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1.
Abstract

The choice of prospective type of farming requires knowledge about the specific relationships that exist between farm management practices and base environmental conditions. Nowadays the protection of soil organic carbon is one of the main tasks, because organic carbon in addition to soil fertility can act in elimination of soil contamination and carbon sequestration. Field experiments were focused on the effect of intensive farming without organic inputs versus grassland on organic carbon content. Organic carbon content (Cox) and humic substance fractions (C-humic acids and fulvic acid fractions), hot water extractable carbon and selected microbial characteristics in Eutric Cambisol were monitored during the period 1999–2010. A priming effect of soil cultivation was detected immediately after tillage. Arable soil with ‘intensive’ crop sequences (exclusively cash crops, cereals, oil plants) and with an optimal level of chemical inputs (mineral fertilizers, pesticides), but without organic farmyard manure had lower content of all carbon forms compared with grassland. 13C NMR spectroscopy and thermal analysis (TGA) were applied to characterize humic acid (HA) structure and stability. More carbon, less oxygen and more aromatic compounds were detected in grassland HA. Slight differences were found in HA thermo-oxidative stability and degradability, which was probably caused by changes in elemental composition and structure. Even the land use had no significant effect on basic microbiological characteristics (basal respiration, microbial biomass and qCO2); the physiology of the microbial community of grassland was altered by a higher ability to utilize L- and D-glutamic acid. The L/D ratio of glutamic acid mineralization indicated no occurrence of stress in soil for both types of farming. It has been demonstrated that although losses of carbon as a result of land-use conversions are generally more rapid, gains of carbon in grassland followed by changes in management practices can also occur.  相似文献   

2.
The organic compounds released from roots (rhizodeposits) stimulate the growth of the rhizosphere microbial community. They may be responsible for the differences in the structure of the microbial communities commonly observed between the rhizosphere and the bulk soil. Rhizodeposits consists of a broad range of compounds including root mucilage. The aim of this study was to investigate if additions of maize root mucilage, at a rate of 70 μg C g−1 day−1 for 15 days, to an agricultural soil could affect the structure of the bacterial community. Mucilage additions moderately increased microbial C (+23% increase relative to control), which suggests that the turnover rate of microorganisms consuming this substrate was high. Consistent with this, the number of cultivable bacteria was enhanced by +450%. Catabolic (Biolog® GN2) and 16S-23S intergenic spacer fingerprints exhibited significant differences between control and mucilage treatments. These data indicate that mucilage can affect both the metabolic and genetic structure of the bacterial community as shown by a greater catabolic potential for carbohydrates. We concluded that mucilage is likely to significantly contribute to differences in the structure of the bacterial communities present in the rhizosphere compared to the bulk soil.  相似文献   

3.
Monitoring the environmental impact of anthropogenic disturbance on soil ecosystem is of great importance for optimizing strategies for soil use, conservation and remediation. The aim of this study was to assess whether and to what extent a long-term, human-induced disturbance could have affected main chemical and biological properties in an agricultural soil. The study site was a hazel (Corylus avellana L.) orchard located in the area surrounding the volcanic apparatus of Somma-Vesuvius (Southern Italy). For the last two decades, the site has been repeatedly subjected to floodings by wastewaters containing not only alluvial sediments but also potentially hazardous compounds from illegally disposed wastes. Soil disturbance was assessed by a multitechnique approach, which combined chemical, biochemical and physiological (Biolog®) methods together with community fingerprinting by denaturing gradient gel electrophoresis (DGGE) and amplified ribosomal DNA restriction analysis (ARDRA). A hazel site never subjected to flooding provided the control soil. Soil sampling was repeated three times over a 1-year period. The effect of flooding by wastewaters, sampling time and their interaction were statistically evaluated. Under wastewater flooding, soil pH and most organic matter-related pools, i.e. total organic C, total N, and active soil C-resources such as basal (SBR) and substrate-induced respiration (SIR) and microbial biomass C (MBC) were all increased; whereas sampling time mostly affected two active-N pools, namely K2SO4-extractable N (Extr-N) and potentially mineralizable N that varied unconcurrently in tested soils. Also the electrical conductivity varied across samplings. Parameters related to microbial maintenance energy (ATP and qCO2) were higher in the flooded soil, even though they were not statistically affected by wastewater flooding or by sampling time. The Biolog® method evidenced that under recurrent flooding, soil microbial populations became functionally more uniform when compared to the control soil. Molecular fingerprinting of PCR-amplified 16S rDNA targets revealed that, along with seasonal shifts, a marked change in the genetic structure of total bacterial community occurred in the flooded soil. Furthermore, compositional shifts in the actinomycete community were less marked and mostly influenced by seasonal effects. Yet, a decreased genetic diversity in the ammonia-oxidizing bacteria community was evidenced in the flooded soil by ARDRA. Thus both the genetic and the functional structure of native soil bacterial populations were changed under repeated flooding by wastewaters. Repeated sampling over a 1-year period allowed us to reveal soil disturbance effects beyond seasonal variations.  相似文献   

