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Permafrost thawing could increase soil contaminant mobilization in the environment. Our objective was to quantify metal accumulation capacities for plant species and functional groups common to Alaskan military training ranges where elevated soil metal concentrations were likely to occur. Plant species across multiple military training range sites were collected. Metal content in shoots and roots was compared to soil metal concentrations to calculate bioconcentration and translocation factors. On average, grasses accumulated greater concentrations of Cr, Cu, Ni, Pb, Sb, and Zn relative to forbs or shrubs, and bioconcentrated greater concentrations of Ni and Pb. Shrubs bioconcentrated greater concentrations of Sb. Translocation to shoots was greatest among the forbs. Three native plants were identified as candidate species for use in metal phytostabilization applications. Elymus macrourus, a grass, bioconcentrated substantial concentrations of Cu, Pb, and Zn in roots with low translocation to shoots. Elaeagnus commutata, a shrub, bioconcentrated the greatest amounts of Sb, Ni, and Cr, with a low translocation factor. Solidago decumbens bio-concentrated the greatest amount of Sb among the forbs and translocated the least amount of metals. A combination of forb, shrub, and grass will likely enhance phytostabilization of heavy metals in interior Alaska soils through increased functional group diversity.

Permafrost thawing could increase soil contaminant mobilization in the environment. Our objective was to quantify metal accumulation capacities for plant species and functional groups common to Alaskan military training ranges where elevated soil metal concentrations were likely to occur. Plant species across multiple military training range sites were collected. Metal content in shoots and roots was compared to soil metal concentrations to calculate bioconcentration and translocation factors. On average, grasses accumulated greater concentrations of Cr, Cu, Ni, Pb, Sb, and Zn relative to forbs or shrubs, and bioconcentrated greater concentrations of Ni and Pb. Shrubs bioconcentrated greater concentrations of Sb. Translocation to shoots was greatest among the forbs. Three native plants were identified as candidate species for use in metal phytostabilization applications.

Many ectomycorrhizal fungi (EMF) are generalists, but most plant genera that form ectomycorrhizas have at least some fungal partners that are specific to that host genus. Because shared mycorrhizal fungi mediate plant community interactions, host preference has implications for plant succession and competition. We studied the EMF of oaks (Quercus spp.) and pines (Pinus spp.) in a forest in northern Florida, USA, focusing on symbionts shared with longleaf pine (Pinus palustris Mill.). Longleaf pine is an important species in the southeastern USA, both for timber plantations and for restoring savanna and woodland habitat. However, we found no research on the composition of naturally occurring EMF on longleaf pine roots. A lower proportion of EMF operational taxonomic units (OTUs) were found colonizing both oaks and pines than expected, providing evidence of host preference within the community. Although most EMF were detected only on either oaks or pines, the OTUs found on both tended to be frequently occurring and abundant. Cenococcum OTUs were found to be significantly associated with oaks, an unexpected finding as this genus is widespread, with a broad host range. These results suggest that host preference of EMF may structure EMF communities and therefore influence ecosystem effects of mycorrhizal networks.

Permafrost thaw is expected to alter biogeochemistry and hydrology, potentially increasing the mobility of soil constituents. Northern latitude boreal forests where permafrost thaw is occurring also experience extreme changes in day length during the growing season. As the effects of photoperiod on plant uptake of soil constituents or interactions with the rhizosphere are unknown, our objective was to determine these interactions with three plant species from different functional groups. A tree, forb, and grass common to military training ranges in this region were grown in soil spiked with or without lead, antimony, or 2,4-dinitrotoluene and grown under 16, 20, or 24 h of light. Plant biomass, soil constituent uptake, and rhizosphere bacterial communities were compared between treatments. Photoperiod had no effect on plant uptake of any soil constituent or on rhizosphere community, indicating that plants and their associated microbial communities adapted to this environment are resilient to extremes in photoperiod. Lead uptake was not significant in any plant species and had no effect on the rhizosphere. Antimony increased the percentage composition of Saprospirales in the rhizospheres of two of the three plants, indicating an interaction between this bacterial order and antimony. Antimony uptake by white spruce (Picea glauca) was considerable, with a mean concentration of 1731 mg kg−1 in roots, while mean shoot concentration was only 155 mg kg−1, indicating its potential to phytostabilize this heavy metal. Although antimony had the strongest impact on the rhizosphere bacterial community, it was also readily accumulated by the grass and tree.

