Abstract:In view of the fact that the current soil moisture retrieval from remotely sensed data is low in accuracy, a new integrated approach termed “Co-inversion of land surface soil moisture by integrating optical, thermal infrared and passive microwave remote sensing data” was proposed. Specifically, the MODIS optical and thermal infrared bands are used to derive soil moisture benchmark, and the AMSR-E X-band data to estimate daily variation of land surface soil moisture. Then the two are integrated, building up a co-inversion model for soil moisture retrieval over a large area. Xinjiang was cited as experiment zone. A total of 365 in-situ measured soil moisture values were collected from a typical area and used to test the proposed inversion model. Verification analysis with the ground truthing data of the study area shows that the co-inversion of optical/thermal and microwave remotely sensed data displays higher correlation coefficient and smaller root mean square errors (RMSE) than any inversion using one single data source.

Abstract:Based on X-ray mineral identification, particle-size analysis, electron microscopic identification and field observation of purple soil and purple mudstone, mineral composition and particle size composition as well as susceptibility to erosion were studied. Results show that little difference was observed in mineral composition and content between purple soil and purple mudstone, which are both mainly composed of quartz and feldspar, plus Smectite-dominated clay mineral. They are all very close in particle size and consisted dominantly of fine silt and clay. The micro-structure of purple soil appears to be mainly of clasts with pores cemented, and some of granulars cemented through contact and of granular cemented with lumps. Clay played a key role in cementing, of which only about 3% was attributed to Fe₂O₃, chemical agglutinate. The microstructure of purple mudstone is characterized predominantly by miniature laminate structure and micro-lump structure, which take up the main part. The high smectite content indicates that both purple soil and purple mudstone are dilatable soils. Purple soil and purple mudstone frequently swell and shrink when the weather is humid, making them susceptible to physical weathering and erosion and their miniature block structure, miniature laminate structure and dense micro-pores are also important causes of its poor erosion resistance. These structures of the purple mudstone are mainly formed during the diagenetic process, as a result of the compression during the diagenetic process of the large amounts of spheric and ellipsoidal clays formed during primitive sedimentation.

Abstract:Soil profiles of double-layer structure with Yellow-brown Earth (YBE) overlying Red Clay (RC) are commonly seen in the Xuancheng-Langxi-Guangde region, Anhui Province. Particle-size and geochemical characteristics of a selective YBE-RC soil profile in Langxi County, Anhui Province were studied. Results show that the YBE of the studied profile is quite coincident in particle-size composition and geochemical characteristics with that in Xuancheng and Jiujiang, and also the Xiashu Loess in Zhenjiang, Jiangsu Province, which strongly suggests that the YBE in the study areas shares the same provenance with the Xiashu Loess, widely distributed along the Yangtze Valley. The Langxi profile is vertically even in particle-size and geochemical characteristics, and also shows continuous transition between YBE and RC without any depositional interruption. This suggests that the underlying RC of the profile shares a similar origin with the YBE and the Xiashu Loess and was derived from typical aeolian-dust deposition. Compared with the YBE, however, the underlying RC is finer in particle-size and more intensively weathered. The transition from the RC to the YBE might record a great paleoclimatic change at the early stage of the Late Pleistocene, when the Last Interglacial ended and the Last Glacial began. However, more work needs to be done to find some irrefutable chronological evidence.

Abstract:Intensely leached soil is a unique type of soil and has an important position in the soil classification system. For its classification, bleached soils on the second, third, fourth and fifth terraces of Mingshan County, West Sichuan where they are widely distributed, were investigated and sampled in field and analyzed in laboratory. Following the principle and methods of Chinese Soil Taxonomy (CST), their diagnostic horizons were identified and their diagnostic characteristics, such as anthrostagic epipedon, hydragric horizon, albic horizon, anthrostagnic moisture regime, redoxic features, determined; and by means of sequential searching, they were sorted into Anthrosols in order, Stagnic Anthrosols in suborder, Hapli-Stagnic Anthrosols and Fe-accumulic –Stagnic Anthrosols in group, Albic Hapli-Stagnic Anthrosols, Albic Fe-accumulic –Stagnic Anthrosols, and Typic Fe-accumulic –Stagnic Anthrosols in subgroup, and according to the Genetic Soil Classification of China (GSCC), they fell into the subgroup of Bleached Paddy Soil. Comparatively speaking, CST can more accurately discriminate soils, which favors standardized management of soils. However, CST still needs to be further perfected.

