Floristic Homogenization Research Articles

Drivers of plant biodiversity on cemeteries in the Ruhr Metropolitan Region (W Germany)

Cemeteries are biodiversity hotspots in urban areas, while the drivers of their floristic diversity are poorly understood. We investigated 153 cemeteries in the western Ruhr Metropolitan Region and generated comprehensive species lists of wild plants. Altogether, we found 964 species, equivalent to 53.6% of the flora known from the region. Cluster analysis revealed five distinct cemetery types based on their species composition and prevalence. Subsequently, we used ANOVAs to relate the most effective environmental descriptors identified with a CCA to the five clusters, thus revealing the drivers of species composition. Two of the main clusters had clear regional foci, which could be explained by soil types, while the third main cluster included most of the large cemeteries with many different habitat types, and encompassed sites from the entire study region. Here, the number of species is highest. Two smaller clusters included old historic and Jewish cemeteries, respectively, which were characterized by a smaller number of neophytes and heat indicators. Through the various functional types, the cemeteries contribute to the biodiversity of urban areas like the Ruhr Metropolitan Region and thus counteract the floristic homogenization of cities.

Floristic homogenization of South Pacific islands commenced with human arrival

The increasing similarity of plant species composition among distinct areas is leading to the homogenization of ecosystems globally. Human actions such as ecosystem modification, the introduction of non-native plant species and the extinction or extirpation of endemic and native plant species are considered the main drivers of this trend. However, little is known about when floristic homogenization began or about pre-human patterns of floristic similarity. Here we investigate vegetation trends during the past 5,000 years across the tropical, sub-tropical and warm temperate South Pacific using fossil pollen records from 15 sites on 13 islands within the biogeographical realm of Oceania. The site comparisons show that floristic homogenization has increased over the past 5,000 years. Pairwise Bray–Curtis similarity results also show that when two islands were settled by people in a given time interval, their floristic similarity is greater than when one or neither of the islands were settled. Importantly, higher elevation sites, which are less likely to have experienced human impacts, tended to show less floristic homogenization. While biotic homogenization is often referred to as a contemporary issue, we have identified a much earlier trend, likely driven by human colonization of the islands and subsequent impacts.

Naturalizations have led to homogenization of the Malesian flora in the Anthropocene

AbstractAimWorldwide, floras are becoming homogenized at global scales, but regional patterns vary. Here, we present the first assessment for the Malesian phytogeographical region in terms of the timing of introductions, direction, magnitude and drivers of floristic change due to alien plant naturalizations.LocationMalesian phytogeographic region, including Southeast Asia and the Pacific.TaxonTracheophyta (vascular plants).MethodsWe compiled data on first records of naturalized plants in Malesia to investigate temporal trends in the rate and origin of introductions. We then calculated β‐diversity (including turnover and nestedness) for the native, naturalized and Anthropocene (native + naturalized) floras for each pair of island groups (36 pairs), and a homogenization index for the native and Anthropocene floras, using presence/absence data for 31,580 plant species. Mantel tests were used to investigate the geographic, climatic and anthropogenic correlates of dissimilarity and homogenization.ResultsAround 75% of all naturalized species documented to date were already reported for the first time within Malesia prior to 1950. This has led to homogenization between the historic (native) and contemporary (Anthropocene) floras for all island group pairs. Turnover was the most important process for driving compositional dissimilarity between island groups in Malesia in the native and Anthropocene floras, but homogenization resulted from decreases in nestedness and turnover. Differences in average taxonomic homogenization for island groups were associated with differences in their level of anthropogenic modification.Main ConclusionsThis study improves current understanding of the direction and drivers of floristic homogenization in one of the world's most diverse tropical regions. Alien plant introductions carry a long historical legacy in Malesia, and naturalizations of these plants have led to overall taxonomic homogenization of the region's flora. Expected increases in the magnitude of human modification, without appropriate policy, will likely lead to further reductions in the floristic uniqueness of island groups.