Lespedeza cuneata is a non-native invasive legume that alters the soil bacterial community, associates promiscuously with rhizobia, and benefits more from rhizobial interactions compared to coexisting native Lespedeza in North America. We tested the hypothesis that native congeners differ in their nodule bacteria associations compared to L. cuneata. Plots with high L. cuneata invasion, low L. cuneata invasion with native Lespedeza species present, and uninvaded plots where native Lespedeza species existed without L. cuneata were sampled. Nodules were collected from all Lespedeza species present, and Chamaecrista fasciculata, a common native annual legume. Bacterial DNA from nodules was isolated and sequenced. Nodule bacterial composition differed significantly between hosts. L. cuneata nodules contained high frequencies of rhizobial DNA and low bacterial diversity, while native Lespedeza nodules contained lower rhizobial frequencies and higher non-rhizobial bacterial diversity. Specific non-rhizobial bacterial groups exhibited strong associations with native legumes and uninvaded sites. Significant differences exist in the nodule bacterial composition between native legumes and an introduced congener. The mechanism(s) and ecological importance of these differences remain unknown. These differences in bacterial associations could influence not only the competitive ability of the invader, but recovery of invaded sites as well.

Lespedeza cuneata is an introduced legume that is invasive in the tallgrass prairie system and open woodlands of North America. This system includes native Lespedeza species that coexist with L. cuneata, including L. capitata and L. virginica. Previous research has indicated that L. cuneata exudates have profound influences on soil biological functions. The goal of this current research was to identify and then compare exudate chemicals from L. cuneata, L. capitata, L. virginica, and common tallgrass prairie grasses. Exudates from Lespedeza species were found to be distinct from the grasses. In particular, L. cuneata and, to a lesser extent, a subset of L. virginica could be differentiated based on the presence of five unique compounds. Two low molecular weight compounds were identified via gas chromatography/mass spectrometry (GC/MS) and tentatively identified as benzophenone and 1,4-diacetylbenzene. Three higher molecular weight compounds were identified by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS), with possible relationships to a 3 sterol, phosphatidylglycerol, and the 19-nor analogues of vitamin D. The relative abundance of these compounds were found to be greater in the invasive species, L. cuneata, than in the native noninvasive species, L. virginica. These results are an integral step in further understanding through chemical exudation how L. cuneata can be benefiting from greater rhizobial associations.

Arbuscular mycorrhizal fungi (AMF) have been implicated in non-native plant invasion success and persistence. However, few studies have identified the AMF species associating directly with plant invaders, or how these associations differ from those of native plant species. Identifying changes to the AMF community due to plant invasion could yield key plant-AMF interactions necessary for the restoration of native plant communities. This research compared AMF associating with coexisting Bromus tectorum, an invasive annual grass, and Artemisia tridentata, the dominant native shrub in western North America. At three sites, soil and root samples from Bromus and Artemisia were collected. Sporulation was induced using trap cultures, and spores were identified using morphological characteristics. DNA was extracted from root and soil subsamples and amplified. Sequences obtained were aligned and analyzed to compare diversity, composition, and phylogenetic distance between hosts and sites. Richness of AMF species associated with Artemisia in cultures was higher than AMF species associated with Bromus. Gamma diversity was similar and beta diversity was higher in AMF associated with Bromus compared to Artemisia. AMF community composition differed between hosts in both cultures and roots. Two AMF species (Archaeospora trappei and Viscospora viscosum) associated more frequently with Artemisia than Bromus across multiple sites. AMF communities in Bromus roots were more phylogenetically dispersed than in Artemisia roots, indicating a greater competition for resources within the invasive grass. Bromus associated with an AMF community that differed from Artemisia in a number of ways, and these changes could restrict native plant establishment.

Arbuscular mycorrhizal fungi (AMF) are an important driver of plant community assembly, and as such may be critical for restoring plant communities. Previous work has shown that as plant communities develop, AMF density is a good predictor of what type of plant community is supported. However, interactions between plants, particularly facultative hosts, and AMF are often assumed from plant growth responses and lack concomitant AMF growth response data. We examined both plant and AMF responses in association using early- and mid-seral plant hosts and a homogenous AMF community. The goal was to determine how variable interactions are between facultative plant hosts and an AMF community. Plant responsiveness was measured using field soil with and without AMF. AMF density was measured by observing root colonization by AMF in a bioassay host plant grown in soils trained by the individual host plant species used in the plant responsiveness study. Plant species studied were highly variable in their interactions with AMF, and mutualisms, parasitisms, amensalisms and commensalisms were all prevalent. The presence of certain AMF facilitators may have a strong founder effect on plant communities and, where such feedbacks exist, identifying and utilizing these key interactions might facilitate the restoration of degraded ecosystems.

