Moussab/ORKG-training-evaluation-set huggingface dataset:
Research field: Ecology and Evolutionary Biology
Title: Conservation of the Grassy White Box Woodlands: Relative Contributions of Size and Disturbance to Floristic Composition and Diversity of Remnants
Abstract: <jats:p> Before European settlement, grassy white box woodlands were the dominant vegetation in the east of the
wheat-sheep belt of south-eastern Australia. Tree clearing, cultivation and pasture improvement have led
to fragmentation of this once relatively continuous ecosystem, leaving a series of remnants which
themselves have been modified by livestock grazing. Little-modified remnants are extremely rare. We
examined and compared the effects of fragmentation and disturbance on the understorey flora of
woodland remnants, through a survey of remnants of varying size, grazing history and tree clearing. In
accordance with fragmentation theory, species richness generally increased with remnant size, and, for
little-grazed remnants, smaller remnants were more vulnerable to weed invasion. Similarly, tree
clearing and grazing encouraged weed invasion and reduced native species richness. Evidence for
increased total species richness at intermediate grazing levels, as predicted by the intermediate
disturbance hypothesis, was equivocal. Remnant quality was more severely affected by grazing than by
remnant size. All little-grazed remnants had lower exotic species abundance and similar or higher native
species richness than grazed remnants, despite their extremely small sizes (&lt; 6 ha). Further, small, littlegrazed
remnants maintained the general character of the pre-European woodland understorey, while
grazing caused changes to the dominant species. Although generally small, the little-grazed remnants
are the best representatives of the pre-European woodland understorey, and should be central to any
conservation plan for the woodlands. Selected larger remnants are needed to complement these,
however, to increase the total area of woodland conserved, and, because most little-grazed remnants are
cleared, to represent the ecosystem in its original structural form. For the maintenance of native plant
diversity and composition in little-grazed remnants, it is critical that livestock grazing continues to be
excluded. For grazed remnants, maintenance of a site in its current state would allow continuation of
past management, while restoration to a pre-European condition would require management directed
towards weed removal, and could take advantage of the difference noted in the predominant life-cycle
of native (perennial) versus exotic (annual or biennial) species. </jats:p>
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: EFFECTS OF DISTURBANCE ON HERBACEOUS EXOTIC PLANT-SPECIES ON THE FLOODPLAIN OF THE POTOMAC RIVER
Abstract: The objective of this study was to investigate specific effects of disturbance on exotic species in floodplain environments and to provide baseline data on the abundance of exotic herbs in the Potomac River floodplain. Frequency of exotics generally increased with man-made disturbance (forest fragmentation and recreational use of land) and decreased with increasing flooding frequency. Species richness of exotics followed a similar pattern. Some variation was found in individual species' responses to disturbance. The spread of Alliaria officinalis and Glecoma hederacea, the most frequent exotic species, was inhibited by forest fragmentation.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Functional and performance comparisons of invasive Hieracium lepidulum and co-occurring species in New Zealand
Abstract: One of the key environmental factors affecting plant species abundance, including that of invasive exotics, is nutrient resource availability. Plant functional response to nutrient availability, and what this tells us about plant interactions with associated species, may therefore give us clues about underlying processes related to plant abundance and invasion. Patterns of abundance of Hieracium lepidulum, a European herbaceous invader of subalpine New Zealand, appear to be related to soil fertility/nutrient availability, however, abundance may be influenced by other factors including disturbance. In this study we compare H. lepidulum and field co-occurring species for growth performance across artificial nutrient concentration gradients, for relative competitiveness and for response to disturbance, to construct a functional profile of the species. Hieracium lepidulum was found to be significantly different in its functional response to nutrient concentration gradients. Hieracium lepidulum had high relative growth rate, high yield and root plasticity in response to nutrient concentration dilution, relatively low absolute yield, low competitive yield and a positive response to clipping disturbance relative to other species. Based on overall functional response to nutrient concentration gradients, compared with other species found at the same field sites, we hypothesize that H. lepidulum invasion is not related to competitive domination. Relatively low tolerance of nutrient dilution leads us to predict that H. lepidulum is likely to be restricted from invading low fertility sites, including sites within alpine vegetation or where intact high biomass plant communities are found. Positive response to clipping disturbance and relatively high nutrient requirement, despite poor competitive performance, leads us to predict that H. lepidulum may respond to selective grazing disturbance of associated vegetation. These results are discussed in relation to published observations of H. lepidulum in New Zealand and possible tests for the hypotheses raised here.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Mammals of the northern Philippines: tolerance for habitat disturbance and resistance to invasive species in an endemic insular fauna
