Resident Species Richness Research Articles

Resistance against tree encroachment is driven by richness and identity of herbaceous resident species

AbstractAimsHerbaceous plant cover can be used to inhibit tree encroachment in many managed and semi‐natural grasslands. Ideally, herbaceous seed mixtures should reduce the establishment and growth of many invading tree species over several years. Theory predicts that invasion resistance can be maximized by both: (a) increasing the diversity (taxonomic and/or functional) of resident seed mixtures, and (b) including species that are especially efficient at blocking further colonizers. We established an experiment in a regularly mown old field within a deciduous forest region in southeastern Canada. Our overall goal was to examine the relative contribution of old field community composition and diversity (taxonomic and functional) to resistance against encroachment by two undesirable native tree species over time.LocationVarennes, southern Québec, Canada (45°37′01.24″ N, 73°23′03.57″ W).MethodsWe tested our hypotheses by seeding experimental plots with different levels of taxonomic diversity (from one to nine species) and functional group richness (grasses, legumes, and forbs). Our herbaceous species comprised four native species and five introduced and naturalized species. We then seeded the plots with two model tree colonizers, Acer rubrum and Betula populifolia, during three consecutive years. We also transplanted seedlings of Acer and Betula to determine the effect of herbaceous diversity on post‐emergence growth and seedling survival.ResultsOverall, herbaceous species identity (presence and absence) better predicted the resistance of resident herbaceous seed mixtures to tree encroachment than the other diversity measures assessed in our study. Fast‐growing herbaceous species, such as Lolium, substantially inhibit resistance to woody encroachment in the first year. Achillea millefolium and Solidago canadensis were by far the most efficient in blocking tree seedling establishment and growth, particularly during the second and third years. These effects highlight the potential for a combination of fast‐growing species, along with slower‐growing but highly inhibitive species, as a way to limit tree encroachment in real field applications. Functional group richness was a poor predictor of tree encroachment. Species richness reduced tree encroachment, especially when considering a multidimensional tree encroachment index integrating all aspects of tree establishment and growth over the three years of our experiment.ConclusionsSeeding highly inhibiting herbaceous species is the most efficient approach against specific tree invaders. However, it is difficult to implement in practice because it relies on a priori knowledge of the species’ inhibitory effects. In the absence of this knowledge, the taxonomic richness of seed mixtures should be increased to prevent tree encroachment.

The relationship between the abundance of non-native tree species and the community structure of resident woody species in tropical montane forest of West Usambara Mountains, Tanzania

The relationship between the abundance of non-native tree species and the community structure of resident woody species in tropical montane forest of West Usambara Mountains, Tanzania

Are the same factors determining biodiversity in cities across different regions? Comparing drivers of urban bird richness patterns in Southern Asia vs. Western Europe

AbstractAccording to general urban ecological understanding, bird species richness declines in highly urban areas due to the increasing extent of built-up areas, and decreasing proportions of green areas. However, this hypothesis is mainly based on studies conducted in cities located in the Global North and rarely in the Global South. We aimed to assess whether existing conceptual understandings of drivers of bird species richness patterns within cities are similar across different regions, specifically Southern Asia (in the Global South) vs. Western Europe (in the Global North). Using avian occurrence data drawn from GBIF (gbif.org), we estimated resident bird species richness in 943 selected grid cells (each cell corresponding to approximately 1 km2 area) distributed in 24 cities, 13 in Southern Asia and 11 in Western Europe. We applied generalised linear mixed models to relate resident bird richness with different explanatory variables of gradients of urbanisation, habitat and climatic factors using the selected grid cells as sampling units. Our results showed that bird richness declined with increasing human built-up and settlement extent (imperviousness) in both regions, but this relationship was stronger in Southern Asia compared to Western Europe. Bird richness also sharply declined in urban areas located far from inland waterbodies, but only in Southern Asia. Our findings suggest that high imperviousness drives bird richness decline, but this process appears to be more pronounced in regions where rapid urbanisation is ongoing. Urban planning integrating green spaces throughout cities is crucial in Southern Asia, as it is in Western Europe, to benefit both people and biodiversity.

