Non-native Plants (non-native + plant)

Distribution by Scientific Domains

Terms modified by Non-native Plants

  • non-native plant species

  • Selected Abstracts

    A non-native invasive grass increases soil carbon flux in a Hawaiian tropical dry forest

    Abstract Non-native plants are invading terrestrial ecosystems across the globe, yet little is known about how invasions impact carbon (C) cycling or how these impacts will be influenced by climate change. We quantified the effect of a non-native C4 grass invasion on soil C pools and fluxes in a Hawaiian tropical dry forest over 2 years in which annual precipitation was average (Year 1) and ,60% higher than average (Year 2). Work was conducted in a series of forested plots where the grass understory was completely removed (removal plots) or left intact (grass plots) for 3 years before experiment initiation. We hypothesized that grass invasion would: (i) not change total soil C pools, (ii) increase the flux of C into and out of soils, and (iii) increase the sensitivity of soil C flux to variability in precipitation. In grass plots, grasses accounted for 25,34% of litter layer C and ,70% of fine root C. However, no differences were observed between treatments in the size of any soil C pools. Moreover, grass-derived C constituted a negligible fraction of the large mineral soil C pool (< 3%) despite being present in the system for ,50 years. Tree litterfall was ,45% lower in grass plots, but grass-derived litterfall more than compensated for this reduction in both years. Annual cumulative soil-surface CO2 efflux (Rsoil) was ,40% higher in grass plots in both years, and increased in both treatments by ,36% in the wetter Year 2. Despite minimal grass-derived mineral soil C, > 75% of Rsoil in grass plots was of C4 (i.e. grass) origin. These results demonstrate that grass invasion in forest ecosystems can increase the flux of C into and out of soils without changing total C pools, at least over the short term and as long as the native tree canopy remains intact, and that invasion-mediated changes in belowground C cycling are sensitive to precipitation. [source]

    Recreational Portage Trails as Corridors Facilitating Non-Native Plant Invasions of the Boundary Waters Canoe Area Wilderness (U.S.A.)

    corredores; invasiones; perturbación humana; recreación; senderos Abstract:,Wilderness areas are protected and valued in part for recreation; recreational use, however, can negatively impact these areas. In particular, recreational use can facilitate transport of non-native propagules and create open sites for establishment of non-native species. We examined the role of recreational portage trails in the introduction and establishment of non-native plants into the Boundary Waters Canoe Area Wilderness of northern Minnesota (U.S.A.). On 20 portages, we sampled non-native plant richness and cover at four distances (0, 10, 25, and 50 m) from trails. Non-native richness and cover were not related to distance from wilderness entry point. Non-native richness and cover were, however, negatively related to distance from trails. All six non-native species we observed were either directly on or within 1 m of trails. These results suggest that recreational trails act as corridors facilitating invasions of non-native plants into wilderness areas. It remains unclear, however, whether these effects are caused by dispersal of propagules, creation of bare ground, or changes in the native plant community. Resumen:,En parte, las áreas silvestres son protegidas y valoradas para recreación; sin embargo, el uso recreativo puede impactar a estas áreas negativamente. En particular, el uso recreativo puede facilitar el transporte de propágulos no nativos y crear áreas abiertas para el establecimiento de especies no nativas. Examinamos el papel de senderos recreativos en la introducción y establecimiento de plantas no nativas en el Boundary Waters Canoe Area Wilderness en el norte de Minnesota (E.U.A.). En 20 senderos, muestreamos la riqueza y cobertura de plantas no nativas a cuatro distancias (0, 10, 25 y 50 m) de los senderos. La riqueza y cobertura de no nativas no se relacionaron con la distancia al punto de entrada al área silvestre. Sin embargo, la riqueza y cobertura de no nativas se relacionaron negativamente con la distancia a los senderos. Las seis especies no nativas fueron observadas directamente sobre o a 1 m de los senderos. Estos resultados sugieren que los senderos recreativos fungen como corredores que facilitan la invasión de plantas no nativas a las áreas silvestres. Sin embargo, aún no es claro si estos efectos son causados por la dispersión de propágulos, la creación de suelo desnudo o por cambios en la comunidad de plantas nativas. [source]

