Undisturbed Landscapes Research Articles

Development of microtopography in a semi-arid grassland: Effects of disturbance size and soil texture

Our objective was to evaluate effects of disturbance size and soil texture on the development of microtopography for a shortgrass plant community in north central Colorado USA. Disturbances, defined as the death of individual plants, were created in 1984 and 1985 to evaluate development through time of the small-scale pattern of perennial bunchgrasses and bare soil openings that characterize this semiarid grassland. Disturbed plots of three sizes (50, 100, 150 cm-diameter) comparable in size to naturally-occurring disturbances were produced by killing plants at two sites differing in soil texture (sandy loam, clay loam). Disturbed plots were not manipulated after being created. In 1993, a laser surveying instrument was used to measure heights of crowns of individual plants of the dominant species, the perennial bunchgrass Bouteloua gracilis ([H.B.K.] Lag. ex Griffiths), and bare soil openings between plants for two locations: within each disturbance and in the surrounding undisturbed landscape. Differences between crown heights of plants and bare soil openings were comparable for both the undisturbed landscape and inside disturbances indicating that small-scale microtopography had recovered within nine years after disturbance occurred. However, complete recovery to the undisturbed state had not occurred since crown heights of plants relative to bare soil openings were significantly less on disturbed than undisturbed locations. Differences in height between plant crowns and bare soil openings on disturbed plots increased as disturbance size increased, indicating greater soil redistribution with increasing plot size. Larger differences in height were also found on plots on the fine- than the coarse-textured soil, indicating the importance of soil particle size and plant cover type to the development of microtopography. Differences in height between microsites on disturbed plots were positively related to total plant cover and negatively related to cover of B. gracilis indicating the importance of this species to reducing erosion on disturbed areas. In this semiarid grassland, patterns in microtopography were heterogeneous, likely as a result of the small-scale redistribution of soil between bare soil openings and B. gracilis plants through time. Our results indicate that this redistribution of soil is affected by disturbance size, soil texture, and patchy plant cover. The major effect of small-scale disturbances on patterns in microtopography of the shortgrass steppe are causing plant death and exposing soil to erosional and depositional processes.

Topographic Influences on Soil Water and Spring Wheat Yields on Reclaimed Mineland

AbstractTopographic positions on undisturbed soils affect available soil water and crop yields. Reclaimed minelands are required by regulation to have productivity levels “equal to or greater than” premine levels. Since a normal reclamation technique is to place uniform depths of topsoil and subsoil across the topography, this technique often changes the topsoil and subsoil depths from the premine condition. The objective of this research was to determine if these changes in topsoil and subsoil depths have resulted in effects on soil water and crop yields unlike those documented for undisturbed soils. This study was initiated on reclaimed mineland in 1986 at two North Dakota coal mines where topographic positions (summit, shoulder, backslope, and footslope) were monitored for 6 yr for available water at planting, spring wheat (Triticum aestivum L.) yields, and soil water recharge from harvesting to planting the following year. Results showed that downslope topographic positions had nearly 300% more available soil water at planting (0‐ to 1.2‐m depth due to greater recharge) and generally significantly greater (P = 0.10) spring wheat yields than upslope positions. Relationships between total water use and wheat yields were similar to those found for undisturbed soils. These results seem to suggest that the uniform depths of replaced topsoil and subsoil have not affected soil water and wheat yields differently on reclaimed minelands than on undisturbed landscapes in a semi‐arid climate.

