuracy of consumption rate estimates. We investigate these questions by comparing feeding performances of 19 tropical species, representing four taxonomic classes (i.e. diplopods, isopods, gastropods and earthworms) through monospecific microcosm experiments, with and without soil, measuring specific litter consumption rate and assimilation efficiency. Without soil, our results show specific litter consumption rate ranging between 7.1 ± 1.0 mg/g/day for the snail Pleurodonte discolor and 383 ± 79.6 mg/g/day for a woodlice species (Thrichorhina sp). We showed that there was a link between specific litter consumption without soil and macrofauna fresh biomass which is class-specific and strongly dependent on the presence of soil. In addition, detritivorous macrofauna tend to compensate for their consumption by having a higher specific litter consumption when soil was not available questioning methods usually used for estimating this important feeding parameter. On average, assimilation efficiency of gastropods (71%) and isopods (70%) was higher than diplopods (18%), however there was a strong intra-class variability with species having very contrasted feeding strategies within a same class especially for diplopods. Measuring feeding performances for a large number of detritivorous macrofauna allowed us to bring an important brightening on the functional diversity of these species often classified into a single functional group “litter-transformers”.
Free-living nematodes are sensitive indicators of soil food-web structure and long-term management effects. While contrasts between continuous no-till (NT) and conventional tillage are well documented, far less is known about how periodic tillage embedded within long-term NT systems influences nematode communities. This study evaluated nematode community indices and composition in a 50-year field experiment comparing moldboard plow (MP), chisel-disk (CD), alternate tillage (2-yr NT followed by 1-yr MP; AT), and continuous NT. Maturity Index (MI), Modified Maturity Index (MI 2–5), and summed Maturity Index (ΣMI) were highest under NT and lowest under MP. Values for AT fell within the range of NT and MP for MI and ΣMI, while MI(2–5) values under AT overlapped with those observed under MP and CD. Enrichment index (EI) and plant parasitic index (PPI) were unaffected by tillage, suggesting that observed treatment effects primarily reflected long-term food-web structure rather than short-term nutrient responses. Although PERMANOVA did not detect a significant tillage effect, non-metric multidimensional scaling (NMDS) revealed a clear disturbance gradient, with AT positioned between NT and MP, consistent with persistent biological legacy effects. Lack of differences between NT, AT, and CD indicates that a combination of disturbance frequency and intensity (MP) governs long-term nematode community organization, and that periodic tillage can modify, but not fully reset, soil food-web structure within predominantly NT systems.
Introducing nitrogen (N)-fixing trees into monoculture plantations is a promising strategy for enhancing soil organic carbon (SOC) sequestration. This study aimed to elucidate the mixed plantations-mediated mechanisms that drive SOC stabilization in such systems. We compared pure Eucalyptus plantations (PP) with mixed Eucalyptus & times; Dalbergia odorifera plantations (MP) in Pingxiang City, Guangxi Zhuang Autonomous Region, China, by analyzing rhizosphere and bulk soils for a suite of parameters, including SOC fractions, microbial community structure assessed by phospholipid fatty acid analysis, microbial necromass carbon, and Fe/Al oxides. Results showed that MP significantly increased the proportion of mineral-associated organic carbon (MAOC) and decreased the particulate organic carbon (POC):MAOC ratio, indicating a shift toward more stable SOC. The rhizosphere in MP stimulated microbial activity and necromass accumulation, contributing substantially to MAOC. Concurrently, elevated Fe and Al oxides in the rhizosphere further promoted MAOC formation. Redundancy analysis identified these interconnected microbial and mineralogical pathways as key drivers. NMDS and PERMANOVA revealed revealed that species mixing directly drives C sequestration and amplifies it through rhizosphere-mediated effects, with a significant interaction between mixing and rhizosphere presence. We conclude that integrating N-fixing trees enhances SOC sequestration by shifting storage toward a more durable, mineral-stabilized form. Underpinning this enhancement are interconnected microbial and mineralogical mechanisms, which operate through two synergistic pathways: the intrinsic advantages of species mixing and the intensification of rhizosphere effects. This mechanistic framework provides a foundation for designing mixed plantations aimed at long-term C sequestration.
