Coarse Fragment Content Research Articles

Regolith Strength, Water Retention, and Implications for Ripping and Plant Root Growth in Bauxite Mine Restoration

The lateritic bauxite in the Darling Range of Western Australia is approximately 4–6 m deep and is composed of caprock (duricrust) and underlying friable bauxite developed from highly weathered granite and dolerite. This paper investigates the impact of mine floor ripping operations on materials exposed after mining in relation to strength, water retention, and plant root growth. Deep ripping has been shown to create a structured rootzone and increase both recharge and plant available water. Material classified as quartz rich (Zm) lacks structural features for plant root growth, yet the material requires the least force to rip. These materials require deep pre-ripping followed by contour or multi-tine ripping for successful restoration. Materials that contain 50% or more coarse fragments (gravels, cobbles, and stones) increase the force required for pre-ripping operations but only require contour or multi-tine ripping; doleritic clay with a high coarse fragment content may be readily colonized by roots without pre-ripping. Localized compression (smearing) of materials may occur during ripping due to the pre-ripping tine working deeper than its critical depth of 1.0–1.5 m and/or ripping of materials at high moisture content. A relationship exists between the ratio of reactive silica to total silica and the clay content of regolith, both properties being determined from pre-mining borehole samples. This ratio can be used to identify future mine floor materials from borehole data prior to mining and to target ripping operations to appropriate regolith types to enable the most effective and economical restoration practice.

Effects of coarse fragment content on soil physical properties, soil erosion and potato production

Most potato (Solanum tuberosum L.) production in northeastern America is on till soils with an abundance of stones. Stone picking has removed many coarse fragments to a point that it might be detrimental to soil quality. This study was to assess the impacts of coarse fragment content (10–19 mm in diameter) on selected soil physical properties, field soil thermal and water regimes, runoff and soil loss and potato yield and tuber quality on a sandy loam soil in New Brunswick. The objectives were to evaluate both beneficial and adverse effects of coarse fragment content (0, 10, 20 and 30% by volume) on soil quality in relation to potato production over a 4-yr period. Soil bulk density increased significantly by incorporating 10 to 30% coarse fragments into the plow layer. Porosity and available soil water-holding capacity were reduced in response to this increase in bulk density. In spite of the reduction in total porosity, pore size greater than 148 µm diameter of the 30% coarse fragment treatment was significantly greater than the 0, 10 and 20% treatments during 2001, 1 yr after the treatments were applied. This increase in macropores may have been responsible for the significantly higher saturated hydraulic conductivity of the soil treated with 30% coarse fragments. The results from 2002 and 2003 show that these beneficial effects on soil physical properties were short lived in this study; however, this may not be the case under field conditions because experimental plot problems of relocation of coarse fragments beyond plot boundaries and/or dilution with incorporation of stone-free subsoil material is not an issue in the field. Volumetric water content at field capacity of −33.3 kPa matric potential declined from 20.9% for the control to 7.7% for the 30% coarse fragment treatment. Cumulative soil heat greater than 10°C of the 30% treatment showed significant increases of 11.2, 8.8, and 3.7% during the growing season of 2001, 2002, and 2003, respectively, as compared with the control. Although field soil water tension regimes revealed that soil water in different treatments was held at a somewhat similar energy status, field soil water content was reduced considerably with increasing amount of coarse fragments. No significant differences in runoff and soil loss were found between treatments, but average reductions in soil loss over the 3-yr period were 9, 36, and 47% lower than the control for the 10, 20, and 30% treatments, respectively. Although no significant difference in yield and tuber quality between treatments was found in 2001–2003, both total and marketable yield decreased with increasing time. The yield reduction over time may be directly attributed to the mono-culture of potatoes practiced during the course of this experiment. Key words: Soil temperature, soil moisture, conductivity, bulk density, tillage erosion, potato cropping

Impact of effective soil volume on growth and yield of rubber ( Hevea brasiliensis)