4.
The aim of this study was to evaluate the long-term influence of contrasting rural land use types on the level, plot-scale variation and horizontal spatial structure of decomposition activities and the bacterial community in soil. Experimental data were collected in the southern boreal zone from topsoil layers of adjacent spruce forest, unmanaged meadow (former field) and organically cultivated field that all shared the same soil origin. The forest soil was sampled separately for the organic and mineral layers. A geostatistical design comprising 50 sampling points per plot area of 10 × 10 m2 was used. The measured microbiological characteristics included eight different hydrolytic soil enzyme activities involved in C, P and S cycles, bacterial 16S rDNA length heterogeneity profiles (LH-PCR) and total DNA yield as a relative estimate of microbial biomass.Effects of land use were pronounced on both the bacterial community structure and soil enzyme activities. Soil organic matter (SOM) content predicted well the major differences in soil enzyme activities and microbial biomass. Highest enzyme activities were generally found in the forest organic soil whereas the underlying mineral soil showed significantly lower activities with a pattern similar to those of the other mineral soils, especially the cultivated field. Bacterial LH-PCR fingerprints were distinct but at the same time remarkably similar between field and meadow soils whereas the forest organic layer differed clearly from the mineral soils. Within-plot variation of soil microbiological characteristics was best explained by the variation of SOM. Relative standard deviations of soil microbiological characteristics typically decreased in the order: forest organic layer ≈ forest mineral layer > meadow > field. However, bacterial fingerprints showed lowest variation within the meadow. Most of the microbiological variables studied showed no or only weak spatial structure at the scale sampled.  相似文献   

5.
《Applied soil ecology》2007,35(1):79-93
Microbial diversity in soils is considered important for maintaining sustainability of agricultural production systems. However, the links between microbial diversity and ecosystem processes are not well understood. This study was designed to gain better understanding of the effects of short-term management practices on the microbial community and how changes in the microbial community affect key soil processes. The effects of different forms of nitrogen (N) on soil biology and N dynamics was determined in two soils with organic and conventional management histories that varied in soil microbial properties but had the same fertility. The soils were amended with equal amounts of N (100 kg ha−1) in organic (lupin, Lupinus angustifolius L.) and mineral form (urea), respectively. Over a 91-day period, microbial biomass C and N, dehydrogenase enzyme activity, community structure of pseudomondas (sensu stricto), actinomycetes and α proteobacteria (by denaturing gradient gel electrophoresis (DGGE) following PCR amplification of 16S rDNA fragments) and N mineralisation were measured. Lupin amendment resulted in a two- to five-fold increase in microbial biomass and enzyme activity, while these parameters did not differ significantly between the urea and control treatments. The PCR–DGGE analysis showed that the addition of mineral and organic compounds had an influence on the microbial community composition in the short term (up to 10 days) but the effects were not sustained over the 91-day incubation period. Microbial community structure was strongly influenced by the presence or lack of substrate, while the type of amendment (organic or mineral) had an effect on microbial biomass size and activity. These findings show that the addition of green manures improved soil biology by increasing microbial biomass and activity irrespective of management history, that no direct relationship existed among microbial structure, enzyme activity and N mineralisation, and that microbial community structure (by PCR–DGGE) was more strongly influenced by inherent soil and environmental factors than by short-term management practices.  相似文献   

