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1.
The role of climate and vegetation in weathering and clay mineral formation in late Quaternary soils of the Swiss and Italian Alps 总被引：2，自引：0，他引：2
Interactions between climate and soil remain ambiguous, particularly when silicate weathering and clay mineral formation and transformation rates are considered in relation to global climate changes. Recent studies suggest that climate affects weathering rates much less than previously thought. Here we show that the climate in the central European Alps has a significant, but indirect, influence on the weathering of soils through vegetation. The pattern of element leaching and mineral transformations is not only due to precipitation and temperature. Element leaching was greatest in subalpine forests near the timberline; weathering is lessened at higher and lower altitudes. Vegetation, therefore, contributes significantly to weathering processes. The highest accumulation of organic matter was found in climatically cooler sites (subalpine range) where the production of organic ligands, which enhance weathering, is greatest. Patterns of smectite formation and distribution had strong similarities to that of the elemental losses of Fe and Al (R = 0.69; P < 0.01) or base cations (R = 0.58; P < 0.05). Higher precipitation rates and the production of organic chelating compounds in the soil promoted the appearance of smectites. The relationship between climate, element leaching (Fe, Al, Ca, Mg, K, Na), and smectite formation is strongly nonlinear and driven by the podzolisation process, which is more pronounced near the timberline because of the bioclimatic constellation. Climate warming will probably, in the future, lead to a decrease in SOM stocks in the subalpine to alpine range because of more favourable conditions for biodegradation that would also affect weathering processes. 相似文献
2.
Soils at well-drained sites near Kongsfjorden, Spitsbergen, are described in terms of morphology as well as solid and solution phase chemistry. Decarbonation is the dominant soil process and results in high Mg and Ca concentrations in soil solutions, in negative enrichment of Fe, Al, and non-carbonate clasts in near-surface horizons, and in the accumulation of dolomitic silt horizons at depth. Coatings of reprecipitated carbonates extend into the C horizon. Several developmental pathways are suggested for well-drained carbonate soils at Kongsfjorden. In vegetation-rich areas, with calcite-rich parent material, relatively rapid (∼ 10, 000 years) carbonate dissolution precedes silicate mineral weathering. In areas of Polar Desert climate and dolomitic parent material, decarbonation is slower and the continued accumulation of dolomite silt may eventually transform the soil system to a periglacial one. 相似文献
3.
土壤铁锰结核中生命有关元素的化学地理特征 总被引：11，自引：1，他引：11
研究了我国亚热带、暖温带几种土壤铁锰结核中锰矿物的类型,探讨了它们形成的地球化学过程与特征。结果表明:不同土壤铁锰结核锰矿物的类型及其含量不尽相同,但锂硬锰矿普遍存在且结晶程度较高;与土壤相比,土壤铁锰结核的化学组成仍以Si、Al、Fe为主,但Fe含量超过了Al,Mn含量远大于Mg、Ca;结核中一些重金属富集顺序为Pb>Co>Ni>Cu>Zn>Cr;揭示了土壤铁锰结核形成过程中存在着成核富集作用、成矿作用、专性吸附作用和轻度积钙作用。 相似文献
4.
