Moussab/ORKG-training-evaluation-set huggingface dataset:
Research field: Ecology and Evolutionary Biology
Title: Local interactions, dispersal, and native and exotic plant diversity along a California stream
Abstract: Although the species pool, dispersal, and local interactions all influence species diversity, their relative importance is debated. I examined their importance in controlling the number of native and exotic plant species occupying tussocks formed by the sedge Carex nudata along a California stream. Of particular interest were the factors underlying a downstream increase in plant diversity and biological invasions. I conducted seed addition experiments and manipulated local diversity and cover to evaluate the degree to which tussocks saturate with species, and to examine the roles of local competitive processes, abiotic factors, and seed supply in controlling the system-wide patterns. Seeds of three native and three exotic plants sown onto experimentally assembled tussock communities less successfully established on tussocks with a greater richness of resident plants. Nonetheless, even the most diverse tussocks were somewhat colonized, suggesting that tussocks are not completely saturated with species. Similarly, in an experiment where I sowed seeds onto natural tussocks along the river, colonization increased two- to three-fold when I removed the resident species. Even on intact tussocks, however, seed addition increased diversity, indicating that the tussock assemblages are seed limited. Colonization success on cleared and uncleared tussocks increased downstream from km 0 to km 3 of the study site, but showed no trends from km 3 to km 8. This suggests that while abiotic and biotic features of the tussocks may control the increase in diversity and invasions from km 0 to km 3, similar increases from km 3 to km 8 are more likely explained by potential downstream increases in seed supply. The effective water dispersal of seed mimics and prevailingly downstream winds indicated that dispersal most likely occurs in a downstream direction. These results suggest that resident species diversity, competitive interactions, and seed supply similarly influence the colonization of native and exotic species.
Extracted statement — Investigated species: Plants
Research field: Ecology and Evolutionary Biology
Title: Phalaris arundinacea seedling establishment: effects of canopy complexity in fen, mesocosm, and restoration experiments
Abstract: Phalaris arundinacea L. (reed canary grass) is a major invader of wetlands in temperate North America; it creates monotypic stands and displaces native vegetation. In this study, the effect of plant canopies on the establishment of P. arundinacea from seed in a fen, fen-like mesocosms, and a fen restoration site was assessed. In Wingra Fen, canopies that were more resistant to P. arundinacea establishment had more species (eight or nine versus four to six species) and higher cover of Aster firmus. In mesocosms planted with Glyceria striata plus 1, 6, or 15 native species, all canopies closed rapidly and prevented P. arundinacea establishment from seed, regardless of the density of the matrix species or the number of added species. Only after gaps were created in the canopy was P. arundinacea able to establish seedlings; then, the 15-species treatment reduced establishment to 48% of that for single-species canopies. A similar experiment in the restoration site produced less cover of native plants, and P. a...
Extracted statement — Investigated species: Plants
Research field: Ecology and Evolutionary Biology
Title: Evenness-invasibility relationships differ between two extinction scenarios in tallgrass prairie
Abstract: Experiments that have manipulated species richness with random draws of species from a larger species pool have usually found that invasibility declines as richness increases. These results have usually been attributed to niche complementarity, and interpreted to mean that communities will become less resistant to invaders as species go locally extinct. However, it is not clear how relevant these studies are to real-world situations where species extinctions are non-random, and where species diversity declines due to increased rarity (i.e. reduced evenness) without having local extinctions. We experimentally varied species richness from 1 to 4, and evenness from 0.44 to 0.97 with two different extinction scenarios in two-year old plantings using seedling transplants in western Iowa. In both scenarios, evenness was varied by changing the level of dominance of the tall grass Andropogon gerardii. In one scenario, which simulated a loss of short species from Andropogon communities, we directly tested for complementarity in light capture due to having species in mixtures with dissimilar heights. We contrasted this scenario with a second set of mixtures that contained all tall species. In both cases, we controlled for factors such as rooting depth and planting density. Mean invader biomass was higher in monocultures (5.4 g m 2 week 1 ) than in 4-species mixtures (3.2 g m 2 week 1 ). Reduced evenness did not affect invader biomass in mixtures with dissimilar heights. However, the amount of invader biomass decreased by 60% as evenness increased across mixtures with all tall species. This difference was most pronounced early in the growing season when high evenness plots had greater light capture than low evenness plots. These results suggest that the effect of reduced species diversity on invasibility are 1) not related to complementarity through height dissimilarity, and 2) variable depending on the phenological traits of the species that are becoming rare or going locally extinct.
