Adjacent Undisturbed Areas Research Articles

Changes in soil chemistry associated with changes in soil-pH in Victorian pastures

Relationships between changes in soil pH and changes in other soil chemical properties were examined using data from a survey of 107 pasture sites from across Victoria. At each site, soil samples (0-5, 5-10, 10-15 and 15-20 cm depths) were taken from the pasture and an adjacent undisturbed (reference) area for chemical analysis. Changes in soil chemical properties were inferred from differences between pasture and reference soils. Increases in extractable Al and extractable Mn and decreases in the sum of exchangeable cations were associated with decreases in pH. Changes in soil organic C, total soil N and total soil P were not associated with changes in pH but were related to pasture composition at each site. Increases in total soil P and exchangeable Ca, and decreases in exchangeable Mg were partly attributed to the application of superphosphate. Decreases in electrical conductivity are discussed in relation to vegetation and salinization.

Assessment of soil moisture movement in nuclear subsidence craters

This study was undertaken to investigate the potential ground-water recharge resulting from a nuclear subsidence crater on the Nevada Test Site. Results from two boreholes, one completed in the subsidence crater bottom and the other completed in an adjacent undisturbed area, suggest that deep infiltration of periodically ponded runoff water at the crater bottom is occurring, whereas little or no deep infiltration was evident in the adjacent, undisturbed area. Specialized drilling, coring and borehole logging revealed high water contents and a unit hydraulic gradient downward beneath the subsidence crater. Traditional soil physics analysis via Darcy's law and core samples suggested a wide range of downward fluid velocities and fluxes beneath the crater. In contrast, soil water tritium concentrations, combined with several mixing models, significantly reduced the range of estimated fluxes. Based upon these models, it is suggested that the vertical flux beneath the crater is on the order of 0.6m year −1. It is postulated that the surface topography, combined with the coarse-textured soils beneath the crater, allows for the deep infiltration of ephemerally ponded water at the bottom. In the adjacent undisturbed (and topographically flat-lying) site, significant ponding does not occur, and evaporation and transpiration processes recycle much, if not all, of the precipitation falling on the surface.

Grasshopper Response to Rapid Vertical Displacements within a “Clear Air” Boundary Layer as Observed by Doppler Radar

Dual-polarization radar recorded insect behavior when a gust flow interacted with a deep, dense cloud of large insects over North Dakota on 4 July 1987. These data reveal areas within the upper parts of the cloud with apparent active modified flight behavior. Disturbed areas were separated from adjacent undisturbed areas by only a few hundred meters. The boundary layer was not capped and circulations were free to rise above an apparent flight ceiling of ≈1,800 m and where temperatures were in the range 12–15°C. Disturbances in some areas extended downward 1,000–1,200 m from the top of the cloud to levels where the temperatures were ≈10°C warmer. Kinematic analysis of Doppler velocities revealed close correspondence between the areas of modified flight behavior and strong updrafts (and in a few instances, strong downdrafts). The data permit at least five explanations for the apparent modified flight behavior. These are passive sorting in updrafts, and active response to turbulence, rates of change of temperature, rates of change of pressure, and the presence of clouds.

Bulk Density Changes in Two Central Oregon Soils Following Tractor Logging and Slash Piling

Abstract Bulk density changes were measured in two soil types within and adjacent to a 20-ha clearcut site in central Oregon. Yarding was done with rubber-tired skidders, and slash was piled with crawler tractors. Bulk density of the 0-20 cm depths was measured with a single probe nuclear gauge at randomly located sites in the clearcut and an adjacent undisturbed area with similar soils. Average bulk densities of sandy loam volcanic ash and cobbly loam soils were 35% and 23% higher, respectively, than undisturbed controls following yarding and piling. Detrimental compaction existed on 60%-66% of the harvest area when defined as either a 15% or 20% increase in bulk density. Compacted areas included skid trails, landings and land subjected to slash piling. The Proctor test and lower energy versions of this test were made on both soils to describe moisture density relationships in response to compactive forces. While the low energy curve appears to provide a good simulation of field bulk density of the cobbly loam soil, it is the moderate energy curve that provides the most reasonable estimate of soil densities after activities on the noncohesive sandy loam volcanic ash soils. West. J. Appl. For. 7(3):86-88.

Gopher Tortoise (Gopherus polyphemus) Effects on Soils and Vegetation in a Florida Sandhill Community

Burrowing and mound-building activities of gopher tortoises generated significant environmental heterogeneity in an oak-pine sandhill forest in Florida. Mounds were characterized by lower soil nutrient and organic matter concentrations, higher light intensities and greater diurnal temperature fluctuations than adjacent undisturbed areas. Temperatures during prescribed spring fires were significantly lower on mounds and near burrow openings relative to the surrounding undisturbed vegetation. Changes in plant species composition and relative abundances between recently abandoned mounds, old mounds and undisturbed areas indicated that mounds undergo microsuccession and contribute toward increased plant species diversity in the forest understory. Old mounds had the highest species richness per unit area. Mound size had no effect on plant population dynamics or community structure. Gopher tortoise disturbances increased the frequency of recruitment by seed relative to vegetative reproduction in the common rhizomatous forb, Pityopsis graminifolia.