Abstract:Soil-environment models can be of great importance to proper understanding of relationships between soil properties and environmental factors, and to predicting and mapping of soil properties, as well. A gully area where the “Grain for Green” policy had been implemented for years was selected in Changwu County, Shaanxi Province, a Loess Plateau region in China. A total of 72 surface soil samples were collected, and 3 fourths of the samples were used as a calibration set of samples and the rest as a validation set. Several easily aquired environmental factors, such as topographic factor, vegetation index and wetness index were used in a PLSR (partial least squares regression)-based soil-environment model established for the study. Quantitative analysis of relationships between environmental factors and soil properties of the samples was done. Results show that soil properties, including available potassium, total potassium, organic matter and total nitrogen, were significantly correlated with environmental factors. The PLSR-based model could well explain 23% to 27% the spatial variability of soil properties. Compared with the stepwise regression model used, the PLSR model was much better at characterizing soil-environment relationships with better fitting and prediction accuracy, suggesting that the PLSR-based model is applicable to prediction of soil properties of similar regions.

Abstract:Clay mineralogical and chemical elements analyses of the loess-paloesol deposit of Tawan Profile in Linxia Basin indicated that the climate of Linxia experienced a four-phase alteration, i.e. relatively warm/humid (92.4～78.8 ka) - cold/arid (78.8～59.8 ka) - relatively warm/humid (59.8～47.7 ka) - cold/arid (47.7 ka to present) since the last interglacial period. The loess-paleosol deposit of the profile was dominated with illite, chlorite, mixed layer illite-smectite and minor palygorskite. Palygorskite was ubiquitous in the sediment, suggesting that on the whole the region was relatively arid throughout the period. w(TiO₂)/w(Al₂O₃) ratio of the loess-paleosol deposits indicated of the same origin. The loess-paleosol alternation was attributed to different weathering intensities, which were closely related to rainfall and temperature conditions in the period. Relative proportions of clay minerals, CIA values, w(Al₂O₃)/w(Fe₂O₃), w(SiO₂)/w(Al₂O₃), w(SiO₂)/w(Fe₂O₃) and w(MgO)/w(Al₂O₃) varied quite sharply during the warm and humid period, but rather stable during the cold and arid period. The variation of the clay mineralogical features and major elements indicated significant cooling events occurred at the period of 92.4～78.8 ka and 47.7 ka ～ present, , suggesting unstability of the climate environment in Linxia since the last interglacial period, which was probably related to the winter and summer monsoons in the plateau.

Abstract:Watershed evapotranspiration is an important process of surface water movement. Water and soil conservation measures influence this process by altering properties of the underlying surface. To reveal evaportranspiration characteristics of watersheds different in adoption of water and soil conservation measures, two watersheds, Jiuyuangou and Peijiamao in a hill-gully region of the Loess Plateau, were selected as subjects for estimation of evapotranspiration from different underlying surfaces using the energy-balance based SEBAL remote-sensing model. Results show that the surface albedo of the study area varied mostly in the range of 0.1~0.2; the NDVI of the watershed under different water and soil conservation managements displayed different seasonal variation; the net radiation fluctuated in the range of 400～800W m^-2, the sensible heat flux of 50~200W m^-2, and the soil heat flux of 100~200W m^-2；the daily evaportranspiration of Jiuyuangou, which is better managed in water and soil conservation, is slightly less than that of Peijiamao. Lands different in land use followed the order of check dam > orchard > woodland > grassland > terrace > slope land in daily evaportranspiration. Analysis of rationality of the calculation from various angles suggests that the estimation of watershed evapotranspiration using the SEBAL model is reliable.