Finding the sweet spot in camera trapping: A global synthesis and meta‐analysis of minimum sampling effort

SummaryCamera traps are one of the most common tools in wildlife and conservation biology. Sampling can document and measure animal presence and activity. Captures can be used to estimate population parameters such as presence, abundance, habitat suitability, and resident species richness of specific populations. Effective camera trapping is relevant to conservation for many reasons. For instance, they can be used to inform pre‐ and post‐restoration efforts, monitor the use of artificial structures by species and assess behaviours like predator–prey interactions. This sampling approach can aid in assessing diversity change, habitat change, pre‐ and post‐restoration efforts, artificial structure effects, species presence, and animal behaviour. We reviewed the literature to collect data and estimate incidence effect size measures for both vertebrate abundance and vertebrate richness to examine the relative efficacy of deploying more camera traps for a given period in different ecosystems. Increasing sampling effort through an increased number of cameras significantly increased net positive abundance detection rates in grasslands and mixed ecosystems. Net richness detection rates in mixed, tropical, deciduous, and grassland ecosystems similarly increased with the number of cameras deployed. The total number of days, however, was not a significant predictor of abundance or richness rates detected in any ecosystem. These findings suggest that deploying relatively more cameras for relatively fewer days provides the most effective estimates of vertebrate abundance and richness for a region.

The influencing factors for distribution patterns of resident and migrant bird species richness along elevational gradients.

The latitudinal and elevational patterns of species richness of resident and migrant birds have been of interest to researchers over the past few decades, and various hypotheses have been proposed to explain the factors that may affect these patterns. This study aimed to shed light on the elevational distribution patterns of resident and migrant bird species richness by examining biotic and abiotic factors such as climate, and habitat heterogeneity using a piecewise structural equation model (pSEM). The overall pattern of resident species richness showed a decreasing trend with increasing elevation, whereas that of migrant species richness showed an increasing trend. The mid-peak pattern of species richness was affected by a combination of resident and migrant species and not by either resident or migrant species. Our results showed that resident species were distributed in lower elevation regions with higher mean spring temperatures, whereas migrant species were found in higher elevation regions with lower mean spring temperatures and higher overstory vegetation coverage. Although high elevation conditions might adversely affect the reproduction of migrant birds, higher overstory vegetation coverage at high elevations seemed to compensate for this by providing a better nesting and roosting environment. Despite the significance of habitat diversity and understory vegetation coverage in univariate linear regression models, multiple regression models of the interconnection of ecological processes demonstrated that mean spring temperature and overstory vegetation coverage were more explanatory than other variables.

Winter conditions structure extratropical patterns of species richness of amphibians, birds and mammals globally

AbstractAimThe aim was to derive global indices of winter conditions and examine their relationships with species richness patterns outside of the tropics.LocationAll extratropical areas (>25° N and 25° S latitudes), excluding islands.Time period2000–2018.Major taxa studiedAmphibians, birds and mammals.MethodsWe mapped three global indices of winter conditions [number of days of frozen ground (length of frozen ground winter); snow cover variability; and lack of subnivium (below‐snow refuge)] from satellite data, then used generalized additive models to examine their relationships with species richness patterns derived from range data.ResultsLength of frozen ground winter was the strongest predictor of species richness, with a consistent cross‐taxonomic decline in species richness occurring beyond 3 months of winter. It also often outperformed other environmental predictors of species richness patterns commonly used in biodiversity studies, including climate variables, primary productivity and elevation. In areas with ≥3 months of winter conditions, all three winter indices explained much of the deviance in amphibian, mammal and resident bird species richness. Mammals exhibited a stronger relationship with snow cover variability and lack of subnivium than the other taxa. Species richness of fully migratory species of birds peaked at c. 5.5 months of winter, coinciding with low species richness of residents.Main conclusionsOur study demonstrates that winter structures latitudinal and elevational gradients of extratropical terrestrial species richness. In a rapidly warming world, tracking the seasonal dynamics of frozen ground and snow cover will be essential for predicting the consequences of climate change on species, communities and ecosystems. The indices of winter conditions we developed from satellite imagery provide an effective means of monitoring these dynamics into the future.

