The variation of soil water regime, oxygen status and rooting pattern with soil type under Sitka spruce

Soil water regime, oxygen status and rooting pattern under Sitka spruce were characterized in five soil types: a waterlogged peaty gley, a peaty gley, a flushed peaty gley, a surface water gley and a brown forest soil during 1982. The waterlogged peaty gley had a high water-table which only dropped below 30 cm depth for 46 d during the summer. Below the water-table the profile was anoxic and rooting was restricted to a depth of 12cm. The peaty gley experienced seasonal waterlogging with a winter water-table around 15cm depth. Roots that grew further down the profile during the summer as the topsoil dried to –100 kPa matric potential were later killed when the water-table rose. The top 30 cm of the flushed peaty gley remained oxygenated even below the water-table. Roots survived below the winter water-table. The top 30 cm of the surface water gley and brown forest soil were freely draining and remained aerated throughout the year. The platinum electrode polarographic method demonstrated that there was a sharp transition to anoxic conditions just above the water-table at the first two sites.     

中国几种主要土壤的持水性质

土壤的持水性是指土壤吸持水分的能力。在对植物的有效范围内,土壤所吸持的水分是由土壤孔隙的毛管引力和土壤颗粒的分子引力所引起的,这两种力现在统称为土壤吸力,或基质吸力,它相当于土壤总水势中的基质势。     

SOME EFFECTS SUB-SURFACE DRAINAGE AND PLOUGHING ON THE STRUCTURE and COMPACTABILITY A CLAY SOIL

In a field experiment to determine the direct and indirect effect on soil structure, of sub-surface piped drainage as compared with natural surface drainage only, in ploughed and unploughed soil, a factorial systematic design with four replicated blocks was used. Structural changes were monitored during 8 months of natural rain and finally irrigation, by measuring surface heights and soil strength (penetration resistance) in relation to moisture content and matric suction, at plough sole depth (27 cm). A compaction test using a tractor with differentially loaded wheels, was applied at various times after irrigation, measuring the resulting wheel sinkage and wet density of the soil. The effects of the drainage treatments were found to be temporary, except a ‘crusting’ effect during the drying of the unploughed surface drained soil. The ploughed soil with sub-surface drainage showed greater frost heave than the undrained soil. The soil strength at 7.5-22.5 cm. depth was linearly related to the matric suction within the range of –3 to 20 cm-water. The compaction data for the unploughed soil suggested relationships between matric suction, sinkage, and wet density, but complicated interactions prevented any general conclusion. In the ploughed soil, compaction data established the beneficial effects of subsurface drainage in reducing damage from tractor traffic, decreasing wheel sinkage and reducing compaction both below and 16 cm from the track edge. A rise in matric suction of 10 cm-water, in the range 2-24 cm-water was, on the average, as effective in reducing rutting as a wheel load reduction of 670 kg (0.54 kg/cm² reduction of tyre inflation pressure). It was concluded that for clay soils having a temporary excess moisture, draining the water table to below 50-60 cm depth should be recommended as a precautionary measure to minimize structural damage.     

土壤基质吸力与土壤微生物活性关系的研究

研究了土壤微生物活性与土壤基膜吸力的关系，将土壤发泡点，即土壤导气率由0突变为非0时的基质吸力，与微生物的最高呼吸活性相联系，试图证明土壤微生物的最高活性发生于略高于土壤发泡点的基模吸力。对粗沙土、细沙土和砂壤土三种轻质地土壤的测定表明，土壤微生物的最高呼吸活性发生在略高于土壤发泡吸力的基质吸力。土壤基模吸力较小时微生物活性到达最高值的速度较慢，土壤基模吸力在发泡点附近时，微生物活性到达最高值的速度较快。     

上海地区土壤持水特性研究

土壤水的研究,从Henri Darcy(1856)提出达西定律算起,已有一百多年历史.经历了由经验到理论、由静态到动态、由定性到定量、由宏观到微观逐步深入发展的过程^[1].1877年Briggs L.J.提出毛管假说,将土壤孔隙组成的孔道看成是一些大小不同的毛细管,认为表面张力是土壤保持水分的主要原因.     

Water and oxygen regimes under conifer plantations and native vegetation on upland peaty gley soil and deep peat soils

Concentrations of oxygen and carbon dioxide were measured in an upland peaty gley soil during two growing seasons and a deep peat during one season. Measurements were compared with the soil water regimes on both soils. Comparison was also made between planted areas of Sitka spruce and Lodgepole pine, and areas of the native vegetation (Molinia grassland on the peaty gley, and Calluna heath on the deep peat). In 13 m tall pure stands of the pine and spruce on the peaty gley soil about 28% of the rainfall was intercepted by the canopy and evaporated without reaching the soil, and the watertable was deeper and matric potentials were lower than under grass. When the matric potential fell below ?5 kPa in the upper soil layers, high oxygen concentrations prevailed. In undisturbed peat, waterlogged conditions produced an anaerobic regime virtually to the surface, but a 1 m deep drainage ditch lowered the watertable and created an aerobic regime within the top 0.3 m of peat. The presence of tree crops on drained plots increased the depth of drying during the summer months, and aerobic conditions reached 0.4 m depth under Sitka spruce and 0.5m under Lodgepole pine. On the peaty gley also, Lodgepole pine dried and aerated the soil to a greater depth than Sitka spruce during the summer, but no difference in water regime was evident in the winter.     