Extracted statement — Investigated species: Plants
Research field: Ecology and Evolutionary Biology
Title: The distribution and habitat associations of non-native plant species in urban riparian habitats
Abstract: Questions: 1. What are the distribution and habitat associations of non-native (neophyte) species in riparian zones? 2. Are there significant differences, in terms of plant species diversity, composition, habitat condition and species attributes, between plant communities where non-natives are present or abundant and those where non-natives are absent or infrequent? 3. Are the observed differences generic to non-natives or do individual non-native species differ in their vegetation associations? Location: West Midlands Conurbation (WMC), UK. Methods: 56 sites were located randomly on four rivers across the WMC. Ten 2 m × 2 m quadrats were placed within 15 m of the river to sample vegetation within the floodplain at each site. All vascular plants were recorded along with site information such as surrounding land use and habitat types. Results: Non-native species were found in many vegetation types and on all rivers in the WMC. There were higher numbers of non-natives on more degraded, human-modified rivers. More non-native species were found in woodland, scrub and tall herb habitats than in grasslands. We distinguish two types of communities with non-natives. In communities colonized following disturbance, in comparison to quadrats containing no non-native species, those with non-natives had higher species diversity and more forbs, annuals and shortlived monocarpic perennials. Native species in quadrats containing non-natives were characteristic of conditions of higher fertility and pH, had a larger specific leaf area and were less stress tolerant or competitive. In later successional communities dominated by particular non-natives, native diversity declined with increasing cover of non-natives. Associated native species were characteristic of low light conditions. Conclusions: Communities containing non-natives can be associated with particular types of native species. Extrinsic factors (disturbance, eutrophication) affected both native and non-native species. In disturbed riparian habitats the key determinant of diversity is dominance by competitive invasive species regardless of their native or non-native origin.
Extracted statement — Investigated species: Plants
Research field: Ecology and Evolutionary Biology
Title: Patterns of invasion of an urban remnant of a species-rich grassland in southeastern Australia by non-native plant species
Abstract: . The invasion by non-native plant species of an urban remnant of a species-rich Themeda triandra grassland in southeastern Australia was quantified and related to abiotic influences. Richness and cover of non-native species were highest at the edges of the remnant and declined to relatively uniform levels within the remnant. Native species richness and cover were lowest at the edge adjoining a roadside but then showed little relation to distance from edge. Roadside edge quadrats were floristically distinct from most other quadrats when ordinated by Detrended Correspondence Analysis. Soil phosphorus was significantly higher at the roadside edge but did not vary within the remnant itself. All other abiotic factors measured (NH4, NO3, S, pH and % organic carbon) showed little variation across the remnant. Non-native species richness and cover were strongly correlated with soil phosphorus levels. Native species were negatively correlated with soil phosphorus levels. Canonical Correspondence Analysis identified the perennial non-native grasses of high biomass as species most dependent on high soil nutrient levels. Such species may be resource-limited in undisturbed soils. Three classes of non-native plants have invaded this species-rich grassland: (1) generalist species (> 50 % frequency), mostly therophytes with non-specialized habitat or germination requirements; (2) resource-limited species comprising perennial species of high biomass that are dependent on nutrient increases and/or soil disturbances before they can invade the community and; (3) species of intermediate frequency (1–30 %), of low to high biomass potential, that appear to have non-specialized habitat requirements but are currently limited by seed dispersal, seedling establishment or the current site management. Native species richness and cover are most negatively affected by increases in non-native cover. Declines are largely evident once the non-native cover exceeds 40 %. Widespread, generalist non-native species are numerous in intact sites and will have to be considered a permanent part of the flora of remnant grasslands. Management must aim to minimize increases in cover of any non-native species or the disturbances that favour the establishment of competitive non-native grasses if the native grassland flora is to be conserved in small, fragmented remnants.
Extracted statement — Investigated species: Plants
Research field: Ecology and Evolutionary Biology
Title: Native plant diversity increases herbivory to non-natives
Abstract: There is often an inverse relationship between the diversity of a plant community and the invasibility of that community by non-native plants. Native herbivores that colonize novel plants may contribute to diversity–invasibility relationships by limiting the relative success of non-native plants. Here, we show that, in large collections of non-native oak trees at sites across the USA, non-native oaks introduced to regions with greater oak species richness accumulated greater leaf damage than in regions with low oak richness. Underlying this trend was the ability of herbivores to exploit non-native plants that were close relatives to their native host. In diverse oak communities, non-native trees were on average more closely related to native trees and received greater leaf damage than those in depauperate oak communities. Because insect herbivores colonize non-native plants that are similar to their native hosts, in communities with greater native plant diversity, non-natives experience greater herbivory.
