Donald L. Johnson

Historical development of soil and weathering profile concepts from Europe to the United States of America

In the 1870s, agricultural geologists (pioneer pedologists) in Germany, Denmark, and Russia conceived of the soil profile. In more than a century since, pedologists have generally agreed on the reasons and purpose for using symbols such as A-B-C for the designations, but not on the definitions themselves or the assigned significance of the designations. In this paper, we submit that two seemingly conflicting classes of profile concepts evolved in the USA from European roots. The conflict stems historically from arbitrarily defined thin and thick profile concepts, often referred to as the soil or geologic weathering profiles, respectively. The pedologic or thin profile concept is depth-restricted when compared with the geologic thick weathering profile. The geologic profile concept was developed as a homologue of the pedologic profile and is considered to be the full or complete profile of weathering. Throughout the 20th century many variations of the concept of profile appeared, and all seem to have pedo-geo conflicts, exemplified by the myriad C horizon definitions by soil scientists. Recent concepts, such as the pedoweathering profile, have integrated the terminology used by pedologists and geologists into a functional and useful classification for all horizons of complete profiles. Full 21st century understanding of soils beyond the historic 20th century needs of agriculture, increasingly requires a knowledge of soil properties to greater depth than merely the historic solum and upper C horizon, and makes understanding subsolum properties more critical than ever before.

Tree uprooting: review of impacts on forest ecology

This paper reviews the ecological effects of tree uprooting. In many forests, disturbance by uprooting is the primary means of maintaining species richness and diversity. Treefall may be due to exogenous factors or it may be endogenously created, although the former predominate. The canopy gap formed by downed trees is often vital to community vegetation dynamics and successional pathways, by providing high light niches (gaps) for pioneer species, by encouraging release of suppressed, shade-tolerant saplings, and through recruitment of new individuals. Nutrient cycling may be affected by uprooting as subsoil materials are brought to the surface, via additions of woody debris to the forest floor, through exposure of bare mineral soil, and by changes in throughfall chemistry. The influence of the resultant pit/mound microtopography on understorey herb distribution is largely due to microclimatic and microtopographic variation. Tree seedling distribution, however, is related to microtopography primarily through differences in soil morphology, nutrition, and moisture content of mound and pit sites.

Biomantle evolution and the redistribution of earth materials and artifacts.

A biomantle is a differentiated zone in the upper part of soils produced largely by bioturbation, but often aided by subsidiary processes. One such process is loss of fine particles and redistribution of coarse ones from evolving biomantles. This is accomplished by rainwash and wind sorting of unprotected surface mounds and by vertical and/or lateral eluviation (lessivage) through-flow processes. Also subsidiary are the various processes by which iron, manganese, and other concretions come to reside in some biomantles. Concretions may form in biomantles directly from metal-bearing solutions, they may enter biomantles from upslope via creep and slope processes, or they may enter biomantles from below as the landscape down-wastes. Faunalmantles are biomantles produced largely by burrowing animals (faunalturbation), and floralmantles are produced largely by tree uprooting (floralturbation). Faunalmantles and floralmantles may be one-, two-, or multilayered, as differentiated by one or more observable or measurable soil properties. Chief among these properties are particle size and biologically produced soil fabric (biofabric). Complex biomantles result where faunal-mantles and floralmantles are conjoined or coevolve on the same tract or landscape. Stone zones, stone lines, or coarse-textured layers comprise the lower members of two-layered and multilayered faunal-mantles, and stone pavements comprise the upper members of two-layered and multi-layered floralmantles. Prehistoric and historic artifacts may be components of some floralmantle pavements and of some faunalmantle some lines and stone zones.

9 – A Survey of Disturbance Processes in Archaeological Site Formation

Publisher Summary This chapter discusses various processes of soil mixing, and the way mixing may affect archaeological context. The various processes of homogenization are collectively termed as pedoturbation—a synonym for soil mixing. Pedoturbation is the biological, chemical, or physical churning, mixing, and cycling of soil materials. The chapter presents the range and implications of pedoturbation processes in archaeological site formation. A reasonably accurate assessment of the pedoturbatory history of the soils and sediments at every archaeological site is absolutely prerequisite to valid archaeogeological interpretations. Soils are not static bodies—they are dynamic, open systems in which numerous processes operate to pedoturbate profiles, and to move objects vertically and horizontally within them. These processes can operate singly or in combination in additive or subtractive fashion, in all environments, and at all latitudes. Fingerprint topography and linear gilgai, for example, express the combined effects of argilloturbation and graviturbation in subtropical latitudes. At high latitudes and altitudes, gelifluction lobes are produced by graviturbation and cryoturbation and to some extent by aquaturbation. In many well-drained soils, faunalturbation by ants and earthworms might well offset the effects of cryoturbation. Very few archaeologists have the training to interpret soil dynamics subtly. Many of the processes are as yet poorly understood, even by soil scientists.