为了量化川西高寒山地土壤与铁、铝矿物相关的有机碳含量以及探讨川西高寒山地土壤铁、铝矿物对有机碳稳定性和累积方式的影响,采用选择性提取法研究了川西高寒山地的山地灰化土（MP)和高山草甸土（AM）中土壤有机碳与晶质金属氧化物（DH）提取、短程有序（HH）提取、矿物复合体以及有机—金属配合物（PP）提取中的有机碳和铁、铝的分布。结果表明,MP中DH,HH和PP提取的碳含量分别为(10.91±6.23) g/kg、(5.92±1.66) g/kg和(8.76±2.29) g/kg,分别占有机碳的20.92%,12.07%和19.93%;而AM中DH、HH和PP提取的碳含量分别为(9.05±1.33) g/kg、(5.52±1.02) g/kg和(9.12±3.21) g/kg,分别占有机碳的21.04%、12.47%和19.34%。3种提取剂提取的碳含量以及其占有机碳的百分比在MP和AW的A层土壤中均表现为PP > DH > HH,而在B层土壤中则表现为DH > PP ≈ HH。随着土壤深度的增加,深层土壤中次级矿物和晶体矿物丰度的显著增加,导致有机碳与铁、铝矿物复合体由有机—金属配合物主导转变为有机碳与晶质金属氧化物形成的复合体主导。PP提取的碳和其所占有机碳的百分比表现为A层高于B层,而DH和HH提取的碳含量和其所占有机碳的百分比大体表现为A层低于B层。由于MP特殊的土壤性质,这种差异在MP中更为明显。3种提取剂提取的金属（Al+Fe）含量在两种土壤中均表现为DH > HH > PP。而其提取的碳与金属的摩尔比表现为DH < HH < PP,说明随着铁、铝矿物的结晶度增加,其与有机质的作用从共沉淀、络合而向吸附作用转变。DH,HH和PP提取的碳与SOC的相关分析表明,MP中土壤有机碳的累积在一定程度上受晶质铁、铝矿物与有机质的相互作用而驱动;AM中土壤有机碳的累积在一定程度上受短程有序矿物与有机质的相互作用以及有机—金属配合物的驱动。本文研究表明,土壤中的铁、铝矿物与有机碳形成的复合体在一定程度上驱动着川西高寒山地土壤有机碳的积累,不同土壤类型中,与矿物相关的有机碳的分布不同,其有机碳的积累方式也不同。 相似文献
5.
在野外考察采样的基础上,对泥河湾盆地马圈沟剖面更新世河湖相沉积序列进行了XRD矿物组分和磁性矿物分析。研究发现,剖面沉积矿物主要由碎屑矿物和碳酸盐矿物组成,碎屑矿物主要为石英、钠长石、白云母和斜绿泥石,其平均含量分别为38.77%、17.16%、29.63%和4.11%,是剖面沉积矿物组成主体,且各矿物之间基本没有相关性;相对于碎屑矿物,碳酸盐矿物在整个剖面中含量较低,主要为方解石和白云石,其平均含量分别为4.72%、3.59%,文石在剖面中零星出现。对剖面典型样品进行热磁分析,确定了沉积物中磁性矿物的种类以及加热过程中的变化和产物,并对其来源进行了探讨。同时发现,含绿泥石较高的灰绿色粉砂样品加热后磁化率的升幅比灰黄色样品高,而绿泥石的相对含量与该地区化学风化密切相关,进一步说明κ-T曲线的变化特征可以用来反应盆地化学风化作用强度的变化,具有重要的古环境意义。 相似文献
6.
Stephen A. Norton Randall H. Perry Jasmine E. Saros George L. JacobsonJr. Ivan J. Fernandez Jiří Kopáček Tiffany A. Wilson Michael D. SanClements 《Journal of Paleolimnology》2011,46(1):107-122
The sediment record from a 5.3-m core from Sargent Mountain Pond, Maine USA indicates strong co-evolutionary relationships
among climate, vegetation, soil development, runoff chemistry, lake processes, diatom community, and water and sediment chemistry.
Early post-glacial time (16,600–12,500 Cal Yr BP) was dominated by deposition of mineral-rich sediment, low in organic matter
and secondary hydroxides of Al and Fe; pollen indicate tundra conditions; diatom taxa indicate pH between 7.5 and 8, and total
P concentrations of about 25 μg L−1, favoring higher productivity. Chemical weathering was rapid, with high alkalinity, pH, Ca, and P in runoff. As climate ameliorated,
about 12,500 Cal Yr BP, forest vegetation became established; soils would have developed vertical zonation, including organic
matter accumulation, and incipient podzolic horizons, with accumulating secondary hydroxides of Al and Fe that sequestered
P in the soils. Labile minerals (primarily apatite, Ca5(PO4)3(OH,F,Cl)) became depleted in the soil, further reducing the supply of P to the lake. Dissolved organic carbon (DOC) from
soil organic matter mobilized Al and Fe to the lake where Al(OH)3 (primarily) and Fe(OH)3 (minor) were precipitated. The sedimenting hydroxides adsorbed P from the water column, further reducing bioavailable P.