6.
 We used polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) to compare bacterial community patterns obtained with target DNA extracted from a soil by direct and indirect methods. For this purpose, two direct extraction methods, i.e. cell lysis by bead beating and cell disruption by grinding in liquid N, and two indirect methods, i.e. cell extraction followed by DNA extraction, and combined RNA/DNA extraction from the bacterial cell fraction, were performed. Crude extracts were purified and amplified using universal bacterial primers. PCR products were then analysed by DGGE, and similarity between the profiles obtained was determined by unweighted pair group with mathematical averages clustering. The results showed clear profiles that presumably represented the dominant bacterial fractions in the samples. The profiles generated by all four methods were similar, indicating that the methods were of approximately equal efficiency in the extraction of target DNA representative of the soil bacterial community. However, the patterns of clustering also indicated that different populations of bacteria could be detected in the same soil using different soil DNA extraction methods. The application of two dilution levels of DNA in PCR-DGGE showed that the most stable profile of the soil bacterial community could be generated by the direct methods. The indirect methods gave clustered profiles at both dilution levels. It is likely that these methods extracted DNA from a major, easily desorbed, bacterial fraction, consisting of low-density populations. PCR-DGGE was found to be a suitable technique with which to assess differences in methods for DNA extraction from soil, which can be further used for the determination of microbial community diversity at the molecular level. Received: 22 June 1999  相似文献   

7.
We conducted a laboratory incubation of forest (Scots pine (Pinus sylvestris) or beech (Fagus sylvatica)), grassland (Trifolium repens/Lolium perenne) and arable (organic and conventional) soils at 5 and 25 °C. We aimed to clarify the mechanisms of short-term (2-weeks) nitrogen (N) cycling processes and microbial community composition in relation to dissolved organic carbon (DOC) and N (DON) availability and selected soil properties. N cycling was measured by 15N pool dilution and microbial community composition by denaturing gradient gel electrophoresis (DGGE), phospholipid fatty acid (PLFA) and community level physiological profiles (CLPP). Soil DOC increased in the order of arable<grassland<forest soil while DON and gross N fluxes increased in the order of forest<arable<grassland soil; land use had no affect on respiration rate. Soil DOC was lower, while respiration, DON and gross N fluxes were higher at 25 than 5 °C. Gross N fluxes, respiration and bacterial biomass were all positively correlated with each other. Gross N fluxes were positively correlated with pH and DON, and negatively correlated with organic matter, fungal biomass, DOC and DOC/DON ratio. Respiration rate was positively correlated with bacterial biomass, DON and DOC/DON ratio. Multiple linear modelling indicated that soil pH, organic matter, bacterial biomass, DON and DOC/DON ratio were important in predicting gross N mineralization. Incubation temperature, pH and total-C were important in predicting gross nitrification, while gross N mineralization, gross nitrification and pH were important in predicting gross N immobilization. Permutation multivariate analysis of variance indicated that DGGE, CLPP and PLFA profiles were all significantly (P<0.05) affected by land use and incubation temperature. Multivariate regressions indicated that incubation temperature, pH and organic matter content were important in predicting DGGE, CLPP and PLFA profiles. PLFA and CLPP were also related to DON, DOC, ammonium and nitrate contents. Canonical correlation analysis showed that PLFA and CLPP were related to differences in the rates of gross N mineralization, gross nitrification and soil respiration. Our study indicates that vegetation type and/or management practices which control soil pH and mediate dissolved organic matter availability were important predictors of gross N fluxes and microbial composition in this short-term experiment.  相似文献   

8.
Key physicochemical factors associated with microbial community composition and functions in Australian agricultural soils were identified. Soils from seven field sites, with varying long-term agricultural management regimes, were characterised physicochemically, on the basis of their bacterial and fungal community structures (using PCR-DGGE), and by assessing potential catabolic functions (MicroResp?). Soil type, rather than agricultural management practice, was the key determinant of microbial community structure and catabolic function (P<0.05). Following multivariate analysis, soil pH was identified as the key habitat-selective physicochemical soil property associated with variation in biological diversity and profiles of organic substrate utilisation. In particular, the capacity of soils to catabolise different C-substrates was closely correlated (ρ=0.604, P=0.001) to pH. With decreasing pH, the catabolism of common low molecular weight organic compounds (especially cysteine and aspartic acid) declined, however catabolism of two others (lysine and arginine) increased. Shifts in the capacity of soil microbiota to cycle common organic compounds have implications for overall geochemical cycling of C and N in acidifying soils. The genetic structure of the bacterial communities in soil strongly correlated with pH (ρ=0.722; P=0.001) and that of soil fungi with pH and % sand (ρ=0.323; P=0.006). Catabolic function was more closely associated with the structure of the bacterial than fungal communities. This work has shown that soil pH is a primary driver of microbial diversity and function in soil. Agricultural management practices thereby act to selectively shift populations and functions against this background.  相似文献   

