Showing papers on "Native plant published in 2016"

Invasive plant species are locally adapted just as frequently and at least as strongly as native plant species

Abstract: Summary Concerns over the ecological impacts of invasive alien plant species have generated great research interest in understanding the mechanisms that underlie the capacity of such plants to occupy a broad range of habitats. It has been repeatedly suggested that rapid evolution of local adaptation to novel environments may enable invasive plants to occupy a broad range of habitats. However, the classical Darwinian view on evolution by natural selection is that the process is slow and gradual, occurring over thousands of years. Invasive plants typically have a relatively short residence time in their introduced ranges (decades or just a few centuries). Besides the time constraint, founder effects (reduction in population size and genetic diversity) may also limit the capacity of invasive plants to rapidly evolve local adaption. Thus, invasive plants may be less likely than native plants to evolve local adaptation. Interestingly, however, an expanding body of literature documents the existence of local adaptation in invasive plant species within their exotic ranges. Here, we did a phylogenetically controlled meta-analysis to compare invasive and native plant species for differences in the frequency and magnitude of local adaptation. The meta-analysis was based on different experiments performed in various habitats including grasslands, steppes, deserts, forests, mountains, wetlands and dunes, and used a total of 134 plant species in 52 families. Forty seven of these species (in 24 families) are alien invaders in the region where the studies were undertaken, while the other 91 species (in 38 families) are native. On average, local plants performed better than foreign plants, and invasive plant species expressed local adaptation just as frequently, and at least as strongly as that exhibited by native plant species. An analysis performed while taking into account different plant life-history traits showed that self-incompatible invasive plants exhibited significantly higher frequencies of local adaptation than native plants characterized by the same breeding system. Synthesis. The present results support the suggestion that rapid evolution of local adaptation may enable invasive plant species to occupy a broad range of novel habitats.

Land use change and ecosystem service provision in Pampas and Campos grasslands of southern South America

Abstract: New livestock production models need to simultaneously meet the increasing global demand for meat and preserve biodiversity and ecosystem services. Since the 16th century beef cattle has been produced on the Pampas and Campos native grasslands in southern South America, with only small amounts of external inputs. We synthesised 242 references from peer-reviewed and grey literature published between 1945 and mid-2015 and analysed secondary data to examine the evidence on the ecosystem services provided by this grassland biodiversity hotspot and the way they are affected by land use changes and their drivers. The analysis followed the requirements of systematic review from the PRISMA statement (Moher et al 2009 Acad. Clin. Ann. Intern. Med. 151 264–9). The Pampas and Campos provide feed for 43 million heads of cattle and 14 million sheep. The biome is habitat of 4000 native plant species, 300 species of birds, 29 species of mammals, 49 species of reptiles and 35 species of amphibians. The soils of the region stock 5% of the soil organic carbon of Latin America on 3% of its area. Driven by high prices of soybean, the soybean area increased by 210% between 2000 and 2010, at the expense of 2 million ha (5%) of native grassland, mostly in the Pampas. Intensification of livestock production was apparent in two spatially distinct forms. In subregions where cropping increased, intensification of livestock production was reflected in an increased use of grains for feed as part of feedlots. In subregions dominated by native grasslands, stocking rates increased. The review showed that land use change and grazing regimes with low forage allowances were predominantly associated with negative effects on ecosystem service provision by reducing soil organic carbon stocks and the diversity of plants, birds and mammals, and by increasing soil erosion. We found little quantitative information on changes in the ecosystem services water provision, nutrient cycling and erosion control. We discuss how changing grazing regimes to higher forage allowance can contribute to greater meat production and enhancing ecosystem services from native grasslands. This would require working with farmers on changing their management strategies and creating enabling economic conditions. (Resume d'auteur)

