Abstract:Earthworm plays a key role in the terrestrial ecosystem and is often used as test organism in chemical risk assessment. To understand how earthworm accumulates hydrophobic organic chemicals (HOCs) and models for its prediction are very important to security of the food chain and chemicals management. A brief introduction is presented to processes of earthworm accumulation of HOCs and its affecting factors, and several models, as well, for prediction of the accumulation, such as empirical model, rate model, equilibrium-partition model, mechanical model and fugacity model. In general, earthworm accumulation of HOCs has two pathways: ingestion and percutaneous absorption through simple diffusion. As for most of the HOCs the latter is the dominant one. However, the contribution of ingestion increases with the increasing hydrophobicity of the chemicals (logK_ow>5), especially in soils high in organic matter content. All the prediction models, except the rate model are developed on the basis of the three hypotheses: (1) HOCs are mainly persistent organic pollutants and their basic behavior in the soil-earthworm ecosystem is the process of distribution and equilibrium between the solid-liquid phase of the soil and the biophase of earthworm; (2) the fat phase of earthworm is the main accumulation pool of such organic pollutants; and (3) HOCs inside earthworm are not subject to any or negligible biotransformation or metabolism. At the end, the paper suggests that the research in the future should focus on behaviors of HOCs inside earthworm, such as distribution, so as to understand more about eco-toxicology of HOCs in earthworm.

Abstract:Changes in soil physical properties in the surface layer (0~20 cm) on a sloping farmland of Mollisols under no-tillage (NT), reduced tillage (RT) and conventional tillage (CT), separately, were monitored throughout the entire crop growing season for comparison to explore differences between soils under tillage patterns in seasonal variation of soil structure and hydraulic conductivity and relationships of the variations with soil-water loss. Results show that soil bulk density in NT varied slightly, remaining in the range of 1.20~1.30 g cm^-3. NT was higher than CT in content of water stable soil aggregate > 0.25 mm size (WR_0.25) and mean weight diameter (MWD), higher than RT and CT in initial and stable soil infiltration rate, 4.68% and 4.44% higher than RT and NT in mean soil water content, and 86% and 100% lower than CT in runoff and soil loss, respectively. RT ranged between NT and CT in all the measured properties, throughout the season except in summer. In RT, deep tillage of the furrows in summer significantly lowered soil bulk density in the furrow, at least 0.15 g cm^-3 lower than that in NT and CT, thus increasing the initial soil infiltration rate by 30% or more. RT was 20% and 40% lower than CT in soil and water loss, respectively. In CT, soil bulk density in ridge increased from 0.91 g cm^-3 at the seeding stage to 1.23 g cm^-3 at the harvesting stage, and that in furrow remained around 1.30 g cm^-3 . CT was lower than the other two in WR_0.25, MWD, soil infiltration rate and soil water content. It lost 10% of the rainfall it had during the entire the crop growing season and soil at 615 t km^-2 a^-1. NT was rather stable in soil structure and the best in soil-water conservation among the three. Hence, it is a tillage practice significant in soil-water conserving effect. RT is also a practice that has some soil-water conserving effect. And both of the practices help improve soil physical properties.

Abstract:The data of 138 rice "3414" fertilizer tests conducted in Shangrao City of Jiangxi Province were studied and analyzed for spatial distribution of fertilizer use efficiency of the current rice crop and impacts of its affecting factors, such as soil type, fertilization rate , landform type and soil fertility, using ARCGIS and SPSS analysis software. Results show that in Shangrao City the nitrogen, phosphorus and potassium fertilizer utilization rate of the current rice crop averaged 36.86%, 18.86% and 43.89%, respectively, which varied to some extent from region to region, showing a decreasing order of Southwest > Southeast > Northwest > North > Central. The fertilizer nutrient utilization rate of the current rice crop varied in a certain pattern as affected by soil type (or soil species). It was the highest in the poorly developed Typic Hapli-Stagnic Anthrosols, and the lowest in the highly developed Typic Gleyi-Stagnic Anthrosols; the fertilizer use efficiency of the current rice crop was negatively related to fertilization rate, The higher the fertilization rate, the lower the fertilizer use efficiency; the effect of landform followed the order of plain > hilly land > mountain land; and the effect of soil fertility was also very important, displaying a decreasing order of low fertility > middle fertility > high fertility.

