Moussab/ORKG-training-evaluation-set huggingface dataset:
Research field: Ecology and Evolutionary Biology
Title: The influence of anthropogenic disturbance and environmental suitability on the distribution of the nonindigenous amphipod, Echinogammarus ischnus, at Laurentian Great Lakes coastal margins
Abstract: ABSTRACT Invasion ecology offers a unique opportunity to examine drivers of ecological processes that regulate communities. Biotic resistance to nonindigenous species establishment is thought to be greater in communities that have not been disturbed by human activities. Alternatively, invasion may occur wherever environmental conditions are appropriate for the colonist, regardless of the composition of the existing community and the level of disturbance. We tested these hypotheses by investigating distribution of the nonindigenous amphipod, Echinogammarus ischnus Stebbing, 1899, in co-occurrence with a widespread amphipod, Gammarus fasciatus Say, 1818, at 97 sites across the Laurentian Great Lakes coastal margins influenced by varying types and levels of anthropogenic stress. E. Ischnus was distributed independently of disturbance gradients related to six anthropogenic disturbance variables that summarized overall nutrient input, nitrogen, and phosphorus load carried from the adjacent coastal watershed, agricultural land area, human population density, overall pollution loading, and the site-specific dominant stressor, consistent with the expectations of regulation by general environmental characteristics. Our results support the view that the biotic facilitation by dreissenid mussels and distribution of suitable habitats better explain E. ischnus' distribution at Laurentian Great Lakes coastal margins than anthropogenic disturbance.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Alien plant dynamics following fire in Mediterranean-climate California shrublands
Abstract: Over 75 species of alien plants were recorded during the first five years after fire in southern California shrublands, most of which were European annuals. Both cover and richness of aliens varied between years and plant association. Alien cover was lowest in the first postfire year in all plant associations and remained low during succession in chaparral but increased in sage scrub. Alien cover and richness were significantly correlated with year (time since disturbance) and with precipitation in both coastal and interior sage scrub associations. Hypothesized factors determining alien dominance were tested with structural equation modeling. Models that included nitrogen deposition and distance from the coast were not significant, but with those variables removed we obtained a significant model that gave an R 2 5 0.60 for the response variable of fifth year alien dominance. Factors directly affecting alien dominance were (1) woody canopy closure and (2) alien seed banks. Significant indirect effects were (3) fire intensity, (4) fire history, (5) prefire stand structure, (6) aridity, and (7) community type. According to this model the most critical factor in- fluencing aliens is the rapid return of the shrub and subshrub canopy. Thus, in these communities a single functional type (woody plants) appears to the most critical element controlling alien invasion and persistence. Fire history is an important indirect factor be- cause it affects both prefire stand structure and postfire alien seed banks. Despite being fire-prone ecosystems, these shrublands are not adapted to fire per se, but rather to a particular fire regime. Alterations in the fire regime produce a very different selective environment, and high fire frequency changes the selective regime to favor aliens. This study does not support the widely held belief that prescription burning is a viable man- agement practice for controlling alien species on semiarid landscapes.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Fire and grazing impacts on plant diversity and alien plant invasions in the southern Sierra Nevada
Abstract: Patterns of native and alien plant diversity in response to disturbance were examined along an elevational gradient in blue oak savanna, chaparral, and coniferous forests. Total species richness, alien species richness, and alien cover declined with elevation, at scales from 1 to 1000 m2. We found no support for the hypothesis that community diversity inhibits alien invasion. At the 1-m2 point scale, where we would expect competitive interactions between the largely herbaceous flora to be most intense, alien species richness as well as alien cover increased with increasing native species richness in all communities. This suggests that aliens are limited not by the number of native competitors, but by resources that affect establishment of both natives and aliens. Blue oak savannas were heavily dominated by alien species and consistently had more alien than native species at the 1-m2 scale. All of these aliens are annuals, and it is widely thought that they have displaced native bunchgrasses. If true, this...
