Biology and Fertility of Soils最新文献

Plant residue added into soils may release substances interfering DNA extraction and PCR, influencing the subsequent profiling of soil microbial community. Many field and laboratory studies investigate the effect of plant residue (e.g., straw) on soil bacterial communities after a period of time. However, whether aged plant residue will exert an interfering impact remains unanswered. Here, five air-dried soils were mixed with 5 g kg⁻¹ rice straw and then stored at room temperature (~ 25 ℃), -20 ℃, or -80 ℃. At all three temperatures, we found that compared to the unamended control soils, plant residue had a minor effect (< 10%) on bacterial abundance and no significant effect on bacterial community composition after 4 and 10 weeks. However, for two air-dried soils (soils 4 and 5), we observed a significant increase in bacterial abundance and a shift in bacterial community composition after storage for 4 and 10 weeks, compared to week 0, at all three temperatures. These findings stood when we repeated the experiment with a rice straw addition rate at 20 g kg⁻¹. Many of the phylotypes that increased after storage in soils 4 and 5, which had the highest pH and lowest nutrient contents in all soils, are reportedly tolerant to dry, alkaline, or oligotrophic conditions. Metagenomic analysis further showed that genes related to bacterial drought, cold, and alkali resistance increased in soils 4 and 5 after storage. These results suggest that aged plant residue does not affect bacterial communities in air-dried soils but for alkaline and oligotrophic air-dried soils, storage may do even at -80 ℃. This work can help us optimize the storage of soils for microbial analysis and understand microorganism survival in dry soils.

The home-field advantage (HFA) hypothesis postulates that plant litter decomposes faster in the home habitat than in other locations (i.e., away site) due to specialized microbial decomposers. However, we still have limited understanding of how specific microbes contribute to HFA. Here, we examined how variation in HFA relates to differences in soil bacterial diversity and interconnections among co-existing bacteria taxa. A 480-d reciprocal transplant experiment was designed using Schima superba and Zea mays litter collected from forest and farmland ecosystems, respectively. Our findings showed that litter decomposition is associated with specific soil bacterial taxa that generate HFA effects for litter use. The decomposition of labile Z. mays litter in away site increased the biodiversity of soil bacteria, thereby creating more complex and stable co-occurrence networks. In contrast, the decomposition of recalcitrant S. superba litter in away site reduced the interconnections among co-existing taxa by preventing the establishment of specific taxa such as Proteobacteria and Actinobacteria, resulting in less complex and stable networks. The simplified bacterial networks in away sites led to reduced ecosystem functions, including nutrient cycling and decomposition, and were responsible for the generation of HFA in litter decomposition. Furthermore, the effect of soil bacterial diversity on litter mass loss was indirectly driven by network stability, suggesting that interconnections among co-existing taxa enable a better explanation how specific microbes contribute to drive HFA than the diversity metrics. Our results highlight the importance of co-occurrence networks as a key component of microbial biodiversity linking it with litter decomposition.

Aluminum (Al) toxicity is a major limiting factor for crop production in acidic soils. The diverse mechanisms by which microbes enhance plant tolerance to Al toxicity, such as Al ion absorption, regulation of metal ion transport, adjustment of rhizosphere pH, filtration of Al ions through mycelial networks, and interaction with root traits, have attracted increasing attention. In this review, we focus on the physiological and biochemical effects of Al toxicity on plants, as well as the mechanisms of plant resistance to Al toxicity. We particularly emphasize the interaction between plants and microorganisms, and how microbes could be used to enhance plant tolerance to Al toxicity. Notably, microbial inoculation strategies often face challenges due to the soil properties and competitive exclusion by indigenous soil microbiomes. Despite these challenges, we propose that combining omics techniques with synthetic microbial consortia designed for Al stress may be a more effective approach to addressing the related issues in this research area. These advancements will pave the way for harnessing microbiome engineering as a powerful tool to enhance agricultural production and optimize practices in Al-challenged environments.

Drought events are becoming more severe and recurrent over Europe. Changes in temperature and rain patterns can affect soil nutrient mobility and availability, modulating the biomass and activity of soil microbial communities. Here, we investigated the effects of drought on extracellular polymeric substances (EPS) and microbial biomass carbon (MBC) and nitrogen (MBN) in differently managed cropping systems. An on-field drought simulation experiment using rain-out shelters was conducted as part of a long-term field experiment cultivated with winter wheat, comparing cropping systems with contrasting fertilization strategies and crop protection measures: A biodynamic system and a mixed conventional system with no pesticide application, and a purely minerally fertilized conventional system, with conventional pesticide use. The implemented drought lasted for three months, starting at plant tillering stage and ending at ripening stage. No watering was performed on the drought treatment during that period. Soils were sampled at stem elongation, flowering, and ripening. EPS-carbohydrates and EPS-proteins significantly increased by approximately 20% due to induced drought but remained roughly constant from stem elongation to ripening under drought. Mean EPS-carbohydrates to EPS-proteins ratio was 1.9. MBC and MBN remained largely unaffected by drought. The ratio of both EPS fractions to microbial biomass was lowest in the biodynamic system and highest in the minerally fertilized conventional system, indicating that rhizodeposits and mucilage were predominantly diverted into microbial biomass, rather than into microbial EPS. This might be an important reason for the higher soil fertility of the biodynamic system.

