Polyphenol oxidase activity in subcellular fractions of tall fescue contaminated by polycyclic aromatic hydrocarbons

Understanding enzyme responses to contamination with persistent organic pollutants (POPs) is a key step in the elucidation of POP metabolic mechanisms in plants. However, there is little information available on enzyme activity in subcellular fractions of POP-contaminated plants. To our knowledge, this is the first study to investigate the activities of polyphenol oxidase (PPO) in cell fractions of plants under contamination stress from polycyclic aromatic hydrocarbons (PAHs) using a greenhouse batch technique. Three parameters, E(cell), E(cell-n), and P(cell), denoting the amount of PPO activity, cell fraction content-normalized PPO activity, and proportion of PPO activity in each cell fraction, respectively, were used in this study. Contamination with phenanthrene, as a representative PAH, at a relatively high level (>0.23 mg L?1) in culture solution generally stimulated PPO activity in tall fescue (Festuca arundinacea Schreb.) roots and shoots and their cellular fractions. The amount and distribution proportion of PPO activity in each cell fraction of phenanthrene-contaminated roots and shoots were (in descending order): cell solution > > cell wall > cell organelles. Cell solution was the dominant storage domain of PPO activity and contributed 84.0 and 82.8% of PPO activity in roots and shoots, respectively. The cell wall had the highest density of PPO activity in roots and shoots, based on the highest cell fraction content normalized PPO activity in this cell fraction. Our results provide new information on enzyme responses in plant intracellular fractions to xenobiotic POPs and fundamental information on within-plant POP metabolic mechanisms.     

Role of mycorrhizal fungi and phosphorus in the arsenic tolerance of basin wildrye

Revegetation of arsenic (As)-rich mine spoils is often impeded by the lack of plant species tolerant of high As concentrations and low nutrient availability. Basin wildrye [Leymus cinereus (Scribner & Merr.) A. L?ve] has been observed to establish naturally in soils with elevated As content and thus may be useful for the stabilization of As-contaminated soils. An experiment was conducted to evaluate how variable phosphorus (P) concentrations and inoculation with site-specific arbuscular mycorrhizal fungi influence As tolerance of basin wildrye. Basin wildrye was grown in sterile sand in the greenhouse for 16 weeks. Pots of sterile sand were amended to create one of four rates of As (0, 3, 15, or 50 mg As kg(-1)), two rates of P (3 or 15 mg P kg(-1)), and +/-mycorrhizal inoculation in a 2 x 4 x 2 factorial arrangement. After 16 weeks of growth, plants were harvested, shoots and roots thoroughly washed, and the tissue analyzed for total shoot biomass, total root and shoot As and P concentrations, and degree of mycorrhizal infection. Basin wildrye was found to be tolerant of high As concentrations allowing for vigorous plant growth at application levels of 3 or 15 mg As kg(-1). Arsenic was sequestered in the roots, with 30 to 50 times more As in the roots than shoots under low P conditions. Mycorrhizal infection did not confer As tolerance in basin wildrye nor did mycorrhizal fungi influence biomass production. Phosphorus concentrations of 15 mg kg(-1) effectively inhibited As accumulation in basin wildrye. Basin wildrye has the potential to be used for stabilization of As-rich soils while minimizing exposure to grazing animals following reclamation.     

接种根瘤菌和菌根真菌对三叶草生长及对土壤Pb2+吸收的影响

采用盆栽实验,设计了不接种(CK)、接种根瘤菌、接种丛枝菌根真菌、双接种根瘤菌和菌根真菌4种处理,探讨了三叶草的生长情况及对土壤中Pb2+吸收的影响。结果表明:三叶草对Pb具有一定的吸收能力,两次采样中,CK处理三叶草Pb浓度分别为15.38mg/kg和15.57mg/kg,均为各处理中最高;接种根瘤菌可明显提高三叶草生物量,接种菌根真菌能明显减少三叶草对土壤中Pb的吸收。接种根瘤菌和菌根真菌减少三叶草对Pb2+的吸收和向地上部运输。     

Clonal differences in mercury tolerance, accumulation, and distribution in willow

This study was performed to investigate mercury (Hg) tolerance, accumulation, and translocation within the genus Salix for the potential use of this plant to remediate Hg-contaminated sites. Six clones of willow (Salix spp.) were tested on tolerance to Hg by treating plants grown in solution culture with 0 to 15 microM HgCl(2). Results showed that willow had a large variation in its sensitivity to Hg. However, the accumulation and translocation of Hg to shoots was similar in the eight tested willow clones as shown by cold vapor atomic absorption spectrometry analysis when plants were treated with 0.5 microM HgCl(2) in a nutrient solution. The majority of total Hg accumulated was localized to the roots, whereas only 0.45 to 0.62% of the total Hg accumulated via roots was translocated to the shoots. Thus, the root system is the main tissue of willow that accumulates Hg and the majority of the Hg in the root system (80%) was bound in the cell wall.     

