查看更多>>摘要：Intercropping is a sustainable agroecological tool known to provide multiple benefits to farmers. Several studies have shown that arbuscular mycorrhizal fungi (AMF) play a key role for the improved grain yields in intercropping systems through facilitative nutrient and water uptake via the common mycorrhizal network (CMN), yet little is known on the rate of hyphal spread. Here we hypothesized that AMF species differ in the rate of extraradical hyphae to spread from one plant to another, thereby affecting the growth of the intercropped plants. To test our hypothesis, we established experimental microcosms in the greenhouse, in which one pigeon pea (Cajanus cajan) and two finger millet (Eleusine coracana) plantlets were kept in separate pots, connected by soil bridges of 5 or 12 cm length, inaccessible to roots but accessible to fungal hyphae. The pigeon pea plants were pre-inoculated with Claroideoglomus etunicatum, Rhizophagus fasciculatus or Rhizophagus irregularis. All three AMF species led to a strong growth promotion compared to uninoculated control of the short microcosms and more than doubled the biomass of pigeon pea. The biomass as well the phosphorus content of finger millets connected by AMF to the pigeon pea differed with the length of the soil bridge and the species of AMF. By applying 15N isotopes to the soil of pigeon pea pots we revealed that in both lengths of the microcosms R. fasciculatus and C. etunicatum transported nitrogen from pigeon pea to finger millet across distances of up to 12 cm but R. irregularis did not. Furthermore, by destructive sampling, we estimated a hyphal spread of 4.1 mm d-1 by C. etunicatum across a 12 cm soil bridge. We conclude that the row distance between the crops and the choice of AMF species play a crucial role for the application of AMF as biofertilizer.
Emery, Sarah M.Bell-Dereske, LukasStahlheber, Karen A.Gross, Katherine L....
7页
查看更多>>摘要：Anthropogenic global change is increasing the severity and frequency of abiotic stresses such as drought that are likely to affect soil communities. Arbuscular mycorrhizal fungi (AMF) play important roles in many soil processes, so it is important to understand how drought affects AMF biodiversity. This is especially relevant in agricultural systems where crops rely on AMF associations for water and nutrient uptake, and where management decisions such as crop selection and fertilizer application may influence how the AMF community responds to drought. In this study, we examined the effects of reduced precipitation and nitrogen fertilization on AMF richness, community composition, and root and soil colonization in monocultures of two cultivars of switchgrass (Panicum virgatum) grown for bioenergy feedstock. We conducted a two-year field experiment using rain-out shelters to manipulate precipitation in mature stands of switchgrass growing in a long-term nitrogen fertilization (0 or 56 kg N ha(-1)) experiment at the W.K. Kellogg Biological Station Long-Term Ecological Research site in Michigan, USA. We expected that AMF richness and colonization would decrease due to drought, as predicted by the stress exclusion hypothesis. Contrary to our expectations, we found that drought stress increased AMF species richness in fertilized plots by 15%; there was no effect of drought on AMF richness in unfertilized plots. Drought also significantly altered AMF community composition, primarily due to increases in Rhizophagus taxa abundance, and reduced AMF root colonization in switchgrass by 6%. We also found variation in AMF richness and colonization across switchgrass cultivars as well as sampling dates. The changes in AMF richness and composition that we observed in this study may have implications for perennial bioenergy feedstock selection and management as changes in AMF communities may feedback to affect host plants.
查看更多>>摘要：Knowledge remains limited on how the structure of microbial community in paddy soils changes in relation to different types of fertilizers with same amount of nutrients. Thus, here, soil samples were collected at 0-10, 10-20, 20-30, and 30-40 cm depths from a paddy field subjected to four long-term fertilization treatments (no fertilization, mineral fertilization, mineral fertilization combined with rice straw, and chicken manure) and analyzed for microbial biomass and community composition. In unfertilized soils, microbial biomass decreased from 0 to 40 cm (with actinomycetes < gram-positive (G+) bacteria < gram-negative (G-) bacteria < fungi). This ordering was retained after fertilization, but the decline with depth was less pronounced. Both mineral and mineral plus organic fertilization increased the biomass of G+ bacteria compared to G- bacteria (22.7-56.2% increase) and actinomycetes (14.8-52.5% increase). Thus, over the long term, G+ bacteria benefited the most from mineral fertilizer than the other microbial groups. The partial replacement of mineral fertilizer with manure primarily enhanced the abundance of G+ bacteria at 0-30 cm soil depth, whereas replacement with straw enhanced the abundance of fungi at 10-20 cm soil depth. Our findings demonstrate that the structure of the microbial community is strongly impacted by long-term fertilization, independent of fertilizer type.