Tropical intertidal seagrass beds as fish habitat: Similarities between fish assemblages of intertidal and subtidal seagrass beds in the Philippines

Tropical intertidal seagrass beds have recently been identified as foraging grounds for multiple fish species, although the possible drivers of fish migration to such beds remain unknown. Investigations of fishes occurring in intertidal and subtidal seagrass beds, and comparison of food resources of the dominant trophic groups in the intertidal and subtidal beds, and surrounding bare-sand areas, were conducted at two sites in northern Mindanao, Philippines. Fish species collected in the intertidal and subtidal seagrass beds overlapped by 65%, with species richness and abundance of both residents and visitors between the two habitats not differing substantially (although significantly higher than in intertidal and subtidal bare-sand areas), as many site-attached residents appeared to remain in the intertidal beds during low tide. Benthic-invertebrate feeders, including juveniles of commercially important species, dominated intertidal seagrass beds, comprising >70% of species richness and abundance. Four of them ( Halichoeres argus , H. papilionaceous , Lethrinus harak , and Parupeneus barberinus ) fed primarily on small crustaceans, such as harpacticoid copepods and amphipods, the densities of such food resources being significantly higher in the intertidal and subtidal seagrass beds than in the surrounding bare-sand areas. The results demonstrated that intertidal seagrass beds function as foraging grounds for many visiting fishes, in addition to providing a permanent habitat for resident species. Recognition of the importance of tropical intertidal seagrass beds as fish habitat has significant implications for the management and protection of coastal fish biodiversity and fishery resources. • Many resident and visitor fishes utilize intertidal seagrass beds in the Philippines. • Fish assemblage highly overlapped between intertidal and subtidal seagrass beds. • Benthivorous fishes and their prey items are abundant in intertidal seagrass beds. • Tropical intertidal seagrass beds provide permanent and foraging habitats for fishes.

Suitability of open digital species records for assessing biodiversity patterns in cities: a case study using avian records

Abstract Openly available species observation records on various online platforms achieve good coverage in urban areas. Thus, such digital data could provide a basis for biodiversity assessments in cities. Here, we investigated suitability of open digital species occurrence data, compared with systematically field surveyed data, in Freiburg, Germany (a Western city) and Dhaka, Bangladesh (a global-South city). We focused on resident bird species richness as an indicator of local biodiversity. We collected avian records for urban areas from ‘ornitho.de’ in Freiburg and ‘gbif.org’ in Dhaka. Additionally, we conducted point count surveys at several urban locations in both cities. Using these records, we prepared three grid (cell size 250 m × 250 m) based datasets—open digital dataset (i.e. records compiled from well-surveyed grid cells), field surveyed dataset (i.e. records of systematic bird surveys) and combined dataset (i.e. digital data and field data combined). We compared the relationship of resident bird richness with different habitat factors by applying linear regression models, separately using each of the three datasets. We assessed suitability of data from online platforms by comparing the variables retained after model selection based on digital data versus field surveyed data. We found that field surveyed data and combined data did not alter general understanding of the key driving factors of bird richness patterns we obtained from open digital data. This held for both case examples, Freiburg vs. Dhaka, respectively. This suggests that open digital data from well-surveyed urban locations can provide a suitable basis to assess drivers of biodiversity patterns within cities.