Positive and Negative Impacts of Non-Native Bee Species around the World

Abstract: Though they are relatively understudied, non-native bees are ubiquitous and have enormous potential economic and environmental impacts. These impacts may be positive or negative, and are often unquantified. In this manuscript, I review literature on the known distribution and environmental and economic impacts of 80 species of introduced bees. The potential negative impacts of non-native bees include competition with native bees for nesting sites or floral resources, pollination of invasive weeds, co-invasion with pathogens and parasites, genetic introgression, damage to buildings, affecting the pollination of native plant species, and changing the structure of native pollination networks. The potential positive impacts of non-native bees include agricultural pollination, availability for scientific research, rescue of native species, and resilience to human-mediated disturbance and climate change. Most non-native bee species are accidentally introduced and nest in stems, twigs, and cavities in wood. In terms of number of species, the best represented families are Megachilidae and Apidae, and the best represented genus is Megachile. The best studied genera are Apis and Bombus, and most of the species in these genera were deliberately introduced for agricultural pollination. Thus, we know little about the majority of non-native bees, accidentally introduced or spreading beyond their native ranges.

Alien plant invasions and native plant extinctions: a six-threshold framework.

Abstract: CITATION: Downey, P. O. & Richardson, D. M. 2016. Alien plant invasions and native plant extinctions : a six-threshold framework. AoB PLANTS, 8:1-21, doi:10.1093/aobpla/plw047.

Slow recovery of tropical old-field rainforest regrowth and the value and limitations of active restoration

Abstract: There is current debate about the potential for secondary regrowth to rescue tropical forests from an otherwise inevitable cascade of biodiversity loss due to land clearing and scant evidence to test how well active restoration may accelerate recovery. We used site chronosequences to compare developmental trajectories of vegetation between self-organized (i.e., spontaneous) forest regrowth and biodiversity plantings (established for ecological restoration, with many locally native tree species at high density) in the Australian wet tropics uplands. Across 28 regrowth sites aged 1–59 years, some structural attributes reached reference rainforest levels within 40 years, whereas wood volume and most tested components of native plant species richness (classified by species’ origins, family, and ecological functions) reached less than 50% of reference rainforest values. Development of native tree and shrub richness was particularly slow among species that were wind dispersed or animal dispersed with large (>10 mm) seeds. Many species with animal-dispersed seeds were from near-basal evolutionary lineages that contribute to recognized World Heritage values of the study region. Faster recovery was recorded in 25 biodiversity plantings of 1–25 years in which wood volume developed more rapidly; native woody plant species richness reached values similar to reference rainforest and was better represented across all dispersal modes; and species from near-basal plant families were better (although incompletely) represented. Plantings and regrowth showed slow recovery in species richness of vines and epiphytes and in overall resemblance to forest in species composition. Our results can inform decision making about when and where to invest in active restoration and provide strong evidence that protecting old-growth forest is crucially important for sustaining tropical biodiversity.

Conserving pollinators in North American forests: A review

Abstract: Bees and butterflies generally favor open forest habitats regardless of forest type, geographic region, or methods used to create these habitats. Dense shrub layers of native or nonnative species beneath forest canopies negatively impact herbaceous plant cover and diversity, and pollinators. The presence of nonnative flowers as a source of nectar, pollen, or larval food can have positive or negative effects on pollinators depending on the situation, but in cases where the nonnatives exclude native plants, the results are almost always negative. Roads and roadside corridors offer an opportunity to increase open, pollinator-friendly habitat even in dense forests by thinning the adjacent forest, mowing at appropriate times, and converting to native herbaceous plant communities where nonnative species have been planted or have invaded. Efforts to improve forest conditions for pollinators should consider the needs of specialist species and vulnerable species with small scattered populations. Conservation of bees and butterflies, as well as other pollinating species, in forested areas is important for most forest plant species, and forests may serve as reservoirs of pollinators for recolonization of surrounding habitats.

On-farm habitat restoration counters biotic homogenization in intensively managed agriculture.

Abstract: To slow the rate of global species loss, it is imperative to understand how to restore and maintain native biodiversity in agricultural landscapes. Currently, agriculture is associated with lower spatial heterogeneity and turnover in community composition (β-diversity). While some techniques are known to enhance α-diversity, it is unclear whether habitat restoration can re-establish β-diversity. Using a long-term pollinator dataset, comprising ∼9,800 specimens collected from the intensively managed agricultural landscape of the Central Valley of California, we show that on-farm habitat restoration in the form of native plant 'hedgerows', when replicated across a landscape, can boost β-diversity by approximately 14% relative to unrestored field margins, to levels similar to some natural communities. Hedgerows restore β-diversity by promoting the assembly of phenotypically diverse communities. Intensively managed agriculture imposes a strong ecological filter that negatively affects several important dimensions of community trait diversity, distribution, and uniqueness. However, by helping to restore phenotypically diverse pollinator communities, small-scale restorations such as hedgerows provide a valuable tool for conserving biodiversity and promoting ecosystem services.