查看更多>>摘要：Plastic film mulching (PF) can change soil properties and microbial community structure. However, the effect of PF on soil microbial interactions in different aggregate fractions is still unclear. We conducted a three-year field trial in black soil of northeastern China to evaluate the variation in soil microbial interactions and community structure in different aggregate fractions after PF. Compared with the control (CK), the PF treatment significantly decreased the humification index by 13.9% and chromophoric dissolved organic matter by 36.6% and significantly increased the fractal dimension by 4.8% and electrical conductivity by 22.8%. In addition, the PF treatment significantly decreased the relative abundances of Chloroflexi, Planctomycetes and Verrucomicrobia but significantly increased the relative abundance (RA) of Proteobacteria. Furthermore, the PF treatment significantly decreased the RA of Glomeromycota in megaaggregates ( 2 mm, ME) and macroaggregates (0.25-2 mm) and the RA of Actinobacteria in microaggregates (<0.25 mm, MI), related to decreases in aggregate stability. Compared with the CK treatment, the PF treatment significantly decreased the bacterial Shannon index in ME but significantly increased the fungal Shannon index in MI. Moreover, 8-1,4-glucosidase activity significantly influenced the community structure of soil bacteria and fungi. The PF treatment decreased soil microbial interactions, especially in ME. The keystone of the microbial network shifted from 0319-6A21 (Nitrospirae) to Gsoil-1167 (Actinobacteria) after PF. In short, PF decreased soil aggregate stability and microbial interactions in black soil in a subhumid area.
查看更多>>摘要：A challenge in biogeography is to understand what are the factors and how they regulate soil microbial communities. To explore the coexistence pattern of bacterial community and the factors shaping agricultural soil bacterial community at spatial scale, 135 soil samples were collected from a typically agricultural province in the North China Plain and analyzed with high-throughput 16S rRNA gene sequencing. As expected, bacterial community dissimilarity showed significant distance-decay relationships with 42.2% variation explained by geographic distance and physicochemical factors. Bacterial phyla abundance showed different responses to environmental factors among which soil pH was the primary factor shaping soil bacterial community structure. Bacterial communities in acidic soils suggest lower phylotype richness and phylogenetic diversity and its associated network structure showed greater connectivity and stability compared to those in neutral and alkaline soils. Soil bacterial community diversity was also varied with soil type. Unlike the simplest topological features of co-occurrence network in Cinnamon soil, bacterial community structure was more connected and stable in Lime concretion black soil and Kallotenuales but not the predominant taxa were identified as kinless hub. However, Neisseriales, Anaerolineaceae and Nannocystaceae from Proteobacteria and Chloroflexi with higher relative abundance might support higher levels of ecosystem functions in Fluvo-aquic soil. Taken together, our results suggest that geographic distance and pH variation strongly shaped bacterial community structure with correspondingly diverse co-occurrence patterns observed in different soil pH ranges and types.
查看更多>>摘要：In agriculture, the use of soil biodegradable mulch films could represent an eco-friendly alternative to conventional plastic films. However, soil biodegradable mulch films incorporated into the soil through tillage, being not only a physical but also a biogeochemical input, is expected to influence the soil quality by affecting its functions. Therefore, the eco-compatibility of these biodegradable plastics needs to be evaluated for their impact on different soil functions. To understand the effect of biodegradable plastics on soil quality (i.e. microbial biomass, nitrogen cycle, and activity of soil enzymes involved in the biochemical processes of carbon and nitrogen), we added increasing quantities of biodegradable plastics in two different soils: a loamy (Cambisol) and sandy (Arenosol) soil. The results highlight that the carbon added through the biodegradable plastics influenced the processes linked to carbon and nitrogen cycles. Significant effects were observed mainly with the highest dose of biodegradable plastics added (1%), resulting in a higher growth of microbial biomass, increased carbon mineralisation, and increased immobilisation of available nitrogen. The results also underline the importance of evaluating the impact of biodegradable plastics in different soils because all the processes considered are also influenced also by soil physicochemical characteristics.
查看更多>>摘要：Despite the linkage of arbuscular mycorrhizal (AM) fungi to soil-plant interface, how changes in plant community-level traits and soil properties affect AM fungal communities under global changes remains largely unknown. Here, to investigate whether nitrogen (N) enrichment and altered precipitation can influence AM fungal communities through effects on plant community-level traits and soil properties, a six year-long factorial N and precipitation field experiment (N-addition rate: 10 g m(-2) year(-1) reduced precipitation by 50% and enhanced precipitation by 50%) was conducted in an alpine steppe of the Tibet Plateau. We observed that reduced precipitation decreased AM fungal diversities, while N enrichment decreased AM fungal biomass. Secondly, N enrichment and reduced precipitation shifted plant community composition from bunchgrass dominance (primarily Stipa purpurea) to rhizomatous grass dominance (primarily Leymus secalinus). N enrichment and reduced precipitation also led to a marked shift in AM fungal community composition. More specifically, reduced precipitation enhanced the relative abundance of the dominant taxa Glomus, while the relative abundance of Scutellospora and Diversispora was decreased. In contrast, N enrichment decreased the relative abundance of Scutellospora and Diversispora, while the relative abundance of Glomus was decreased. Structural equation models (SEMs) demonstrated that precipitation regime affected dominant AM fungal taxa via soil pH, while N enrichment affected dominant AM fungal taxa by changes in plant community-level traits. In addition, N-and precipitation-induced shifts in AM fungal community structure were significantly related to canopy photosynthetic rates and soil pH, indicating that canopy photosynthesis and soil pH may mediate the responses in AM fungal communities to enhanced N deposition and precipitation regime. Therefore, our findings may provide previously unidentified insights into N- and precipitation- evoked differential responses of AM fungal communities by linking plant community-level traits and soil properties.
