CONCURRENT STABILIZATION OF SOME INTERIOR DUNE FIELDS IN MICHIGAN

Inland dunes occur over a large part of east-central lower Michigan, where they mantle glaciolacustrine and outwash surfaces that were exposed around 12,000 yrs. B.P. The dunes are parabolic, with northwest-oriented limbs, and occur in swampy landscapes, suggesting that paleoclimatic conditions at the time of their formation were much drier and possibly windier. In order to determine whether the dunes stabilized concurrently or randomly in time and space, surface soils were studied on 30 dunes in the area and quantitatively analyzed for relative differences. Soils data from the dunes indicate concurrent stabilization, following a period of regional mobilization of aeolian sand. Surface soils have formed by podzolization, in uniform parent materials, and are morphologically similar throughout the area. All the soils are weakly developed, with subtle variations on a A-E-Bs-BC-C horizonation sequence. Munsell colors of Bs horizons are remarkably uniform, with 27 of 30 sites exhibiting values of 4 and chromas of 6. Chemical data suggest that Fe and Al translocation has been uniform throughout the region. When compared with soils of known age in northwest lower Michigan, the data indicate that dunes in the region had stabilized at least by 4000 yrs. B.P., leaving an approximately 8000-yr. interval in which they could have formed. In contrast to the prevailing southwesterly winds of today, dune-forming winds were dominantly from the northwest. [Key words: aeolian sedimentation, dunes, soil, Great Lakes, Michigan.]     

Alluvial Fans as Records of Holocene Sediment Yield in the Central Great Plains of Southwest Nebraska

Soils buried by alluvial fan deposits in southwest Nebraska record several intervals of increased sediment yield from small watersheds during the Holocene. These intervals, which began at ca. 9000, 5800, 4000, 3000, and 1000 ¹⁴C yrs. B.P., were probably caused by some sort of change in regional climatic conditions. Existing evidence of Holocene climate change suggests that increased sediment yields were caused by periodic shifts toward drier climatic conditions, except for the intervals that began at 5800 and 4000 ¹⁴C yrs. B.P. The cause of increased sediment yields at those times is unclear, although an increased frequency of large intense storms may have been a contributing factor. The record of soil burial exhibits considerable spatial variability both within individual fans and between fans. This is partly due to practical limitations on the number of buried soils that could be sampled on each fan. But it is also due to the inherent spatial variability of depositional processes and to differences in the geomorphic development of the four fans. Thus, researchers who use data from fans to reconstruct sediment-yield histories need to investigate several sites on several fans in order to obtain as complete a record as possible of changing sediment yields.     

Distribution characteristics of SOM and nitrogen on the eastern slope of Gongga Mountain

Soil is the largest carbon pool of terrestrial ecosystem, and its carbon content accounts for two thirds of the whole terrestrial ecosystem (Schlesinger, 1990). The soil organic matter (SOM) content and turnover rate exert impacts directly on the terrestrial ecosystem and global carbon cycles. Nitrogen is the main limiting factor constraining the plant growth (Vitousek etal., 1997; Pamela etal., 2002). Changes of the nitrogen content will change the microbial respiration through changing the…     

The relevance of humus forms for land degradation in Mediterranean mountainous areas

In the Gavarras (NE Spain), a large number of plots on respective schists, leucogranite and granodiorite was studied for their soils and vegetation. Results were used to check conclusions from earlier studies of Mediterranean forest soils (mostly shallow Regosols and Cambisols) on such acidic to intermediate rocks. They confirmed that the humus form depends on catenary position and lithology, and that aggregate stability and infiltration characteristics of the upper mineral soil horizon relate to humus form type. Aggregate stability of the topsoil was found to be relatively high in mor and mull type humus forms, but differences with moder type humus forms were not statistically significant. Differences in aggregate stability are attributed to the presence of stable humus–clay–iron complexes in mulls and to high fungal activity and organic matter content of mors. Low infiltration rates were only encountered in topsoils with mor type humus form, in line with results from the earlier studies. In deeper soil horizons with low organic matter content, aggregate stability will be largely related to soil reaction and base saturation. On leucogranite and granodiorite, these were found to vary strongly, most probably largely due to local differences in fast acid neutralizing capacity (ANC_f). These local differences are primarily attributed to differences in the mineralogical composition and texture of the soil material, connected with differences in lithology and/or brought about by erosion, colluviation and soil formation. Consonant with earlier studies, it is concluded that the susceptibility of these forest soils to erosion largely depends on properties of the upper mineral soil horizon, which are controlled by or related with humus form development. General trends in the latter are clear and can be used to predict this susceptibility. In the case of land degradation, which implies a more severe erosion, deeper soil horizons are also involved. Spatial variability in properties of these horizons, relevant for degradation, is considerable and not clearly related to humus form development. Accordingly, the abovementioned trends in humus form development cannot be used to predict the susceptibility to land degradation.     