Soil is a three dimensional body that is exploited by plant roots to extract water and nutrients. Depending on the conditions of soil development, part of the soil volume may be occupied by coarse fragments, which cannot be penetrated by plant roots. In a part of one study, we applied factor analysis to the available soil survey data to understand the basic relationship among soil properties and soil qualities using sand, silt, clay, coarse fragments (2 to 50 mm size) and depth. Subsequent to analysis of regression of available water capacity (AWC) on factor scores, we then utilized the results to evaluate the role of effective soil volume (ESV) on the plant performance in terms of growth and yield of rubber. Sixty two soil series, which are under rubber plantations in traditional region of cultivation in India, had varied weighted means of coarse fragment content ranging from less than 15 to 81% by volume along with variation in other soil properties too. Factor analysis extracted two factors, which described a total variance of 72%. The first factor was named as ‘surface area factor’ (that described 46% of variance) to which sand fraction was negatively related while silt and clay were positively related. The second factor was identified as ‘soil water availability factor’ (that described 26% variance) to which coarse fragments were negatively related whereas depth showed a positive relation with the same. AWC regressed on the scores of both the factors significantly indicating the most likely influence of soil texture, coarse fragments and depth on the availability of water, obviously along with plant nutrients when soil water is regarded as soil solution. Results of analysis of data generated in Part II of the study indicated that increased FLESV (first layer effective soil volume, corresponding to the depth of 0–11 cm) increased the growth of rubber trees observed during second, third, fourth, fifth and seventh year after planting with correlation coefficients (Pearson's) 0.432 ⁎⁎, 0.383 ⁎, 0.321 ⁎, 0.357 ⁎ and 0.325 ⁎ respectively ( ⁎ and ⁎⁎ indicate significance at 5 and 1% level, respectively). During the second year of growth, a significant correlation was observed between growth and ESV at 0–22 cm ( r = 0.366 ⁎) as well as 0–44 cm ( r = 0.346 ⁎). Rubber latex yield was found to be influenced by the FLESV (First Layer Effective Soil Volume) only that is the surface 0–11 cm layer ( r = 0.381 ⁎). The present fertilizer recommendations for rubber plants do not take the effective soil volume into account. Generally the properties measured in < 2 mm soil fraction are taken into consideration and rating charts for advisory purposes are prepared based on the STCR (soil test crop response) studies and rubber nutrition also follows the suit. In the future, the effective soil volume should be considered for development of fertilizer recommendations for rubber in a field where coarse fragments comprise a significant portion of soil.

Dielectric constant time stability of glacial till at a clear-cut site

Temporal stability of spatial patterns (time stability) of field measured soil water content has been attributed to soil texture and topographic curvature in agricultural soils, but limited information is available on time stability of soil water content of forest soils composed on non-stratified glacial tills. We studied time stability of soil water regimes by measuring soil dielectric ( ε) properties of fine-grained glacial till (0–15 cm) at 1-m-spacing along a 110-m-long transect with TDR twice a week through one growing season, from the 31st of May to the 1st of October 2001, in Finnish Lapland. The formerly Norway spruce ( Picea abies L. Karst.) covered site was clear-cut, subsequently burnt over and mechanically prepared with a disk drencher, and then regenerated to Scots pine ( Pinus sylvestris L.). Ten years after silvicultural treatments the measurements of soil ε, analyzed with Spearman's rank correlation coefficients, showed significant time stability ( r s = 0.83–0.93; P < 0.01) of soil water content for the whole season. Precipitation in July (122 mm) was twice as high as the average (1982–1999), but a persistent pattern of the soil ε occurred during both the drying phase which lasted until the end of June and the wetting phase which took until the end in September. Soil texture and topographic curvature were found to be secondary to coarse fragment content in contributing to spatial persistence of the soil ε. The minute recovery of vegetation after forestry practices also demonstrated that evapotranspiration and root water uptake played a negligible role in the soil water dynamics. Our results imply that the time stability of the spatial pattern of soil water regimes in glacial tills largely accounts for the composition of tree species in northern boreal forests and should be taken into consideration when artificial regeneration is contemplated in the harsh climate of Lapland.

Determination and Analysis of Interrill Erosion of a Soil with Coarse Fragments in Taiwan

To evaluate the effects of coarse fragments in soil on interrill soil erosion, a programmable rainfall simulator and soil erosion boxes were designed and fabricated. Simulated rainfall erosion tests were conducted on soils with coarse fragment contents of 0%, 7.5%, 15%, 30%, and 45%; at slope steepnesses of 9%, 20%, and 30%; and under simulated rainfall intensities of 40, 60, 80, and 100 mm h-1. A total of 132 data sets were obtained. It was found from the test results that coarse fragments had a mitigating effect on soil erosion at high rainfall intensities, and the steeper the slope, the better the effect. However, there was no apparent positive correlation between such mitigating effect and the percentage of coarse fragments in test samples. When part of the coarse fragments were exposed at the soil surface, both positive and negative effects might result, and a quantitative evaluation thereof requires further study. Furthermore, regression analysis and an artificial neural network were used in this study to establish a general equation and a three-layer back-propagation neural network model for estimating interrill soil erosion. While the regression equation is in harmony with the conceptual mechanisms of soil erosion, with an R2 value of 0.900 and an RMSE of 0.429, the artificial neural network model has a higher R2 value of 0.962 and a lower RMSE of 0.342, indicating that the artificial neural network model may provide better estimation of interrill soil erosion.