The effects of residential greenspace on avian Biodiversity in Beijing

Residential communities are the primary living spaces for people in China. Their associated greenspaces are important elements of the urban ecosystem, providing neighborhood ecosystem services and hosting bird populations of differing community structures compared with other urban green areas. This study analyzes avian community characteristics within residential communities and their differences compared with urban parks in Beijing. Furthermore, we assess the key environmental factors determining species composition and population sizes and the spatial scales at which these factors are most significant. We randomly selected 27 residential communities to assess the habitat structure and landscape characteristics that underpin residential avian assemblages across multiple spatial scales. Independent sample t-test and model selection methods based on AICc were used for data analysis. Eurasian Tree Sparrow (Passer montanus) (hereafter ETS) alone accounted for 91.0% of total individuals. Compared with urban parks, more migrants and omnivores were found in residential communities. Within-site forest patch connectivity simultaneously decided resident species diversity and individual abundance, with the exception of ETS. Tree species richness and coverage are key predictors for resident species richness and ETS numbers, respectively. Even in the most urbanized species, ETS retained ecological attributes found in “wilder” settings. Residential communities skewed toward avian communities with dominant numbers of ETS. In these low-quality habitats, our results suggest that landscape configuration is more important than local habitat structure. Within-site habitat connectivity and the number of surrounding forest patches with shorter between-patch distances deserve more attention in future landscape design for residential communities.

The interaction of imperviousness and habitat heterogeneity drives bird richness patterns in south Asian cities

Bird species richness has often been used as an indicator of urbanisation effects on biodiversity in North America and Europe, but similar studies are rare in rapidly urbanising regions in the tropics. Here we assess the effect of different urban environmental factors on local resident bird species richness at different spatial extents in South Asian cities. Bird data at 57 urban locations distributed across 11 cities were retrieved from the available literature. Different variables assessing the degree of urbanisation and urban habitat factors were measured, at 1000 m and 5000 m radius scale extent, for each urban location. We investigated how resident bird species richness was affected by urban environmental predictors by fitting linear regression models in a Bayesian framework. Our model suggested strong positive influence of the interaction between habitat Shannon metric (a proxy of habitat heterogeneity) and proportion of impervious surface (a proxy of human built-up and settlement extent) on local resident bird richness at both spatial scales. Increasing values of habitat Shannon metric positively related to increasing bird richness, but only when the proportion of impervious surface was very high. Our results suggest that areas with a high degree of urbanisation necessitate an increase of habitat heterogeneity to maintain high local bird diversity. Increasing the quality and the compositional variability of remaining bird habitat patches in highly built-up areas should be a major conservation concern within cities of South Asia.

Nutrient fluctuation has different effects on a tropical invader in communities from the native and non-native range

Invader success might depend on both nutrient availability and species richness of the resident community. Here, we combine these ideas in a single experiment, testing whether the Fluctuating resource and biotic resistance hypotheses might be contingent upon one another. The fluctuating resource hypothesis proposes that resource fluctuation might facilitate the successful invasion of exotic plants if invaders are better than natives at taking advantage of resource pulses. The biotic resistance hypothesis proposed that more species rich communities might be more resistant to invasion, due to greater competition for resources with greater native richness. Here, we use an experiment with the invader, Chromolaena odorata in 315 artificial communities with resident plants from native and non-native ranges. We found that resident origin, nutrient treatment and species richness of artificial community have significant effects on invasion success of C. odorata. The effect of nutrient fluctuation on invasion success was contingent on resident origin (native vs. non-native range), and this effect was weaker in more species rich communities. In addition, the invasion success of C. odorata was negatively related with biomass of resident plants, suggesting competition as a mechanism governing invader success. Our results suggest a novel twist on the fluctuating resource hypothesis: fluctuating resources may favor invaders more in species poor communities of non-native origin. This also suggests that competition for fluctuating resources may be one mechanism governing biotic resistance because the effects of richness were greater when resources were fluctuating. Our results suggest that the fluctuating resource hypothesis will apply only to resident communities with lower resource acquisition strategies, relative to the invader.

Effect of the invasive exotic herb Centaurea solstitialis on plant communities of a semiarid ecosystem

ABSTRACT Background The effects of many invasive species on invaded communities are still scarcely known. Centaurea solstitialis is an invasive Eurasian herb, widely distributed around the world, but its effects on recipient communities are not well known. Aims To evaluate the effect of C. solstitialis invasion on richness and cover of native and exotic resident species in naturally established communities. Methods We repeated a field experiment in three old-fields of central Chile where C. solstitialis was not present. The experiment simulated the invasion of C. solstitialis by adding 600 seeds per plots of 1 × 1 m in size and compared the richness and cover of all naturally growing species in plots with and without C. solstitialis. Results For exotics, initial species richness (average ca.18% and 20% per site), and cover (average ca. 20% and 34% per site) were significantly reduced by C. solstitialis in two out of the three sites. The abundances of four out of 17 exotic resident species were negatively affected by C. solstitialis. Native species were not affected by C. solstitialis. Conclusions C. solstitialis can outcompete resident species of communities where it invades, but local ecological factors influence its effects producing different impacts among species and localities.