    Phylogenetic relatedness and plant invader success across two spatial scales

    Marc W. Cadotte
    ABSTRACT Aim, Successful invaders often possess similar ecological traits that contribute to success in new regions, and thus under niche conservatism, invader success should be phylogenetically clustered. We asked if the degree to which non-native plant species are phylogenetically related is a predictor of invasion success at two spatial scales. Location, Australia , the whole continent and Royal National Park (south-eastern Australia). Methods, We used non-native plant species occupancy in Royal National Park, as well as estimated continental occupancy of these species from herbarium records. We then estimated phylogenetic relationships using molecular data from three gene sequences available on GenBank (matK, rbcL and ITS1). We tested for phylogenetic signals in occupancy using Blomberg's K. Results, Whereas most non-native plants were relatively scarce, there was a strong phylogenetic signal for continental occupancy, driven by the clustering of successful species in Asteraceae, Caryophyllaceae, Poaceae and Solanaceae. However, we failed to detect a phylogenetic signal at the park scale. Main Conclusions, Our results reveal that at a large spatial scale, invader success is phylogenetically clustered where ecological traits promoting success appear to be shared among close relatives, indicating that phylogenetic relationships can be useful predictors of invasion success at large spatial scales. At a smaller, landscape scale, there was no evidence of phylogenetic clustering of invasion success, and thus, relatedness plays a much reduced role in determining the relative success of invaders. [source]

    Fish abundance and community composition in native and non-native plants following hydrilla colonisation at Lake Izabal, Guatemala

    Abstract, Fish community composition was assessed among six macrophyte habitats, including hydrilla, Hydrilla verticillata (L.F.) Royle, common native species (bulrush, Scirpus spp., muskgrass, Chara spp., eelgrass, Vallisneria americana Michx. and Illinois pondweed, Potamogeton illinoensis Morong) and no-plants, to assess potential impacts of recent hydrilla colonisation on the littoral fish community at Lake Izabal, Guatemala. Fish biomass was significantly different among habitats, with hydrilla supporting the highest fish biomass. Fish density did not differ significantly among habitats. Total fish species richness was similar (12-15 species) among habitats, but community composition changed with macrophyte presence. Biomass of mojarra, Cichlasoma maculicauda Regan, which supported the most important subsistence fishery at the lake, was significantly different among habitats and had the greatest biomass in the hydrilla habitat. Although hydrilla may adversely affect native plants, lake access and other uses, it provided useful fish habitat and likely was not detrimental to the Lake Izabal fish community composition. [source]

    California annual grass invaders: the drivers or passengers of change?

    JOURNAL OF ECOLOGY, Issue 5 2010
    Janneke HilleRisLambers
    Summary 1.,The dominance of invasive species is often assumed to reflect their competitive superiority over displaced native species. However, invasive species may be abundant because of their greater tolerance to anthropogenic impacts accompanying their introduction. Thus, invasive species can either be the drivers or passengers of change. 2.,We distinguish between these two possibilities in California grasslands currently dominated by Mediterranean annuals (exotics) and subjected to livestock grazing since European settlement. We focused on native annual grasses and forbs, an understudied species-rich component of the California flora, and Mediterranean annual grasses, currently dominant and among the first non-native plants introduced to the area. 3.,We established a field experiment with fenced and unfenced blocks in a cattle pasture. We measured concentrations of limiting resources (nitrogen, phosphorus, light and soil moisture) in monoculture plots as an index of competitive ability (i.e. R*). We then quantified grazing impacts on biomass and seed production in grazed vs. ungrazed monoculture plots. Finally, we measured biomass and seed production of each species competing in mixture plots, in the presence and absence of grazers. 4.,We found that native and exotic species did not differ in R* indices of competitive ability, i.e. concentrations of limiting resources in ungrazed native monoculture plots did not differ from concentrations in ungrazed exotic monoculture plots. By contrast, exotic annuals suffered less from grazing than native annuals, perhaps reflecting their longer evolutionary history with cattle grazing. Consistent with these results, native and exotic annuals were equally abundant in ungrazed mixtures, but exotic species overwhelmingly dominated grazed mixtures. 5.,Species able to draw down nitrogen and light to lower levels in monocultures (i.e. those with lower R* values) dominated biomass and seeds in mixed plots without grazers. However, R* did not predict the relative abundance of species in grazed plots. Moreover, the relative abundance of species in mixtures did not correlate with grazing impacts on their monocultures, implying that grazing alters inter-specific competitive dynamics. 6.,Synthesis. We demonstrate that the displacement of native annuals by Mediterranean annual grasses in California may largely have been driven by cattle grazing. [source]

    Plant,soil feedback induces shifts in biomass allocation in the invasive plant Chromolaena odorata