丛枝菌根在矿区生态重建中的应用及其前景分析

目前国内外矿山复垦研究的新热点是应用现代微生物工艺技术加速新覆盖土的改性与熟化。在总结分析国内外微生物复垦技术研究现状的基础上,对丛枝菌根应用于矿区复垦的前景进行了展望。加快这项技术的应用研究,对拓宽我国科学复垦技术研究领域、提高土地复垦率具有重要意义。     

Copper release from chemical root-control baskets in hardwood tree production

The City of Montreal, Canada, evaluated the environmental impact and usefulness of in-ground copper (Cu)-treated baskets in controlling root growth of hardwood trees in nursery culture. Using baskets planted with 5-yr-old Norway maple (Acer platanoides L.) trees, the amount and temporal pattern of Cu release from the basket surface into soil was determined for two copper formulations: Cu metal powder and Cu(OH)2. Release of both Cu formulations from the basket surface decreased exponentially over time, with Cu concentration at the basket surface dropping to 2% of the initial Cu applied by the end of the second field season. Total Cu content increased significantly in the soil around the baskets (from 7 to 28 mg Cu kg(-1) soil) and in the baskets (from 7 to 50-70 mg Cu kg(-1) soil) over the two years of the study. Three levels of phosphorus application (33, 66, and 100% of the regular nursery rate of 465 kg ha(-1) yr(-1)) did not affect release of Cu from the basket surface. The release of Cu metal at 28 and 105 d in the field was significantly increased by inoculation with the symbiotic arbuscular mycorrhizal fungus (AMF) Glomus intraradices Schenck & Smith; however, AMF inoculation had no affect on Cu(OH)2 release. Trees grown in Cu-treated baskets and inoculated with G. intraradices had similar colonization to non-inoculated trees, suggesting that inoculation was not very effective and that AMF inoculum was already present in the root ball of the trees at planting. After two years, copper basket-grown trees had significantly less root colonization than isolated control trees growing in the open field. This strongly suggests that conditions inside the baskets were not favorable to AMF.     

Simulation of phytoremediation of a TNT-contaminated soil using the CTSPAC model

Knowledge of water movement in the plant-xylem system and contaminant bioavailability in the soil environment is crucial to evaluate the success of phytoremediation practices. This study investigated the removal of 2,4,6-trinitrotoluene (TNT) from a contaminated sandy soil by a single poplar (Populus fastigiata) tree through the examinations of temporal variations of xylem water potential, root water uptake, and soil TNT bioavailability. A mathematical model, CTSPAC (Coupled Transport of water, heat, and solutes in the Soil-Plant-Atmosphere Continuum), was modified for the purpose of this study. The model was calibrated using laboratory measurements before its application. Our simulations show that the xylem water potential was high in the roots and low in the leaves with a potential head difference of 3.55 cm H2O, which created a driving force for water flow and chemical transport upward from the roots through the stem to the leaves. The daily average root water uptake rate was 25 cm3 h(-1) when an equilibrium condition was reached after 24 h. Our simulations further reveal that no TNT was found in the stem and leaves and only about 1% of total TNT mass was observed in the roots due to the rapid biodegradation and transformation of TNT into its daughter products. About 13% of the soil TNT was removed by the poplar tree, resulting mainly from root uptake since TNT is a recalcitrant compound. In general, the soil TNT bioavailability decreased with time due to the depletion of soil solution TNT by the poplar tree. A constant bioavailability (i.e., 3.1 x 10(-6)) was obtained in 14 d in which the soil TNT concentration was about 10 mg L(-1). Our study suggests that CTSPAC is a useful model to simulate phytoremediation of TNT-contaminated sites.     

