玉米根鞘改变土壤粒径及养分有效性

Root exudates,microorganism colonization and soil aggregates together form the rhizosheath,a special cylinder of micro-ecosystem adhering to the root surface.To study how the rhizosheath affects soil structure and nutrient distribution,we analyzed the impact of maize rhizosheath on soil particle size and nutrient availability in pot and field experiments.The results showed that there was a significant size decrease of soil particles in the rhizosheath.Meanwhile,the soil mineral nitrogen in the rhizosheath was significantly higher than that in the rhizosphere or bulk soil at tasseling and maturity stages of maize.The contents of Fe and Mn were also differentially altered in the rhizosheath.Rhizosheath development,indicated by a dry weight ratio of rhizosheath soil to the root,was relatively independent of root development during the whole experimental period.The formation of maize rhizosheath contributed to the modulation of soil particle size and nutrient availability.The subtle local changes of soil physical and chemical properties may have profound influence on soil formation,rhizospheric ecosystem initiation,and mineral nutrient mobilization over the long history of plant evolution and domestication.     

东北黑土区冻融作用对黑土水稳性团聚体的影响

Soil aggregate stability,an important index of the physical characteristics of a soil,can provide a good indication of a soil’s erodibility,and deserves special consideration in regions with cold climate.The objective of this study was to study the effect of freeze-thaw on soil water-stable aggregates in the black soil region of Northeast China.Samples of a typical black soil in the region were collected to measure water-stable aggregates after freeze-thaw under different conditions(i.e.,initial moisture contents,freezethaw cycles and freezing temperatures)by wet-sieving into eight particle size groups(10,10–6,6–5,5–3,3–2,2–1,1–0.5,and0.5–0.25 mm).Freeze-thaw had the most effect on aggregate stability when the samples had an initial moisture content of 400 g kg-1.The water-stable aggregates of the four larger particle size groups(5,5–3,3–2,and 2–1 mm)reached a peak stability value,but those of the two smaller particle size groups(1–0.5 and 0.5–0.25 mm)reached a minimum value when the soil moisture content was 400 g kg-1.Water-stable aggregates of the four larger particle size groups decreased while those of the two smaller particle size groups increased with the increase of freeze-thaw cycles.As temperatures fell,the water-stable aggregates of the four larger particle size groups decreased while those of the two smaller particle size groups increased.     

土壤圈及其对全球变化的影响

With development of modern geoscience,particularly development of environmental sciences,the contemporary soil science is undergoing great changes in both research contents and scope.Soil is not only a certain substance or a certain independent natural historical body but also a spheric layer with peculiar structure and functions in the earth system.From the viewpoint of the geo-biosphere system of earth,soil science does deal not only with the soil substances per se but also more importantly with the relationships among soil,the other spheres and the human survival environment in view of the “pedosphere“,This is the new orientation of soil science today and will affect profoundly the studies on the human survival environment and global changes,To throw more light on this subject,the present paper intends to address the conception of pedosphere and its role in global changes,Also addressed are series of environmental issues in China and their relations to the global changes.Moreover,research orientation and priorities are indicated ,including exploitation and protection of the soil resources,soil fertility and sustainable agricultural development,construction of the ecological environment,and the material cycling in pedosphere and its relation to global changes.     

土壤微生物多样性研究方法综述

Soil microorganisms play a central role in decomposing organic matter, in determining the release of mineral nutrients, and in nutrient cycling. Recently, extensive studies have focused on soil microbial diversity. However, understanding the diversity of this complex microbial community in the soil environment is a challenging task. Thus, it is important to master and comprehend appropriate methods for studying soil microbial diversity. Concepts of soil microbial diversity and major methods of study are briefly introduced in this paper. Then, the application of biochemical-based and molecular-based techniques in this area, and their advantages and disadvantages are evaluated. Based on recent related research, perspectives for studying microbial diversity in soils are presented.     

