Abstract:Characteristics of iron oxides in soils with a chronosequence developed from basalt have been studied in Northern Hainan Island.The results show that pedogenic free iron oxides(DCB-Fe) and Fed/Fe,(ratio of DCB-Fe to total Fe) increase and Feo/Fed(ratio of active Fe to DCB-Fe) decrease with increase in soil-forming age.The ratio of pedogenic hematite to iron oxides reaches from 16 % 25% to 48% in soil clays at soil-forming age of 9×10⁴a,64×10⁴a to 181×10⁴a determined by Mössbauer Spectroscopy.Furthermore the younger the soil-forming age,the poorer the crystallinity of goethite in soils.Also,X-ray diffraction studies indicate that the hematite contents in fine-earth fraction and clay fraction rise with increase in soil-forming age and that magnetite descends while maghemite ascends in content.

Abstract:This paper concludes that the formation of loess is in fact a result of soil-forming.Loess in the different regions such as steppe,desert steppe and forest steppe regions,may develop into Isohumisols,Aridisols,Cambisols,etc.But compared with reddish paleosols,it was formed in dry and cold conditions,so,loess even could serve as an indicator of dry and cold climate.The evolution of loess occured with change in the post-weathering,post-soil-formation and post-lithfication after aeolian deposit.

Abstract:The characteristics of clay minerals in the soils derived from different parent materials in Hainan Island and their application in Chinese Soil Taxonomic,Classification are discussed in this paper.The results are as follows.In general,there are much kaolinite in the clay fraction of all soil samples,but the highest content and the worst crystaillinity of kaolinnite are present in the soils derived from basalt.The contents of hydromica are so much in the soils derived from schist or purple sandstone that they are as high as 40%-50% of the clay fraction.And the content of hydromica in the soil derived from limestone is also as much as 20%-37% of the clay fraction.Moreover,the hydromica belong to hydromuscovite with dioctahedral structure.The ratio of the content of goethite and that of hematite is (3-4):1 in the clay fraction of the soils of "udic" suborder derived from basalt and granite.13ut there is only goethite without hematite in the clay fraction of the soils of "perudic" suborder derived from granite on the mountain.This result proves that the types of iron oxide in soil response to the soil moisture conditions,which can be used as an index to distinguish the "udic" and "perudir" soil moisture regime in the Chinese Soil Taxonomic Classification.

Abstract:Transport capacity of flowing water in a rill is one of the important parameters in soil erosion,especially in soil erosion prediction and soil erosion process modeling.Considering the fact that,under steady flow,sediment load increases with slope length and will finally approach the transport capacity,a laboratory flume experimental method with variable slope length is advanced for transport capacity determination. And a mathematical expression is suggested to estimate transport capacity with thus obtained experimental data.A series of 405 flume experiments were conducted with sand-clay(loess) soil.Transport capacity is related to slope and inflow rate,based on the experimental data under five slopes (5°,10°,15°,20°,25°),and three flow rates(2,4,8Lmin^-1).

Abstract:Information high way based on INTERNET is the foundation for sharing of soil information data sharing.It avoids unnecessary repetition of investment and construction,and brings soil information into full play for economic construction,agricultural development,environment protection and rational use of natural resources.To reach the targets of dynamic,static and remote distributed inquiry of soil map and attribute data,a client/server distributed network inquiry model and the techniques of Web GIS,ASP and FrontPage have been used and developed for this research.The study of this paper provides theory and methodology for further standardization and sharing of soil information data in China.

Abstract:Numerous studies have shown that soil particle size distribution (PSD),mass distribution,surface distribution and pore size distribution are fractals,which are generally described with fractal geometry.In this paper,the fractal properties of ten types of soils from loamy sand to clay were investigated with the method developed by Tyler and Wheatcraft (1992) un the basis of accumulative mass distribution of soil particles.Sieving data sets of the above mentioned ten soils were used to calculate fractal dimension which ranged from 2.489 to 2.896,and relationship between frac;tal dimension of PSD and soil texture was analyzed.Meanwhile the fractal dimension of PSD was compared with the fitted fractal dimension calculated from the calibration of the power-law expression of the corresponding soil water retention function developed with Monger sponge,and the mathematical relationship between them was therefore established.Results indicated that the fractal dimension of PSD increased with clay content but decreased with sand content, and the fractal dimension of PSD was approximately the same as and in linear relationship with the fractal dimension of the power-law expression for the soil water retention function.This implies that the soil water retention properties can be predicted by the power-law function in combination with the mass based fractal dimension of PSD.