The structure of the segetal flora of field crops in the steppe zone of Krasnodar Territory

A comparative analysis of the species composition of the segetal flora of the surveyed steppe zone and the segetal flora of the entire Krasnodar Territory based on the materials of numerous scientific publications is presented. The main part of the floristic spectra of both segetal florae coincides in the composition of the 10 leading families, which attests to their unity. The leading families in the compared lists are Asteraceae Dumort., Poaceae Barnhart, Fabaceae Lindl., and Brassicaceae Burnett. Floristic homogeneity of the weed species compositions between the segetal floras in the areas under different types of field crops is considered. Besides, species with a high degree of permanency in the agrocenoses of each field crop have been identified. These species are objects of phytosanitary risk for a number of field crops or some of them in the steppe zone of Krasnodar Territory. The most common weeds in the fields of all surveyed crops are field bindweed (Convolvulus arvensis L.), common ragweed (Ambrosia artemisiifolia L.), bristly thistle (Cirsium setosum (Willd.) Bess.), and cockspur grass (Echinochloa crusgalli (L.) Beauv.). Information about the predicted widespread species in the fields under a certain crop will make it possible to plan the volume of production or purchase of protective means focusing on groups of dominant species, and anticipate possible changes in the reformatting of the acreage structure, violations of the reclamation system and crop rotation schemes, etc.

Changes of vegetation in coniferous monocultures in the context of conversion to mixed forests in 30 years – Implications for biodiversity restoration

The understorey vegetation of temperate forests harbours a major proportion of terrestrial biodiversity and fulfills an important role in ecosystem functioning. Over the past decades, temperate forest understoreys were found to change in species diversity and composition due to several anthropogenic and natural drivers. Currently, the conversion and restoration of even-aged coniferous monocultures into more diverse and mixed broad-leaved forests are major objectives of sustainable forest management in Central Europe. This forest conversion alters understorey communities and abiotic site conditions but the underlying patterns and processes are not yet fully understood. Therefore, we investigated changes in the Bavarian Spessart mountains in southwest Germany, where we re-sampled 108 semi-permanent plots from four different coniferous stand types (i.e., Norway spruce, Scots pine, Douglas fir, European larch) about 30 years after the initial assessment. On these plots, we recorded understorey vegetation and forest structure, and derived abiotic site conditions based on ecological indicator values of understorey vegetation, followed by multivariate analysis. We found changes in plant communities that point towards a decrease of soil acidity and a “thermophilization” of forest understoreys. Understorey species richness remained constant, while understorey's Shannon and Simpson diversity increased. The observed changes in forest structure explained the temporal shifts in understorey species composition. The understorey species composition did not experience a significant floristic homogenization since the 1990s. However, plant communities exhibited a reduction in species characteristic of coniferous forests and a simultaneous increase in species associated with broad-leaved forests. The increase of specialist species (closed forests and open sites) may have compensated for the detected decrease in generalist species. We conclude that the forest conversion towards mixed broad-leaved forest in the Spessart mountains of the past decades might have masked homogenization trends that are increasingly reported from Central European forest understoreys.

IZE, DENSITY, ECOLOGICAL GROUPS, AND DISPERSAL SYNDROMES OF THE SEED RAIN IN URBAN ATLANTIC FOREST FRAGMENTS IN NORTHEASTERN BRAZIL

Urban expansion has been one of the main factors contributing to the reduction and fragmentation of tropical forests, and such urban green areas are crucial for conserving and maintaining local and regional biodiversity. This study assessed different aspects of the seed rain (seed size, seed density, dispersal syndromes, ecological groups) in two urban Atlantic Forest fragments (Jardim Botânico – 11 ha / Mata do Curado – 106 ha) in Recife, northeastern Brazil. We expected that i) the connectivity and large size would reduce the floristic homogenization in Mata do Curado, ii) the continuous human presence would increase the abundance of non-shaded tolerant species, and iii) in the Jardim Botânico the absence of connectivity and small size would reduce the abundance of shade-tolerant species (large seeds). A total of 50 fruit traps were maintained for 12 months at each site, and visits were performed fortnightly to collect seeds. The collected seeds were quantified, measured (length and width), and categorized into dispersal syndromes (zoochoric, anemochoric, autochoric) and ecological groups (shade and non-shade tolerant). 4,621 seeds were collected in the traps across the study period (Jardim Botânico: 1,778, 7 spp. / Mata do Curado: 2,843, 8 spp. plus 18 morphotypes). Overall, large seeds (15.1 mm - 30 mm) were more abundant in the Jardim Botânico. Zoochoric seeds were longer in length and width in the Mata do Curado. As expected, connectivity and size appeared to contribute to the decrease of floristic homogenization, and human presence increased the abundance of non-shade tolerant seeds in the Mata do Curado. In contrast, albeit small and isolated, the Jardim Botânico demonstrated a higher abundance of shade-tolerant seeds. Our results reinforce the urgency of preserving urban forests to conserve regional biodiversity.