挪威北部土壤微生物活性的季节变化

Seasonal development of soil microbial activity and bacterial biomass in sub-polar regions was investigated to determine the impacts of biotic and abiotic factors, such as organic matter content, temperature and moisture. The study was performed during spring thaw from three cultivated meadows and two non-cultivated forest sites near Alta, in northern Norway. Samples from all five sites showed increasing respiration rates directly after the spring thaw with soil respiration activity best related to soil organic matter content. However, distributions of bacteria] biomass showed fewer similarities to these two parameters. This could be explained by variations of litter exploitation through the biomass. Microbial activity started immediately after the thaw while root growth had a longer time lag. An influence of root development on soil microbes was proposed for sites where microorganisms and roots had a tight relationship caused by a more intensive root structure. Also a reduction of microbial activity due to soil compaction in the samples from a wheel track could not be observed under laboratory conditions. New methodological approaches of differential staining for live and dead organisms were applied in order to follow changes within the microbial community. Under laboratory conditions freeze and thaw cycles showed a damaging influence on parts of the soil bacteria. Additionally, different patterns for active vs. non-active bacteria were noticeable after freeze-thaw cycles.     

基于微观球体颗粒模型的土水特征曲线研究

When variations occur in the water content or dry bulk density of soil,the contact angle hysteresis will affect the soil-water characteristic curve(SWCC).The occurrence of the contact angle hysteresis can be divided into slipping and pinning.It is difficult to determine the effect of pinning existence on SWCC by tests.In this study,the effect of contact angle hysteresis on SWCC was analyzed either in the case of no variations in soil dry bulk density with changes in soil water content or no variations in soil water content with changes in soil dry bulk density.In both cases,soil particles were simplified to the spherical particle model.Based on the geometrically mechanic relationship between the particles and connecting liquid bridges,a physical model for predicting the SWCC was derived from the spherical particle model.Adjusting parameters made the model applicable to various soils,that is,the cohesive soil was considered as micron-sized spherical particles.Through the simulations on SWCC test data of sand,silt,clay,and swelling soil,it was confirmed that the physical model possessed good reliability and practicability.Finally,the analysis of rationality of contact angle was performed based on the basic assumptions of the model.     

土壤微生物对不同粒径、不同表面和孔隙性质生物炭的响应

Biochars are known for their heterogeneity, especially in pore and surface structure associated with pyrolysis processes and sources of feedstocks. The surface area of biochar is likely to be an important determinant of the extent of soil microbial attachment, whereas the porous structure of biochar is expected to provide protection for soil microorganisms. Potential interactions between biochars from different sources and with different particle sizes were investigated in relation to soil microbial properties in a short-term incubation study. Three particle size(sieved) fractions(0.5–1.0, 1.0–2.0 and 2.0–4.0 mm) from three woody biochars produced from jarrah wood,jarrah and wandoo wood and Australian wattle branches, respectively, were incubated in soil at 25?C for 56 d. Observation by scanning electron microscopy(SEM) and characterisation of pore and surface area showed that all three woody biochars provided potential habitats for soil microorganisms due to their high porosity and surface areas. The biochars were structurally heterogeneous,varying in porosity and surface structure both within and between the biochar sources. After the 56-d incubation, hyphal colonisation was observed on biochar surfaces and in larger biochar pores. Soil clumping occurred on biochar particles, cementing and covering exposed biochar pores. This may have altered surface area and pore availability for microbial colonisation. Transient changes in soil microbial biomass, without a consistent trend, were observed among biochars during the 56-d incubation.     

土壤排水系统在土壤演变中的作用

While research on pedogenesis mainly focuses on long-term soil formation and most often neglects recent soil evolution in response to human practices or climate changes, this article reviews the impact of artificial subsurface drainage on soil evolution. Artificial drainage is considered as an example of the impact of recent changes in water fluxes on soil evolution over time scales of decades to a century. Results from various classical studies on artificial drainage including hydrological and environmental studies are reviewed and collated with rare studies dealing explicitly with soil morphology changes, in response to artificial drainage. We deduce that soil should react to the perturbations associated with subsurface drainage over time scales that do not exceeding a few decades. Subsurface drainage decreases the intensity of erosion and must i) increase the intensity of the lixiviation and eluviation processes, ii) affect iron and manganese dynamics, and iii) induce heterogeneities in soil evolution at the ten meter scale. Such recent soil evolutions can no longer be neglected as they are mostly irreversible and will probably have unknown, but expectable, feedbacks on crucial soil functions such as the sequestration of soil organic matter or the water available capacity.     