Vegetation restoration is an effective way to prevent soil degradation and promote soil organic carbon (SOC) accumulation. However, research on changes in SOC, soil heterotrophic respiration (Rh), and the underlying mechanisms in response to vegetation restoration in fragile karst ecosystems is still deficient. In this study, we investigated the effects of converting cropland (maize field) to forest and grassland on SOC, Rh, soil microbial communities, other soil properties, and their relationships in the karst area of Southwest China. Total nitrogen, available nitrogen, microbial biomass carbon, and microbial biomass nitrogen did not differ between forest and grassland, but were significantly higher than in the maize field. Bulk density and clay decreased, and sand increased in the grassland compared to the maize field. At the phylum level, for bacteria, the relative abundance of Chloroflexi declined, and that of Actinobacteriota increased in both forest and grassland compared with the maize field. Meanwhile, for fungi, the relative abundance of Mortierellomycota decreased, and that of Basidiomycota increased in the forest compared to the maize field. In correlation networks, for bacteria, total links, density, and average degree were highest in the maize field, followed by the grassland, and lowest in the forest. In contrast, for fungi, total nodes, total links, density, and average degree were higher in the forest than in the maize field. SOC was similar between forest and grassland, but was higher than in the maize field. Rh was highest in the grassland, followed by the forest, and lowest in the maize field. SOC and Rh were significantly correlated with soil microbial communities and other soil properties based on the Mantel test. Accordingly, the results indicated that SOC accumulation occurred simultaneously with increased Rh, and that both SOC and Rh were significantly influenced by soil microbial communities and other soil properties after vegetation restoration. Therefore, the study provides an important reference for preventing soil degradation and promoting SOC accumulation in fragile karst ecosystems.
Large ungulates are the key drivers of forest ecosystems, yet research has mainly focused on browsing. Their influence through carrion inputs on soil microbial litter decomposition, a critical pathway in carbon cycling, remains poorly understood. To address this gap, we conducted manipulation experiments in temperate forests of central Japan to evaluate how carrion of Japanese sika deer (Cervus nippon) influences potential soil microbial litter decomposition. We used BIOLOG EcoPlate assays to assess soil microbial multifunctionality (MF) and functional composition (FC), and examined how these responses were modulated by forest type (natural vs. plantation), the presence of insect scavengers (carrion beetles, Silphidae spp.), and interannual variation in precipitation. The results showed that deer carrion placement significantly increased the MF of soil microbial litter decomposition. However, the magnitude and direction of the effects varied between natural and plantation forests and shifted across years, likely reflecting nutrient availability and precipitation-driven differences in carrion desiccation. Insect exclusion experiments revealed that carrion beetles suppress MF across multiple substrate groups, probably because of antimicrobial secretions, whereas their effects on FC are limited. These results demonstrate that deer carrion act as strong nutrient inputs that stimulate potential soil microbial litter decomposition; however, their effects are highly context-dependent. Our study highlights a previously overlooked pathway through which large ungulates influence forest carbon emissions and underscores the need to incorporate the contribution of carrion to forest carbon emissions mediated by soil microbial communities, along with browsing, into models of forest carbon cycling.
Preserving soil health is essential for sustaining ecosystem functions and human well-being, yet it is increasingly challenged by intensive agricultural practices. In Nonthaburi Province, Thailand, smallholder farmers produce premium-quality Monthong durian (Durio zibethinus L.) in raised-bed orchards using diverse management strategies whose impacts on soil health remain poorly understood. Therefore, this study assessed how contrasting management practices affect soil physicochemical properties, biodiversity and functioning. Thirty-two farmers were interviewed to characterize management diversity, with their orchards grouped into three clusters based on fertilizer and irrigation regimes: C1 (high organic fertilizer and tap water), C2 (high canal water use), and C3 (high mineral fertilizer use). Soil analyses conducted in 15 orchards showed predominantly clay textures and relatively high soil organic carbon levels (3.45–4.31%). Significant differences emerged for available phosphorus and extractable calcium, with Cluster C2 presenting the lowest concentrations. While earthworm biomass did not differ significantly among clusters, bait-lamina testing indicated higher soil biological activity in C1 than in C2 or C3. Overall, the management practices influenced nutrient availability and biological functioning, with the fertilization regimes shaping P, K, and Ca status, while organic amendments enhanced soil biological activity. Analysis of the results highlighted the complementarity of various methods to assess soil health. Furthermore, these findings should contribute to the development of more sustainable soil management strategies to maintain fertility and support long-term durian orchard productivity.
