Woodland Herb Research Articles

Oak savanna vegetation response to layered restoration approaches: Thinning, burning, and grazing

Temperate savannas are unique, biodiverse ecosystems that have undergone extensive habitat conversion globally. In the midwestern United States, 99% of historic oak savanna area has been lost. Most remaining patches of savanna are degraded due to woody encroachment following the removal of both fire and large herbivore disturbances from the landscape. Restoring degraded savanna remnants is challenging because we lack an understanding of how to best apply contemporary restoration tools to mimic historic disturbance dynamics. To that end, we evaluated the outcomes of ongoing oak savanna restorations that have received a gradient of restoration actions: 1) no management, 2) tree thinning, 3) thinning + burning, and 4) thinning + burning + cattle grazing. We assessed several metrics of restoration success including canopy, shrub, herbaceous, and non-native cover, herbaceous diversity, and plant community composition. We found that layering restoration approaches achieved certain, but not all, structural vegetation goals. Compared to no management, thinning and fire successfully increased canopy openness, herbaceous cover, and herbaceous diversity, but had the unwanted effect of increased shrub cover. The addition of low-intensity cattle grazing did not improve structural outcomes. We also found that each restoration treatment left a unique signature on understory plant community composition. Unmanaged and thin-only treatments were characterized by tree saplings and woodland herbs, while burned and grazed treatments were defined by shrubs and savanna-associate species. We conclude that reintroducing multiple disturbances does not guarantee the successful restoration of disturbance-dependent ecosystems such as oak savannas. Restoration outcomes are not dictated by how many management approaches are applied, but rather, the nuances of how they are applied such as burn season and livestock density.

Myrmecochorous plants and their ant seed dispersers through successional stages in temperate cove forests

Anthropogenic disturbance can decrease woodland diversity in the species-rich herbaceous layer of eastern deciduous forests, and ant-dispersed (myrmecochorous) plants may be particularly affected due to their limited ability to re-colonise secondary forests. Consequently, we predicted that myrmecochorous plants and their keystone seed-dispersing ants would increase with time since the last disturbance, as reflected by young, middle or mature forest successional stage. Specifically, we hypothesized that myrmecochore abundance and richness would be relatively lowest in the youngest forests, moderate in middle-aged forests and highest in mature forests. We also hypothesized that experimentally introducing ant bait in a regular pattern, as might be expected from intact species-rich myrmecochore communities, would elicit greater ant foraging interest than intermittent baiting, as might be expected in recently disturbed depauperate myrmecochore communities. We found the highest myrmecochore plant abundance in mature forests, but we found the same for herbaceous plants overall. Moreover, regular and intermittent bait offerings elicited similar overall ant responses. The observational results suggested that myrmecochorous plants respond to forest successional stage as do other woodland plants, and our experimental results suggest that disrupted seed delivery by myrmecochores did not affect Aphaenogaster abundance or foraging behaviour. As such, the myrmecochore communities studied here appeared as resilient as other woodland herbs, and seed-dispersing ants did not appear dependent on myrmecochore plant communities. Indeed, given the relatively high myrmecochore richness and abundance across our study sites, forest type (e.g., rich cove forest) might better predict myrmecochore success than successional stage.

Relative contribution of ancient woodland indicator and non‐indicator species to herb layer distinctiveness in ancient semi‐natural, ancient replanted, and recent woodland

AbstractQuestionsThe floristic distinctiveness of ancient woodland relative to recent woodland is commonly measured by Ancient Woodland Indicator (AWI) species richness. However, focussing on a pre‐defined subset of species means that wider community‐level differences may be overlooked. Can ancient semi‐natural, ancient replanted, and recent woodland herb layer communities be distinguished by alpha, beta, and gamma diversity? How are any differences partitioned across AWI and non‐AWI species communities?LocationCotswolds, southwest UK.MethodsTo quantify AWI and non‐AWI responses to stand history in ancient semi‐natural, ancient replanted, and recent woodland, we conducted floristic surveys of 45 sites. Using a modelling approach, we tested the relative and additive contribution of alpha‐scale AWI and non‐AWI species richness to woodland distinctiveness. Ordination was applied to analyse beta species composition distinctiveness, and multilevel pattern analysis was used to examine which species were significant contributors to gamma‐scale richness differences.ResultsAWI species richness models significantly distinguished ancient semi‐natural woodland from both ancient replanted and recent woodland at the alpha scale. For the classification of ancient semi‐natural woodland and recent woodland, the hierarchical inclusion of non‐AWI alpha richness resulted in a superior and more significant model. AWI gamma richness was numerically similar for all three woodland categories, whereas non‐AWI was more varied. AWI and non‐AWI species composition showed significant beta diversity differences among all woodland types, with six species being significant drivers of differences.ConclusionsOur results have revealed previously undetected complexity in the contributions of AWI and non‐AWI species to floristic distinctiveness of ancient woodland. In addition to traditional AWI species, the non‐AWI assemblage also exhibited a sensitivity to habitat continuity that: (a) adds weight to the argument that ancient woodland is floristically distinct from recent woodland; and (b) provides a useful measure of success for ancient replanted woodland restoration.