Distribution characteristics of SOM and nitrogen on the eastern slope of Gongga Mountain

The distribution of soil organic matter (SOM) and nitrogen on Gongga Mountain was studied in this paper. The results showed that the content of SOM and nitrogen (N) of A horizon had an ascending trend with the increase of the elevation. The vegetation types distributed higher than the mixed broad-leaved and coniferous forest have the irregular trends. In the transitional zone vegetation such as mixed trees and treeline, the content of SOM and N is higher than other vegetation types. The distribution of SOM and N of A horizon is dependent on the synthetic effect of climate and vegetation types. The vertical distribution of SOM and N in soil profiles has the similar trends for all kinds of vegetation types, i.e., the content of A horizon is higher than that of the B and C horizons, which is the same to the distribution of dead animal and plant in soil. The soil C:N is between 7 and 25, which is relatively low comparing to the appropriate C:N of 25-30. The ratio of soil carbon to nitrogen (C:N) increases with the increase of the elevation, but its vertical distribution in soil horizons varies with different vegetation types. The N exists in SOM mainly in the form of organic nitrogen, and the soil C:N correlates significantly with SOM.     

贡嘎山东坡土壤有机质及氮素分布特征

The distribution of soil organic matter (SOM) and nitrogen on Gongga Mountain was studied in this paper. The results showed that the content of SOM and nitrogen (N) of A horizon had an ascending trend with the increase of the elevation. The vegetation types distributed higher than the mixed broad-leaved and coniferous forest have the irregular trends. In the transitional zone vegetation such as mixed trees and treeline, the content of SOM and N is higher than other vegetation types. The distribution of SOM and N of A horizon is dependent on the synthetic effect of climate and vegetation types. The vertical distribution of SOM and N in soil profiles has the similar trends for all kinds of vegetation types, i.e., the content of A horizon is higher than that of the B and C horizons, which is the same to the distribution of dead animal and plant in soil. The soil C:N is between 7 and 25, which is relatively low comparing to the appropriate C:N of 25-30. The ratio of soil carbon to nitrogen (C:N) increases with the increase of the elevation, but its vertical distribution in soil horizons varies with different vegetation types. The N exists in SOM mainly in the form of organic nitrogen, and the soil C:N correlates significantly with SOM.     

贡嘎山东坡土壤有机质及氮素分布特征

对贡嘎山东坡自然垂直带土壤有机质和氮素的分布特征的研究表明,贡嘎山东坡表层土壤有机质和全氮含量随海拔升高有上升趋势,但在针阔混交林以上出现波动,在群落过渡带处出现显著峰值,气候和植被类型的综合作用决定了有机质和氮素的空间分布。土壤有机质和氮素在土壤剖面中的垂直分布趋势一致,凋落物层和土壤A层高于B、C层,这与动植物残体在土壤中的垂直分布格局类似。群落过渡带在腐殖质A层出现氮素累积峰。土壤碳氮比介于7~25之间,相对较低,利于土壤腐殖质化和有机氮矿化。碳氮比随海拔升高而升高,在土壤剖面中的分布随植被类型不同而有所差异。土壤中的氮素主要以有机氮的形式存在于土壤有机质中,土壤碳氮比与有机质含量显著相关。     

RATES OF SOIL FORMATION ON BLACK MESA,NORTHEAST ARIZONA: A CHRONOSEQUENCE IN LATE QUATERNARY ALLUVIUM

A chronosequence of 17 soils in late Quaternary alluvium on Black Mesa, northeast Arizona, permits quantification of rates of pedogenesis in a semi-arid region. Based on 24 tree-ring, radiocarbon, and archaeological dates, soil ages range from about 100 to 20,000 to 30,000+ years. Data indicate that ochric, cambic, argillic, natric, and calcic horizons form within about 100, 500, 1000, 3000, and 15,000 years, respectively, whereas mollic epipedons form within 1000 years. Bk horizons with Stage I, I+, II+, and III carbonate morphologies form within about 1000, 4000, 10,000, and 15,000 years, respectively. Thickness of Bt and Bk horizons, and Harden profile development and clay accumulation index values increase in a linear manner with increasing soil age. High resolution dating suggests rates of pedogenesis on Black Mesa are rapid relative to those documented elsewhere in the southwest United States and in the Rocky Mountains. Rates of soil formation recorded on Black Mesa, however, necessarily incorporate the combined effects of slight variations in elevation, climate, vegetation, topography, and parent materials throughout the region, as well as the influence of additions of atmospheric dust at the soil surface. [Key words: soil, pedogenesis, soil geomorphology, Quaternary, Arizona.]     