Abstract:Based on the vector patch units of the 1:50 000, 1:1 000 000 and 1:14 000 000 soil maps of the Tai Lake region and the grid units, different in resolution, derived from the above mentioned vector patch units, and the 1982 paddy soil organic carbon pool of the region as well, soil organic carbon pool in the surface layer (0~20 cm) of paddy fields in the region of the year of 2000 was simulated using the DNDC model. And comparison analysis was done of variations of number of soil types, area of each soil type, soil organic carbon storage in the surface layer and soil organic carbon density relative to grid units different in solution and vector patch units different in scale. The 4 indices derived from the vector patch units were set as benchmarks and the relative variability (VIV, %) used to discriminate optimal resolutions of grid units simulated based on the DNDC models of different scales. Results show that the optimal resolution of the simulated grid units converted from the vector patch units of the 3 different scales is 0.2 km × 0.2 km, 2 km × 2 km and 17 km × 17 km, separately, on the premises that all the four indices are less than 1% in VIV. The optimal resolution of grid units can not only meet the requirement for precision in simulation, but also avoid data redundancy and waste of resources. Relationships established between the scales of the soil organic carbon simulation researches and the optimal resolutions of grid units are of great reference value to the researches on modeling of soil organic carbon pool on a regional scale.

Abstract:County is the basic unit for estimating soil organic carbon stock in China at the country scale. Rational soil sampling density is fundamental to assurance of a desired accuracy of the estimation. A case study of Taoyuan County was performed and designed to have 8 levels of sampling density, i.e. 4.70, 0.90, 0.60, 0.40, 0.25, 0.15, 0.10, and 0.05 samples per km^-2, to explore effect of sampling density on accuracy of the estimation of soil organic carbon stock at a county scale. Data of the sampling were analyzed with the classical statistical and geo-statistical methods. Classical statistical analysis shows that lower sampling density increased fluctuation of the mean of soil organic carbon and its variation coefficient, and the standard errors (Y) as a power function of sampling density (X) (Y=0.025X^-0.47, R²=0.97, p<0.01). Geo-statistical analysis discovers that lower sampling density increased nugget value and nugget-to-sill ratio, and fluctuation of partial sill, range, and R² as well, and residual error (Y), too, as a power function of sampling density (X) (Y=0.0014X^-1.66, R²=0.56, p<0.05). Meanwhile, the variation of spatial distribution of soil organic carbon in a small locality gradually weakened, and fluctuation of the estimation of soil organic carbon stock and the associated mean error gradually intensified, while the root mean square error (Y) increased as a power function of sampling density (X) (Y=0.77X^-0.05, R²=0.59, p<0.05). As a whole, when the sampling density dropped below 0.15 samples per km², all the above-mentioned indices intensified and as a result, accuracy of the estimation of soil organic carbon stock declined drastically. In overall consideration of the balance between economic inputs and the accuracy demand, the authors propose that the optimal sampling density for estimation of soil organic carbon stock at a county scale is 0.15 samples per km².

Abstract:Through in-lab simulation, research was carried out on retention and migration of soil particles in different sandy porous media relative to concentration of soil suspension, to explore characteristics of the migration of soil particles in sandy porous media. Results show that migration of soil particle in sandy porous media was influenced by size and concentration of soil particles as well as composition of the porous media. Retention dominated the transport of soil particles through porous media with retention rate increasing with the concentration of soil particles, and decreasing with the proportion of coarse sand in porous media. The outflow of total particles, > 50 μm particles and 1～50 μm particles increased with the input amount of their respective fractions in a power function, while the outflow of < 1 μm particles increased linearly with the input amount. The outflow of total particles increased linearly with the proportion of coarse sand in porous media. The results from this study suggest that composition of porous medium and size and concentration of soil particles are major factors affecting migration of soil particles through sandy porous media, and factors that should be taken into full account in the study on fate of soil particles and contaminants in porous media.