Abstract: Aim Island faunas, particularly those with high levels of endemism, usually are considered especially susceptible to disruption from habitat disturbance and invasive alien species. We tested this general hypothesis by examining the distribution of small mammals along gradients of anthropogenic habitat disturbance in northern Luzon Island, an area with a very high level of mammalian endemism.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Relationship between productivity, and species and functional group diversity in grazed and non-grazed Pampas grassland
Abstract: Most hypotheses addressing the effect of diversity on ecosystem function indicate the occurrence of higher process rates with increasing diversity, and only diverge in the shape of the function depending on their assumptions about the role of individual species and functional groups. Contrarily to these predictions, we show that grazing of the Flooding Pampas grasslands increased species richness, but drastically reduced above ground net primary production, even when communities with similar initial biomass were compared. Grazing increased species richness through the addition of a number of exotic forbs, without reducing the richness and cover of the native flora. Since these forbs were essentially cool-season species, and also because their introduction has led to the displacement of warm-season grasses from dominant to subordinate positions in the community, grazing not only decreased productivity, but also shifted its seasonality towards the cool season. These results suggest that species diversity and/or richness alone are poor predictors of above-ground primary production. Therefore, models that relate productivity to diversity should take into account the relative abundance and identity of species that are added or deleted by the specific disturbances that modify diversity.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Distribution of an alien aquatic snail in relation to flow variability, human activities and water quality
Abstract: 1. Disturbance and anthropogenic land use changes are usually considered to be key factors facilitating biological invasions. However, specific comparisons of invasion success between sites affected to different degrees by these factors are rare. 2. In this study we related the large-scale distribution of the invading New Zealand mud snail ( Potamopyrgus antipodarum ) in southern Victorian streams, Australia, to anthropogenic land use, flow variability, water quality and distance from the site to the sea along the stream channel. 3. The presence of P. antipodarum was positively related to an index of flow-driven disturbance, the coefficient of variability of mean daily flows for the year prior to the study. 4. Furthermore, we found that the invader was more likely to occur at sites with multiple land uses in the catchment, in the forms of grazing, forestry and anthropogenic developments (e.g. towns and dams), compared with sites with low-impact activities in the catchment. However, this relationship was confounded by a higher likelihood of finding this snail in lowland sites close to the sea. 5. We conclude that P. antipodarum could potentially be found worldwide at sites with similar ecological characteristics. We hypothesise that its success as an invader may be related to an ability to quickly re-colonise denuded areas and that population abundances may respond to increased food resources. Disturbances could facilitate this invader by creating spaces for colonisation (e.g. a possible consequence of floods) or changing resource levels (e.g. increased nutrient levels in streams with intense human land use in their catchments).
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Invasion, competitive dominance, and resource use by exotic and native California grassland species
Abstract: The dynamics of invasive species may depend on their abilities to compete for resources and exploit disturbances relative to the abilities of native species. We test this hypothesis and explore its implications for the restoration of native ecosystems in one of the most dramatic ecological invasions worldwide, the replacement of native perennial grasses by exotic annual grasses and forbs in 9.2 million hectares of California grasslands. The long-term persistence of these exotic annuals has been thought to imply that the exotics are superior competitors. However, seed-addition experiments in a southern California grassland revealed that native perennial species, which had lower requirements for deep soil water, soil nitrate, and light, were strong competitors, and they markedly depressed the abundance and fecundity of exotic annuals after overcoming recruitment limitations. Native species reinvaded exotic grasslands across experimentally imposed nitrogen, water, and disturbance gradients. Thus, exotic annuals are not superior competitors but rather may dominate because of prior disturbance and the low dispersal abilities and extreme current rarity of native perennials. If our results prove to be general, it may be feasible to restore native California grassland flora to at least parts of its former range.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Pre-fire fuel reduction treatments influence plant communities and exotic species 9 years after a large wildfire