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Species introductions, diversity and disturbances in marine macrophyte assemblages of the northwestern Mediterranean Sea
Abstract: In the process of species introduction, the traits that enable a species to establish and spread in a new habitat, and the habitat characteristics that determine the susceptibility to intro- duced species play a major role. Among the habitat characteristics that render a habitat resistant or susceptible to introductions, species diversity and disturbance are believed to be the most important. It is generally assumed that high species richness renders a habitat resistant to introductions, while disturbances enhance their susceptibility. In the present study, these 2 hypotheses were tested on NW Mediterranean shallow subtidal macrophyte assemblages. Data collection was carried out in early summer 2002 on sub-horizontal rocky substrate at 9 sites along the French Mediterranean coast, 4 undisturbed and 5 highly disturbed. Disturbances include cargo, naval and passenger har- bours, and industrial and urban pollution. Relationships between species richness (point diversity), disturbances and the number of introduced macrophytes were analysed. The following conclusions were drawn: (1) there is no relationship between species introductions, diversity and disturbance for the macrophyte assemblages; (2) multifactorial analyses only revealed the biogeographical relation- ships between the native flora of the sites.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Biogenic disturbance determines invasion success in a subtidal soft-sediment system
Abstract: Theoretically, disturbance and diversity can influence the success of invasive colonists if (1) resource limitation is a prime determinant of invasion success and (2) disturbance and diversity affect the availability of required resources. However, resource limitation is not of overriding importance in all systems, as exemplified by marine soft sediments, one of Earth's most widespread habitat types. Here, we tested the disturbance-invasion hypothesis in a marine soft-sediment system by altering rates of biogenic disturbance and tracking the natural colonization of plots by invasive species. Levels of sediment disturbance were controlled by manipulating densities of burrowing spatangoid urchins, the dominant biogenic sediment mixers in the system. Colonization success by two invasive species (a gobiid fish and a semelid bivalve) was greatest in plots with sediment disturbance rates < 500 cm(3) x m(-2) x d(-1), at the low end of the experimental disturbance gradient (0 to > 9000 cm(3) x m(-2) x d(-1)). Invasive colonization declined with increasing levels of sediment disturbance, counter to the disturbance-invasion hypothesis. Increased sediment disturbance by the urchins also reduced the richness and diversity of native macrofauna (particularly small, sedentary, surface feeders), though there was no evidence of increased availability of resources with increased disturbance that would have facilitated invasive colonization: sediment food resources (chlorophyll a and organic matter content) did not increase, and space and access to overlying water were not limited (low invertebrate abundance). Thus, our study revealed the importance of biogenic disturbance in promoting invasion resistance in a marine soft-sediment community, providing further evidence of the valuable role of bioturbation in soft-sediment systems (bioturbation also affects carbon processing, nutrient recycling, oxygen dynamics, benthic community structure, and so on.). Bioturbation rates are influenced by the presence and abundance of large burrowing species (like spatangoid urchins). Therefore, mass mortalities of large bioturbators could inflate invasion risk and alter other aspects of ecosystem performance in marine soft-sediment habitats.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Old World Climbing Fern (Lygodium microphyllum) Invasion in Hurricane Caused Treefalls
Abstract: ABSTRACT: We examined effects of a natural disturbance (hurricanes) on potential invasion of tree islands by an exotic plant (Old World climbing fern, Lygodium microphyllum) in the Arthur R. Marshall Loxahatchee National Wildlife Refuge, Florida. Three major hurricanes in 2004 and 2005 caused varying degrees of impacts to trees on tree islands within the Refuge. Physical impacts of hurricanes were hypothesized to promote invasion and growth of L. microphyllum. We compared presence and density of L. microphyllum in plots of disturbed soil created by hurricane-caused treefalls to randomly selected non-disturbed plots on 12 tree islands. We also examined relationships between disturbed area size, canopy cover, and presence of standing water on presence and density of L. microphyllum. Lygodium microphyllum was present in significantly more treefall plots than random non-treefall plots (76% of the treefall plots (N=55) and only 14% of random non-treefall plots (N=55)). Density of L. microphyllum was higher in treefall plots compared to random non-disturbed plots (6.0 stems per m2 for treefall plots; 0.5 stems per m2 for random non-disturbed plots), and L. microphyllum density was correlated with disturbed area size (P = 0.005). Lygodium microphyllum presence in treefall sites was significantly related to canopy cover and presence of water: it was present in five times more treefalls with water than those without. These results suggest that disturbances, such as hurricanes, that result in canopy openings and the creation of disturbed areas with standing water contribute to the ability of L. microphyllum to invade natural areas.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Are invasive species the drivers or passengers of change in degraded ecosystems?