9.
Abstract

In this study, two fields of temperate Andisols from high‐input and low‐input (zero‐input) management practices of an apple orchard were selected to assess microbial community dynamics based on environmental variables. Soils from an Ap horizon were sampled in five consecutive months from May to September and assessed for phospholipid fatty acids as a biomarker of soil microbial community, soil hardness, bulk density, porosity, pH, electrical conductivity (EC), organic carbon (C), available nitrogen (N) and phosphorus (P), and exchangeable cations as soil environmental variables. For all sample dates, total phospholipid fatty acids (PLFAs), total bacterial PLFAs, fungal PLFA, mycorrhizal PLFA, PLFA for actinomycetes, and earthworm were higher in low‐input management than high‐input management. Total PLFAs showed a high degree of seasonality, having August maxima and May minima. Significant effect on the relationships among soil environmental variables and microbiological attributes were observed. Soil management practices also showed a remarkable effect on the relationships among microbiological traits, indicating that some mechanism regulated soil microbial dynamics under two soil management practices. Comparatively higher correlations among the microbiological attributes were observed in low‐input management than high‐input management. Irrespective of soil management practices, bacterial and fungal lipid biomarkers were negatively correlated, suggesting that these subsets of fatty acids are contrasting components of the microbial biomass. Bulk density has negative influence on all soil microbial communities except fungi. On the other hand, linoleic acid and organic C were positively correlated, referring to the distribution of soil organic C implying an upper layer of soils. Microbial community composition and structure were greatly affected by sampling date and to a lesser extent by long‐term management practice. In this study, both ecosystems were characterized by a very diverse microbial community.  相似文献   

10.
A 13C natural abundance experiment including GC-c-IRMS analysis of phospholipid fatty acids (PLFAs) was conducted to assess the temporal dynamics of the soil microbial community and carbon incorporation during the mineralization of plant residues under the impact of heavy metals and acid rain. Maize straw was incorporated into (i) control soil, (ii) soil irrigated with acid rain, (iii) soil amended with heavy metal-polluted filter dust and (iv) soil with both, heavy metal and acid rain treatment, over a period of 74 weeks. The mineralization of maize straw carbon was significantly reduced by heavy metal impact. Reduced mineralization rate of the added carbon likely resulted from a reduction of the microbial biomass due to heavy metal stress, while the efficiency of 13C incorporation into microbial PLFAs was hardly affected. Since acid rain did not significantly change soil pH, little impact on soil microorganisms and mineralization rate was found. Temporal dynamics of labelling of microbial PLFAs were different between bacterial and fungal PLFA biomarkers. Utilization of maize straw by bacterial PLFAs peaked immediately after the application (2 weeks), while labelling of the fungal biomarker 18:2ω6,9 was most pronounced 5 weeks after the application. In general, 13C labelling of microbial PLFAs was closely linked to the amounts of maize carbon present in the soil. The distinct higher labelling of microbial PLFAs in the heavy metal-polluted soils 74 weeks after application indicated a large fraction of available maize straw carbon still present in the soil.  相似文献   

11.
Various parameters of the soil microbial community may be used in soil quality evaluation and environmental risk assessment. The objectives of this study were to assess the effects of different environmental factors on the characteristics of forest humus microbial communities, and to test which environmental factors most affect the gross microbial indices and physiological profiles of these communities. Samples were taken at 71 plots located in a heavily polluted area of the Krakowsko-Cze¸stochowska upland in southern Poland. The samples were analyzed for pH in KCl (pHKCl), organic C (Corg), total N (Nt) and S (St), and for total and soluble Zn, Pb and Cd concentrations. The considered microbial parameters included basal respiration (BAS), microbial biomass (Cmic), Cmic-to-Corg ratio, and community-level physiological profiles (CLPPs) studied using BIOLOG® Ecoplates. Multiple regression analysis was used to estimate the effects of humus properties on the microbial parameters. It indicated that St and Corg-to-Nt ratio were the most important factors positively affecting Cmic (β=0.15 and 0.11, respectively) and BAS (β=0.13 and 0.08, respectively). The Cmic-to-Corg ratio was related positively to St (β=0.12) but negatively to Nt (β=−0.08). The effects of pHKCl and heavy metals on the gross microbial indices were significant but less important. The most important effect on microbial activity on BIOLOG® plates and CLPPs was from pHKCl. The other significant variables included St, Corg-to-Nt and interactions of heavy metals with pHKCl. It was concluded that Cmic, Cmic-to-Corg and BAS might be good indicators of the general status of soil microbial communities, but their use in studying heavy metal effects may entail difficulties in separating the effects of other factors. The sensitivity of the BIOLOG® test to pHKCl suggests that it may be useful for studying the effects of acidification or liming on soil microbial communities. The significant effect of the interactions between heavy metals and other variables on physiological profiles indicated that high heavy metal content affects the metabolic functions of soil microbial populations.  相似文献   