Chronology and rates of faulting of Ventura River terraces, California

New evidence concerning the chronology of four late Pleistocene terraces of the Ventura River near Oak View, California, that are vertically offset and tilted by reverse and reverse flexural-slip faults provides a means of estimating rates of fault movement and downcutting by the Ventura River. Radiocarbon ages of charcoal contained within terrace deposits date two of the terraces. Correlation of soils that have developed on terrace deposits and extrapolation of the rate of vertical displacement of the Arroyo Parida-Santa Ana fault (not a flexural-slip fault) date the others. Resulting age estimates for the four main late Pleistocene terraces are Qt5b = 30,000 Qt6a = 38,000, Qt6b = 54,000, and Qt6c = 92,000 yr B.P. Vertical-slip rates on flexural-slip faults range from <0.3 to 1.1 mm/yr and apparently are related to the rate, form, and mechanics of folding of the north limb of the Ayers Creek–Canada Larga syncline. Average rates of downcutting of the Ventura River for several intervals during the late Pleistocene, estimated from the chronology and relative elevation of river terraces north of the Arroyo Panda–Santa Ana fault upstream from the zone of faulting, vary from ∼0.5 to 1.3 mm/yr. The range in rates probably reflects variations in local uplift as well as adjustments to changing eustatic sea level, climatic conditions, and/or regional deformation of the western Transverse Ranges. The average rate of downcutting of the Ventura River north of the zone of flexural-slip faulting is ∼0.8 mm/yr, compared with 1.2 to 2.2 mm/yr in the deformation zone immediately to the south. This apparently indicates that during tectonic deformation there is an approximate balance between the rate of uplift due to faulting and folding and the rate of downcutting by the fluvial system.

Dynamic pedogenesis: New views on some key soil concepts, and a model for interpreting quaternary soils

Abstract Inasmuch as soils are open systems and rarely, if ever, achieve equilibrium with their environments, it is philosophically sound to view all soils as expressing varying levels of polygenesis as that term has been redefined. Soil genesis and resultant morphology may then be viewed in a comprehensive framework of soil evolution that consists of two linked pathways, one developmental and the other regressive, that reflect interactions of both exogenous and endogenous vectors (vectors are factors, processes, and conditions of pedogenesis). Following this philosophy, a model of pedogenesis is framed in an evolutional paradigm that emphasizes the integrated effects of dynamic and passive pedogenic vectors in directing pathways and in controlling rates of soil genesis through time. The dynamic vectors include energy and mass fluxes, frequencies of soil wetting and drying, water table dynamics, organisms, feedback processes, and pedoturbation. The passive vectors include parent materials, soil chemical environment, stability of geomorphic surfaces, and various evolved soil properties and conditions (accessions). Both sets of vectors vary spatially, and the dynamic vectors, more so than passive vectors, fluctuate through time. The model is expressed as S=f(D,P, dD dt , dD dt ) where S is the state of the soil or degree of profile evolution, D is the set of dynamic vectors, P is the set of passive vectors, and dD dt and dP dt denote change through time t. The model helps explain the apparent minimal development and regressed character of some old soils and the rapid and strong development of some young ones.

Proisotropic and proanisotropic processes of pedoturbation

Because pedoturbation processes (soil mixing) occur in all soils in varying degrees during the curse of their evolution, mixing processes should be assessed within the larger context of soil genesis. Soils may be viewed as evolving along two pedogenic pathways that operate concurrently: a progressive pathway that includes processes, factors, and conditions that promote ordered, differentiated and/or deep profiles; and a regressive pathway that promotes disordered, simplified, rejuvenated, and/or shallow profiles. Pedoturbative processes that disrupt, blend, destroy, or prevent the formation of horizons, subhorizons, or genetic layers, such that simplified profiles evolve from more ordered ones, are proisotropic and function within the regressive pathway. Pedoturbative processes that form or aid in the formation and maintenance of horizons, subhorizons, or genetic layers and/or promote increased profile order are proanisotropic and function within the progressive pathway. Ten forms of pedoturbation are recognized. Hypothetical and real examples of how proisotropic and proanisotropic mixing processes affect soil profiles are presented. The examples demonstrate that both the form of pedoturbation and the texture of the parent material largely determine whether the ensuing morphology of a soil expresses order or disorder. A particular form of pedoturbation may produce a disordered profile in one soils or polypedon, but a more ordered profile in another. This can be true not only for different soils on a landscape, but also for the same soil at different times during its evolution. Homogeneous or heterogeneous geologic deposits may be pedologically organized, or reorganized, via proanisotropic pedoturbation to express profile order and in certain cases may produce spatial patterning and microrelief. Surface stone pavements and armored surfaces, subsurface stone lines and stone zones, and upper profile biomantles can thus be formed.

