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1.
A comprehensive comparison about microbial community (bacterial, archaeal and fungal) response to different tillage managements in Northern China remain little studied, in this study we compared no-tillage (NT) versus conventional tillage (CT) management on topsoil microbial community diversity and composition in field experiment. We found that NT practice significantly increased the soil moisture content (SMC), bulk density, stocks of soil organic carbon (SOC), total nitrogen (TN), and microbial biomass carbon and nitrogen (P < 0.05). Moreover, higher levels of bacterial and archaeal alpha diversity were observed in NT relative to CT while unexpectedly, there was no significant difference found in fungal diversity between two treatments. The most pronounced shifts in the composition of the different microbial groups were found for the archaeal community, which followed by bacterial and fungal. NT practice markedly enhanced abundances of Proteobacteria (belongs to bacteria) phyla, Thaumarchaeota phyla (belongs to archaea) and Glomeromycota phyla (belongs to fungi). Redundancy analysis revealed that the factor that most closely correlated with bacterial, archaeal and fungal composition were SMC, TN and SOC, respectively. Considering NT enhanced both microbial composition and C storage in topsoil, we suggest that NT offers significant promise to improve topsoil health in this region.  相似文献   

2.
A 3‐year field tillage and residue management experiment established in North China was used to analyse topsoil (0–15 cm) aggregation, and microbial functional diversity, enzyme activity and glomalin‐related soil protein (GRSP) content within aggregates. Compared with conventional tillage (CT), no‐tillage (NT) alone significantly (P < 0.05) increased organic C contents in 50–250 and <2 μm aggregates and decreased the proportion of C accumulated by 2–50 μm aggregates and microbial functional diversity indices in <2 μm aggregates. Regardless of tillage practice, both half‐amount (C50) and full (C100) residue retention tended to increase organic C and GRSP contents, or dehydrogenase and invertase activities, in certain aggregates. Under CT, a poorer performance of C50 than C100 was observed in maintaining Shannon index (H′) and Simpson index (D) in >250 and <2 μm aggregates, and also McIntosh index (U) in <2 μm aggregates, owing to insufficient residue and possible decreases in the distribution of decomposer micro‐organisms. Under NT, however, C50 was more effective than C100 in maintaining/elevating H′, D and U in all soil aggregates except for 50–250 μm, suggesting that surplus residue may induce worse soil conditions, decreasing heterotrophic microbial activities. Thus, NT with half‐amount residue retention improved soil physical–chemical–biological properties and could be a useful management practice in North China.  相似文献   

3.
The effect of long-term (45 years) mineral and organic fertilization on soil organic matter (SOM) quantity (organic C and N content) and quality (hot-water-soluble C content, microbial biomass C content, hydrophobic organic components of SOM, soil enzyme activities) was determined in a field experiment established in Trutnov (North Bohemia, sandy loam, Eutric Cambisol). Six treatments were chosen for investigation: unfertilized control, mineral fertilization (NPK), straw N, farmyard manure (FYM) and straw and FYM completed with mineral NPK. Soil samples were taken from the arable layer (0–20 cm) in spring over the period of 2004–2010. The positive effect of FYM on the total organic C and N content, hot-water-soluble C content and hydrophobic organic components of SOM was more than 50% higher than that of straw and mineral N fertilization. Application of straw N increased microbial biomass C content in soil and generated invertase activity above the level of FYM. Hot-water-soluble C content, hydrophobic organic components of SOM and urease activity were positively correlated with total organic C and N content (R = 0.58–0.98; p < 0.05). Addition of mineral NPK to both the straw and FYM emphasized the effect of organic fertilization in most of monitored characteristics.  相似文献   

4.
The dynamics of soil organic carbon (SOC) is imperative for maintaining soil quality. Our objective was to investigate the effects of tillage practices on SOC and its fractions at the depth (0–60 cm) of Chromic Cambisol profile in northern China. The experiment including no-tillage with straw mulch (NTSM) and conventional tillage (CT). Our results indicated that differences in SOC concentration and stock were primarily evident in the 0–10 cm layer. The particulate organic matter carbon (POM-C), dissolved organic carbon (DOC), and microbial biomass carbon (MBC) levels in the top layers (0–10 cm) under the NTSM treatment were 28.5, 26.1 and 51.0% higher than CT. A positive correlation was observed between these labile C fractions and the SOC, and POM-C was the much more sensitive indicator of SOC quality than MBC and DOC. NTSM was unable to sustain the greater yields, and from 2006 to 2011, the mean maize yield for NTSM was significantly lower than that for CT (P < 0.05). NTSM resulted in higher SOC content and stocks in dryland farming systems but lower crop yields is a concern which needs to be addressed in order to make these systems acceptable to the farming community.  相似文献   

