Abstract:In this paper, the authors summarized progresses in the study on variable charge soil chemistry in recent years with emphasis on special chemical phenomena, such as salt adsorption, the effect of Fe/Al oxides inhibiting natural acidification of the soil and the effect of ionic strength affecting specific adsorption of ions and their microscopic mechanisms in the soil. The phenomena of salt adsorption and iron and aluminum oxides inhibiting natural acidification of the soil can be explained with the principle of overlapping of diffuse layers on the surfaces of oppositely charged particles which led to decrease in effective surface charge in the soils. The authors also elucidated the mechanism of ionic strength affecting specific adsorption of anions and heavy metal cations by variable charge soils and explained the effect with a four-layer adsorption model, and further verified on the basis of the variation of zeta potential of the colloids with ionic strength that electrostatic potential in specific adsorption planes of colloids decreases in absolute value with rising ionic strength, which is the main cause for the increase in specific adsorption of anions and heavy metals by the soils and Fe/Al oxides. The extensive investigation of the interactions between the electric double layers on oppositely charged particles and the structure of electric double layer not only helps elucidation of some of the special chemical phenomena in variable charge soils, but also enriches theories of variable charge soil chemistry.

Abstract:Apparent recovery efficiency (ARE) of applied fertilizers has been commonly calculated as fertilizer use efficiency in China and reported low in a number of literatures. In this paper, a new method is proposed to calculate real nutrient use efficiency (RNUE), which refers to ratio of the nutrients absorbed by plants to the nutrients depleted from the soil. The depleted nutrients may come from the nutrients originally in the soil or from the applied fertilizer. The equation for RNUE calculation could be shown as: Nutrients absorbed by plants / (nutrients from fertilization – negative balance of the soil nutrient pool). RNUE could also be calculated as the difference between 100% and nutrients loss rate. The nutrients not used by plants but depleted from the topsoil are considered lost, while the nutrients remaining in the topsoil are not. Since both the nutrients remaining in soil nutrient pool and the nutrients used by plants come mainly from fertilization, the RNUE can be suggested as the real fertilizer use efficiency (RFUE). Based on the proposed method, the RFUE will be much higher than the ARE reported in China. The loss rate of fertilizer could also be calculated if RFUE is known since their sum is 100%. Thus calculation of RFUE could help us understand real contribution and real loss of the fertilizer in agriculture production and work out proper fertilization strategies, as well, in light of fertilizer loss rate and soil nutrient holding capacity. A proper right fertilization technique should aim to reduce loss rate of the fertilizer, instead of achieving high ARE since the meaning of high ARE is not so clear even though it has been widely used in China. Fertilizer recommendation for main field crops will not depend so much on soil testing, but rather on the knowledge of the consumption and loss rate of nutrients of the soil-crop systems in future.

Abstract:Though peatlands comprise approximately only 2%~3% of the global terrestrial area and about 40%~70% of all the wetlands of the world, their carbon storage reaches as high as 3.0×10¹⁷~6.0×10¹⁷ g, accounting for 14%~40% of the global soil organic carbon pool (1.5×10¹⁸~2.344×10¹⁸ g). In the past, studies on carbon storage in peatlands focused mainly on carbon pool in the soil, especially in regions high in latitude, and few comprehensive reports were available on carbon pools in vegetation and litter layers. Here, a comprehensive analysis and review of the progress of the study on budgeting carbon storages in the soil, vegetation and litter layer carbon pools, the three major components of the carbon pool of the global peatlands. Now, it is still existing big uncertainties in budgeting carbon storage of the global peatlands. Inadequacy of information and data available from the countries or regions that have largest areas of peatlands, including biomasses of the vegetation and litters, carbon mass fraction, and thickness, bulk density and area of the peat layers, is a major one in budgeting. Then anthropogenic disturbance may further contribute to the uncertainty, thus making the budgeting more difficult. It is well known that China ranks first in Asia and fourth in the world in area of wetlands. However, in budgeting organic carbon storage in peatlands/wetlands, China differs quite sharply from others in the world, because the data and information are inadequate and varying sharply. Therefore, in order to improve precision of the budgeting peat wetland carbon storage and accuracy of the prediction of mechanism of the terrestrial ecosystem responding to climate change. It is, therefore, essential to intensify the study on carbon storage in peatlands.