查看更多>>摘要：Understanding the temporal changes of soil organic C (SOC) pools and microbial residues is essential for clarifying SOC dynamics in agmecosystems; however, this information remains largely unclear in greenhouse vegetable production (GVP) systems. Here, based on information of SOC pools (i.e., oxidizable organic C pools) and microbial residue C (MRC, as indicated by amino sugars differentiation), a 10-year (2009-2019) field experiment with fertilization was conducted to evaluate how fertilization alters SOC dynamics in a GVP field in Tianjin, China. The experiment includes four treatments (equal N, P2O5, and K2O inputs): 100% chemical N (N-100), 50% substitution of chemical N with manure-N (N50M50), straw-N (N50S50), and manure-N plus straw-N (N50M25S25). Results showed that the values of SOC, lability index, and C management index increased and decreased linearly with time in N50M50- and N-100-amended soils, respectively, which were mainly induced by the changes in labile C fractions. Based on logistic regression models, we found that these indices in straw-amended soils (N50M25S25 and N50S50) were rapidly increased between 2009 and 2013, and then approach steady levels between 2015 and 2019. These findings suggested that we should guarantee enough C inputs to maintain the level and quality of SOC, otherwise it will cause C loss in the unique GVP soils. Besides, straw-amended treatments increased MRC contents and enlarged their contributions to SOC sequestration, whereas these indices in N-100 treatment decreased linearly with the time of fertilization. In conclusion, long-term chemical application alone was not beneficial for SOC accumulation, whereas organic amendments brought several benefits for SOC sequestration in GVP soils. Our results implied that C sequestration in GVP soils is to a large extent determined by the amounts and time of fertilization.
Zubek, SzymonKapusta, PawelStanek, MalgorzataWoch, Marcin W....
10页
查看更多>>摘要：Reynoutria japonica (Japanese knotweed) is one of the most potent global invasive plant species; however, there is still insufficient knowledge on the impact of its invasion on arbuscular mycorrhizal fungi (AMF, Glomeromycota). The aim of our study was to assess the condition of AMF communities under the influence of R. japonica and determine the temporal and site-dependent variability of this influence. We studied AMF spore number, species richness, and composition as well as biomass in pairs of adjacent plots encompassing R. japonica and resident plant species. We established these pairs of plots in different habitat conditions (light and heavier soil conditions), and we sampled them four times (two spring and two summer seasons) to check if the potential impact of the invader on AMF communities is soil-and/or season-dependent. We found that the invasion reduced AMF spore number, species richness, and biomass, but had no effect on AMF species composition. AMF parameters varied over time (spore number, species composition and biomass) and depended on soil condition (species richness), but were barely affected by interactions between the studied factors. The lower performance of AMF communities in R. japonica plots was probably due to the displacement of resident mycorrhizal plant species. This displacement was not complete as some mycorrhizal plants, especially spring ephemerals, managed to survive the invasion. These were probably responsible for the maintenance of AMF communities in the patches of R. japonica. In conclusion, AMF communities are negatively affected by the invasion, but R. japonica does not entirely eliminate AMF, which is optimistic from the viewpoint of restoring sites invaded by this non-mycorrhizal alien plant species.
查看更多>>摘要：Ginseng root rot, caused by the soil-borne pathogenic fungi Fusarium solani (Fs) and Cylindrocarpon destructans (Cd), severely impacts the quality of ginseng. Despite economic losses due to ginseng root rot, the use of chemical and biological control agents to prevent this disease is apparently limited. Hence, in this study, we applied biochar to soil and monitored the effect of biochar on ginseng pathogens and diversity of soil microbiome, ultimately observing the effect of biochar on the survival of ginseng. Here we show that biochar exhibited high adsorption capacity toward radicicol and nutrients and increased the pH. This adsorption capacity and increased pH explained that biochar not only delayed conidial germination but also influenced normal mycelial growth of Fs and Cd. Biochar supplementation reduced the density of Fs and Cd in soil by 48% and 63%, respectively, and enriched the bacterial diversity in soil. Moreover, biochar supplementation to soil increased the survival rate of ginseng. The microbiota analyses suggested that biochar is a good candidate to manage ginseng root rot disease in ginseng fields and guaranties sustainable ginseng production.
NSTL
Elsevier