English

The Appalachian coalfields occur largely under rugged mountains covered by native hardwood forests. These forests, soils, and bedrock are removed by the surface mining process. Surface mines are not typically reclaimed to a managed forest land-use, but are often seeded with non-native grasses and legumes, or with pines, black locust, and shrubs for unmanaged forest land. Surface mining and reclamation techniques since the passage of the Surface Mining Control and Reclamation Act of 1977 (SMCRA) create highly compacted mine soils with high coarse fragment content, low organic matter, and high pH, which inhibits native forest reestablishment. The purpose of this study was to develop a forest site quality classification model to advise landowners on the production potential and feasibility of reforesting their mined lands with white pine (Pinus strobus L.). Ten selected physical, chemical, and site properties were assessed and a model was developed using variables that were the most highly correlated with the growth of 10- to 18-year-old white pines established on post- SMCRA surface-mined sites. A model with soil pH, texture, density, and rooting depth variables yielded a coefficient of determination of 0.71. Sufficiency curves were used in a productivity index (PI) model to classify reclaimed surface-mined land into one of five forest site quality classes (FSQC). A site index (SI50 = dominant tree height at age 50) for white pine was estimated for each class, and this measure of productivity may be used to aid in management decisions regarding reforestation of surface mines in the Appalachian coalfields.

Estimating bulk density in vertically exposed stoney alluvium using a modified excavation method.

Despite many decades of education and refining land-use practices, accelerated stream bank erosion is still prevalent in the United States. Eroding stream banks produce a sediment load to the riverine system and can cause reduced water quality as a result of increased suspended sediment. As total maximum daily loads (TMDLs) for water bodies impaired by turbidity or suspended sediments become more numerous, a simple, in situ field technique will be needed to estimate the bulk density of readily erodible stream bank material so that reasonably accurate sediment loading rates can be estimated. In this study, the excavation/polyurethane-foam technique for estimating total bulk density was applied to vertically exposed alluvium with high coarse-fragment content. Though not previously attempted in vertically exposed alluvium with high coarse-fragment content, the excavation/polyurethane-foam technique appears to provide a reasonably accurate estimate of the total and soil (<2-mm size fraction) bulk density from vertically exposed, alluvial deposits with high coarse-fragment content (i.e., >70%) along eroding stream banks. Obtaining bulk density estimates using this method would facilitate calculation of sediment loading rates to riverine systems with actual field data.

Forest Soil Productivity of Mined Land in the Midwestern and Eastern Coalfield Regions

Our goal was to determine the effects of surface mining on forest land productivity in the eastern coalfields of the USA before the passage of the Surface Mining Control and Reclamation Act of 1977 (SMCRA), and to determine the extent to which selected mine soil properties influenced forest productivity. The site productivity of 14 mined and eight nonmined sites in the eastern and midwestern coalfields were compared. Results show that site productivity of nonmined sites and 12 of the 14 mined sites was similar. Sites with low productivity were shallow, had high coarse fragment contents, and had lower fertility. Regression analysis identified five influential soil properties affecting site quality, which included soil profile base saturation (BS), total coarse fragments, total available water, C horizon total porosity, and soil profile electrical conductivity (EC). These five properties explained 52% of the variation in tree growth. Forests on most prelaw mined sites were just as productive as the forests on unmined adjacent sites and can be used as a benchmark to assess the impacts of current reclamation on mine soil quality and forest productivity.

Forest Soil Productivity of Mined Land in the Midwestern and Eastern Coalfield Regions

Our goal was to determine the effects of surface mining on forest land productivity in the eastern coalfields of the USA before the passage of the Surface Mining Control and Reclamation Act of 1977 (SMCRA), and to determine the extent to which selected mine soil properties influenced forest productivity. The site productivity of 14 mined and eight nonmined sites in the eastern and midwestern coalfields were compared. Results show that site productivity of nonmined sites and 12 of the 14 mined sites was similar. Sites with low productivity were shallow, had high coarse fragment contents, and had lower fertility. Regression analysis identified five influential soil properties affecting site quality, which included soil profile base saturation (BS), total coarse fragments, total available water, C horizon total porosity, and soil profile electrical conductivity (EC). These five properties explained 52% of the variation in tree growth. Forests on most prelaw mined sites were just as productive as the forests on unmined adjacent sites and can be used as a benchmark to assess the impacts of current reclamation on mine soil quality and forest productivity.