长期地下水位管理及施用秸秆对中国亚热带水稻土团聚体形成的影响

Soil organic carbon(SOC) and iron(Fe)-oxides are important contributors of aggregate stability in highly weathered soils, and they are influenced by groundwater management and straw application. A 30-year plot experiment with early rice(Oryza sativa L.)-late rice-winter fallow rotations was conducted using a upland clay soil in cement pools under shallow groundwater table at a depth of 20 cm(SGT) and deep groundwater table at a depth of 80 cm(DGT) to simulate the groundwater tables of two types of important paddy soils, gleyed paddy soils and hydromorphic paddy soils, respectively, in subtropical China. Soil redox potential(Eh) was measured in situ, and 0–20 cm soil samples were collected for the analyses of soil Fe-oxides, SOC, and aggregates under SGT or DGT with different straw application treatments, in order to evaluate the interaction of groundwater management and straw application on paddy soil aggregation and the relative importance of SOC or Fe-oxides on soil aggregation. The results showed that soil Eh was restricted by irrigation, and its variation was more significant under DGT than under SGT. The decreased soil Eh or reduced drying and wetting cycles under SGT resulted in more SOC accumulation with the straw application, had no effect on soil free Fe-oxides(Fed), significantly increased the amorphous Fe-oxide(Feo) and complex Fe-oxide contents, but decreased the crystalline Fe-oxide content(Fed–Feo). The soils under DGT had more macroaggregates than those under SGT, but the difference decreased with the straw application. It could be concluded that soil Fe-oxides were the principal contributing factor to the aggregation of paddy soils in subtropical China and SOC was also an important contributing factor.     

Responses of Soil Enzyme Activities and Microbial Community Composition to Moisture Regimes in Paddy Soils Under Long-Term Fertilization Practices

The effects of fertilization on activity and composition of soil microbial community depend on nutrient and water availability;however,the combination of these factors on the response of microorganisms was seldom studied.This study investigated the responses of soil microbial community and enzyme activities to changes in moisture along a gradient of soil fertility formed within a long-term(24 years)field experiment.Soils(0–20 cm)were sampled from the plots under four fertilizer treatments:i)unfertilized control(CK),ii)organic manure(M),iii)nitrogen,phosphorus,and potassium fertilizers(NPK),and iv)NPK plus M(NPK+M).The soils were incubated at three moisture levels:constant submergence,five submerging-draining cycles(S-D cycles),and constant moisture content at 40%water-holding capacity(low moisture).Compared with CK,fertilization increased soil organic carbon(SOC) by 30.1%–36.3%,total N by 27.3%–38.4%,available N by 35.9%–56.4%,available P by 61.4%–440.9%,and total P by 28.6%–102.9%.Soil fertility buffered the negative effects of moisture on enzyme activities and microbial community composition.Enzyme activities decreased in response to submergence and S-D cycles versus low moisture.Compared with low moisture,S-D cycles increased total phospholipid fatty acids(PLFAs)and actinomycete,fungal,and bacterial PLFAs.The increased level of PLFAs in the unfertilized soil after five S-D cycles was greater than that in the fertilized soil.Variations in soil microbial properties responding to moisture separated CK from the long-term fertilization treatments.The coefficients of variation of microbial properties were negatively correlated with SOC,total P,and available N.Soils with higher fertility maintained the original microbial properties more stable in response to changes in moisture compared to low-fertility soil.     

人为土中纳米颗粒的发生、结构和矿物相

Soils contain various kinds of crystalline to amorphous solid particles with at least one dimension in the nanoscale (<100nm). These nanoparticles contribute greatly to dynamic soil processes such as soil genesis, trace element cycling, contaminant transport, and chemical reaction. The nano-sized fraction of an Anthrosol was obtained to determine the occurrence, chemical composition, structure, and mineral phases of nanoparticles using high-resolution transmission electron microscopy (HRTEM) equipped with an energy-dispersive X-ray spectroscopy. Selected area electron diffraction or the fast Fourier transform of high-resolution images was used in structural characterization of the nanoparticles with HRTEM. Two nanoscale mineral types, i.e., mineral nanoparticles and nanominerals, were observed in the Anthrosol. Mineral nanoparticles in soil included well crystalline aluminumsilicate nanosheets, nanorods, and nanoparticles. Nanosheets with a length of 120-150 nm and a width of about 10-20 nm were identified as chlorite/vermiculite series. The presence of clear lattice fringe spacing in HRTEM image of nanoparticles indicated that mineral nanoparticles had a relatively good crystallinity. The nanomineral ferrihydrite also existed in the Anthrosol. The HRTEM images and the particle size distribution histogram suggested that these ferrihydrite nanoparticles were quite homogeneous, and had a narrow size distribution range (1-7 nm) with a mean diameter of 3.6±1.6 nm. Our HRTEM observation indicated that mineral nanoparticles and nanominerals were common and widely distributed in Anthrosols. HRTEM and selected area diffraction or lattice fringe spacing characterization provided further proofs to the structure of nanoparticles formed in soil.energy-dispersive X-ray spectroscopy (EDS), ferrihydrite, high-resolution transmission electron microscopy (HRTEM), nanominerals, nano-sized fraction     

