砾石覆盖对土壤水热过程及旱作小麦玉米产量的影响

为了揭示砾石覆盖对农田土壤水热变化及作物产量形成的影响,2013—2015年采用小区试验法研究冬小麦-夏玉米轮作条件下土壤水分变化、温度效应以及作物生长和产量之间的相互作用关系。田间试验设置无覆盖(CK)、25%砾石覆盖(GM1)、50%砾石覆盖(GM2)、75%砾石覆盖(GM3)和100%砾石覆盖(GM4)5个处理。结果表明:砾石覆盖度与土壤水分呈显著正相关,100%砾石覆盖处理土壤贮水量最高;干旱胁迫条件下砾石覆盖度越高土壤的保水性越好,降雨条件下砾石覆盖度越高土壤截留雨水的能力越大。砾石覆盖具有明显的增温效应,4个砾石覆盖处理的土壤平均温度大于CK处理,GM4处理土壤平均温度最大;砾石覆盖处理可以认为是一种有效的温度调节方式,具体表现在低温(-5~0℃)条件下GM4处理较CK处理土壤温度增加5℃,高温(40~45℃)条件下GM4处理较CK处理土壤温度降低3.7℃;在寒冷气候和水分亏缺的情况下4个砾石覆盖处理增温能力均大于对照。此外,夏玉米叶面积指数随着砾石覆盖度增加而增大。100%砾石覆盖处理的2季冬小麦和夏玉米平均产量较对照处理分别增加了58.55%和22.50%。可见,砾石覆盖技术可以有效保持土壤水分、增加土壤温度、促进作物生长和提高产量,是干旱半干旱地区应对水分胁迫和气候变化、     

MINERALOGY, GENESIS AND CLASSIFICATION OF FERRUGINOUS SOILS OF THE EASTERN MYSORE PLATEAU, INDIA

The relationship of geomorphic and climatic history and formation of the ferruginous soils, formed on the acidic Peninsular Gneiss, of the Mysore Plateau, India, is discussed. The profiles studied are found on two different land systems. The soils of the older, fairly smooth landscape are composed of colluvium over truncated laterite profiles, with a gravel layer and a prominent kaolin layer over the weathered rock. These soils show an accumulation of pedogenic haematite grains in the sand fraction and have considerable kaolinite and amorphous ferri-aluminosilicate minerals in the clays. The soils of the younger, rugged landscape have similar clay mineralogy, but do not have a gravel layer, or haematite grains. The influence of the coarse-grained parent rock is seen in the large amounts of quartz gravel. The absence of granulation is attributed to lack of accumulation of iron. The soils have been formed in an earlier, more humid climate than prevails today. The original laterite profiles were formed on a plane surface, and subsequent change in climate has led to change in the land forms and dissection. Truncation of the profiles was followed by deposition of red colluvium over the resistant ferruginous layer. These ancient soils do not fit the criteria for Oxisols in the U.S. classification, but fit well in the French system as ‘Sols Ferrallitiques’, subclass ‘fiablement désatures en (B)’. The soil from a low lying area, formed from colluvium under hydromorphic conditions. is classified as‘Vertisols et Paravertisols'.     

Influence of soil surface features and vegetation on runoff and erosion in the Western Sierra Madre (Durango,Northwest Mexico)

In mountainous areas, runoff and soil erosion are closely linked to soil surface features, particularly stoniness. Depending on the size of rock fragments (gravel, pebbles, stones and/or blocks) and especially the way they are integrated into the soil matrix, they may facilitate or hinder infiltration and promote soil losses. The present study examines the role of different soil surface features and their influence on runoff formation and on soil erosion in an area seriously affected by overgrazing.Based on measurements made on hillslopes for 2 years at the plot scale, the results show that grass cover, pebbles and sand content increase runoff and erosion. Inversely, slope value, tree cover percentage, structural stability and organic matter content are negatively correlated with runoff and soil losses.It is shown that the correlations can be explained by the major role played by the surface features on hydrologic behaviour of the hillslopes. Two main surface features were identified and hydraulically characterised, namely: (i) crusted surfaces with embedded gravel widespread on gentle slopes which induce high runoff and erosion rates; and (ii) stony surfaces, where free pebbles and blocks protect the top soil against raindrops and overland flow kinetic energy and lead to reduce runoff and soil losses.     

