清涧河流域的水文情势变化阶段及其特征

 为探讨清涧河流域不同阶段的水文变化特性,分析流域水文变化的原因,通过定量指标结合定性原则,筛选了清涧河流域内的代表性雨量站,在此基础上,建立了具有一致性的1955—2002年的降水量序列资料;采用滑动平均和有序聚类分析方法,对选定的水文序列进行阶段划分,并统计分析各阶段降水、径流的变化特性;结合流域水土保持措施状况,进一步讨论引起流域水文变化可能的原因。结果表明:清涧河流域的水文序列可划分为3个阶段,分别为:1955—1979、1980—1989和1990—2002。与第1阶段相比,第2、3阶段汛期和年降水量呈减少趋势;第2阶段径流量小于第1阶段,第3阶段平均径流量大于前2个阶段。各阶段年降水量与径流量之间具有正相关关系,但点群散乱,相关性不好;各阶段暴雨特性和水土保持措施数量、质量的变化,是流域水文变化的主要原因。     

Nitrification activity in submerged soils and its relation to denitrification loss

Summary Nitrification activity (formation of NO ₂ ^– + NO ₃ ^– per unit soil weight) was measured in the surface layer of 15 presubmerged soils incubated in petri dishes under flooded but aerobic conditions. soils with pH above 5 nitrified quickly, whereas soils with pH below this level did not nitrify or nitrified slowly. The pH values between 7 and 8.5 were optimal for nitrification. Organic-matter levels in the 15 soils of our study did not influence their nitrification activities. In a follow-up greenhouse pot study, after a period of 3 weeks, ¹⁵N-balance measurements showed that the loss of N through apparent denitrification did not follow the nitrification patterns of the soils observed in the petri dishes. Apparent denitrification accounted for 16.8% and 18.9% loss of ¹⁵N from a soil with insignificant nitrification activity and a soil with high nitrification activity, respectively. These results, thus, indicate a lack of correspondence between the nitrification activities of soil and the denitrification loss of N when the former was measured in the dark and the latter was estimated in the light. Soils that nitrified in the darkness of the incubator did not nitrify in the daylight in the greenhouse.     

Speciation of copper in soils and relation with its concentration in fruits

Abstract

Different extraction reagents were studied in soils and the results obtained were compared with copper (Cu) contents of seven type fruits grown in these soils. For fruits, wet and dry ashing methods were applied and acceptable results were obtained by using dry ashing. The speciation is based on the dissolution of the soil samples in HNO₃/H₂O₂, oxalic acid, acetic acid, EDTA and citric acid as extraction reagents at hot and cold conditions. Mean total Cu concentrations for all fruits studied were (mg kg^‐1) in the range of 3.0–7.0 (dried weight basis). Significant positive correlations have been found between Cu contents of various fruits and different extractants studied. Flame atomic absorption spectrometry was used for determination of Cu in digestions. Probable chemical forms of Cu in soils were evaluated.     

Salt regime of post-irrigated soils at the Kislovsk irrigation system

The study of post-irrigated and virgin soils at the Kislovsk irrigation system has shown that the salt regime of the post-irrigated soils is determined by the (1) depth and salinity of the groundwater, (2) the litho-logical structure of the soil and subsoil, (3) the local microtopography, (4) the presence or absence of a solonetzic horizon in the post-irrigated solonetzes, and (5) the portion of solonetzes in the soil cover. The post-irrigated soil complexes on the Privolzhsk sand ridge with a groundwater depth of more than 4 m do not undergo secondary salinization. At the groundwater depth of 2.0–2.6 m, post-irrigated meadow-chestnut soils remain nonsaline, chestnut soils and solonetzes with an artificially destroyed (due to deep tillage) solonetzic horizon undergo desalinization, and solonetzes with a preserved solonetzic horizon undergo salinization in the subsolonetzic layers. The post-irrigated soils of the Khvalyn undrained sea plain used for rainfed farming have become saline in the deep part of the profile, and their plow layers remain nonsaline.     