A field experiment was conducted on a Chinese hickory (Carya cathayensis Sarg.) plantation using two types of hickory husk mulching: fresh and composted husk mulching (FHM and CHM, respectively). Soil samples were collected 90, 180, 270, and 360 days after husk mulching to determine the effects of the treatments on soil nutrients, aggregates, microbial communities, and nutrient cycling-related enzyme activities. We found that soil pH and organic carbon content (SOC) increased by 4.10–12.16% and 13.72–76.39% after FHM and CHM treatment, respectively. FHM and CHM treatments increased the proportion of > 2000 μm aggregates by 15.71–24.74% and decreased the proportion of < 250 μm aggregates by 7.87–38.25%. The total soil microbial, fungal, bacterial, and actinomycete biomasses significantly increased after husk mulching (P < 0.05). The α-glucosidase, β-glucosidase, and leucine aminopeptidase activities increased 29.17%–99.55%, 27.03%–49.19%, and 40.35%–118.47% after the husk mulching treatments, respectively. Soil pH, organic carbon, available potassium, and the proportions of aggregates of > 2000 μm and 1000 – 2000 μm were the main factors influencing the soil microbial community composition. Partial least squares path modeling demonstrated that husk mulching increased soil enzyme activity through altering the composition of the main microbial groups. Organic mulching may affect soil aggregate microstructure through increasing SOC and influencing the composition of the main microbial groups, directly affecting enzyme activities. Overall, the husk mulching treatments increased SOC as well as soil stability and decreased pH, describing the benefits of the application of this soil management practice in sustainable agroforestry.

Stimulated microbial nitrification has been reported during grassland degradation when plants and microbes compete for declined nitrogen (N) resources. However, it remains unclear whether inhibiting microbial nitrification would change such competition and alter grassland productivity. Here, we investigated changes induced by the nitrification inhibitor (NI) application in N acquisition strategies, niche breadth and competitiveness of plants and microbes, with different soil N levels in greenhouse. The ¹⁵N labeling technology was employed with ammonium, nitrate and glycine to quantify N uptake. NI significantly (P ≤ 0.02) decreased abundances of AOA and AOB genes for microbial nitrifiers in low-N (1.3 g/kg for total N) soils, and AOB abundance in high-N (1.8 g/kg) soils, validating the efficacy of NI in inhibiting nitrification. NI significantly (P < 0.01) increased the soil ammonium content by 25.50% and 10.43% in low- and high-N soils, respectively. Moreover, NI narrowed the plant niche breadth for N utilization by concentrating more on ammonium uptake in both low- and high-N soils. Consequently, NI significantly (P ≤ 0.04) increased the plant biomass by 10.02% and 10.16% in low- and high-N soils, respectively. In comparison, microbial competitiveness against plants for ammonium decreased by NI in low-N soils, leading to a 23.41% reduction in microbial biomass (P < 0.01); while they remained unchanged in high-N soils. Overall, our study revealed the effectiveness of NI application for enhancing grassland productivity by reducing plant niche breadth through utilizing more ammonium, suggesting a viable strategy to restore degraded grasslands without any external N input.

Antibiotic resistance has emerged as a global threat to public health. However, the current information is insufficient to understand how other pollutants, such as fungicides and nanoplastics, affect the spread of antibiotic resistance genes (ARGs) among bacteria in the soil. Here, our findings revealed that polyethylene nanoplastics (PENPs) prolonged the persistence of pyraclostrobin (PYR) in the soil by 13 days, increased PYR bioaccumulation in earthworm (Eisenia fetida) by 8.4%, and reduced its weights by 26.8%. PYR alone or combined with PENPs significantly increased the microbiome diversities of earthworm guts, while PENPs alone decreased those but increased the relative abundances of Proteobacteria and Firmicute. PYR and/or PENPs enhanced the diversity and abundance of ARGs in earthworm guts, the range of ARG hosts, and the complexity of ARGs and antibiotic-resistant bacteria coexistence network. The abundance of plasmid-origin ARG-harboring contigs in PYR, PENP, and PYR + PENP treatments was 1.5-, 3.8-, and 2.4-fold higher than that in the control, respectively. Overall, PYR and/or PENPs specifically disturbed the antibiotic resistome in earthworm guts by altering the bacterial community composition and richness, increasing the abundance of mobile genetic elements (MGEs) and ARGs, and modifying the co-occurrence pattern of ARGs-MGEs, particularly plasmids.

A large fraction of the Mediterranean soils is threatened by losses of organic matter and biodiversity, which could compromise the provision of soil ecosystem services and the stability of ecosystems in the face of climate change. In this work we explore several hypotheses related to the role of C inputs and microbial diversity on soil multifunctionality and its resistance to drought in degraded Mediterranean soils. We designed a factorial experiment to test the effect of the addition of an organic amendment and of microbial diversity (using four inoculants with different abundance and diversity of soil microbiota), on the resistance of soil functionality against drought in pot mesocosms. Pots were sown with a forage mixture (Lolium rigidum and Medicago polymorpha), and plant productivity, soil chemical properties, and microbial activity and diversity were measured before and after a simulated drought event. The amendment favored soil moisture, enhancing the stability of the productivity of M. polymorpha. In contrast, the manipulation of inoculation load had a limited effect on the resistance of microbiological activity. Indeed, microbial functioning was highly resistant to reduced water inputs, probably related to the prevalence of Gram positive bacteria. Besides, the effect of microbial diversity on soil multifunctionality was limited. Structural equation modelling confirmed that the enhancement of multifunctionality after soil amendment was attributed to the direct effect of organic C on soil moisture and chemical fertility. In these degraded soils, physico-chemical limitations are the major drivers of soil multifunctionality rather than bacterial or fungal diversity.