Abstract:Mechanism of gravitational erosion in the slope-gully system of the Loess Plateau was explored with the aid of the finite difference software, FLAC^3D, while numerical simulation of stress field and displacement field of the system and analysis of effect of rising elevation of the erosion base level on slope-gully stability and gravitational erosion was performed. Results show that the slope-gully system tends to stabilize with the rising elevation of the erosion base level; its maximum displacement, safety factor and landslide probability vary within the exponential function distribution range. Its fitting equation is high enough in accuracy to be used in qualitative and quantitative analysis of gravitational erosion of the system. The geometric shape of concave slope can effectively reduce stress concentration, mitigate the likelihood of gravitational erosion, The displacement in the upper part of the slope-gully system appears mainly in the form of “settlement”, tops and slopes of barren hills are the most susceptible to gravitational erosion; with rising elevation of the erosion base level, displacement to whatever direction is decreased to a various degree.

Abstract:Chronosequential soils derived from basalts formed through volcano eruptions during different ages since the Quaternary period from 0.58 Ma to 6.12 Ma BP on Leizhou Peninsula, South China were samples for analysis of changes in some physiochemical properties of the soils. Results show that (1) soil bulk density increased with soil depth and quite closely related to soil age, which suggests that soil bulk density could be deemed, to a certain degree, as an indicator of soil genetic horizons and development; (2) Fe_d, Fe_d/Fe_t, Al_o and Al_o/Al_d, were quite closely related to soil age, as well, suggesting that they are good indicators of soil development and relative age of the soil, while Fe_o, Al_d and Si_o were not, suggesting they were not good indicators either; and (3) the common indicators of clay weathering and development, such as Sa (SiO₂/Al₂O₃), Saf (SiO₂/ (Al₂O₃+Fe₂O₃)), ba ((Na₂O+K₂O+CaO) / Al₂O₃), A ((SiO₂+CaO+K₂O+Na₂O) / (Al₂O₃+CaO+K₂O+Na₂O)), B ((CaO+K₂O+Na₂O) / (Al₂O₃+SiO₂+CaO+K₂O+Na₂O)), WI (\[(2Na₂O/0.35) + (MgO/0.9) + (2K₂O/0.25) + (CaO/0.7)\]×100), CIW (\[Al₂O₃/ (Al₂O₃+CaO+Na₂O)\]×100), CIA (\[Al₂O₃/ (Al₂O₃+CaO+Na₂O+K₂O)\]×100) were not significantly related to soil age, suggesting that they are not good indicators of soil weathering degree, while changes in Sa and Saf of clay and migration rate of element Si to a certain extent revealed formation and enrichment of biogenic silica, which may influence Si leaching in soil.

Abstract:Particle-size distribution of five typical profiles of Quaternary red clay in Yichang and Xianning, Hubei Province, and Changde, Changsha and Zhuzhou, Hunan Province, the middle reaches of the Yangtze River, was analyzed to study origin of the Quaternary red clay and its implications for evolution of the paleo-environment in South China. Results indicate that all the profiles demonstrate obvious dualistic structure in particle-size composition, e.g. in the upper part of the profile (0～320 cm of the Yichang profile, 0～220 cm of the Xianning profile, 0～270 cm of the Changde profile, 0～280 cm of the Changsha profile, and 0～150 cm of the Zhuzhou profile), the clay is fine and uniform in particle size and low in content of sands, mostly <1%, and relative high in content of coarse silt or basic component of aeolian dust fraction, accounting for 34.38%, 32.29%, 32.48%, 31.69% and 31.86% on average, respectively. Moreover, the particle-size distribution frequency graphs of the red clay samples are similar to those of the Quaternary red clay in Xuancheng, Anhui Province, and also show some inherited patterns from the Xiashu loess in Zhenjiang, Jiangsu Province. All the above reflect the aeolian characteristics of the red clay in the upper parts. However, the lower parts of the profiles is significantly different from the upper in particle-size composition. They often have gravels and a relatively high content of sands, showing a significant vertical variation of different particle-size fractions along the file. Furthermore, the files are also significantly different from those of the Quaternary red clay in Xuancheng, Anhui Province, and the Xiashu loess in Zhenjiang, Jiangsu Province, in particle-size frequency graph, demonstrating diluvial or alluvial properties. The dualistic structure of the Quaternary red clay in the middle reaches of the Yangtze River manifests variability and complexity of the paleo-environment in the study area. After the red clay formed in the early stage of the Quaternary period, it was often exposed to the impact of interglacial hot and humid climates and flowing water, while in the later stage of the period, the red clay was subjected more to aeolian deposition, and maintains its aeolian characteristics though it has experienced strong in situ weathering during the post-depositional processes.