A battle of the sexes? Sex ratio and performance at small scales in dioecious Mercurialis perennis

Mercurialis perennis is a dioecious clonal woodland herb. Its male-biased shoot sex ratio may result from differential selection (with skewed genet sex ratio) and/or differential performance (fairly even genet sex ratio but skewed shoot sex ratio since male clones grow more vigorously or have a higher flowering propensity). To test both scenarios, a total of 1024 shoots were mapped and excavated in five 1 m2 plots in an old-growth forest in northeastern Germany. SSR genotyping revealed a less skewed intrinsic male:female shoot sex ratio (1.6) and a nearly even genet sex ratio. The sexes showed intermingling rather than sexual niche segregation. Most of the 36 genets found split into numerous independent units (merigenets). A slight sexual size dimorphism (SSD) was found: male clones possess on average more shoots, have longer stolons and a higher proportion of flowering shoots. Analyses of resource allocation patterns showed 1.5–2.8 times higher costs for sexual reproduction (dry mass, nitrogen) for females. Males invest surplus resources into leaves and stolons, accentuating the SSD; although for genets the difference may be smaller due to the higher flowering rate of males (53% vs. 34%). Photosynthetic performance, deduced from rapid light curves measured with a portable fluorometer, was similar for both sexes, especially in spring; the main challenge being the transformation from light to shade plant with tree foliation. Our data indicate that differential performance accounts for the male bias in shoot sex ratio; competition between sexes is unlikely given the strongly intermingled clones.

Planting clonal shade-tolerant herbs in young urban woodlands—Effects of compost on plant growth, flowering and survival

Rich herbaceous layers supply important ecosystem functions and amenity values in urban woodlands. However, due to poor dispersal and recruitment, typical woodland herbs often remain absent in woodlands established on post-agricultural and post-industrial sites, especially in fragmented urban landscapes. Efficient methods for active restoration of the herbaceous layer are therefore needed. In a plantation experiment in an 11-year-old oak stand established on post-agricultural land just outside Malmö City, southern Sweden, this study investigated the effects of compost addition and weed control on post-planting survival, growth and flowering of three typical shade-tolerant woodland herb species: Galium odoratum, Lamiastrum galeobdolon and Stellaria holostea. Removal of competing weed vegetation did not affect plant performance, but compost addition dramatically increased growth and flowering of all three species during the first two growing seasons, and also increased survival in S. holostea. This positive treatment effect probably derived from a more suitable top soil structure and a higher soil moisture in the compost treatment. We conclude that combined use of planting and composting is an effective method for rapid achievement of profusely flowering carpets of summer-green woodland herbs, which can provide important amenity values in the many woodlands established in and around cities in north-west Europe in recent decades. The method may also be applicable in other woodland restoration projects, where it can promote colonisation by typical shade-tolerant woodland herb species.