Revegetation of a Taxodium-Nyssa forested wetland following complete vegetation destruction

Revegetation is described for a portion of a Taxodium distichum-Nyssa aquatica (bald cypress-water tupelo) forested wetland in South Carolina. Thermal effluent from nuclear production reactors from 1954 to 1968 eliminated most of the original vegetation from the study area. Vegetation in disturbed and adjacent undisturbed areas was sampled in 1981 and 1985 using permanent plots. Herbs invaded rapidly throughout the disturbed portion of the wetland after thermal discharge ceased. Shrubs (Salix spp. and Cephalanthus occidentalis) followed soon thereafter, and have gradually occupied more of the area. Taxodium and Nyssa regeneration is rare because of the inability of seedlings of these species to compete with the dense cover of herbs and shrubs. Species composition is correlated with water depth, substrate type, and severity of disturbance. Because of substrate diversity, several successional mechanisms may account for the revegetation patterns.

Nitrate increases in soil water following conversion of chaparral to grass

An Arizona watershed converted from chaparral to grass, released high concentrations of nitrate to stream water. The nitrate originated from the rooting zone of the decomposing shrubs. High nitrate concentrations (44–373 ppm) were found in soil solutions from 1.5-, 3.0-, and 4.6-m depths on the converted watershed as compared with low nitrate concentrations (0.2–6.2 ppm) found in an adjacent undisturbed area. Soil solution nitrate concentrations at the 0.3-m depth were generally low, especially in the untreated area. High nitrate concentrations were balanced mainly by relative decreases in bicarbonate anions in the soil solutions and in the stream water. Multiple stepwise regression analyses showed improvement in the regression of bicarbonate on nitrate when chloride and sulfate anions were entered as variables.

The residual effects of tracked vehicles on soil surface properties

Differences in soil surface properties were measured on soil cores collected from within tracks and adjacent undisturbed areas. The passage of tracks resulted in an increase in bulk density, a reduction in saturated hydraulic conductivity and an increase in cone penetrometer resistance. Laboratory direct-shear tests showed in-track soil was stronger than out-of-track samples. The saturated hydraulic conductivity of in-track soil cores increased with an increasing number of wetting and draining cycles, whereas out-of-track samples showed little change. Implications for erosion, vegetation regeneration and management strategies for off-road vehicle areas are discussed, with some speculation as to the rate of recovery of impacted areas.

Soil Bulk Density Recovery on Compacted Skid Trails in Central Idaho

AbstractIn west‐central Idaho, the bulk densities of soil in major skid trails were compared with those of adjacent undisturbed soil in order to determine rates of recovery. Five study sites on each of two soils, one formed from granitic material (mixed, frigid, Typic Xeropsamments) and the other from volcanic material (fine‐loamy, mixed Dystric Cryochrepts), provided two chronosequences (five 5‐yr periods) of time since logging. Bulk density was measured at 5.1‐, 15.2‐, and 30.5‐cm depths. The percent increase in bulk density of soil on a skid trail over that on an adjacent undisturbed area was greater in the volcanic than the granitic soil, but recovery rates (slope of the regression line) for the two soils were not significantly different. Linear regression models showed a significant (p < 0.05) recovery trend for all depths except the 15.2‐cm depth on the volcanic site. Except for the surface 5.1 cm of the granitic soil, none of the bulk densities in skid trails had returned to the undisturbed values in the 23 yr since logging.

Characterization of Soil Compaction at Construction Sites and Woody Plant Response

This study was designed to quantify soil compaction occurring at construction sites and determine the effect of soil compaction on woody plant growth. Soil compaction was measured at 12 sites including residential, commercial, and new road construction. Methods of measurement included bulk density, determined with a nuclear densiometer and by the rubber balloon method, and penetrometer resistance. Bulk density in the construction zone averaged 0.50 g/cm3 (33.09lb/ft3) higher than in an adjacent undisturbed area. Bulk density readings in the construction zone were in the range that has been found to restrict growth of woody plants. Penetrometer resistance was higher in the construction zone, but this was a less reliable method of measure than bulk density for this type of site. A field study was conducted to determine the effect of compaction and puddled soil on the growth of Forsythia ovata Nakai and Cornus sericea L. Treatments included puddled soil and low, medium, and high levels of compaction. Although levels of bulk density achieved in the field plots were lower than those observed at construction sites, growth of both species was reduced by all treatments compared to the check.

