Moussab/ORKG-training-evaluation-set huggingface dataset:
Research field: Ecology and Evolutionary Biology
Title: Roads as conduits for exotic plant invasions in a semiarid landscape
Abstract: Abstract: Roads are believed to be a major contributing factor to the ongoing spread of exotic plants. We examined the effect of road improvement and environmental variables on exotic and native plant diversity in roadside verges and adjacent semiarid grassland, shrubland, and woodland communities of southern Utah ( U.S.A. ). We measured the cover of exotic and native species in roadside verges and both the richness and cover of exotic and native species in adjacent interior communities ( 50 m beyond the edge of the road cut ) along 42 roads stratified by level of road improvement ( paved, improved surface, graded, and four‐wheel‐drive track ). In roadside verges along paved roads, the cover of Bromus tectorum was three times as great ( 27% ) as in verges along four‐wheel‐drive tracks ( 9% ). The cover of five common exotic forb species tended to be lower in verges along four‐wheel‐drive tracks than in verges along more improved roads. The richness and cover of exotic species were both more than 50% greater, and the richness of native species was 30% lower, at interior sites adjacent to paved roads than at those adjacent to four‐wheel‐drive tracks. In addition, environmental variables relating to dominant vegetation, disturbance, and topography were significantly correlated with exotic and native species richness and cover. Improved roads can act as conduits for the invasion of adjacent ecosystems by converting natural habitats to those highly vulnerable to invasion. However, variation in dominant vegetation, soil moisture, nutrient levels, soil depth, disturbance, and topography may render interior communities differentially susceptible to invasions originating from roadside verges. Plant communities that are both physically invasible ( e.g., characterized by deep or fertile soils ) and disturbed appear most vulnerable. Decision‐makers considering whether to build, improve, and maintain roads should take into account the potential spread of exotic plants.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Testing life history correlates of invasiveness using congeneric plant species
Abstract: We used three congeneric annual thistles, which vary in their ability to invade California (USA) annual grasslands, to test whether invasiveness is related to differences in life history traits. We hypothesized that populations of these summer-flowering Centaurea species must pass through a demographic gauntlet of survival and reproduction in order to persist and that the most invasive species (C. solstitialis) might possess unique life history characteristics. Using the idea of a demographic gauntlet as a conceptual framework, we compared each congener in terms of (1) seed germination and seedling establishment, (2) survival of rosettes subjected to competition from annual grasses, (3) subsequent growth and flowering in adult plants, and (4) variation in breeding system. Grazing and soil disturbance is thought to affect Centaurea establishment, growth, and reproduction, so we also explored differences among congeners in their response to clipping and to different sizes of soil disturbance. We found minimal differences among congeners in either seed germination responses or seedling establishment and survival. In contrast, differential growth responses of congeners to different sizes of canopy gaps led to large differences in adult size and fecundity. Canopy-gap size and clipping affected the fecundity of each species, but the most invasive species (C. solstitialis) was unique in its strong positive response to combinations of clipping and canopy gaps. In addition, the phenology of C. solstitialis allows this species to extend its growing season into the summer—a time when competition from winter annual vegetation for soil water is minimal. Surprisingly, C. solstitialis was highly self-incompatible while the less invasive species were highly self-compatible. Our results suggest that the invasiveness of C. solstitialis arises, in part, from its combined ability to persist in competition with annual grasses and its plastic growth and reproductive responses to open, disturbed habitat patches. Corresponding Editor: D. P. C. Peters.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Invasibility and abiotic gradients: the positive correlation between native and exotic plant diversity
Abstract: We sampled the understory community in an old-growth, temperate forest to test alternative hypotheses explaining the establishment of exotic plants. We quantified the individual and net importance of distance from areas of human disturbance, native plant diversity, and environmental gradients in determining exotic plant establishment. Distance from disturbed areas, both within and around the reserve, was not correlated to exotic species richness. Numbers of native and exotic species were positively correlated at large (50 m 2 ) and small (10 m 2 ) plot sizes, a trend that persisted when relationships to environ- mental gradients were controlled statistically. Both native and exotic species richness in- creased with soil pH and decreased along a gradient of increasing nitrate availability. Exotic species were restricted to the upper portion of the pH gradient and had individualistic responses to the availability of soil resources. These results are inconsistent with both the diversity-resistance and resource-enrichment hypotheses for invasibility. Environmental conditions favoring native species richness also favor exotic species richness, and com- petitive interactions with the native flora do not appear to limit the entry of additional species into the understory community at this site. It appears that exotic species with niche requirements poorly represented in the regional flora of native species may establish with relatively little resistance or consequence for native species richness.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Land use intensification differentially benefits alien over native predators in agricultural landscape mosaics
Abstract: Both anthropogenic habitat disturbance and the breadth of habitat use by alien species have been found to facilitate invasion into novel environments, and these factors have been hypothesized to be important within coccinellid communities specifically. In this study, we address two questions: (1) Do alien species benefit more than native species from human‐disturbed habitats? (2) Are alien species more generalized in their habitat use than natives within the invaded range or can their abundance patterns be explained by specialization on the most common habitats?