模拟降雨条件下土壤结皮的发展和聚丙烯酰胺对黄土上结皮形成的影响

This study evaluated the morphological characteristics and dynamic variation in characteristics of soil crust and iden-tified the relationships between soil crust and splash erosion under simulated rainfall.The effect of polyacrylamide (PAM) on soil aggregate stabilization and crust formation was also investigated.A laboratory rainfall simulation experiment was carried out using soil sample slices.The slices were examined under a polarized light microscopy and a scanning electron microscope (SEM).The results revealed that the soil crusts were thin and were characterized by a greater density,higher shear strength,finer porosity,and lower saturated hydraulic conductivity than the underlying soil.Two types of crusts,i.e.,structural and depositional crusts,were observed.Soil texture was determined to be the most important soil variable influ-encing surface crust formation;depositional crust formation was primarily related to the skeleton characteristics of the soil and happened when the soil contained a high level of medium and large aggregates.The crust formation processes observed were as follows:1) The fine particles on the soil surface became spattered,leached,and then rough in response to raindrop impact and 2) the fine particles were washed into the subsoil pores while a compact dense layer concurrently formed at soil surface due to the continual compaction by the raindrops.Therefore,the factors that influenced structural crust formation were a large amount of fine particles in the soil surface,continual impact of raindrops,dispersion of aggregates into fine particles,and the formation of a compact dense layer concurrently at the soil surface.It was concluded that the most important factor in the formation of soil crusts was raindrop impact.When polyacrylamide (PAM) was applied,it restored the soil structure and greatly increased soil aggregate stabilization.This effectively prevented crust formation.However,this function of PAM was not continuously effective and the crust reformed with long-term rainfall.In conclusion,this study showed that soil micromorphological studies were a useful method for evaluating soil crust formation.     

用激光衍射法评价有机物和和碳酸盐对土壤团聚的作用

>Aggregation in many soils in semi-arid land is affected by their high carbonate contents.The presence of lithogenic and/or primary carbonates can also inffuence the role of soil organic matter(SOM) in aggregation.The role of carbonates and SOM in aggregation was evaluated by comparing the grain-size distribution in two carbonate-rich soils(15% and 30% carbonates) under conventional tillage after different disaggregating treatments.We also compared the effect of no-tillage and conventional tillage on the role of these two aggregating agents in the soil with 30% of carbonates.Soil samples were treated as four different ways:shaking with water(control),adding hydrochloric acid(HCl) to remove carbonates,adding hydrogen peroxide(H2O2) to remove organic matter,and consecutive removal of carbonates and organic matter(HCl + H2O2),and then analyzed by laser diffraction grain-sizing.The results showed that different contributions of carbonates and SOM to aggregate formation and stability depended not only on their natural proportion,but also on the soil type,as expressed by the major role of carbonates in aggregation in the 15% carbonate-rich soil,with a greater SOC-to-SIC(soil organic C to soil inorganic C) ratio than the 30% carbonate-rich soil.The increased organic matter stocks under no-tillage could moderate the role of carbonates in aggregation in a given soil,which meant that no-tillage could affect the organic and the inorganic C cycles in the soil.In conclusion,the relative role of carbonates and SOM in aggregation could alter the aggregates hierarchy in carbonate-rich soils.     

Nitrogen fertilization degrades soil aggregation by increasing ammonium ions and decreasing biological binding agents on a Vertisol after 12 years

Degraded soil aggregation arising from nitrogen(N) fertilization has been reported in many studies; however, the mechanisms have not yet been clarified.Elucidating the impact of N fertilization on soil aggregation would help to improve soil structure and sustain high crop production. The objective of this study was to determine the impact of long-term N fertilization on soil aggregation and its association with binding and dispersing agents. A 12-year(2008–2019) N fertilization field experiment ...     