Abstract:In order to understand where North China paleo-latosol-like soils should be placed in Chinese Soil Taxonomy, study was carried out on soil properties and taxonomy of the Quaternary paleo-latosol-like soils in Chaoyang area of Liaoning Province. The soils were classified based on diagnostic horizons and diagnostic characteristics of the soils analyzed either by following the principle and methodology of the “Keys to the Chinese Soil Taxonomy (3rd edition)” with the soils deemed as parent material, or by proceeding from the soil genetic characteristics of the soils. Results show that the current version of the Keys to Chinese Soil Taxonomy (3rd edition) is unable to provide the paleo-latosol-like soils, a niche in the system. To solve the problem, the foremost task is to establish criteria for diagnosis of paleosols.

Abstract:With the land use status of Dongpo in 1996 and in 2005 cited as basic data, three land use planning targets were predicted for the Dongpo District, based on Cellular Automata Modeling, and three planning schemes were put forth correspondingly. Under the precondition of sufficient data mining, and by following the transformation rule of transferring numerous elements simultaneously into CA-Markov, changes in amount and space of land use in Dongpo District in 2014 were simulated separately according to the three different planning schemes. Results show that of the three planning schemes, the one oriented towards protection of basic farmland and “Grain for Green”, and consideration of both land consolidation and city development was the most ideal. Changes of land use in amount and space in 2014 predicted according to the most ideal planning scheme were analyzed and compared with the status of land use in 2005 and corresponding policies and measures were put forward.

Abstract:Aiming at the restraints in exploiting and utilizing the soil resource of tidal flat in the coastal region of North Jiangsu Province，the theory of ecological risk was introduced into soil salinization risk assessment of the agroecosystem of this area; methodology and procedure of ecological risk analysis was discussed; and an index system for soil salinization risk assessment was established and risk assessment models were constructed.Then the soil salinization risk of the region was quantitatively assessed and graded.Results show that the integrated risk value of the region ranged from 0.26 to 0.91 with an average of 0.53，indicating its soil salinization risk was generally high and varied significantly from place to place in the study area.The spatial pattern of the soil salinization risk was similar to that of soil salinity and groundwater mineralization.As affected by the farming system and field practices，the salinization risk was generally higher in the rice growing eastern part than the cotton-growing western part of the study zone.The area very high，high，medium，and low in risk accounted for 5.01%，63.54%，30.53%，and 0.92%，respectively，of the total study area.The two grades of high risk and medium risk were the largest in area and hence are the critical area for soil amelioration.The findings may be cited as reference for amelioration of moderate-and-low-yield farmlands and for scientific management of problem soils in the coastal region.

Abstract:Not many reports are available on researches on chemical fractions of heavy metals based on soil types.In this project，seven soil profiles，representing the seven sub-classes of soils typical of Hong Kong，were collected for analysis of chemical fractions of heavy metals (Cd，Cu，Pb and Zn) in these types of soils and their potential environmental risks，using three-step sequential extraction procedure laid down by the EC Reference Bureau (BCR).Potential environmental risk of the heavy metals in the soils was also addressed based on the relative contents of chemical fractions.Results indicate that besides some residual forms a substantial proportion of HOAc-soluble Cd，Pb and Zn was observed in the soils and varied with soil types.Copper fractions were dominated by residual and reducible phases (bound to organic matter and sulfide) in all the seven types of soils.Heavy metals in Orthic Gleysols and Udic Luvisols posed relatively higher potential risks to the biota and environment than in the others.Of the four metals lead was the highest in potential environmental risk.