These long-term trends of moderating climate, and changing terrestrial biology, soils, and aquatic chemistry and phytoplankton
were interrupted by the 1,000-year long Younger Dryas cooling, which led to a temporary reversal of these processes, a period
that ended with the major onset of Holocene warming. The sequestration of P by soils would have strengthened because of long-term
soil acidification and pedogenesis. The lake was transformed from a more productive, high P, high pH, low DOC system into
an oligotrophic, relatively low P, acidic, humic lake over a period of 16,600 years, a natural trend that continues. In contrast
to many human-affected lakes that become increasingly eutrophic, many lakes become more oligotrophic during their history.
The precursors for that are: (1) absence of human land-use in watersheds, (2) bedrock lithology and soil with a paucity of
soluble Ca-rich minerals, and (3) vegetation that promotes the accumulation of soil organic matter, podzolization, and increased
export of metal-DOC complexes, particularly Al. 相似文献
7.
《自然地理学》2013,34(5):407-422
High-intensity forest fires can degrade, collapse, or completely destroy clay minerals in soils, with signatures of these changes remaining for years after the burns. To ascertain immediate impacts of high-intensity fire on soil clay minerals and mineral recovery over time, soil from the 2002 Hayman, Colorado, fire was analyzed by X-ray diffraction. Sample locations included burned soil from within the perimeter of the fire, unburned soil near the origin, and soil from adjacent historic burns. The unburned soils contain mixtures of illite, mixed-layer illite/smectite and illite/vermiculite, kaolin, and mixed-layer chlorite. Surface soils (surface-7.7 cm) contain illite, mixed-layer illite/smectite, and kaolin. Sub-surface soils (7.7-13.0 cm) contain mixed-layer illite/vermiculite, in addition to the same minerals found at the surface. Deep soils (13.0-27.0 cm) show disappearance of mixed-layer illite/smectite and illite/vermiculite and show evidence of the presence of mixed-layer chlorite. Comparisons between recently and historically burned soils and unburned soils showed slight trends in alterations of clay mineral structures in the surface soil, including alteration of the 001 illite peak, the 001 kaolin peak, and a decrease in the swelling component of mixed-layer illite/smectite. These trends indicate fire impacts the structure of soil clay minerals. 相似文献
8.
Recent Environmental Change and Human Impact on Svalbard: The Lake-Sediment Geochemical Record 总被引：1，自引：1，他引：1
As part of a broader investigation into recent environmental change on Svalbard, the inorganic geochemical record of six lake-sediment cores was analysed. The major temporal trends in sediment elemental composition are driven by variations in two contrasting sediment components, both derived from catchment soils: (1) mineral matter, and (2) soil organic matter (SOM), enriched in Fe and Mn oxides and heavy metals. Two environmental impacts are recorded in most or all of the lake sediment sequences. An up-core increase in organic matter can be partly attributed to diagenetic effects, but also requires an enhanced supply of SOM relative to mineral matter. In addition, the central and southern sites all show a ca. 1970 event characterised by an enhanced mineral matter accumulation rate. This requires either an enhanced allochthonous supply or an enhanced mobilisation of littoral sediments. In either case a regional-scale driving force, such as a shift in climate, is required. At five of the lakes the sediment heavy metal concentration profiles can be explained entirely by natural factors. However, at Tenndammen (U), situated close to the Svalbard’s largest settlement at Longyearbyen, possible anthropogenic Pb enrichment is found. Comparison of observed and expected heavy metal profiles (based on Greenland ice-core data) shows that the lakes are generally too insensitive to have recorded a long-transported heavy metal pollution signal. 相似文献
9.
Kumtagh Desert is one of the eight biggest deserts in China, but poorly investigated before our interdisciplinary study because of the difficulty of access. In this paper, 33 representative surface sediment samples were collected from the Kumtagh Desert and analyzed in the laboratory to obtain heavy mineral components and geochemical element contents. Results show that various kinds of heavy minerals are present in these samples, with high levels of epidote and hornblende. Si and Al take up a large part of chemical composition. Compared with the average composition of geochemical elements of the upper continental crust (UCC), except Si and Ca, all elements are depleted to a certain degree; Fe, Mg, Ca, P, Ti and Mn have high correlation coefficients in their contents. The mineral and geochemical composition of the Kumtagh Desert sediments have a similarity with that of rocks of Altyn Tagh Mountains, and the surface sediments of the alluvial/diluvial fans around the Altyn Tagh Mountains and that of the Taklamakan Desert, indicating that one major source of the Kumtagh Desert sediments is located in the Altyn Tagh Mountains. Alluvial deposits and lake sediments in Aqik valley and lower reaches of Shule River are prone to be eroded and transported by the strong northeasterly wind into the Kumtagh Desert, forming another source of the desert deposits. An A-CN-K ternary diagram shows that a weak degree chemical weathering by the loss of Na and K occurred in these sediments, whereas A-CNK-FM ternary diagram suggests that Fe and Mg have undergone a significant chemical differentiation. Physical weathering processes cause easy erosion and enrichment in fine particles for mafic minerals, thus coarse desert sand particles can be relatively depleted in Fe and Mg. The mineral and geochemical composition of sediments in arid regions experiencing less chemical weathering are mostly affected by physical weathering. 相似文献
10.