Local soil, but not commercial AMF inoculum, increases native and non-native grass growth at a mine restoration site.

Abstract: Soil communities are often degraded in mined sites, and facilitating the recovery of soil mutualists such as arbuscular mycorrhizal fungi (AMF) may assist with the restoration of native plants. At a grassland mine restoration site, I compared a commercial AMF inoculum with soil collected from beneath native grasses as a source of inoculum, as well as a control treatment. Field plots were broadcast-inoculated and seeded with native grasses, and biomass of native and non-native species was measured in three consecutive years. In addition, greenhouse-grown seedlings of a native bunchgrass (Stipa pulchra) were inoculated with similar treatments, transplanted into the field, and assessed after 18 months. When broadcast inoculation was used, the local soil inoculum tended to increase non-native grass biomass, and marginally decreased non-native forb biomass in the second year of study, but did not significantly affect native grass biomass. Broadcast commercial inoculum had no detectable effects on biomass of any plant group. Stipa pulchra transplants had greater N content and mycorrhizal colonization, and marginally higher shoot mass and K content, when pre-inoculated with local soil (relative to controls). Pre-inoculation with commercial AMF increased AMF colonization of the S. pulchra transplants, but did not significantly affect biomass or nutrient content. The findings indicate that at this site, the use of local soil as an inoculum had greater effects on native and non-native plants than the commercial product used. In order to substantially increase native grass performance, inoculation of transplanted plugs may be one potential strategy.

Timing is everything: does early and late germination favor invasions by herbaceous alien plants?

Abstract: Plant invasions represent a unique opportunity to study the mechanisms underlying community assembly rules and species distribution patterns. While a superior competitive ability has often been proposed as a major driver of successful plant invasions, its significance depends crucially on the timing of any competitive interaction. We assess whether a mismatch in germination phenology can favor the establishment of alien species, allowing them to exploit vacant niches where competition is low. As well as having important effects on the survival, growth and fitness of a species, asymmetric competition and potential soil legacies resulting from early or late germination can also impact on species recruitment. However, early or late germination comes at a cost, increases the risks of exposure to unfavorable conditions and requires an enhanced abiotic resistance if it is to lead to successful establishment. While there are several anecdotal accounts of early and late germination for invasive species, there are limited comparative data with resident species growing under natural conditions. Available evidence from grassland communities indicates that a short-term germination advantage or priority (few days/weeks) provides invasive species with a strong competitive advantage over native species and is a critical factor in many invasions. While the exploitation of periods of low competition is a plausible mechanism for the successful establishment of many invasive plants, direct evidence for this strategy is still scarce. This is particularly true with regard to the exploitation of late germination niches. Consequently, long-term comparative monitoring of the germination phenology of invasive and native plants in situ is needed to assess its significance in a range of ecosystems and its impact on community dynamics.

Invasive plants affect arbuscular mycorrhizal fungi abundance and species richness as well as the performance of native plants grown in invaded soils

Abstract: We studied the effects of invasions by three plant species: Reynoutria japonica, Rudbeckia laciniata, and Solidago gigantea, on arbuscular mycorrhizal fungi (AMF) communities in habitats located within and outside river valleys. Arbuscular mycorrhizal colonization, AMF abundance and species richness in soils were assessed in adjacent plots with invaders and native vegetation. We also quantified the performance (expressed as shoot mass, chlorophyll fluorescence, and the concentration of elements in shoots) of two common, mycorrhizal native plants, Plantago lanceolata and Trifolium repens, grown in these soils. The invasions of R. japonica, R. laciniata, and S. gigantea influenced AMF communities compared to native vegetation, but the changes depended on the mycorrhizal status of invaders. The effects of non-mycorrhizal R. japonica were the most pronounced. Its invasion reduced AMF abundance and species richness. In the plots of both mycorrhizal plants, R. laciniata and S. gigantea, we observed decreased AMF species richness in comparison to native vegetation. The AMF community alterations could be due to (i) depletion of organic C inputs to AMF in the case of R. japonica, (ii) plant secondary metabolites that directly inhibit or selectively stimulate AMF species, or (iii) changes in soil physicochemical properties induced by invasions. The effect of invasion on AMF abundance and species richness did not generally differ between valley and outside-valley habitats. The invasions affected photosynthetic performance and the concentrations of elements in the shoots of P. lanceolata or T. repens. However, the directions and magnitude of their response depended on both species identity and the mycorrhizal status of invaders.