12.
Using a scheme of agricultural fields with progressively less intensive management （deintensification）, different management practices in six agroecosystems located near Goldsboro, NC, USA were tested in a large-scale experiment, including two cash-grain cropping systems employing either tillage （CT） or no-tillage （NT）, an organic farming system （OR）, an integrated cropping system with animals （IN）, a successional field （SU）, and a plantation woodlot （WO）. Microbial phospholipid fatty acid （PLFA） profiles and substrate utilization patterns （BIOLOG ECO plates） were measured to examine the effects of deintensification on the structure and diversity of soil microbial communities. Principle component analyses of PLFA and BIOLOG data showed that the microbial community structure diverged among the soils of the six systems.Lower microbial diversity was found in lowly managed ecosystem than that in intensive and moderately managed agroecosystems, and both fungal contribution to the total identified PLFAs and the ratio of microbial biomass C/N increased along with agricultural deintensification. Significantly higher ratios of C/N （P 〈 0.05） were found in the WO and SU systems, and for fungal/bacterial PLFAs in the WO system （P 〈 0.05）. There were also significant decreases （P 〈 0.05） along with agricultural deintensification for contributions of total bacterial and gram positive （G＋） bacterial PLFAs.Agricultural deintensification could facilitate the development of microbial communities that favor soil fungi over bacteria.  相似文献   

13.
国内首次运用FastPrep○R 核酸快速提取系统提取了重金属复合污染农田土壤的DNA ,并对其进行了聚合酶链反应—变性梯度凝胶电泳 (PCR DGGE)分析。结果表明 ,FastPrep○R核酸提取仪与相应的FastD NASPINKitforSoil试剂盒联用时 ,能有效地分离到纯度较高的重金属污染农田土壤的DNA。PCR DGGE电泳图谱表明 ,PCR产物经DGGE检测后得到的电泳条带清晰且分离效果好 ,可以明显反映出重金属复合污染导致了农田土壤微生物在基因上的损伤 ,影响到农田土壤生态系统的细菌丰富度 ,改变了土壤环境的优势菌群 ,从而使农田土壤微生物群落结构多样性发生变化。可见 ,FastPrep○R核酸提取系统同样适用于重金属污染农田土壤环境中微生物基因组DNA的快速分离和纯化 ,得到的DNA可直接用于PCR DGGE分析。  相似文献   

14.
《Soil biology & biochemistry》2001,33(4-5):679-682
Accelerated biodegradation of organic contaminants in planted soil is frequently reported yet our current understanding of plant–microbe interactions does not allow us to predict which plant species can encourage the development of rhizosphere communities with enhanced degradation capacity. In a companion study, five grass species (Sudan grass, ryegrass, tall fescue, crested wheatgrass, and switch grass) were grown in a Matapeake silt loam soil to study the degradation of atrazine and phenanthrene by rhizosphere microorganisms (see Fang et al., 2000, this vol., Fang, C., Radosevich, M., Fuhrmann, J. J., 2000. Atrizine and phenanthrene degradation in grass rhizosphere soil. Soil Biology & Biochemistry, in press). In the present paper substrate utilization patterns (BIOLOG®), and fatty acid methyl ester (FAME) profiles of the same rhizosphere microbial communities were determined. Both FAME and BIOLOG® analyses detected changes in soil microbial community structure among treatments. However, community structure did not directly correlate to either ATR or PHE degradation rates.  相似文献   