Effects of gravel on grassland soil carbon and nitrogen in the arid regions of the Tibetan Plateau

Many previous studies have focused on soil gravel concentrations and their effect on crop yields in agricultural systems. The extent of carbon and nitrogen sequestration in soils under steppe systems in relation to surface gravel mulch remains largely unexplored. This study investigated the effects of gravel mulches on soil organic carbon and total nitrogen stocks in the arid and windy regions of the Tibetan Plateau. Surface gravel mulches provide a more favorable environment for soil carbon and nitrogen stocks than do non-mulched sites. Soil organic carbon and total nitrogen stocks were highest (46.9 Mg ha^− 1 SOC and 2.8 Mg ha^− 1 TN) in the medium gravel mulch sites with ~ 40-50% gravel, and lowest (29.5 Mg ha^− 1 SOC and 1.4 Mg ha^− 1 TN) in no gravel mulch sites. Analysis of aggregate size fractions indicated that the vast majority of SOC was present in microaggregate fractions throughout the top 30 cm of soil. Considering the low level of soil disturbance in the study area, the carbon contained in the macroaggregate fraction might become stabilized in the soil. Gravel mulches above the soil surface have an important bearing on soil carbon sequestration as they control wind erosion, decrease soil surface evaporation and change soil physical behavior in the arid and semiarid regions.     

紫色土丘陵区坡耕地坡面侵蚀响应特征研究

采用人工模拟降雨法,分析了紫色土丘陵区坡耕地坡面侵蚀过程地表石砾化、土层厚度变化及影响因素,利用建立的流失土层厚度计算方程对重庆地区不同土地利用类型流失土层厚度进行了分析。研究表明:(1)在降雨前、3次降雨后、6次降雨后,小区地表石砾覆盖度分别为1.5%,2.4%和12.2%,地表石砾覆盖度与累积产沙量正相关,在相同产沙量条件下,后期降雨侵蚀产沙造成的石砾化程度更为显著;(2)在模拟降雨前期,随着降雨量增大坡面流失土层厚度增加很快,4场降雨后降雨量增大导致的流失土层厚度增长率减少;不同地形因子组合下,累积雨量与流失土层厚度间存在较好的线性关系;(3)重庆地区无措施裸露坡耕地年均流失土层厚度为4.479 mm,大于年均成土厚度,作物覆盖顺坡耕地、作物覆盖横坡耕地、植物篱坡耕地、作物覆盖水平梯地、林地和荒草地年均流失土层厚度分别为1.931,0.728,0.533,0.041,0.001,0.079 mm,均小于年均成土厚度;重庆地区流失土层厚度大小为:渝东南地区>渝中部区>渝东北区>主城区>渝西地区,研究可为重庆市水土保持分区防治提供理论指导。     

Lithologic controls of drainage density: A study of six small rural catchments in New England, N.S.W.

The term drainage density has been operationally defined by a number of parameters characterising both static and dynamic networks (eroded channel density, perennial flow occupance, flow net, wetted channel length). The present study examines the variation of flowing stream length on six catchments of contrasting granite and sedimentary lithologies.The basic influence of lithology is analysed at three scales: between catchments, within one network, and along specific channel sections. Flow length graphs demonstrate that the drainage density of flow is greater on sedimentary rocks and is associated with higher eroded channel densities. All basins displayed a wide range of flow net fluctuations which were highly related to rainfall increments. Phases of flow network evolution were traced for each basin during one large storm.On granite basins two other components of the wetted channel network were quantified and exhibited equally dynamic characteristics when compared to flow. These were linear changes of continuous stagnant water sections and saturated segments. Field observations of episodic flows on two contrasting lithologies indicate the variable influence of rock type in surface and subsurface runoff processes and the importance of relating channelled flows to stream channel morphology.     

荒地不同压砂年限对土壤微生物区系、酶活性与土壤理化性状的影响

以宁夏中卫市香山地区荒地压砂3,8,15,25 a和邻近未压砂(对照)的土壤为研究对象,研究了压砂对土壤微生物区系、酶活性和土壤理化性状的影响.结果表明,与对照相比,压砂后微生物总数减少;土壤脲酶活性随着压砂年限的延长呈下降趋势;前15 a压砂地土壤有机碳、全氮、碱解氮和速效钾随着压砂年限的延长呈下降趋势;压砂地土壤含水量高于对照;压砂地全盐含量远远低于对照;说明荒地压砂种植能蓄水保墒,防止土壤次生盐碱化,但连续种植肥力下降,微生物量减少.     