Invasive non-native plants have a greater effect on neighbouring natives than other non-natives

Abstract: Human activity is creating a global footprint by changing the climate, altering habitats and reshuffling the distribution of species. The movement of species around the globe has led to the naturalization and accumulation of multiple non-native species within ecosystems, which is frequently associated with habitat disturbance and changing environmental conditions. However, interactions among species will also influence community composition, but little is known about the full range of direct and indirect interactions among native and non-native species. Here, we show through a meta-analysis of 1,215 pairwise plant interactions between 274 vascular plant species in 21 major habitat types that interactions between non-native plants are asymmetrical with interactions between non-native and native plants. Non-native plants were always bad neighbours, but the negative effect of non-natives on natives was around two times greater than the effect of non-natives on other non-natives. In contrast, the performance of non-native plants was five times higher in the presence of a neighbouring native plant species than in the presence of a neighbouring non-native plant species. Together, these results demonstrate that invaded plant communities may accumulate additional non-native species even if direct interactions between non-natives species are negative. Put another way, invasions may be more likely to lead to more invasions, requiring more active management of ecosystems by promoting native species restoration to undermine invasive positive feedback and to assist native species recovery in invaded ecosystems. Invading plant species have direct and indirect effects on both native and other non-native species. This meta-analysis finds that while non-native plants negatively affect all their neighbours, they affect natives around twice as harshly as other non-natives.

More of the same? In situ leaf and root decomposition rates do not vary between 80 native and nonnative deciduous forest species.

Abstract: Invaders often have greater rates of production and produce more labile litter than natives. The increased litter quantity and quality of invaders should increase nutrient cycling through faster litter decomposition. However, the limited number of invasive species that have been included in decomposition studies has hindered the ability to generalize their impacts on decomposition rates. Further, previous decomposition studies have neglected roots. We measured litter traits and decomposition rates of leaves for 42 native and 36 nonnative woody species, and those of fine roots for 23 native and 25 nonnative species that occur in temperate deciduous forests throughout the Eastern USA. Among the leaf and root traits that differed between native and invasive species, only leaf nitrogen was significantly associated with decomposition rate. However, native and nonnative species did not differ systematically in leaf and root decomposition rates. We found that among the parameters measured, litter decomposer activity was driven by litter chemical quality rather than tissue density and structure. Our results indicate that litter decomposition rate per se is not a pathway by which forest woody invasive species affect North American temperate forest soil carbon and nutrient processes.

On the island biogeography of aliens: a global analysis of the richness of plant and bird species on oceanic islands

Abstract: Aim (1) To characterize the relationship(s) between species richness and area for alien plant and bird species on islands, and to identify commonalities and differences in those relationships for these different taxa, and between alien and native species; (2) to test whether area per se, native species richness or human factors related to area is the primary determinant of alien species richness; and (3) to explore the effects on alien island biogeography of isolation, productivity and the time since first European landfall. Location Islands around the world. Methods We used structural equation models (SEMs; supported by generalized linear models) to interrogate data on the alien and native species richness of birds and plants on islands. Results Alien plant and bird species richness were both strongly correlated with island area, with similar slopes on logarithmic axes. SEMs for both plants and birds revealed positive direct effects of native species richness and human population size, and positive indirect effects of area, on alien species richness. The models also identified indirect effects of temperature (positive) and isolation (negative) on alien species richness. Native plant and bird species richness were both predicted by direct effects of area (positive), temperature (positive) and isolation (negative). However, native plant richness was the only direct predictor of native bird species richness, and the strongest direct predictor of alien bird species richness, for islands with both plant and bird richness data. Main conclusions Our analyses recover the species–area, species–isolation and productivity relationships in native richness. Alien species richness was most strongly related to native species richness, with additional effects of human population size. Human population size most likely determines the number of alien species that arrive on an island, while the effect of native species richness may be driven by the influence of habitat heterogeneity on the likelihood that those populations persist (establishment success).