15.
菌肥对青稞根际土壤理化性质以及微生物群落的影响   总被引：6，自引：0，他引：6  
应用化学分析、聚合酶链反应-变性梯度凝胶电泳(PCR-DGGE)技术和DNA测序技术,研究了西藏棕色砂壤土中微生物肥料不同施用量和施用期对青稞根际土壤理化性质和细菌群落多样性的影响。结果表明,施用谷特菌肥能显著提高土壤全氮、全磷、全钾、有机质、碱解氮、有效磷和速效钾的水平,如播前施用菌肥浓度750 ml hm-2的处理较不施用菌肥的处理上述指标分别提高13.32%、28.42%、16.20%、9.81%、21.36%、39.35%和30.48%,拔节期施用菌肥浓度2 250 ml hm-2的处理较不施用菌肥的处理分别提高7.25%、29.35%、18.04%、12.86%、15.90%、43.27%和53.99%。DGGE分析表明,相同施用方式中不同施用量土样中微生物的DGGE图谱相似。非加权组平均法(UPGMA)聚类分析将DGGE图谱分为2大类群。Shannon-Wiener指数表明,施用菌肥的土壤细菌多样性先增加后逐渐降低,播前以喷施谷特菌浓度750 ml hm-2时的细菌多样性最高;拔节期则以喷施谷特菌浓度2 250 ml hm-2处理的细菌多样性最高,且两种施用方式土壤养分的释放与Shannon指数的变化规律均为播前﹥拔节期。测序结果表明,不同施肥浓度土样微生物种群分布较为广泛,其中Actinobacteria纲细菌种类略多,少数菌种为未经培养菌种(Uncultured bacterium)。典型对应分析(CCA)表明,DGGE图谱条带分布与土壤理化性质密切相关,碱解氮、全磷和全氮是影响微生物群落的主要环境因子。研究结果表明,施用谷特菌肥可明显改善青稞根际土壤理化性状,提高土壤细菌多样性。  相似文献   

16.
Organic matter incorporation into soil can increase nutrient availability to plants but it can affect soil microbial communities. These in turn influence soil fertility and plant growth. Soil biochemical and microbiological properties are indicators of soil quality, but there is still no consensus as to how these should be used. Recent developments in molecular biology have provided new tools to obtain a view of the whole microbial community. The long-term impact of crop residue management on the microbial biomass, and on the activity and community structure of soil bacteria was evaluated in a clay soil of Southern Italy, where a monoculture of durum wheat (Triticum durum Desf.) was grown in semiarid conditions, and burning or incorporation of post harvest plant residues were typical practices. The role of N-mineral fertilization, simultaneously with the ploughing in of crop residues and during the plant growth cycle was also investigated. Total bacterial counts of viable cells, biomass C, ATP content of soil microorganisms, genetic fingerprinting of the total eubacterial community and of ammonia oxidizers were evaluated. Burning and incorporation did not affect microbial biomass C, ATP content, and total bacterial counts of viable cells although statistically relevant changes were detected among rhizosphere and bulk soil samples regardless of the crop residue management used. Molecular fingerprinting confirmed that: no significant change in the composition and diversity of total bacteria, as well as of ammonia oxidizers was induced by the crop residue managements; that soil bacteria were more sensitive to N fertilizer application during the plant growth cycle; and that rhizosphere soil samples were significantly different from those of the bulk soil. As microbiological and genetic factors related to soil fertility were not affected significantly, the long-term incorporation of crop residues, under the field conditions investigated, is a sustainable practice to manage post-harvest residues.  相似文献   

17.
Soil in short-term crop rotation systems (STCR) is still in the initial development stage of farmland soil, whereas after long-term crop rotation treatment (LTCR), soil properties are significantly different. This study compares STCR (4 years) and LTCR (30 years) rice-rice-fallow, rice-rice-rape rotation practices under the same soil type background and management system. To reveal ecosystem mechanisms within soils and their effects on rice yield following LTCR, we analyzed the physical, chemical, and microbiological properties of soils with different rotations and rotation times. Relative to STCR, LTCR significantly reduced soil water-stable aggregate (WSA) content in the <?0.053-mm range, while >?2 mm WSA content significantly increased. Soil organic matter increased in fields under LTCR, mainly in >?2 mm, 2–0.25 mm, and <?0.053 mm soil WSA in 0–10 cm soil layer. LTCR was associated with significantly increased total soil organic matter, at the same time being associated with increasing the amount of active organic matter in the 0–20 cm soil layer. The two crop rotation regimes significantly differed in soil aggregate composition as well as in soil N and P, microbial biomass, and community composition. Relative to STCR, LTCR field soils had significantly higher soil organic matter, active organic matter content, soil enzyme activities, and overall microbial biomass, while soil WSA and microbial community composition was significantly different. Our results demonstrate that LTCR could significantly improve soil quality and rice yield and suggest that length of rotation time and rice-rice-rape rotation are critical factors for the development of green agriculture.  相似文献   

