The aim was to estimate the impacts of invasive Impatiens parviflora on forests' herbal layer communities. A replicated Before-After-Control-Impact field experiment and comparisons with adjacent ...uninvaded plots were used. The alien's impact on species richness was tested using hierarchical generalized mixed effect models with Poisson error structure. Impact on species composition was tested using multivariate models (DCA, CCA, RDA) and Monte-Carlo permutation tests. Removal plots did not differ in native species richness from neither invaded nor adjacent uninvaded plots, both when the treatment's main effect or its interaction with sampling time was tested (Chi(2) = 0.4757, DF = 2, p = 0.7883; Chi(2) = 7.229, DF = 8, p = 0.5121 respectively). On the contrary, ordination models revealed differences in the development of plots following the treatments (p = 0.034) with the invaded plots differing from the adjacent uninvaded (p = 0.002). Impatiens parviflora is highly unlikely to impact native species richness of invaded communities, which may be associated with its limited ability to create a dense canopy, a modest root system or the fact the I. parviflora does not represent a novel and distinctive dominant to the invaded communities. Concerning its potential impacts on species composition, the presence of native clonal species (Athyrium filix-femina, Dryopteris filix-mas, Fragaria moschata, Luzula luzuloides, Poa nemoralis) on the adjacent uninvaded plots likely makes them different from the invaded plots. However, these competitive and strong species are more likely to prevent the invasion of I. parviflora on the adjacent uninvaded plots rather than being themselves eliminated from the invaded communities.
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1. Much attention has been paid to negative effects of alien species on resident communities but studies that quantify community-level effects of a number of invasive plants are scarce. We address ...this issue by assessing the impact of 13 species invasive in the Czech Republic on a wide range of plant communities. 2. Vegetation in invaded and uninvaded plots with similar site conditions was sampled. All species of vascular plants were recorded, their covers were estimated and used as importance values for calculating the Shannon diversity index H', evenness J and Sørensen index of similarity between invaded and uninvaded vegetation. 3. With the exception of two invasive species, species richness, diversity and evenness were reduced in invaded plots. Species exhibiting the greatest impact reduced species numbers per plot and the total number of species recorded in the communities sampled by almost 90%. A strong reduction of species number at the plot scale resulted in a marked reduction in the total species number at the landscape scale, and in less similarity between invaded and uninvaded vegetation. The decrease in species richness in invaded compared to uninvaded plots is largely driven by the identity of the invading species, whereas the major determinants of the decrease in Shannon diversity and evenness are the cover and height of invading species, and differences between height and cover of invading and dominant native species, independent of species identity. 4. Synthesis. Management decisions based on impact need to distinguish between invasive species, as their effects on diversity and composition of resident vegetation differ largely. Tall invading species capable of forming populations with the cover markedly greater than that of native dominant species exert the most severe effects on species diversity and evenness. Since a strong impact on the community scale is associated with reduction in species diversity at higher scales, invaders with a high impact represent a serious hazard to the landscape.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
With the growing body of literature assessing the impact of invasive alien plants on resident species and ecosystems, a comprehensive assessment of the relationship between invasive species traits ...and environmental settings of invasion on the characteristics of impacts is needed. Based on 287 publications with 1551 individual cases that addressed the impact of 167 invasive plant species belonging to 49 families, we present the first global overview of frequencies of significant and non‐significant ecological impacts and their directions on 15 outcomes related to the responses of resident populations, species, communities and ecosystems. Species and community outcomes tend to decline following invasions, especially those for plants, but the abundance and richness of the soil biota, as well as concentrations of soil nutrients and water, more often increase than decrease following invasion. Data mining tools revealed that invasive plants exert consistent significant impacts on some outcomes (survival of resident biota, activity of resident animals, resident community productivity, mineral and nutrient content in plant tissues, and fire frequency and intensity), whereas for outcomes at the community level, such as species richness, diversity and soil resources, the significance of impacts is determined by interactions between species traits and the biome invaded. The latter outcomes are most likely to be impacted by annual grasses, and by wind pollinated trees invading mediterranean or tropical biomes. One of the clearest signals in this analysis is that invasive plants are far more likely to cause significant impacts on resident plant and animal richness on islands rather than mainland. This study shows that there is no universal measure of impact and the pattern observed depends on the ecological measure examined. Although impact is strongly context dependent, some species traits, especially life form, stature and pollination syndrome, may provide a means to predict impact, regardless of the particular habitat and geographical region invaded.