Particulates, not plants, dominate nitrogen processing in a septage-treating aerated pond system

In pond and wetland systems for wastewater treatment, plants are often thought to enhance the removal of ammonium and nitrogen through the activities of root-associated bacteria. In this study, we examined the role of plant roots in an aerated pond system with floating plants designed to treat high-strength septage wastewater. We performed both laboratory and full-scale experiments to test the effect of different plant root to septage ratios on nitrification and denitrification, and measured the abundances of nitrifying bacteria associated with roots and septage particulates. Root-associated nitrifying bacteria did not play a significant role in ammonium and total nitrogen removal. Investigations of nitrifier populations showed that only 10% were associated with water hyacinth [Eichhornia crassipes (Mart.) Solms] roots (at standard facility plant densities equivalent to 2.2 wet g roots L(-1) septage); instead, nitrifiers were found almost entirely (90%) associated with suspended septage particulates. The role of root-associated nitrifiers in nitrification was examined in laboratory batch experiments where high plant root concentrations (7.4 wet g L(-1), representing a 38% net increase in total nitrifier populations over plant-free controls) yielded a corresponding increase (55%) in the non-substrate-limited nitrification rate (V(max)). However, within the full-scale septage-treating pond system, nitrification and denitrification rates remained unchanged when plant root concentrations were increased to 7.1 g roots L(-1) (achieved by increasing the surface area available for plants while maintaining the same tank volume). Under normal facility operating conditions, nitrification was limited by ammonium concentration, not nitrifier availability. Maximizing plant root concentrations was found to be an inefficient mechanism for increasing nitrification in organic particulate-rich wastewaters such as septage.     

Rhizospheric mobilization and plant uptake of radiocesium from weathered micas: I. Influence of potassium depletion

Potassium depletion in the soil solution around plant roots promotes the root uptake of radiocesium. However, it can also induce the transformation of mica through the release of interlayer K. In bulk soil, the formation of frayed edge sites (FES) with a high selectivity for Cs adsorption is usually related with mica weathering. We studied the effect of K level in the nutrient solution on the root-induced weathering of phlogopite as well as on the root uptake of radiocesium by willow (Salix viminalis L. var. Orm). The willows were grown for 7 wk in column lysimeters filled with a quartz-phlogopite mixed substrate continuously irrigated with nutrient solutions differing in K concentration (0-2 mM). From a potassium supply of 0.4 mM downward, we observed a decrease in root uptake of potassium as well as an increase in (i) potassium release from phlogopite, (ii) degree of transformation of phlogopite into vermiculite, and (iii) root uptake of radiocesium. Increasing K depletion had thus two effects: a decrease of the root uptake of potassium and an increase of phlogopite weathering in the rhizosphere, both of which promoted the root uptake of radiocesium.     

The role of nitrilotriacetate in copper uptake by tobacco

In growth chamber experiments we studied the effect of nitrilotriacetate (NTA) on Cu uptake by tobacco (Nicotiana tabacum L.). Plants were exposed for 6 d to 126 microM Cu and 500 microM NTA in nutrient solutions without and with 10 g L(-1) montmorillonite. Approximately seven times less Cu was dissolved in the montmorillonite solutions than in the nutrient solutions alone. In the absence of NTA, montmorillonite effectively competed with plant roots for Cu, although Cu remained bound to the roots. Nitrilotriacetate increased Cu uptake and translocation into shoots of tobacco by a factor of 3.5 from the nutrient solution and by a factor of 26 from the montmorillonite nutrient solution. Neither growth reduction nor any other visible sign of Cu toxicity was found in the presence of NTA with Cu concentrations of 190 mg kg(-1) in the shoots. In the absence of NTA, high Cu concentrations in root samples led to a brownish discoloration of the roots.     

Mycorrhizae increase arsenic uptake by the hyperaccumulator Chinese brake fern (Pteris vittata L.)

Chinese brake fern (Pteris vittata L.) is a hyperaccumulator of arsenic (As) that grows naturally on soils in the southern United States. It is reasonable to expect that mycorrhizal symbiosis may be involved in As uptake by this fern. This is because arbuscular mycorrhizal (AM) fungi have a well-documented role in increasing plant phosphorus (P) uptake, P and As have similar chemical properties, and ferns are known to be colonized by AM fungi. We conducted a factorial greenhouse experiment with three levels of As (0, 50, and 100 mg kg(-1)) and P (0, 25, and 50 mg kg(-1)) and with and without Chinese brake fern colonized by a community of AM fungi from an As-contaminated site. We found that the AM fungi not only tolerated As amendment, but their presence increased frond dry mass at the highest As application rate. Furthermore, the AM fungi increased As uptake across a range of P levels, while P uptake was generally increased only when there was no As amendment. These data indicate that AM fungi have an important role in arsenic accumulation by Chinese brake fern. Therefore, to effectively phytoremediate As-contaminated soils, the mycorrhizal status of ferns needs to be taken into account.     