Deer feeding selectivity for invasive plants

Abstract: Native generalist herbivores might limit plant invasion by consuming invading plants or enhance plant invasion by selectively avoiding them. The role of herbivores in plant invasion has been investigated in relation to plant native/introduced status, however, a knowledge gap exists about whether food selection occurs according to native/introduced status or to species. We tested preference of the native herbivore white-tailed deer (Odocoileus virginianus) for widespread and frequently occurring invasive introduced and native plants in the northeastern United States. Multiple-choice deer preference trials were conducted for the species and relative preference was determined using biomass consumption and feeding behavior. While more native than introduced plant biomass was consumed overall, deer food selection varied strongly by plant species. Results show consistent deer avoidance of several invasive introduced plants (Alliaria petiolata, Berberis thunbergii, and Microstegium vimineum) and a native plant (Dennstaedtia punctilobula). Other invasive introduced plants (Celastrus orbiculatus, Ligustrum vulgare, and Lonicera morrowii) and a native plant (Acer rubrum) were highly preferred. These results provide evidence that herbivore impacts on plant invaders depend on plant species palatability. Consequently, herbivore selectivity likely plays an important role in the invasion process. To the extent that herbivory impacts population demographics, these results suggest that native generalist herbivores promote enemy release of some plant invaders by avoiding them and contribute to biotic resistance of others by consuming them.

Biotic resistance and disturbance: rodent consumers regulate post-fire plant invasions and increase plant community diversity.

Abstract: Biotic resistance and disturbance are fundamental processes influencing plant invasion outcomes; however, the role of consumers in regulating the establishment and spread of plant invaders and how disturbance modifies biotic resistance by consumers is unclear. We document that fire in combination with experimental exclusion of rodent consumers shifted a native desert shrubland to a low-diversity, invasive annual grassland dominated by Bromus tectorum (cheatgrass). In contrast, burned plots with rodents present suppressed invasion by cheatgrass and developed into a more diverse forb community. Rodents created strong biotic resistance to the establishment of aggressive plant invaders likely through seed and seedling predation, which had cascading effects on plant competition and plant community diversity. Fire mediated its positive effects on plant invaders through native plant removal and by decreasing the abundance and diversity of the rodent community. The experimental disruption of plant and consumer-mediated biotic resistance of plant invaders using fire and rodent exclusion treatments provides strong evidence that native plants and rodents are important regulators of plant invasion dynamics and plant biodiversity in our study system. While rodents conferred strong resistance to invasion in our study system, fluctuations in rodent populations due to disturbance and climatic events may provide windows of opportunity for exotic plant species to escape biotic resistance by rodent consumers and initiate invasions.

Climate and soil factors influencing seedling recruitment of plant species used for dryland restoration

Abstract: . Land degradation affects 10–20 % of drylands globally. Intensive land use and management, large-scale disturbances such as extractive operations, and global climate change, have contributed to degradation of these systems worldwide. Restoring these damaged environments is critical to improving ecosystem services and functions, conserve biodiversity, and contribute to climate resilience, food security, and landscape sustainability. Here, we present a case study on plant species of the mining intensive semi-arid Pilbara region in Western Australia that examines the effects of climate and soil factors on the restoration of drylands. We analysed the effects of a range of rainfall and temperature scenarios and the use of alternative soil materials on seedling recruitment of key native plant species from this area. Experimental studies were conducted in controlled environment facilities where conditions simulated those found in the Pilbara. Soil from topsoil (T) stockpiles and waste materials (W) from an active mine site were mixed at different proportions (100 % T, 100 % W, and two mixes of topsoil and waste at 50 : 50 and 25 : 75 ratios) and used as growth media. Our results showed that seedling recruitment was highly dependent on soil moisture and emergence was generally higher in the topsoil, which had the highest available water content. In general, responses to the climate scenarios differed significantly among the native species which suggest that future climate scenarios of increasing drought might affect not only seedling recruitment but also diversity and structure of native plant communities. The use of waste materials from mining operations as growth media could be an alternative to the limited topsoil. However, in the early stages of plant establishment successful seedling recruitment can be challenging in the absence of water. These limitations could be overcome by using soil amendments but the cost associated to these solutions at large landscape scales needs to be assessed and proven to be economically feasible.