Abstract:Soil water retention curve refers to the relationship between volumetric water content and pressure head,which plays a very important role in solving the problems of water flow and solute transport in soil. Due to its complexity,it is difficult to derive an accurate equation theory erically However,quite a number of experience formulas have ever been proposed on the basis of a number of experiments,such as Brookscorey(1964) model,Gardner(1970) model,van Grnuchten(1980) model,and Gardner-Russo(1988) model etc.,in which many parameters need to be determined.In this paper,by means of the least square method,the nonlinear equation groups that are used to obtain the parameters in models above mentioned, are derived respectively,and their Picard iterative forms are got.At last,the suitability of the four models for different tvpes of soil is indicated by the numerical examples.

Abstract:When water flows through the vadose zone,there is not only water inflow but also air inflow.In this study,a one-dimension infltration and two-dimension infiltration experimental apparatus was designed and built up.We got the two-phase flow field by driving the airflow with water infiltration and recorded and monitored the water accumulative infiltration volume,wetting front and the air pressure within the twophase flow field to study the two-phase flow.One-dimension and two-dimension two-phase flow experiments were conducted to determine effect of air compression on the infiltration of water under different air outflow rates,the change in air pressure and the air movement.The pressure sensors connected with the automatic pressure monitor system were used to monitor and record the change in air pressure in 1-D and 2-D soil column.The micro gas flowmeter with valves was connected with the soil column at its bottom to control and regulate the air outflow rate.In 1-D experiment,we found that without controlling the air outflow the water inflow rate was reduced compared with the water inflow rate under the condition,as observed by other researchers.When the air outflow rate varied,the water inflow rate changed accordingly,but always remained bigger than the former.In 2-D experiment,it is found that the water inflow-rate in vertical direction was bigger than that in horizontal direction.Finally,we got air pressure contour figures at different times.From these figures,it is discovered that the airflow was most vehement along the line between the water trench and the air vent in the bottom of the soil box.

Abstract:The Jingtai Irrigation Zone with an acreage of 200km² is located alongside the upper reaches of the Yellow River,in Gansu Province,Northwest China.Under the control of arid and semiarid climate,besides the influence of strong evaporation it is subject to strong effects of seasonally freezing and thawing processes as well.The uneven distribution of salt and water makes the freezing point of soil different from one depth layer to another.It is found based on the field investigation that the frozen period of salinized soil was shorter and the maximum frozen depth shallower.The starting position of soil freezing is from a certain depth below the soil surface other than from the soil Surface.The freezing characteristic makes the salt-water-heat dynamic more complex due to two freezing fronts occurring during freezing.

Abstract:Soil hydraulic properties can be estimated from soil basic properties such as soil texture,bulk density and soil organic matter,which can be obtained easily.These estimating functions are called as Pedo-Transfer Functions(PTFs).Based on the summary of relevant study on PTFs,data collected from Huabei Region was analyzed in this paper.Some PTFs have been established and verified.It was found that the PTFs were useful in the estimation of soil hydraulic parameters in a regional scale.

Abstract:Pot culture experiment was conducted to study salt resistance and mechanisms of five wheat varieties.The mechanisms of salt resistance were set forth by means of determining and analyzing the water retention indexes such as wax content of leaf(WC),succulence index (SI) and relative water content of leaf (RWC),and membrane stability indexes such as electrolyte leakage value of leaf (ELV) and relative electrolyte leakage percentage of leaf(RELP).The results obtained showed that the salt-resistant wheat varieties were of relatively higher wax content,succulence index and relative water content while grown under saline condition,so they performed stronger ability to retent water and fight against salt injury.The strong ability of salt resistance of "Lumai No.19" and "Zhishen No.2" was relevant to their higher wax content in leaf,succulence index and relative water content.The situation was contrary for "Lumai No.23 ".The strong ability of salt resistance was also relevant to the higher stability of membrane tissue.Salt-resistant wheat varieties "Lumai No.19" and "Zhishen No.2" were of lower electrolyte leakage value of leaf and relative electrolyte leakage percentage and higher stability of membrane.

Abstract:Characteristics of NH₄⁺ transport during water infiltration and redistribution have been studied with the soil column destruction method.The solute distribution curve in the soil profile (depth vs. amount of solute retained in per gram dry soil) was of slope at the beginning of infiltration,and its upper part gradually became vertical to the abscissa while infiltration continued.Compared with water in infiltration and redistribution,solute was significantly delayed.The ratio of water wetting front depth to solute front depth,indicating the delay of solute infiltration,increased with the process of infiltration.With increasing concentration of displacement solution,the solute retardation factor during infiltration decreased and the velocity constant of soil NH₄⁺ retention reaction increased,accordingly,the apparent Gibbsfree energy decreased.Solute redistributed while water was redistrbuting. The solute amount retained in per gram dry soil at the iso-concentration point of solute redistribulion,which was the cross point of solute distribution curves of different times,was not changed during solute redistribution.In the upper part of the soil column above the iso-concentration point,the solute amount retained in per gram dry soil decreased,contrarily that in the lower column part increased due to solute redistribution.The depth of the iso-concentration point increased with increasink concentration of the displacement solution.