太阳能集热器的热流气体对砾石的蓄放热特性研究

太阳能的蓄放热特性的研究对清洁能源太阳能的开发和利用具有重要意义。该文利用冬季太阳能集热器的热流气体,对砾石的蓄放热特性进行了研究。以居民居住的标准房间（4 m×2.7 m）为依据进行了模拟;利用太阳能集热器的热能与直径为50～100 mm的砾石铺设成150 mm厚度的地下蓄热系统进行蓄热和放热试验,研究昼夜之间室内砾石的蓄热和放热特性;通过测试太阳能集热器的内部温度、砾石层内部及室内地表面的温度,研究了太阳能集热器的蓄热效率和转换效率,同时分析了蓄热层及室内地表面的热传递特性;为进一步开拓针对冬季寒冷地区太阳能蓄热型居民建筑物内部热环境方面的基础研究提供了科学的依据。     

Structural analysis and mechanical origins of gilgai at Boorook,Victoria, Australia

Gilgai microrelief at an undisturbed site is described. Surface and subsurface structural patterns in a duplex soil (solodic planosol) are analysed using principles and techniques adapted from structural geology. The microrelief is situated on a gently dipping regional slope and some mounds show evidence of surface erosion. Large cracks on the ground surface have an orientational relationship with the strike and dip of the regional slope. Some of the surface cracks may post-date the original time of gilgai formation. Beneath the microrelief surface a lenticular gravel layer of sedimentary origin is folded into a series of anticlines and synclines. Compositional layers also have fold-like geometries. Two-dimensional crack pattern analysis on a vertical section through several mounds, revealed upwards fan-like and concentric-convex patterns, where upwards movement had occurred. Three-dimensional measurements were made on monoliths and on an undisturbed block sample. The mean slickensided shear plane dip below a mound is 43° (standard deviation 9°). There is a statistical decrease in shear plane dip with depth, which is in partial agreement with soil mechanics theory. Shear planes are distributed from 0.3 m below ground surface down to a projected limit of 1.3 m to 1.8 m which is shallower than the limits reported for slickensided cracks in non-gilgai soils of Israel. The mechanism proposed to explain the surface and subsurface structures involves moisture concentrations that focus near, and below pre-gilgai surface cracks and a gravel lens. The moisture interacts with a swelling component and a triaxial state of stress is achieved. Differences between lateral and vertical stresses due to swelling pressures and overburden loads are sufficient to cause small, inclined shear displacements in definable depth zones. Accumulations of vertical movement components arising from the shear displacements, and vertical sliding of blocky non-sheared units nearer the ground surface, cause the gilgai microrelief and fold-like deformations in the soil profile. Zones of possible downward movement are located at the margins of mounds. Mechanical models proposed in the past are assessed in the light of the Boorook findings. Some proposals appear to be mechanically unlikely for the Boorook gilgai.     

北方风沙区砾石对堆积体坡面径流及侵蚀特征的影响

为了研究砾石对工程堆积体降雨侵蚀规律的影响,采用室内人工模拟试验,以土质堆积体(砾石质量分数为0)为对照,研究了10%、20%和30%砾石质量分数堆积体边坡在模拟降雨条件下的径流水力特征、产沙过程及侵蚀动力机制。结果表明:1)产流0~6 min,砾石促进堆积体坡面细沟间径流流动;产流12~30 min后,砾石阻碍堆积体坡面细沟径流流动;2)含砾石堆积体坡面粗糙度增大,水流流态变缓,水流速度降低,且均以层流为主。较土质堆积体而言,30%砾石质量分数堆积体坡面阻力系数增大88.8%~288.4%,弗汝德数降低28.9%~41.8%,水流速度降低0~45.8%;3)径流含沙量随产流历时经历快速降低-平稳过渡-波动上升3个阶段,土质及10%砾石质量分数堆积体高含沙水流现象频发,且随雨强增大,重力坍塌次数增加,重力侵蚀程度增强。20%、30%砾石质量分数堆积体发生高含沙水流的几率约为0。相对土壤流失比与砾石质量分数呈极显著负指数函数关系;4)土壤剥蚀率与各侵蚀动力参数均可用简单线性函数关系描述,单位径流功率是描述风沙区土质和10%砾石质量分数工程堆积体侵蚀产沙的最优因子,径流功率是刻画20%、30%砾石质量分数工程堆积体土壤侵蚀参数更为合理的因子。结果可为全国范围工程堆积体土壤侵蚀模型的建立提供科学依据。     