Metal decontamination of tannery solid waste using <Emphasis Type="Italic">Tagetes patula</Emphasis> in association with saprobic and mycorrhizal fungi

A greenhouse trial was conducted to investigate the role of mycorrhizal and resistant fungi on heavy metal phytoextraction from different concentrations of tannery solid waste amended soil (10, 20, 50, and 100%) by Tagetes patula. The four treatments included were, the control (C) without any inoculum, mycorrhizal (M) inoculated with strongly mycorrhizal roots of Cynodon dactylon, fungal (F) inoculated with Trichoderma pseudokoningii and the combined inoculation with both mycorrhizal and fungal inocula (M + F). The dual inoculation increased plant biomass and phytoextraction ability of plant for metals like Cd, Cr, Cu, and Na. Plants given only fungus (F) and only mycorrhizal (M) treatment also showed significant growth rate as compared with control treatment. The statistical analysis of data indicated synergistic interaction between mycorrhizal and fungal inoculum promoting high biomass and enhanced metal phytoextraction. Thus using more than one group of rhizosphere fungi in association with a high biomass producing plant may be employed for rendering tannery solid waste free of metals.     

Relationship between metal speciation in soil solution and metal adsorption at the root surface of ryegrass

The total metal content of the soil or total metal concentration in the soil solution is not always a good indicator for metal availability to plants. Therefore, several speciation techniques have been developed that measure a defined fraction of the total metal concentration in the soil solution. In this study the Donnan Membrane Technique (DMT) was used to measure free metal ion concentrations in CaCl(2) extractions (to mimic the soil solution, and to work under standardized conditions) of 10 different soils, whereas diffusive gradients in thin-films (DGT) and scanning chronopotentiometry (SCP) were used to measure the sum of free and labile metal concentrations in the CaCl(2) extracts. The DGT device was also exposed directly to the (wetted) soil (soil-DGT). The metal concentrations measured with the speciation techniques are related to the metal adsorption at the root surface of ryegrass (Lolium perenne L.), to be able to subsequently predict metal uptake. In most cases the metal adsorption related pH-dependently to the metal concentrations measured by DMT, SCP, and DGT in the CaCl(2) extract. However, the relationship between metal adsorption at the root surface and the metal concentrations measured by the soil-DGT was not-or only slightly-pH dependent. The correlations between metal adsorption at the root surface and metal speciation detected by different speciation techniques allow discussion about rate limiting steps in biouptake and the contribution of metal complexes to metal bioavailability.     

Root exudation, phosphorus acquisition, and microbial diversity in the rhizosphere of white lupine as affected by phosphorus supply and atmospheric carbon dioxide concentration

White lupine (Lupinus albus L.) was used as a phosphorus (P)-efficient model plant to study the effects of elevated atmospheric CO(2) concentrations on (i) P acquisition, (ii) the related alterations in root development and rhizosphere chemistry, and (iii) the functional and structural diversity of rhizosphere microbial communities, on a P-deficient calcareous subsoil with and without soluble P fertilization. In both +P (80 mg P kg(-1)) and -P treatments (no added P), elevated CO(2) (800 micromol mol(-1)) increased shoot biomass production by 20 to 35% and accelerated the development of cluster roots, which exhibit important functions in chemical mobilization of sparingly soluble soil P sources. Accordingly, cluster root formation was stimulated in plants without P application by 140 and 60% for ambient and elevated CO(2) treatments, respectively. Intense accumulation of citrate and increased activities of acid and alkaline phosphatases, but also of chitinase, in the rhizosphere were mainly confined to later stages of cluster root development in -P treatments. Regardless of atmospheric CO(2) concentrations, there was no significant effect on accumulation of citrate or on selected enzyme activities of C, N, and P cycles in the rhizosphere of individual root clusters. Discriminant analysis of selected enzyme activities revealed that mainly phosphatase and chitinase contributed to the experimental variance (81.3%) of the data. Phosphatase and chitinase activities in the rhizosphere might be dominated by the secretion from cluster roots rather than by microbial activity. Alterations in rhizosphere bacterial communities analyzed by denaturing gradient gel electrophoresis (DGGE) were related with the intense changes in root secretory activity observed during cluster root development but not with elevated CO(2) concentrations.     