The late Quaternary climate of coastal California: Evidence for an ice age refugium☆

The present Mediterranean climate of coastal California is unique in North America and reflects the interaction of several important synoptic controls, principally the North Pacific semipermanent anticyclone, and to a lesser extent the Aleutian low-pressure system and the cool California oceanic current. These synoptic climatic controls, key parts of the global air-sea circulation, were probably operative throughout late Quaternary time as shown by paleoecologic evidence. The thick accumulations of sediments in basins of offshore California indicate that while variable sedimentation regimes reflect changing climatic and oceanographic conditions, the Quaternary climate was probably semiarid as now, even during glacial maxima. Late Quaternary coastal dunes preserve former wind directions and show that prevailing late Quaternary winds were directionally equivalent to modern winds, which are controlled by the North Pacific anticyclone and by interactions between the North Pacific high and the interior basin low. These sand dunes contain buried, datable, carbonate-rich soils. Precipitation then, like the present rainfall regime, was not enough to leach the carbonates from the soils. Charcoal in buried dunes and soils shows that fire was environmentally important throughout the Quaternary, just as it is today. Fossil plants indicate that sclerophyllous vegetation and forest stands of conifers, adapted to a Mediterranean climate, were widely distributed during late Quaternary time. Fossil pollen in the Sierra Nevada indicates the influence of the North Pacific high. The historical precipitation record overlaps a late Holocene tree-ring record permitting extrapolation of the precipitation curve back nearly 600 years. Well-defined wet and dry trends in the precipitation pattern characterized this time span, and provide a possible analog to the earlier Holocene and Pleistocene precipitation regime. The paleoecologic record shows that the late Quaternary climate of coastal California was characterized by regimes similar to those prevailing today. The persistence of a Mediterranean climate in California during the last glaciation contrasts with dramatic climatic changes experienced in glaciated parts of North America. California thus was an Ice Age refugium for animals and cold-sensitive plants.

Kimmswick: A Clovis-Mastodon Association in Eastern Missouri

Stone tools characteristic of the Clovis culture have been found in direct association with bones of the American mastodon at Kimmswick, Missouri. The vertebrate fauna from Clovis components suggests a deciduous woodland and meadow habitat. Such an environmental reconstruction provides a new perspective for Clovis adaptations and the ecological tolerances of Mammut americanum.

Geochemical evidence for airborne dust additions to soils in Channel Islands National Park, California

There is an increasing awareness that dust plays important roles in climate change, biogeochemical cycles, nutrient supply to ecosystems, and soil formation. In Channel Islands National Park, California, soils are clay-rich Vertisols or Alfi sols and Mollisols with vertic properties. The soils are overlain by silt-rich mantles that contrast sharply with the underlying clay-rich horizons. Silt mantles contain minerals that are rare or absent in the volcanic rocks that dominate these islands. Immobile trace elements (Sc-Th-La and Ta-Nd-Cr) and rare-earth elements show that the basalt and andesite on the islands have a composition intermediate between upper-continental crust and oceanic crust. In contrast, the silt fractions and, to a lesser extent, clay fractions of the silt mantle have compositions closer to average upper-continental crust and very similar to Mojave Desert dust. Island shelves, exposed during the last glacial period, could have provided a source of eolian sediment for the silt mantles, but this is not supported by mineralogical data. We hypothesize that a more likely source for the silt-rich mantles is airborne dust from mainland California and Baja California, either from the Mojave Desert or from the continental shelf during glacial low stands of sea. Although average winds are from the northwest in coastal California, easterly winds occur numerous times of the year when “Santa Ana” conditions prevail, caused by a high-pressure cell centered over the Great Basin. The eolian silt mantles constitute an important medium of plant growth and provide evidence that abundant eolian silt and clay may be delivered to the eastern Pacifi c Ocean from inland desert sources.