Stability of an upland gravel-bed stream, Swinhope Burn, Northern England

Some upland gravel-bed streams often undergo frequent channel change in response to floods and changes in sediment supply. However, in others, where local conditions permit, long-term channel planform stability can be observed. This paper uses evidence from Swinhope Burn in upper Weardale, Northern England, to demonstrate relative channel stability over a 180-year period.Channel planform change is identified using seven historical maps and air photographs dating from 1815 to 1991. The 1.4-km study reach has retained a stable meandering pattern over a period of 180 years, with a temporary but dramatic change to a straight, low sinuosity, partly divided channel, at some point between 1815 and 1856 (identifiable on the 1844 Tithe Map). Channel planform stability, observed over the historic period, is related in part to the low channel gradient upstream of a cross-valley moraine situated at the lower end of the study reach. This moraine has led to partial closure of the valley system and the development of a small upstream floodplain or ‘sedimentation zone’ (average width of 150 m). The resulting low channel gradient (0.012) inhibits coarse bedload transport and encourages overbank sedimentation. Cohesive banks promote lateral channel stability and the wide floodplain reduces potential coupling between the channel and valley-side slope sediment sources.The probable cause of the observed channel planform change is the combination of a succession of four major floods in the River Wear catchment during the 1820s, and episodic inputs of sediment generated by upstream metal mining between 1823 and 1846. Large floods in the past 40 years have produced very little evidence of lasting channel change. However, locally a channel avulsion has been documented following a flood in February 1997. This represents a useful modern analogue for previous mechanisms of channel change.     

Aggradation and dissection sequences on Spanish alluvial fans: Influence on morphological development

Similarities in Quaternary alluvial fan development are identified throughout southeast Spain. Pre-Wurm aggradation phases culminate in calcrete crusted upper fan surfaces, which are followed by Wurm dissection phases producing deep fanhead or through trenches. Deposits of the aggradation phases reflect source area size, relief and geology and in addition to proximal/distal facies variations show vertical decreases in debris flow and increases in gravel deposition. The dissection phases were complicated by cut and fill sequences forming within-trench terraces which show a southward decrease in complexity. The sequences are expressed in progressive changes in fan, terrace, and channel slopes and intersection point location. Fan morphological development during the Quaternary reflects long term progressive change, complicated by short term responses to climatic fluctuations and further comolicated by the locally variable effectiveness of trenching thresholds.     

Aggradation and dissection sequences on spanish alluvial fans: Influence on morphological development

Similarities in Quaternary alluvial fan development are identified throughout southeast Spain. Pre-Wurm aggradation phases culminate in calcrete crusted upper fan surfaces, which are followed by Wurm dissection phases producing deep fanhead or through trenches. Deposits of the aggradation phases reflect source area size, relief and geology and in addition to proximal/distal facies variations show vertical decreases in debris flow and increases in gravel deposition. The dissection phases were complicated by cut and fill sequences forming within-trench terraces which show a southward decrease in complexity. The sequences are expressed in progressive changes in fan, terrace, and channel slopes and intersection point location. Fan morphological development during the Quaternary reflects long term progressive change, complicated by short term responses to climatic fluctuations and further comolicated by the locally variable effectiveness of trenching thresholds.     

Evidence for transport of bedload in waves: Analysis of fluvial sediment samples in a small upland stream channel

Data pertaining to the transport of fluvial sediment sampled in detail during a five hour long event in a small upland stream channel in the extremely arid Southern Negev are presented. Considerations based on comparative evaluations of water discharge, stream power, total and fractional sediment concentration, and total and fractional sediment discharge suggest that bedload transport in channels of even very small upland catchments practically devoid of continuous alluvial cover takes place in waves, which are not a priori related to any water discharge characteristic, but rather reflect some intrinsic feature of watershed dynamics, such as slope-channel topographic contrasts or fluvial bifurcation. The regular spacing of pools and riffles and of gravel bars in the more alluvial reaches downstream may therefore be initiated from upstream.     

THE ADSORPTION OF POLYVINYL ALCOHOL ON GIBBSITE AND GOETHITE

The neutral polymer, polyvinyl alcohol, has been shown to be adsorbed by the hydrated oxides gibbsite and goethite. A reduction in adsorption on gibbsite is observed when it is dried prior to the adsorption measurements. Evidence from electron microscopy suggests that this is caused by a reduction in the accessible surface area due to aggregate formation, rather than a change in the surface properties of the substrate. Changes in either the pH or the ionic strength of the medium do not significantly alter the amount of PVA adsorbed. Electrophoretic data indicate that the thickness of the adsorbed layer on both clays and oxides is in excess of 10 nm at high concentrations of polymer.     