暴雨对土壤组成和性质的影响——以河南省泌阳暴雨中心区为例 总被引：1，自引：0，他引：1
本文以河南省泌阳暴雨中心区为例 ,在野外土壤调查和室内理化分析的基础上 ,分析讨论了暴雨对土壤组成和性质的影响。结果表明 ,暴雨中心区土壤因长期的暴雨冲刷 ,土层浅薄 ,发生层数目少 ,土体构型简单 ;砾石含量高 ,物理性粘粒含量低 ,质地类型多属多砾质砂土 ;土体中不出现肉眼可辨的铁锰结核 ;土壤淋溶作用强烈 ,呈微酸性反应 ;土壤有机质和速效氮含量较高 ,而速效钾含量偏低 ,有机质表聚化现象不明显 ;盐基淋溶率小于 1 0 0 ,土体SiO2 /R2 O3小于 7 0 0 ,脱硅和富铁铝化作用明显 ,土体风化程度较高。对暴雨中心区附近的土壤来说 ,上述土壤组成和性质均出现明显的差异。 相似文献
11.
《Geomorphology》2007,83(1-2):121-135
This paper presents ALLOGEN, a process model of soil mineral chemical weathering. Though designed principally to aid interpretation of lake sediment geochemical records by providing mass balance constraints for competing interpretations, the model is also applicable to more general questions about long-term weathering and soil development. The model is constructed around a generalised version of the mineral-weathering submodel of PROFILE, modified to minimise the need for site-specific data and to optimise performance for long-term change. Comparison with observed weathering rate data (river flux studies, chronosequences and lake sediment chemical stratigraphy) suggests that soil mineral depletion can be usefully simulated over timescales applicable to Quaternary and Holocene studies. To illustrate this, the plausibility of a weathering interpretation is demonstrated for sediment records at Lake Hope Simpson and Moraine Lake and the lake chronosequence at Glacier Bay. While long-term soil mineral depletion appears predictable, reliable simulation of past runoff quality is hampered by lack of a suitable long-term model for soil carbon. 相似文献
12.
以X射线衍射分析,研究了长江上游山地土壤的粘土矿物组成。根据土壤粘土矿物组成分类,划分了粘土矿物地带。采用土壤结构恢复试验,比较了不同粘土矿物组成土壤的结构形成特征。 相似文献
13.
Sedimentary cores BDP 96 and 98 and VER 96-2 St. 3 from Academician Ridge in Lake Baikal were investigated to investigate the effect of climatic fluctuations on rock weathering and clay formation in the Baikal drainage basin. Illite, smectite, vermiculite, and kaolinite were identified as the major clay minerals in the sediments by X-ray diffraction analysis. Biotite in gravels in alluvial soils of the Baikal drainage area weathers through illite to vermiculite, smectite, and finally to kaolinite. To investigate the relationship between weathering and climate, we measured the clay content and the concentration of biogenic silica in the sediments. High surface productivity (increased biogenic silica) and high chemical weathering (decreased clay content) occurred simultaneously, showing that crustal weathering and soil formation were enhanced under warm climatic conditions.Clay formation was enhanced in the watershed from the Late Miocene to the Middle Pliocene, and mechanical weathering of rocks increased during glacial intervals after the climate began to cool in Late Pliocene time. This change in the weathering mode in the watershed reduced the nutrient flux and aquatic productivity of Lake Baikal. 相似文献
14.