Cryptic indirect effects of exurban edges on a woodland community

Exurban development (e.g., second homes) in woodlands spreads urban land use impacts beyond suburbs, but because exurban developments often retain many components of original ecosystem structure—such as a forest canopy rather than open lawn—their ecological impacts may be underestimated. Changes in seed‐dispersing ant behavior prompted by exurban land use, such as edge avoidance, may pose deleterious impacts on the woodland plants (myrmecochores) they disperse, and hence the floristic diversity of exurban forests. We examined the effects of exurbanization on seed‐dispersing ant nesting and foraging, seed retrieval, dispersal direction and subsequent impact on myrmecochores. We used a matrix of forested and exurbanized habitats to test whether (1) exurban edges decrease ant nest colonization and seed foraging, (2) ants disperse seeds away from exurban edges, and (3) consequently, there is lower ant‐dispersed plant abundance nearer exurban edges. We found that exurban development poses little impact on keystone seed‐dispersing ants because they foraged, colonized and thrived in fragmented woodland habitats as well as they did in intact forests. Exurban edges changed ant behavior, however, so that they generally moved seeds toward forest interiors, and, hence, away from edges. Corresponding to this behavioral change, we found that ant‐dispersed plants declined with proximity to edges, whereas other woodland herbs with dispersal modes other than ants were unaffected. Exurbanization poses little threat to seed‐dispersing ant viability, but, by changing foraging patterns (specifically, limiting the directionality of dispersal), it indirectly threatens the plants they disperse. Edge effects on biota commonly are associated with cascades through abiotic resources, but we show a deleterious biotic cascade between exurban edge, keystone ants and herbaceous plants. Species‐mediated services, such as seed dispersal and pollination, are key resources, and assessing the full consequences of land use change therefore necessitates evaluation of impacts on biotic interactions.

Spatiotemporal variation in deer browse and tolerance in a woodland herb.

Herbivory can shape the dynamics of plant populations, including effects on survival and reproduction, and is in turn affected by environmental factors that vary in space and time. White-tailed deer are significant herbivores in North America that have been broadly documented to affect plant reproductive success. If variation in the frequency and impact of herbivory by deer correlates with a broad-scale latitudinal gradient, climactic effects may be important for shaping plant-herbivore interactions, Alternatively, a lack of broad-scale gradients would suggest local factors such as plant community composition and deer densities are affecting herbivory. To investigate broad-scale patterns of deer herbivory, we examined the frequency and reproductive consequences of deer browse over three years in 17 populations of Campanulastrum americanum spanning the latitudinal extent of its range. Even though deer are overabundant throughout the range of C. americanum, we found spatiotemporal variation in deer browse frequency (0-0.96, mean 0.46) and its effects on plant reproductive success. The four southernmost populations experienced high levels of herbivory, and were responsible for generating a negative relationship between latitude and herbivory. In general, patterns of variation in the frequency and impact of herbivory across the entire latitudinal gradient pointed to the importance of local rather than broad-scale factors. Within a population, deer consumed larger plants. Across many populations and years, average fitnesses of browsed and uneaten plants were similar, suggesting that plants are tolerant to browse. However, since large plants have greater reproductive success and are more likely to be browsed, tolerance may be influenced by plant size. When plant size was accounted for, most populations did not fully compensate for browsing. There was no relationship between browsing intensity and tolerance, suggesting that browsing may be too variable to consistently select for tolerance, or that increases in deer density are too recent for increased tolerance to evolve.

Phylogenetic Relationships within Uvularia (Colchicaceae) Based on Morphology

Abstract The five species of bellworts in the genus Uvularia are common woodland herbs endemic to eastern North America. Two previous studies conducted phylogenetic analyses of Uvularia based on matK and rbcL gene sequences. The objective of this study was to create a phylogeny for Uvularia based on 18 qualitative morphological characters and 14 quantitative characters. Two phylogenetic analyses were performed, one including all 32 characters and one excluding the 14 quantitative characters. Strict consensus trees from the two analyses had the same topology and were congruent with published molecular phylogenies, supporting two sections of the genus.

Migration of vascular plant species to a recent wood adjoining ancient woodland

Woodland communities can be restored by natural succession in sites adjoining ancient woodlands which can act as seed sources for trees, shrubs and woodland herbs. The influence of dominant tree species and the distance from an adjacent ancient oak-hornbeam woodland upon the floristic composition of species in a recent pine wood planted on dry rendzina soil were studied. It was found that, in spite of a 52-year long succession, the border between woods was sharp and the composition of species in the recent wood were significantly different than in the adjacent ancient woodland. Canonical correspondence analysis (CCA) showed that the distance to the ancient woodland had a significant influence on species distributions in the recent wood. The numbers of species from the <em>Querco-Fagetea</em> class, vegetatively reproducing species and myrmecochores decreased with this distance, whereas the numbers of anemochores increased. The migration rate of many woodland species, calculated on occurrence of the farthest individuals was very slow, varying from 0.0 m year<sup>-1</sup> to 0.38 m year<sup>-1</sup>. The restoration of the field layer vegetation in the studied pine wood was much slower than in recent deciduous woods on rich and moist soils where the migration rate of some species exceeded 1.50 m year<sup>-1</sup>. Recent woods adjacent to ancient woodlands can be more effectively colonised by woodland species only when they are dominated by broad-leaved trees with quickly decomposing litter, and the spatial continuity of these woods persists for a long period.