    JOURNAL OF ECOLOGY, Issue 6 2009
    Mariska Te Beest
    Summary 1. ,Soil communities and their interactions with plants may play a major role in determining the success of invasive species. However, rigorous investigations of this idea using cross-continental comparisons, including native and invasive plant populations, are still scarce. 2. ,We investigated if interactions with the soil community affect the growth and biomass allocation of the (sub)tropical invasive shrub Chromolaena odorata. We performed a cross-continental comparison with both native and non-native-range soil and native and non-native-range plant populations in two glasshouse experiments. 3. ,Results are interpreted in the light of three prominent hypotheses that explain the dominance of invasive plants in the non-native range: the enemy release hypothesis, the evolution of increased competitive ability hypothesis and the accumulation of local pathogens hypothesis. 4. ,Our results show that C. odorata performed significantly better when grown in soil pre-cultured by a plant species other than C. odorata. Soil communities from the native and non-native ranges did not differ in their effect on C. odorata performance. However, soil origin had a significant effect on plant allocation responses. 5. ,Non-native C. odorata plants increased relative allocation to stem biomass and height growth when confronted with soil communities from the non-native range. This is a plastic response that may allow species to be more successful when competing for light. This response differed between native and non-native-range populations, suggesting that selection may have taken place during the process of invasion. Whether this plastic response to soil organisms will indeed select for increased competitive ability needs further study. 6. ,The native grass Panicum maximum did not perform worse when grown in soil pre-cultured by C. odorata. Therefore, our results did not support the accumulation of local pathogens hypothesis. 7. ,Synthesis. Non-native C. odorata did not show release from soil-borne enemies compared to its native range. However, non-native plants responded to soil biota from the non-native range by enhanced allocation in stem biomass and height growth. This response can affect the competitive balance between native and invasive species. The evolutionary potential of this soil biota-induced change in plant biomass allocation needs further study. [source]

    Patterns of invasion within a grassland community

    JOURNAL OF ECOLOGY, Issue 5 2002
    A. Kolb
    Summary 1Relatively few studies have looked for patterns of invasion by non-native species within communities. We tested the hypotheses that: (i) some types of microhabitats within a community are more invasible than others; (ii) microhabitat types that differ in invasion also differ in resource availability; and (iii) invasibility is mediated by effects of these resources on competition between native and non-native species. 2To test the first two hypotheses, we measured plant cover and soils in a coastal grassland in northern California. Consistent with these hypotheses, cover of non-native plants was consistently high where nitrogen-fixing shrubs had recently grown, in the bottoms and sides of gullies and on deep soils, and these microhabitats tended to have relatively high nitrogen or water availability. 3Cover and number of native species tended to be lower where cover of non-native species was higher, indicating that non-native species as a group negatively affected native species. However, the number of non-native species also tended to be lower where the total cover of non-natives was higher. This suggests that a few non-native species excluded natives and other non-natives alike. 4To test the third hypothesis, we grew a common non-native, the annual grass Lolium multiflorum, and a common native, the perennial grass Hordeum brachyantherum, at different levels of water and nitrogen. The relative competitive ability of the native was higher at lower nitrogen availability but not at lower water availability. When 10-week-old native plants were grown with non-native seedlings and nitrogen was relatively low, the native out-competed the non-native. However, the non-native out-competed the native at all resource levels when species were both grown as seedlings. Competition between native and non-native grasses in this system may thus help prevent invasion by non-natives in microhabitats where nitrogen availability is low, but invasion may be relatively irreversible. [source]

    Effects of Native and Non-Native Grassland Plant Communities on Breeding Passerine Birds: Implications for Restoration of Northwest Bunchgrass Prairie

    Patricia L. Kennedy
    Abstract One common problem encountered when restoring grasslands is the prominence of non-native plant species. It is unclear what effect non-native plants have on habitat quality of grassland passerines, which are among the most imperiled groups of birds. In 2004 and 2005, we compared patterns of avian reproduction and the mechanisms that might influence those patterns across a gradient of 13 grasslands in the Zumwalt Prairie in northeastern Oregon that vary in the degree of non-native plant cover (0.9,53.4%). We monitored the fate of 201 nests of all the breeding species in these pastures and found no association of percent non-native cover with nest densities, clutch size, productivity, nest survival, and nestling size. Regardless of the degree of non-native cover, birds primarily fed on Coleoptera, Orthoptera, and Araneae. But as percent non-native cover in the pastures increased, Orthoptera made up a greater proportion of diet and Coleoptera made up a smaller proportion. These diet switches were not the result of changes in terrestrial invertebrate abundance but may be related to decreases in percent bare ground associated with increasing cover of non-native vegetation. Measures of nest crypticity were not associated with cover of non-native vegetation, suggesting that predation risk may not increase with increased cover of non-native vegetation. Thus, the study results show that increased non-native cover is not associated with reduced food supplies or increased predation risk for nesting birds, supporting the growing body of evidence that grasslands with a mix of native and non-native vegetation can provide suitable habitat for native grassland breeding birds. [source]