Forgotten Hardwood Forests of the Coastal Plain

THE destruction and alteration of upland ecosystems on the Atlantic coastal plain of the United States have received little attention, particularly in comparison with wetland and longleaf pine ecosystems. The purpose of this article is threefold: to show that hardwoods were far more common in precolonial times than is generally believed, that upland hardwood forests have been the most ruthlessly exploited ecosystem on the coastal plain, and that the decline of hardwood upland forest has been far more severe than has that of any wetlands in the region. The details of this study are confined to the North Carolina portion of the coastal plain, but the basic trends are applicable to its entire southeastern expanse. This article illustrates the principle that conservation efforts are often focused on essentially marginal lands, where remnants of relatively undisturbed landscapes and ecosystems exist. Landscapes and ecosystems associated with the best land have usually been so thoroughly altered that public recognition of the problem is limited, with few efforts to preserve or restore them. LONGLEAF PINE FORESTS There has long been a misconception that Pinus palustris is the dominant upland tree in undisturbed coastal-plain forests. Pioneering foresters Gifford Pinchot and W. W. Ashe (1897) asserted that the forest on the North Carolina coastal plain before European contact was mostly longleaf pine and described and mapped a portion of this forest that extended almost unbroken to Virginia. An early-twentieth-century map of vegetation in the United States generalized the entire Atlantic coastal plain as southern mesophytic evergreen forest (Livingston and Shreve 1921). Early soil surveys likewise reported longleaf pine as the original vegetation on the most common upland soils (Bureau of Chemistry and Soils 1924, 1928, 1929, 1935). The myth of a continuous longleaf forest across the coastal plain, interrupted only by swamps and other wetlands, persists in relatively recent scholarly endeavors (Clark 1984; Williams 1989; Walker 1991). According to many biogeographers and ecologists, longleaf dominate only on the driest and sandiest coastal-plain uplands, where fire is a crucial element in establishing and maintaining longleaf-dominated forests and savannas (Wells 1928, 1942). The map of potential natural vegetation does not indicate longleaf-dominated uplands throughout the region (Kuchler 1964), and recent natural-community inventories give a more realistic appraisal of the original extent of the longleaf (Frost, LeGrand, and Schneider 1990; LeGrand, Frost, and Fussell 1992). Considerable evidence validates that the longleaf pine was found primarily on the sandiest, droughtiest, most excessively drained land or on wet, sandy, relatively sterile soils. A study made shortly before the Civil War found the pine only on dry, soil and considered occurrence of the species indicative of a sterile soil (Ruffin 1861). Although Ruffin implied that longleaf pine was restricted to those sites because it been eliminated from more favorable settings, earlier accounts suggested differently. Observations from the mid-1770s noted open pine forests, which were most likely longleaf savannas, on sand hills in southeastern North Carolina (Bartram 1791, 473-477). Bartram also concluded that generally occupied places on the coastal plain from Florida to the Carolinas (Bartram 1791, xvi). Land west of the Dismal Swamp on the coastal plain along the North Carolina-Virginia border had all the marks of poverty, being for the most part and full of pines (Byrd 1728). An even earlier account contained a report from a 1663 sailing on the Cape Fear River that described as growing, for the most part, in barren and sandy situations (Lawson 1709, 74). UPLAND HARDWOOD FORESTS Biogeographers and ecologists have long asserted that minimally disturbed mesic uplands in the coastal plain will develop hardwood forests. …

Cross‐Scale Morphology, Geometry, and Dynamics of Ecosystems

Community ecology and ecosystem ecology seem to have existed in different worlds. Levin (1989) suggests that the gulf between the two is the consequence of the different historical traditions in each. Community ecology, for example, emerged from basic studies, where generalized patterns were sought in the natural interactions among the biota. From the outset, the goal has been to deduce general and simple theory. On the other hand, many of the modelling approaches developed to understand ecosystem dynamics emerged from specific applied problems, where not only biotic but abiotic and human disturbances transformed ecosystem function. That tradition, therefore, is often more complete, but at the price of producing a collection of complex specific examples from which generalization is difficult.

An Archaeological Survey of Skomer, Dyfed

Skomer is an island off the west coast of Dyfed, the archaeology of which, consisting of fields, small enclosures, cairns, huts and dams, is well preserved. The broad outline and much detail was recorded by W. F. Grimes in 1950 and it was demonstrated that about two-thirds of the island is covered in a more or less undisturbed prehistoric landscape, preservation being due to the absence of Medieval and later settlement. The fieldwork described in the present paper was designed to record in detail small enclosures, or pounds, and habitation sites, mainly at a scale of 1:100 which was not done by Grimes. In addition two sets of air photographs were used to make a map of the fields. The work was done as a student exercise and is accordingly largely descriptive. However, analysis at two spatial levels has been attempted, one for huts and pounds and one for settlement complexes as a whole. But beyond the island itself there has been no comparative survey. The remains could be of any age from the Neolithic to early Roman period.

The great war

Abstract These stereo cards are from the set ‘The Great War’, published by H. D. Girdwood, ca. 1917 The 200-card set, one of his ‘Realistic Travels’ series, covered the 1914/16 period of the war, and most of them authentically show troop mobilization and movement, the effects of bombardments, parades, etc. However, during these years, photography at the actual battle fronts was subject to severe censorship and control, and so approximately fifty of the cards in the set which purport to show events at the front line, on closer examination, portray something rather different. Most, if not all, of these battle sequences were obviously staged, at locations far from the front. ‘Corpses’ are placed in picturesque attitudes of death, the trenches are neat, practice ones set in placid, undisturbed landscapes, and the troops are immaculately turned out. The term ‘Theatres of War’ takes on an unintentiOnal meaning, as it is indeed in the dramatic theatrical sense that these battle sequences are staged.

Soil Variability on Surface‐Mined and Undisturbed Land in Southern Illinois

AbstractFive different soil units were defined on surface‐mined land to group soils that were constructed by similar mining and reclamation methods and from similar materials. Three soil units were defined on undisturbed landscape using the traditional soil series concepts of soil classification and mapping. The goal in defining and mapping soil units on both surface‐mined land and undisturbed land was to minimize variation of soil properties within soil units.A nested sampling design allowed for testing the lateral variation of selected properties within and among the five units on surface‐mined land and within and among the three units on undisturbed land. The analysis of variance conducted separately for the constructed soil units and the undisturbed units indicate that there are more significant differences among the five constructed soil units than among the three undisturbed soil units.Variability, as measured by the coefficient of variation, within the constructed soil units was similar to that within the soil units on undisturbed land. Pre‐mine overburden characteristics and method of soil construction are useful guides for mapping soils on surface‐mined land.