Forest and grassland habitats support pollinator diversity more than wildflowers and sunflower monoculture

Abstract Intensively managed agricultural landscapes often lack suitable habitats to support diverse wildlife, particularly harming pollinator communities. Besides mass flowering crops, remnant patches of natural and semi‐natural vegetation may play a key role in maintaining and conserving biodiversity. Yet, the effects of different natural habitats, including forests and grasslands, on different pollinator communities are poorly understood at the landscape scale. We examined the abundance, richness, and diversity of wild bees and hoverflies, two key pollinator groups, across a land‐use gradient spanning forest edges, grassland, wildflower strips, and sunflower monoculture. We also examined the distribution of hoverfly larvae trophic guilds and wild bee nesting traits across the above‐mentioned land‐use gradient. Finally, we evaluated the impact of landscape structure (forest, grassland, and water cover in the surrounding landscape) on pollinator community composition. Our results indicate that forest and grassland habitats supported a higher abundance and greater richness of pollinators than wildflower strips and sunflower monocultures. Furthermore, hoverflies were more sensitive to habitat and floristic homogenization than wild bees. Sunflower and wildflower habitats also hosted a lower diversity of larvae trophic guilds and wild bee nesting guilds as compared to forests and grasslands. Our study suggests that conserving and restoring forest and grassland habitats within agricultural mosaics may serve as the main ‘refuge’ for wild pollinators.

High‐severity fire drives persistent floristic homogenization in human‐altered forests

AbstractEcological disturbance regimes across the globe are being altered via direct and indirect human influences. Biodiversity loss at multiple scales can be a direct outcome of these shifts. Fire, especially in dry forests, is an ecological disturbance that is experiencing dramatic changes due to climate change, fire suppression, increased human population in fire‐prone areas, and alterations to vegetation composition and structure. Dry western conifer forests that historically experienced frequent, low‐severity fires are now increasingly burning at high severity. Relatively little work has been done looking at the effects of this novel disturbance type on affected plant communities, and little is known about how these impacts change over time. To fill in these knowledge gaps, we examined a fire that burned in a yellow pine and mixed conifer forest in the central Sierra Nevada in California, USA. We sampled at five time steps across the nine years following the fire (1, 3, 5, 8, and 9 years postfire). We found a generally unimodal relationship between fire severity and plant alpha and gamma diversity, but found that areas that burned at high severity supported progressively lower plant diversity as time since fire increased. Similarly, beta diversity decreased drastically through time for the high‐severity areas, while remaining more static in the other severity classes. The combination of these findings indicates that significant floristic homogenization can result from high‐severity fire in this ecosystem type. We also saw consistently lower diversity in unburned areas in comparison to area burned at low and moderate severity, underlining that both lack of fire and high‐severity fire can have negative impacts on postfire plant diversity. Unburned areas that experienced forest thinning after the first sample year saw an increase in plant diversity over time, suggesting that some—but not all—of the effects of fire on plant diversity can be approximated through forest management.

Floristic Homogenization and Differentiation under Deer Grazing in a Subalpine Zone in Central Japan

Changes of vegetation due to deer grazing may result in floristic homogenization or differentiation. The relationships between the changes caused by grazing are still being debated. Vascular plants and grazing by Cervus nippon were recorded in 2010 and 2018 in Betula forests and tall grassland communities in a subalpine zone, central Japan. Species composition differed significantly between vegetation types in both censuses. The α-diversity had declined significantly in both vegetation types. Metrics related to species replacement made a greater contribution to β-diversity than those related to nestedness in both vegetation types. A decrease of β-diversity based on incidence data from 2010 to 2018 in the Betula forests indicated that floristic homogenization had occurred; an increase of β-diversity based on abundance data from 2010 to 2018 in the grasslands indicated that floristic differentiation had occurred. Changes of α-diversity in both vegetation types and of β-diversity in the grasslands were significantly correlated with grazing intensity. These results showed that deterministic processes, which originally differed between the Betula forests and grasslands, would be the dominant causes of floristic changes under deer-grazing pressure.