Abstract: Few invaded ecosystems are free from habitat loss and disturbance, leading to uncertainty whether dominant invasive species are driving community change or are passengers along for the environmental ride. The ''driver'' model predicts that invaded communities are highly interactive, with subordinate native species being limited or ex- cluded by competition from the exotic dominants. The ''passenger'' model predicts that invaded communities are primarily structured by noninteractive factors (environmental change, dispersal limitation) that are less constraining on the exotics, which thus dominate. We tested these alternative hypotheses in an invaded, fragmented, and fire-suppressed oak savanna. We examined the impact of two invasive dominant perennial grasses on community structure using a reduction (mowing of aboveground biomass) and removal (weeding of above- and belowground biomass) experiment conducted at different seasons and soil depths. We examined the relative importance of competition vs. dispersal limitation with experimental seed additions. Competition by the dominants limits the abundance and re- production of many native and exotic species based on their increased performance with removals and mowing. The treatments resulted in increased light availability and bare soil; soil moisture and N were unaffected. Although competition was limiting for some, 36 of 79 species did not respond to the treatments or declined in the absence of grass cover. Seed additions revealed that some subordinates are dispersal limited; competition alone was insufficient to explain their rarity even though it does exacerbate dispersal inefficiencies by lowering reproduction. While the net effects of the dominants were negative, their presence restricted woody plants, facilitated seedling survival with moderate disturbance (i.e., treatments applied in the fall), or was not the primary limiting factor for the occurrence of some species. Finally, the species most functionally distinct from the dominants (forbs, woody plants) responded most significantly to the treatments. This suggests that relative abundance is determined more by trade-offs relating to environmental conditions (long- term fire suppression) than to traits relating to resource capture (which should most impact functionally similar species). This points toward the passenger model as the underlying cause of exotic dominance, although their combined effects (suppressive and facilitative) on community structure are substantial.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Scaling Disturbance Instead of Richness to Better Understand Anthropogenic Impacts on Biodiversity
Abstract: A primary impediment to understanding how species diversity and anthropogenic disturbance are related is that both diversity and disturbance can depend on the scales at which they are sampled. While the scale dependence of diversity estimation has received substantial attention, the scale dependence of disturbance estimation has been essentially overlooked. Here, we break from conventional examination of the diversity-disturbance relationship by holding the area over which species richness is estimated constant and instead manipulating the area over which human disturbance is measured. In the boreal forest ecoregion of Alberta, Canada, we test the dependence of species richness on disturbance scale, the scale-dependence of the intermediate disturbance hypothesis, and the consistency of these patterns in native versus exotic species and among human disturbance types. We related field observed species richness in 1 ha surveys of 372 boreal vascular plant communities to remotely sensed measures of human disturbance extent at two survey scales: local (1 ha) and landscape (18 km2). Supporting the intermediate disturbance hypothesis, species richness-disturbance relationships were quadratic at both local and landscape scales of disturbance measurement. This suggests the shape of richness-disturbance relationships is independent of the scale at which disturbance is assessed, despite that local diversity is influenced by disturbance at different scales by different mechanisms, such as direct removal of individuals (local) or indirect alteration of propagule supply (landscape). By contrast, predictions of species richness did depend on scale of disturbance measurement: with high local disturbance richness was double that under high landscape disturbance.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Predicting Richness of Native, Rare, and Exotic Plants in Response to Habitat and Disturbance Variables across a Variegated Landscape
Abstract: Species richness of native, rare native, and exotic understorey plants was recorded at 120 sites in temperate grassy vegetation in New South Wales. Linear models were used to predict the effects of environment and disturbance on the richness of each of these groups. Total native species and rare native species showed similar responses, with rich- ness declining on sites of increasing natural fertility of par- ent material as well as declining under conditions of water
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Disturbance-mediated competition and the spread of Phragmites australis in a coastal marsh