Temperate rainforests along the North American Pacific coast typically have podzolized soils with high acidity and depleted base cations. Low-molecular weight organic acids (LMWOA) play a potentially important role in rainforest soils by enhancing the biotic weathering of minerals for cation release, but whether ectomycorrhizal (EM) fungi and arbuscular (AM) fungi differ in this trait is uncertain. We compare LMWOA concentrations in soils and directly produced from individual root tips by an EM conifer (Picea sitchensis) and AM conifer (Thuja plicata) in a mature field trial. Soil water extracts were dominated by tartaric acid, particularly in the organic horizon, and concentrations were 10-fold higher on average under T. plicata. The effect of tartaric acid on cation availability was highlighted by positive correlations with calcium in soil solution, but at a significantly lower rate of release under T. plicata compared to P. sitchensis. We also found elevated podzolization attributes under T. plicata, with reduced base saturation, lower pH near the soil surface, and greater concentrations of exchangeable aluminum. A short-term laboratory assay of excised roots demonstrated 50% higher production of total LMWOA (primarily formic acid) by distal roots of T. plicata compared to EM fungal colonies. Several findings deserve further investigation, including whether these organic acids protect roots from aluminum toxicity, and the possible role of mycorrhizosphere bacteria in LMWOA production. When considering the ‘whole-tree’ response, we suggest T. plicata, through LMWOA production, is adapted to exploiting the base-poor, podzolized soils of the North American Pacific coast.
The surface area dedicated to grazing activity decreases worldwide, while the biomass of livestock increases, resulting in a high density of herbivores in enclosed pastures with direct impacts on the biodiversity, and on the physical and chemical properties of the soil. Overstocking pastures lead to a decrease in vegetation height and plant diversity, an increase of soil compaction, and an increase of accidental mortality of soil fauna. Dung beetles provide important ecosystem services to animal production by removing feces. While they rely on herbivores dung, they might be victims of high herbivore density. Thus, we define two contradictory hypotheses: either the resource abundance, or the impact of the herbivores on their environment, will limit the abundance of these insects. In this study, a dung beetle community was assessed within zoo enclosures housing different densities of African herbivores fed a standard diet. We set up 66 non-lethal pitfall traps during spring 2023 and 2024. We characterized the habitat at the enclosure scale (vegetation cover and soil compaction), and in a 10-meter buffer surrounding the traps (vegetation cover and feces abundance). We captured 830 dung beetles, belonging to 12 species. Onthophagus vacca (n = 269) and Onthophagus ruficapillus (n = 223) represented more than half of the abundance. In high herbivore density enclosures the surface area of bare ground increased while the vegetation height decreased. The surface area of bare ground at the trap scale had a significant negative effect on abundance and diversity of dung beetles. Despite being resource dependent, we demonstrated that at high densities of herbivores, the dung beetles were impacted by the compaction of soil caused by both trampling and agricultural machinery.
Temperate alley cropping is anticipated to enhance soil fertility and carbon sequestration on croplands, with litter decomposition forming a major pathway for organic matter accumulation. Despite this, alley cropping’s impacts on litter decomposition, and particularly soil faunal contributions to litter decomposition, remain poorly understood. This study evaluated how alley cropping, soil-dwelling fauna, and their interactions influence Phleum pratense decomposition across five arable farms in England, United Kingdom. P. pratense decomposition over 16 weeks was compared between litter bags, with and without holes permitting access to soil meso- and macro-fauna, buried in paired alley-cropping and sole-cropping systems at three locations: in tree rows, the tree row-crop alley interface, and crop alley centres. Alley cropping significantly increased litter decomposition rates, which were 4.8 % ± 1.5 (SE) (p = 0.002) higher in alley-cropping than sole-cropping systems. The effect varied with proximity to tree rows: relative to sole cropping, the increase was 7.2 % ± 1.8 (SE) (p = 0.001) in tree rows, 5.3 % ± 1.8 (SE) (p = 0.010) at the edge of crop alleys, and non-significant in crop alley centres. Soil-dwelling fauna increased litter decomposition by 4.8 % ± 1.0 (SE) (p < 0.001), but faunal-mediated decomposition was unaffected by alley cropping. In contrast, microorganism-mediated litter decomposition was enhanced by 6.4 % ± 2.3 (SE) (p = 0.025) in tree rows and by 6.5 % ± 2.3 (SE) (p = 0.025) at crop alley edges compared to sole cropping. Incorporation of litter-derived carbon and nutrients into soil organic matter could increase carbon sequestration and fertility. However, alley cropping’s impacts are context-dependent, with more research needed to understand under what circumstances alley cropping enhances litter decomposition.