Abstract:An indoor test was carried out to measure time it takes for water to go from infiltration to waterlogging in 8 types of soils homogenous in texture. To predict the time, different forms of variable combination were adopted and principles of mathematical statistics used. Results show that it is feasible to forecast the time using five conventional soil physical parameters, i.e. soil bulk density, initial moisture, sand content, clay content and water supply intensity; forecasting using the multivariable linear prediction model is more or less the same in accuracy as that using the multivariable linear prediction model, except that they yield different parameters, and that the former is more simple; and when using any one of the two, relatively speaking the more factors are taken into account, the more precise the prediction would be.

Abstract:Artificial neural network (ANN), ordinary kriging (OK) and sequential Gaussian simulation (SGS) was introduced separately to simulation, interpolation and prediction of spatial distribution of soil salinity in a field typical of the coastal polder in North Jiangsu, to work out optimal structures and parameters of various methods for comparison of the methods in efficiency of predicting distribution characteristics and spatial structure of soil salinity. Results show that all the three methods, ANN, OK and SGS, were quite good at simulating and predicting spatial distribution of soil salinity and displayed quite high accuracy in the simulation, interpolation and prediction. The spatial distribution obtained by the ANN method was the most continuous and smooth, while that obtained by the SGS method was relatively discrete and fluctuant. The ANN method exhibited a relatively high prediction accuracy at sites of low soil salinity, but a much lower accuracy than the SGS and OK did at sites of high soil salinity. Furthermore, the prediction of SGS tallied the most with the fluctuation trait of measured value, and the narrowest fluctuation range was observed in prediction using the ANN method. The SGS method was better than the ANN and OK methods at reflecting spatial structure and fluctuation of the random variables of data, indicating that SGS is superior to ANN and OK as a whole. The findings may be cited as reference for precision assessment and high-efficiency amelioration of saline soil in coastal polders.

Abstract:Soil secondary salinity and fresh water shortage are two major problems limiting crop growth and yield improvement. Therefore, analysis of effects of sand mulching on soil water infiltration, evaporation, and salt transportation is of some great significance to optimizing the method of sand mulching in arid regions. A laboratory simulation experiment was conducted to study processes of soil water infiltration, soil water evaporation, and salt transportation under sand mulchings different in thickness, in the condition of constant water head infiltration and simulating steady evaporation. The sand used in this study varied from 0.2 mm to 2 mm in particle size. The experiment was designed to have four treatments in sand mulching, i e., 0 (control), 1.7, 3.6 and 5.7 cm, in thickness of the sand layer on the surface of soil. Results show that (1) Sand mulching has an obvious inhibitory effect on soil water net infiltration, and the thicker the sand mulching the less the soil water infiltration, namely, the effect increases significantly with the thickness of the sand mulching; (2) Sand mulching dramatically reduces soil water evaporation, and the thicker the sand mulching the less the soil water evaporation, demonstrating a significant positive correlation between soil water evaporation from surface and the thickness of the sand mulching; and it was found that during the 20 days of experiment, the evaporation process in the sand mulching treatment was rather stable, and the soil water cumulative evaporation fitted a linear equation and the Rose empirical equation as well; (3) Sand mulching alters soil salt transportation and distribution in soil profile, especially reducing accumulation on the top-surface soil layer. To sum up, sand mulching significantly inhibits soil water evaporation from soil, and surface accumulation of soil salt. Sand mulching, 1.7 cm or more in thickness, is sufficient to create the effect, but it also affects net infiltration of the soil. To sum up, sand mulching significantly inhibits soil water evaporation from soil, and surface accumulation of soil salt. Sand mulching, 1.7 cm or more in thickness, is sufficient to create the effect, but it also affects net infiltration of the soil.