Noise level and water distance drive resident and migratory bird species richness within a Neotropical megacity

A large body of evidence indicates that urbanization profoundly affects ecological communities, but the extent to which patterns are generalizable across regions, such as in the Neotropics, remains unclear. We examined responses of migratory and resident birds to human disturbance and habitat attributes in São Paulo, Brazil, a tropical megacity in South America. In 2017–2018, we surveyed birds across 31 landscapes distributed across the urban landscape and evaluated competing models that included five non-correlated variables explaining variation in species richness: ambient noise level, distance to water, tree cover, human population size, and impervious surface. We recorded 142 bird species, 128 of which were resident and 14 migratory. Richness of both resident and migratory birds declined with increasing noise level and distance to water, which best explained variation in bird communities among the sampled landscapes. Although resident and migratory birds presented similar response patterns to local and landscape attributes, noise level was the best predictor of migratory species occurrence, whereas distance to water best explained the occurrence of resident species. Our results suggest that, although tree cover is important to biodiversity in urbanized landscapes, proper management of urban water bodies and reduction of noise levels are also essential to maintaining avian diversity within tropical urban areas and suggest novel avenues for future research in tropical urban ecology.

Richness, phylogenetic diversity, and abundance all have positive effects on invader performance in an arid ecosystem

AbstractIn search of generalities in biological invasions, it is sometimes forgotten that invader success can be a function of both the diversity of the invaded community and the relatedness of the invader relative to community residents. Both qualities are likely to be especially important in stressful ecosystems, and identifying the species and community attributes that influence biological invasions can help direct management efforts in a sensitive ecosystem like those in arid regions. Pink Morning Glory, Ipomoea carnea Jaq. (Family: Convolvulaceae), is an annual vine native to Central and South America and is invasive in Egypt. We examined the performance of I. carnea at different densities in assembled communities of Egyptian annual native species. The native plant communities were manipulated to represent gradients of species richness and phylogenetic diversity and relatedness to I. carnea. We quantified the performance of I. carnea in these communities and examined the contribution of resident species richness, phylogenetic diversity, and phylogenetic relatedness to invader resistance. Our findings revealed that there was a positive relationship between invader performance and its mean phylogenetic distance to the resident species. Furthermore, species‐rich communities with more distantly related species positively contributed to invader performance in contrast to the classic biotic resistance hypothesis. Beyond these positive relationships, a positive density‐dependent effect of I. carnea on its performance was observed. We conclude that facilitative interactions are potentially important drivers promoting the successful invasion of the nonnative species I. carnea in water‐limited and harsh ecosystems. These results suggest that perhaps contrary to understanding from temperate systems, communities with a higher diversity of species could be more likely to be invaded by arid‐adapted species that are distantly related to natives. Thus, policy and management in arid regions should carefully consider reviewing the importation of nonnative species that are phylogenetically distinct and adapted to arid conditions and prioritizing their control once they are established.

Recovery of ecosystem functions after experimental disturbance in 73 grasslands differing in land‐use intensity, plant species richness and community composition