THE EFFECT OF FARMYARD MANURE ON MATRIC SUCTIONS PREVAILING IN A SANDY LOAM SOIL

Soil matric suctions under a crop of ryegrass on farmyard manure-treated and untreated plots were determined over a total period of 24 weeks from March to November. The soil moisture characteristic of each plot was determined five times throughout this period, and for each plot and on every occasion a linear relationship was found between moisture content and log matric suction. A formula was derived to account for the seasonal changes in moisture characteristic and it was then possible to obtain matric suction values from the soil moisture contents obtained from twice-weekly sampling of each plot. Although differences between available-water capacity of the manured and unmanured plots were small throughout the 6-month period of sampling, the soil matric suctions of the manured plots were almost always lower than those of the unmanured plots. The lower suctions prevailing in the manured soil could be a factor contributing to the higher yields of ryegrass obtained from the manured plots as compared with those obtained from the unmanured plots.     

The response of Aporrectodea rosea and Aporrectodea trapezoides (Oligochaeta: Lubricidae) to moisture gradients in three soil types in the laboratory

The question of whether the response of earthworms to soil moisture is governed by their reaction to soil wetness (moisture content) or to soil water energy (matric suction) was examined in two species of earthworm using moisture gradients in three contrasting soil types with clay contents varying from 4 to 39%. Gravimetric moisture gradients ranging over 5–30% were established in horizontal cores comprising 12 or 14 sections containing loosely packed soil. Earthworms were introduced to each section at the beginning of each experiment. The earthworms moved from sections containing dry soil into adjacent sections containing moister soil. Clear effects were evident after 6 h but these became more obvious after 96 h. For the earthworm Aporrectodea rosea, the threshold soil mositure level at which earthworms were induced to move away from dry soil was a matric suction of about 300 kPa (pF 3.4) and was independent of soil type. In contrast, for A. trapezoides, the threshold soil moisture varied with soil type (sandy loam 15 kPa, loam 25 kPa, clay 300 kPa). We conclude that, for the earthworm A. rosea, matric suction and not water content of soil provided the cue by which the earthworm recognized dry soil. For A. trapezoides, there was an interaction between matric suction and soil type in which the response of A. trapezoides to soil moisture varied with soil texture and the threshold for avoidance of dry soil ranged from a matric suction of 300 kPa (20% w/w) in clay to 15 kPa (10% w/w) in sandy loam.     

庐山区土壤的特征

庐山是长江流域中部的名山,位于鄱阳湖西北面,其地理位置约为北纬29度/35分及东经116度。庐山最高峯的海拔略高于1,500米,它虽不是一座高山,但为避暑胜地,并且是不同领域的自然科学工作者所爱好的科学研究场所。朱显谟曾对庐山土壤作过研究,他着重报导了庐山主要土类的分布和形态。本文报告庐山主要土类的理化性状及其他特征的研究结果。所采取的土样皆分布于自庐山次高峯大月山(海拔约1,450米)经含鄱口,下至山之东南麓白鹿洞一線,其中仅自大月山不远所选的一个剖面在此線之外。本文特别着重于山上土壤与山麓低丘土壤差异的     

Specificity of soil hydrolytically microbial complex under different moisture conditions

It has been established that soil moisture has a significant impact on the activity of chitinolytic microbial processes, rather than pectinolytic processes. The degradation of polysaccharides with an increase in soil moisture in microbial complex markedly increases the role of prokaryotic microorganisms, especially actinomycetes. For the first time, using the FISH method, the amount of detected phylogenetic composition of a metabolically active hydrolytic complex of humus horizons of grey forest and gley and weakly podzolic soil and humus has been estimated depending on the humidity. At optimum moisture, phylogenetic groups Actinobacteria and Firmicutes dominated in the chitinolytic process. An increase in the proportion of proteobacteria is observed with an increase in humidity. The role of gamma- and alphaproteobacteria and actino-bacteria is heightened with the drying of soil in the hydrolytic complex. A quantitative estimate of the rate of degradation of polysaccharides (pectin and chitin) in different types of soils at different levels of moisture is given. The dependence of the phylogenetic composition of an active microbial hydrolytic complex of humus horizons of grey forest and gley, weakly podzolic soils and humus on humidity is revealed.     