Abstract:Soil pH, total soil salt and eight main salt ions (K⁺, Na⁺, Ca²⁺, Mg²⁺, Cl^-, SO₄^2-, CO₃^2- and HCO₃^-) in soils under and in-between groves of Tamarix romasissima，Halostachys caspica，Halocnemum strobilaceum in two habitats, i.e. saline meadow and shrubland, were analyzed in order to explore effects of habitat and shrub species on salt island effect of halophytic shrubs in north Tarim Basin. Results show that in the saline meadow only under the grove of Halocnemum strobilaceum in the saline meadow, significant salt enrichment was observed in the soil, forming a salt island, while in the shrubland salt island effect was found in soils under all the three halophytic shrubs. That under Halocnemum strobilaceum was the most significant whereas under tamarisk the least. Data analysis further suggested that the salt island effect varied in strength with the halophytic shrub species and the habitat they grew in, that is to say, the salt island effect of halophytes and plants high in salt tolerance in salt-rich habitats is more obvious. And changes in habitat or plant species also influence to a varying extent enrichment of salt ions in the salt island. Intensified salt island effect accelerates degradation of saline meadow into halophyte-dominated desert in north Tarim Basin, Xinjiang.

Abstract:Investigations were carried out of CH₄ emission and its δ¹³C values from a rice field under continuous flooding throughout the fallow and following rice seasons. Results show that in the fallow season CH₄ flux rose from April and reached a peak value, about 6.4 mg m^-2 h^-1, in June. After rice transplanting, CH₄ flux increased quickly at the beginning of the rice season and two peaks occurred in July and August, reaching 23.1 and 29.8 mg m^-2 h^-1, respectively, which was followed by a rapid decrease. Then another peak appeared during the final drainage before rice harvest. The total CH₄ emission in the fallow season amounted to 3.3 g m^-2, accounting for 8.9% of the annual total emission. On the other hand, δ¹³CH₄ (emitted) increased gradually from -51‰ to -44‰, and then dropped back to -56‰ in the late fallow season. After rice transplanting, δ¹³C value decreased from -62‰ to -68‰ firstly and then increased swiftly to -60‰, which afterwards remained unchanged for a relatively long time. Late in the season, emitted CH₄ became ¹³C enriched again. The impact of the final drainage on δ¹³CH₄ (emitted) was remarkable. The δ¹³C value of emitted CH₄ was heavier in the fallow season than in the rice season, because the fraction of CH₄ oxidized was higher in the fallow season (60%~90%) than during the following rice season (10%~80%). Within the whole observation period, the temporal variation of CH₄ flux was positively related to soil temperature (p<0.01), but negatively related to soil Eh (p<0.01) and to δ¹³C value (p < 0.05) as well.

Abstract:Samples of Fe-leachi-Stagnic Anthrosols were collected and incubated with different rates of CaCO3 and H2SO4 amended through titration, for indoor simulation of variation of the pH buffering capacity of the soil as affected by rainfall, different in pH (2.5, 4.5 and 6.5) and nitrogen application, different in rate (0, 150 mg kg^-1 and 300 mg kg^-1), and further for exploration of effects of rainfall and N application on soil total acid induced and on leaching of mineral N. Results show that soil acidification rate ranged from 4.73 mmol H⁺ to 15.57 mmol H⁺ per column, being the lowest in the treatment with rainfall 6.5 in pH and N application zero and the highest in the treatment with rainfall 2.5 in pH and N application rate N2. Soil acidification rate increased with N application rate, regardless of pH of rainfall. In the treatment with zero N application rate, soil acid accumulated with decreasing pH in rainfall. In the treatments with N application rate being, soil acid accumulation was the highest when the rainfall was 2.5 in pH, and the lowest when the rainfall was 4.5 in pH. Leaching of nitrate induced soil acidification and the amount of acid induced by leaching of nitrate ranged from 4.24 to 13.18 mmol per column in the experiment, while leaching of NH₄⁺ consumed H⁺ at a rate of 0.01 to 0.29 mmol per column. In the treatment with rainfall normal in pH, 6.5, N application at 15 mg kg^-1 and 30 mg kg^-1 increased soil acid by 11.34 mmol and 12.96 mmol per column, respectively, which was more than it did in the treatment with rainfall 2.5 in pH (9.49 mmol per column), and in the treatment with rainfall 4.5 pH (6.87 mmol per column) and more than the amount of H⁺ rainfall 4.5 in pH brought in (0.16 mmol per column). The above findings show that application of nitrogen alone may induce more acid than acid depostion with rainfall could bring in. However, no matter whether rainfall or N application, leaching of NO₃^- plays a leading role in accelerating soil acidification.