Abstract: In recent decades the grass Phragmites australis has been aggressively in- vading coastal, tidal marshes of North America, and in many areas it is now considered a nuisance species. While P. australis has historically been restricted to the relatively benign upper border of brackish and salt marshes, it has been expanding seaward into more phys- iologically stressful regions. Here we test a leading hypothesis that the spread of P. australis is due to anthropogenic modification of coastal marshes. We did a field experiment along natural borders between stands of P. australis and the other dominant grasses and rushes (i.e., matrix vegetation) in a brackish marsh in Rhode Island, USA. We applied a pulse disturbance in one year by removing or not removing neighboring matrix vegetation and adding three levels of nutrients (specifically nitrogen) in a factorial design, and then we monitored the aboveground performance of P. australis and the matrix vegetation. Both disturbances increased the density, height, and biomass of shoots of P. australis, and the effects of fertilization were more pronounced where matrix vegetation was removed. Clear- ing competing matrix vegetation also increased the distance that shoots expanded and their reproductive output, both indicators of the potential for P. australis to spread within and among local marshes. In contrast, the biomass of the matrix vegetation decreased with increasing severity of disturbance. Disturbance increased the total aboveground production of plants in the marsh as matrix vegetation was displaced by P. australis. A greenhouse experiment showed that, with increasing nutrient levels, P. australis allocates proportionally more of its biomass to aboveground structures used for spread than to belowground struc- tures used for nutrient acquisition. Therefore, disturbances that enrich nutrients or remove competitors promote the spread of P. australis by reducing belowground competition for nutrients between P. australis and the matrix vegetation, thus allowing P. australis, the largest plant in the marsh, to expand and displace the matrix vegetation. Reducing nutrient load and maintaining buffers of matrix vegetation along the terrestrial-marsh ecotone will, therefore, be important methods of control for this nuisance species.
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Six years of plant community development after clearcut harvesting in western Washington
Abstract: What roles do ruderals and residuals play in early forest succession and how does repeated disturbance affect them? We examined this question by monitoring plant cover and composition on a producti...
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Are invaders disturbance-limited? Conservation of mountain grasslands in Central Argentina
Abstract: Abstract Extensive areas in the mountain grasslands of central Argentina are heavily invaded by alien species from Europe. A decrease in biodiversity and a loss of palatable species is also observed. The invasibility of the tall-grass mountain grassland community was investigated in an experiment of factorial design. Six alien species which are widely distributed in the region were sown in plots where soil disturbance, above-ground biomass removal by cutting and burning were used as treatments. Alien species did not establish in undisturbed plots. All three types of disturbances increased the number and cover of alien species; the effects of soil disturbance and biomass removal was cumulative. Cirsium vulgare and Oenothera erythrosepala were the most efficient alien colonizers. In conditions where disturbances did not continue the cover of aliens started to decrease in the second year, by the end of the third season, only a few adults were established. Consequently, disturbances are needed to maintain ali...
Extracted statement — hypothesis: Disturbance
Research field: Ecology and Evolutionary Biology
Title: Pollution reduces native diversity and increases invader dominance in marine hard-substrate communities
Abstract: Anthropogenic disturbance is considered a risk factor in the establishment of non‐indigenous species (NIS); however, few studies have investigated the role of anthropogenic disturbance in facilitating the establishment and spread of NIS in marine environments. A baseline survey of native and NIS was undertaken in conjunction with a manipulative experiment to determine the effect that heavy metal pollution had on the diversity and invasibility of marine hard‐substrate assemblages. The study was repeated at two sites in each of two harbours in New South Wales, Australia. The survey sampled a total of 47 sessile invertebrate taxa, of which 15 (32%) were identified as native, 19 (40%) as NIS, and 13 (28%) as cryptogenic. Increasing pollution exposure decreased native species diversity at all study sites by between 33% and 50%. In contrast, there was no significant change in the numbers of NIS. Percentage cover was used as a measure of spatial dominance, with increased pollution exposure leading to increased NIS dominance across all sites. At three of the four study sites, assemblages that had previously been dominated by natives changed to become either extensively dominated by NIS or equally occupied by native and NIS alike. No single native or NIS was repeatedly responsible for the observed changes in native species diversity or NIS dominance at all sites. Rather, the observed effects of pollution were driven by a diverse range of taxa and species. These findings have important implications for both the way we assess pollution impacts, and for the management of NIS. When monitoring the response of assemblages to pollution, it is not sufficient to simply assess changes in community diversity. Rather, it is important to distinguish native from NIS components since both are expected to respond differently. In order to successfully manage current NIS, we first need to address levels of pollution within recipient systems in an effort to bolster the resilience of native communities to invasion.
Extracted statement — hypothesis: Disturbance