查看更多>>摘要：? 2022 Elsevier B.V.Tea tree pruning, an essential agronomic practice for maintaining the plant's table height, leads to the gradual accumulation of allelochemicals and accompanying changes in the physicochemical and biological properties of tea garden soils. The accumulated allelochemicals coupled with disturbance in the soil properties including soil microbiota gradually lead to ‘soil-sickness’ impeding the establishment of newly-planted tea saplings (replanting) and tea crop productivity. Although pruning is an essential and regular practice in tea management, its effect on the soil properties and the microbial populations is less understood. We used a metagenomics approach to decipher and compare the microbial community structure and functional characteristics in tea soils under pruning and non-pruning practices. Principal component analysis indicated the metagenomes of the two sample plots to be unique with key microbial taxa and metabolic pathways. The plot with pruned crops had significantly lesser microbial abundances and richness, but it harbored a relatively higher proportion of biologically important soil bacteria such as Pseudomonas, Candidatus Solibacter, Rhodopseudomonas and Nitrobacter. This indicated that a specific population and its associated soil functions play a significant role in plant growth and survival under stress conditions. The metabolic functions related to microbial growth and reproduction were prevalent in both metagenomes as revealed through the Kyoto Encyclopedia of Genes and Genomes (KEGGs) and Cluster of Orthologous Groups (COGs) analyses. The pruned-plot-metagenome contained six metabolic pathways linked to different stress-responsive metabolisms (starch, arginine and proline, pyrimidine, ribosome, and peroxisome). Although long-term pruning in tea plantations can decrease the microbial abundance, richness, and functions in soil, plants under these stress conditions may selectively encourage the growth and colonization of functionally-important microorganisms to aid in their survivability.
查看更多>>摘要：? 2022 The AuthorsClick beetle larvae (Elateridae), commonly known as wireworms are burrowing insects found commonly in many habitats. Some species can be a significant agricultural pest, reducing crop yields and quality of harvestable parts such as Agriotes spp. which are common in Europe and parts of North America. X-ray Computed Tomography (CT) has previously been demonstrated as a viable method for investigating wireworm interaction in soils with living plants. In this study, we used X-ray CT to visualise and quantify wireworms, their burrow networks and the root architecture of maize, barley and bare soil over a 96-hour time period order to monitor the typically cryptic behaviour of these organisms. Components within these CT scans were subsequently segmented and volume, size and complexity data collected. Wireworm burrow volume was significantly greater in bare soil compared to maize and barley planted columns, suggesting a behavioural difference in the wireworms elicited by the presence of root structures. Burrow volume was significantly greater at 96 h compared to 24 h. Burrow networks with maize were significantly shallower and less complex in structure compared to their barley and bare soil counterparts. Burrow network depth did not vary significantly over time. The presence and species of crop roots caused differences in wireworm behaviour, leading to variation in both the volume and structure of the burrow networks. Further work is needed to determine the specific type of behaviour of wireworms (e.g. random searching behaviour) and the mechanisms that influence it (e.g. CO2 and Volatile organic compound gradients).
查看更多>>摘要：? 2022 Elsevier B.V.The transition from the vegetative stage to reproductive stage of plants and variations in soil water regimes can alter the community feedbacks of rhizosphere microbiomes by affecting the partitioning of photosynthates to roots. However, little is known about how different rhizosphere microbiota respond to the growth stages of drought-resistant crops under different irrigation regimes. To address these issues, we investigated the effects of irrigation regimes on the rhizosphere prokaryotic and fungal communities at the pre- and post-anthesis stages of oats in a semi-arid region of northeastern China. The prokaryotic and fungal community traits of the oat rhizosphere were characterized by Illumina high-throughput sequencing. The results revealed that the prokaryotic diversity was primarily regulated by oat growth stage, while the fungal diversity was mainly increased by irrigation regimes. Similarly, all prokaryotic phyla responded significantly to oat growth stages rather than irrigation regimes, while the composition of the fungal taxa was largely regulated by irrigation regimes. Approximately 2–3-fold higher proportions of the predominating pathogenic Fusarium genus were identified under dryland farming conditions than under irrigation treatment. In addition, functional predictions suggested that the contrasting responsive traits of prokaryotes and fungi were attributed to their functional guilds, which were related to oat growth stages and soil water conditions. However, the properties of the prokaryotic networks mainly responded to irrigation regimes while the fungal networks were regulated by oat growth, implying distinct determination mechanisms for microbial diversity and community stability. Our results indicate that rhizosphere prokaryotic and fungal communities differentially responded to oat growth stages and soil water history, highlighting the significance of irrigation in manipulating rhizosphere microbes in semi-arid regions.