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Questions: How is the loss of plant species richness, associated with invasions, related to changes in functional diversity? What is the relationship between the traits of invasive species and those ...of invaded communities? Location: Different Central European vegetation types within the Czech Republic. Methods: Functional diversity was calculated for 260-paired relevés, half non-invaded and half invaded by one of 13 widespread invasive species in Central Europe. Four traits (height, SLA, seed mass and clonal index) were considered as a way to understand the functional space occupied by native and alien species in the data set (410 species altogether). Results: Some of the functional diversity (FD) indices used (mean trait dissimilarity, mean nearest neighbour dissimilarity and SD of the mean nearest neighbour dissimilarity) revealed higher trait diversity for the invaded vegetation and negative relationship with species richness, while functional richness and evenness gave higher values for the uninvaded vegetation and positive relationship with species richness. Adding hypothetically the invader into the FD calculations for the uninvaded vegetation was found to increase most of the FD indices used, while excluding it from the FD calculations of the invaded vegetation decreased functional richness and also mean trait dissimilarity. Conclusions: Results suggest that invading aliens tend to be functionally different from native species and are therefore likely to occupy an empty niche in the invaded vegetation. Similarly, the resident species in the non-invaded communities are not likely to occupy the whole potential niche space, which could remain available for the invasive species with different traits. This study suggests that the probability of a successful invasion is related to functional dissimilarities between the alien invader and native species of the resident communities.
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To identify factors that drive plant species richness in South-African savanna and explore their relative importance, we sampled plant communities across habitats differing in water availability, ...disturbance, and bedrock, using the Kruger National Park as a model system. We made plant inventories in 60 plots of 50 × 50 m, located in three distinct habitats: (i) at perennial rivers, (ii) at seasonal rivers with water available only during the rainy season, and (iii) on crests, at least ~ 5 km away from any water source. We predicted that large herbivores would utilise seasonal rivers' habitats less intensely than those along perennial rivers where water is available throughout the year, including dry periods. Plots on granite harboured more herbaceous and shrub species than plots on basalt. The dry crests were poorer in herb species than both seasonal and perennial rivers. Seasonal rivers harboured the highest numbers of shrub species, in accordance with the prediction of the highest species richness at relatively low levels of disturbance and low stress from the lack of water. The crests, exposed to relatively low pressure from grazing but stressed by the lack of water, are important from the conservation perspective because they harbour typical, sometimes rare savanna species, and so are seasonal rivers whose shrub richness is stimulated and maintained by the combination of moderate disturbance imposed by herbivores and position in the middle of the water availability gradient. To capture the complexity of determinants of species richness in KNP, we complemented the analysis of the above local factors by exploring large-scale factors related to climate, vegetation productivity, the character of dominant vegetation, and landscape features. The strongest factor was temperature; areas with the highest temperatures reveal lower species richness. Our results also suggest that Colophospermum mopane, a dominant woody species in the north of KNP is not the ultimate cause of the lower plant diversity in this part of the park.
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Recent research on plant invasions indicates that some parts of the world are understudied with temperate Asia among them. To contribute towards closing this gap, we provide a standardized list of ...invasive alien plant species with their distributions in 45 Russian regions, and relate the variation in their richness to climate, socioeconomic parameters and human influence. In total, we report 354 invasive alien species. There are, on average, 27 ± 17 (mean ± SD) invasive plants per region, and the invasive species richness varies from zero in Karelia to 71 in Kaluga. In the European part of Russia, there are 277 invasive species in total, in Siberia 70, and in the Far East 79. The most widespread invaders are, in terms of the number of regions from which they are reported,
Acer negundo
,
Echinocystis lobata
(recorded in 34 regions),
Erigeron canadensis
and
Elodea canadensis
(recorded in 30 regions). Most invasive species in Russia originate from other parts of temperate Asia and Europe. There were significant differences in the representation of life forms between the European, Siberian and Far East biogeographical regions, with perennials being over-represented in the Far East, and shrubs in the European part of Russia. The richness of invasive species can be explained by climatic factors, human population density and the percentage of urban population in a region. This publication and the associated dataset is the first comprehensive treatment of the invasive flora of Russia using standardized criteria and covering 83% of the territory of this country.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The accelerating rates of international trade, travel, and transport in the latter half of the twentieth century have led to the progressive mixing of biota from across the world and the number of ...species introduced to new regions continues to increase. The importance of biogeographic, climatic, economic, and demographic factors as drivers of this trend is increasingly being realized but as yet there is no consensus regarding their relative importance. Whereas little may be done to mitigate the effects of geography and climate on invasions, a wider range of options may exist to moderate the impacts of economic and demographic drivers. Here we use the most recent data available from Europe to partition between macroecological, economic, and demographic variables the variation in alien species richness of bryophytes, fungi, vascular plants, terrestrial insects, aquatic invertebrates, fish, amphibians, reptiles, birds, and mammals. Only national wealth and human population density were statistically significant predictors in the majority of models when analyzed jointly with climate, geography, and land cover. The economic and demographic variables reflect the intensity of human activities and integrate the effect of factors that directly determine the outcome of invasion such as propagule pressure, pathways of introduction, eutrophication, and the intensity of anthropogenic disturbance. The strong influence of economic and demographic variables on the levels of invasion by alien species demonstrates that future solutions to the problem of biological invasions at a national scale lie in mitigating the negative environmental consequences of human activities that generate wealth and by promoting more sustainable population growth.