Climate warming is suggested to alter insect parental care behaviors and subsequent offspring development, yet empirical evidence from alpine ecosystems remains limited. We conducted a fully factorial experiment to determine the effects of simulated warming (warmed vs. unwarmed) and substrate type (sandy soil vs. meadow soil) on pre-reproductive tunneling behavior and dung burial in the tunneling dung beetle Geotrupes stercorarius (Linnaeus, 1758) in an alpine meadow of the Tibetan Plateau. Our results revealed that, warming prolonged tunneling duration, increased total tunnel depth, and reduced dung burial weight in both meadow soil and sandy soil, despite of the statically non-significant effects in sandy soil. In addition, dung burial weight was significantly negatively correlated with tunneling duration and total tunnel depth across both substrates. These findings indicate that warming enhances parental care effort in G. stercorarius by increasing tunneling investment independent on substrate types. This study provides empirical evidence for behavioral plasticity in insect parental care, and advances the understanding of adaptive strategies of alpine insects in response to climate warming scenarios.
Ammonia-oxidizing microorganisms, including complete ammonia-oxidizing bacteria (Comammox), play vital roles in nitrogen cycling. However, despite extensive research on the abundance and composition of Comammox in agroecosystems, the rates of ammonia oxidation and their relative contributions to nitrous oxide (N2O) emissions by ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and Comammox remain uncertain, particularly under varying fertilization treatments. Our study investigated the effects of organic and mineral fertilization on the abundance, community composition, and ammonia oxidation rates of AOA, AOB, and Comammox, as well as their relative contributions to soil N2O emissions. This was achieved using inhibitor methods, quantitative PCR, and Illumina MiSeq sequencing. Four different treatments were compared: control (no fertilizer), mineral fertilizer (NPK: nitrogen, phosphorus, potassium), organic manure (OM: swine manure), and a combination of NPK and OM (NPKOM). The results indicated that the OM treatment significantly increased the total absolute abundances of AOA and AOB, while reducing the total absolute abundance of Comammox via qPCR. Consistent with these quantitative findings, amplicon sequencing further revealed that the OM treatment increased the relative abundances of the predominant AOA genus Nitrososphaera and AOB genus Nitrosospira, while it lowered the relative proportion of Comammox Nitrospira. The results also revealed that the NPKOM treatment significantly enhanced ammonia oxidation rates for AOA, AOB, and Comammox, which was attributed to increased soil pH values and organic carbon content. Meanwhile, compared with the control treatment, both organic fertilizer application and combined organic-inorganic fertilization significantly increased the relative contributions of AOA, AOB, and Comammox to soil N2O emissions. These findings expand the current understanding of the relationship between Comammox and canonical ammonia oxidizers in agricultural soils, providing evidence for the niche differentiation of ammonia-oxidizing microorganisms.
Soil protist communities and their interaction with prokaryotes in the rhizocompartment influence plant growth. However, the drivers of protist diversity and their co-occurrence and interaction with prokaryotic communities in dynamic rhizocompartments and between wheat varieties are not well understood. We hypothesized that rhizocompartment and wheat varieties, differing in root structure and pathogen resistance, impact protist community structure and diversity. Additionally, the co-occurrence of prokaryotes and protists was hypothesized to depend on wheat varieties selecting for different key protist-prokaryote interactions. We studied the protist community composition of four wheat varieties in three rhizocompartments: rhizoplane, rhizosphere, and bulk soil, and their co-occurrence with prokaryotic communities. In soil DNA from a greenhouse pot experiment, protist abundance was determined using qPCR, and community composition was described by metabarcoding of 18S rRNA and 16S rRNA genes. Protist community structure and abundance were significantly affected by the rhizocompartment and wheat varieties. Protist richness increased with distance from the root surface. Protist abundance was higher in the rhizocompartments of the Rembrandt wheat variety. Colpodea was more abundant in the rhizosphere, and Filosa-Sarcomonadea in the rhizoplane, compared to bulk soil. The trophic profile of the protist communities showed the dominance of protist predators, and a co-occurrence network analysis showed an intricate network with more nodes in the bulk soil. Rhizocompartment and wheat variety drive protist communities, consistent with the drivers of prokaryotic communities, demonstrating the interconnectivity of protist-prokaryotic co-occurrence in the soil rhizosphere and highlighted by the functional assignments.