Late Glacial and Neoglacial (Little Ice Age) deposits on the Humboldt Massif were analyzed for relative-age dating parameters, including geomorphic and weathering characteristics, geochemical and soil properties. The soil chronosequence, formed in chemically uniform parent materials, provides an important database to study soil evolution in a tropical alpine environment. Extractable and total Fe and Al concentrations, examined to assess their use in relative-age determination, and as paleoenvironmental indicators, provide an important measure of the accumulation and downward profile movement over time of organically-bound Al, ferrihydrite and other crystalline forms (hematite and goethite) of extractable Fe. Ferrihydrite is particularly useful in determining former perched water levels in soils with relation to paleoclimate. The ratios of most Fe extracts are time dependent. The Fed/Fet ratio, within statistical limits, shows a slow increase from LIA (Little Ice Age) to Late Glacial soils, which closely correlates with other alpine soil studies in the middle latitudes and other tropical alpine locales. Values of Ald (dithionite) and Alo (oxalate extractable) generally do not correlate with time; however, Alp (pyrophosphate extractable) measured against Alt (total) provides insight on the downward translocation over time of organically-bound Al. Low leaching rates in this chronosequence are further supported by clay mineralogy trends and the geochemical data. 相似文献
15.
We investigated impacts of biocontrol of Tamarix spp. by Diorhabda carinulata on soil nitrogen (N) transformations by surveying organic and mineral soils from three sites. Potential net N mineralization was assayed using laboratory incubations. Results partially supported our hypothesis that herbivory would result in stimulated net N mineralization rates after one year of herbivory exposure, and did not support our hypothesis that herbivory would result in a sustained increase in rates after several years of exposure. Short-term effects differed by site, likely influenced by differences in prevailing soil N status, with net mineralization stimulated at a low fertility site but not at a high fertility site. In the longer-term, there was no impact on overall net N mineralization rates, even though there was a trend towards greater N immobilization in mineral soil. This may result from declining organic matter inputs to soil due to progressive growth limitations from herbivore-induced stress. Results suggest soil N availability will increase in the short-term and eventually decrease in the longer-term at low fertility sites, while soil N availability will not be impacted by herbivory at high fertility sites. Widespread management implications will require further research at sites spanning a range of edaphic characteristics. 相似文献
16.
Magnetic susceptibility of soil: an evaluation of conflicting theories using a national data set 总被引：5，自引：0，他引：5
J. A. Dealing K. L. Hay S. M. J. Baban A. S. Huddleston E. M. H. Wellington P. J. Loveland 《Geophysical Journal International》1996,127(3):728-734
Magnetic susceptibility values for topsoils across England arc combined with data for soil type, geochemistry and concentrations of magnetotactic bacteria in order to evaluate different theories for explaining soil magnetism. Strongly magnetic soils in unpolluted areas are found over weakly magnetic substrates and are dominated by ultrafine superparamagnetic grains. Magnetotactic bacteria are present in insufficient concentrations to account for strongly magnetic soils, and crop burning is discounted as a major factor. A small number of samples show high values associated with either airborne magnetic particulates from pollution or residual primary ferrimagnetic minerals from igneous substrates. The results are used to construct a new mechanism for the formation of secondary ferrimagnetic minerals that links abiological weathering and biological fermentation processes. The fundamental driving force in the mechanism is Fe supply, which may be linked to climate. Observed causative associations between climate and the magnetic susceptibility of loess-palaeosol sequences are supported by the findings. 相似文献
17.
Due to high temporal variation of soil organic matter in arid regions, estimates of annual sequestered C might be overestimate. We assessed the soil stable organic matter (humic substances) in the transitional area between Dry Chaco and Monte eco-regions in western Argentina, as an approach to estimate realistic soil C sink. Soil samples were taken during wet and dry seasons in four sites along precipitation gradient. In each site three soil cover situations (under tree, under shrubs and on bare soils) were sampled (n = 5) and the quantity and type of residues (tree and shrub leaves, woody material, grasses and forbs) were recorded. Soil organic matter and humic substances (humic and fulvic acids) content were analyzed and non-humic substances were calculated by the differences between organic matter and humic substances. Soil humic substance proportion respect to SOM was low (20%) in all sites and it did not correspond with the precipitation gradient. Non-humic substances were lower in wet season indicating high C lability. The most important factors that affected soil humic substance content were the type and quantity of organic residues and soil cover type. Our results suggest that previous C sink estimations in Argentina dry forest probably are overestimated. 相似文献
18.