5.
The effects of agricultural–pastoral and tillage practices on soil microbial populations and activities have not been systematically investigated. The effect of no-tillage (NT), no-tillage agricultural–pastoral integrated systems (NT-I) and conventional tillage (CT) at soil depths of 0–10, 10–20 and 20–30 cm on the microbial populations (bacteria and fungi), biomass-C, potential nitrification, urease and protease activities, total organic matter and total N contents were investigated. The crops used were soybean (in NT, NT-I and CT systems), corn (in NT and NT-I systems) and Tanner grass (Brachiaria sp.) (in NT-I system); a forest system was used as a control. Urease and protease activities, biomass-C and the content of organic matter and total N were higher (p < 0.05) in the forest soil than the other soils. Potential nitrification was significantly higher in the NT-I system in comparison with the other systems. Bacteria numbers were similar in all systems. Fungi counts were similar in the CT and forest, but both were higher than in NT. All of these variables were dependent on the organic matter content and decreased (p < 0.05) from the upper soil layer to the deeper soil layers. These results indicate that the no-tillage agricultural–pasture-integrated systems may be useful for soil conservation.  相似文献   

6.
Currently, straw transformation in saline soil is largely unknown. The effect of soil salinity on wheat straw transformation and the roles of nitrogen (N) and phosphorus (P) were evaluated in a greenhouse experiment. By sodium chloride (NaCl) addition, straw was applied at the rate of 30 g kg?1 in various saline soils (2.0–4.0 g kg?1). N or combined N and P added in straw amended saline soil (3.0 g kg?1). Three replications of each treatment were sampled to determine straw residues at 30, 60, and 90 d. Results showed straw application significantly increased microbial biomass, especially fungal biomass. Soil salinity increased by 1.0 g kg?1, which decreased straw decomposed rate by 6.3 ~ 11.1%. N application significantly increased straw decomposed rate (p < 0.05), and high salinity obviously inhibited the humidification process of straw. We suggested that straw carbon transformation regulation and little straw residue accumulation in saline soil should arouse more attentions in future studies.  相似文献   

7.
To explore the effects of long-term organic and mineral fertilization practices on the physical properties in Ultisol of south China, a study was conducted since 1998 to investigate the effects of a control (CK), application of chemical fertilizers (NPK), application of organic manure (OM), and NPK fertilizer plus straw returning (NPK + straw). Results showed that OM significantly increased soil water retention capacity at all tensions but with larger increment in low tension at depths of 0–10 cm and 10–20 cm (p < 0.05) when compared with the CK. On the contrary, NPK and NPK + straw led to a decrease in soil water retention capacity under chemical treatments. In the field both in wet and dry periods, soil water content was significantly higher in OM than in NPK + straw and NPK (p < 0.05) since soil hydraulic conductivity (saturated and unsaturated) are lower in OM than in other treatments (p < 0.05). OM was also found to have the lowest soil bulk density and penetration resistance of the four treatments. A high negative correlation was observed between the soil organic carbon and the bulk density and the penetration resistance (p < 0.01). In this way, the application of OM improved the clayey soil physical properties.  相似文献   

8.
To assess changes in organic carbon pools, an incubation experiment was conducted under different temperatures and field moisture capacity (FMC) on a brown loam soil from three tillage practices used for 12 years: no‐till (NT), subsoiling (ST) and conventional tillage (CT). Total microbial respiration was measured for incubated soil with and without the input of straw. Results indicated that soil organic carbon (SOC) and microbial biomass carbon (MBC) under ST, NT and CT was higher in soil with straw input than that without, while the microbial quotient (MQ or MBC: SOC) and metabolic quotient (qCO2) content under CT followed the opposite trend. Lower temperature, lower moisture and with straw input contributed to the increases in SOC concentration, especially under NT and ST systems. The SOC concentrations under ST, with temperatures of 30 and 35°C after incubation at 55% FMC, were greater than those under CT by 28.4% and 30.6%, respectively. The increase in MBC was highest at 35°C for 55%, 65% and 75% FMC; in soil under ST, MBC was greater than that under CT by 199.3%, 50.7% and 23.8%, respectively. At 30°C, the lower qCO2 was obtained in soil incubated under NT and ST. The highest MQ among three tillage practices was measured under ST at 55% FMC, NT at 65% FMC and CT at 75% FMC with straw input. These data indicate the benefits of enhancing the MQ; the low FMC was beneficial to ST treatment. Under higher temperature and drought stress conditions, the adaptive capacity of ST and NT is better than that of CT.  相似文献   