Abstract: Questions: How did post-wildfire understorey plant community response, including exotic species response, differ between pre-fire treated areas that were less severely burned, and pre-fire untreated areas that were more severely burned? Were these differences consistent through time? Location: East-central Arizona, southwestern US. Methods: We used a multi-year data set from the 2002 Rodeo–Chediski Fire to detect post-fire trends in plant community response in burned ponderosa pine forests. Within the burn perimeter, we examined the effects of pre-fire fuels treatments on post-fire vegetation by comparing paired treated and untreated sites on the Apache-Sitgreaves National Forest. We sampled these paired sites in 2004, 2005 and 2011. Results: There were significant differences in pre-fire treated and untreated plant communities by species composition and abundance in 2004 and 2005, but these communities were beginning to converge in 2011. Total understorey plant cover was significantly higher in untreated areas for all 3 yr. Plant cover generally increased between 2004 and 2005 and markedly decreased in 2011, with the exception of shrub cover, which steadily increased through time. The sharp decrease in forb and graminoid cover in 2011 is likely related to drought conditions since the fire. Annual/biennial forb and graminoid cover decreased relative to perennial cover through time, consistent with the initial floristics hypothesis. Exotic plant response was highly variable and not limited to the immediate post-fire, annual/biennial community. Despite low overall exotic forb and graminoid cover for all years (<2.5%), several exotic species increased in frequency, and the relative proportion of exotic to native cover increased through time. Conclusions: Pre-treatment fuel reduction treatments helped maintain foundation overstorey species and associated native plant communities following this large wildfire. The overall low cover of exotic species on these sites supports other findings that the disturbance associated with high-severity fire does not always result in exotic species invasions. The increase in relative cover and frequency though time indicates that some species are proliferating, and continued monitoring is recommended. Patterns of exotic species invasions after severe burning are not easily predicted, and are likely more dependent on site-specific factors such as propagules, weather patterns and management.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Quantifying the impact of an extreme climate event on species diversity in fragmented temperate forests: the effect of the October 1987 storm on British broadleaved woodlands
Abstract: We report the impact of an extreme weather event, the October 1987 severe storm, on fragmented woodlands in southern Britain. We analysed ecological changes between 1971 and 2002 in 143 200‐m2 plots in 10 woodland sites exposed to the storm with an ecologically equivalent sample of 150 plots in 16 non‐exposed sites. Comparing both years, understorey plant species‐richness, species composition, soil pH and woody basal area of the tree and shrub canopy were measured. We tested the hypothesis that the storm had deflected sites from the wider national trajectory of an increase in woody basal area and reduced understorey species‐richness associated with ageing canopies and declining woodland management. We also expected storm disturbance to amplify the background trend of increasing soil pH, a UK‐wide response to reduced atmospheric sulphur deposition. Path analysis was used to quantify indirect effects of storm exposure on understorey species richness via changes in woody basal area and soil pH. By 2002, storm exposure was estimated to have increased mean species richness per 200 m2 by 32%. Woody basal area changes were highly variable and did not significantly differ with storm exposure. Increasing soil pH was associated with a 7% increase in richness. There was no evidence that soil pH increased more as a function of storm exposure. Changes in species richness and basal area were negatively correlated: a 3.4% decrease in richness occurred for every 0.1‐m2 increase in woody basal area per plot. Despite all sites substantially exceeding the empirical critical load for nitrogen deposition, there was no evidence that in the 15 years since the storm, disturbance had triggered a eutrophication effect associated with dominance of gaps by nitrophilous species. Synthesis. Although the impacts of the 1987 storm were spatially variable in terms of impacts on woody basal area, the storm had a positive effect on understorey species richness. There was no evidence that disturbance had increased dominance of gaps by invasive species. This could change if recovery from acidification results in a soil pH regime associated with greater macronutrient availability.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: How grazing and soil quality affect native and exotic plant diversity in rocky mountain grasslands
Abstract: We used multiscale plots to sample vascular plant diversity and soil characteristics in and adjacent to 26 long-term grazing exclosure sites in Colorado, Wyoming, Montana, and South Dakota, USA. The exclosures were 7–60 yr old (31.2 ± 2.5 yr, mean ± 1 se). Plots were also randomly placed in the broader landscape in open rangeland in the same vegetation type at each site to assess spatial variation in grazed landscapes. Consistent sampling in the nine National Parks, Wildlife Refuges, and other management units yielded data from 78 1000-m2 plots and 780 1-m2 subplots. We hypothesized that native species richness would be lower in the exclosures than in grazed sites, due to competitive exclusion in the absence of grazing. We also hypothesized that grazed sites would have higher native and exotic species richness compared to ungrazed areas, due to disturbance (i.e., the intermediate-disturbance hypothesis) and the conventional wisdom that grazing may accelerate weed invasion. Both hypotheses were soundly rej...