Biotic homogenization of dendroflora in the conditions of the megapolis (Dnipro, Ukraine)

Purpose. Biodiversity assessment and clarification of the trend towards homogenization of the dendroflora of the Shevchenko Park (Dnipro, Ukraine). Methods. Floristic methods of research are applied - elucidation of the taxonomic composition and selection of the adventitious fraction of dendroflora, methods of species richness assessment (according to the Menkhinik index and Margalef index), determination of floristic commonality (according to the Jaccard index) and floristic homogeneity (according to the Koch index of biotic dispersion), methods of ecological analysis (by biomorphs and ecomorphs), physical, physicochemical, chemical methods of soil analysis, soil biological activity, statistical methods of data processing (descriptive statistics and correlation analysis). Results. It was established that artificial stands of trees in the Shevchenko Park are capable of forming a sufficient amount of viable undergrowth of autochthonous and introduced (adventurous) species, the ratio of which is 37.0% to 63.0%. The amount of tree growth of adventive sites in the areas according to the level of recreational load is distributed as follows: with no load - 38.5% of the number of self-regenerating trees, with moderate - 68.2%, with strong - 80.5%. The indexes of species richness of Margalef and Menkhinik of self-regenerating tree species for the site with a strong recreational load turned out to be the largest (due to adventitious species) compared to the sites with no and moderate recreational load. Koch index of biotic dispersion is 50.0%. Correlation coefficients between the number of allochthonous and autochthonous tree species that have self-regenerated for the studied areas with strong, moderate and no recreational load are statistically significant (0.73, 0.76, 0.77 respectively). Conclusions. On the territory of the investigated areas of the park, there are 14 tree species capable of seed self-regeneration, which taxonomically belong to 12 genera and 10 families. Of them, 9 adventive species were registered, represented by 9 genera and 7 families with the leading family Sapindaceae. The calculated index of biotic dispersion testifies to the presence of a process of floristic homogenization of the forest stand on the territory of the park. As part of the adventitious fraction of the self-regenerating dendroflora, there is an increased invasion of Ailanthus altissima and the occurrence of such neophyte species as Celtis occidentalis and Acer negundo, which indicates the penetration of alien species into the local flora and a potential threat to natural floristic diversity.

Floristic homogenization as a result of the introduction of exotic species in China

AbstractAimThe introduction of exotic plants can both increase (homogenize) and decrease (differentiate) floristic similarity between areas. We have a poor understanding of the degree to which plant species introductions tend to homogenize or differentiate floras, and relevant studies covering large spatial extent are scarce. China has been heavily invaded by exotic plants. Here, we analyse a comprehensive dataset of vascular plants to determine whether the introduction of exotic plant species has homogenized or differentiated species composition in regions across China.LocationChina.MethodsWe calculated the Jaccard index and Simpson index of similarity for each pair of province‐level regions for native and exotic species separately and jointly, and calculated a homogenization index for each pair of regional floras. We correlated species richness of native and exotic plants to climatic factors, and correlated the Jaccard index and Simpson index to geographic and climatic distances. We used variation partitioning analysis to determine the relative importance of geographic and climatic distances on species turnover. We also examined the effect of human population density on florisitic similarity of exotic species.ResultsWe found that the geographic range of each species was, on average, larger for exotics than for natives; floristic similarity between regions was greater for exotics than for natives; the vast majority of pairwise regional floras have been homogenized; the introduction of exotic species has caused stronger biotic homogenization for pairwise floras with greater dissimilarity in their species composition; geographic distributions of exotic and native species were determined by different sets of climatic factors; and distributions of exotic species were determined by climatic factors more strongly, compared to those of native species. Human population density had a moderate effect on florisitic similarity of exotic species.Main conclusionsThe introduction of exotic plant species has homogenized regional floras across China. Because strong international trades between China and other countries and dramatic development of transportation systems are continuing in China, which help spread of exotic species, we predict that exotic species will continue to spread and will strengthen biotic homogenization in China.