Soil variation within a hummocky podzolic landscape under intensive potato production

The purpose of this study was to determine if relationships between landscape position and soil properties occurred on a podzolic landscape with hummocky meso-topography, which is under intensive potato production in New Brunswick, Canada. Elevation was measured on an approximately 5 m grid spacing and used to construct a digital elevation model. Selected soil textural, morphological and chemical properties were measured on a 7×17 grid with 25 m spacing. Landform segmentation was used to divide sampling locations into eight landform elements based on profile and plan curvature, slope gradient and specific dispersal area. Orthic Humic Regosols and Orthic Sombric Brunisols were predominant in upper slope positions, whereas gleyed subgroups of the main soil orders were commonly found in the concave, lower slope positions. Lower, concave slope positions generally had lesser sand and coarse fragment contents, greater silt, organic carbon and 137Cs contents, and greater depth to C horizon and to bedrock than upper, convex slope positions. In contrast, A horizon thickness, clay content, soil pH and soil test P showed little relationship to landscape position. Landform segmentation was effective in characterizing the spatial distribution of soil loss at the study site, as indicated based on 137Cs content, and of soil taxa. However, the resulting landform elements had generally small differences in parameters such as SOC, sand, silt and clay content, which are commonly considered important in agricultural production. The landscape examined in this study appears to be dominated by soil loss and the closely related homogenizing effects of intensive tillage for potato production. The properties that continue to show a clear relationship to landform position are largely remnant properties (e.g., depth to bedrock or to the C horizon), whose pattern reflects a stronger hydrological and/or pedological control. The results provide further evidence that human-induced changes in soil can fundamentally alter the natural pattern of soil distribution in the landscape, even over relatively short (i.e., 100 years) time scales.

Ecological descriptions of pine mushroom ( Tricholoma magnivelare) habitat and estimates of its extent in northwestern British Columbia

Twenty-one sites known to be highly productive pine mushroom ( Tricholoma magnivelare [Peck] Redhead) habitat were described in northwest British Columbia. Soils were well to very rapidly drained and generally coarse in texture, often with a high coarse fragment content and thin forest floor. Western hemlock ( Tsuga heterophylla [Raf.] Sarg.) was consistently the dominant tree species, and lodgepole pine ( Pinus contortavar. latifolia Engelm) was frequently, though not always, present in the tree layer. Plant communities typically featured sparse herb and shrub layers, and a high coverage of mosses. Using the British Columbia biogeoclimatic system of ecosystem classification, all sites in the interior cedar hemlock forests were classified as the (01) Hw-step moss site series, submesic phase, and in the coastal western hemlock forests, as the (03) HwPl-feathermoss site series. Four separate areas of interior cedar hemlock forests, encompassing approximately 60,000 ha were assessed using air photography for the described (01) Hw-step moss submesic habitat. The extent of the submesic habitat across study areas ranged from 4.3 to 21.5% of the hemlock forests. The relatively low areal extent of these valuable forests demonstrated the need to better protect and manage the pine mushroom resource.

Using time domain reflectometry in stony forest soil

Forest soils often contain many large coarse fragments making it difficult to insert probes to measure soil water content. The ability of time domain reflectometry (TDR) to give reliable measurements of water content in soil with up to 40% coarse fragments was evaluated at a site in the southern interior of British Columbia, Canada. A commercial time domain reflectometer was used with 0.3-, 0.5- and 0.75-m-long probes to measure soil water content of the profile and layers within the profile. A probe had a shorting diode at the surface and two 3-mm-diameter stainless steel rods inserted vertically, 30 mm apart, as the waveguide. Diverging rods or profile discontinuities resulted in erroneous readings that required a review of the recorded signals and recalculation the travel time. Soil physical and hydrologic soil properties were determined and the soil calibrated for TDR. An accuracy of ±0.02 m3m−3 was obtained with measurement of soil bulk density and minimizing probe and travel time errors. Variation in water content between probes reflected the variability in coarse fragment content; however, the ranking of the probes stayed constant with time and rates of change were similar between probes. One standard deviation on the measured change in the volume of water between measurement days for the 0 to 0.5 m depth was ±6 mm (n = 20), equivalent to 0.012 m3m−3. Measurements of water content of the layers had one standard deviation of 0.02 m3m−3. Key words: Time domain reflectometry, forest hydrology, soil water content, water balance