각시족도리풀(Asarum misandrum)의 유전적 다양성 및 집단 구조

ABSTRACT: Genetic variation in Asaum misandrum, a woodland herb in Korea, was investigated based on alloz-yme analysis with starch gel electrophoresis. All of previously reported populations in Korea were sampled andseven loci from six enzymes were analyzed. Overall genetic variation of A. misandrum population showed con-siderably high levels of genetic variation within the species (A = 2.05, P = 71.4, H E = 0.294). A positive F IS value of A. misandrum indicated overall deficiency of heterozygotes, and a low F ST value (0.112) meant very lit-tle differentiation among populations. Factors contributing to the high levels of genetic diversity found withinpopulations of A. misandrum include population maintenance via wide distribution range from Korea to Japanand primarily outcrossing breeding system. Although it showed moderate genetic diversity level, most habitatsof the species were scattered and discontinuous. Besides, low numbers of individuals were found in the mosthabitats and individuals are collected frequently from the wild due to the unique shape of the flowers as well asthe rarity of the species. Thus, there is a need to set up a reasonable conservation strategies including the main-tenance mechanism of genetic diversity of A. misandrum.

Effects of land‐use history and current management on ancient woodland herbs in Western Hungary

AbstractQuestionsAt least half of the European woodland is recent and most stands have been under heavy management since the Industrial Revolution. Woodland herbs have adapted to the conditions of the forest interior and many species occur at lower frequencies in recent habitats as well as in young stands. We compared herbaceous plant composition of forests with different land‐use history and looked for life‐history traits that could be responsible for the differences.LocationBakony Mountains, Western Hungary, Central Europe.MethodsAdjacent old ancient, young ancient and post‐agricultural recent forest stands were surveyed in the submontane beech zone in Western Hungary. Frequency data were recorded for herbaceous plants, indicator species analysis was carried out and trait‐based species groups were identified.ResultsSpecies composition differed among all three categories. The most profound difference was in the occurrences of ancient forest species (species with low dispersal ability and early flowering). These were most abundant in old ancient forests, while three species were entirely missing from recent stands. Young stands were dominated by few shade‐tolerant herbs and lacked most ancient forest species. Post‐agricultural woodland was largely dominated by competitive species.ConclusionsCurrent forest management as well as past agricultural use influenced herb composition. Reintroduction of ancient forest herbs might be necessary in the recent forests.

Environmental Heterogeneity and Interspecific Interactions Influence Nest Occupancy By Key Seed-Dispersing Ants

The complex interplay between species along environmental gradients ultimately shapes their distributions and additional community interactions. Ant-mediated seed dispersal fails in the wettest habitat of deciduous forest in eastern North America, and we examine whether this pattern corresponds with colony distributions for seed-dispersing ants and associated heterogeneity in abiotic and biotic variables. Specifically, we used spatial variation in soil moisture, temperature and diffuse light along natural habitat gradients and experimentally manipulated soil moisture gradients to examine ant habitat selection. We also examined niche segregation between effective (Aphaenogaster spp.) and ineffective (Lasius alienus Foerster) seed-dispersing ants across these environmental gradients. Whereas most research links ant foraging and nesting with temperature gradients, we find niche segregation between Aphaenogaster spp. and L. alienus by soil moisture along naturally occurring gradients and in experimentally irrigated upland habitat. The failure of Aphaenogaster spp. to occupy the wettest habitats, where L. alienus is present, is consistent with observed seed dispersal failure in these habitats. These results indicate that environmental heterogeneity drives niche segregation between effective (Aphaenogaster spp.) and ineffective (L. alienus) seed dispersers so each occupies distinct habitat. Most forest understory plants rely on ants for seed dispersal. Our research implies that climate-mediated interactions between effective and ineffective seed dispersing ant species may structure the microhabitat distributions for woodland herbs.