    Effects of invasive alien kahili ginger (Hedychium gardnerianum) on native plant species regeneration in a Hawaiian rainforest

    V. Minden
    Abstract Questions: Does the invasive alien Hedychium gardnerianum (1) replace native understory species, (2) suppress natural regeneration of native plant species, (3) increase the invasiveness of other non-native plants and (4) are native forests are able to recover after removal of H. gardnerianum. Location: A mature rainforest in Hawai'i Volcanoes National Park on the island of Hawai'i (about 1200 m a.s.l.; precipitation approximately 2770 mm yr,1). Study sites included natural plots without effects of alien plants, ginger plots with a H. gardnerianum -dominated herb layer and cleared plots treated with herbicide to remove alien plants. Methods: Counting mature trees, saplings and seedlings of native and alien plant species. Using non-parametric H -tests to compare impact of H. gardnerianum on the structure of different sites. Results: Results confirmed the hypothesis that H. gardnerianum has negative effects on natural forest dynamics. Lower numbers of native tree seedlings and saplings were found on ginger-dominated plots. Furthermore, H. gardnerianum did not show negative effects on the invasive alien tree species Psidium cattleianum. Conclusions: This study reveals that where dominance of H. gardnerianum persists, regeneration of the forest by native species will be inhibited. Furthermore, these areas might experience invasion by P. cattleianum, resulting in displacement of native canopy species in the future, leading to a change in forest structure and loss of other species dependent on natural rainforest, such as endemic birds. However, if H. gardnerianum is removed the native Hawaiian forest is likely to regenerate and regain its natural structure. [source]

    Relationships among non-native plants, diversity of plants and butterflies, and adequacy of spatial sampling

    Non-native invasive species are altering ecosystems in undesirable ways, often leading to biotic homogenization and rapid reduction of evolutionary potential. However, lack of money and time hampers attempts to monitor the outcome of restoration efforts. Hence, it is useful to determine whether relatively limited sampling can provide valid inferences about biological responses to pattern-based and process-based variables that are affected by restoration actions. In the Mojave Desert, invasion of salt-cedar (Tamarix ramosissima) has altered vegetational communities and some measures of faunal diversity. We tested whether six vegetation-based predictor variables affected species richness of butterflies in the Muddy River drainage (Nevada, USA). We also explored whether similar conclusions about relationships between vegetation and butterflies could have been obtained by using data from a subset of the 85 locations included in the study. We found that the effect of non-native plants on species richness of butterflies was negligible. Availability of nectar had the greatest independent explanatory power on species richness of butterflies, followed by species richness of plants. In comparison with the full data set, subsamples including 10, 25 and 50% of sites yielded similar conclusions. Our results suggest that relatively limited data sets may allow us to draw reliable inferences for adaptive management in the context of ecological restoration and rehabilitation. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85, 157,166. [source]

    Patterns of Seed Dispersal and Dispersal Failure in a Hawaiian Dry Forest Having Only Introduced Birds

    BIOTROPICA, Issue 4 2010
    Charles G. Chimera
    ABSTRACT Dry forests are among the most endangered natural communities in the Hawaiian Islands. Most have been reduced to isolated trees and small forest fragments in which native tree species reproduce poorly. The replacement of native birds by introduced generalists may be contributing to dry forest decline through modification of seed dispersal patterns. To document seed dispersal by introduced birds, we conducted foraging observations on fleshy-fruited trees and measured seed rain under trees and in adjacent open areas for 1 year in a dry forest dominated by native trees. Although trees covered only 15.2 percent of the study area, 96.9 percent of the bird-dispersed seeds were deposited beneath them. The Japanese white-eye (Zosterops japonicus) was the principal dispersal agent. Among bird-dispersed seeds, those of the invasive tree Bocconia frutescens accounted for 75 percent of all seeds collected beneath trees (14.8 seeds/m2/yr) and the invasive shrub Lantana camara accounted for 17 percent. Although nearly 60 percent of the reserve's native woody species possess fleshy fruits, introduced birds rarely disperse their seeds. Native trees accounted for <8 percent of all bird-dispersed seeds and are consequently experiencing dispersal failure by falling directly under parent trees. Smaller-seeded non-native plants, in contrast, may be benefiting from dispersal by introduced birds. Current dispersal patterns suggest that these readily disseminated non-native plants may eventually replace the remaining native flora. [source]