Abstract:An experiment using the rhizo-bag system and the sequential extraction method was conducted to investigate translocation and transformation of arsenic during the whole rice growing period and analyze As fractions in a soil-rice system，where the soil was moderately-slightly contaminated with arsenic.Results show that the concentrations of total arsenic as well as amorphous and poorly-crystalline hydrous arsenic oxides in the rhizosphere (R) were significantly higher than those in the nonrhizospheric soil (NR) during the third and fourth growth periods，while the concentration of residual arsenic，the lowest in availability，were lower in the rhizosphere (R) than in the nonrhizospheric soil (NR).The iron plaques over the surface of roots were dominantly formed of well-crystallized hydrous oxides of Fe and Al and amorphous and poorly-crystalline hydrous oxides of Fe and Al (＞90%).Moreover，during the fast growing period，the iron plaques aged the most and their arsenic adsorption capability decreased by 60% and by 10% as compared that in the first and second growing periods，respectively，however，it did not vary completely with the change in quantity of the iron plaques，but was closely related to fractions of Fe in the iron plaques.The behaviors of arsenic in the soil-rhizosphere-rice(YY-1) system could be concluded as follows：arsenic transported from bulk soil to rhizosphere with iron oxides reducing in soil and accumulated in the oxidizing rhizosphere.Iron plaques increased arsenic uptake by roots during the early growth periods，while it functioned as buffer in arsenic uptake for decreasing concentrations of arsenic in rice roots during the last three growth periods.

Abstract:Relationship between soil phosphorus (P) accumulation and characteristics of P adsorption in red soil under long-term (20 years) fertilization were explored，and environmental risk of P accumulation P in the soil was discussed through analyzing changes in P adsorption eigenvalue and environment oriented soil P token value.Results show that longterm P fertilization markedly increased P accumulation and the contents of available P and readily desorbable P in the soil，but decreased the soil adsorption capacity of foreign P.In all the seven treatments in the experiment，except Treatment NK and Treatment PSI (peanut stem incorporation)，the amounts of Olsen-P in the soil were all over 20 mg kg^-1，reaching a P level of abundance，but only in Treatment PM (pig manure) did P accumulation pose some environmental risk.Consequently a new fertilization system should be worked out by taking into account both the agricultural effects and environment safety of soil P，to further rationalize the use of P resources.

Abstract:A field experiment was carried out to study effects of waste-CaCO₃ on growth and heavy metals (Cd，Pb，Zn，Cu) concentration of a low-accumulating cultivar of Zea mays in a soil contaminated by waste water from a lead/zinc mining，and changes in soil pH and available heavy metals content as affected by application of waste-CaCO₃. Results show that waste-CaCO₃ increased yield of the plant significantly.The effect was the most significant in treatments of high waste-CaCO₃ application rate，where the first crop increased its yield by 154% and the second by 275% as compared with the control，and lowered their uptake of heavy metals (Cd，Pb，Zn，Cu).As a result，their concentrations in the grains were below the criteria of the Natural Food Hygiene Standard. waste-CaCO₃，regardless of its application rate，increased soil pH and reduced the concentration of available heavy metals in the soil to a varying extent，and inhibited translocation of Cd and Cu from stem to grains of the plant，resulting in lower heavy metal concentration in the grains of Z.mays.

Abstract:Ion diffusion is an important path of mass transport in nature，controlling movement of nutrients from bulk soil to plant roots as well as fate of potentially harmful salts and toxic compounds.The kinetic method was used in this experiment to determine surface charge properties of soil colloids of neutral purplish soil and latosol and to study K⁺，Mg²⁺ diffusion in the two types of colloids under the same condition as surface charge properties were determined.And the diffusion flux dependent of time and diffusion coefficient in the two types of colloids (at different of pH electrolyte type and electrolyte concentration) were determined. Results show 1) the total diffusion flux varied in the range of 2.6 ~3.1 mg g^-1 in neutral purple soil under different environmental conditions，about 6~10 times higher than what in latosol，being in the range of 0.26 ~0.51 mg g^-1; and 2) the diffusion coefficient varied in the range of 1.17×10^-9~1.91×10^-9 cm² s^-1 in neutral purple soil under different environmental conditions，and in the range of 0.23×10^-9~0.45×10^-9 cm² s^-1 in latosol. Surface charge properties were the dominant factor affecting ion diffusion in charged colloids.