Abstract:The study on thermal properties of mulched soil is of some great significance to the study of water and heat transfer in the vadose zone and application of the mulching technology. A 11-needle heat-pulse probe was used to measure soil thermal diffusivity, thermal capacity and thermal conductivity at different depths, 6 mm, 18 mm and 30 mm in sandy yellow earth under different mulches, no mulch, straw and gravel, so as to explore dynamic variation of the soil thermal properties and inner relationship between the soil thermal parameters and soil moisture in mulched soils. Results show that (1) mulching increased the soil thermal parameters and the more significant the effects, the closer to the soil surface; (2) rainfall also increased the soil thermal parameters, which decreased between two rainfall events and the difference increased between the bare soil and the mulched soils in the thermal parameters; (3) after a rainfall event, the three thermal parameters differed in dynamic variation process, with thermal capacity being the most sensitive in response to rainfall, and followed by thermal conductivity, and with thermal diffusivity starting to decline later than the other two, over 48 hours later at all the three soil layers, and in the mulched soils than in the bare soil. In soils constant in soil bulk density, soil water content was the most important factor affecting the soil thermal parameters in the process of frequent alternation of wetting and drying. Analysis of the relationships between the soil thermal parameters and soil water content in mulched soils showed that the relationship in soils mulched with either gravels or straw was similar to that in the bare soil, and that thermal conductivity increased as an exponential function of soil water content, soil thermal capacity did linearly with soil water content and soil thermal diffusivity increased first and then decreased with increasing water content. The peak of soil heat diffusion rate occurred in the sandy yellow earth, 0.20 cm³ cm^-3 in water content. Besides, from these above findings, it can be concluded that surface mulch had a significant impact on dynamic variation of the thermal properties and the water conservation effect of mulch would directly affect variation of the soil thermal properties.

Abstract:In order to characterize 3-D microstructures of the soil aggregates in the paddy soil of a long-term fertilization experiment on red soil in Jinxian, Jiangxi Province, as affected by different patterns of fertilization (CK, NPK and NPKOM), soil aggregates, 3~5 mm in diameter, collected from the paddy soil, were scanned with a micro-CT scanner at the Shanghai Synchrotron Radiation Facility (SSRF) for slice images, 3.7 μm in resolution, which were then processed with the 3DMA_Rock software into digital images for construction of a pore-throat network model. Results show that compared with CK, Treatment NPK decreased soil porosity, specific surface area, throat numbers, and average path length by 31.6%, 28.8%, 15.1% and 12.6%, respectively, while Treatment NPKOM increased them by 77.6%, 68.4%, 182.8% and 14.4%, respectively, demonstrating that long-term application of chemical fertilizer caused degradation of soil aggregate structure, whereas combined application of chemical fertilizer with organic manure significantly improved aggregate microstructure and promoted formation and stability of soil aggregates and the soil quality, thus keeping the soil in good aeration and permeability and building up soil fertility.

Abstract:To quantify the relation of salt accumulation in the topsoil of deserted land with groundwater in areas with shallow groundwater table in Kashi, Xinjiang, in-situ monitoring was performed of soil water content, salt content in the topsoil, depth and mineralization of groundwater and phreatic evaporation in the experimental area under natural conditions; simulation was done of the relationship between phreatic evaporation and groundwater table; quantitative analysis was conducted of the effect of groundwater table and mineralization on salinity of the topsoil; and in the end an empirical model was established for relationships of salt content in the topsoil with water table and mineralization of the groundwater. Results show that within the 5~50 cm soil layer, soil water content (SWC) increases with depth;. the effects of water table and mineralization of the groundwater are significant on salinity of the topsoil; and soil salt content is in a positive linear relationship with mineralization of the groundwater when groundwater table is a const, but in a negative linear one with groundwater table when mineralization of the groundwater is a const. The phenomenon of surface accumulation of soil salts indicates that soil salt content increases with increasing cumulative phreatic evaporation regardless of groundwater table and salt accumulation rate in the topsoil decreases with increasing depth of the groundwater table. The salt accumulation rate in the topsoil of a deserted land with groundwater table deep at 25 cm is twice as high as that with groundwater table deep at 50 cm. The findings of the study could serve as scientific basis for amelioration of salt-affected soils and prevention of soil secondary salinization.