查看更多>>摘要：? 2022 Elsevier B.V.Earthworms stimulate organic nitrogen (N) mineralization and this is linked to plant N uptake and N loss from soil. Earthworms may also simultaneously transfer N-rich residues into physically protected soil fractions and temporarily increase N stabilization. This study evaluated soil N transformations and lettuce N uptake in soil microcosms amended with 15N-labeled rice straw, with and without earthworms (Metaphire guillelmi), during a 45-day period. We measured the amount of straw N absorbed by lettuce, lost as N2O or in leachates, and remaining in bulk soil and aggregate fractions. Lettuce biomass increased significantly (P < 0.05) by 37% with earthworms, and a greater proportion of the N uptake by lettuce was from the soil native N pool rather than from straw N (soil-derived N in lettuce increased from 101 to 170 mg pot?1 with earthworms). Earthworms did not change N losses by leaching. Total cumulative N2O emissions were 29% greater with earthworms than without earthworms (P < 0.05), but the straw-derived cumulative N2O emission was three times lower with earthworms than without earthworms. Straw N was recovered in large macroaggregates (> 2 mm) and earthworm tissues in the microcosms with earthworms. There was 4.5% more straw N remaining in soil with earthworms, suggesting that earthworms temporarily increased the residence time of straw N. We propose that M. guillelmi stimulates short-term mineralization of soil native N, which is available for uptake by lettuce and increases the risk of N loss as N2O, while temporarily stabilizing straw N in the soil.
查看更多>>摘要：? 2022 Elsevier B.V.Below-ground processes are crucial in determining the effects of plants on ecosystem function. The root-soil interface is a highly active zone due to root exudation and nutrient uptake. However, its role in determining effects of tree species and their interactions on the soil microbial community, ecosystem function and above-ground growth is less well known. We compared the effects of tree species monocultures and their mixture on rhizospheric microbial communities, specific functional genetic markers associated with processes in the nitrogen (N) cycle, and above-ground and below-ground growth and nutrient allocation. Two pairs of tree species were grown: Pseudotsuga menziesii and Alnus rubra; Acer pseudoplatanus and Quercus robur. Tree establishment altered soil microbial composition, but after 26 months differences amongst tree species and effects of species mixture were minor, suggesting functional redundancy in microbial communities. A greater abundance of fungi, bacteria, and specifically ammonia oxidising and denitrifying bacteria in the rhizospheric soil of the N-fixing A. rubra was the most notable trend. Mixing A. rubra with P. menziesii did produce overyielding: trees grown in mixture attained a two-fold greater (Relative Yield Total 2.03 ± 0.52) above-ground biomass than in a mixture predicted from trees grown in monoculture. We did not observe strong trends in overyielding for A. psuedoplatanus and Q. robur. Inclusion of the N-fixing species A. rubra in admixture with P. menziesii promoted N cycling, and decreased the C:N ratios of leaf, branch, and root tissues but not soil C:N ratio for P. menziesii. Given the observed overyielding in the A. rubra with P. menziesii mixtures, we explored potential mechanistic links between functional genetic markers for nitrification and ammonification, however we found no statistically significant effects attributable to these genetic markers. We found root area index was significantly lower in A. rubra monocultures than in admixture with P. menziesii. For both P. menziesii and A. rubra, the number of root tips was lower in mixture than monoculture, indicating physical partitioning of soil space as a result of growing in mixture. We documented additive and synergistic effects of tree species identity on above and belowground productivity, and rhizospheric microbial community development in these four tree species.
查看更多>>摘要：? 2022Piper aduncum, a tree species native to the Neotropics, has been introduced to other tropical regions and successfully invades secondary forest in fallow land after small scale slash-and-burn agriculture in Papua New Guinea (PNG). However, the effect of P. aduncum invasion on soil chemical properties as well as soil biota remains poorly understood. To fill this knowledge gap, we compared soil chemistry, soil microbiota and soil fauna between sites invaded by P. aduncum and sites with secondary native vegetation, where P. aduncum absent. Soils under P. aduncum had significantly lower P content at 0–5 cm depth, lower NO3? at 5–10 cm depth and lower N and C content at both depths compared to soil under secondary vegetation where P. aduncum absent. Sites invaded by P. aduncum also harbored lower microbial biomass measured by phospholipid fatty acid (PLFA) analysis, especially at 5–10 cm depth. The composition of microbial communities, based on PLFA and amplicon sequencing methods, also differed between soils invaded and uninvaded by P. aduncum, while soil macrofauna did not show any significant difference in the density of various faunal groups between invaded and uninvaded sites. Furthermore, we studied soil chemistry and foliar nitrogen in food gardens established after clearing of secondary vegetation in sites where P. aduncum had been experimentally excluded for five years. These gardens did not differ in soil chemistry compared to the control gardens where P. aduncum was not cleared. However, P. aduncum removal was associated with a higher N content in the leaves of sweet potatoes (Ipomoea batatas), but not bananas (Musa spp.). Our results suggest that P. aduncum has negative effect on soil microbiota and may slowdown nutrient turnover and availability as well as growth of plants on invaded soil. This finding requires further attention and may have practical implication for food gardening in tropical rainforests.