Abstract Drivers of ecosystem stability have been a major topic in ecology for decades. Most studies have focused on the influence of species richness on ecosystem stability and found positive diversity‐stability relationships. However, land use and abiotic factors shape species richness and functional composition of plant communities and may override species richness‐stability relations in managed grasslands. We analysed the relative importance of land‐use intensity (LUI), resident plant species richness and functional composition for recovery of plant communities (plant species richness, plant cover, above‐ and below‐ground biomass) and release of soil nutrients after a severe mechanical disturbance. Experimental sward disturbance was applied to 73 grassland sites along a LUI gradient in three German regions. We considered relative (ln(disturbance/control)) and absolute (disturbance − control) treatment effects. Using structural equation modelling, we disentangled direct effects of LUI and resident species richness on recovery and indirect effects via changes in functional richness. Community‐weighted‐mean traits rarely mattered for recovery or nutrient release, while functional richness especially increased relative recovery of plant communities but also relative release of NO3‐N and NH4‐N. These effects were enhanced by increasing resident plant species richness and decreasing LUI. Next to these indirect influences of LUI and resident plant species richness via functional community composition, grasslands of high compared with grasslands of low resident plant species richness generally showed decreased recovery of plant communities. In grasslands of high LUI, absolute recovery of some aspects of plant communities was decreased. We did not find consistent differences between the relative importance of the different drivers of recovery after the first and the second season. Overall, resident species richness seemed most important for relative recovery and less important for absolute recovery, where direct effects of LUI were more common. Synthesis. The stability of ecosystems in managed grasslands depends on more than species richness. Thus, drivers that directly affect species richness and functional community composition have to be considered when studying the stability of real‐world ecosystems. More specifically, in managed grasslands high resident species richness but also high land‐use intensity (LUI) decreased the stability of ecosystem functions, which was partially buffered by increases in functional richness.

Seasonality in spatial distribution: Climate and land use have contrasting effects on the species richness of breeding and wintering birds.

AimMany studies have examined large‐scale distributions of various taxa and their drivers, emphasizing the importance of climate, topography, and land use. Most studies have dealt with distributions over a single season or annually without considering seasonality. However, animal distributions and their drivers can differ among seasons because many animals migrate to suitable climates and areas with abundant prey resources. We aim to clarify seasonality in bird distributions and their drivers.LocationJapan.MethodsWe examined the effects of climate (annual mean temperature, snow depth), topography (elevation), and land use (extent of surrounding habitat) on bird species richness, in the breeding and wintering seasons separately, using nationwide data (254 forest and 43 grassland sites, respectively). We separately analyzed the species richness of all species, residents, short‐, and long‐distance migrants in forests and grasslands.ResultsIn the breeding season, the annual mean temperature negatively affected all groups (except for forest and grassland residents), and the extent of surrounding habitat positively affected many groups. By contrast, in the wintering season, temperature positively affected all groups (except for forest residents), and the extent of surrounding habitat positively affected only grassland long‐distance migrants. In both seasons, the species richness of forest and grassland residents was high in regions of moderate and high temperature, respectively. Moreover, snow depth negatively affected all forest groups in the wintering season. Mapping expected species richness suggested that regions with different climates served as habitats for different groups during different seasons.Main conclusionsAll regions were important bird habitats depending on the season, reflecting the contrasting effects of temperature across seasons. In the breeding season, surrounding land use was also an important driver. To understand the seasonal role that each region and environment plays in maintaining species/communities, a large‐scale study considering both environmental seasonality and species distribution is needed.

Latitudinal effects of anthropogenic factors driving raptor species richness across the American continent

AbstractAimGeographic gradients in species richness have been traditionally attributed to variation in environmental conditions. However, untangling the importance of human activities in explaining spatial patterns in raptor species richness, still remains a challenge. We evaluated the relative importance of how human impacts and ecogeographical conditions shape the latitudinal patterns of resident (n = 140) and migratory (n = 35) raptor species richness in the American continent, and analysed whether these factors differ between the Nearctic and the Neotropical regions.LocationAmerican Continent.TaxonRaptor species.MethodsWe processed BirdLife distributional data for 175 raptor species distributed in America, and a set of three ecogeographical and three human impact variables at a spatial resolution of 96.5 × 96.5 km. We applied simple, multiple, simultaneous auto‐regressive models and partial regression analyses to explore the associations between ecogeographical conditions and human impacts on raptor richness.ResultsAt the continental scale and the Neotropical region, global forest structure is the main driver of richness patterns for all raptors combined, and for resident and migratory species alone. In the Nearctic region, human accessibility was the best explanatory variable to understand the spatial patterns of richness regardless of the raptor group analysed.Main conclusionsEnvironmental features play a leading role in determining raptor species richness. However, the independent contribution of human activities emerges as an important factor in explaining richness patterns of migratory species at the continental scale and within the Neotropical region, whereas humans become particularly important in the Nearctic region for all raptors, residents and migratory species. We show for the first time how human‐related factors influence raptor species richness.