Abstract:A pot experiment was conducted, using winter wheat (Triticum aestivum L.cv Yangmai 6) growing in a clay loam and a clay, to investigate fate of fertilizer nitrogen (N) in soil N pools and plant parts after combined application of inorganic and organic fertilizers, i.e. ammonium sulphate and rabbit feces.The experiment was designed to have five treatments, namely Treatment IF (inorganic fertilizer N), Treatment OF (organic fertilizer N), Treatment IOF1 (combined application of inorganic fertilizer and organic N fertilizer labelled with ¹⁵N), Treatment IOF2 (combined application of organic fertilizer and inorganic N fertilizer labelled with ¹⁵N) and Treatment CK (no fertilizer N). Results show 1) the highest winter wheat grain yields were obtained in Treatments IF and IOF, and no significant difference was found between them both in clay loam and clay; 2) Treatment IOF increased plant uptake of organic-fertilizer-sourced ¹⁵N, by 57.1% and 133.3%, in grain and by 220% and 100% in whole plant in clay loam and clay, respectively, but decreased its uptake of inorganic-fertilizer-sourced ¹⁵N with them decreased by 31% and 17% in grain and by 27% and 15% in plant, in the two soils, respectively, suggesting that in Treatment IOF, inorganic fertilizer N increased the uptake of organic fertilizer ¹⁵N whereas organic N fertilizer decreased the uptake of inorganic fertilizer ¹⁵N; 3) compared with Treatment IF or OF, in clay loam Treatment IOF increased accumulation of inorganic and organic fertilizer ¹⁵N in vegetative organs of the plant growing, while in clay, it increased accumulation of inorganic fertilizer ¹⁵N in vegetative organs and organic fertilizer ¹⁵N in grains; and 4) compared with Treatment IF or OF, Treatment IOF at the maturity stage of wheat significantly increased fertilizer ¹⁵N recovery rate of the soil plant system and the two portions of fertilizers stimulated each other sequestration of ¹⁵N of the other in the soil microbial biomass N(MBN) pool, and correspondingly, N loss rate (NLR) of both organic and inorganic fertilizer ¹⁵N decreased significantly. It is quite obvious that compared with Treatment IF, the traditional fertilization method, Treatment IOF obtained similar grain yield, but increased fertilizer N recovery rate of the soil plant system.

Abstract:Root-phosphorus-uptake (RPU) is a very important parameter for farmland fertilizer management and non-point source pollution control. Since it is almost impossible to determine RPU rate distribution in soil profile directly, it is often estimated using an inverse method, which, however, is influenced by factors, such as the spatial interval (SI) of soil soluble phosphorus (P) concentration measurements, the time interval (T) between the two successive measurements, and the measurement errors (ε_pa) of soil soluble P concentration, etc. In this study, several numerical simulation experiments were first conducted to explore effect of SI, T andε_pa on accuracy and stability of the method. Results show that the overall relative error between the estimated and the theoretical average root-phosphorus-uptake rate distributions was less than 10% when (a) SI was set as 5 cm within the 0~30 cm soil layer and 10~20 cm in soil layers beyond 30 cm in depth; (b) T was set between 5 d and 20 d; and (c) ε_pa was controlled no more than 15%. On such a basis, the inverse method was applied to estimating average root-phosphorus-uptake rate distribution of winter wheat at the seedling stage in a soil column experiment. The estimated total P uptakes by winter wheat at various growth stages matched well with the measured values, with all the relative errors ranging within 10%.

Abstract:A field experiment is carried out to evaluate effects of non-tillage on distribution, content of organic carbon, and microbial carbolic metabolism of soil aggregates in a fluvo-aquic soil under a cropping system of corn-wheat rotation in the Fengqiu National Agro-Ecological Experiment Station, China. The>250 μm fraction of aggregates in the soil was significantly higher (p<0.05) under non-tillage than under conventional tillage, while the 250~50 μm fraction did not vary much between different tillage methods, and the contents of organic carbon in these two fractions were higher under no-tillage.The 50~2 μm fraction was significantly lower (p<0.05) under no-tillage than under conventional tillage, while the<2 μm fraction showed no much difference between tillage methods, and the organic carbon in these two fractions did not either.The increase in the 250~50 μm fraction and the resultant decrease in the 50~2 μm fraction made the former ranking first in contribution to the total organic carbon in the soil.BIOLOG analysis indicates that the two treatments, non-tillage and conventional tillage, differed significantly in carbolic metabolism of soil microbial communities in various particle size fractions, with the former being obviously lower than the latter in the 250~50 μm and<2 μm fractions.All demonstrate that non-tillage favors congregation of small particles into macroaggregates and increases the content of organic carbon in the>50 μm fraction, while microbial carbolic metabolism in the 250~50 μm fraction weakens thus leading to higher stability of organic carbon in the soil.