Abstract:The commonly used method for determining exchangeable bases is to repeatedly leach a soil sample with 70% ethanol (CH₃CH₂OH) solution, and then treated with the mixture of 0.1 mol L^-1 ammonium chloride (NH₄Cl) and 70% ethanol (CH₃CH₂OH), 8.5 in pH, several times for extraction, and in the end, content of K , Na , Ca² and Mg² in the extractant is determined, separately. However, this method is complicated and time-consuming in operation and repeated extraction may increase dissolution of carbonate in the soil solution, thus making results of the determination tend to be higher. Based on the above-mentioned, tests were conducted of 10 ion exchangers different in concentration of NH₄Cl and NH₄OAc and in pH for comparison in solubility of carbonates and content of exchangeable Ca² and Mg² . Results indicate that the mixture of 1mol L^-1 NH₄Cl and 70% CH₃CH₂OH, 8.5 in pH is the most suitable one. The new method goes like this, wash a soil sample off salts with 70% CH₃CH₂OH first and then treat the sample with the mixture of 1mol L^-1 NH₄Cl and 70% CH₃CH₂OH 8.5 in pH for extraction, only once, and in the end, concentration of K , Na , Ca² and Mg² in extractant is determined. To sum up, this method not only simplifies the operation procedure, but also effectively inhibits dissolution of carbonate in the calcareous soils, thus lowering deviation of the determination.

Abstract:Biochar is a kind of highly aromatized substance with very stable physical, biological and chemical properties, and hence deemed as a measure of great potential for carbon sequestration. However, once biochar is applied into soil, it may expedite mineralization of native soil organic C, which is called “priming effect”. In this study, biochars was produced out of C4 plant, Miscanthus giganteus at 350℃ (BC350) and 700℃(BC700), and then amended separately into two soils, 3.70 and 7.60 in pH that had long been cultivated with C3 plants for in-lab incubation at 25℃ for 180 days. The respiration of CO₂ and δ¹³C were measured at set intervals during the incubation to verify andquantify priming effects of the biochars. Results show that in the soils amended amended with biochar, BC350, in particular, mineralization of organic carbon was obviously higher, that is to say, significant positive priming effect was observed. The priming effect in the acid and alkaline soils was CO2-C 250 and 319 mg kg^-1 soil, respectively. Besides, mechanisms of the priming effects biochar are also discussed from the angle of physics, chemistry and biology in this paper.

Abstract:Effect of long-term application of chemical fertilizers on content of organic carbon (SOC) in paddy soil was analyzed with the meta-analysis method. Results show that the practice increased SOC content in the top soil layer of the paddy field by 1.00 ± 0.23 g kg^-1, or by 1.06 ± 1.01 times as compared with control (CK). Analysis reveals that fertilization increased root biomass of the crop and hence input of carbon, and relatively sufficient nutrient supply from chemical fertilizer led to higher soil carbon sequestration efficiency. These two are believed to be the causes of higher SOC content in paddy field under long-term chemical fertilization. However, the effect of chemical fertilization varied with the rotation system. It was not so significant under the rotation system of rice-rice-upland crop, but was under the systems of rice-upland crop and rice-rice. One-way ANOVA analysis shows that in paddy fields, the same in fertilization, SOC content was the highest in the field under the system of rice-rice-upland crop, and little difference in SOC content was found between the other two rotation systems. Although application of chemical fertilizer significantly increases SOC content, it is essential to take into account comprehensively the emissions of greenhouse gases from the processes of manufacturing and transporting chemical fertilizers, besides the contribution of fertilization to global warming.