Temporal beta diversity patterns reveal global change impacts in closed mountain grasslands

Global changes are recognized as one of the main drivers of biodiversity changes over time, especially in mountain ecosystems. A key approach to detect and investigate the effect of climate and land use change on these ecosystems is represented by vegetation surveys. In this study, based on the resurvey of historical vegetation data, we assessed temporal beta-diversity patterns within and between subalpine and alpine vegetation types in the Dolomiti Bellunesi National Park. Resurvey was focussed on plots sampled in four main vegetation types: 1 and 2) Mesophytic and xerophytic grasslands on neutral or base-rich soils respectively dominated by Sesleria caerulea and Carex sempervirens and by Sesleria caerulea and Helictotrichon parlatorei; 3) Acidophytic grasslands dominated by Nardus stricta; 4) Snowbeds with dominance of dwarf willows (Salix herbacea or S. retusa) or Luzula alpinopilosa. Our results revealed a pattern of floristic homogenization in grasslands and snowbeds indicating a decreasing heterogeneity, both within and between different vegetation types that can be associated with different components of global change. The highest temporal beta diversity and floristic homogenization were detected in snowbeds. In general, the magnitude of temporal changes differ between communities, thus claiming for conservation activities that are tailored to each vegetation type.

Decrease in species richness and diversity, and shrub encroachment in Cerrado grasslands: A 20 years study

AbstractQuestionThe Cerrado is a global biodiversity hotspot, highly threatened by changes in land use. Alterations in species composition and the colonization of Cerrado grasslands by woody species can lead to long‐term changes in these communities. In this study, we investigated changes over 20 years in three grassland areas, in terms of species richness and diversity and growth‐form cover, as well as the effects of shrub and grass encroachment on species richness.LocationCerrado Brazilian savanna, moist grassland and dry shrub grassland. Areas under low and high anthropogenic pressure.MethodsPlant species composition and cover were sampled on seven occasions between the years 2000 and 2020, in permanent line‐transects. We compared plant cover, richness, diversity and growth‐form cover between the periods for each area. Next, we developed mixed‐effect linear models to test whether species richness in grasslands at the latest sampling event was altered by species representing 70% of the species cover at this time.ResultsGrasslands located in areas under higher anthropogenic pressure presented reduced richness and diversity, and cover concentrated on a few species of shrubs and large tussock grasses. Moist grassland undergoing encroachment by the native shrub Trembleya parviflora had lost over 50% of its diversity since encroachment. In the same area, a shrub grassland undergoing encroachment by native shrub Raulinoreitzia tremula, three native grass species and one exotic grass presented significantly reduced species richness. The moist grassland in an area under low anthropogenic pressure showed a reordering of the species cover over time, but a decrease in species richness.ConclusionWe observed changes in plant richness, diversity, cover, composition and growth‐form cover over a period of 20 years in grassland communities. We found, however, different trajectories in the three grassland areas sampled, mainly due to the encroachment of a few species, leading to floristic homogenization in grasslands located in areas under high anthropogenic pressure.

BIOECOLOGICAL ASSESSMENT OF THE STATE OF THE ADVENTITIOUS FRACTION OF THE DENDROFLORA OF RECREATIONAL AND PARK LANDSCAPES (DNIPRO)

The state of seed self-regeneration of woody plants of Kyrylivka Park (Dnipro, Ukraine) in areas with a strong, moderate and non-existent level of recreational load was studied. Floristic methods (estimates of species richness, determination of floristic community and homogeneity), methods of ecological analysis of vegetation, physico-chemical methods of soil analysis, statistical methods are applied. It was established for the first time that in Kyrylivka Park, artificial stands are capable of forming a sufficient amount of viable undergrowth of autochthonous (53,5%) and introduced (46,5%) species. The amount of tree growth of adventitious plants in the areas according to the level of recreational load is distributed as follows: with no load – 32,2% of the number of self-regenerating trees, with moderate – 41,3%, with strong – 89,7%. The indices of species richness of Margalef and Menkhinik of self-regenerating tree species for the site with a strong recreational load turned out to be the largest (at the expense of adventitious species) compared to the sites with a moderate recreational load and without it. The calculated Koch index of biotic dispersion (40.0%) indicates a certain process of floristic homogenization of the tree stand in the investigated territory of the park. The correlation coefficients between the number of self-restored allochthonous and autochthonous tree species for the studied areas with strong, moderate and absent recreational loads are significant (0.90, 0.92 and 0.88 respectively). The need to analyze and forecast the possible remote consequences of the introduction of alien species in the composition of the dendroflora is emphasized.