9.
为明确宁南山区马铃薯田不同耕作措施对土壤细菌群落组成及多样性的影响机制，2019年通过大田试验，借助Illumina MiSeq高通量测序手段，系统分析了三种不同耕作方式，即传统翻耕（CT）、深松耕30cm（STD）、深松耕50cm（STS）对0−20cm土层土壤酶活性季节变化规律、土壤全氮、有机碳含量以及土壤细菌群落组成和多样性的影响。结果表明：（1）不同耕作方式下马铃薯土壤酶活性表现出季节变化规律，对马铃薯整个生育期的土壤酶活性测定结果显示，STS较CT能显著增加尿酶活性12.9%，STS较STD和CT分别显著增加蔗糖酶活性17.1%和56.1%，STS较STD和CT处理分别增加过氧化氢酶活性27.5%和16.7%，并且深松耕处理能够显著增加土壤有机碳含量和全氮含量；（2）马铃薯田不同耕作处理下鞘氨醇单胞菌属（Sphingomonas）属于优势属，STD较CT显著增加鞘氨醇单胞菌属相对丰度24.3%。STD较CT增加Simpson指数0.72%，STS处理下Shannon指数最大，较CT处理增加6.4%，STS较CT处理显著增加Chao 1值35.1%；（3）冗余分析显示，细菌多样性（Shannon）和丰富度指数（Chao1值）均与土壤尿酶活性、全氮含量呈显著正相关，逐步回归分析得出全氮是影响宁南山区不同耕作方式下细菌丰富度和多样性的主要因素。因此，在宁南山区采用STS（深松耕50cm）模式可改善土壤酶活性和土壤性状，促进土壤细菌丰富度和多样性的增加，是维持该区马铃薯高产、生态的最佳耕作方式。  相似文献   

10.
The field experiments on calcareous sodic Vertisols were conducted on farmer’s fields in Purna valley of Vidarbha region of Maharashtra. The treatments comprised of different green manures (GMs); crop residues (CRs); gypsum. The chemical and biological properties after 2 years experiment showed that the application of gypsum recorded significant drop in pH and exchangeable sodium percentage (ESP) as compared to organic amendments. But later has outperformed with respect to biological activities viz., dehydrogenase activity (DHA) and microbial respiration and carbon sequestration by enhancing soil organic carbon (SOC), soil organic carbon (SOC) stock, soil microbial biomass carbon (SMBC) and labile carbon pool (POXC). Among the different organic amendments the application of dhaincha improved SMBC by 90%, microbial respiration by 104%, POXC by 59% and DHA by 265% as compare to control. High ESP of these soils showed negative relationship with microbial respiration and POXC (r = 0.48 and r = 0.43, p = < 0.05). While addition of biomass showed positive relationship with SMBC, microbial respiration, POXC and DHA (r = 0.93, r = 0.81, r = 0.83 and r = 0.91 p = < 0.01). The results of study showed green manuring in sodic black soil found to be alternative choice to gypsum, which besides gradual reclamation also enhance biological properties and carbon sequestration.  相似文献   

11.
不同耕作方式对土壤有机碳、微生物量及酶活性的影响   总被引：12，自引：2，他引：10  
【目的】依托8年长期(2005~2012)固定道定位试验,研究不同耕作方式对土壤有机碳、土壤微生物量、土壤酶活性在0—90 cm土层的分布特征,为优化中国西北干旱区的耕作方式提供理论依据。【方法】试验包括固定道垄作(PRB)、固定道平作(PFT)与传统耕作(CT)三种耕作模式下的土壤有机碳土壤总有机碳(TOC)、颗粒有机碳(POC)、土壤微生物量碳(MBC)、土壤微生物量氮(MBN)、土壤微生物量磷(MBP)、蔗糖酶、过氧化氢酶、脲酶及小麦产量进行了测定和分析。【结果】在0—90 cm土层,不同耕作方式下的TOC、POC、MBC、MBN、MBP、蔗糖酶活性、脲酶活性均随着土层的增加呈下降趋势,过氧化氢酶活性呈先下降后增大的分布特征;在0—60 cm,固定道保护性耕作能够显著增加心土层作物生长带土壤有机碳储量,有机碳储量大小为PRBPFTCT;PRB、PFT较CT可以显著增加0—10 cm作物生长带TOC、POC、MBC、MBN、MBP含量、蔗糖酶、脲酶活性,其大小为PRBPFTCT;耕作方式对过氧化氢酶活性影响不显著;TOC、POC、MBC、MBN、MBP、蔗糖酶活性、脲酶活性、过氧化氢酶活性之间均达到了显著或极显著相关。【结论】PRB较PFT、CT能够提高耕作层(0—10 cm)土壤有机碳含量、土壤微生物量、土壤酶活性, 增加作物产量, 增大0—60 cm土层有机碳储量,耕作方式(PRB、PFT及CT)对10 cm以下土层土壤环境改善作用不明显。  相似文献   