中国西南薄层砾石土喀斯特坡地土壤的137Cs分布特点

The fallout radionuclide cesium-137(137 Cs) has been widely employed as a tracer for assessment of soil loss from thick uniform soils;however,few studies have been conducted on thin stony soils on slopes underlain by carbonate rocks which are widely distributed in karst areas.Information derived from 137 Cs measurement of soil samples collected along a carbonate rock slope with thin stony soil where neither soil erosion nor deposition occurred was used to investigate the characteristics of 137 Cs redistribution in a karst area of Southwest China.The results indicated that the 137 Cs inventories of the surface soil on the slope studied were much lower than that of the local 137 Cs reference inventory and the 137 Cs activities were much higher than those on slopes with thick uniform soils.The spatial distribution of 137 Cs inventories was characterized by considerable variation.The high 137 Cs depletion in the stony soil of the slope studied was mainly because a considerable proportion of the fallout input of 137 Cs could be lost with runoff and the dissolution of carbonate particles in the soil promoted the loss of 137 Cs.These demonstrated that the rates of soil loss could not be estimated from the degree of depletion of the 137 Cs inventory relative to the local reference inventory for the thin stony soil of the rocky slope underlain by carbonate rocks in the study area in the way that has been widely used in areas with thick uniform soils.     

湿地土壤NH4+吸附解吸对冻融循环的响应

Nitrogen (N) cycling in boreal peatland ecosystems may be influenced in important ways by freeze-thaw cycles (FTCs).Adsorption and desorption of ammonium ions (NH + 4) were examined in a controlled laboratory experiment for soils sampled from palustrine wetland,riverine wetland,and farmland reclaimed from natural wetland in response to the number of FTCs.The results indicate that freeze-thaw significantly increased the adsorption capacity of NH + 4 and reduced the desorption potential of NH + 4 in the wetland soils.There were significant differences in the NH + 4 adsorption amount between the soils with and without freeze-thaw treatment.The adsorption amount of NH + 4 increased with increasing FTCs.The palustrine wetland soil had a greater adsorption capacity and a weaker desorption potential of NH + 4 than the riverine wetland soil because of the significantly higher clay content and cation exchange capacity (CEC) of the riverine wetland soil.Because of the altered soil physical and chemical properties and hydroperiods,the adsorption capacity of NH + 4 was smaller in the farmland soil than in the wetland soils,while the desorption potential of the farmland soil was higher than that of the wetland soils.Thus,wetland reclamation would decrease adsorption capacity and increase desorption potential of NH + 4,which could result in N loss from the farmland soil.FTCs might mitigate N loss from soils and reduce the risk of water pollution in downstream ecosystems.     

7Be: 中国贵州Hongfeng湖流域表土季节性侵蚀的地球化学示踪剂

7Be penetrative depth in undisturbed surface soil is within 4mm.^7Be activity shows exponential decrease with soil depth,which is expressed as a diffusion process.7Be penetrative depth in undisturbed surface soil is apparently deeper in the fall (0.22-0.37g cm^-1) than in the spring (0.11-0.28g cm^-2) at the same site;Whereas,^7Be apparent activity at the top of surface soil is higher in the spring (0.3-2.2Bq g^-1)than in the fall (0.2-0.5Bqg^-1) at the same site,The 7Be inventory(189-544Bq m^-2)changes with both locations and seasons.Although the ^7Be flux to the earth‘s surface increases with amount of precipitation,its maximum inventory in the soil profiles decreases to 30%-40% after the rainy period.Calculated by the diffusion equation,the erosion and accumulation rates of soil particles are agreeable with the observation in situ,Which shows that the rates in fall are 1.5 times those in spring.The eroded soil particles almost all have been removed on the tablelands rathel than transported into the drainage system.This indicates that the soil erosion process in the karst region is only partial transportation within a short distance.     