Cobalt distribution and speciation: effect of aging, intermittent submergence, in situ rice roots

The speciation and distribution of Co in soils is poorly understood. This study was conducted using x-ray absorption spectroscopy (XAS) techniques to examine the influence of soluble cobalt in the +2 oxidation state (Co[II]) aging, submergence-dried cycling, and the presence of in vivo rice roots on the speciation and distribution of added Co(II) in soils. In the aging and submerged-dried cycling studies, Co was found to be associated with Mn oxide fraction (23 to 100% of total Co) and Fe oxide fractions (0 to 77% of total Co) of the soils as either Co(II) species or a mixed Co(II), and Co in the +3 oxidation state (Co[III]) species. The surface speciation of Co in the Mn oxide fraction suggests an innersphere complex was present and the speciation of Co in the Fe oxide fraction was an innersphere surface complex. The in vivo root box experiments showed similar Co speciation in the Mn oxide fraction (13 to 76% of total Co) as the aging and submerged-dried cycling studies. However, the Fe oxide fraction of the soil was unimportant in Co retention. A significant amount (24 to 87% of total Co) of the Co in root box treatments was identified as a Co precipitate. The importance of this finding is that in the presence of rice roots, the Co is redistributed to a Co precipitate. This work confirmed earlier macroscopic work that Mn oxides are important in the sequestration of Co in soils and the influence of roots needs to be taken into account when addressing Co speciation. The information gained from this study will be used to improve models to predict the lability and hence the availability of Co in terrestrial environments.     

Ryegrass cover crop effects on nitrate leaching in spring barley fertilized with 15NH415NO3

Cover crops are a management option to reduce NO3 leaching under cereal grain production. A 2-yr field lysimeter study was established in Uppsala, Sweden, to evaluate the effect of a perennial ryegrass (Lolium perenne L.) cover crop interseeded in barley (Hordeum vulgare L.) on NO3-N leaching and availability of N to the main crop. Barley and ryegrass or barley alone were seeded in mid-May 1992, in lysimeters (03-m diam. x 1.2-m depth) of an undisturbed, well-drained, sandy loam soil. Fertilizer N was applied at the same time as labeled l5NH415NO3 (10 atom % 15N) at a rate of 100 kg N ha(-1). In 1993, barley was reseeded in May in the lysimeters but with nonlabeled NH4NO3 and no cover crop (previous year's cover crop incorporated just prior to seeding). Barley yields and total and fertilizer N uptake in Year 1 (1992) were unaffected by cover crop. Total aboveground N uptake by the ryegrass was 28 kg ha(-1) at the time of incorporation the following spring. Recovery of fertilizer-derived N in May 1993 was about 100%; 53% in soil, 46% in barley, <2% in ryegrass, and negligible amounts in leachate. In May 1994, the corresponding figures were: 32% in soil, <3% in barley, and, again, negligible amounts in leachate. The cover crop reduced concentrations of NO3-N in the leachate considerably (<5 mg L(-1), compared with 10 to 18 mg L(-1) without cover crop) at most sampling times from November 1992 to April 1994, and reduced the total amount of NO3-N leached (22 compared with 8 kg ha(-1)).     

Rhizospheric mobilization and plant uptake of radiocesium from weathered micas: II. Influence of mineral alterability

Acute K depletion in the rhizosphere can lead to increased root uptake of radiocesium. Two processes can govern this increase: the very low uptake of potassium and the weathering of Cs-fixing clay minerals. Their respective importance is, however, unknown. We investigated the effects of these processes on radiocesium mobilization by roots of willow (Salix viminalis L.) from three micas: muscovite, biotite, and phlogopite. Willows were grown in a mixed quartz-mica substrate with the three respective (134)Cs-contaminated micas as sole sources of potassium and radiocesium. After 7 wk of plant growth, the micas were partially weathered. The degree of mica weathering and the prevalent potassium concentration in the solution increased in the order muscovite (5-11 microM K) < biotite (25-32 microM K) < phlogopite (25-35 microM K). The mobilization and root uptake of radiocesium were negligible with muscovite but increased in the same order. These results show that mica weathering directly and chiefly governs the mobility of radiocesium in K-depleted rhizosphere soil. The low mobility of trace Cs in the muscovite rhizosphere is linked with the dioctahedral character of this mica, and hence to its very low alterability.     