Abstract:Various particle-size fractions of soil aggregates were obtained with the wet-screening method from the soil of a long-term stationary fertilization experiment (since 1984) field of the Changwu State Key Loess Plateau Agro-Ecological Experimental Station of the Chinese Academy of Sciences, Northwest China, for analysis of effect of long term fertilization on soil organic carbon distribution in water-stable aggregates of different particle-size fractions. The experiment had five N treatments (N₀、N₄₅、N₉₀、N₁₃₅、N₁₈₀), which were all the same in P application rate, and four fertilization treatments, that is, CK (unfertilized), NP (nitrogen and phosphorus), M (farmyard manure), and NPM (nitrogen and phosphorus plus farmyard manure). Results show that long-term fertilization significantly affected water-stable aggregates distribution (p<0.05), increasing the content of macro aggregates (>2 mm) and decreasing that of micro aggregates (<0.25 mm). Nitrogen fertilization significantly increased soil organic carbon (SOC) content in the 0.5~0.25 mm and>5mm water-stable aggregates by 44.3%~73.3%, compared to that in Treatment N₀. Moreover, Treatments M and NPM increased SOC content in aggregates of all particle sizes by 40.7%~92.2% over CK, and in the >5 mm aggregates by 66.7% and 92.2%, respectively. Treatments N₀、N₄₅、N₉₀ and CK contributed the most to the soil organic carbon content in the 1~0.5 mm water-stable aggregates, accounting for 13.7%~23.7%. Treatments N₁₃₅、N₁₈₀, NP, M and NPM contributed the most to the SOC content in the>5 mm aggregates, accounting for 17.3%~24.9%. SOC was positively related to the content of the>5 mm and 5~2 mm water-stable aggregates, but negatively related to the content of the<0.25 mm water-stable aggregates.

Abstract:Significant difference of nitrification can be always found between rices different in cultivar, which may result in difference in nitrogen use efficiency between the two rice cultivars. A rhizobox with three compartments and subsequent soil-slicing was used to determine simultaneously variation of nitrification and ammonia oxidizing bacteria (AOB) in the rhizospheric soils of two rice cultivars, i.e. Shanyou 63 (Indica) and Wuyun 7 (Japonica), growing at an N level of 30 mg kg^-1 soil ^-1. Composition of AOB communities in the rhizosphere was studied by means of DGGE (denaturing gradient gel electrophoresis) of 16S rDNA of the AOB. Results show that nitrification activities of both rice cultivars increased with the incubation time. Peak nitrification activities were found in rhizospheric soil. In the rhizosphere nitrification activities decreased with the distance from the root. The maximum nitrification activity was measured to be at 0.77 mg kg ^-1 h^-1 and 0.73 mg kg ^-1 h ^-1, in Shanyou and Wuyun respectively. The populations of AOB in the root zone, rhizosphere (0～4 mm away from the root zone) and bulk soil (>4 mm away from the root zone) for both rice cultivars increased during the growth periods The composition of AOB communities in the rhizosphere of Shanyou 63 is more abundant than of Wuyuny 7, showing that Indica might have a stronger nitrification in rhizosphere and on root surface and hence have a higher capability of utilizing nitrate than Japonica.