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Grassland invisibility and diversity: responses to nutrients, seed input, and disturbance
Abstract: The diversity and composition of a community are determined by a com- bination of local and regional processes. We conducted a field experiment to examine the impact of resource manipulations and seed addition on the invasibility and diversity of a low-productivity grassland. We manipulated resource levels both by a disturbance treatment that reduced adult plant cover in the spring of the first year and by addition of fertilizer every year. Seeds of 46 native species, both resident and nonresident to the community, were added in spring of the first year to determine the effects of recruitment limitation from local (seed limitation) and regional (dispersal limitation) sources on local species richness. Our results show that the unmanipulated community was not readily invasible. Seed addition increased the species richness of unmanipulated plots, but this was primarily due to increased occurrence of resident species. Nonresident species were only able to invade following a cover-reduction disturbance. Cover reduction resulted in an increase in nitrogen availability in the first year, but had no measurable effect on light availability in any year. In contrast, fertilization created a persistent increase in nitrogen availability that increased plant cover or biomass and reduced light penetration to ground level. Initially, fertilization had an overall positive effect on species richness, but by the third year, the effect was either negative or neutral. Unlike cover reduction, fertilization had no observable effect on seedling recruitment or occurrence (number of plots) of invading resident or nonresident species. The results of our experiment demonstrate that, although resource fluctuations can increase the invasibility of this grass- land, the community response depends on the nature of the resource change.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Influence of fire and soil nutrients on native and non-native annuals at remnant vegetation edges in the Western Australian wheatbelt
Abstract: . The effect of fire on annual plants was examined in two vegetation types at remnant vegetation edges in the Western Australian wheatbelt. Density and cover of non-native species were consistently greatest at the reserve edges, decreasing rapidly with increasing distance from reserve edge. Numbers of native species showed little effect of distance from reserve edge. Fire had no apparent effect on abundance of non-natives in Allocasuarina shrubland but abundance of native plants increased. Density of both non-native and native plants in Acacia acuminata-Eucalyptus loxophleba woodland decreased after fire. Fewer non-native species were found in the shrubland than in the woodland in both unburnt and burnt areas, this difference being smallest between burnt areas. Levels of soil phosphorus and nitrate were higher in burnt areas of both communities and ammonium also increased in the shrubland. Levels of soil phosphorus and nitrate were higher at the reserve edge in the unburnt shrubland, but not in the woodland. There was a strong correlation between soil phosphorus levels and abundance of non-native species in the unburnt shrubland, but not after fire or in the woodland. Removal of non-native plants in the burnt shrubland had a strong positive effect on total abundance of native plants, apparently due to increases in growth of smaller, suppressed native plants in response to decreased competition. Two native species showed increased seed production in plots where non-native plants had been removed. There was a general indication that, in the short term, fire does not necessarily increase invasion of these communities by non-native species and could, therefore be a useful management tool in remnant vegetation, providing other disturbances are minimised.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Disturbance Facilitates Invasion: The Effects Are Stronger Abroad than at Home
Abstract: Disturbance is one of the most important factors promoting exotic invasion. However, if disturbance per se is sufficient to explain exotic success, then “invasion” abroad should not differ from “colonization” at home. Comparisons of the effects of disturbance on organisms in their native and introduced ranges are crucial to elucidate whether this is the case; however, such comparisons have not been conducted. We investigated the effects of disturbance on the success of Eurasian native Centaurea solstitialis in two invaded regions, California and Argentina, and one native region, Turkey, by conducting field experiments consisting of simulating different disturbances and adding locally collected C. solstitialis seeds. We also tested differences among C. solstitialis genotypes in these three regions and the effects of local soil microbes on C. solstitialis performance in greenhouse experiments. Disturbance increased C. solstitialis abundance and performance far more in nonnative ranges than in the native range, but C. solstitialis biomass and fecundity were similar among populations from all regions grown under common conditions. Eurasian soil microbes suppressed growth of C. solstitialis plants, while Californian and Argentinean soil biota did not. We suggest that escape from soil pathogens may contribute to the disproportionately powerful effect of disturbance in introduced regions.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Effect of disturbance and nutrient addition on native and introduced annuals in plant communities in the Western Australian wheatbelt