Mycostasis in relation to the microbial nutrient sinks of five soils

[^l4C]exudation from fungal propagules on 5 soils over 4–24 h was studied in relation to mycostasis. [^l4C]exudation from sclerotia of Macrophomina phaseolina, chlamydospores of Thielaviopsis basicola, and conidia of Cochliobolus victoriae after 24 h on two sandy loam soils and a loam was generally greater than exudation on the two clay loam soils. Results were similar for conidia of Stemphylium sarcinaeforme but differences were not statistically significant. When natural soils were pulsed with [¹⁴C]glucose, ¹⁴CO₂ evolved by the soil microflora over 2–12 h showed a similar trend. [¹⁴C]exudation from M. phaseolina sclerotia and C. victoriae conidia incubated on soils was greater than that from propagules incubated aseptically on a bed of sand through which water percolated at a flow rate sufficient to inhibit germination. Propagules of C. victoriae, M. phaseolinia and T. basicola germinated greater on one or more of the coarse-textured soils than on fine-textured soils. Using γ-irradiated soils, more [^l4C]exudate was adsorbed by the clay loams than by the loam and sandy loam soils, suggesting that the adsorptive capacity of soils may be an important factor in controlling fungal utilization of soluble nutrients. Fungal germination in soil appears to be jointly influenced by two opposing tendencies: the ease with which germination occurs in response to exogenous nutrients and the amount of endogenous substrate lost or retained.     

Nitrogen regime of soils with different macrosymbiont genotypes

The specificity of the nitrogen regime in gray forest and meadow-chernozemic soils under the effect of different genotypes of peas (Pisum sativum L.) was shown under field and optimal hydrothermal conditions. The dynamics of the nitrogen form ratios in soils with and without symbiotic nitrogen fixation was studied. The role of the macrosymbiont type genotype in the accumulation of ammonium, nitrate, and microbial nitrogen in soils was revealed.     

土壤磷有效性及其与土壤性质关系的研究

选取我国14个不同地点土样,测定理化性质、全磷、速效磷、水溶性磷含量,采用通径分析研究土壤磷有效性与土壤性质的关系。结果表明,土壤磷有效性是各个土壤性质综合作用的结果。土壤CEC、有机碳、粘粒、砂粒、碳酸钙含量对土壤速效磷比例影响显著,土壤CEC、粘粒、砂粒含量对土壤速效磷比例贡献为正值,而土壤有机碳对土壤速效磷比例贡献为负值;土壤pH和CEC含量对土壤水溶性磷含量影响显著,土壤pH对水溶性磷比例贡献为正值,土壤CEC对土壤水溶性磷比例贡献为负值。本文所选土样基本符合土壤磷有效性与土壤性质之间通径分析的结果。     

Sulfur transformations in relation to carbon and nitrogen in incubated soils

Changes in biomass-S in relationship to biomass-C and N were evaluated, and the transformation of ³⁵S-labelled SO₄^2? among organic matter fractions were followed during incubation of a Black Chernozemic (Udic Haploboroll) and Orthic Gray Luvisol (Typic Cryoboralf) soils. There was a net immobilization of S with and without the addition of cellulose or sulfate after 64 days. In contrast, a net mineralization of N occurred. Cellulose decomposition rates responded to supplies of S available for new microbial cell synthesis.Fluctuations in the amounts of biomass-S during incubation of both soils followed biomass-C and biomass-N changes and C/S and C/N ratios of the biomass ranged between 47–121 and 4.9–7.7, respectively. Microbially-incorporated S was found concentrated within the biomass or partially transformed into soil organic matter.Fractionation of soils after incubation, by a 0.1 m NaOH-0.1 m Na₄P₂o₇ extraction-separation technique showed significant increases in the C and N contents of the conventional humic acid (HA-A) and fulvic acid (FA-A), and humin (<2 μm) fractions. Biomass C accounted for 20–64% of the observed increases in these fractions suggesting that the differences were due partly to transformed microbial products and partly to microbial cell organic constituents released on lysis of cells during incubation. In contrast to C and N, the contents of total S and HI-reducible S increased in the FA-A fraction only and accounted for 45–76% of the immobilized labelled S.     