Diversity and abundance of selected animal species in undisturbed forest, selectively logged forest and plantations in East Kalimantan, Indonesia

Animal surveys were conducted in six habitat types within the timber concession of PT International Timber Corporation Indonesia, East Kalimantan. Species diversity was found to be similar in undisturbed forest and in 3- to 5-year-old selectively logged forest, although densities in the latter were considerably less. Both diversity and density declined drastically in forestry plantations, but certain of the species remaining caused significant damage to young trees. Although few animals were observed in areas where there was active road construction and timber felling, their densities in adjacent undisturbed forest areas did not increase, suggesting that the level of local migration actually is low. It is suggested that recolonisation of old logged forest can occur successfully provide that the level of hunting is low and that adjacent areas of undisturbed forest remain to provide a population pool from which colonists can spread.

The impact, control, and mitigation of off-road vehicle activity in Hungry Valley, California

Hungry Valley, and arid basin situated within the Transverse Ranges of Southern California, has been utilized by off-road vehicles (ORVs) since 1971. Loss of vegetation, severe soil erosion and gullying, alluvial fan formation, and increased sediment discharge are the direct results of ORV activity in the valley. These hydrologic-geologic effects have been documented and monitored utilizing sequential aerial photographs, ground surveys, and sediment transport measurements. Despite the increased usage of ORVs on public lands, and the well-documented short-term physical environmental impacts, little data exists on erosion or sediment transport rates in disturbed vs. adjacent undisturbed areas, the ability of natural vegetation to re-establish itself, or the feasibility of site rehabilitation techniques or methods.

Salt Tolerance of Two Saltbush Species Grown in Processed Oil Shale

The tolerance of fourwing saltbush (A triplex canescens) and cuneate saltbush (Atriplex cuneata) to the salts in processed oil shale was studied in a greenhouse experiment over an ECe range of 4 to 38 mmho/cm. Growth responses differed, depending on the species and the particular salt or salts in the soil solution. Cuneate saltbush was more salt tolerant than fourwing saitbush, but both species survived and grew at salinities as high as 38 mmho/cm. Because of their high salt tolerance these saltbush species may be very important for use in the rehabilitation of processed oil shale disposal sites. Commercial scale surface retorting of oil shale will result in large amounts of processed shale that may be deposited in canyons as land fill. Any lessee of federal prototype oil shale lands is required to rehabilitate affected lands to a useable and productive condition. .compatible with existing adjacent undisturbed natural areas. .that will support fauna of the same kinds and in the same numbers as existing at the time the basline data were obtained. . (Federal Register 1973). Establishment of vegetation must be considered as one of the prime steps of rehabilitation. One of the major obstacles to successful plant establishment on processed oil shale is high salinity. Electrical conductivities of saturation extracts (ECe's) of several processed shale samples ranged from 9 to 26 mmho/ cm in studies of Schmehl and McCaslin (1973) and from 5 to 22 mmho/cm in our studies (Institute for Land Rehabilitation 1979). Soils are usually considered saline when ECe values reach 4 mmho/cm (Richards 1954). In addition to the total salinity, as measured by EC, the specific ion composition of the shale may have important effects on plant growth as well. The predominant soluble salts in processed oil shale are sodium sulfate and magnesium sulfate, while concentrations of chloride salts are relatively low (Schmehl and McCaslen 1973). For example, the first liter of leachate obtained from columns of paraho processed oil shale at Utah State University contained 509 milliequivalents per liter (meq/ l)Na +, 436 meq/ 1 Mg++, 882 meq/ 1 SO4'and only 14.1 meq/ 1 CL(Institute for Land Rehabilitation 1979). The leachate also contained 23.5 meq/l Ca,19.3 meq/ I K+, and 1.6 meq/l HCO3 Two plant species of interests for rehabilitating processed oil shale in Utah are fourwing saltbush (Atriplex canescens) and cuneate saltbush (Atriplex cuneata). Both species are native to the federal oil shale lease tracts, U-a and U-b, in eastern Utah (VTN Colorado, Inc. 1977). The species are noted for their salt and drought tolerance and their forage value (Blauer et al. 1976). These two species occupy different Authors are research associate and director, Institute for Land Rehabilitation, Utah State University, Logan 84322. This study was conducted as a project of the Institute for Land Rehabilitation, Utah State University, and was supported by funds from the White River Shale Project, Vernal, Utah. Manuscript received July 13, 1979. habitats and may have different soil requirements and salt

The Ecological Impact of Pedestrian Traffic on Alpine Vegetation in Kosciusko National Park

SUMMARY Comparative observations of relative cover and species composition along walking tracks and on adjacent undisturbed areas were carried out to determine the impact of pedestrian traffic on alpine vegetation in Kosciusko National Park. The eight main plant alliances of the alpine zone were all modified to some degree by trampling and subsequent erosion, although the nature and extent of the modification varied widely, as did the resistance of plants to trampling. Except for climatically and edaphically extreme habitats, bare ground and erosion initiated by trampling created niches for opportunist species, mainly fast-growing annuals, to colonise. Sections of the walking tracks most in need of attention were those over bog vegetation and those leading straight up slopes. Further damage would almost certainly be detrimental, whether judged from the viewpoint of aesthetics or soil conservation, and could be avoided by appropriate measures such as the installation of cross drains, the stabilisation of e...