长白山北坡原始林采伐对土壤性质影响的研究

长白山北坡是我国中纬度地区保持得比较完好的著名原始林区。林木组成复杂,成林树种丰富,每公顷蓄积量可达300—600立方米。而适合采伐的成过熟林已占绝大部分。据白河林业局资料:其林分蓄积中成过熟林占90.1%,这些成过熟林的林木生长量已大为减退,平均生长率为3.96%,而自然枯损率却占1.87%。特别是针叶树种平均自然枯损率高达3.79%,几乎与平均生长率相等¹⁾,这表明该局的森林资源应及时开发利用。另一方面,这些可采伐的原始林,地处熔岩高原,是第二松花江的源头,现有森林覆被对于调节气候、涵养水源、保持水土的作用是难于估量的。若采伐方式不当,是否会引起森林立地条件恶化而不利于更新造林,导致生态失去平衡并带来极大的灾难。为此,1982年吉林省林学会联合我院等十多个单位,针对上述问题,从各方面进行考察。笔者等用设立标准地调查对比的方法,于落叶松纯林和阔叶红松林采伐迹地上进行研究,现将初步结果报道如下。     

Hydraulic characteristics of conventionally and zero-tilled field plots

A silage corn crop was grown on field plots entering their 2nd-year cycle of zero tillage, and on control plots representing traditional tillage practices. Concurrent measurements of soil matric suction and water content were made under transient conditions of a draining profile without evaporation. The results indicated some similarity in the soil moisture characteristics of the untilled soils which produced high crop yields. The time rate of change of soil water content, the root extraction rate and the unsaturated hydraulic conductivity were always smaller in the zero-tilled plots than in the conventionally tilled plots.     

Methane production and growth of microorganisms under different moisture conditions in soils with added chitin and without it

The limits of soil moisture providing the possibility of methane production and growth of microorganisms in soils with added chitin and without it were determined. Samples of gray forest, soddy-podzolic, gley taiga, chestnut, and chernozemic soils were studied. It was found that methane emission increases significantly under a high soil moisture content in the presence of chitin. The increase of the soil moisture up to the maximum water-holding capacity enhanced the emission of methane by two-six times. The dynamics of the methane emission from the soils in the course of microbial successions initiated by the addition of chitin or by the soil moistening to different levels were studied by the gas-chromatographic method. The population density and biomass of fungal, bacterial, and actinomycetic complexes under different moister levels were studied by the method of luminescent microscopy. It was determined that many microorganisms participate in the transformation of chitin in the soil under conditions of oxygen deficiency (upon the increased moisture content). Prokaryotes dominated by actinomycetes were the group that increased its biomass most actively (the biomass doubling took place).     

Soybean seedling root growth as influenced by soil texture,matric suction and bulk density

Abstract

Laboratory experiments were conducted under controlled conditions to determine the effect of five matric suctions (0.05, 0.10, 0.30, 1.00 and 3.00 bars) and three bulk densities (1.10, 1.30 and 1.50 g.cm^?3) on the moisture content, penetrometer resistance and soybean (Glycine max L.) root growth in six different soil textural groups (sand, silt, clay and their combinations).

The different textural groups were compacted in PVC pipes 4.4 cm ID and 10 cm long and placed in pressure cells to obtain the desired matric suction. After equilibrium five pregerminated soybean seedlings were fixed on the soil surface. At the end of 48 hours root elongation was measured.

There was an increase in root growth in all the textural groups at all the bulk densities when the matric suction was increased from 0.05 to 0.30 bar. There was however a gradual decrease in root growth as the matric suction increased from 0.30 to 3.0 bars. The reduction in root growth at low and high matric suctions was related to moisture content, change in soil resistance and redox status of the soil system.

The measured penetrometer resistance values were directly related to the level of compaction, soil matric suction and also were dependent upon the texture. Close relationships were recorded between redox potentials and soil matric suction.     

鄂西山地的酸性棕壤和灰棕壤形成条件及理化性质

根据鄂西山地的自然成土条件，分析了酸性棕壤、灰棕壤诊断层和诊断特性，主要理化性质和粘土矿物组成，结果表明：酸性棕壤和灰棕壤同属于亚热带中山上部或亚高山中上部冷湿条件下形成的森林土壤。其理化性质与我国北方同类土壤又有较大差别。     

Soils and the soil cover of the taiga zone in the northern Urals (upper reaches of the Pechora River)

The territory in the upper reaches of the Pechora River is characterized by the predominance of Al-Fe-humus and metamorphic soils with gley features developing under the middle taiga fir-spruce forests rather than gley-podzolic soils as had been considered before. Some of the described soil profiles represent intergrades between brown taiga soils (burozems) and gleysols; these soils are absent in the new Russian soil classification system. General regularities of the soil cover are controlled by the geomorphic position of the soils on slopes and by the conditions of ground moistening and lateral soil water flows. The development of modern soil cover patterns is determined by the impact of herbaceous and woody vegetation, bioturbation of the soils by windfalls, the presence of dead tree trunks on the soil surface, and other factors.     