12.
耕作方式对华北农田土壤固碳效应的影响   总被引：15，自引：11，他引：15  
研究不同耕作方式对华北农田土壤固碳及碳库管理指数的影响,可为探寻有利于农田固碳的耕作方式提供科学依据。该研究在中国农业大学吴桥实验站进行,试验于2008年设置了免耕秸秆不还田(NT0)、翻耕秸秆不还田(CT0)、免耕秸秆还田(NT)、翻耕秸秆还田(CT)和旋耕秸秆还田(RT)5个处理。研究测定分析了土壤容重、有机碳、易氧化有机碳含量及不同耕作方式下的碳库管理指数。通过对不同耕作方式下0～110cm土壤的分析,结果表明,随着土层的加深,土壤有机碳含量不断下降,NT显著增加了表层(0～10cm)土壤有机碳含量,而>10～50cm有机碳含量较其他处理(NT0除外)有所下降,深层(>50～110cm)处理间差异不明显;土壤容重与有机碳含量呈显著的负相关关系(P<0.01);0～30cm土层有机碳储量以NT最高,CT与其无明显差异,二者较CT0分别高出13.1%和11.0%,而至0～50cm土层,CT的碳储量最高,但与NT无显著差异(P<0.05);与CT0相比,NT0降低了各层土壤易氧化有机碳含量,而NT则在0～10cm土层表现为增加;RT、CT分别显著增加了0～10、>10～30cm土层的碳库管理指数。结果表明,秸秆还田可改善土壤质量,提高农田碳库管理指数,同时碳库管理指数受耕作方式的影响也较大,尤其是CT和RT;NT通过减少土壤扰动、增加有机质的输入,可提高上层土壤有机碳的储量。  相似文献   

13.
ABSTRACT

Studying changes in soil organic carbon (SOC) pools and soil microbial C substrate utilization under plastic mulching in different seasons is of great significance for improving soil fertility and sustainable agricultural development. Based on a 2-year plastic film mulching experiment in northeastern China, we investigated the SOC, labile SOC fractions under three treatments: non-mulching (NM), autumn mulching (AM) and spring mulching (SM). The results showed that SOC decreased with soil depth under the AM and SM treatments compared with the NM treatment. The microbial biomass carbon (MBC) and dissolved organic carbon (DOC) under the AM treatment increased significantly in the 0–10 cm soil layer, by 31.2% and 27.2% (p < 0.05), respectively. The AM treatment significantly increased the utilization of amino acids and carbohydrate C sources. Redundancy analysis (RDA) indicated that MBC was the main factor influencing microbial metabolic functional diversity and accounted for the largest variation in the 0–10 cm layer. Pearson’s correlation analysis illustrated that MBC was strongly correlated with the utilization of the microbial C substrate. We suggest that AM may be an effective and sustainable management practice for improving soil quality and maintaining microbial functional diversity in semi-arid agroecosystems in this area.  相似文献   

14.
Poor soil health and low soil water content during crop growing period are major factor for low productivity of pearl millet – mustard rotation under rainfed semi-arid regions. The authors evaluated five different tillage and residue management practices for improving physico–chemical and biological properties of soil. Results showed that conservation agriculture (CA) practice (zero tillage (ZT) with 4 t ha–1 residue retention) exhibited higher proportion of soil macro-aggregate. It also increased infiltration rate of about 15.2% over conventional tillage without residue but ZT increased soil penetration resistance in surface soil layer. In the residue applied plots, ~2–4% (w/w) higher soil water content was maintained throughout the season than the no-residue plots. CA practice had the highest soil organic carbon (4.96 g kg–1) and microbial biomass carbon (188.3 μg g–1 soil). Significant and positive correlation was also found between soil organic carbon with infiltration rate (r = 0.73**), mean weight diameter (r = 0.80**) and microbial biomass carbon (r = 0.86**). Thus, this study suggests that ZT with residue retention can be advocated in pearl millet – mustard rotations for improving, productivity, soil health and maintaining higher soil water content in rainfed semi-arid regions.  相似文献   

15.