Soil-Site Relations for Trembling Aspen in Northwest Ontario

Abstract Past harvesting in Northwest Ontario has produced increased regeneration and increased forest areas supporting trembling aspen stands, resulting in greatly increased utilization of aspen. Thus there is a critical need to accurately estimate site quality and growth and yield for trembling aspen and for identifying productive sites where more intensive aspen forest management can be practiced. Soil-site relations were studied using 95 plots located in mature, fully stocked, evenaged, undisturbed trembling aspen stands. On each plot site index (SIBH50) estimation was based on stem analysis of three to five dominant and codominant trees. Each plot also had soil profile descriptions and soil analyses for four major soil horizons (A, B, BC, C). Plots were located on morainal soils, glaciofluvial soils, and lacustrine soils. Multiple regression analyses showed: (a) for morainal soils site index was correlated (adj R² = 0.63) to depth to a root restricting layer, silt plus clay content of the A horizon, and coarse fragment content of the C horizon; (b) for glaciofluvial soils site index was correlated (adj R² = 0.64) to depth to a root restricting layer and to drainage class: and (c) for lacustrine soils site index was correlated (adj R² = 0.65) to depth to mottles and to clay content of the C horizon. Results are applicable only to medium and good sites where mature, fully stocked, merchantable trembling aspen stands commonly occur. North. J. Appl. For. 15(3):146-153.

Rocky Mountain forest soils: Evaluating spatial variability using conventional statistics and geostatistics

Spatial variability of soils is a landscape attribute which soil scientists must identify and understand if they are to construct useful soils maps. This paper describes the spatial variability of soils in a forested watershed in the Medicine Bow Mountains, Wyoming, using both conventional statistics and geostatistics. Principle Components Analysis indicated that flow accumulation and aspect were the two terrain attributes that most economically described terrain variability. Thickness of A and B horizons, organic carbon and solum coarse fragments were variable in the study area (CVs of 40 to 58%). Simple correlation and regression analyses suggested there were no statistically significant relationships between soil properties (texture, pH, coarse fragments, organic carbon content) and terrain attributes (elevation, slope gradient, slope shape, flow accumulation, aspect). Geostatistical analysis indicated thickness and coarse fragment contents of the A and B horizons, and solum thickness were spatially independent variables; however, pH, organic carbon content, and solum coarse fragment content were spatially correlated. Spatial variability was described by both linear (pH and organic carbon content) and spherical (solum coarse fragment) models. Use of geostatistics provided insight into the nature of variability in soil properties across the landscape of the Libby Creek watershed when conventional statistics (analysis of variance and regression analysis) did not. Key words: Rocky Mountains, Medicine Bow Mountains, forest soils, spatial variability, principle component analysis, geostatistics

Forest site-quality estimation using Forest Ecosystem Classification in Northwestern Ontario

Site index for jack pine, black spruce and trembling aspen was found to be poorly related to soil types described in the Northwestern Ontario Forest Ecosystem Classification (NWO FEC). Statistical analyses showed that average site indices for most soil types and groupings of soil types were not significantly different from each other.Site index varies greatly within presently defined NWO FEC soil types because certain soil and topographic features that are closely related to site index vary greatly within soil types or are not well described by the NWO FEC soil types. These critical soil features have been identified by soil-site studies that show features most closely related to site index usually are surface soil features found within the effective rooting zone of forest trees. These critical features include depth to bedrock, depth to root restricting soil layers, and coarse fragment content and texture of surface soil horizons.Site-quality research in Northwestern Ontario is closely integrated with the NWO FEC program, thus future NWO FEC soil classifications probably will use results from our soil-site research as a basis for soil type revisions. The result will be future soil types that are more closely related to forest site quality and thus to the capability of forest land to produce tree growth.