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The paper provides an inventory of the naturalized vascular flora of Ghana, based on newly gathered information from the literature and consultations with local experts. We adopted a rather ...conservative approach by including only species for which strong evidence exists that they are alien in Ghana. We recorded 291 species of naturalized alien plants; for 237 of them there is information on their distribution in the 10 administrative regions of Ghana. Twenty-five species (i.e. 8.6% of the total number of naturalized species) are classified as invasive. There are 21 widely distributed species (7.2% of the total naturalized flora) that occur in at least eight regions, and five of them are distributed all over the country:
Azadirachta indica
,
Echinochloa colona
,
Leucaena leucocephala
,
Senna occidentalis
and
S. siamea
. Of these five, the first three are classified as invasive. The naturalized flora of Ghana includes 71 families, with Leguminosae (66 species), Compositae (22) and Poaceae (18) most represented. The majority of species have their native range in South and North America, contributing 161 and 127 species, respectively. Tropical Asia (98 species) and Africa (37 species) are less represented and only three species have their origin in Europe. The dominance of the Americas as a source region is even more pronounced for the subset of invasive species, with this continent accounting for 18 species out of 25 (72%). Annual and biennial/perennial herbs, shrubs and trees are evenly represented in the naturalized alien species pool. Among invasive species, biennial/perennial herbs are markedly over-represented compared to their contribution to the naturalized flora as a whole (52% vs 38%). The same is true for aquatic species (12% vs 2%). Species that occur as naturalized in more than 40 regions in Africa are also more widely distributed within Ghana. The numbers of naturalized species in the administrative regions of Ghana varied from 34 in Upper West to 173 in Greater Accra. These numbers increased with human population density and decreased with distance from the sea, but this pattern was driven by the city of Accra region. The only predictor that remained significant after removing this outlier was the amount of precipitation in the dry period, which was positively associated with the regional richness of naturalized species. This study could serve as a stimulus for other countries in hitherto understudied tropical regions to work towards comprehensive inventories, for which basic data on the alien flora often is still incomplete.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Understanding the responses of vegetation characteristics and soil properties to grazing in different precipitation regimes is useful for the management of rangelands, especially in the arid regions. ...In northeastern Iran, we studied the responses of vegetation to livestock grazing in three regions with different climates: arid, semiarid, and subhumid. In each region, we selected 6–7 pairwise sampling areas of high versus low grazing intensity and six traits of the present species were recorded on 1 m2 plots—five grazed and five ungrazed in each area. The overall fertility was compared using the dissimilarity analysis, and linear mixed‐effect models were used to compare the individual fertility parameters, functional diversity indices, and species traits between the plots with high and low grazing intensity and between the climatic regions. Both climate and grazing, as well as their interaction, affected fertility parameters, functional diversity indices, and the representation of species traits. Grazing reduced functional evenness, height of the community, the representation of annuals, but increased the community leaf area. In the subhumid region, grazing also reduced functional richness. Further, grazing decreased the share of annual species in the semiarid region and seed mass in the arid region. Larger leaf area and seed mass, smaller height and lower share of annuals were associated with intensive grazing. Species with large LA and seed mass, lower height and perennials can be therefore presumed to tolerate trampling and benefit from high nutrient levels, associated with intensive grazing. By providing a detailed view on the impacts of overgrazing, this study highlights the importance of protection from grazing as an effective management tool for maintaining the pastoral ecosystems. In general, the composition of plant traits across the pastures of northeastern Iran was more affected by intensive grazing than by the differences in climate.
We studied responses of soil and vegetation to livestock grazing in the arid, semiarid, and subhumid rangelands in northeastern Iran. Linear mixed‐effect models were used to compare the soil fertility parameters, functional diversity indices, and species ecological traits. Both climate and grazing significantly affected soil fertility parameters. However, functional diversity indices and species traits were more affected by intensive grazing compared to climate.
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Human activities have altered the composition of biotas through two fundamental processes: native extinctions and alien introductions. Both processes affect the taxonomic (i.e., species identity) and ...phylogenetic (i.e., species evolutionary history) structure of species assemblages. However, it is not known what the relative magnitude of these effects is at large spatial scales. Here we analyze the large-scale effects of plant extinctions and introductions on taxonomic and phylogenetic diversity of floras across Europe, using data from 23 regions. Considering both native losses and alien additions in concert reveals that plant invasions since AD 1500 exceeded extinctions, resulting in (i) increased taxonomic diversity (i.e., species richness) but decreased phylogenetic diversity within European regions, and (ii) increased taxonomic and phylogenetic similarity among European regions. Those extinct species were phylogenetically and taxonomically unique and typical of individual regions, and extinctions usually were not continent-wide and therefore led to differentiation. By contrast, because introduced alien species tended to be closely related to native species, the floristic differentiation due to species extinction was lessened by taxonomic and phylogenetic homogenization effects. This was especially due to species that are alien to a region but native to other parts of Europe. As a result, floras of many European regions have partly lost and will continue to lose their uniqueness. The results suggest that biodiversity needs to be assessed in terms of both species taxonomic and phylogenetic identity, but the latter is rarely used as a metric of the biodiversity dynamics.
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