Non-native species are hypothesized to decrease native species establishment and cover crops are hypothesized to decrease non-native species abundance. Although many studies have compared invaded to non-invaded habitats, relatively few studies have experimentally added non-native species to directly examine their effects. In a greenhouse mesocosm experiment, we tested the effects of non-native forbs (Melilotus officinalis, Verbascum thapsus, and Lespedeza cuneata), a proposed C3 grass cover crop (Pascopyrum smithii), and a commonly seeded non-native C3 grass (Bromus inermis) on the establishment of target native C4 prairie grass species. All treatments contained the same seed density of target C4 species and were begun on bare soil collected from the field. The legume M. officinalis strongly decreased the abundance of all other species, species diversity, and light and soil moisture levels. Surprisingly, M. officinalis took up relatively large amounts of labeled nitrogen (15N) from the soil early in its development, but M. officinalis fixed nitrogen, thus increasing nitrogen in biomass nearly fivefold by the end of the study. We found few effects of either C3 grass species on non-native forbs or C4 target species, but seeded P. smithii did increase species diversity. Non-native plants therefore impeded native C4 grass establishment through long-lasting effects of target species seedbank depletion (death of most target seedlings) and altered nutrient availability. The effects of M. officinalis were not reduced by the presence of a cover crop.

A garbage processing technology has been developed that sterilizes and separates inorganic and organic components of municipal solid waste. A study was initiated to evaluate the uncomposted organic byproduct of this process as a soil amendment for establishing native prairie grasses on disturbed Army training lands. The waste was incorporated into sandy soils at Fort Benning Military Reservation on two sites: a moderately degraded and a highly degraded soil. The waste material was applied at rates of 0, 17.9, 35.8, 71.6, and 143 Mg ha 21 and seeded with native prairie grasses to assess its effects on vegetation for twogrowingseasons, withanadditionalunseededcontroltreatmentfor comparison to natural recovery. The addition of uncomposted waste increasedpercentcompositionandbasalcoverofswitchgrass(Panicum virgatum L.) at both sites and percent composition of big bluestem (Andropogon gerardii Vitman) at one site. Indiangrass [Sorghastrum nutans (L.) Nash] was negatively affected by the addition of the waste material at both sites. Biomass in the 143 Mg ha 21 treatment increased 4180% compared to the seeded control at the highly degraded site. Plant uptake of P and Na increased at both sites and an apparent Fe toxicity problem was alleviated at the highly disturbed site with increasing application rates. Because perennial grass establishment improved so dramatically with increasing application rates, land application of this uncomposted waste material could be considered a viable and beneficial alternative to current waste management practices for degraded Army lands.

Cheatgrass is a highly invasive winter annual grass that is most aggressive in the semi-arid steppe region of western North America. In this region, cheatgrass invasion becomes so severe that virtual monocultures can result. Due to its strategy for growth from autumn to spring, cheatgrass remains active during winter months when most native vegetation is dormant. This shift in host activity could be important for beneficial soil microbes, particularly the arbuscular mycorrhizal fungi (AMF), as they are adapted for coincidental growth with host plants. Many native plant species that are utilized for restoring areas invaded by cheatgrass associate with AMF, so any reduction in these symbiotic fungi could reduce the successful establishment of desirable plant species. Although cheatgrass is recognized as a facultative associate of AMF, its associations with AMF across seasons and throughout its lifespan are not known. We measured AMF colonization of cheatgrass roots from soon after germination through senescence. We found that cheatgrass remains colonized throughout its life. Colonization drops dramatically once soil temperatures approach freezing, but was highest late in the growth cycle of cheatgrass during flowering and seed set. Colonization by AMF never attained levels comparable to highly mycorrhizal plant species. This indicates that cheatgrass is a poor host for AMF throughout its life, and long-term dominance by cheatgrass could alter AMF in soils. Restoring highly invaded sites quickly following invasion might reduce the negative effects of cheatgrass on this important soil microbial community.

The spatial scale on which microbial communities respond to plant invasions may provide important clues as to the nature of potential invader-microbe interactions. Lespedeza cuneata (Dum. Cours.) G. Don is an invasive legume that may benefit from associations with mycorrhizal fungi; however, it has also been suggested that the plant is allelopathetic and may alter the soil chemistry of invaded sites through secondary metabolites in its root exudates or litter. Thus, L. cuneata invasion may interact with soil microorganisms on a variety of scales. We investigated L. cuneata-related changes to soil bacterial and fungal communities at two spatial scales using multiple sites from across its invaded N. American range. Using whole community DNA fingerprinting, we characterized microbial community variation at the scale of entire invaded sites and at the scale of individual plants. Based on permutational multivariate analysis of variance, soil bacterial communities in heavily invaded sites were significantly different from those of uninvaded sites, but bacteria did not show any evidence of responding at very local scales around individual plants. In contrast, soil fungi did not change significantly at the scale of entire sites, but there were significant differences between fungal communities of native versus exotic plants within particular sites. The differential scaling of bacterial and fungal responses indicates that L. cuneata interacts differently with soil bacteria and soil fungi, and these microorganisms may play very different roles in the invasion process of this plant.

Background and Aims Lespedeza cuneata (Dum. Cours.) G. Don is an invasive legume that displaces populations of native N. American congeners. Our aims are to determine the growth benefits of different rhizobacterial strains for L. cuneata and native Lespedeza virginica (L.) Britton, and to determine if these strains influence competition between these plants.