Floristic structuring of woody plants from the Chaco in light of abiotic factors

Abstract The phytogeographic domains are structured by different geoclimatic (abiotic) factors, such as altitude, temperature and precipitation. Thus, our goal was to investigate the possible abiotic factors that are related to the floristic richness of the tree-shrub component throughout the Chaco remnants. This study is based on data of the presence and absence of species in different remnants related to geoclimatic data. In addition, World Wildlife Fund shapes were used to differentiate dry and wet Chaco. The database aggregated 36 areas and 522 species. The different clusters obtained by floristic affinity between groups in Chaco was mainly related to temperature, altitude and seasonality of precipitation. In remnants where the seasonality of precipitation and altitude were more evident, there is greater dissimilarity in the composition of the tree-shrub vegetation. On the other hand, the temperature gradient explained the floristic homogeneity in the humid Chaco. Thus, the richness of the tree-shrub component of the Chaco is mainly attributed to three geoclimatic factors. Dry Chaco presents greater floristic dissimilarity compared to Humid Chaco. Still, the seasonality of the precipitation and the altitude play a dominant role in the structuring of trees and shrubs in the Dry Chaco and the temperature in the most homogeneous formations that integrate the humid Chaco.

The global loss of floristic uniqueness

Regional species assemblages have been shaped by colonization, speciation and extinction over millions of years. Humans have altered biogeography by introducing species to new ranges. However, an analysis of how strongly naturalized plant species (i.e. alien plants that have established self-sustaining populations) affect the taxonomic and phylogenetic uniqueness of regional floras globally is still missing. Here, we present such an analysis with data from native and naturalized alien floras in 658 regions around the world. We find strong taxonomic and phylogenetic floristic homogenization overall, and that the natural decline in floristic similarity with increasing geographic distance is weakened by naturalized species. Floristic homogenization increases with climatic similarity, which emphasizes the importance of climate matching in plant naturalization. Moreover, floristic homogenization is greater between regions with current or past administrative relationships, indicating that being part of the same country as well as historical colonial ties facilitate floristic exchange, most likely due to more intensive trade and transport between such regions. Our findings show that naturalization of alien plants threatens taxonomic and phylogenetic uniqueness of regional floras globally. Unless more effective biosecurity measures are implemented, it is likely that with ongoing globalization, even the most distant regions will lose their floristic uniqueness.

Little trace of floristic homogenization in peri‐urban Andean secondary forests despite high anthropogenic transformation

Abstract Pervasive human impact in heavily transformed landscapes may lead disturbance‐adapted species to thrive, resulting in floristic homogenization across forest stands. However, environmental heterogeneity and dispersal limitation may be antagonistic forces to homogenization, maintaining inherent floristic differentiation across sites. We evaluated the extent to which peri‐urban Andean forests are undergoing floristic homogenization in both late‐ and early‐successional stands. We considered seedling assemblages as well, as they provide key insights into forests’ future. We then quantified the relative importance of dispersal limitation and environmental filtering in determining the observed patterns of floristic similarity across the landscape. We used tree, seedling, soil and climatic data from six sites located in the high plain where Bogotá lies (Colombia). Within each site, we established six 20 × 20 m plots, three in early‐successional stands and three in late‐successional stands, for a total of 36 plots. To evaluate the extent of floristic homogenization, we defined tree floristic similarity among late‐successional stands as a baseline, reflecting our best‐guess of the original species composition that would have once occurred previous to intense anthropogenic intervention. Tree floristic turnover across the landscape was alike in late‐ and in early‐secondary stands, a finding that does not support the homogenization scenario. Seedling species composition, in contrast, was more homogeneous among early‐ than among late‐secondary stands, an outcome suggestive of homogenization. The relative importance of spatial and environmental drivers shifted between life stages. Distance between plots was the best predictor of tree species dissimilarity (29% of variance explained), whereas seedling compositional variation was more sensitive to changes in environmental conditions (41% of the variance explained). Relative humidity and several variables related to soil fertility showed a significant effect on floristic dissimilarity across the landscape, although significant factors were often different between life stages. Synthesis. Despite high anthropogenic transformation, we found little trace of floristic homogenization in these peri‐urban landscapes. Inherent floristic differentiation, promoted both by dispersal limitation and environmental heterogeneity, suggests that all patches are important to the conservation in these Andean forests, critical centres of endemism.