Criteria and methods to assess the ecological status of soils in relation to the landscaping of urban territories

The ecological status and functioning of soils in urban ecosystems are considered. A series of criteria and simple methods of their determination are suggested to assess soil suitability for landscaping purposes. Their practical application is shown by the example of the ecological assessment and monitoring survey of different urban territories in the southwestern, western, and northwestern administrative districts of Moscow and in Moscow suburbs. It is shown that the main damage to the soils of actively used territories in Moscow is due to the artificial salinization induced by the application of deicing substances and fertilizers. The second factor of soil degradation is the soil compaction. An unfavorable water and air regime (a deficit or excess of soil moisture) is a factor that manifests itself sporadically in time (during the extremely dry years) and in space (at the sites with an increased soil compaction and soil water evaporation). A considerable decrease in the potential biological activity of urban soils, including the soils of newly built residential areas, in comparison with their natural analogues attests to the disturbance of their functioning under the impact of chemical pollution and an unfavorable physical status.     

Micronutrients distribution in salt-affected soils of the Punjab in relation to soil properties

Salt-affected soils in arid and semi-arid tracts of the Indian Punjab are prone to deficiency of micronutrients. Nine profiles from alluvial terraces, sand dunes and palaeochannels in the southwestern Punjab were investigated for total and diethylenetriamine-penta-acetic acid (DTPA) extractable Zn, Cu, Mn and Fe. Soil physiography exerted significant influence on the spatial distribution of micronutrients. Total contents varied from 20–78 for Zn, 8–32 for Cu, and 88–466 mg kg^?1 for Mn and 0.82–2.53% for Fe. DTPA-extractable contents varied from 0.10–0.98 for Zn, 0.14–1.02 for Cu, 0.54–13.02 for Fe and 0.82–9.4 mg kg^?1 for Mn. Total contents were higher in fine-textured soil than in coarse-textured soils. Concentration of micronutrients in the surface layer was low and there occurred more accumulation in the Cambic horizon. Organic carbon, pH, clay, silt and calcium carbonate exerted strong influence on the distribution of micronutrients. DTPA extractable Zn, Cu, Mn and Fe increased with increasing organic carbon but decreased with increase in pH and calcium carbonate content. Total micronutrient contents increased with increase in clay, silt and calcium carbonate contents and decreased with increase in sand content.     

Temperature regime of agrosoddy-podzolic soils on slopes of different steepness

Soil temperature regime at the depth of 20 cm may vary considerably on different parts of a given slope. This variation may be related to the position of the particular site on the slope and to the geomorphic features of the slope, including its surface inclination. The soils of the upper steep part of the slope of southern aspect are subjected to more active warming in the spring. They are characterized by higher cumulative temperatures above 10°C. The degree of this difference depends on the particular weather conditions. The differences in the soil temperature regimes may be the reason for the unequal crop yields on the different parts of the slope.     

The effect of soil texture and organic amendment on the hydrological behaviour of coarse-textured soils

To gain more insight into the hydrological behaviour of coarse-textured soils, the physical properties of artificially created soil mixtures with different texture were determined. The mixtures were prepared according to the specifications of the United States Golf Association (USGA) for constructing putting greens. In addition, the effect of 10 vol.% organic matter addition was studied. The soil moisture retention and hydraulic conductivity relationships of the different mixtures were determined and their hydrological behaviour was studied using the numerical model SoWaM. Both texture and organic matter addition substantially affected the hydraulic properties. Hydraulic conductivity significantly increased with increasing coarseness while moisture retention decreased. On the other hand, organic matter addition reduced saturated hydraulic conductivity by a factor of 10 to 100 and distinctly increased moisture retention capacity. The amounts of total available water were increased by the addition of organic matter between 144% (slightly coarse texture) and 434% (very coarse texture). Results indicate that the mixtures can contain only 2–16% plant available water and therefore need frequent irrigation to maintain plant growth. Addition of organic matter seems a good solution to reduce the irrigation water requirements but it increases the risk of ponding or runoff because of large reductions in the saturated hydraulic conductivity sometimes to below the rate of 3.6 m/day recommended by the USGA.     