Purpose

Long-term fertilization can influence soil biological properties and relevant soil ecological processes with implications for sustainable agriculture. This study determined the effects of long-term (>25 years) no fertilizer (CK), chemical fertilizers (NPK) and NPK combined with rice straw residues (NPKS) on soil bacterial and fungal community structures and corresponding changes in soil quality.

Materials and methods

Soil samples were collected from a long-term field site in Wangcheng County established in 1981 in subtropical China between mid summer and early autumn of 2009. Terminal restriction fragment length polymorphism (T-RFLP) and the real-time quantitative polymerase chain reaction (real-time qPCR) of bacterial and fungal community and microbial biomass (MB-C, -N and -P) were analyzed.

Results and discussion

Redundancy analysis of the T-RFLP data indicated that fertilization management modified and selected microbial populations. Of the measured soil physiochemical properties, soil organic carbon was the most dominant factors influencing bacterial and fungal communities. The bacterial and fungal diversity and abundance all showed increasing trends over time (>25 years) coupling with the increasing in SOC, total N, available N, total P, and Olsen P in the fertilized soils. Compared to chemical fertilizer, NPKS resulted in the greater richness and biodiversity of the total microbial community, soil organic C, total N, MB-C, -N and -P. The high biodiversity of microbial populations in NPKS was a clear indication of good soil quality, and also indicated higher substrate use efficiency and better soil nutrient supplementation. Otherwise, unfertilized treatment may have a soil P limitation as indicated by the high soil microbial biomass N: P ratio.

Conclusion

Our results suggest that NPKS could be recommended as a method of increasing the sustainability of paddy soil ecosystems.  相似文献   

16.
Conservation tillage has been applied in vast semi‐arid regions of the Guanzhong Plain, Northwest China. The tillage effects on soil aggregation, organic carbon (OC) stabilization and grain yield on this plain have not been fully elucidated. A 9‐year field experiment was established from 2002 on a silty clay loam soil (Eum‐Orthic Anthrosol) growing winter wheat–maize in a double‐cropping system. Six conservation tillage treatments were applied by different combinations of rotary tillage (RT), subsoiling (SS) and no‐till (NT), with or without finely chopped straw retention. Conventional tillage (CT) acted as the control. Results showed that in the surface (0–10 cm) soil, the proportion of water‐stable aggregates (WSA) <0.05 mm was 18% less while that for WSA >2 mm was 98% more under NT treatments compared with CT. Additionally, the oxidizable OC content in WSA 0.25–2 mm was 27% greater under NT treatments compared with CT. The OC stocks increased under SS by 17%, RT by 16% and NT by 15% relative to CT. Grain yield (wheat + maize) showed similar increasing trends in all the tillage treatments compared with CT. Both OC stocks and grain yield were larger in treatments with than without straw retentions. These results indicate that NT is beneficial for OC accumulation in WSA but is limited in its ability to improve soil structure in this region. SS plus straw retention (fine‐chopped or as a mulch) is an effective practice to improve soil structural stability, OC accumulation and soil productivity of Eum‐Orthic Anthrosols in Northwest China.  相似文献   

17.
We investigated the potential of three methods of quantifying microbial biomass carbon (MBC), viz., chloroform fumigation-extraction (CFE) following organic C estimation through Vance method (CFE-V) and Snyder–Trofymow method (CFE-ST), and substrate-induced respiration (SIR) method in soils under various temperate fruit crops along with a control (no plantation) at 0–20 and 21–40 cm soil depths. CFE methods have shown significant (p < 0.05) increase in chloroform labile C in all orchards over the control in surface soil. The interaction between the fruit crops and methods, although significant (p < 0.01), indicated that CFE-ST and SIR methods were statistically at par with each other within the same fruit crop, except peach plantation (CEF-ST significantly lower than SIR) in 0–20 cm soil depth. The coefficient of variation recorded for chloroform labile organic C estimates by CFE-ST method makes it more precise than CFE-V method, especially in 0–20 cm soil depth. The very close agreement between the methods suggests that over this narrower range (i.e., smaller geographical area) all methods are appropriate for assessing MBC. However, SIR, being most sensitive to orchard plantations and strongly correlated with various soil chemical properties, could preferably be recommended for estimation of MBC in such soils. As an alternative to CFE-V method, CFE-ST may also be used for estimation of chloroform labile organic C in these soils.  相似文献   