The integration of alien plants in mutualistic plant–hummingbird networks across the Americas: the importance of species traits and insularity

Abstract: Aim: To investigate the role of alien plants in mutualistic plant–hummingbird networks, assessing the importance of species traits, floral abundance and insularity on alien plant integration. Location: Mainland and insular Americas. Methods: We used species-level network indices to assess the role of alien plants in 21 quantitative plant–hummingbird networks where alien plants occur. We then evaluated whether plant traits, including previous adaptations to bird pollination, and insularity predict these network roles. Additionally, for a subset of networks for which floral abundance data were available, we tested whether this relates to network roles. Finally, we tested the association between hummingbird traits and the probability of interaction with alien plants across the networks. Results: Within the 21 networks, we identified 32 alien plant species and 352 native plant species. On average, alien plant species attracted more hummingbird species (i.e. aliens had a higher degree) and had a higher proportion of interactions across their hummingbird visitors than native plants (i.e. aliens had a higher species strength). At the same time, an average alien plant was visited more exclusively by certain hummingbird species (i.e. had a higher level of complementary specialization). Large alien plants and those occurring on islands had more evenly distributed interactions, thereby acting as connectors. Other evaluated plant traits and floral abundance were unimportant predictors of network roles. Short-billed hummingbirds had higher probability of including alien plants in their interactions than long-billed species. Main conclusions: Once incorporated into plant-hummingbird networks, alien plants appear strongly integrated and, thus, may have a large influence on network dynamics. Plant traits and floral abundance were generally poor predictors of how well alien species are integrated. Short-billed hummingbirds, often characterized as functionally generalized pollinators, facilitate the integration of alien plants. Our results show that plant–hummingbird networks are open for invasion.

Pilbara Seed Atlas and Field Guide: Plant Restoration in Australia's Arid Northwest

Abstract: The Pilbara region in Australia’s arid northwest is rich in flora that is suited to extreme temperatures and boom and bust cycles of moisture availability. It is also a region important for its natural resources. In places where mining activities have finished and the land is under management for ecological restoration, there is increasing demand for information about native plant communities and the biology of their seeds. Pilbara Seed Atlas and Field Guide is the first book to combine plant identification with robust, scientific criteria for cost-effective seed-based rehabilitation. It describes 103 regional plant taxa and provides guidelines for effective collection, cleaning, storage and germination of their seeds. It addresses issues such as timing of collection, quality and viability of seed, and dormancy release, which are essential for successful restoration programs. With photographs to portray the subtle differences and unique features of each species’ biology, this book will be of great use to practitioners in the field, including environmental consultants, rehabilitation companies, commercial seed collectors and government authorities, as well as naturalists and people interested in growing the Pilbara’s remarkable plants.

Pollinator-mediated impacts of alien invasive plants on the pollination of native plants: the role of spatial scale and distinct behaviour among pollinator guilds

Abstract: Alien invasive plant species can affect pollination, reproductive success and population dynamics of co-flowering native species via shared pollinators. Consequences may range from reproductive competition to facilitation, but the ecological drivers determining the type and magnitude of such indirect interactions remain poorly understood. Here, we examine the role of the spatial scale of invader presence and spatially contingent behavioural responses of different pollinator groups as potential key drivers, using the invasive Oxalis pes-caprae and the self-incompatible native annual Diplotaxis erucoides as a model system. Three treatments were assigned to native focal plants: (1) invader present at the landscape scale (hectares) but experimentally removed at the floral neighbourhood scale (pa); (2) invader present at both scales (pp); (3) invader absent at both scales (aa). Interestingly, we found pronounced spatially contingent differences in the responses of pollinators: honeybees and bumblebees were strongly attracted into invaded sites at the landscape scale, translating into native plant visitation facilitation through honeybees, while bumblebees almost exclusively visited Oxalis. Non-corbiculate wild bees, in contrast, showed less pronounced responses in foraging behavior, primarily at the floral neighborhood scale. Average heterospecific (Oxalis) pollen deposition onto stigmas of Diplotaxis was low (<1 %), but higher in the pp than in the pa treatment. Hand-pollination of Diplotaxis with Oxalis and conspecific pollen, however, reduced seed set by more than half when compared to hand-pollination with only conspecific pollen. Seed set of Diplotaxis, finally, was increased by 14 % (reproductive facilitation) in the pp treatment, while it was reduced by 27 % (reproductive competition) in the pa treatment compared to uninvaded populations. Our study highlights the crucial role of spatial scale and pollinator guild driving indirect effects of invasive on co-flowering native plant species.