Amitrole degradation in vineyard soils in relation to pedo-climatic conditions

The fate of [¹⁴C]-amitrole herbicide was studied in eight soils having different capacities for amitrole mineralisation. Laboratory incubations were run combining different experimental conditions: temperature (4, 28 and 50°C), soil moisture (50, 100 and 150% of soil water holding capacity) and microbial activity (sterile and non-sterile conditions). During incubation, samples of the soils were periodically extracted with 0.5 M NH₄OH and extracts were analysed by HPLC. The lengths of time needed for 50% dissipation of amitrole (DT50) in soils ranged from less than 1 day to more than 70 days. Amitrole mineralisation occurred only in non-sterile soils, showing that it is a biological process. Mineralisation was lower in soils with a coarse texture than in soils with a fine texture. Soil water content had little influence on the total amount of amitrole mineralised at the end of incubation. Temperature had a greater influence on mineralisation, although rates were still high at low and high temperatures. In non-sterile as in sterile soils, the major product detected in the extracts was amitrole. Additional non-identified radioactivity was occasionally extracted. However, it never represented more than 10% of initially applied amitrole. Non-extractable residues represented less than 15% of applied radioactivity in acidic soils and about 30% of applied radioactivity in alkaline and neutral soils. The amount of non-extractable radioactivity formed was enhanced in sterile as compared to non-sterile soils. Furthermore, in sterile soils, high temperature induced an increase of non-extractable residues, showing that amitrole is chemically quite reactive.     

Thermal regime of tundra soils under reclamation and restoration of natural vegetation

This paper covers the specifics of the temperature regime in reclaimed tundra soils under a sown perennial herb meadow and a restored (secondary) ecosystem as compared to the small-shrub yernik (birch)-willow-moss and shrub yernik-willow-moss tundra types. The taxonomic position of the anthropogenic soils and those of the secondary (restored) biogeocenosis is discussed as related to the transformation or regeneration of the biotic and thermal components of the biogeocenosis. The soil development causes profound changes in the freezing-thawing regime, which gives grounds to distinguish the developed soils as an individual soil type.     

Potassium-supplying power of some northern-Greece soils in relation to clay-mineral composition

The correlation between the content of the clay minerals, mica, montmorillonite or vermiculite, and the logarithmic form $\text{pK-}\text{1}\text{2}\text{p (Ca + Mg)}$ of the activity ratio (K)/√(Ca + Mg) was highly significant for 23 soils from northern Greece. The correlation was negative with mica and positive with montmorillonite and vermiculite. A free-energy term, ΔF¹, necessary to bring the activity ratio of each soil equal to the lowest value encountered, using the concentrations of soluble and exchangeable K and Ca + Mg in the equilibrium systems, was also calculated. The relationship between the content of the three clay minerals and ΔF¹ was the same as when $\text{pK-}\text{1}\text{2}\text{p (Ca + Mg)}$ was used except that the correlation coefficient was greater in all cases, being significant at P_0.001 with each of the clay minerals. The regression of ΔF¹ on each of the clay mineral contents was also much greater than the corresponding ones with $\text{pK-}\text{1}\text{2}\text{p (Ca + Mg)}$.     