Abstract:Based on comparison between the effects of NO₃^-, Cl^- and SO₄^2- on the adsorption of Cu²⁺ by variable charge and constant charge soils, the mechanism of the anion effect was studied. Results show that when the initial concentrations of NO₃^-, Cl^- and SO₄^2- in the systems studied were identical, the adsorption percentage of Cu²⁺ by Hyper-Rhodic Ferralsol was larger in the SO₄^2- system than in the NO₃^- and Cl^- systems, while the adsorption percentage of Cu²⁺ by Cambisol in the three anion systems were very close to each other. The adsorption percentage of Cu²⁺ by Rhodic Ferralsol in the systems containing different concentrations of NaCl differed insignificantly, suggesting the effect of ionic strength on the adsorption of Cu²⁺ by variable charge soils was small. The adsorption percentage of Cu²⁺ by Hyper-Rhodic Ferralsol in the systems containing NO₃^-, Cl^- and SO₄^2- increased with increasing pH of the media. At the same pH value, the percentage in the system containing NO₃^- was close to that in the system containing Cl^-, but lower than that in the system containing SO₄^2-. The adsorption percentage of Cu²⁺ by Hyper-Rhodic Ferralsol and Rhodic Ferralsol decreased with increasing concentration of Na₂SO₄. However, the percentages were larger in the systems containing 0.005 mol L^-1 and 0.05 mol L^-1 Na₂SO₄, but smaller in the system containing 0.5 mol L^-1 Na₂SO₄ than in the system without Na₂SO₄. On the other hand, all the adsorption percentages of Cu²⁺ by Cambisol were smaller in the systems containing different concentrations of Na₂SO₄ than in the system without Na₂SO₄. It is, therefore, concluded that kind of anion species can affect the adsorption of Cu²⁺ by soils through changing the ionic strength of the media, the degree of formation of ion-pairs and the specific adsorption of anions by soils. The mechanism of anion effect on the adsorption of Cu²⁺ is more complicated in variable charge soils than in constant charge soils.

Abstract:Through the project of soil testing and fertilizer recommendation in 2005~2009, a lot of data about soil nutrients in paddy fields were acquired. Based on the data obtained in Hubei 2008, status quo of the soil fertilities in seven rice producing regions of the province, namely, E’dong, Jianghan Pingyuan, E’dongnan, E’dongbei, E’zhong, E’xibei, and E’xinan were systematic analyzed and compared with the data obtained during the second national soil survey to explore laws and causes of the variation of soil nutrients in paddy field. Results show that presently the paddy soils in Hubei Province were 10~40 g kg^-1 or 26.1 g kg^-1 on average in organic matter, > 90 mg kg^-1 or 124.2 mg kg^-1 on average in alkalystic N, 5~40 mg kg^-1 or 13.1 mg kg^-1 on average in available P, and 50~150 mg kg^-1 or 89.1 mg kg^-1 on average in available K, and 5.0~7.5 in pH or 6.3 on average. The soil nutrients varied to a varying extent from region to region. In view of the province as a whole, the distribution of organic matter was characterized by being high in the east and south and low in the west and north, that of alkalystic N being high in the west and south and low in the east and north, and that of available K and pH both being high in the west and north and low in the east and south, while that of available P did not show any apparent rule. Compared with the findings of the second soil survey, the contents of organic matter, alkalystic N and available P increased while pH decreased as a result of long-term application of N and P fertilizers at an increasing rate and increased area and rate of straw incorporation. However, inadequate application rate of K fertilizer and the adoption of high K-demanding rice cultivar led to decrease in available K in the soil. Obviously in rice production in Hubei Province, to increase K application rate, to readjust the ratio of N:P:K rationally, and to lime the paddy fields at a proper rate while incorporating rice straw into the soil are effective approaches to raising soil fertility and preventing acidification of the paddy soils. The study also demonstrates that by making full use of the data of the project of soil testing and fertilizer recommendation and conducting systematic study of the soil nutrient data, it is feasible to obtain full knowledge of the status quo and variation of soil fertility of a region.