查看更多>>摘要：? 2022 Elsevier B.V.In acidic soil, potassium (K) deficiency is a main limiting factor that restricts the growth of fruit trees. Biochar has been used as a soil amendment to increase pH and nutrients. However, studies on the effect of biochar on the bacterial community and soil properties in potted experiments are limited. Therefore, we used peanut shell biochar to investigate the effect of biochar on the structure and function of bacterial communities by high-throughput sequencing, soil enzymes (urease, dehydrogenase, and extracellular enzymes), and gene function prediction in response to K deficiency in acidic soil. The results indicated that soil pH, enzyme activity, and available nutrients were improved by biochar. In particular, biochar still had a beneficial effect on improving soil and plant K levels after thirty months of application. In addition, biochar promoted the growth of K-dissolving bacteria and relative abundance of bacteria (p_actinomycetes, p_chloroflexi, p_proteobacteria, p_acidobacteriota, and p_firmicutes). Based on the above results, we assumed that biochar application can effectively improve soil K levels and bacterial functions. Such as: K-dissolving, soil organic matter decomposition and the conversion of nutrients. Our findings encourage and support the use of biochar as an amendment in acidic soil.
查看更多>>摘要：? 2022 The AuthorsPlant-parasitic nematodes (PPNs) are an important damaging biotic agent for numerous crops around the world, causing serious losses directly and indirectly. Cultural and chemical control strategies were mainly used to PPNs management. However, the choice of chemical nematicides is strictly limited in the agrosystems due to their toxicity, their impact to the environment and, therefore, banning policies. The main lines of action of biological control strategies for nematode control, are based on the development of antagonist microorganism formulations and the use of plant extracts with nematicidal potential. There are many plant secondary metabolites with effective nematicidal potential. In this sense, glucosinolates (GSLs) and, especially, glucosinolate hydrolysis products (GHPs) show relevant nematicidal activity. The effects through which these compounds control nematodes, both direct and indirect are diverse, such as toxicity, anti-hatching effect or promotion of competing saprophytic nematodes or nematophagous bacteria populations. The present work compiles many of the studies that describe the use of GSLs and GHPs as nematicides in agriculture, through very diverse strategies that range from crop rotation with Brassicales to the direct application of GSLs and GHPs to the soil. The authors present GSLs and GHPs as a more sustainable and suitable alternative in nematode control, remarking the need to further research in the modes of action and the impact on environment.
查看更多>>摘要：? 2022 Elsevier B.V.The aim of the present study was to detect the heterogeneity of diversity in seasonal, site, tree species, and soil properties' effects on structural and functional attributes of the nematode communities under smooth mesquite, Prosopis laevigata and palo brea, Cericidium praecox within the Biosphere Reserve Valle de Tehuacán-Cuicatlán. Soils under biological crusts and neighbouring exposed sites were surveyed during the dry and wet seasons of 2018. Assessment of effective diversity (D) and diversity weighted by metabolic footprint (DMFP) were calculated as they reflect taxonomic and functional diversity. Trophic group abundances and both indices showed marked seasonal variation. Soil water content and bulk density were the only physicochemical variables that showed seasonal variation whereas bulk density, total C and total N content showed significant variation between soil under biological crusts and exposed sites. DMFP seemed to have a better chance of explaining a relationship with physicochemical heterogeneity than D as shown by PCA analyses. This places DMFP as an index for measuring diversity related to ecosystem services and therefore should be used as a tool for biological integrity assessments at the soil level and a support aid in stewardship soil management policies.
查看更多>>摘要：? 2022 Elsevier B.V.Trichoderma is a genus of fungi used for biocontrol and plant growth promotion; however, effects of co-inoculation with rhizobia in legumes still require detailed analysis. This study conducted a global meta-analysis of 59 published studies (1992–2021) on co-inoculation of legumes with rhizobia and Trichoderma spp. to assess factors affecting the efficiency of plant growth compared to inoculation exclusively with rhizobia. Co-inoculation favored plants by reducing disease incidence (?44%) and increasing root mass (+17%), nodule number (+32%), nodule mass (+37%), nodule nitrogenase activity (+35%), shoot nitrogen content (+8%), and grain yield (+14%). Co-inoculation of legumes can decrease root diseases caused by Fusarium spp., Rhizoctonia spp., Macrophomina phaseolina, Pythium debaryanum and Sclerotium rolfsii and also has potential as a plant growth promoter regardless of plant health. Positive effects of co-inoculation on grain yield and root mass were observed under the majority of the factors evaluated (e.g., legume species, microorganisms, co-inoculation methods, experimental conditions, plant health status, and edaphic factors). Co-inoculation with rhizobia and Trichoderma spp. may contribute to sustainable intensification of legume production systems due to multiple plant benefits under a wide range of conditions.
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