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Lack of native species recovery following severe exotic disturbance in southern Californian shrublands
Abstract: Summary 1. Urban and agricultural activities are not part of natural disturbance regimes and may bear little resemblance to them. Such disturbances are common in densely populated semi-arid shrub communities of the south-western US, yet successional studies in these regions have been limited primarily to natural successional change and the impact of human-induced changes on natural disturbance regimes. Although these communities are resilient to recurrent and large-scale disturbance by fire, they are not necessarily well-adapted to recover from exotic disturbances. 2. This study investigated the effects of severe exotic disturbance (construction, heavy-vehicle activity, landfill operations, soil excavation and tillage) on shrub communities in southern California. These disturbances led to the conversion of indigenous shrublands to exotic annual communities with low native species richness. 3. Nearly 60% of the cover on disturbed sites consisted of exotic annual species, while undisturbed sites were primarily covered by native shrub species (68%). Annual species dominant on disturbed sites included Erodium botrys, Hypochaeris glabra, Bromus spp., Vulpia myuros and Avena spp. 4. The cover of native species remained low on disturbed sites even 71 years after initial exotic disturbance ceased. Native shrub seedlings were also very infrequent on disturbed sites, despite the presence of nearby seed sources. Only two native shrubs, Eriogonum fasciculatum and Baccharis sarothroides, colonized some disturbed sites in large numbers. 5. Although some disturbed sites had lower total soil nitrogen and percentage organic matter and higher pH than undisturbed sites, soil variables measured in this study were not sufficient to explain variations in species abundances on these sites. 6. Non-native annual communities observed in this study did not recover to a predisturbed state within typical successional time (< 25 years), supporting the hypothesis that altered stable states can occur if a community is pushed beyond its threshold of resilience.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Roads Alter the Colonization Dynamics of a Keystone Herbivore in Neotropical Savannas
Abstract: Roads can facilitate the establishment and spread of both native and exotic species. Nevertheless, the precise mechanisms facilitating this expansion are rarely known. We tested the hypothesis that dirt roads are favorable landing and nest initiation sites for founding‐queens of the leaf‐cutter ant Atta laevigata. For 2 yr, we compared the number of attempts to found new nests (colonization attempts) in dirt roads and the adjacent vegetation in a reserve of cerrado (tree‐dominated savanna) in southeastern Brazil. The number of colonization attempts in roads was 5 to 10 times greater than in the adjacent vegetation. Experimental transplants indicate that founding‐queens are more likely to establish a nest on bare soil than on soil covered with leaf‐litter, but the amount of litter covering the ground did not fully explain the preference of queens for dirt roads. Queens that landed on roads were at higher risk of predation by beetles and ants than those that landed in the adjacent vegetation. Nevertheless, greater predation in roads was not sufficient to offset the greater number of colonization attempts in this habitat. As a consequence, significantly more new colonies were established in roads than in the adjacent vegetation. Our results suggest that disturbance caused by the opening of roads could result in an increased Atta abundance in protected areas of the Brazilian Cerrado.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Case studies of the expansion of Acacia dealbata in the valley of the river Mino (Galicia, Spain)
Abstract: Aim of study: Acacia dealbata is a naturalized tree of invasive behaviour that has expanded from small plots associated with vineyards into forest ecosystems. Our main objective is to find evidence to support the notion that disturbances, particularly forest fires, are important driving factors in the current expansion of A. dealbata. Area of study: We mapped it current distribution using three study areas and assesses the temporal changes registered in forest cover in these areas of the valley of the river Mino. Material and Methods: The analyses were based on visual interpretation of aerial photographs taken in 1985 and 2003 of three 1x1 km study areas and field works. Main result: A 62.4%, 48.6% and 22.2% of the surface area was covered by A. dealbata in 2003 in pure or mixed stands. Furthermore, areas composed exclusively of A. dealbata make up 33.8%, 15.2% and 5.7% of the stands. The transition matrix analyses between the two dates support our hypothesis that the areas currently covered by A. dealbata make up a greater proportion of the forest area previously classified as unwooded or open forest than those without A. dealbata cover. Both of these surface types are the result of an important impact of fire in the region. Within each area, A. dealbata is mainly located on steeper terrain, which is more affected by fires. Research highlights: A. dealbata is becoming the dominant tree species over large areas and the invasion of this species gives rise to monospecific stands, which may have important implications for future fire regimes. Keywords: Fire regime; Mimosa; plant invasion; silver wattle.
Extracted statement — hypothesis: Disturbance