18.
Sustainable soil management of orchards can have positive effects on both soils and crop yields due to increases in microbial biomass, activity and complexity. The aim of this study was to investigate medium‐term effects (12 yr) of two different management practices termed ‘sustainable’ (ST) and ‘conventional’ (CT) on soil microbial composition and metabolic diversity of a rainfed mature olive orchard in Southern Italy. ST included no‐till, self‐seeding weeds (mainly graminaceous and leguminosae), and mulch derived from olive tree prunings, whilst CT was managed by frequent tillage and included severe pruning with residues removed from the orchard. Microbial analyses were carried out by culture‐dependent methods (microbial cultures and Biolog®). Molecular methods were used to confirm the identification by light microscopy of the isolates of fungi and Streptomyces. Significantly more culturable fungi and bacteria were found in ST than in CT. The number of fungal groups in ST was also significantly greater than in CT. Overall and substrate‐specific Biolog® metabolic diversity indices of microbial communities and soil enzyme activities were greater in ST. The results demonstrate that soil micro‐organisms respond positively to sustainable orchard management characterized by periodic applications of locally derived organic matter. This study confirms the need to encourage farmers with orchards in the Mediterranean basin to practise soil management based on organic matter inputs associated with zero tillage to improve soil functionality.  相似文献   

19.
《Applied soil ecology》2001,16(3):251-261
Reduced tillage of agricultural soils has been shown to result in greater macroaggregation, microbial biomass and microbial diversity. While it has been shown that macroaggregates contain more microbial biomass per unit soil mass than microaggregates, it is unclear how microbial diversity varies with soil aggregation. We investigated the functional diversity (catabolic potential) of bacteria, evaluated by calculating Shannon’s diversity index (H′), substrate richness (S) and substrate evenness (E) from potential substrate utilization patterns, in whole soil (i.e. not separated into different aggregate sizes) and aggregates of different sizes (2–4, 1–2, 0.5–1, 0.25–0.5, and 0.1–0.25 mm diameter) in loam and silt loam soils grown to barley and managed for 6 years under conventional tillage (CT) or zero tillage (ZT) systems in northern British Columbia. There were no significant tillage effects on bacterial diversity in whole soils. In soil aggregates, H′ and E were significantly higher under CT than under ZT on the loam at barley planting time, with no significant aggregate size effects. However, at barley-heading stage, all diversity indices in both soils were significantly higher under ZT than under CT, and they tended to increase with increasing aggregate size. Cluster analysis and principal component analysis of substrate utilization patterns also revealed differences in bacterial community structures between CT and ZT, but the substrates that were utilized differently between the two tillage systems were not the same between soil types or sampling times. The results during the cropping cycle imply that deterioration of soil structure is probably one factor that explains the adverse effects of soil tillage on soil microbial biomass and diversity.  相似文献   

20.
It is increasingly believed that substantial soil organic carbon (SOC) can be sequestered in conservation tillage system by manipulating the functional groups of soil biota. Soil aggregates of different size provide diverse microhabitats for soil biota and consequently influence C sequestration. Our objective was to evaluate the contributions of soil biota induced by tillage systems to C sequestration among different aggregate size fractions. Soil microbial and nematode communities were examined within four aggregate fractions: large macroaggregates (>2 mm), macroaggregates (2–1 mm), small macroaggregates (1–0.25 mm) and microaggregates (<0.25 mm) isolated from three tillage systems: no tillage (NT), ridge tillage (RT) and conventional tillage (CT) in Northeast China. Soil microbial and nematode communities varied across both tillage systems and aggregate fractions. The activity and abundance of microbes and nematodes were generally higher under NT and RT than under CT. Among the four aggregate fractions, soil microbial biomass and diversity were higher in microaggregates, while soil nematode abundance and diversity were higher in large macroaggregates. Structural equation modelling (SEM) revealed that the linkage between microbial and nematode communities and their contributions to soil C accumulation in >1 mm aggregate fractions were different from those in <1 mm aggregate fractions. Higher abundance of arbuscular mycorrhizal fungi (AMF) could enhance C retention within >1 mm aggregates, while more gram-positive bacteria and plant-parasitic nematodes might increase C accumulation within <1 mm aggregates. Our findings suggested that the increase in microbial biomass and nematode abundance and the alteration in their community composition at the micro-niche within aggregates could contribute to the higher C sequestration in conservation tillage systems (NT and RT).  相似文献   

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