Abstract:Three different plant communities typical of the forest region of the Yanhe River watershed in the Loess Plateau were selected as subjects in study to explore effects of vegetation community on content and composition of organic carbon and activities of soil enzymes in soil aggregates, and relationships between organic carbon and enzyme activities, Results show that in all the three soils, regardless of vegetation community, soil aggregates in the 0~10 cm soil layer were higher than those in the 10~20 cm layer in content of organic carbon regarless of fraction and in activity of all soil enzymes, except for ployphenol oxidase, which was higher in the 10~20 cm soil layer than in the 0~10 cm soil layer under the Quercus liaotungensis community; that in terms of soil organic carbon content in soil aggregates the vegetation communities displayed an order of Quercus liaotungensis community > Robinia pseudoacacia community > Sophora viciifolia community, while the three vegetation communities did not show any consistent trend in soil enzyme activity, and the content of organic carbon and the activity of oil enzymes increased with increasing particle size of soil aggregates or increased first and then declined afterwards; significant positive relationships were observed of the activities of sucrase, cellulase and β-D-glucosidase with soil organic carbon of all forms, but no such relationships were of the activities of ployphenol oxidase and peroxidase with soil organic carbon; that in the soils under the Quercus liaotungensis and Shrub Sophora communities, the fractions of soil aggregates displayed an order of |<0.25 mm| > |2~0.25 mm| > |5~2 mm| > |>5 mm| in activities of sucrase, cellulase and β-D-glucosidase, but the fraction of 2~0.25 mm aggregates was the highest in activities of loyphenol oxidase and Peroxidase in both of the soils and in the soil under Black Locust community the fraction was the highest in activities of all the soil enzymes; and that higher activity of soil β-D-glucosidase contributed to the increase of soil organic carbon of all the forms, that of soil sucrase and β-D-glucosidase did to the increase of soil active organic carbon, and that of soil Ployphenol oxidase did to the accumulation of humus carbon.

Abstract:Samples of Ultisols different in erosion degree (slight, medium and severe) were collected in Central China and treated with the drying-wetting sieving method for different fractions of water-stable aggregates, >0.25 mm in particle-size. Carbon contents in different components of fumic acid (humic and fulvic acids) in these aggregates were analyzed for characteristics of humic acid in composition, and effects of amendment of different concentrations (0.06 and 0.6g L^-1) of humic acid in the fractions of aggregates from soils different in erosion degree explored. Results show that with erosion aggravating, the content of humic acids in Ultisols and water stable aggregates decreased. In Ultisols slight and medium in erosion, HA carbon content is higher in water-stable aggregates, >4 and 2~4 mm in particle size than in water-stable aggregates, 1~2, 0.5~1 and 0.25~0.5 mm in particle size. In Ultisols the same in erosion degree, fractions of aggregates did not differ much in FA carbon content, except for soils severe in erosion degree, where the fraction (2~4 mm) differed sharply from the fraction (1~2 mm) in FA carbon content. HA/FA ratios in all the Ultisols different in erosion degree were generally less than 1 and the Ultisols medium in erosion degree were higher than those slight or severe in erosion degree in HA/FA ratio in all fractions. Humic acid composition was significantly positively related to content of water-stable aggregates (>0.25 mm), and the correlation coefficients of HA carbon content were the highest (r=0.85^** ，n=19). After amendment of humic acid at 0.06 or 0.6 g L^-1, the contents of all fractions of aggregates increased in all the soils different in erosion degree, and the extent of the increase was higher in 1~2, 0.5~1 and 0.25~0.5 mm fractions of aggregates than in 2~4 and >4 mm fractions of aggregates.

Abstract:Batch isothermal equilibrium experiments were conducted to investigate phosphate adsorption by red soil colloids with addition of citric acid, and effects of two different treatments, (A) removing or (B) retaining supernatant after the samples reached equilibrium on lead immobilization by red soil colloids. Results show that citric acid inhibited phosphate sorption on red soil colloids, and the effect intensified with increasing citric acid concentration. When the Langmuir equation was used to fit isothermal adsorption curve of phosphate on red soil colloids, the adsorption reaction constant (K), the maximum adsorption quantity (X_m) decreased with increasing initial concentration of citric acid. And the two treatments affected differently lead immobilization capacity of red soil colloids. On the whole, lead immobilization capacity was lower in Treatment A than in Treatment B, and increased with increasing initial P concentration and P adsorption rate, but, decreased with increasing citric acid concentration. In Treatment B, Pb immobilization capacity peaked when the initial citric acid concentration was 0.1 mmol L^-1 and initial phosphate concentration was lower than 0.4mmol L^-1, which indicate that in this condition, the coexistence of phosphate and citric acid jointly promote lead immobilization by red soil colloids.