Abstract:In modeling the processes of soil CaCO₃ eluviation and deposition,the Ca²⁺ concentration and the pH value in soil solution must be calculated based on the principles of the soil chemical thermodynamic equilibrium.But it is difficult to calculate them directly,for some parameters(e.g.ionic activity coefficients in soil solutions) are hardly available,which leads to unrealizability of computer simulation of the process.Focused on this problem,this paper presents an algorithm of successive approximation.With known CO₂ partial pressures in soil air and soil temperatures,the algorithm enables computation of Ca²⁺ concentrations and pH values in soil solutions at arid area,which provides a significant supporting technology for computer to simulate the process of soil CaCO₃ eluviation and deposition.This method has been applied and verified in CAEDP model (A model for CaCO₃ eluviation and deposition process in arid area soils).The results show that the method is solidly grounded in theory with results accurate and stable,and process simple and easy to follow.

Abstract:Effect of waterlogged conditions on phosphorus sorption and release of 18 soils with contrasting chemical and physical properties was studied in a laboratory experiment.The soils both in aerobic and anaerobic conditions were analyzed for pH,redox potential(Eh),oxalate Fe and the amount of P released measured by means of successively removing soil phosphate using iron oxide-impregnated paper strips.Phosphate sorption isotherms were determined with the standard batch technique for air dried and waterlogged soils.It was shown that after being reduced for 30 days the P sorption capacity,maxim buffering capacity and standard P requirement of most of the soils studied increased while P release from all soils decreased.Our data suggest that the increase in soil oxalate Fe aftrr waterlogging was the main reason responsible for the changes in P sorption and release of the soils studied.

Abstract:Soil structural stability,as measured by water-stable aggregate rate(WSAR,the rate of >0.25 mm water-stable aggregate's weight in 1-5 mm dry aggregate's weight) and clay dispersion rate,and Atterberg limits(ALS) were assessed with relation to salinity,sodicity and organic matter on salt-affected soil samples taken from Jingdian Irrigation Area,Gansu.The obtained results showed that soluble salts were dominated by sodium ion.As a result,soils were sodic.With increase in salinity and sodicity,aggregate stability decreased and clay dispersion increased significantly,meanwhile,there was a declining trend in ALS.This clearly implied that salinization as well as increase in sodicity was one of the factors which are responsible for soil structural degradation.With increase in organic matter(OM),aggregate stability and ALS increased and clay dispersion decreased markedly,which showed that addition in organic matter to salt-affected soils can improve structural characteristics.On the effects of OM and ESP on aggregate stability,WSAR could be predicted according to the following equation:
WSAR=19.4+0.98OM-1.43ESP(R²=0.5741,n=67)
Aggregate stability,clay dispersion,liquid limit and plastic limit significantly correlated.This illustraced that liquid limit and plastic limit could be used to characterize the structure of salt-affected soils.

Abstract:The study on exchange-adsorption of aluminium and manganoustions in red soils was carried out.The results were shown:Ion exchange power (or ion adsorbability) sequence was Al³⁺>Mn²⁺>Ca²⁺>K and the amount of adsorbedtion and displacedtion increased with the amount of added ion,which acted according to the universal rules of ion exchange;Nonelectrostatic adsorption of hydrolysis products overlapping electrostatic adsorption was probably responsible for the nonequivalence of ion exchange reaction in which aluminum and manganous ions participated,it was extremely in laterite systems due to its more content of iorn oxide;The realationship between amount of nonelectrostatic adsorption and concentration of equilibrium solution conformed to the the Freundlish equation.

Abstract:Hydroponic culture and H¹⁴CO₃^- isotopic tracing were conducted to study on the distribution and transfer of HCO₃^- assimilates in Zn-inefficient cultivar IR26 and Zn-efficient cultivar IR8192-31-2 in relation to rice cultivar adaptation to Zn deficiency.The results showed that IR26 accumulated more HCO₃^- assimilates in the roots than IR8192-31-2.whereae,the latter is faster in root-to-shoot transfer of HCO₃^- assimilates.Zn application enhanced transfer of HCO₃^- assimilates from roots to shoots of Zn-inefficient rice.¹⁴C-activities were higher in all Zones of excised roots of IR26 roots than in that of IR8192-31-2,which implied that IR26 roots absorbed more H¹⁴CO₃^- than IR8192-31-2 roots.Moreover,transfer rate of H¹⁴CO₃^- assimilates from root tip to enlogation zone was higher for IR26 than for IR8192-31-2.It could he concluded that the difference in distribution and transfer of HCO₃^- assimilates were major mecha nisms responsible for Zn efficiency in lowland rice.