Abstract:Phyllostachys pracecox stands under intensive management different in history (1, 5, 10 and 15 years) in West Tianmu, Linan City, a major Phyllostachys pracecox production area, were selected for sampling of soil profiles, 0~10 cm, 10~20 cm and 20~40 cm, separately, in depth. These samples were subjected to sequential extraction for analysis of variation of contents and fractions of silicon with plantation age and soil depth. Results show that the content (0.084~0.318 g kg^-1) of available Si and its proportion (1.60%~12.3%) to soil Si in the profiles varied with the age of plantation and organic mulching, showing a curve downwards first and then turning rise . The content (2.58~5.15 g kg^-1) of amorphous Si and its proportion (75.1%~87.7%) in the topsoil increased with the age of plantation. Organic mulching promoted transformation of amorphous Si into available Si, organic Si and Fe/Mn-oxide Si. The findings of the study may be offered as reference for regulation of soil bioavailable Si in the soil of Phyllostachys pracecox stands.

Abstract:A rhizobox experiment was carried out, using boxes each separated into two compartments in the middle with nylon net and planted with aerobic rice and/or watermelon, both inoculated with Glomus etunicatum of arbuscular mycorrhizal fungi (abbreviated as AM fungus), to investigate formation of arbuscular mycorrhizal hyphal links between the roots of the two plants, and their effects on expression of OsPT11, phosphate transporter in rice, and uptake of phosphorus. Results showed that when neither aerobic rice nor watermelon was inoculated with AM fungus, no mycorrhiza colonized and no expression of OsPT11 was observed either in rice roots; (2) When the watermelon compartment was incubated, the hyphal links formed between aerobic rice and watermelon induced colonization of mycorrhiza on rice and expression of OsPT11 in the root system of rice; (3) Inoculation either directly or indirectly through hyphal links displayed the same effect on colonization of mycorrhiza in aerobic rice and watermelon, making the colonization rate over 80% and over 70%, respectively; and (4) In the aerobic rice/watermelon interplanting system, inoculation significantly increased availability of phosphorus in the rhizosphere of both aerobic rice and watermelon as compared to control, and the content of total phosphorus decreased in the shoots of rice, but increased in the shoots of watermelon.

Abstract:To analyze by comparison AOB amoA gene diversity of three cultivated soils, i.e. black soil in Hailun (HL), chao soil in Fengqiu (FQ) and red soil in Yingtan (YT) which are located in different climatic zones in East China. Total DNA of soil microbe was extracted by the direct lysis method, and amplified with specific primers of AOB amoA gene, amoA gene libraries of the three soils were thus constructed and analyzed with the RFLP method for diversity. The number of clones in amoA gene library was 49, 50 and 48 in HL, FQ and YT respectively, and their corresponding number of OTU (Operational Taxonomic Unit) was 10, 10 and 14, of while 4 were common in all the three samples. YT was the highest in index of amoA gene diversity while FQ the lowest; The similarity index between HL and FQ in AOB community was 70%, between HL and YT was 50%, and between FQ and YT was 42%, which indicates that AOB distribution has geographic characteristics. Seventeen AOB amoA gene sequences could be sorted into six clusters belonging to two genera, Nitrosospira and Nitrosomonas. All the three soils have an abundance of AOB, thus implying autotrophic AOB play a crucial role in nitrogen cycling in cultivated soils.

Abstract:With a Karst primeval forest (KPF) set as check, effects of human disturbance on community structure of soil bacteria were analyzed using the 16S rRNA genes PCR-RFLP and sequencing techniques. Results show that Proteobacteria were the dominant bacterial group in all the four soils subjected to different patterns of human disturbance, primeval forest (KPF, free of disturbance), naturally restored land (KNR), cropland (KMS) and grassland disturbed by long-term grazing and burned annual in winter (KGB), separately, accounting for 41.3% of the total clone libraries. As compared to KPF, the proportions of Proteobacteria were decreased by 30.2%~47.4% in disturbed soils (KNR, KMS and KGB). Similar distributions of the subgroups of Proteobacteria were found among KPF, KNR and KGB, being in the order of α->δ->β->γ-Proteobacteria, but in KMS it was in the order of δ->α->β->γ-Proteobacteria, which indicate that the effects of natural restoration and grazing and burning in winter were limited on recovery of soil Proteobacteria, but obviously positive on distribution sequence of the four subphyla. In KNR, the subphylum of α-Proteobacteria was well restored, being 130% higher than in KMS. In the four soils, 16.5% of the total clones were sorted into Rhizobiales, which was the highest in KPF, about 1.6 to 3.7 times higher than in the other three soils. Based on the above-described findings, it is concluded that planting of native nitrogen-fixing plants in combination with inoculation of native nitrogen-fixing microorganisms may be considered as one of the measures in future to restore degraded Karst ecosystems.