Abstract:Ecological stoichiometric ratios of C, N and P are important characteristics of the process, and function of ecological system. robinia pseudoacacia featuring fast-growing, strong adaptability and tolerance of aridity and sterility, is a major tree species in reafforestation for soil and water conservation in the Loess Plateau.With robinia pseudoacacia forests on the Loess Plateau as subject, a study was carried out on ecological stoichiometry of carbon, nitrogen and phosphate in leaf-litter-soil systems different in aspect and their correlations. Results show that: On both shady and sunny slopes, in term of C:N, the three components of the systems were in order of leaf > litter > soil, while in term of C:P and N:P in the order of litter > leaf > soil. There was no significant difference between sunny and shady slope in C:P，C:N and N:P in leaf，litter and soil (p>0.05); but there were between the two in leaf，litter (p<0.05). In soil C:P，C:N and N:P were all higher in the 0～10cm soil layer than in the 10～20cm soil layer, but the difference was not significant(p>0.05); No matter on sunny or shady slope, leaf was positively related to litter in C:N. On sunny slope, the positive correlation between leaf and litter in N:P was significant. While, on shady slope, the positive correlation between litter and soil in C:N was in the 0～10cm soil layer.

Abstract:Light and pH are key factors regulating biological iron redox process in soil anaerobically. Samples of paddy soil were prepared into slurry using deionized water and pH buffer, and then incubated anaerobically under dark and, illumination and constant temperature, to investigate variation of soil pH in the process and effect of pH on iron redox cycle. The relationships of pH with, Fe(II) and water soluble inorganic carbon during the anaerobic incubation were also explored. Results showed that soil pH could be altered by illumination during the anaerobic incubation, decreasing under dark, and rising and then declining under illumination, with time elapsing. Iron reduction occurred when pH was in the range from 4 to 9, and peaked at pH 7, reaching 128.5 μmol g^-1, and it was inhabited under dark when pH was adjusted to 4 or 9. Under illumination, Fe(II) produced from iron reduction was re-oxidized when pH was in the range of 6~8. The re-oxidation was enhanced up to 77.13%, or 49.17 μmol g^-1 when the buffer initial pH was 7. A significant linear positive relationship was observed between Fe(II) and WSIC during the anaerobic incubation under dark, but significant negative ones were of pH with Fe(II) and water soluble inorganic carbon (WSIC).

Abstract:In order to explore effects of straw incorporation plus application of chemical fertilizer varying in NPK ratio on soil temperature and moisture conservation and soil-root biological properties, a field experiment was conducted. Results show that the treatments of straw incorporation plus application of chemical fertilizer varying in ratio raised soil temperature at 8:00 and 20:00 and lowered at 14:00 in all the growing periods, compared with the control. Analysis of soil temperature shows that the range of its daily variation was narrower in the treatments than in the control and the difference was significant. However, the difference was getting less significant with the increasing soil depth, which means that the soil temperature regulating effect of the treatments was declining gradually. Besides, the treatments significantly increased the populations of bacteria, actinomyces, fungi, ammonia-oxidizing bacteria, aerobic authigenic nitrogen-fixing bacteria, nitrite bacteria, phosphorus bacteria and aerobic cellulose decomposing bacteria, but generally the difference between the treatments in the effect was not significant. All the treatments, except Treatment SNP₁ (3 000 kg hm^-2 crushed straw 150 kg hm^-2N 75 kg hm^-2 P₂O₅), were higher than the control in activity of catalase, urease and invertase, but the differences were not very significant. The findings demonstrate that straw incorporation plus application of chemical fertilizer, though varying in ratio, may reasonably regulate, increase the population and activity of soil microbes and help improve the soil eco-environment. Among the treatments, Treatment SNPK₁ (3 000 kg hm^-2 straw 150 kg hm^-2 N 75 kg hm^-2 P₂O₅ 37.5 kg hm^-2 K₂O) and Treatment SNPK₂ (3 000 kg hm^-2 straw 225 kg hm^-2N 112.5kg hm^-2 P₂O₅ 56.3 kg hm^-2K₂O) are the most significant in this effect.