18.
This research attempted to investigate a part of the United Nations sustainable development goal 15, dealing with preventing land degradation and halting the loss of microorganisms’ diversity. Since soil deterioration and biodiversity loss in the Mediterranean area are occurring because of intensive management, we evaluated some biochemical and microbiological parameters and bacterial biodiversity under long-term conventional tillage (CT) and no-tillage (NT) practices, in Basilicata, a typical Region of Southern Italy, characterized by a semiarid ecosystem. The highest biological fertility index (BFI) (composed of soil organic matter, microbial biomass C, cumulative microbial respiration during 25 days of incubation, basal respiration, metabolic quotient and mineralization quotient) was determined for the 0–20 cm of NT soil (class V, high biological fertility level). The analysis of the taxonomic composition at the phylum level revealed the higher relative abundance of copiotrophic bacteria such as Proteobacteria, Actinobacteria and Bacteroidetes in the NT soil samples as compared to the CT soil. These copiotrophic phyla, more important decomposers of soil organic matter (SOM) than oligotrophic phyla, are responsible of a higher microbial C use efficiency (CUE) in tilled soil, being microbial community composition, C substrates content and CUE closely linked. The higher Chao1 and Shannon indices, under the NT management, also supported the hypothesis that the bacterial diversity and richness increased in the no-till soils. In conclusion, we can assume that the long-term no-tillage can preserve an agricultural soil in a semiarid ecosystem, enhancing soil biological fertility level and bacterial diversity.  相似文献   

19.
The daily dynamics of the number of copiotrophic and oligotrophic bacteria (in colony-forming units) and CO2 emissions from cultivated soils after short- and long-term disturbances were studied for 25–27 days in a microfield experiment. The relationship of the wavelike fluctuations of the bacterial number and CO2 emission with the succession of the soil microbial community was determined by the polymerase chain reaction method—denaturing gradient gel electrophoresis (PCR-DGGE). Short-term disturbances involved the application of organic or mineral fertilizers, pesticides, and plant residues to the soils of different plots. The long-term effect was a result of using biological and intensive farming systems for three years. The short-term disturbances resulted in increased peaks of the bacterial number, the significance of which was confirmed by harmonics analysis. The daily dynamics of the structure of the soil microbial community, which was studied for 27 days by the DGGE method, also had an oscillatory pattern. Statistical processing of the data (principal components analysis, harmonics and cross-correlation analyses) has revealed significant fluctuations in the structure of microbial communities coinciding with those of the bacterial populations. The structure of the microbial community changed within each peak of the dynamics of the bacterial number (but not from peak to peak), pointing to the cyclical character of the short-term succession. The long-term effects resulted in a less intense response of the microbiota—a lower rate of CO2 emission from the soil cultivated according to the organic farming system.  相似文献   

20.
To clarify the variation in soil microbial respiration (SMR) in Jiuduansha wetland during different succession stages, the SMR of five typical zones was evaluated. The results showed that the SMR during different successional stages of vegetation varied significantly (P < 0.05), with the SMR of the Spartina alterniflora zone (0.43 mg CO2 g−1 d−1) being the highest. These findings implied that S. alterniflora could enhance the SMR. Based on both the SMR and input of organic matter from plant decomposition, the Phragmites australis community likely possesses a higher organic carbon accumulation capability. In addition, the results of the present study implied that the difference in microbial characteristics among the wetland soils may be the primary reason for their different SMR. Path analysis indicated that the correlation between soil bacterial diversity and SMR was especially strong. Moreover, phylogenetic analysis showed that the bacterial community structure along the successional stages varied. Specifically, microbial species such as Acidobacteria, δ-Proteobacteria and Cytophaga belonging to Bacteroidetes, which have special heterotrophic metabolic capabilities or the ability to degrade cellulose, were the dominant soil bacterial flora in the S. alterniflora zone, which ultimately strengthened the SMR. Different elevations and vegetation types leading to a change in the wetland soil characteristics such as waterlogging time and inorganic nitrogen may be important factors resulting in the differences in soil microbial characteristics of different successional stages in Jiuduansha wetland.  相似文献   

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