Abstract:Field surveys were carried out to investigate earthworm species in soils in 7 land-use types in salinity transforming region of Quzhou Country, Hebei Province and indoor incubation was done to study influences of earthworm population to soil biological parameters. Results show that (1) 5 species of earthworms were found, belonging to 5 genera and 3 families, with Eisenia fetida in dominance over 60% in number of individuals, and two species of Aporrectodea trapezoides and Eisenia fetida were widely distributed in this area, the present frequency in samples were 74% and 44% respectively, as the dominant species; (2) the order of earthworm population density and biomass change tendency in different land use types was : vegetable garden > vertical no-tillage > clean-stubble no-tillage > market vegetable plot > traditional corn land > orchard > abandoned land. The earthworm average population density and biomass were highest was in vegetable garden, achieving 272 Ind. m^-2 and 68.04 g m^-2 respectively; (3) Among the relationships between earthworm population characteristics and biological properties of soils the earthworm population density and the species number were positively correlated with soil basal respiration and microbial biomass carbon content significantly (p< 0.01 ), but soil basal respiration quotient existed significantly negative correlation (p< 0.01 ); (4) the effects of earthworm population density and biomass on soil microbial communities were significant. The greater the earthworm biomass and population, the higher the contents of soil organic matter, available nitrogen, available phosphorus, available potassium, and conversely contrary. Moreover the lab experiment also indicates that soil protozoa, microbial carbon, and microbial nitrogen tended to increase with the rise of the number of earthworm individuals. The characteristics of earthworm population can also be used as indicators in evaluating soil biological fertility, just like soil biological indicators and soil chemical indicators.

Abstract:Electric and electronic wastes (e-wastes) contain plenty of toxic and hazardous materials, such as polychlorinated biphenyls (PCBs). Improper dissembling of these e-wastes can cause pollution to the soil, water and air, thus posing a potential threat to the ecological environment and human health. Bioremediation is an option that may accelerate removal of various environmental contaminants using the functions of biomes absorbing, metabolizing and biodegrading the contaminants. Based on the subject used, bioremediation can be divided into phytoremediation, microbial remediation, animal remediation, and joint remediation. Based on the author's research work, this paper summarizes characteristics of PCBs pollution of the soils around an e-wastes dissembling typical zone along the coast of Southeast China, and introduces status quo of the researches on technologies for and mechanisms of microbial remediation, phytoremediation, and phyto-microbial joint remediation of PCB-contaminated soils, and proposes the future research trends, with a view to providing a theoretical reference for in-depth study on bioremediation of the soil environment, and protection of food safety and human health in polluted areas.

Abstract:Application of nitrogen fertilizers in agricultural systems is one of the most important factors influencing the global nitrogen cycle. Nitrogen fertilizers can improve crop production, but also have much influence on ecological environment. Nitrogen fertilizers in ammonium form (NH₄⁺) is easily transferred into nitrate form (NO₃^-) in dry land by nitrification. However, only a small portion of the formed NO₃^- can be taken up by plants, while a large amount will be leached or released into the air through denitrification, which results in severe nitrogen loss. In nature some plants can excrete through their roots some compounds that have the function of inhibiting nitrification and thus can be characterized as biological nitrification inhibitor (BNI), which may significantly improve nitrogen use efficiency in soil. This review illustrates the origin, excretion and regulation of the substances, mechanisms of their function and potential of their application, and also discusses prospects of their application to high efficiency management of nitrogen in agricultural systems.

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