Abstract:To investigate soil microbe using of different types of carbon sources under four types of reestablished forests or treatments (mixed broadleaf plantation, pure broadleaf plantation, mixed coniferous-broadleaf plantation, pure coniferous plantation) with a naturally restored fallow land as control, the microResp method was used. Results show that the capacity of soil microbes using mono-carbon source varied significantly with duration of incubation (6 h or additional 18 h) and soil depth (0~10 or 10~20 cm), and also with the type of forest. In terms of the capacity, the forests followed the order of naturally restored fallow land > mixed broadleaf plantation > pure broadleaf plantation > mixed coniferous-broadleaf plantation > pure coniferous plantation. Shannon index (H) and evenness index (E) indicates that the five treatments followed an order of mixed broadleaf plantation > pure broadleaf plantation > mixed coniferous-broadleaf plantation > pure coniferous plantation in soil microbial community diversity. All the treatments, except the control did not differ much from each other in soil microbial diversity and abundance. Principle components analysis indicates that the fifteen carbon sources selected in this study were sufficient to elucidate differences between the four plantations in soil microbial functional diversity, and that sugars were the sensitive carbon source to forest soil microbes.

Abstract:Soil microorganisms play an important role in soil carbon and nitrogen recycling. It is, therefore, necessary to study responses of soil microorganisms to warming for better understanding soil biological processes under global warming. The technique of open-top chambers (OTC) was used in an experiment to explore responses to warming ( 1.1~1.9℃) of soil enzymes in activity and soil microbes in biomass, community structure and respiration in the soil of the tundra ecosystem on the Changbai Mountains. OTCs were established in June, 2010 and kept the temperature inside 1.1 to 1.9 ℃ higher than the air temperature around for three growing seasons consecutively. Results show that warming did not affect much the activities of soil sucrase (0.34 and 0.26 mg g^-1 72 h^-1) or cellulase (58.1 and 45.9 mg g^-1 24 h^-1), but did increased the activity of soil urease (0.82 and 0.46 mg g^-1 24 h^-1) by 80.1% and of soil catalase (1.18 and 1.07 ml KMnO₄ g^-1 h^-1) by 10.1%. No significant difference was observed between warming OTCs and control plots in soil microbial biomass carbon (0.85 and 0.75 mg g^-1), microbial biomass nitrogen (0.07 and 0.06 mg g^-1), microbial biomass phosphorus (0.013 and 0.011 mg g^-1) and soil microbial respiration (6.1 and 6.3 μmol m^-2 s^-1). Correlation analysis indicates that the significant monthly variation of soil microbial biomass was related to changes in soil water content and soil organic matter. Warming altered soil microbial community structure, but did not affect much carbon-recycling-related soil enzyme activites, soil microbial biomass and soil microbial respiration. Maybe the warming is not long enough in duration or not great enough in magnitude to significantly alter the activity of soil microbes.

Abstract:A pot experiment was conducted to study effects of ameliorants on soil properties and rice yield of acid sulfate paddy soil. Results show that soil pH, in the range of 3.47~4.90, was significantly and negatively correlated with exchangeable H and Al³ , but positively with soil available iron (Fe), sulfur (S). Compared with treatments CK and NPK, all the amelioration treatments showed varying significant effects of increasing crop yield and improving soil properties. Inorganic ameliorants, e.g. calcium magnesium phosphate, home-developed ameliorant, lime and alkali residue, were better than organic ones, such as humic acid, refined organic manure and alkaline organic manure. The amelioration effects were mainly reflected in higher soil pH, available Ca and available Mg, lower soil exchangeable H and Al³ , better environment for root growth and hence higher nutrient uptake by rice shoots and higher rice grain yield. To sum up, acid hazard (including active acid and potential acid) is the main limiting factor in rice production in acid sulfate paddy soil. Alkalescent and Ca- or P-rich inorganic substances, such as calcium magnesium phosphate, home-developed ameliorant, lime, etc. are proper ameliorants for acid sulfate paddy fields in agricultural practice.

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