Effect of Anthropogenic Disturbance on Floristic Homogenization in the Floodplain Landscape: Insights from the Taxonomic and Functional Perspectives

Anthropogenic disturbances pose significant threats to biodiversity. However, limited information has been acquired regarding the degree of impact human disturbance has on the β-diversity of plant assemblages, especially in threatened ecosystems (e.g., floodplains). In the present study, the effects of anthropogenic disturbance on plant communities of floodplain areas (the Miya River, Mie Prefecture, Japan) were analyzed. The taxonomic and functional β-diversity among different degradation levels were compared, and the differences were assessed by tests for homogeneity in multivariate dispersions. In addition, the effects of non-native species and environmental factors on β-diversity were analyzed. As revealed from the results, anthropogenic disturbance led to taxonomic homogenization at a regional scale. The increase in non-native invasions tended to improve homogenization, whereas at a low degradation level, the occurrence of non-natives species was usually related to taxonomic differentiation. Furthermore, though the increase in non-natives and environmental parameters significantly affected the β-diversity of the floodplain area, environmental factors may be of more crucial importance than biotic interactions in shaping species assemblages in this study. The previously mentioned result is likely to be dependent on the research scale and the extent to which floodplains are disturbed. Given the significant importance of floodplains, the significance of looking at floodplains in the different levels of degradation was highlighted, and both invasion of non-native species and environmental factors should be considered to gain insights into the response of ecosystems to anthropogenic disturbance. The findings of this study suggested that conservation programs in floodplain areas should place more emphasis on the preservation of natural processes and forest resources.

Co-existence between humans and nature: Heritage trees in China’s yangtze River region

The negative consequences of increased urbanization on native biological and cultural diversity have received considerable research attention. Biological and cultural diversity can be sustained by counteracting various processes of floristic homogenization and by reestablishing connections between humans and nature. However, effective instruments to help people reconnect with nature can be lacking, especially in cities. Green spaces provide cultural, aesthetic, and ecological services and can represent a critical component of native plant diversity in urban environments. We examined the species composition of heritage trees and the tangible and cultural values of these trees in 11 major cities in the Yangtze River basin of China. Our analysis explored the similarities of three arboreal types, namely heritage trees, urban greening components, and natural plant communities. Heritage tree species are diverse, containing 310 recorded species representing 159 genera and 64 families. Their tangible and cultural values are mainly medicinal (221 species), followed by timber (186), culture (134), traditional courtyard planting (131) and food (124). Notable geographical differences in heritage tree species composition identified in our analysis could be explained by cities adopting mostly species native to the locality or province. Heritage tree assemblages were similar in composition to undisturbed natural plant communities, and the two populations experienced comparable progressive decline with geographical distance. Urban greening components indicated negligible decline in similarity beyond the 1000 km threshold, indicating common sharing of exotic species across disparate locations. Heritage tree species associated with notable tangible and cultural values, superior genetic constitution, and adaptation to local growth conditions present suitable candidates for urban planting to improve tree performance and urban biodiversity. Their long history of association with local culture and rich cultural values can be enlisted to strengthen the connections of urban communities to nature and history, and to promote nature conservation within cities. Given increasing biological and biocultural homogenization, especially in urban areas, protecting heritage trees and using them in urban greening can slow this trend and enrich stocks of urban biodiversity.

Plant Community Assembly in Invaded Recipient Californian Grasslands and Putative Donor Grasslands in Spain

The introduction of exotic species to new regions offers opportunities to test fundamental questions in ecology, such as the context-dependency of community structure and assembly. Annual grasslands provide a model system of a major unidirectional introduction of plant species from Europe to North America. We compared the community structure of grasslands in two Mediterranean regions by surveying plots in Spain and in California with similar environmental and management conditions. All species found in Spanish grasslands were native to Spain, and over half of them (74 of 139 species) are known to have colonized California. In contrast, in California, over half of the species (52 of 95 species) were exotic species, all of them native to Spain. Nineteen species were found in multiple plots in both regions (i.e., shared species). The abundance of shared species in California was either similar to (13 species) or greater than (6 species) in Spain. In California, plants considered pests were more likely than non-pest species to have higher abundance. Co-occurring shared species tended to maintain their relative abundance in native and introduced communities, which indicates that pools of exotic species might assemble similarly at home and away. These findings provide interesting insights into community assembly in novel ecosystems. They also highlight an example of startling global and local floristic homogenization.