Context dependency of the allelopathic effects of Lonicera maackii on seed germination

Allelopathic effects of invasive plants on native flora may be mitigated by the abiotic and biotic environment into which the allelochemicals are released. Lonicera maackii (Amur honeysuckle), an invasive plant of the eastern deciduous forest, suppresses seed germination in laboratory assays. We investigated how L. maackii leachate interacts with abiotic conditions and with the soil microbial community. First, we tested the effects of leaf extract from L. maackii on germination of the native woodland herb, Blephilia hirsuta, under different light and soil conditions. We found that germination of Blephilia hirsuta was reduced by L. maackii extract, but abiotic conditions did not interact with this effect. We also tested the effects of leaf extract on germination of five native woodland species and L. maackii placed in sterile or live soil. There was an overall suppressive effect of L. maackii extract on itself and the other five native species tested. However, L. maackii extract interacted with live soil in ways that differed with the species being tested and, in some cases, changed over time. Our results indicate that allelopathic potential of L. maackii shows context dependency with respect to soil microorganisms and native species identity but not to light conditions or soil type. Our results imply that restoration of invaded areas may require active reintroduction of species sensitive to allelopathy in live soil. Further, laboratory assays of allelopathy should consider the interaction of allelochemicals with biotic and abiotic conditions to more accurately predict the impacts of allelopathy on plant communities.

Multiple glacial refugia and postglacial colonization routes inferred for a woodland geophyte, Cyclamen purpurascens: patterns concordant with the Pleistocene history of broadleaved and coniferous tree species

The phylogeographical history of mid-altitude woodland herbs that depend on moist and shaded forest habitats is poorly understood. Here, we analysed the genetic structure of Cyclamen purpurascens, a mountainous calcicolous perennial, to test hypotheses regarding its glacial survival in single or multiple refugia and postglacial colonization routes, and to explore how they are congruent with the histories inferred for temperate trees and other mountainous herbs. We gathered AFLP data and chloroplast DNA sequences (trnD-trnT region) from 68 populations spanning the entire distribution range (the Jura Mountains, Alps, western Carpathians, Dinarides). Both genetic markers revealed two main phylogeographical groups (phylogroups) in C. purpurascens. Additionally, AFLP data detected a more detailed structure of five phylogroups: two widespread, showing east−west geographical separation, and three local ones, restricted to somewhat disjunct, marginal regions of the species range. We suggest that C. purpurascens survived the last glaciation in two main regions, the foothills of the Southern Limestone Alps and the Karst area of the north-western Dinarides, and possibly also in microrefugia in the Western Carpathians. The glacial persistence and colonization routes of this woodland herb are highly concordant with those inferred for several temperate trees, especially the European beech. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 741–760.

BLACK COHOSH RHIZOME AND PHYTOCHEMICAL PRODUCTION IN RESPONSE TO SHADING, SPACING, AND AGE

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): A New Look at Medicinal and Aromatic Plants Seminar BLACK COHOSH RHIZOME AND PHYTOCHEMICAL PRODUCTION IN RESPONSE TO SHADING, SPACING, AND AGE

Biological flora of Central Europe: Ceratocapnos claviculata (L.) Lidén

The eu-oceanic therophytic woodland herb Ceratocapnos claviculata has been expanding north- and eastwards into north temperate and subcontinental regions during the past decades. The rapid range expansion of the species may be an example of a species which is strongly profiting from global change. Against this background, in the present paper we review the taxonomy, morphology, distribution, habitat requirements, life cycle and biology of the species.

For she that hath, to her shall be given…Implications of flowering in Anemone nemorosa L.

We looked for life-history trade-offs between flowering, vegetative growth and somatic maintenance in the common woodland herb Anemone nemorosa. A.nemorosa forms a horizontal rhizome system consisting of previously formed annual segments and terminated by a flowering or non-flowering shoot. Resources acquired by the aboveground parts are used for flowering, seed production, storage and growth of the annual segments. Resources stored in the rhizome during the growing period are used for preformation of buds, somatic maintenance between two growing periods and development of aboveground parts in the following spring. We hypothesised that the decision to invest in flower buds depends on the amount of resources stored in the recently formed annual segment. We also hypothesised a trade-off between flowering and segment growth and, finally, as a consequence, we expected individual rhizomes to alternate between the flowering and the non-flowering state. We found that segments producing flower buds were significantly longer than non-flowering segments, indicating that resource level influences the function of the preformed buds. Contrary to our expectations, we found flowering rhizomes produced longer annual segments than non-flowering rhizomes. We suggest the larger leaf area of flowering rhizomes and occasional abortion of flowers or seeds as possible mechanisms behind this pattern. Our study shows that even though the decision to produce a flower bud is taken in another time-frame than that in which the actual flowering and fruiting takes place, an ostensibly inexpedient decision is changed to a neutral or even an advantageous incident.