Effects of coarse-fragment content and size on soil erosion under simulated rainfall

Farmers have long considered coarse fragments a hindrance in potato production. Rock picking or crushing has become a routine operation. Using simulated rainfall events and runoff-erosion plots (1 m × 1 m), the effects of coarse-fragment content (0, 7, 15 and 25% by volume) and size (1.0–1.9, 1.9–5.1 and 5.1–7.6-cm diam) on runoff, infiltration and soil loss were evaluated on an Orthic Dystric Brunisol. Study objectives were to quantify the influence of coarse fragments on soil erosion and to convert these relationships into mathematical equations for use with existing models to predict soil loss. Although there were only marginal increases in infiltration and reductions in runoff attributable to increasing content and size of coarse fragments, the rate of soil loss from the control was higher than that from all other treatments. In general, the rate of soil loss decreased with increasing content and size of coarse fragments. The effects of content and size of coarse fragments on soil-loss reduction, either individually or in combination, were expressed mathematically with correlation coefficients greater than 0.82. The study also revealed that for a given volumetric coarse-fragment content, the percentage surface cover increased with increasing coarse-fragment size. This finding has important practical implications because most reporting of coarse fragments is done on the basis of volume rather than percentage surface cover. Key words: Rock content, rock size, rainfall simulator, infiltration, soil loss

Sample size for determination of coarse fragment content in a stony soil

Particle size analysis of soils containing coarse fragments requires sufficient amounts of soil material. We tried to quantify the sample volume for coarse fragment measurements in a Rendzina soil with more than 50% coarse fragment content. A monolith of 50 cm × 80 cm was excavated to a depth of 160 cm, hardened with an epoxy resin and cut into six cross sections. The coarse fragment contents were determined on the cross sections by counting the aerial fractions belonging to the fine earth, fine gravel and gravel classes. Additionally, 24 samples with a volume of 3.2 to 4.5 1 were sieved to determine the coarse fragment content. The contents estimated from the cross sections equalled the contents measured with particle size analysis. The data were evaluated in terms of the representative elementary area and volume. The coarse fragment content as a function of the sampling size exhibited the features of the representative elementary volume graph. The side length of the representative elementary area ranged from 11 to 19 cm. The estimated representative elementary volume ranged from 400 to 2 100 cm 3.

Estimating total soil mass, nutrient content, and trace metals in soils under a low elevation spruce-fir forest

The concentration, contents, and distribution of nutrients, metals, and soil materials were quantified at the Howland Integrated Forest Study (HIFS) site in eastern Maine. The site is a mature, low-elevation spruce-fir forest on Podzolic soils developed from dense basal till. Standard morphologically based soil sampling and quantitative soil pits were both used to characterize the soil component of this ecosystem. Vertical trends in nutrient concentrations at the site were largely governed by the distribution of organic matter. Standard morphological soil sampling techniques tended to overestimate soil pools of labile cationic nutrients and C, and underestimate trace metals and P, as a result of underestimations of coarse fragment content. These discrepancies can be critical if extrapolations for nutrients, metals, and C are made using existing databases to regional or global scales.Key words: Forest soils, spruce-fir, quantitative pits, sample size

Water Content, Bulk Density, and Coarse Fragment Content Measurement in Forest Soils

Water Content, Bulk Density, and Coarse Fragment Content Measurement in Forest Soils

Vertical root distribution in relation to soil properties in New Jersey Pinelands forests

Vertical distribution of root density (length per unit soil volume) and abundance (length per unit ground surface area) to a depth of 1.5 m or to the depth of the water table and their relationships with soil properties and tree basal area were examined in 36 soil profiles of pine-oak and oak-pine forests of the New Jersey Pinelands. Soil morphology were almost uniform within the forest type and characterized by the presence of high coarse fragment contents in the C horizon in oak-pine uplands; by the spodic B horizon and water table in the C horizon in pine-oak lowlands; by the sandy soil throughout the profile in pine-oak uplands; and by the firm argillic B horizon in pine-oak plains. Root density decreased from ranges of 44423–133369 m m-3 in the 0–5 cm depth in all the forest types to 1900–5593 m m-3 in the 100–150 cm depth in all the forest types except in pine-oak lowlands. Total profile root density and abundance was in the order: oak-pine uplands>pine-oak lowlands>pine-oak uplands>pine-oak plains. Root density correlated positively with organic C, total N, water soluble P, exchangeable Ca, Mg, K, Al, Fe, and cation exchange capacity, and negatively with bulk density, coarse fraction content, and pH, whereas root abundance correlated positively with organic C, total N, water soluble P, exchangeable Ca, Mg, K, and Fe, and negatively with bulk density. No correlation existed between root density and abundance with tree basal area. Higher root density in the E horizon of oak-pine uplands as compared to the other forest types was associated with high nutrient content; higher root density in the C horizon of pine-oak lowlands was associated with a shallow water table beneath the horizon; and lower root densities in the B and C horizons of pine-oak plains were associated with the presence of a firm clay layer in the B horizon.