Rock fragments I. Their effect on runoff, erosion and soil properties under field conditions

Abstract. The effects of different sizes, amounts, and positions of rock fragments on soil properties and erosion were studied in experimental plots (10 treatments including bare soils and soils under natural vegetation, with 3 replicates each) installed on a hillslope.
Over five events, the largest amounts of runoff were from bare soils containing abundant rock fragments, either partially embedded on the surface or incorporated in the upper part of the soil. Stoneless soils gave smaller amounts, and the smallest runoffs were measured on soils under natural vegetation. Generally, large rock fragments (cobbles) caused greater runoff than smaller fragments (coarse gravel). However, soils with appreciable amounts of coarse gravel on the surface generated considerable runoff under rainfalls of low intensity and long duration, but smaller amounts at greater rainfall intensities.
Sediment loss was greater from soils with cobbles than from soils containing coarse gravel; vegetation greatly decreased sediment loss from both.
In a 12-month period, the organic matter content of the soils decreased by 15.5 to 23.0%, decreasing soil aggregate stability. The organic matter content was greater in the collected sediments than in the soil.     

Potential future effects of current levels of sulfur deposition on stream chemistry in the southern blue ridge mountains,U.S.

Using newly available regional data sets we examine the potential for future changes in stream acid neutralizing capacity (ANC) for the Southern Blue Ridge Province (SBRP) of the U.S. as related to (1) levels of S deposition, (2) retention of S within watersheds, (3) current surface water SO₄, and (4) potential historical changes in surface water chemistry. We conclude that, although (1) little change in surface water chemistry (as affected by acidic deposition) likely has occurred in the region to date, and (2) soils are currently retaining a majority of atmospherically deposited S, it is likely that marked increases in surface water SO₄ will occur. Such increases could be accompanied by significant surface water acidification (loss of ANC).     

砂石覆盖粒径对土壤蒸发的影响

为研究不同粒径砂石覆盖对土壤蒸发过程的影响,进行模拟试验.试验以砂石粒径大小为因子,设3个粒径水平:0.5,2.5,4.5 cm,以裸土为对照.结果表明:地面砂石覆盖能够有效抑制土壤蒸发,在土壤含水率较高的阶段,抑制作用更加明显;砂石覆盖对蒸发的抑制作用与砂石粒径密切相关,在相同的覆盖厚度(5 cm)和同一含水率条件下,砂石覆盖的粒径越大,对蒸发的抑制能力越低;砂石覆盖能明显改变土壤蒸发过程,覆盖条件下的土壤蒸发与裸土相比不仅降低而且更加平稳;在41d的连续蒸发过程中,覆盖条件下的累计土壤蒸发量与时间呈近似线性关系,而裸土为对数关系.     

基于多时相遥感影像分析的城市土地利用/覆盖变化与热环境演变--以徐州市为例

以1987,1994,2000和2005年共4期的Landsat TM遥感影像为数据源,利用先进的决策树分类法获取徐州市土地利用/覆盖信息,通过单通道算法反演地表亮温获取城市热场分布与热环境变化信息,采用土壤调节植被指数SAVI定量描述研究区植被覆盖变化,并综合采用这些信息对城市热环境演变与城市扩展、植被覆盖变化的关系进行了综合分析.结果表明,利用Landsat TM数据结合决策树分类方法,是获取土地覆盖/利用的有效方法.通过计算地表辐射亮温来研究城市热环境变化是合适的,SAVI等因子与城市热环境显著相关,能够有效地定量描述城市扩展及其生态环境响应.研究结果可服务于城市环境保护与人居环境改善.     

塔里木盆地荒漠类型及其抗风蚀特征初探

塔里木盆地的荒漠面积达到 5 2 .1× 10 6 hm2 ,按物质组成、地表景观和形成 ,荒漠可划分为盐漠、泥漠、砾漠和沙漠 4种类型。从不同荒漠类型剖面结构特点看 ,盐漠表层有盐结皮或盐结壳 ,泥漠则板结而坚硬 ,砾漠在地表有砾幕 ,它们都有一定抗风蚀的能力。沙漠中的沙丘组成物质以细沙为主 ,无特殊抗风蚀层次。尽管塔里木盆地的一些荒漠类型有一定抗风蚀的结构特点 ,加强荒漠区域的生态保护仍是非常重要。