Non-Native Plant Invasion along Elevation and Canopy Closure Gradients in a Middle Rocky Mountain Ecosystem.

Abstract: Mountain environments are currently among the ecosystems least invaded by non-native species; however, mountains are increasingly under threat of non-native plant invasion. The slow pace of exotic plant invasions in mountain ecosystems is likely due to a combination of low anthropogenic disturbances, low propagule supply, and extreme/steep environmental gradients. The importance of any one of these factors is debated and likely ecosystem dependent. We evaluated the importance of various correlates of plant invasions in the Wallowa Mountain Range of northeastern Oregon and explored whether non-native species distributions differed from native species along an elevation gradient. Vascular plant communities were sampled in summer 2012 along three mountain roads. Transects (n = 20) were evenly stratified by elevation (~70 m intervals) along each road. Vascular plant species abundances and environmental parameters were measured. We used indicator species analysis to identify habitat affinities for non-native species. Plots were ordinated in species space, joint plots and non-parametric multiplicative regression were used to relate species and community variation to environmental variables. Non-native species richness decreased continuously with increasing elevation. In contrast, native species richness displayed a unimodal distribution with maximum richness occurring at mid–elevations. Species composition was strongly related to elevation and canopy openness. Overlays of trait and environmental factors onto non-metric multidimensional ordinations identified the montane-subalpine community transition and over-story canopy closure exceeding 60% as potential barriers to non-native species establishment. Unlike native species, non-native species showed little evidence for high-elevation or closed-canopy specialization. These data suggest that non-native plants currently found in the Wallowa Mountains are dependent on open canopies and disturbance for establishment in low and mid elevations. Current management objectives including restoration to more open canopies in dry Rocky Mountain forests, may increase immigration pressure of non-native plants from lower elevations into the montane and subalpine zones.

Rhizobacterial Community Structures Associated with Native Plants Grown in Chilean Extreme Environments

Abstract: Chile is topographically and climatically diverse, with a wide array of diverse undisturbed ecosystems that include native plants that are highly adapted to local conditions. However, our understanding of the diversity, activity, and role of rhizobacteria associated with natural vegetation in undisturbed Chilean extreme ecosystems is very poor. In the present study, the combination of denaturing gradient gel electrophoresis and 454-pyrosequencing approaches was used to describe the rhizobacterial community structures of native plants grown in three representative Chilean extreme environments: Atacama Desert (ATA), Andes Mountains (AND), and Antarctic (ANT). Both molecular approaches revealed the presence of Proteobacteria, Bacteroidetes, and Actinobacteria as the dominant phyla in the rhizospheres of native plants. Lower numbers of operational taxonomic units (OTUs) were observed in rhizosphere soils from ATA compared with AND and ANT. Both approaches also showed differences in rhizobacterial community structures between extreme environments and between plant species. The differences among plant species grown in the same environment were attributed to the higher relative abundance of classes Gammaproteobacteria and Alphaproteobacteria. However, further studies are needed to determine which environmental factors regulate the structures of rhizobacterial communities, and how (or if) specific bacterial groups may contribute to the growth and survival of native plants in each Chilean extreme environments.