Effects of bird community dynamics on the seasonal distribution of cultural ecosystem services.

Biodiversity-based cultural ecosystem services (CES), such as birdwatching, are strongly influenced by biotic community dynamics. However, CES models are largely static, relying on single estimates of species richness or land-use/land-cover proxies, and may be inadequate for landscape management of CES supply. Using bird survey data from the Appalachian Mountains (USA), we developed spatial-temporal models of five CES indicators (total bird species richness, and richness of migratory, infrequent, synanthrope, and resident species), reflecting variation in birdwatcher preferences. We analyzed seasonal shifts in birdwatching supply and how those shifts impacted public access to projected birdwatching hotspots. Landscape patterns of CES supply differed substantially among indicators, leading to opposing conclusions about locations of highest birdwatching supply. Total species richness hotspots seldom overlapped with hotspots of migratory or infrequent species. Public access to CES hotspots varied seasonally. Our study suggests that simple, static biodiversity metrics may overlook spatial dynamics important to CES users.

Do invasive alien plants really threaten river bank vegetation? A case study based on plant communities typical for Chenopodium ficifolium-An indicator of large river valleys.

Riparian zones are very rich in species but subjected to strong anthropogenic changes and extremely prone to alien plant invasions, which are considered to be a serious threat to biodiversity. Our aim was to determine the spatial distribution of Chenopodium ficifolium, a species demonstrating strong confinement to large river valleys in Central Europe and an indicator of annual pioneer nitrophilous vegetation developing on river banks, which are considered to be of importance to the European Community. Additionally, the habitat preferences of the species were analysed. Differences in the richness and abundance of species diagnostic for riverside habitats, as well as the contribution of resident and invasive alien species in vegetation plots along three rivers differing in terms of size and anthropogenic impact were also examined. Finally, the effect of invaders on the phytocoenoses typical for C. ficifolium was assessed. The frequency of C. ficifolium clearly decreased with an increasing distance from the river. Among natural habitats, the species mostly preferred the banks of large rivers. The vegetation plots developing on the banks of the three studied rivers differed in total species richness, the number and cover of resident, diagnostic and invasive alien species, as well as in species composition. Our research indicates that abiotic and anthropogenic factors are the most significant drivers of species richness and plant cover of riverbank vegetation, and invasive alien plants affect this type of vegetation to a small extent.

Invasive Species <i>Echinochloa colona</i> Reduces Abundance and Diversity of Resident Plant Communities in Tropical Wetland

Although the relationship between invasive alien species (IAS) and plant community structure has attracted considerable interest, the impacts of IAS on abundance and diversity of resident plant communities in species rich-ecosystems, such as tropical wetlands are poorly understood. Consequently, this has impeded development of improved management strategies and successful restoration of invaded tropical wetlands. Therefore, data on vegetation were collected from 60 plots of 20 × 50 m to study the impacts of alien invasive grass Echinochloa colona (L.) Link abundance on plant community abundance, richness, evenness and diversity of resident plant species within grasslands of the Kilombero Valley wetland, Tanzania. Moreover, the impacts of abundance of E. colona on plant functional groups (i.e. graminoids, forbs and shrubs) richness were also explored. Generalized linear models showed that community richness, evenness, diversity and abundance of resident species were negatively related to the E. colona abundance. There was a negative relationship between richness of graminoids and shrubs and the abundance of E. colona. Similarly, the abundance of graminoids, forbs and shrubs is related negatively to the abundance of E. colona. Given that most of the community and functional group attributes of resident plants is related negatively to E. colona abundance, improved management strategies should be developed to minimize the abundance and further spread of E. colona to restore and conserve wetland biodiversity.