The rapid retreat of mountain glaciers provides a natural chronosequence for studying the formation of ecological communities. The proglacial dynamics of springtails (Collembola) have been poorly studied in the Caucasus. This study examines a 164-year successional gradient along the Alibek Glacier foreland in the western Caucasus, analysing the development of springtail communities at the species level. Using Tullgren funnels and pitfall traps to sample nine dated surfaces (aged 1-164 years), we assessed changes in density, diversity and community structure. The pioneer assemblage was formed by a cryophilic species of Vertagopus from the supraglacial zone. This was replaced within five years. The community's structure changed fundamentally with the establishment of the forest (after similar to 70 years), achieving densities of similar to 600 individuals/dm(2) and richness of 30 species comparable to those of regional forests older than 164 years. However, the taxonomic composition of the terminal stage differed from that of nearby mature ecosystems, indicating strong local specificity. While the observed succession was broadly consistent with global trends, such as increases in abundance and diversity with terrain age, it also revealed locally characteristic trajectories in species composition and dynamics. This study provides a species-level description of a successional trajectory which can serve as a reference for future replicated studies.
Plant litter breakdown sustains nutrient cycling in forest soils, yet the relative importance of soil type, soil depth, and detritivore access remains uncertain in subtropical Atlantic Forest fragments. We quantified mass loss of Garcinia gardneriana leaf litter in two forest fragments in southern Brazil, one on Cambisol and one on Argisol. Litterbags (3 g; 30 & times; 30 cm) with coarse mesh (10 mm; microbes plus detritivores) or fine mesh (0.05 mm; microbes only) were incubated at the soil surface and at 30 cm depth. Litterbags were retrieved after 30, 60, and 90 days during spring and summer. Argisol showed higher pH, nutrient availability, moisture, and bulk density, whereas Cambisol had higher organic matter, Al concentration, aggregate stability, and penetration strength. Leaf litter decomposition rate coefficients (k) ranged from 0.005 to 0.010 d- 1, and mass loss averaged 41% in coarse-mesh and 33% in fine-mesh litterbags across all retrieval times. Soil type did not affect remaining mass, but remaining mass was higher in subsurface than surface incubations and higher in fine than coarse mesh, indicating strong effects of depth constraints and detritivore access. The edaphic fauna comprised 3161 individuals, richness and density did not differ between soils, but community composition differed, with distinct indicator families for each soil type. In Cambisol, indicator families included Muscidae, Nitidulidae, and Calliphoridae, whereas Formicidae, Philosciidae, Curculionidae, and Pteromalidae were associated with Argisol. Overall, litter breakdown was primarily regulated by detritivore access and soil depth, while soil type mainly structured assemblage identity rather than decomposition rates.
Soil organic carbon (SOC) persistence in intensively managed agroecosystems is increasingly recognized to be mediated by microbial necromass carbon, yet how fertilization intensification and straw return regulate necromass formation remains poorly understood. Using a 16-year field experiment in a tobacco-rice rotation system in subtropical China, we evaluated the effects of additional nitrogen (OFN), phosphorus (OFP), and straw return (OFR) on SOC and microbial necromass carbon under an optimized fertilization baseline (i.e., a reduced fertilizer input regime that maintains crop yield while minimizing nutrient surplus according to previous studies). Compared with optimized fertilization alone, both OFN and OFP significantly reduced SOC and total microbial necromass carbon, a decline driven primarily by reductions in fungal necromass carbon, whereas bacterial necromass carbon remained relatively stable across treatments. In contrast, straw return did not significantly enhance SOC or microbial necromass carbon. Random Forest analysis identified soil total nitrogen and available phosphorus as the dominant predictors of SOC and necromass variation. These results demonstrate that additional nitrogen or phosphorus inputs can suppress microbial-derived carbon accumulation, particularly through disproportionately negative effects on fungal necromass. Overall, the findings highlight that increasing nutrient inputs beyond an optimized fertilization regime does not necessarily enhance soil carbon sequestration in subtropical intensively managed agroecosystems.