Soil and microbial C:N:P stoichiometries play vital roles in regulating P transformation in agricultural ecosystems: A review

Stoichiometry plays a crucial role in biogeochemical cycles and can modulate soil nutrient availability and functions. In agricultural ecosystems,phosphorus(P) fertilizers(organic or chemical) are often applied to achieve high crop yields. However, P is readily fixed by soil particles, leading to low P use efficiency. Therefore, understanding the role of carbon:nitrogen:P stoichiometries of soil and microorganisms in soil P transformation is of great significance for P management in agriculture....     

Long-time precipitation reduction and nitrogen deposition increase alter soil nitrogen dynamic by influencing soil bacterial communities and functional groups

The effects of precipitation reduction and nitrogen deposition increase on soil bacterial communities and functions impact soil nitrogen cycling. Seasonal changes could modify the effects of precipitation reduction and nitrogen deposition increase on bacterial communities and functions by changing soil environments and properties. Understanding soil microbial communities and the seasonal response of functions to precipitation reduction and nitrogen deposition increase may be important for the accurate prediction of changes in the soil nitrogen dynamics. Thus, a long-term field simulation experiment of nitrogen deposition increase and throughfall exclusion was established to investigate soil bacterial communities’ response to nitrogen deposition increase and/or precipitation reduction, with no nitrogen deposition increase and no precipation reduction as a control, in a temperate forest. We examined soil bacterial communities (Illumina sequencing) under different treatments during the winter, freezing-thawing cycle periods (FTCs), and growing season. The bacterial functional groups were predicted by the FAPROTAX database. The results showed that nitrogen deposition increase, precipitation reduction, the combined effect of nitrogen deposition increase and precipitation reduction, and seasonal changes significantly altered the soil bacterial community composition. Interestingly, by combining the result of a previous study in which nitrogen deposition increase increased the nitrous oxide flux in the same experimental system, the loss of soil nitrogen was increased by the decrease in denitrification and increase of nitrification bacteria under nitrogen deposition increase, while ammonification bacteria significantly increased and N-fixing bacteria significantly decreased with precipitation reduction compared to the control. In relation to seasonal changes, the aromatic-degrading, cellulolytic, and ureolytic bacteria were lowest during FTCs, which indicated that FTCs might inhibit biodegradation. Nitrification and nitrite-oxidizing bacteria increased with nitrogen deposition increase or precipitation reduction and in FTCs compared to the control or other seasons. The interaction between treatment and season significantly changed the soil bacterial communities and functions. These results highlight that nitrogen deposition increase, precipitation reduction, seasonal changes, and their interactions might directly alter bacterial communities and indirectly alter the dynamics of soil N.     

中国亚热带土壤的1.4nm过渡矿物: 综述

This paper is a review of some advances in the studies on 1.4-nm intergrade mineral of soils in subtropical China. 1)1.4-nm intergrade mineral occurs ubiquitously in soils of subtropical China. The 1.4-nm mineral in red soil and yellow soil is mainly 1.4-nm intergrade mineral, and in acidic yellow-brown soil (pH < 5.5) is vermiculite alone or 1.4-nm intergrade mineral together with vermiculite. The distribution and the content of 1.4-nm intergrade mineral in the mountain soils are more widespread and higher than those of the corresponding soils in horizontal zone. 2) The interlayer material of 1.4-nm intergrade mineral in these soils appears to be hydroxy-A1 polymers instead of hydroxy-Fe, proto-imogolite or kaolin-like material. There is a significant positive correlation between A1 amount extracted from the soil with sodium citrate after DCB extraction and pH value of the citrate solution after the extraction. The citrate can also extract a certain amount of silicon from the soil, but the silicon may not come from interlayer of 1.4-nm intergrade mineral. 3) It was seldom studied that either vermiculite or smectite did the natural 1.4-nm intergrade mineral come from in soil, or it was commonly thought to come from vermiculite. A recent report has revealed that it can come from smectite. There are some different behaviors between the 1.4-nm intergrade mineral derived from vermiculite and that from smectite. For example, they exert different influences on the formation of gibbsite. The 1.4-nm intergrade mineral derived from smectite may promote the formation of gibbsite in the yellow soil. 4) The type of 1.4-nm minerals in soils. i.e., vermiculite or 1.4-nm intergrade mineral, may be significant to soil properties, such as soil acidity, exchangeable Al, electric charge amount and specific surface area. Therefore, the management for the soil in which 1.4-nm mineral is mainly 1.4-nm intergrade mineral or vermiculite should be dealt with differently.