Pedobiologia最新文献

Cover cropping is a well-established strategy to improve soil health, especially in arid and semi-arid agricultural systems. Benefits to soil health are often mediated via effects of cover crops on soil microbial community structure, function and diversity, crucial for regulating soil biogeochemical cycles, eventually promoting agricultural sustainability. However, limited water availability is a major constraint for both cover crop growth and soil microbial activity. This study sought to characterize and elucidate the shifts in soil microbial community structure in response to different cover crops and differential irrigation treatments using phospholipid fatty acid (PLFA) profiling in southern New Mexico. We tested five cover crop treatments: Pisum sativum (Australian winter pea), Hordeum vulgare cv. Stockford (barley), Brassica juncea cv. Caliente 199 (brown mustard), a three-way mix, and a fallow control — in combination with irrigation treatments of one, two, or three irrigation applications — in a split-plot design over two years. Zea mays (sweet corn) was grown as the summer cash crop. We collected soil samples just after cover crop planting in the fall of 2018, following second year cover crop termination but during Z. mays growth in June 2020, and after the second season of Z. mays growth in October 2020. Differential irrigation treatments did not lead to consistent patterns of change under any cover crop or irrigation treatment. However, PLFA parameters in cover cropped compared to winter fallow plots tended to decrease under one and three irrigations but increased with two irrigations. Changes were more common for bacterial than for fungal PLFA biomarkers, and more common in B. juncea and H. vulgare cover crops than in P. sativa or the mix. It is important to note that, while cover crop effects were inconsistent, cover cropping did lead to some shifts in PLFA biomarkers, even in the short two-year period of cover cropping.

Soil organic matter (SOM) is the main pathway of carbon (C) input to the soil with the decomposition of shoot residues, roots and their exudates. The objective was to evaluate the contribution of different vegetal composition and plant parts of Caatinga species and the effects of introducing a grass in the soil microbial community structure and biochemical composition of SOM. A trial was conducted under controlled conditions (120 days) using, separately, the shoot and roots residues of native species from the herbaceous (HERB) and shrub-arboreal (ARB) strata and a grass (GRASS). Megathyrsus maximum, which is native from Africa, but well adapted to the semi-arid conditions of Brazil, was used. Combinations of these species in different proportions were also evaluated: (i) 55 % shrub and trees + 45 % grass (MIX1) and (ii) 75 % shrub and trees + 25 % grass (MIX2). At the end of incubation, soil samples were collected to evaluate the microbial community structure through the phospholipid fatty acids (PLFA). Physical fractioning of SOM into particulate organic matter (POM) and mineral-associated organic matter (MAOM) was also performed, followed by biochemical characterization of these fractions by thermochemolysis analysis. The ARB shoot residue resulted in a 181.5 % increase (p < 0.05) in total PLFA biomass in the soil. A significant increase (p < 0.05) in the abundance of fungi and bacteria was observed with the incorporation of shoot residues. MAOM was characterized by a higher abundance of aliphatic (31.6 ± 5.0 %) and nitrogen-bearing compounds (21.0 ± 2.0 %), while higher lignin derivatives were observed in POM (18.0 ± 0.6 %). The ground cover provided a diversity of compounds in the SOM, thus regulating the structure of the microbial community. These results highlight the importance of conserving biodiversity, both in natural ecosystems and in agroecosystems in the semi-arid environment.

Soil organic matter is the dominant pool of carbon (C) in terrestrial ecosystems. Recent advances in understanding of the mechanisms of C stabilization in the soil emphasize microbes as the main drivers. Special attention is placed on the accumulation of bacterial and fungal necromasses. This calls for development of fast and reliable methods to estimate microbial necromass in a various type of soils, including peat soils. Here we provide precise method to measure fungal and bacterial necromasses with high-pressure liquid chromatography-fluorescence detector (HPLC-FLD) and its comparison with gas chromatography method. Purity of the chromatographic peaks was confirmed with mass spectrometry. The HPLC-FLD method provides reliable results for mineral, organic and highly organic peat soils.

In the pursuit of sustainable turfgrass management for golf courses, a series of experiments was conducted to assess the potential of Trichoderma TrB (CNCM strain I-5327) as a natural solution. The research encompassed greenhouse and field trials across two golf courses. The comprehensive pot experiment investigated Trichoderma effectiveness, including native (TrB) and commercial strains, with and without organic amino acids, for turfgrass and soil health. The study followed a two-stage process, stimulating beneficial microorganisms with TrB and introducing Fusarium for biocontrol. Preliminary field trial on one golf course utilized a randomized block design to examine the effects of TrB and Trianum with amino acids, and fungicide on soil microbial community. A second field trial analyzed soil metabolic profiles after applying TrB, Trianum, and fungicide on another golf course. The greenhouse experiments demonstrated promising outcomes from the application of TrB, especially when combined with organic amino acids. This combination not only promoted plant growth and improved soil health but also effectively prevented the activation of Fusarium. In both field trials, it was observed that the introduction of TrB into the soil led to an increase in the population of soil fungi and bacteria and stimulated their activity. Our field data revealed that enriching the soil with TrB had a positive effect on soil microbial communities, while the application of fungicide resulted in a decrease in microbial activities. In summary, our research underscores Trichoderma's potential (TrB) in sustainable golf course management. These findings highlight TrB as a promising natural solution for improving turfgrass health and soil quality in sustainable management of golf course.

