Applied Soil Ecology最新文献

Microplastics, recognized as some of the most pervasive and enduring pollutants, have emerged as a potential threat to environmental eco-health. While much is known about the effects of microplastics on soil microorganisms, our understanding of how they interact with terrestrial organisms and the underlying mechanisms remains limited. In this study, the effects of polyethylene microplastics at a concentration of 0.5 % (w/w) on the antioxidant enzymes, gut microbiota of Eisenia fetida and the soil microbiota on days 1, 3, 7, 15, and 30 were investigated. The results indicated that exposure to microplastics slightly increased the activities of superoxide dismutase (1.22-fold on day 3, 1.12-fold on day 7) and catalase (1.10-fold on day 3, 1.09-fold on day 7) in E. fetida, while exposure markedly decreased peroxidase activity (1.33- to 1.79-fold) throughout the whole period. Both the soil microbiota and the gut microbiota of E. fetida in terms of diversity and composition were significantly affected by the microplastic amendment, and their structure tended to be similar throughout the exposure time. The family Nocardiaceae was significantly enriched in both the soil and E. fetida gut biota with microplastic exposure. Our results demonstrated that the antioxidant enzyme response of E. fetida was closely related to both the microbiota, although this relationship with the gut microbiota may have been weakened by microplastic exposure. Overall, this study furnishes new perspectives on the ecotoxicity of microplastics, revealing significant implications for the vitality of soil-dwelling organisms and the overarching health of terrestrial ecosystems.

Reniform nematode (Rotylenchulus reniformis) is a parasite of cotton (Gossypium hirsutum) and crop rotation is commonly used for its management. One specific rotation system is a sod-based rotation, which uses two years of bahiagrass (Paspalum notatum) followed by one year each of peanut (Arachis hypogaea) and cotton, versus a conventional peanut-cotton-cotton rotation. High population densities of reniform nematode are found below plow depth in the soil profile, yet conventional chemical management is often not able to manage these deeper populations, nor is much known about other plant parasites such as ring nematode (Mesocriconema ornatum) and spiral nematode (Helicotylenchus dihystera) at these deeper depths. Our study aimed to investigate how long-term cropping history (since 2000) affects the vertical spatial distribution of plant-parasitic (reniform, ring, and spiral) nematodes under different irrigation regimes. Between March 2017 and January 2019, soil samples were collected to a depth of 120 cm before planting, after harvest, and in the winter using a hydraulic probe. Nematode abundances (including enumeration of all reniform nematode life stages) were analyzed in 30 cm-sections. There were no significant effects of irrigation on nematode abundances (P > 0.05). In each sampling date, all reniform nematode abundances decreased stepwise as soil depth increased, but spiral and ring nematodes were nearly absent below 30 cm. Sod-based rotation generally reduced reniform nematode abundances at all depths compared with conventional rotation, although differences were more pronounced in the shallower depths (0–30 and 30–60 cm). Conversely, at 0–30 cm soil depth, ring nematode abundances were generally greatest in the peanut phase of sod-based rotation. Similarly, spiral nematode abundances, at 0–30 cm soil depth, were generally significantly greater in bahiagrass phases than other phases and variously greater in first-year cotton (sod-based or conventional). Overall, sod-based rotation helped manage reniform nematodes up to 120 cm deep in the soil profile. Sod-based rotation was detrimental for managing minor plant-parasitic nematodes spiral and ring nematodes, and those nematodes were scarce below 30 cm deep in the soil profile.

Large-scale planting of Chinese fir (Cunninghamia lanceolata) can bring considerable economic benefits but also seriously alters soil properties, disrupting soil microbial survival patterns and giving rise to distinct microbial communities. Nitrous oxide (N₂O) reduction is the sole recognized biological sink for N₂O, thereby playing a critical role in forest nitrogen cycling. However, the distribution of N₂O reducers in Chinese fir plantation soils and the underlying factors at a regional scale remain unclear. Here, we assessed the abundance, diversity, and community structure of nosZ I-type N₂O reducers in soil samples collected from nine state-owned forest farms in Fujian Province, China. The abundance of nosZ I-type reducers exhibited significant variation across sites, with altitude exerting the greatest influence, positively influencing their abundance. Soil organic carbon (SOC) and dissolved organic carbon (DOC) were the strongest predictors of alpha-diversity. Interestingly, SOC and DOC exhibited a negative association with nosZ I-type reducer alpha-diversity. Additionally, DOC played a significant role in influencing community structure. All nosZ I sequences were associated with Alphaprotebacteria and Betaproteobacteria, with Alphaproteobacteria dominating nosZ I-type reducer communities in all soils, accounting for over 90 % of the total sequences. Moreover, the modified stochasticity ratio values exceeded 0.5 at all sampling sites except for one, characterized by the lowest pH and relatively lower nutrient content, indicating the predominance of stochastic processes in community assembly. Taken together, our results provide novel evidence that the augmentation of organic carbon content could potentially reduce diversity and alter the structure of nosZ I-type reducer communities, with potential implications for N₂O emissions in Chinese fir plantations.

Cover crops and manure compost application are two common nutrient management practices in organic production. However, their interactive influences on the biogeochemical properties of sandy Coastal Plains soils are not well-documented. Here, we investigated their effects on nitrogen (N) availability and the abundance of selected N functional genes in organic vegetable production. An experiment was established in 2020 with a fully crossed treatment of manure compost application (2365 and 0 kg ha⁻¹) and cover crop inclusion (cereal rye, hairy vetch, mixtures of rye and vetch, and no cover crop control). Two years after establishment, the highest nitrate (NO₃⁻) concentrations were found in the vetch + manure compost plots, while manure compost plots increased ammonia (NH₄⁺) concentrations compared to non-manure compost plots. N-acetyl-β-D-glucosaminidase (NAG) activities were higher in vetch plots than in rye and control plots, while leucine aminopeptidase (LAP) activities were higher in manure compost plots than in the non-manure compost plots. Integrating cover crops introduced higher N mineralization potentials, which, however, was not observed for manure compost. Manure compost resulted in higher fungal abundance than no manure control plots. Manure compost increased the abundance of ammonia-oxidizing archaea (AOA) only in the mixture, and the vetch plots had a higher abundance of ammonia-oxidizing bacteria (AOB) than other cover crop plots. Both cover crops and manure compost increased N availability but posed distinct short-term impacts on soil microbial communities.

Arbuscular mycorrhizal fungi (AMF) can form a beneficial symbiotic relationship with shrubs, thereby playing a crucial role in enhancing the stability and sustainability of fragile arid and semiarid ecosystems. How will soil microbial metabolism change from monoculture to the mixed planting of shrubs? What regulatory role will AMF play in this process? Monoculture and mixed planting of three native shrubs were carried out, and treatments with and without AMF inoculation were established at the same time. The indicators of soil microorganisms, extracellular enzymes and nutrients were measured. The variations in ecoenzymatic stoichiometries, microbial nutrient limitations and regulatory factors were also analyzed. The ratio of soil microbial biomass C to N decreased significantly from the monoculture to the mixed planting of shrubs. The ratios of C- and P-acquiring enzymes and N- and P-acquiring enzymes increased in the mixed planting treatment. The microbial P limitation in the monoculture treatment was replaced by microbial N limitation in the mixed planting treatment, and the soil microbial C limitation increased in the mixed planting treatment. AMF inoculation mainly regulated the ecoenzymatic stoichiometric ratios and microbial nutrient limitations in the monoculture treatment but had little effect on the mixed planting treatment. The main factors influencing microbial C limitation were shrub species and AMF richness in the monoculture and mixed planting treatments, respectively. Soil available nutrients and AMF richness and diversity were identified as the main factors influencing microbial P limitation in the monoculture treatment compared with microbial N limitation in the mixed planting treatment. AMF inoculation and the mixed planting of shrubs effectively promoted soil nutrient cycling, which is highly important for restoring arid and semiarid vegetation.

Organic fertilizer application has been proved to improve soil fertility, but it is not yet known whether organic fertilizers can improve soil quality and maintain soil health. Here, we explored the influence of manure replacing chemical fertilizers on soil quality by measuring soil nutrients, enzyme activity, and microbial abundance. We set up four fertilization treatments: unfertilized control (CK), 100 % fertilizers containing nitrogen (wheat, 157.5 kg ha⁻¹; maize, 178.5 kg ha⁻¹), phosphorus and potassium (NPK), 50 % fertilizers containing nitrogen (wheat, 78.75 kg ha⁻¹; maize, 89.3 kg ha⁻¹), phosphorus and potassium +50 % manure (wheat, 78.75 kg ha⁻¹; maize, 89.3 kg ha⁻¹) (NPKM), and 100 % manure (wheat, 157.5 kg ha⁻¹; maize, 178.5 kg ha⁻¹) (M). This paper focused on the calculation of the weights of 18 soil biotic and abiotic indicators by principal components analysis (PCA), and the calculation of soil quality by Total Data Set. Results showed that compared to NPK and CK, M increased soil organic carbon, total nitrogen and dissolved organic carbon at the wheat filling stage (p < 0.05), while it increased soil available phosphorus, dissolved organic carbon, total nitrogen, ammonium nitrogen, microbial biomass carbon, microbial biomass nitrogen and N-acquisition enzyme activity at the maize filling stage (p < 0.05). The soil quality index of M in the rhizosphere and bulk soils was 48.7 %–78.0 % (p < 0.05) and 50.0 %–74.7 % (p < 0.05) higher than those of CK at the wheat and maize filling stages, respectively. Our findings suggested that complete replacement of chemical fertilizers with organic manure increased soil quality by enhanced soil biotic and abiotic factors in the wheat-maize rotation system. In the future, the use of organic fertilizers should be appropriately increased in the management of the fields to maintain soil health and adhere to the sustainable development of agriculture.

Mining has led to dramatic ecosystem degradation, the destruction of vegetation and irreversible damage to soil structure and nutrient cycling; additionally, heavy metal (HM) contamination has affected soil nitrogen (N) cycle-associated microorganisms and disrupted soil aggregate structure. To explore the mechanism of soil N recovery in mining areas, we investigated the effects of two N fertilizers (urea (U) and ammonium chloride (AC)) and nine different fertilization patterns on the nitrification process and ammonia oxidizers in soil aggregates via incubation experiments. The results showed that different N treatments had different influences on the distribution of AOA and AOB amoA gene abundance and microbial community structure in soil aggregates. The AOB amoA gene abundance was significantly greater than the AOA amoA gene abundance in aggregates. The dominant species of AOA and AOB were Nitrososphaera and Nitrosospira, respectively, which were mainly found in microaggregates and accounted for 10.3 % to 25.0 % and 31.5 % to 60.1 %, respectively, of the microaggregates. Dissolved organic nitrogen (DON) can be used as an important variable to explain variations in AOA communities, and microbial nitrogen (MBN) content, tartaric acid content, cellulase activity and AOB amoA gene abundance can be used as important variables to explain variations in AOB communities. N fertilizer addition resulted in potential ammonia oxidation (PAO) values ranging from 0.079 to 0.236, 0.100 to 0.5953 and 0.146 to 0.905 μg⸱NO₂⁻-N d⁻¹ g⁻¹ in mega-, macro- and microaggregates, respectively, which suggested that PAO values increased with decreasing aggregate size. In addition, the total nitrification potential (TNP) in macroaggregates was greater than that in mega- and microaggregates, which was the main reason for the increase in the NO₃⁻ content in macroaggregates. AOB amoA gene abundance was significantly positively correlated with TNP, and AOB amoA gene abundance was more significantly positively correlated with PAO values than was AOA gene abundance, which suggests that AOB dominated ammonia oxidation and nitrification processes in aggregates. Our research contributes to an understanding of the mechanisms underlying the effects of different types of N fertilizers on nitrification processes and ammonia oxidizers in soil aggregates and provides insights into N management in contaminated soils in mining areas.

The newly discovered complete ammonia oxidizer (comammox Nitrospira) is able to single-step nitrification capability, and increased our understanding of soil nitrogen cycling. However, the response of comammox and ammonia-oxidizing bacteria (AOB) and archaea (AOA) to long-term fertilization and rhizosphere effects in paddy soils and their relative contribution to the nitrification-derived N₂O emissions is still unclear. Here, we collected rhizosphere and bulk soils with thirty years of different fertilization strategies, i.e., non-fertilization (CK), chemical N, P, and K application (NPK), and NPK plus pig manure application (NPKM), respectively, to test changes in nitrification potential rate (PNR), N₂O emission fluxes, abundance of ammonia oxidizers and their significant drivers. The result showed that NPKM significantly increased soil C and N levels, the proportion of soil middle-size particles (40.35–148.00 μm class), and soil PNR, but decreased soil N₂O emissions, especially in the drying time of paddy (P < 0.05), compared to NPK fertilization. NPKM had the highest values of AOA, AOB, and comammox clade A amoA gene copy numbers (P < 0.05), but clade B was increased by the NPK in the rhizosphere soil. Furthermore, fertilization showed greater effects on ammonia oxidizers (except for clade B) than the rhizosphere effect. Mantel test showed that SOM, TP, pH, NH₄⁺, and NO₃⁻ were main abiotic factors causing the niche separation among ammonia oxidizers. Linear regression analysis and structural equation model (SEM) showed that both PNR and N₂O emission fluxes were significantly associated with the abundance of AOB and comammox clade A (P < 0.05). Therefore, our results underline the importance of AOB together with comammox clade A in nitrification and N₂O production in long-term organic fertilized paddy fields, which could provide new ideas for the mitigation of N₂O emission by adopting organic fertilization scenarios in Chinese paddy fields.

The Lhasa River Basin currently faces severe land degradation. In recent years, several dams have been built on the main stream, whereas, their impact on land desertification remains less elucidated. Herein, we investigated variances of soil properties and microbial communities in biological soil crusts (BSCs) along the valley area of Lhasa River and the mountain slope (altitude gradient) in reservoir area after five years of dam construction. Soil nutrient and water contents, enzyme activities, and N-cycle related functional gene copies significantly increased in reservoir-affected areas and decreased with the increase of mountain slope altitude and the distance away from the reservoir, which were usually degraded soil patches; similarly, the relative abundance of bacteria, fungi and moss in BSCs significantly increased in reservoir-affected areas, whilst that of cyanobacteria was higher in degraded soil patches. The linear and structural equation models also showed that dam construction altered water distribution status of soil surface, which enhanced soil properties, N-cycle and increased the relative abundance of moss of BSCs, and successfully accelerated the development and succession of BSCs in degraded soil. This study firstly reported that dam construction could accelerate the succession process of degraded soil in the reservoir affected area and thus a reference for ecological restoration of desertification soil of the Lhasa River Basin in QTP.

Using a mesocosm experiment, we investigated the individual and interaction effects of two earthworm species with contrasting behaviour on soil structure and water transfers. The anecic species Amynthas zenkevichi (Thai, 1982) and the polyhumic endogeic species Pontoscolex corethrurus (Müller, 1857) were incubated in repacked soil columns alone or together for three months under laboratory conditions. The volume of belowground casts, empty burrows and lateral soil compaction were assessed using X-ray computed tomography. The production of surface casts and the amount of food ingested were also recorded. The soil moisture at 7 cm depth and water evaporation of the whole column were monitored regularly. Soil water infiltration was assessed using the Beerkan method at the end of the experiment. A. zenkevichi burrows were less numerous (25 vs. 85), more continuous (41 vs. 0 cm³), more connected from the surface to the bottom of the columns (17 vs. 0 cm³) and more compacted laterally (243 vs. 92 cm³) than those of P. corethrurus. Conversely, P. corethrurus burrows were more abundant in the top 5 cm of the columns and more backfilled by casts than those of A. zenkevichi (36 vs. 5 %). Both species ingested buffalo dung provided at the soil surface and produced surface casts at similar rates. Interactions resulted in an increase in surface activity of more than 40 % and a decrease in the depth and continuity of burrow systems. The water infiltration rate was increased by 3.5 times (compared to the control soil without earthworms) by A. zenkevichi burrows and was not modified by interactions. P. corethrurus increased the cumulative water evaporation by 10 % and decreased soil moisture by 3 % (compared to the control soil without earthworms), whereas A. zenkevichi had marginal effects on these parameters. Globally, interactions led to a slight positive synergistic effect on soil resistance to water loss by evaporation, which was likely related to the increase in surface casting activity. To conclude, this study stresses the importance of considering interactions between earthworms in soil and the need to confirm our findings under natural conditions.