Abstract:A long-term fertilization experiment was conducted to study community structure and diversity of soil collembola in fluvo-aquic soil in North China.The experiment was designed to have 7 treatments, i.e.combined application of N, P and K (NPK), combined application of N and K fertilizer (NK), combined application of N and P (NP), combined application of P and K (PK), application of organic manure (OM), combined application of organic manure and NPK (organic nitrogen∶fertilizer nitrogen=1∶1) (MNPK) and no-fertilizer treatment (CK).Results showed that the average collembola density of the seven treatments was 30 000 m^-2, and application of organic manure significantly increased the size of the soil collembola community, while soil phosphorus content is probably one of the limiting factors for abundance of soil collembola in this region.Soil collembola diversity was higher in Treatments OM and MNPK; and the highest similarity index was observed between Treatments OM and NPK, the runner-up between Treatments NPK and MNPK,and the lowest between CK and any other treatments. The experiment demonstrated high preference of collembola for soil environment. Most genera of collembola were positively related with OM application. Positive response was observed of Isotoma and Xenylla in Treatment MNPK, and somewhat of Hypogastrura and Sminthurinus in Treatment PK. Fertilization also affected vertical distribution of soil collembolan.In Treatments MNPK, NPK and OM they tended to reside in 0-10 cm soil layers , while in Treatment NK and CK they did in 10-20 cm soil layers.The quantitative indices of soil collembolan (such as number of individuals, number of orders and diversity), being very sensitive to fertilization, can be cited as an important indicator in soil quality evaluation.

Abstract:A soil incubation experiment was conducted to investigate effects of application of nitrogen (N), phosphorus (P) and potassium (K) fertilizers on availability of soil Cd. Results show that after 60 days of incubation, all the N fertilizer treatments lowered soil pH, and increased the amount of extractable Cd; among them urea of high rate and ammonium chloride displayed the most significant effects, and ammonium sulfate did the least in increasing extractable Cd. All the P fertilizer treatments caused modest reduction of soil pH, but in terms of their effect of increasing extractable Cd, only single superphosphate showed something significant. All the three K fertilizer treatments reduced soil pH; among them potassium chloride increased extractable Cd the most at D0, but the effect waned down after D15. At the end of the experiment, the contents of extractable Cd in all the K fertilizer treatments fell below that in CK. The findings further suggest that it is advisable to avoid application at a high rate of acidic fertilizers, such as urea (after its transformation), ammonium chloride and single superphosphate, and other acidic materials as well, to soils severely polluted with Cd or soils with Cd content close to the threshold value of pollution, and use di-ammonium phosphate and ammonium sulfate instead.

Abstract:Nitrate loss is an important route of nitrogen loss, and its mechanism in flat cropland has been documented. However, it is still unclear how nitrate loss takes place in sloping cropland. Long-term plot experiments on field runoff were performed to monitor nitrate loss with runoff process in a sloping cropland of purple soil. Results show that runoff affected the process of nitrate loss from the slope cropland. Nitrate content in runoff increased at the initial period of a rainfall event, and then declined, and in the subsurface flow, it increased steadily and leveled off gradually. The potential environmental risk of the nitrate in surface runoff from slopeland of purplish soil is extremely high. The average nitrate content in surface runoff and subsurface flows of several rainfall events was N 0.73±0.17 mg L^-1 and N 21.72±2.05 mg L^-1, respectively. In about 75% of the surface runoffs, nitrate content was above N 0.5 mg L^-1 and in about 85% of the subsurface flow above N 10 mg L^-1. It was calculated that that the annual nitrate loss with surface runoff from the slope cropland of purple soil was N 0.93±0.05 kg hm^-2, accounting for 0.62% of the fertilizer N applied in the current crop season, while with the sub-surface flow, it was N 33.51±2.73 kg hm^-2, accounting for 22.34%, suggesting that nitrate loss via subsurface flow is the main route of nitrate loss from the sloping cropland of purple soil, not only leading to eutrophication of surface waterbodies and pollution of groundwater, but also aggravating environmental pressure in the upper streams of the Changjiang River .

Abstract:Expression of microRNA399 (miR399) and P responsive genes was analyzed in white lupin under P stress by miRNA microarray and RT-PCR, respectively. Samples of root (proteoid root and lateral root), stem and leaf were harvested from white lupin plants, which were cultured in hydroponic nutrient solution with or without P for 21 days. Results show that P deficiency significantly increased root biomass of white luipn, but affected negatively shoot biomass and Pi content of the plant. The results of miRNA microarray indicated that 10 members of the miR399 family in root, 7 in stem and 3 in leaf, were up-regulated in the plants under P stress, on average by 4.4, 3.8 and 2.5 folds, respectively.LaATPase, LaPT1, LaMATE, LaPEPC3, LaSAPand LaMDH1 were the 6 P responsive genes, of which expression was much higher in the proteoid roots of the plants without P than in the lateral roots of the plants with P. Putative P responsive elements were found binding transcription factors, PHR1 or WRKY, in the promoter regions of LaPHT1 and LaMATE. Based on the findings, regulatory relationship of miR399 and PHR1 with P responsive genes were explored, suggesting that miR399 and P responsive genes play an important role in white lupin adapting to P deficiency.