Abstract:To study pedogenetic process and taxonomy of red clay in Beijing, six red clay profiles developed from granites and limestones were selected as samples for analysis of soil profile morphology, soil physical and chemical properties and soil mineral composition. Results show that argillan existed on the surface of soil ped of all the soil profiles, no lime reaction was observed throughout the profiles, and the soils were high in Fed/Fet and low in Feo/Fed. The red clay soil originated from limestones was finer in texture, higher in free iron, redder in color and higher in aggregation degree of the ped, while those from granites was lower in aggregation degree of the ped because of its higher content of sands of hard-to-weather quartz. During the pedogenetic processes of the soils, intensive argillation and ferruginization occurred presumably under hot and humid paleoclimate. However, with time elapsing, the red clays in the area have now become slightly alkaline or neutral in pH, dominated with Ca² in exchangeable base and high in base saturation, as a result of modern loess precipitation and consequent base complication. According to the principles and methods of Chinese Soil Taxonomy (3rd edition), the six red clay profiles should be sorted into four different subgroups of Argosols.

Abstract:It is vitally important to accurately estimate soil organic carbon (SOC) dynamics modeling uncertainty for successful decision-making in cropland management. In this study, a Beyesian inference using the Markov Chain Monte Carlo (MCMC) method was used to calibrate the parameters and estimate the output uncertainty interval for the Denitrification-Decomposition (DNDC) model in modeling SOC dynamics of the long-term monitored croplands with 22-year rice-wheat rotation history in Yixin County, Jiangsu Province of China. Results indicate that though there is some uncertainty, the DNDC model is suitable for modeling SOC dynamics of the long-term monitored croplands. In cases that input parameters are not certain in quality, Beyesian inference using the MCMC method could be an effective way for automatically calibrating input parameters and estimating uncertainty interval of the modeled SOC. The Beyesian inference using the MCMC method applied in this paper could also instruct the estimation of the SOC dynamics modeling uncertainty at region or country scale.

Abstract:An analytical approximation solution to the mathematic model for calculation of soil infiltrability with linear-source inflow is presented, based on the mass-balance principle that when the supplied flow rate is constant. A cumulative infiltration equivalent to the Lewis–Milne equation is produced by ignoring water ponding at the soil surface. Measurement of linear source infiltration was conducted in lab and soil infiltration process was worked out using the numerical algorithm and approximate analytical algorithm. The calculated results were compared with that measured with the double-ring method, and meanwhile based on the principle of mass balance, relative deviations of the calculation models were worked out through comparing the volume of water infiltration with the actual water supply. It was 7.21%~14.8% for numerical solution and 3.31%~12.4% for analytic solution. The significance of this research is that both soil infiltrability and temporal equation of cumulative infiltration can be obtained directly, thus providing an efficient tool for relevant researches on prediction of rainfall–runoff process, hydrologic models and designing and management of irrigation systems.

Abstract:Application of nano-materials to soil physics is a new breakthrough in the field, and its effects are significant in reducing soil water loss and improving soil water and fertilizer utilization efficiency and soil physical structure. A one-dimensional water infiltration experiment was carried out in disturbed loessal soil columns in laboratory for analysis of effects of content of nano-carbon (0 g g^-1, 0.001 g g^-1, 0.005 g g^-1, 0.007 g g^-1 and 0.01g g^-1) on soil water infiltration process and saturated hydraulic conductivity. Results show that (1) the influence of nano-carbon on water infiltration in the disturbed loessal soil was significant, and within a certain infiltration time period, cumulative infiltration and wetting front moving rate tended to decrease with the increasing content of nano-carbon; (2) Kostiakov formula and Philip equation could both be used to describe how cumulative water infiltration varied with time in the disturbed loessal soil treated with nano-carbon and the former fitted better; (3) variation of the wetting front with time demonstrated a power function relationship; and (4) nano-carbon also affected significantly saturated mass water content and saturated hydraulic conductivity in the disturbed loessal soil, and with the increasing content of nano-carbon, the former tended to increase,while the later decrease, which fitted well the binomial expression and exponential function, respectively. Key words Nano-carbon; Cumulative infiltration; Wetting front; Saturated mass water content; Saturated hydraulic conductivity