Impact of ectomycorrhizal colonization of hybrid poplar on the remediation of diesel-contaminated soil

Infection by ectomycorrhizal (ECM) fungi may benefit hybrid poplar growing in contaminated soils by providing greater access to water and nutrients and possibly protecting the trees from direct contact with toxic contaminants. The objective of this research was to determine the effect of colonization of the ECM fungus Pisolithus tinctorius (Pers.) Coker & Couch on hybrid poplar fine root production, biomass and N and P uptake when grown in diesel-contaminated soil (5000 mg diesel fuel kg soil(-1)). Commercially available Mycogrow Tree Tabs were the source of inoculum. A minirhizotron camera was used to provide the data necessary for estimating fine root production. Colonization of hybrid poplar roots (P. deltoides x [P. laurifolia x P. nigra] cv. Walker) by P. tinctorius increased total fine root production in diesel-contaminated soil to 56.58 g m(-2) compared to 22.59 g m(-2) in the uncolonized, diesel-contaminated treatment. Hybrid poplar leaf N and P concentrations were significantly greater in the diesel-contaminated/ECM-colonized treatment compared to the diesel-contaminated/uncolonized treatment after 12 wk, while significantly less diesel fuel was recovered from the soil of the uncolonized treatment compared to the colonized treatment. Both planted treatments removed more contaminants from the soil than an unplanted control. Significantly greater concentrations of total petroleum hydrocarbons (TPH) were found sequestered in hybrid poplar root/fungal-sheath complexes from the colonized treatment compared to the roots of the uncolonized treatment. The results of this study indicate that over a 12-wk growth period, ECM colonization of hybrid poplar in diesel-contaminated soils increased fine root production and whole-plant biomass, but inhibited removal of TPH from the soil.     

EFFECTS OF WOODY VEGETATION ON SANDY LEVEE INTEGRITY1

he influence of woody vegetation on the reliability of a sandy levee was investigated using field data in seepage and slope stability analyses. Field data were collected from selected sites within a 10-km segment of a channel levee on the Sacramento River near Elkhorn, California. Root architecture and distribution were determined using the profile-wall method in which root cross sections were exposed in the vertical wall of an excavated trench. Transects running both parallel and perpendicular to the crest of the levee were excavated at six sites. Each site was dominated by different plant species: five sites were adjacent to trees or woody shrubs, while one supported only herbaceous growth. Lateral plant roots were primarily restricted to, and modified, the near-surface soil horizons to a depth of approximately 1 meter. Root area ratios (RARs) did not exceed 2.02 percent and generally decreased exponentially with depth. At depths greater than 20 cm, mean RARs for sites dominated by wood species were not significantly different from the mean RAB for the herbaceous site. No open voids clearly attributable to plant roots were observed. Roots reinforced the levee soil and increased shear resistance in a measurable manner. Infinite slope and circular arc stability analyses were performed on the landward and riverward slopes under different hydraulic loading conditions. Infinite slope analyses indicated increasing root area ratio from 0.01 percent to 1 percent increased the factor of safety from less than one to more than seven. Circular arc analyses indicated that even the lower measured root concentrations sufficed to increase safety factors for arcs with maximum depths of about 1 m from less than one to about 1.2. Our findings suggest that allowing woody shrubs and small trees on levees would provide environmental benefits and would enhance structural integrity without the hazards associated with large trees such as wind-throwing.     

Variation in root density along stream banks

While it is recognized that vegetation plays a significant role in stream bank stabilization, the effects are not fully quantified. The study goal was to determine the type and density of vegetation that provides the greatest protection against stream bank erosion by determining the density of roots in stream banks. To quantify the density of roots along alluvial stream banks, 25 field sites in the Appalachian Mountains were sampled. The riparian buffers varied from short turfgrass to mature riparian forests, representing a range of vegetation types. Root length density (RLD) with depth and aboveground vegetation density were measured. The sites were divided into forested and herbaceous groups and differences in root density were evaluated. At the herbaceous sites, very fine roots (diameter < 0.5 mm) were most common and more than 75% of all roots were concentrated in the upper 30 cm of the stream bank. Under forested vegetation, fine roots (0.5 mm < diameter < 2.0 mm) were more common throughout the bank profile, with 55% of all roots in the top 30 cm. In the top 30 cm of the bank, herbaceous sites had significantly greater overall RLD than forested sites (alpha = 0.01). While there were no significant differences in total RLD below 30 cm, forested sites had significantly greater concentrations of fine roots, as compared with herbaceous sites (alpha = 0.01). As research has shown that erosion resistance has a direct relationship with fine root density, forested vegetation may provide better protection against stream bank erosion.