Robert G. Darmody & Colin E. Thorn 《Geografiska Annaler: Series A, Physical Geography》1997,79(4):215-222
Chemical weathering and associated soil development trends on glacial forelands are commonly assumed to exhibit increases with time elapsed since glaciation. However, this gross trend is complicated by several other factors including elevation, aspect, and microtopography. This paper demonstrates that on the glacial foreland at Storbreen, Jotunheimen, Norway, chemical weathering and associated soil development trends show significant elevational influences. We sampled soils at shallow depths (0–1, 1–5, and 15–20 cm) at two sites on a moraine dated to 1750 at its elevational extremes of 1155 m (site L) and 1385 m (site H). The two moraine sites also differed developmentally from an adjacent 9000-year-old surface (site T) at an intermediate elevation, 1205 m. Analyses were conducted on the fine-earth fractions. Extractable elemental composition exhibited detectable differences between the same-age soils at different elevations with the lower site L tending to have measured parameters intermediate between the high site H and the older site T. Weathering, as indicated by mineralogy, was more pronounced at the 9000-year-old site T and least evident at the high elevation site H. In addition, elevation under the conditions of the field research may inhibit pedogenesis as indicated by the chemical data. Site H, for example, showed little variation with depth and had in general, less organic matter accumulation, smaller C:N ratio, greater pH, and lesser amounts of the measured extractable elements than the soil at site L. Site T generally had smaller pH and larger levels of the measured elements than the other sites. It was concluded that elevation has a significant control on weathering and pedogenesis that may mask the effects of age in this cold and wet environment. 相似文献
19.
长江口盐沼土壤有机质更新特征的滩面趋势 总被引：9，自引：0，他引：9
通过对长江口崇明东滩高潮滩、中潮滩以及光滩柱状样的有机元素(C、N)含量与碳稳定同位素组成(δ13C)、粒度组成等的测定,研究盐沼土壤有机质更新特征及其滩面趋势.结果表明,长江口盐沼土壤POC-δ13C相关特征与山地土壤剖面上部土层的基本类似,盐沼土壤有机质主要源于长江流域表层土壤,有机质年龄不足100年.不同高程柱样TN-C/N、POC-TIC与POC-δ13C关系特征表明盐沼土壤有机质更新程度普遍较低,有机质更新特征呈明显的滩面变化趋势.光滩有机质基本反映沉积母质特征,更新程度极低;中、高潮滩有机质更新作用已经发生,随着滩面演变,处于不同更新阶段的有机质组分混杂程度提高.盐沼滩面过程塑造垂向沉积层序,层序中独特的沙、泥纹层构造导致物质上下运移困难,有机质更新作用受到抑制.盐沼滩面过程直接影响有机质的累积与更新,对于有机质更新的时空特征具有显著制约. 相似文献
20.
黑河中游临泽绿洲农田土壤有机质时空变化特征 总被引：6，自引：0，他引：6
土壤有机质是表征土壤质量的一个重要指标,持续稳定的有机质含量是土壤维持生产能力的基础。土壤有机质的动态演变可以表征土地利用和管理水平。结合地理信息系统,运用地统计方法研究了黑河中游的临泽县绿洲农田20多年来土壤有机质含量的时空变化特征。结果表明:(1)1982年0~20 cm耕层土壤有机质含量平均为12.78±4.38 g/kg,2008年平均为13.76±4.02g/kg;从1982-2008年,有机质含量总体有所上升。(2)两个时期的土壤有机质的实验变异函数值与理论变异函数拟合均较好;克立格插值和不同时期的有机质空间分布图叠加运算表明,由于人为活动的影响,土壤有机质的结构性空间变化程度有所减弱。(3)临泽县土壤有机质含量和变化具有一定的区域性特点:南部的山前平原地区土壤有机质含量较高,呈现上升趋势;中部地势低下的区域土壤有机质相对较高,由于农田面积扩大,有机肥供应不足而下降显著;北部绿洲与戈壁交错带土壤有机质偏低。总体来看,临泽县土壤有机质含量有所上升,但局部地区的有机质发生了下降。为了防止局部区域土壤有机质下降引起土壤退化,应该采取加大有机肥投入和实施秸秆还田等措施。 相似文献