Abstract:Bioreduction processes will influence distribution of metals in anoxic soil environments. To investigate distribution and evolution of iron and manganese in form in soils under long-term (~74 d) anaerobic incubation, reducing soil systems were simulated by setting up different ratios of glucose/humic acid for the soils in the experiment. Results show that at the initial stage of the incubation, addition of glucose prompted reduction and release of iron and manganese ions, and at the same time increased the amounts of exchangeable and acid soluble iron and exchangeable manganese. However, addition of humic acid increased the amounts of oxidizable iron and manganese in the soils. With the incubation going on, the concentrations of metal ions and the amounts of most various extractable forms of iron/manganese were decreasing, suggesting that the iron and manganese in the soil were gradually transformed into mineral phases lower in extractability. Therefore, it is quite obvious that in anaerobic environment, the reduction, release, distribution and transformation of iron and manganese are significantly affected by variety and concentration of the organic substances in the soil, resulting in variability of the metal elements in mobility and bioavailability in the environment.

Abstract:Isothermal absorption, kinetic absorption and desorption process of antimony [Sb(V)] in red soil and calcareous soil typical to South China were studied. Commonly used adsorption kinetics equations were compared in fitting of dynamic adsorption curves. Sb(V) binding forms in the soils were analyzed using the sequential extraction method. Results show that the acid red soil was higher than the brown calcareous soil in both Sb(V) adsorption capacity (being 13.83 μmol g^-1 and 9.19 μmol g^-1, respectively) and Sb(V) adsorption rate (being 0.58 μmol g^-1 h^-1 and 0.38 μmol g^-1 h^-1, respectively); the Sb(V) adsorption on the surface of the red soil is a rapid and irreversible process; Antimony found in the two soils was mainly in Fe-Al oxides bound form and residue form; the content of specific or non-specific adsorption form of Sb(V) was quite low, which indicates that the adsorption of antimony in the soils is mainly irreversible. The comparison of the four adsoprtion kinetics equations in fitting of the experimental results shows that for red soil, high in Sb(V) concentration, the Elovich equation (R²=0.96) fitted the best and for red soil, low in Sb(V) concentration, the pseudo-second order kinetics equation did the best (R²=0.97、1.00), while for brown calcareous soil, regardless of Sb(V) concentration, the double constant equation (R²=0.96、0.94、0.93) fitted the best.

Abstract:In Cixi of Zhejiang Province, as a result of poldering in different time periods a long time scale succession of paddy soils and upland soils formed, which could be cited as good objects for the study of long term biogeochemical cycle of soil nitrogen. In order to explore effects of cropping history and pattern on soil organic nitrogen fractions, amino acid N, amino sugar N, NH₃ – N and hydrolyzable unknown N in the soils were analyzed with the Bremner method through hydrolysis in sealed tubes. Results show that the content of any fraction of organic nitrogen in the upland soil was only 50% ~ 60% of that of its counterpart in the paddy soil, suggesting that rice planting is more conducive to conservation and utilization of the soil organic nitrogen. On a long-time scale, all the organic nitrogen fractions, except amino acid N and amino sugar N, varied with the time exponentially, showing that organic nitrogen in the paddy soils was mainly on a rising trend, while that in the upland soils on a reverse one. In the soils of this area, amino acid N accounted for 23.5% ~ 29.3%, amino sugar N for 6.0% ~ 7.6%, NH₃ – N for 21.0% ~ 28.8%, and hydrolysable unknown N for 13.0% ~ 21.1% of the total nitrogen, indicating that cropping pattern and cropping duration neither has much effect on proportions of the major soil organic nitrogen fractions to the total nitrogen in the soils.