Temperature cues phenological synchrony in ant-mediated seed dispersal

Species-specific climate responses within ecological communities may disrupt the synchrony of co-evolved mutualisms that are based on the shared timing of seasonal events, such as seed dispersal by ants (myrmecochory). The spring phenology of plants and ants coincides with marked changes in temperature, light and moisture. We investigate how these environmental drivers influence both seed release by early and late spring woodland herb species, and initiation of spring foraging by seed-dispersing ants. We pair experimental herbaceous transplants with artificial ant bait stations across north- and south-facing slopes at two contrasting geographic locations. This use of space enables robust identification of plant fruiting and ant foraging cues, and the use of transplants permits us to assess plasticity in plant phenology. We find that warming temperatures act as the primary phenological cue for plant fruiting and ant foraging. Moreover, the plasticity in plant response across locations, despite transplants being from the same source, suggests a high degree of portability in the seed-dispersing mutualism. However, we also find evidence for potential climate-driven facilitative failure that may lead to phenological asynchrony. Specifically, at the location where the early flowering species (Hepatica nobilis) is decreasing in abundance and distribution, we find far fewer seed-dispersing ants foraging during its fruit set than during that of the later flowering Hexastylis arifolia. Notably, the key seed disperser, Aphaenogaster rudis, fails to emerge during early fruit set at this location. At the second location, A. picea forages equally during early and late seed release. These results indicate that climate-driven changes might shift species-specific interactions in a plant–ant mutualism resulting in winners and losers within the myrmecochorous plant guild.

Dispersal, not Understory Light Competition, Limits Restoration of Iowa Woodland Understory Herbs

Plant community restoration may be limited by the inability of target species to disperse to a restoration site (i.e. dispersal limitation) or by the failure of species to establish once seeds do arrive (i.e. establishment limitation). Seed additions attempt to overcome dispersal limitations; however, seed additions may fail due to establishment limitations resulting from competition with pre‐existing vegetation. We tested whether dispersal and/or competition with the pre‐existing understory limited restoration of 22 native deciduous woodland herbs in Iowa, United States. We employed an experiment that varied seed mix composition to contain either high densities of forbs or graminoids, coupled with clipping of pre‐existing understory vegetation to reduce competition for light during establishment. We found strong support for dispersal limitations, as seed additions increased understory richness by 4–8 species/m2. This was due to the addition of species from the seed mix, not modification to the naturally occurring plant community, which suggests the existence of an open (unsaturated) plant community. Most species in our seed mix established at high rates and there was no effect of seed mix (high vs. low density of graminoid vs. forb seeds) on the richness or persistence of species added by seed. Light competition with the pre‐existing understory vegetation did not limit establishment. We recommend simple seed sowing to restore the majority of species in our study; 19/22 species readily established. Our results support the use of less expensive seed mixes containing high density of gramoids, relative to forbs.

Suppression of the Woodland Herb Senna hebecarpa by the Invasive Grass Microstegium vimineum

Biological invasions are associated with declining biodiversity in many ecosystems, but it is often unclear if invasions are directly responsible for such changes, or if invasions are a symptom of environmental degradation. In addition, the mechanism underlying the effects of many invasive species is unknown. To determine if invaders are driving changes in invaded communities, and to identify causal mechanisms, studies that manipulate the presence of invaders are needed. We experimentally introduced the invasive grass Microstegium vimineum into replicated field plots that had been planted with the native woodland herb Senna hebecarpa. After 3 y, we quantified Senna establishment, growth and reproduction. We then conducted a greenhouse experiment to determine if changes in Senna success were due to alteration of soil microbial communities or nutrient depletion in invaded plots. Microstegium-invaded plots had 74% fewer Senna plants and Senna growing in invaded plots were 21% shorter and weighed 64% less than in control plots. The proportion of Senna plants that reproduced was 67% lower and plants produced 78% fewer seeds on average in invaded than in control plots. In contrast to the field results, there were no differences in the growth of Senna when grown in Microstegium-invaded or control soil in the greenhouse, and the invasion treatment did not alter the effects of soil sterilization or fertilization. Further, we found no evidence that Microstegium success is determined by feedbacks with the soil community. Our results demonstrate that Microstegium has negative effects on a native species, but we found no evidence that the suppressive effects of Microstegium invasions are mediated by plant-soil interactions in invaded areas.