The soils of Culbin forest, Morayshire: their evolution and morphology, with reference to their forestry potential

A brief account of the environmental conditions within Culbin forest is provided as a background to tracing the evolution of the area since late Glacial time. Where possible, the events are placed in historical order and the development and morphological characteristics of the soils are discussed.With the exception of the humus podsols, which are developed on an old dune system, the soils lack profile development. However, since the establishment of a tree canopy, soil horizon development has been initiated and a weakly developed iron podsol has been extensively mapped. Otherwise, the soils are classified as regosols. with some low-lying soils assigned to a gleyic subgroup. The widespread occurrence of buried peat and alluvial horizons was noted during fieldwork, and mapping units that incorporate these important horizons have been separated.Investigation into the potential of each of the mapping units for forestry reveals that where buried horizons are present significant increases in yield class can be anticipated: elsewhere nitrogen and general nutrient deficiency have seriously affected tree growth, which is only mediocre in performance. However, recent work has shown that a dramatic increase in yield class can be brought about with the application of fertilizer.     

PEDOGENESIS IN LATE PREHISTORIC INDIAN MOUNDS,UPPER MISSISSIPPI VALLEY

Inceptisols are developed on silt loam, loam, and sandy loam Indian mounds at the Keller Mound Group and Bluff Top Mound in northeastern Iowa. The mounds date to the Allamakee Phase of the Late Woodland Period (ca. 1650–1250 B.P.) and are built with fill obtained from the A, E, and upper B horizons of pre-existing soils (Alfisols). Differences in the morphologic and chemical characteristics of soils on different mounds are attributed to textural differences of the mounds' fill. Coarse-textured mound fill is pedogenically altered at a faster rate than fine-textured fill, but total carbon percentage of the A horizon attains a steady state faster in fine-textured mound fill. Total phosphorus content is used to determine from which horizons of pre-existing soils the specific layers of mound fill originated. Rates and pathways of pedogenesis in mound fill may not provide good analogues for the early stages of soil development in materials that have not undergone previous weathering and subsequent modification by humans. Nevertheless, mound soils are useful benchmarks for some pedologic studies since they provide time lines for evaluating minimum rates for development of argillic and albic horizons, as well as attainment of the Alfisol order.     

TEMPORAL TRENDS IN SOIL PRODUCTIVITY EVALUATIONS*

Studies of soil productivity must compensate for the effects of temporal trends in order to examine the pattern of crop yields along spatial gradients. An analysis of the published yield estimates for 30 soils in 233 counties, however, did not find consistent yield increases over the past three decades. On the contrary, the yield estimates for many soils were markedly uniform since 1972. The uniformity appears to have two causes: the acknowledged difficulty of making yield estimates in a time of increasing variability in soil and crop management, both within and between regions, and surveyors' awareness of data stored in a national soils data base. The effect is to cast doubt on soil productivity data reported in county soil surveys published between 1973 and 1988.     

RATES OF ORGANIC CARBON ACCUMULATION IN YOUNG MINERAL SOILS NEAR BURROUGHS GLACIER,GLACIER BAY,ALASKA

The functional relationship between organic carbon in surface mineral horizons of fine-grained soils and time of soil development is examined in a chronosequence of soils deglaciated within 40 years of sampling. Rates of carbon accumulation increased through time in the first 4 decades of pedogenesis. Little carbon accumulated in the first 10 years, but rapid accumulation occurred over the next 22 years as alders (Alnus crispa) began to colonize.

Several chronofunctions of carbon accumulation are derived for the Burroughs data. A second-order polynomial function provides a good model of carbon accumulation in the first four decades of pedogenesis that is stronger and more significant than conventional exponential and power function models. A data set extended to 1000 years based on earlier studies in the region, indicates that carbon accumulation rates in this proglacial environment can be expressed by a sigmoidal curve. Several conventional chronofunctions derived from the extended data are appropriate for various stages of pedogenesis, but none provides accurate approximations over the entire 1000 years of pedogenesis. [Key words: Glacier Bay, Alaska, soil, carbon, chronofunction.]     