Abstract:A field experiment of controlled release fertilizers (CRFs) on cotton was carried out to study effects of application rate of CRFs on cotton (Guokang 12) growth and soil fertility with the application of common compound fertilizers (CCFs) as control for comparison. Results show that CRFs significantly increased plant height, culm diameter, leave area and the numbers of fruit spurs and bolls of the cotton. When N 75 kg hm^-2 and N 150 kg hm^-2 was applied, yield of the cotton in Treatment CRFs was 18.9% and 13.6% higher than that in CK (CCFs), respectively. Besides, CRFs also significantly increased the content of NO₃⁻-N in the soil of the 0~40 cm soil layer, but didn’t affect much the content of NH NO₄ -N in the soil. No significant difference was observed in content of available P and K between Treatments CRFs and CCFs.

Abstract:To explore effect of controlled release fertilizer (CRF) on yield of peanut and balance of available N in red soil mulched with rice straw, a field experiment designed to have six treatments, i.e. Treatment MF20 (M stands for mulching, F for fertilizer and the number for the proportion CRF accounted for of the total fertilizer applied, here 20%), Treatment MF40, Treatment MF60, Treatment MF0, Treatment CK1 (mulching only) and CK2 (no mulching in addition to split application of fertilizer), was conducted. Results show that Treatment MF20 was the highest, and similar to Treatment CK2, in peanut yield, show a declining trend with increasing proportion of CRF. Treatment MF20 was also the highest in apparent N utilization efficiency, reaching up to 57.39% and being 20.94% and 3.84% higher than Treatment MF0 and Treatment CK2, respectively, and in N agronomic use efficiency, partial productivity, N uptake efficiency and total nitrogen uptake, as well. All the proceeding indices declined with rising proportion of CRF, once beyond 20%, but the index of apparent N loss rate displayed a reverse trend. (ANLR) and the index of soil N surplus did, too. Based on the balance of soil available nitrogen in the test soil, the technique of halving the nitrogen application rate is an effective measure to tap the N fixing potential of the crop per se, to improve nitrogen fertilizer utilization efficiency while ensuring a stable high yield of peanut in the upland red soil mulched with rice straw.

Abstract:A long-term fertilization field experiment on rice has been going on since 1982 in the Red Soil Experiment Station of CAAS to investigate effects of combined application of organic and chemical fertilizers on crop yield and contents of soil available nitrogen, phosphorus and potassium. Results show that higher fertilization rate raised crop yield. Long-term application of organic and chemical fertilizer(NPKM) could increase the rice yield, and enrich the soil fertility. If long-term application chemical fertilizer(NPK), the rice production will reduce.In treatments the same in N application rate, amendment of phosphate fertilizer was higher than amendment of potash fertilizer, in yield-raising effect and it was particularly obvious with early rice. No significant difference was observed between treatments receiving for long organic fertilizer only and chemical fertilizer only in yield-raising effect. With the experiment going on and on, differences between treatments got more and more significant. In all the treatments, alkalysable-N increasing rates showed a similar trend, low-high-low. Organic fertilizer was better than chemical fertilizer in raising alkalysable-N content (p<0.05). Accumulation of soil available phosphorus was mainly related to application of chemical phosphate fertilizer. In terms of the mean content of soil available P of the years, the treatments displayed an order of NPKM, NPM and PKM > NPK > M and NKM (p<0.01). Soil available K increased the fastest in Treatments NPKM, NKM and PKM and the slowest in Treatment NPK. With increased N and P fertilizers application rate, surplus of nitrogen and phosphorus appeared in soil. However, Treatment NPKM was better than all the others in mitigating the surplus. Potassium deficit was observed in all the treatments, suggesting that to maintain the basic balance of soil potassium, at least 200 kg hm^-2 of K₂O should be supplemented in red soil paddy fields annually.