Extracted statement — Investigated species: Plants
Research field: Ecology and Evolutionary Biology
Title: Habitat stress, species pool size and biotic resistance influence exotic plant richness in the Flooding Pampa grasslands
Abstract: 1 Theory and empirical evidence suggest that community invasibility is influenced by propagule pressure, physical stress and biotic resistance from resident species. We studied patterns of exotic and native species richness across the Flooding Pampas of Argentina, and tested for exotic richness correlates with major environmental gradients, species pool size, and native richness, among and within different grassland habitat types. 2 Native and exotic richness were positively correlated across grassland types, increasing from lowland meadows and halophyte steppes, through humid to mesophyte prairies in more elevated topographic positions. Species pool size was positively correlated with local richness of native and exotic plants, being larger for mesophyte and humid prairies. Localities in the more stressful meadow and halophyte steppe habitats contained smaller fractions of their landscape species pools. 3 Native and exotic species numbers decreased along a gradient of increasing soil salinity and decreasing soil depth, and displayed a unimodal relationship with soil organic carbon. When covarying habitat factors were held constant, exotic and native richness residuals were still positively correlated across sites. Within grassland habitat types, exotic and native species richness were positively associated in meadows and halophyte steppes but showed no consistent relationship in the least stressful, prairie habitat types. 4 Functional group composition differed widely between native and exotic species pools. Patterns suggesting biotic resistance to invasion emerged only within humid prairies, where exotic richness decreased with increasing richness of native warm‐season grasses. This negative relationship was observed for other descriptors of invasion such as richness and cover of annual cool‐season forbs, the commonest group of exotics. 5 Our results support the view that ecological factors correlated with differences in invasion success change with the range of environmental heterogeneity encompassed by the analysis. Within narrow habitat ranges, invasion resistance may be associated with either physical stress or resident native diversity. Biotic resistance through native richness, however, appeared to be effective only at intermediate locations along a stress/fertility gradient. 6 We show that certain functional groups, not just total native richness, may be critical to community resistance to invasion. Identifying such native species groups is important for directing management and conservation efforts.
Extracted statement — Investigated species: Plants
Research field: Ecology and Evolutionary Biology
Title: Exotic plants on Lord Howe Island: distribution in space and time, 1853-1981
Abstract: One hundred and seventy-three exotic angiosperms form 48.2% of the angiosperm flora of Lord Howe Island (310 35'S, 1590 05'E) in the south Pacific Ocean. The families Poaceae (23%) and Asteraceae (13%) dominate the exotic flora. Some 30% are native to the Old World, 26% from the New World and 14% from Eurasia. Exotics primarily occur on heavily disturbed areas but c. 10% are widely distributed in undisturbed vegetation. Analysis of historical records, eleven species lists over the 128 years 1853-1981, shows that invasion has been a continuous process at an exponential rate. Exotics have been naturalized at the overall rate of 1.3 species y-1. Most exotics were deliberately introduced as pasture species or accidentally as contaminants although ornamental plants are increasing. Exotics show some evidence of invading progressively less disturbed habitats but the response of each species is individualistic. As introduction of exotics is a social rather than an ecological problem, the present pattern will continue.
Extracted statement — Investigated species: Plants
Research field: Ecology and Evolutionary Biology
Title: Native and naturalized plant diversity are positively correlated in scrub communities of California and Chile
Abstract: Abstract. An emerging body of literature suggests that the richness of native and naturalized plant species are often positively correlated. It is unclear, however, whether this relationship is robust across spatial scales, and how a disturbance regime may affect it. Here, I examine the relationships of both richness and abundance between native and naturalized species of plants in two mediterranean scrub communities: coastal sage scrub (CSS) in California and xeric‐sloped matorral (XSM) in Chile. In each vegetation type I surveyed multiple sites, where I identified vascular plant species and estimated their relative cover. Herbaceous species richness was higher in XSM, while cover of woody species was higher in CSS, where woody species have a strong impact upon herbaceous species. As there were few naturalized species with a woody growth form, the analyses performed here relate primarily to herbaceous species. Relationships between the herbaceous cover of native and naturalized species were not significant in CSS, but were nearly significant in XSM. The herbaceous species richness of native and naturalized plants were not significantly correlated on sites that had burned less than one year prior to sampling in CSS, and too few sites were available to examine this relationship in XSM. In post 1‐year burn sites, however, herbaceous richness of native and naturalized species were positively correlated in both CSS and XSM. This relationship occurred at all spatial scales, from 400 m2 to 1 m2 plots. The consistency of this relationship in this study, together with its reported occurrence in the literature, suggests that this relationship may be general. Finally, the residuals from the correlations between native and naturalized species richness and cover, when plotted against site age (i.e. time since the last fire), show that richness and cover of naturalized species are strongly favoured on recently burned sites in XSM; this suggests that herbaceous species native to Chile are relatively poorly adapted to fire.