Invader disruption of belowground plant mutualisms reduces carbon acquisition and alters allocation patterns in a native forest herb

Abstract: Invasive plants impose novel selection pressures on naive mutualistic interactions between native plants and their partners. As most plants critically rely on root fungal symbionts (RFSs) for soil resources, invaders that disrupt plant-RFS mutualisms can significantly depress native plant fitness. Here, we investigate the consequences of RFS mutualism disruption on native plant fitness in a glasshouse experiment with a forest invader that produces known anti-fungal allelochemicals. Over 5 months, we regularly applied either green leaves of the allelopathic invader Alliaria petiolata, a nonsystemic fungicide to simulate A. petiolata's effects, or green leaves of nonallelopathic Hesperis matronalis (control) to pots containing the native Maianthemum racemosum and its RFSs. We repeatedly measured M. racemosum physiology and harvested plants periodically to assess carbon allocation. Alliaria petiolata and fungicide treatment effects were indistinguishable: we observed inhibition of the RFS soil hyphal network and significant reductions in M. racemosum physiology (photosynthesis, transpiration and conductance) and allocation (carbon storage, root biomass and asexual reproduction) in both treatments relative to the control. Our findings suggest a general mechanistic hypothesis for local extinction of native species in ecosystems challenged by allelopathic invaders: RFS mutualism disruption drives carbon stress, subsequent declines in native plant vigor, and, if chronic, declines in RFS-dependent species abundance.

Deep rooting and global change facilitate spread of invasive grass

Abstract: Abiotic global change factors, such as rising atmospheric CO2, and biotic factors, such as exotic plant invasion, interact to alter the function of terrestrial ecosystems. An invasive lineage of the common reed, Phragmites australis, was introduced to North America over a century ago, but the belowground mechanisms underlying Phragmites invasion and persistence in natural systems remain poorly studied. For instance, Phragmites has a nitrogen (N) demand higher than native plant communities in many of the ecosystems it invades, but the source of the additional N is not clear. We exposed introduced Phragmites and native plant assemblages, containing Spartina patens and Schoenoplectus americanus, to factorial treatments of CO2 (ambient or +300 ppm), N (0 or 25 g m−2 year−1), and hydroperiod (4 levels), and focused our analysis on changes in root productivity as a function of depth and evaluated the effects of introduced Phragmites on soil organic matter mineralization. We report that non-native invasive Phragmites exhibited a deeper rooting profile than native marsh species under all experimental treatments, and also enhanced soil organic matter decomposition. Moreover, exposure to elevated atmospheric CO2 induced a sharp increase in deep root production in the invasive plant. We propose that niche separation accomplished through deeper rooting profiles circumvents nutrient competition where native species have relatively shallow root depth distributions; deep roots provide access to nutrient-rich porewater; and deep roots further increase nutrient availability by enhancing soil organic matter decomposition. We expect that rising CO2 will magnify these effects in deep-rooting invasive plants that compete using a tree-like strategy against native herbaceous plants, promoting establishment and invasion through niche separation.

Wild and native plants and mushrooms sold in the open-air markets of south-eastern Poland

Abstract: The study of plants and fungi sold in open-air markets is an important part of ethnobotanical enquiry. Only few such studies were carried out in Europe. Four of the largest open-air markets of south-eastern Poland were visited regularly, and the plants sold in them were recorded between 2013 and 2015. The aim of the study was to record native and/or wild species sold in the markets. All the plants sold in the markets were photographed regularly. In each market, 25 sellers were interviewed. Voucher specimens were collected and fungi were identified using DNA barcoding. Altogether, 468 species of plants were recorded, 117 of them native to south-eastern Poland – 19 only collected from the wild and 11 both wild and cultivated. Seventeen of the species are under legal protection. Most protected plants were sold from cultivation, although proper authorization procedures had not been performed. Thirty-two species of fungi were sold (including two cultivated species), all of them for culinary purposes. Two species (Lactarius quieticolor, Leccinum schistophilum) are new to the mycobiota of Poland. Ornamental plants constituted a large section of the market, and they dominated the group of native species. Food plants dominated among wild-collected plants and were sold mainly as fruits for jams, juices and alcoholic drinks, or as culinary herbs. Very few medicinal or green vegetable plants were sold. An interesting feature of the markets was the sale of Ledum palustre as an insect repellent. Finding two species of fungi which are new to Poland highlights the importance of DNA barcoding in ethnomycological studies. Most items in the markets are ornamental plants, or edible fruits and mushrooms. Very few medicinal plants and green vegetables are sold, which differentiates the markets from southern European ones. Such a pattern is probably the model for most central European markets.