Abstract:Decomposition and distribution of carbon derived from organic materials in paddy soils in the red soil region of subtropical China as affected by moisture regime (aerobic, flooding and wet-dry alternating) were investigated in laboratory through incubation experiments. Results indicate that organic material decomposition rate was the highest in the soil under wet –dry alternation and the lowest in the soil under flooding. Amendment of organic materials promoted mineralization of soil original carbon native in the soils under aerobic and flooding conditions, displaying a positive priming effect, but reversely in the soil under wet-dry alternation, showing a negative priming effect. The priming effects weakened with the incubation going on. ΔlogK and E4/E6 ratio of humic acid was significantly lower in the soil amended with organic material under wet-dry alternation than in the soils under flooding and aerobic conditions. Flooding made humic acid in the soil simple in structure, while wet-dry alternation made it complicated, with enhanced aromatization and humification. The distribution ratio of organic material-derived carbon in soil humus fractions showed that wet-dry alternation and aerobic condition promoted formation of humic acid, conversion of fulvic acid fraction and decomposition of humic acid fraction native in the soils. In the soil under flooding, the carbon derived from organic materials accounted for a high proportion in soil fulvic acid fraction and inhibited decomposition of soil native humic acid components. A high proportion of the carbon derived from organic materials was distributed in > 0.053 mm aggregates, which was especially obvious in the soil under wet-dry alternation and flooding.

Abstract:Consecutive vegetable cultivation in greenhouse easily induces soil acidification or salinization and serious soil-borne diseases, which considerably affects sustainable development of the vegetable production. It is of great urgency to develop some effective techniques and methods to improve degraded vegetable soils. A pot experiment was conducted for comparative study on effects of the application of rice straw (RS), ryegrass (RG) and chicken manure (CM) at different rates (1%, 3% and 7%, of the soil in pot) coupled with or without flooding for 15 days on degraded vegetable soil. Compared to CK_d (no manure and no flooding) and CK_f (flooding only), the practices accelerated decline of soil Eh effectively eliminate accumulated NO3-, lowered the content of SO₄²⁻ and increased soil pH. The effect became more significant with the increasing application rate of organic manure. In the ameliorated soils, except for soils applied with 7% of RS or CM, cucumber was better in growth and yield than in CK_d and CK_f. In terms of soil ameliorating effect, the organic manures show a decreasing order of RG > RS > CM. However, more organic manure does not necessarily improve cucumber in growth or yield.

Abstract:Soil moisture is a leading factor that affects turnover of the labile and resistant soil carbon pools, while the turnover rate of soil organic carbon has a potential important impact on global climate change. An indoor paddy soil incubation experiment was carried out to explore effect of drying-rewetting alternation on mineralization of soil organic carbon and evaluate different soil carbon pools and their degradation dynamics using a two-order model. Results show that drying-rewetting alternation significantly stimulated soil respiration as well as metabolic activity of soil microbes. Three successive rounds of drying-rewetting alternation stimulated soil respiration by 119.3%, 159.5% and 87.3%, respectively, and with the alternation increasing in frequency, the effect intensified first and then waned. After rounds of alternation, the release of CO₂ accumulated in the soil fell lower than that from the soil kept permanently wet because the mineralization stimulated by rewetting was far from enough to make up the drop in mineralization during the drying period. Within the hours after rewetting, soil soluble organic carbon rose and then fell in content. Drying-rewetting alternation raised degradation rate of the soil labile carbon pool and lowered that of the soil resistant carbon pool. After rewetting, the soil labile carbon pool was significantly bigger in size. Frequent drying-rewetting alternation lowered soil fungi/bacteria ratio and altered the community structure of soil microbes, pushing bacteria into dominancy.