Extracted statement — Investigated species: Plants
Research field: Ecology and Evolutionary Biology
Title: A null model of exotic plant diversity tested with exotic and native species-area relationships
Abstract: At large spatial scales, exotic and native plant diversity exhibit a strong positive relationship. This may occur because exotic and native species respond similarly to processes that influence diversity over large geographical areas. To test this hypothesis, we compared exotic and native species-area relationships within six North American ecoregions. We predicted and found that within ecoregions the ratio of exotic to native species richness remains constant with increasing area. Furthermore, we predicted that areas with more native species than predicted by the species-area relationship would have proportionally more exotics as well. We did find that these exotic and native deviations were highly correlated, but areas that were good (or bad) for native plants were even better (or worse) for exotics. Similar processes appear to influence exotic and native plant diversity but the degree of this influence may differ with site quality.
Extracted statement — Investigated species: Plants
Research field: Ecology and Evolutionary Biology
Title: Plant species invasions along the latitudinal gradient in the United States
Abstract: It has been long established that the richness of vascular plant species and many animal taxa decreases with increasing latitude, a pattern that very generally follows declines in actual and potential evapotranspiration, solar radiation, temperature, and thus, total productivity. Using county-level data on vascular plants from the United States (3000 counties in the conterminous 48 states), we used the Akaike Information Criterion (AIC) to evaluate competing models predicting native and nonnative plant species density (number of species per square kilometer in a county) from various combinations of biotic variables (e.g., native bird species density, vegetation carbon, normalized difference vegetation in- dex), environmental/topographic variables (elevation, variation in elevation, the number of land cover classes in the county, radiation, mean precipitation, actual evapotranspiration, and potential evapotranspiration), and human variables (human population density, crop- land, and percentage of disturbed lands in a county). We found no evidence of a latitudinal gradient for the density of native plant species and a significant, slightly positive latitudinal gradient for the density of nonnative plant species. We found stronger evidence of a sig- nificant, positive productivity gradient (vegetation carbon) for the density of native plant species and nonnative plant species. We found much stronger significant relationships when biotic, environmental/topographic, and human variables were used to predict native plant species density and nonnative plant species density. Biotic variables generally had far greater influence in multivariate models than human or environmental/topographic variables. Later, we found that the best, single, positive predictor of the density of nonnative plant species in a county was the density of native plant species in a county. While further study is needed, it may be that, while humans facilitate the initial establishment invasions of non- native plant species, the spread and subsequent distributions of nonnative species are con- trolled largely by biotic and environmental factors.
Extracted statement — Investigated species: Plants
Research field: Ecology and Evolutionary Biology
Title: Biotic resistance to invader establishment of a southern Appalachian plant community is determined by environmental conditions
Abstract: Summary 1 Tests of the relationship between resident plant species richness and habitat invasibility have yielded variable results. I investigated the roles of experimental manipulation of understorey species richness and overstorey characteristics in resistance to invader establishment in a floodplain forest in south-western Virginia, USA. 2 I manipulated resident species richness in experimental plots along a flooding gradient, keeping plot densities at their original levels, and quantified the overstorey characteristics of each plot. 3 After manipulating the communities, I transplanted 10 randomly chosen invaders from widespread native and non-native forest species into the experimental plots. Success of an invasion was measured by survival and growth of the invader. 4 Native and non-native invader establishment trends were influenced by different aspects of the biotic community and these relationships depended on the site of invasion. The most significant influence on non-native invader survival in this system of streamside and upper terrace plots was the overstorey composition. Non-native species survival in the flooded plots after 2 years was significantly positively related to proximity to larger trees. However, light levels did not fully explain the overstorey effect and were unrelated to native survivorship. The effects of understorey richness on survivorship depended on the origin of the invaders and the sites they were transplanted into. Additionally, native species growth was significantly affected by understorey plot richness. 5 The direction and strength of interactions with both the overstorey (for non-native invaders) and understorey richness (for natives and non-natives) changed with the site of invasion and associated environmental conditions. Rather than supporting the hypothesis of biotic resistance to non-native invasion, my results suggest that native invaders experienced increased competition with the native understorey plants in the more benign upland habitat and facilitation in the stressful riparian zone.
Extracted statement — Investigated species: Plants