中国土壤土层厚度的空间变异性特征

以全国第二次土壤普查的1627个土壤剖面资料为基础,在地质统计学和地理信息系统的支持下,以变异函数为基本工具初步分析中国土壤土层厚度的空间变异特征,并应用普通克里格法进行最优无偏线性插值,制作出分辨率为30km×30km的中国土壤土层厚度的空间分布图。结果表明:中国土壤土层厚度具有较好的可迁性和空间结构性特点,实验变异函数值的变化趋势基本上随着距离的增加逐渐上升,拟合变程在680km以上,土壤厚度的相关性可大于680km,土层厚度具有明显的块状或连续分布的特点     

Use of soil horizons for assessing soil degradation and reconstructing chronology of degradation processes: the case of Mwisanga Catchment, Kondoa, central Tanzania

This paper analyses the use of soil horizons for mapping soil degradation intensity and reconstructing chronology of degradation processes. Through “Pedogenetic Baseline Approach”, the catchment was classified into two categories: the erosional and depositional zones. The eroded soils were reconstructed even in those areas where there had been total soil stripping. Profiles of the undegraded soil provided a reference mark (particularly the argillic B horizon of Lixisols). One specific criterion for determining the degree of soil degradation of a given map unit in the erosional zone was based on whether A or B horizons or both had been eroded. Another criterion for classifying the units in the depositional zone was based on relating the quality of the buried soil with the overlying young soil developed from the colluvium/alluvium. Hence, the study underscores the importance of being able to reconstruct soil properties of pre-eroded soil profiles with the view to determining erosion units. This will eventually help in developing appropriate land use and conservation strategies.     

黄土中古土壤淀积类型

作者在西安附近发现了第１、４层古土壤的双层淀积和第５、８层古土壤多层淀积现象。资料表明，双层淀积、多层淀积和厚度异常大的ＣａＣＯ３淀积层是土壤具多元发生过程或受后期淋溶的产物，它们常代表两个或两个以上的成壤期。第１层古土壤下部的两层结构均不属古土壤组合部分，该层土壤为中、酸性森林土壤。第８层古土壤特殊的厚层淀积代表了气候的多次变化和多个成壤期。第４、５层古土壤具不连续ＣａＣＯ３和Ｆｅ２Ｏ３、Ａｌ２     

北亚热带江淮地区白浆化土壤的发生学特性

通过孢子花粉、石英砂颗粒和土壤微形态学分析,研究北亚热带江淮地区白浆化土壤的发生学特性。白浆化土壤下部土体经历了暖温带森林草原景观和亚热带草原景观,为高能化学环境。在母质沉积后,经历了褐土化过程或其他物质堆积,经过一定时期的沉积间断后,堆积新物质,随着气候的变化,成土环境演变为现代气候类型,属亚热带森林草原环境。淀积层也源于黄土状物质,风化程度更强,白浆层则为后期堆积物,不具备高能化学环境。淀积层在高能环境下,存在次生粘化和淀积粘化作用。     

临泽绿洲农田土壤肥力质量时空变化特征

干旱区荒漠绿洲农田土壤肥力质量的研究是绿洲功能和生产力评价的一个重要方面。通过1982年和2008年临泽绿洲农田287个样点耕层土壤（0~20 cm）有机质、全氮、碱解氮、速效磷和速效钾数据,利用地理信息系统和地统计学分析手段,研究了26 a来土壤肥力质量的变化特征。结果表明,研究区土壤有机质、全氮、碱解氮、速效磷和速效钾的含量为13.8 g·kg-1、0.81 g·kg-1、64.4 mg·kg-1、32.3 mg·kg-1、199 mg·kg-1,较1982年分别提高了13.5%、7.8％、9.3%、225.6％和26.8％;土壤肥力指标的变异性较大,变异系数均大于25%;模糊数学综合评价方法适合研究区土壤肥力质量评价,土壤肥力质量综合值由1982年的强度空间变异发展为中等空间变异;根据全国农业地力等级划分标准,研究区土壤属于4、5、6、7级,较1982年的土壤肥力呈上升趋势。土壤肥力综合值分布图可以为该区域土壤资源的合理利用提供理论依据。     

Soil development at Kongsfjorden, Spitsbergen

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.     

北方石质山区坡面土壤厚度分布特征——以北京市密云县为例

土壤厚度是土壤退化及土地生产力水平评价的一个重要指标。本研究应用插钎法,调查了北京市密云县山区50个基本抽样单元的坡面土壤厚度。对样点数据进行了统计分析,结果表明:平均土壤厚度为15cm。小于10cm的土壤占37%,小于20cm的土壤占76%,小于30cm的占90%。空间上土壤较厚的区域主要集中在西北和东北部植被覆盖较好的地区。对影响土壤厚度的因子进行分析发现:土壤厚度与海拔无明显相关性,而坡向对土壤厚度的影响较为明显,阴坡土壤厚度明显大于阳坡。土壤厚度与植被覆盖度和坡度明显相关,与植被覆盖度的相关系数为0.84,与坡度的相关系数为-0.40,二者都通过了显著水平为0.01的显著性检验。