Abstract: To investigate factors affecting the ability of introduced species to invade natural communities in the Western Australian wheatbelt, five communities were examined within a nature reserve near Kellerberrin. Transect studies indicated that introduced annuals were more abundant in woodland than in shrub communities, despite an input of introduced seed into all communities. The response of native and introduced annuals to soil disturbance and fertilizer addition was examined. Small areas were disturbed and/or provided with fertilizer prior to addition of seed of introduced annuals. In most communities, the introduced species used (Avena fatua and Ursinia anthemoides) established well only where the soil had been disturbed, but their growth was increased greatly when fertilizer was also added. Establishment and growth of other introduced species also increased where nutrient addition and soil disturbance were combined. Growth of several native annuals increased greatly with fertilizer addition, but showed little response to disturbance. Fertilizer addition also significantly increased the number of native species present in most communities. This indicates that growth of both native and introduced species is limited by nutrient availability in these communities, but also that introduced species respond more to a combination of nutrient addition and soil disturbance.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Removal of nonnative vines and post-hurricane recruitment in tropical hardwood forests of Florida
Abstract: Abstract In hardwood subtropical forests of southern Florida, nonnative vines have been hypothesized to be detrimental, as many species form dense “vine blankets” that shroud the forest. To investigate the effects of nonnative vines in post-hurricane regeneration, we set up four large (two pairs of 30 × 60 m) study areas in each of three study sites. One of each pair was unmanaged and the other was managed by removal of nonnative plants, predominantly vines. Within these areas, we sampled vegetation in 5 × 5 m plots for stems 2 cm DBH (diameter at breast height) or greater and in 2 × 0.5 m plots for stems of all sizes. For five years, at annual censuses, we tagged and measured stems of vines, trees, shrubs and herbs in these plots. For each 5 × 5 m plot, we estimated percent coverage by individual vine species, using native and nonnative vines as classes. We investigated the hypotheses that: (1) plot coverage, occurrence and recruitment of nonnative vines were greater than that of native vines in unmanaged plots; (2) the management program was effective at reducing cover by nonnative vines; and (3) reduction of cover by nonnative vines improved recruitment of seedlings and saplings of native trees, shrubs, and herbs. In unmanaged plots, nonnative vines recruited more seedlings and had a significantly higher plot-cover index, but not a higher frequency of occurrence. Management significantly reduced cover by nonnative vines and had a significant overall positive effect on recruitment of seedlings and saplings of native trees, shrubs and herbs. Management also affected the seedling community (which included vines, trees, shrubs, and herbs) in some unanticipated ways, favoring early successional species for a longer period of time. The vine species with the greatest potential to “strangle” gaps were those that rapidly formed dense cover, had shade tolerant seedling recruitment, and were animal-dispersed. This suite of traits was more common in the nonnative vines than in the native vines. Our results suggest that some vines may alter the spatiotemporal pattern of recruitment sites in a forest ecosystem following a natural disturbance by creating many very shady spots very quickly.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Effects of an intense prescribed fire on understory vegetation in a mixed conifer forest
Abstract: Abstract Huisinga, K. D., D. C. Laughlin, P. Z. Fulé, J. D. Springer, and C. M. McGlone (Ecological Restoration Institute and School of Forestry, Northern Arizona University, Box 15017, Flagstaff, AZ 86011). Effects of an intense prescribed fire on understory vegetation in a mixed conifer forest. J. Torrey Bot. Soc. 132: 590–601. 2005.