Abstract:Characteristics of vegetation succession and diversity were studied through field surveys of lands during a process of natural restoration in a pasture zone in the loess hilly region, and soil samples were taken for analysis of dynamic changes in soil organic carbon, alkalytic-nitrogen, total nitrogen, available phosphorus, and activities of urease, invertase, alkaline phosphates and catalase, and correlations of plant diversity with soil nutrients and enzyme activity as well. Results show that during 75 years of natural restoration, community succession began with annual herbs such as the Asteraceae (Artemisia scoparia) and the Chenopodiaceous (Corispermum chinganicum), which were gradually succeeded by perennial herbs, and finally by Stipa grandis and S. bungeana, which were the dominant species typical of the pasture zone. On the whole, a rising trend was observed of the number of species and a wavy but rising trend of the species diversity index and of soil nutrient and enzyme activities as well with increasing of natural restoration years, soil nutrient and enzyme activities increased with an increase of natural restoration years too. After 75 years of natural restoration, Margalef index, Shannon-Wienner index and Pielous index increased by 83.3%, 31.8% and 21.4%, respectively；soil organic carbon, alkaline nitrogen, total nitrogen and available phosphorus by 185.0%, 164.6%, 152.9% and 109.8%, respectively; and soil urease activity, invertase activity, alkaline phosphates activity, and catalase activity by 64.0%, 7.8%, 51.1% and 11.8%, respectively. Significant positive correlations were observed of soil nutrient and enzyme activities with Margalef and Shannon-Wienner index, but an insignificant one was with Pielous index.

Abstract:Community structures of ammonia-oxidizing bacteria and ammonia-oxidizing archaea in a red paddy soil were studied with aid of the denaturing gradient gel electrophoresis and DNA sequencing technologies Results show that ammonia-oxidizing bacteria and ammonia-oxidizing archaea in red paddy soil were in abundance. Changes in community structures of ammonia-oxidizing archaea were more acute than of ammonia-oxidizing bacteria. With the former, changes were observed between all four stages, while with the latter, only some were between the early growth stages (seedling and tillering) and the late growth stages (booting and maturing) of rice. Shannon-wiener index of ammonia-oxidizing bacteria did not vary much during the entire rice growth season, while Shannon-Wiener index of ammonia-oxidizing archaea increased significant with the succession of the rice growth stages, and leveled off at the booting stage. Potential nitrification rate of the soil rose sharply during the early rice growth period, peaked at the booting stage and then declined somewhat. The potential nitrification rate appeared to be in significantly positive correlation with the Shannon-wiener index of ammonia-oxidizing archaea, but not with that of ammonia-oxidizing bacteria. The findings demonstrated that the effects of ammonia-oxidizing archaea on nitrification of red paddy soil are more pronounced than ammonia-oxidizing bacteria, and both of them, especially archaea, play an important role in the composition of paddy soil microbes and the function of the ecosystem of red paddy soil.

Abstract:Functions of arbuscular mycorrhizal fungi （AMF） in intensified farming systems have been attracting more and more attention.In the past decade，a big headway has been made in recognition of the significance of shifting from simulation in the greenhouse and laboratory to in-situ field study in the research on interactions of AMF and plants. Analysis of findings of related theoretical and applied/basic researches has led to such a conclusion that mycorrhizal biotechnology should include not only technologies for production and application of common AMF inoculums，but also techniques for regulating amount and infectivity of indigenous AMF propagules.Agricultural practices，such as rotation，intercropping，reduced or non-tillage，and application of rhizosphere signaling substances could effectively bring indigenous AMF into play.To better understand how spatial and temporal variation of indigenous AMF communities is related to their ecological functions will probably be the hot spot for future studies in this aspect.Besides，to screen and cultivate high-yielding crop cultivars or varieties that are highly responsive to AMF in fertile soils is thought to be an effective approach to enhance the use efficiency of soil nutrient resources.

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