Pore shape and organic compounds drive major changes in the hydrological characteristics of agricultural soils

A small increase in soil organic matter (SOM) content can change soil hydrological properties from a completely wettable to a partially water‐repellent state. Although considerable research describes hydrophobic compounds as a primary driver of this shift, the influence of pore shape has only been considered in a few studies and none of these has emphasized the role of different carbon compounds. Using a capillary bundle model of non‐cylindrical (wavy) capillaries, we described measured hydrological properties of five agricultural soils that have a small degree of water repellency and textures ranging from coarse sand to heavy clay. To isolate the influence of SOM, it was removed by combustion to provide an SOM‐free treatment. Water and methanol sorptivities quantified infiltration rates and soil‐water wetting angles in packed soil cores. Different cores were sectioned to measure wetting profiles and calculate diffusivity. The results from natural soils were supplemented by measurements carried out on model ‘soils’ consisting of quartz particles (50–200 µm) with four different hydrophobic states. Soil organic matter removal increased water sorptivity from about 60% for a coarse sandy soil (Haplic Arenosol) to about 290% for a heavy clay soil (Haplic Leptosol), corresponding to a decreased apparent wetting angle of 20–30°. Application of the wavy pore model suggests that the apparent wetting angle resulting from SOM removal can be several times smaller than its Young value. Generally, SOM removal increased water diffusivity values by one to two orders of magnitudes. The SOM components having the greatest impact on contact angle were hexanedioic acid and heneicosanoic acid (both hydrophilic) and docosane (hydrophobic).     

中国青海湖地区草地蝗虫与土壤的关系

A growth chamber study was conducted to determine the relationships between the supply of soil available nitrogen （N） and sulfur （S） and canola （Brassica napus） and wheat （Triticum aestivum L. ‘Biggar＇） N and S uptake and yield in three Western Canadian soils. The suitability of one-hour burial with an anion exchange membrane （AEM） was assessed for its utility as a quick test of the available N：S balance in the soil. Canola and wheat were grown on a Luvisolic soil low in available S and on Brown and Black Chernozemic soils low in both available N and S, with different rates and combinations of N and S fertilizers applied. AEM burial was used to assess soil available nitrate and sulfate supply rates after fertilization. Dry matter yield and N and S concentrations in plant tissues were determined after 6 weeks of growth. The soil available N：S ratio determined by AEM burial closely reflected the relative supplies of available N and S as revealed in the N：S ratios of plant tissue dry matter. The highest yields were achieved where the available N：S ratio in soil and plant tissue ranged from 5 to 13. Thus, a one-hour burial of an AEM probe in the field may be a useful tool to quickly test if a balanced N and S supply is present in the soil for optimum crop yield.     

耕作土壤释钾速率及其与钾有效性的关系研究

对 1 0个不同母质土壤进行生物吸钾试验和化学测定 .结果表明 ,二级动力学方程dkt/dt=k(k0 -kt) 2 可以很好地描述连续提取条件下土壤释钾特性。初始释钾速率与有效钾含量呈极显著正相关 ,与黑麦草生物总量及吸钾总量均呈极显著正相关 .2mol/LHNO3提取的释钾速率相关显著性明显高于氢质树脂法 ,其中 0～ 2h的土壤释钾速率能较好地描述土壤钾的有效性     

Carbon stocks in Ethiopian soils in relation to land use and soil management

The effect of soil management and land use change are of interest to the sustainable land management for improving the environment and advancing food security in developing countries. Both anthropogenic changes and natural processes affect agriculture primarily by altering soil quality. This paper reviews and synthesizes the available literatures related to the influence of soil management and land use changes on soil carbon (C) stock in Ethiopia. The review shows that topsoil C stock declines approximately 0–63%, 0–23%, and 17–83% upon land use conversion from forest to crop land, to open grazing, and to plantation, respectively. An increase of 1–3% in soil C stock was observed within 10 years of converting open grazed land to protected enclosures. However, there was a little change in soil C stock below 20 cm depth. There is a large potential of increasing SOC pool with adoption of land restorative measures. Total potential of soil C sequestration with the adoption of restoration measures ranges 0·066–2·2 Tg C y⁻¹ on rain‐fed cropland and 4·2–10·5 Tg C y⁻¹ on rangeland. Given large area and diverse ecological conditions in Ethiopia, research data available in published literature are rather scanty. Therefore, researchable priorities identified in this review are important. Copyright © 2008 John Wiley & Sons, Ltd.