Amongst climate change’s impacts a major concern is salinization of soils, for example due to saltwater intrusion. The aim of the present study was to investigate in a standard field soil the impacts of soil salinity increase. The purpose was to study this in two soil invertebrates that are key model ecotoxicology test-species, Enchytraeus crypticus and Folsomia candida as surrogate representatives of the soil ecosystem. The exposure followed the standard ecotoxicity OECD (Organization for Economic Cooperation and Development) test guidelines, and the assessed endpoints were survival, reproduction and size. Exposure done in LUFA 2.2 soil, spiked with 0,0.6,1,2,3,4,5,6,8 g NaCl/kg soil dry weight (DW) for E. crypticus (21 days) and 0,0.06,0.6,1,2,3,4,5,6 g NaCl/kg soil DW for F. candida (28 days). There was a similar impact for both species in terms of survival (LC₅₀=4.2 g NaCl/kg soil DW), whereas at the reproductive output level of F. candida (EC₅₀=2.1 g NaCl/kg soil DW) was more sensitive than E. crypticus (EC₅₀=2.4 g NaCl/kg soil DW). Further, size was impacted for F. candida in a monotonic dose-response curve for both adults (EC₅₀=3.5 g NaCl/kg soil DW) and juveniles (EC₅₀=2 g NaCl/kg soil DW), whereas for E. crypticus there was an increase in reproductive output at lower concentrations (0.6–1 g NaCl/kg soil DW). This increased reproduction was associated with a larger size of adults within the same concentration range. Considering the prediction from the climate models, the soil invertebrate community will be affected. As upper soils are likely to have the highest salinity increase due to evaporation, soil surface species, such as the collembolan tested here, are at higher risk. Negative population effects were occurring within salinity levels predicted by climate change models.

Larger soil organisms have often been reported as the most sensitive to disturbances caused by cropping practices. However, soil macrofauna comprises groups with a wide diversity of morphological and ecological features, which may respond differently to applied practices. In order to further assess the effect of cropping systems on soil macrofauna, macrofauna organisms were extracted from soil blocks over 21 fields (each comprising three plots) located in the Paris basin, in autumns 2020 and 2021. Fields belonged to conventional, conservation or organic systems, either long-established (≥ 7 years) or in transition (≤ 3 years). Tillage, pesticide treatment and organic matter input intensity were assessed in each field using composite indexes of practice intensity. Macrofauna density and diversity, earthworm ecological categories, species richness and functional traits were investigated. Our results showed that the density and diversity of macrofauna demonstrated few differences regarding different cropping systems, with highly variable effects across groups and years. Specific macroarthropod groups responded differently to tillage, pesticide treatment and organic input intensity, but not over the two years of the study. Regarding earthworms, high tillage intensity had a negative effect on the density and biomass of epi-anecic juveniles and on species with a small body size. Higher organic matter inputs had a negative effect on the density and biomass of endogeic earthworms, and could be related to several earthworm functional traits (body length, mass/length ratio, carbon preferences). Effects of pesticide treatments were less clear, although they could have impacted some earthworm species. More generally, taxonomic and functional trait approaches of earthworm community led to similar conclusions. Overall, our results support the need to account for (i) the actual intensity of practices in cropping systems and (ii) the different taxonomic, trophic and ecological groups of macrofauna, in order to assess the effects of cropping systems on soil biodiversity.

The Mediterranean forest has an important ecological and economic role, being holm oak (Quercus ilex), Pyrenean oak (Quercus pyrenaica), umbrella pine (Pinus pinea) and Scot pine (Pinus sylvestris) some of its main tree species. The fungal damping-off disease caused by Fusarium seriously threatens the establishment of these forest species in nurseries and reforestation, requiring the search for environmentally friendly alternatives to control the disease. We have used different species of ectomycorrhizal fungi (EMF) as potential biological control agents (BCAs) effective against the disease: Lactarius sanguifluus, Tricholoma portentosum, Suillus luteus and Agaricus silvicola from Pinus-species, and Leccinum lepidum, Amanita rubescens and Xerocomus ferrugineus from Quercus-species. A direct in vitro confrontation was performed and conidial germination of Fusarium in contact with cell-free filtrates produced by EMF was studied. Le. lepidum was the most effective Quercus-fungus in vitro against F. oxysporum, reducing its growth up to 32 % and its conidial germination up to 87 %. S. luteus was the most effective Pinus-fungus in vitro against F. oxysporum and F. verticillioides, reducing in direct confrontation, reducing its growth up to 30 %. However, La. sanguifluus was the Pinus-fungus that inhibited conidial germination of both pathogens, up to 55 %. In planta trials were carried out with seeds of the four forest species growing on substrate colonized by Le. lepidum (in Q. ilex and Q. pyrenaica seeds, infected by F. oxysporum) or by La. sanguifluus (P. pinea and P. sylvestris seeds, infected by F. oxysporum or F. verticillioides). Only La. sanguifluus was effective in reducing disease caused by F. oxysporum (strain Fo4) on P. sylvestris seeds. Therefore, EMF may be a potential tool in the control of damping-off in forest species, requiring further research.