Einfluss des Porenwasserdruckes auf die Zugfestigkeit von Bodenproben

Effect of pore water pressure on tensile strength Direct tensile testing with measurements of the pore water suction was used to investigate the relationship between tensile strength and suction. The tests were conducted on a till and a clayey soil, both homogenized. A closer view is focused on the relationship between material strain and the development of suction. Beyond, the factor χ of the effective stress equation for unsaturated soils by Bishop (1959), which was calculated by the data of tensile strength and corresponding matric suction is compared to the volumetric χ of the tested soil specimens. It could be shown, that the pore water pressure changes with strain. Therefore, not the initial suction of a soil is relevant for its failure but the actual one that can be measured in the failure zone at the moment of fracture. In addition the application of the volumetric χ in the effective stress equation compared to the χ derived from tensile testing leads to an 1.6 to 2.8 fold overestimation of the contribution of matric suction to soil tensile strength.     

Landau–Deryagin law and hydration energy of soils of different genesis

Linear regression equations between the logarithm of the total soil moisture potential and soil moisture content in the hygroscopic moisture range (Landau–Deryagin law) were derived for typical soils from different natural zones of European Russia. From these equations, a compact algorithm was developed for calculating the hydration energy of soils, which increases from 1280 to 10600 J/kg in the following soil series: heavy loamy soddy podzolic soil–heavy loamy gray forest soil–medium loamy light chestnut soil–heavy loamy brown semidesert soil–light clayey solonchak–light clayey chernozem–medium clayey krasnozem. Relationships were revealed between the hydration energy of soils, the specific surface of soils, the content of physical clay in soils, and the concentration of hydrated exchangeably adsorbed ions.     

Water and oxygen regimes of four soil types at Newcastleton Forest, south Scotland

The water and oxygen status of four upland soils under Sitka spruce plantations was studied for 2 years. In a brown earth, waterlogging only occurred ephemerally in the subsoil and oxgen concentrations were generally high. In contrast, waterlogged and near-anaerobic conditions persisted for much of the year in stagnogley and stagnohumic gley soils. In a peaty stagnopodzol moist conditions occurred above and below the thin ironpan, but while high oxygen concentrations generally persisted in the subsoil, low concentrations were common in the soil above. In the brown earth, healthy roots of Sitka spruce were present at a depth of 85 cm, but in the gley soils rooting was mainly limited to 25 cm and many roots were dead. In the peaty stagnopodzol, roots penetrated the ironpan and grew in the subsoil to 75 cm depth.     

A new evaluation of carbon stocks in British forest soils

Carbon (C) stocks in forest soils were evaluated in the first comprehensive survey of Great Britain, the BioSoil soil survey, using a total of 167 plots (72 in England, 26 in Wales and 69 in Scotland). The average C stock down to 80 cm depth for seven main soil types ranged between 108 and 448 t C/ha with maximum values from 511 to 927 t C/ha. Carbon stock varied with soil depth and type, forest type, and stand age. Stocks within the upper mineral soil (0–20 cm) represented between 29 and 69% of the total 0–80 cm C stock, while those in the top 40 cm comprised 59–100% of the total. Carbon stocks decreased in the order deep peats > peaty gleys > groundwater gleys > surface‐water gleys > podzols and ironpans > brown earths > rankers and rendzinas. Litter and fermentation horizons on average contributed an additional 7.3 and 8.8 t C/ha, respectively, to the overall soil C stock. Measured soil C stocks (0–80 cm) were upscaled by area of main soil and forest types to provide national estimates. Total forest soil stocks for England, Wales and Scotland were upscaled to 163, 46 and 337 Mt C, respectively, with an additional 17, 4 and 21 Mt C within surface organic layers (litter and fermentation horizons). Carbon stocks were larger under conifers compared with broadleaves. Peaty gleys contributed most to the total C stock in Scotland, while brown earths and podzolic soils made the largest contribution in Wales, and brown earths and surface‐water gley soils in England. Estimated total carbon stocks in forest soils in Great Britain, including organic layers, are 589 Mt C in the top 80 cm and 664 Mt C in the top 1 m of soil. The BioSoil soil survey provides the most comprehensive estimate of forest soil C stocks in Great Britain to date and provides a good baseline for assessing future change even though variability in forest soil C stocks is high. However, a relatively small number of additional plots to fill existing gaps in spatial coverage and to increase representation of rendzinas and highly organic soils would significantly reduce the level of uncertainty.