—Intense prescribed fire has been suggested as a possible method for forest restoration in mixed conifer forests. In 1993, a prescribed fire in a dense, never-harvested forest on the North Rim of Grand Canyon National Park escaped prescription and burned with greater intensity and severity than expected. We sampled this burned area and an adjacent unburned area to assess fire effects on understory species composition, diversity, and plant cover. The unburned area was sampled in 1998 and the burned area in 1999; 25% of the plots were resampled in 2001 to ensure that differences between sites were consistent and persistent, and not due to inter-annual climatic differences. Species composition differed significantly between unburned and burned sites; eight species were identified as indicators of the unburned site and thirteen as indicators of the burned site. Plant cover was nearly twice as great in the burned site than in the unburned site in the first years of measurement and was 4.6 times greater in the burned site in 2001. Average and total species richness was greater in the burned site, explained mostly by higher numbers of native annual and biennial forbs. Overstory canopy cover and duff depth were significantly lower in the burned site, and there were significant inverse relationships between these variables and plant species richness and plant cover. Greater than 95% of the species in the post-fire community were native and exotic plant cover never exceeded 1%, in contrast with other northern Arizona forests that were dominated by exotic species following high-severity fires. This difference is attributed to the minimal anthropogenic disturbance history (no logging, minimal grazing) of forests in the national park, and suggests that park managers may have more options than non-park managers to use intense fire as a tool for forest conservation and restoration.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Epifaunal disturbance by periodic low levels of dissolved oxygen: native vs. invasive species response
Abstract: Hypoxia is increasing in marine and estuarine systems worldwide, primarily due to anthropogenic causes. Periodic hypoxia represents a pulse disturbance, with the potential to restruc- ture estuarine biotic communities. We chose the shallow, epifaunal community in the lower Chesa- peake Bay, Virginia, USA, to test the hypothesis that low dissolved oxygen (DO) (<4 mg l -1 ) affects community dynamics by reducing the cover of spatial dominants, creating space both for less domi- nant native species and for invasive species. Settling panels were deployed at shallow depths in spring 2000 and 2001 at Gloucester Point, Virginia, and were manipulated every 2 wk from late June to mid-August. Manipulation involved exposing epifaunal communities to varying levels of DO for up to 24 h followed by redeployment in the York River. Exposure to low DO affected both species com- position (presence or absence) and the abundance of the organisms present. Community dominance shifted away from barnacles as level of hypoxia increased. Barnacles were important spatial domi- nants which reduced species diversity when locally abundant. The cover of Hydroides dianthus, a native serpulid polychaete, doubled when exposed to periodic hypoxia. Increased H. dianthus cover may indicate whether a local region has experienced periodic, local DO depletion and thus provide an indicator of poor water-quality conditions. In 2001, the combined cover of the invasive and crypto- genic species in this community, Botryllus schlosseri (tunicate), Molgula manhattensis (tunicate), Ficopomatus enigmaticus (polychaete) and Diadumene lineata (anemone), was highest on the plates exposed to moderately low DO (2 mg l -1 < DO < 4 mg l -1 ). All 4 of these species are now found world- wide and exhibit life histories well adapted for establishment in foreign habitats. Low DO events may enhance success of invasive species, which further stress marine and estuarine ecosystems.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Human activity facilitates altitudinal expansion of exotic plants along a road in montane grassland, South Africa
Abstract: ABSTRACT Question: Do anthropogenic activities facilitate the distribution of exotic plants along steep altitudinal gradients? Location: Sani Pass road, Grassland biome, South Africa. Methods: On both sides of this road, presence and abundance of exotic plants was recorded in four 25-m long road-verge plots and in parallel 25 m × 2 m adjacent land plots, nested at five altitudinal levels: 1500, 1800, 2100, 2400 and 2700 m a.s.l. Exotic community structure was analyzed using Canonical Correspondence Analysis while a two-level nested Generalized Linear Model was fitted for richness and cover of exotics. We tested the upper altitudinal limits for all exotics along this road for spatial clustering around four potential propagule sources using a t-test. Results: Community structure, richness and abundance of exotics were negatively correlated with altitude. Greatest invasion by exotics was recorded for adjacent land at the 1500 m level. Of the 45 exotics, 16 were found at higher altitudes than expected and observations were spatially clustered around potential propagule sources. Conclusions: Spatial clustering of upper altitudinal limits around human inhabited areas suggests that exotics originate from these areas, while exceeding expected altitudinal limits suggests that distribution ranges of exotics are presently underestimated. Exotics are generally characterised by a high propagule pressure and/or persistent seedbanks, thus future tarring of the Sani Pass may result in an increase of exotic species richness and abundance. This would initially result from construction-related soil disturbance and subsequently from increased traffic, water run-off, and altered fire frequency. We suggest examples of management actions to prevent this. Nomenclature: Germishuizen & Meyer (2003).
Extracted statement — hypothesis: Disturbance