Abstract:Based on a long-term (33 years) fertilization experiment, changes in form and content of phosphorus in mountain red soil were investigated. Results show that the long-term P fertilization increased both Total P and readily available P in content in the soil, leading to significant accumulation of inorganic and organic P in the surface soil layer. In soils under P treatment inorganic fraction of P was composed mainly of Fe-P, which accounted for about 50%. Correlation analysis shows that readily available P was significantly related to Fe-P and Al-P with correlation coefficient being 0.908** and 0.706*, respectively, which means that Fe-P and Al-P are the sources of readily available P in the soil. The results also show that Fe-P increased with phosphate fertilization, but Al-P reduced, which somewhat affected the content of soil available P. Soil organic P in the mountain red soil under long-term fertilization can sorted into four forms, that is, active organic P, moderately active organic P, moderately stable organic P and highly stable organic P. Soil organic P decreased somewhat in the soils without P fertilization and increased in the soils with P fertilization. In the soils with P fertilization the four soil organic P followed a decreasing order of moderately stable organic P > moderately active organic P > highly stable organic P > active organic P, of which the first two accounted for 90% or so. Correlation analysis of organic fractions of P and readily available P shows that readily available P was significantly and positively related to moderately active organic P and moderately stable organic P, with correlation coefficient being 0.861** and 0.840*, respectively, which demonstrates that moderately active organic P and moderately stable organic P are the major sources of readily available P in the soil. It was also found that a higher application rate of P coupled with N, K and barnyard manure can promote transformation of other forms of organic P into moderately active organic P and moderately stable organic P that are easily absorbed by crops.

Abstract:Soil dissolved organic carbon (DOC) is an important fraction in the global carbon cycle and is critical to soil biogeochemical processes related to soil fertility and climate change. Soil bacteria play an important role in controlling soil DOC dynamics. To determine effects of phosphorus (P) fertilization rate on paddy field soil mineralization of the soil organic carbon, DOC structural complexity and bacterial community structures, a stationary field experiment, designed to have four P application rates, i.e. 0, 30, 60 and 90 kg hm^-2a^-1 of superphosphate, was carried out in a paddy field, and lab analysis was performed with the 3D EEMs and 454 pyrosequencing techniques. Results show that higher P application rate raised the content of soil readily available phosphorus (Olsen-P), thus increasing the content of soil DOC, and DOC mineralization rate and accumulative mineralization as well. Analysis with the 3D EEMs demonstrates that P input increased fluorescence index and β/α index of the DOC by 1%~10% and 3%-21%, respectively, but decreased its humification index, which were significantly related to soil biochemical properties (Olsen-P, DOC and β-glucosidase). The results also indicate that P application increased the content of Olsen P, stimulated formation of microbe-derived DOC and meanwhile decreased the aromatization degree, molecular weight and humification degree of the DOC, thus improving the biodegradability of the DOC. P input also increased the abundance and diversity of microbial communities, and in particular, induced growth of a variety of carbon-degrading bacteria , thus speeding up degradation of complicated organic carbon and oxidation of methane. Besides, principal component analysis shows that the effect of P fertilization on mineralization of SOC and diversity of bacterial communities was the most significant when P 30～60 kg hm^-2a^-1 was applied. It is, therefore, assumed that a proper rate of P applied may significantly stimulate the activity of C-degradation-related microbes, and hence improve the biodegradability of DOC, accelerate mineralization of the soil organic carbon and promote the cycling of soil organic carbon in paddy field.