We investigated how soil fauna impact leaf litter decomposition in north temperate forests using litter bags with different mesh sizes (5 mm, 0.5 mm, and 0.01 mm) to exclude specific fauna by size. The experimental design included two regions (warmer, cooler) in New York State, two forest types (coniferous, deciduous), and litter bags with four tree species (yellow birch, sugar maple, red oak, red pine) that varied in litter resource quality. Excluding most soil fauna with 0.01-mm mesh decreased mass loss from litter bags by 8.8 % overall; by 19 % in the relatively warmer region; by 12 % in coniferous forest stands; and by 18 % for high-quality yellow birch litter but not for high-quality sugar maple litter or low-quality red oak and red pine litters. Mass loss rates were predicted by initial nitrogen concentrations and by initial ratios of carbon / nitrogen and lignin / nitrogen of the leaf litter; these relationships were stronger for litter bags that excluded soil fauna. Fauna extracted from the leaf litter residue were predominantly Acari (mites) and Collembola (springtails). Soil fauna mediated the extent that biochemical fractions (nitrogen, hemicellulose, cellulose, lignin) were lost from decomposing litter but in idiosyncratic ways. Not only are soil fauna impacts on leaf litter decomposition widespread, but, as shown here, they can be idiosyncratic when evaluated with several litter species that differ in resource quality, placed in different forest types, and across a climate gradient. Future analyses of soil fauna impacts on leaf litter decomposition should combine litter-, site-, and climate-related variability to improve understanding and enable prediction.

Dark septate endophytes (DSEs) are a type of endophytic fungus that commonly colonize plant root systems in extreme environments, and play a role in enhancing resistance to drought stress. To investigate the potential applications of DSEs in improving drought tolerance of desert plants, three DSE strains isolated from Haloxylon ammodendron for strong drought tolerance - Alternaria tellustris (AT), Cladosporium sp. (CL), and Paraphoma radicina (PR) - were screened through pure culture in vitro. Pot experiments of H. ammodendron were then conducted with different DSE, water, and soil treatments. In both sterilized and nonsterilized soil, DSEs showed growth-promoting and drought-resistant properties, with a stronger effect observed under sterilized soil treatment. The results showed that in sterilized soil, AT and CL increased root biomass, total biomass and root shoot ratio under high drought treatment, while PR effectively enhanced branch number and root biomass under normal water treatment. Physiologically, DSEs improved plant drought tolerance by increasing soluble sugar content and superoxide dismutase activity. Notably, DSE inoculation facilitated the uptake and utilization of soil nutrients such as available phosphorus, nitrate nitrogen, and free amino acids by plants in both sterilized and nonsterilized soil. Overall, our study highlights the potential of DSEs in improving drought resistance and promoting the growth of desert plants.

Sugarcane vinasse is a residue from ethanol production, which has high content of nutrients and organic matter, improving chemical, physical and biological changes in the soil. This study evaluated nematode community structure, food web, metabolic footprint, and soil quality in sugarcane fields under continuous vinasse fertigation. Soil samples were collected from four sugarcane fields in Pernambuco State, Brazil, under continuous vinasse fertigation for nematode identification at the genus (plant parasites) and family (free-living) level, physical and chemical analyses of the soil. Nine genera of plant-parasitic nematodes and five families of free-living nematodes were identified in sugarcane fields. Plant-parasitic nematodes were dominant, except in the field with five years of continuous vinasse application. The genera Mesocriconema, Meloidogyne, Helicotylenchus and Pratylenchus were frequent in all fields. Predators and fungivores nematodes were few abundant, although, according to the soil food web, all sugarcane fields were low to moderately disturbed environments. A positive correlation was observed between the microbial respiration and Rhabdtidae in fields with five years of vinasse application, and between the electrical conductivity of the soil and Meloidogyne in fields without vinasse application. We highlight those alterations in the structure and composition of the nematode community, and soil characteristics that can occur due to vinasse fertigation in sugarcane fields.