Abstract:The degradative characteristics of butachlor in the root-zone soils of different crops such as wheat, cotton,rice,maize and the bulk soils,and microbial population dynamics of culturable microorganisma capable of utilizing butachlor were investigated.A larger microbial population was measured in these crop rhizosphere soils compared to the non-rhizosphere soils.The increased population enhanced biodegradation of butachlor in the rhizosphere soils as compared to that in the non-rhizosphere soils.The degradative rates of butachlor in the wheat-,cotton-,rice-,or maize-rhizospheres were 1.63-2.34 times of those in nonrhizospheres,and the corresponding half-lives were shorten to be 42.2%-72.8% of those in the nonrhizoshere.The enhancemerrt in biodegradation was further strengthened by the inoculation of a bacterial strain mixture capable of utilizing butachlor as sole carbon and energy sources.Compared with those in the non-rhizosphere,the degradative rates in the rhizospheres increased up to 1.68-2.83 times after the inoculation.The microcosm in crop root-zone soil may be the optimal site for rapid degradation of residual pesticidesbutacholr.

Abstract:Biolog method was applied to studies on microbial community and functional diversity in soils in and around Aberdeen City.Results show that compared with rural soils an obvious changes in microbial tommunities and functional diversities can be observed in urban soils under the press of heavy metal accumulation in the orbit environment.Microbial consumption of carbon sources in urban soils is much more and faster than that in rural soils.And their major carbon sources have shifted from sugar,ammo acid in the rural soil to phenolic acid in the urban soil.Further more,canonical variate loadings in different incubation time point give the obvious discrimination of cluster distribution between urban and rural soils.

Abstract:Under various soils,groundwater levels and soil temperature during days of growth of upland rice root system were studied by three-dimensional coordinate container method stages,the growth.The results were as follows:1.Under various soil conditions,the depth of root system distribution was generally about 0.60 m.2.Regardless of soil types root volume,total area and active area of root surface,root length,dry weight of roots and root density decreased gradually with soil vertical depth,but active/total area of root surface fluctuated lightly.Giving overall consideration to all root parameters,the growth of upland rice root system was the best in red clay soil,the next was in sandy fluvo-aquic soil,the worst was in paddy soil.3.Under various groundwater levels,root length,root dry weight,and the distribution of every soil layer were the treatment A(6 car water layer)>B(4 cm water layer)>C(2 cm water layer),root volume and root density decreased gradually with root system vertical distributiou depth,but the treatment of A increased strongly between 0.30 m and 0.50 m.Total area and active area of root surface of A and B increased or decreased with root system vertical distribution depth,total area of root surface,active area of root surface of C decreased with root system vertical distribution depth,and active area/total area of root surface of A,B,C increased with root system vertical distribution depth.4.Under various soil temperature,root length,root dry weight and root volume,root density,total area and active area of root aurface decreased gradually with root system vertical distribution depth,the increase of soil temperature and the decrease of the accumulation of temperature during days of growth stages.The distribution of every layer/total quantity of root volume was not different between the treatment of b(date of sowing:8th,May) and c(date of sowing:8th,June),but was evident difference between b (date of sowing:8th,May),c(date of sowing:8th,June) and a(date of sowing:8th,April);the distribution of every layer/total quantity of root dry weight was not different between the treatment of a and b, but was different evidently between a,b and c;the distribution of every layer/total quantity of root length was not different between a,b and c; active area/total area of root surface of a,b,c increased with root system vertical distribution depth,the increase of soil temperature,the decrease of the accumulated soil temperature during days of growth stages.The ratio of active area to total area of root surface is in order of the treatment a

Abstract:杉木是我国南方的主要造林树种,但杉木连栽会引起林地生产力下降和生态环境恶化.营造杉木混交林是防止地力衰退的有效途径之一^[1～2].许多学者对杉木的混交林进行了专项研究^[3～4],但研究杉木木荷混交林土壤性状的报道较少,本文重点介绍杉木木荷混交林25年生林分对土壤改良作用的影响.

Abstract:对于退化生态系统的恢复,首先是植被恢复,植被恢复是充分利用土壤-植物复合系统的功能改善局部环境,促进生物物种多样性的形成.植被恢复的生态效应不但影响林地本身,也影响周围的环境,进而对区域和全球的生态平衡有所贡献,因此,退化生态系统的恢复与重建具有重大的生态效益、经济效益和社会效益.