Abstract:Phosphorus solubilizing effects of four strains of phosphorus solubilizing bacteria (PSB) screened out of the red soil in Jiangxi Province were studied and compared through incubation in PVK solution containing AlPO₄ as phosphorus source. Results show that all the four strains displayed significant phosphorus solubilizing effects in the solution. Among the four, Strain B1 was the most effective in dissolving phosphorus. After four days of incubation, it dissolved 292.8 mg L^-1 phosphorus. Solution pH in all the treatments decreased to a varying extent from pH 7.0 to pH 3.2 ~ 4.7, during the incubation period. HPLC analysis shows that the presence of organic acids, varying in type and amount with the time of incubation, in the culture medium of all the strains. Oxalic acid and malic acid were found to the dominant organic acids in the culture medium of strain B1 and reached 5 mmol L^-1 in total concentration after 1 day of incubation. The experiment of adding organic acids to activate AlPO₄ indicates that B1 secreting organic acids to dissolve phosphorus is only one of the mechanisms of its phosphorus solubilizing capability. It was found that B1 favored a solution with pH varying between 5 and 9 and incubation under 30℃ and for a triangular flask (100ml), the most suitable content of medium was 30~40 ml. Identification of strain B1 shows that the strain is 99.9% in similarity to Bacillus thuringiensis in 16S rDNA genes.

Abstract:In seeking for alternatives of potash fertilizer, a strain of potassium-dissolving bacteria coded as G4 was isolated from the red earth in Jiangxi Province. The strain of bacteria is very efficient in dissolving potassium, reaching 27.62% in potassium dissolving rate. G4 was tentatively identified as Paenibacillus sp. based on its morphological, physiological and biochemical features and its 16S rDNA sequence analysis. A single factor experiment and an orthogonal experiment was performed on the strain and found its optimal incubation conditions were maltose 1% (w/v), peptone 0.2% (w/v), dipotassium hydrogen phosphate 0.05% (w/v), temperature 25 ℃, initial pH 7.5, medium volume 80 ml in a 250 ml flask, duration of the incubation 48 h and inoculation rate 7%. Strain G4 is quite good at dissolving potassium, and has the potential to be used in development of microbial fertilizer.

Abstract:Earthworms (Eisenia fetida) as subject in the test are exposed to chlorpyrifos of a sub-lethal dose for 8 weeks in artificial soil．Effects of the exposure on SOD, CAT, and GSH-Px activities in earthworms were observed. Results show that the compound suppressed the activities significantly. So the enzymes of the anti-oxidizing defense system of earthworms can be cited as indicators of chlorpyrifos toxicity. Besides the commonly used ecological toxicity indexes, such as LC₅₀, oviposition rate and hatching rate, the activities of the antioxidases, were closely related to the toxic effect of the pesticide. However, the enzymes varied in sensitivity to the chemical． SOD and GSH-Px were more sensitive than CAT．Therefore, in diagnosing ecological toxicity, it is advisable to have different indices form a mutually supplementary indicator system to improve the sensitivity and efficiency of pollution identification and long term diagnosis．

Abstract:To explore effect of biological soil crusts (BSCs) on soil microbial biomass carbon（SMBC）and nitrogen（SMBN）, soil of a sand dune covered with BSCs in the artificially revegetated sand zone at the southeastern edge of the Tengger Desert, China was selected as subject of the study. Four sample plots were set different in sand-fixing time (55, 47, 30 and 20 a, separately), and a plot of mobile sand dunes and a plot of natural vegetation as control. Results show that cyanobacteria-lichen and moss crusts significantly increased the contents of SMBC and SMBN in artificially revegetated areas (p<0.05), which was positively related to sand-fixing time（p<0.05). Crust type was also a factor, significantly affecting the content of soil microbial biomass. The contents of SMBC and SMBN under moss crusts were significantly higher than those under cyanobacteria-lichen crusts（p<0.05). In addition, BSCs significantly increased the contents of SMBC and SMBN in the 0~20 cm soil layers（p<0.05）and the effect weakened with increasing soil depth. Moreover, the contents of SMBC and SMBN under BSCs varied seasonally to a significant level, showing a decreasing order of in summer > in spring > in autumn. Heat and water were two main factors controlling the seasonal variation, while BSCs affected soil microbial biomass seasonally by regulating soil temperature and moisture.

Abstract:

Abstract:

Abstract:

Abstract:

Abstract: