High species mobility in species-rich plant communities: An intercontinental comparison

Patterns in ground beetle (Coleoptera: Carabidae) assemblages along an urbanisation gradient in Denmark

Plant-diversity hotspots on a global scale are well established, but smaller local hotspots within these must be identified for effective conservation of plants at the global and local scales. We used the distributions of endemic and endemic-threatened species of Myrtaceae to indicate areas of plant diversity and conservation importance within the Atlantic coastal forests (Mata Atlântica) of Brazil. We applied 3 simple, inexpensive geographic information system (GIS) techniques to a herbarium specimen database: predictive species-distribution modeling (Maxent); complementarity analysis (DIVA-GIS); and mapping of herbarium specimen collection locations. We also considered collecting intensity, which is an inherent limitation of use of natural history records for biodiversity studies. Two separate areas of endemism were evident: the Serra do Mar mountain range from Paraná to Rio de Janeiro and the coastal forests of northern Espírito Santo and southern Bahia. We identified 12 areas of approximately 35 km(2) each as priority areas for conservation. These areas had the highest species richness and were highly threatened by urban and agricultural expansion. Observed species occurrences, species occurrences predicted from the model, and results of our complementarity analysis were congruent in identifying those areas with the most endemic species. These areas were then prioritized for conservation importance by comparing ecological data for each.

A probability distribution model of small -scale species richness in plant communities

The research aimed to assess changes in segetal flora richness and biodiversity in cereal crops in a selected habitat (Małopolska voivodship; southern Poland) from 1993 to 2022. The research material consisted of 65 phytosociological relevés representing selected years of the analyzed multiannual period. The total species richness and the average number of segetal species on individual fields slightly decreased. In the first year of the study (1993), the total number of species was 56, and the average number of species in the phytosociological relevé was 23. However, in the last year (2022), the total number of species was 55, while their average number was around 20. The proportion of monocotyledonous weeds in the total weed infestation constantly increased, from 10% in 1993 to 23% in 2022. The studied flora was dominated by short-lived species (especially therophytes) throughout the entire multiannual period. The Shannon-Wiener diversity index remained at a relatively similar level for many years – in 1993 it was 0.8, and in 2022 – it was 0.9, which generally indicates a constant diversity of the studied flora of fields. The Simpson dominance index showed a decreasing trend; in the first year of the study it was 0.4, and in the last year – less than 0.3.

通过在荒漠草原开展增水和增氮野外控制试验，研究增水和增氮对荒漠草原植物群落结构、物种多样性及群落稳定性的影响。结果表明：（1）增水和增氮处理显著影响了荒漠草原植物群落结构和地上生物量，而对植物群落稳定性影响不显著（P>0.05）。增水处理显著增加了豆科和禾本科植物地上生物量（101.3%和57.9%）（P<0.05）；增水+增氮处理显著增加了植物群落盖度（43.2%）和地上生物量（112.4%）及不同功能群（禾本科和杂类草）植物盖度（75.5%和47.3%）和地上生物量（139.3%和85.7%）（P<0.05）。与增氮处理相比，增水+增氮处理显著增加了植物群落和不同功能群（禾本科和杂类草）植物高度、盖度和地上生物量（P<0.05）。（2）增水、增氮和增水+增氮处理均显著降低了植物群落Pielou指数（11.7%、8.7%和10.2%）（P<0.05）。（3）增水和增水+增氮处理提高了荒漠草原植物群落稳定性，而增氮处理降低了荒漠草原植物群落稳定性。增水处理荒漠草原植物群落稳定性效应大于增水+增氮处理。研究表明，荒漠草原植物群落结构受到氮沉降和降水增加的共同影响。增加降水对荒漠草原植物群落稳定性的积极效应可能会抵消部分氮沉降的消极影响，荒漠草原植物群落地上生物量及群落稳定性可能有所增加。;Desert grassland is predicted to be responsive to global climate change, such as increased atmospheric nitrogen deposition and precipitation. The structure, function and stability of plant community in desert grassland are often directly and indirectly affected by increased nitrogen deposition and precipitation. However, the response mechanism of plant community structure and stability in desert grassland to increase nitrogen deposition and precipitation are still not clear. We conducted the field experiments with water and nitrogen addition in desert grassland of Ningxia, China. We assessed the effects of increased atmospheric nitrogen deposition and precipitation on the plant community structure, species diversity and the plant community stability. The field experiment was conducted with four treatments, including control (CK), water addition (W), nitrogen addition (N), and water addition+nitrogen addition (W+N). We found that: (1) the plant community structure and aboveground biomass were effected significantly by water and nitrogen addition in desert grassland, but the plant community stability were not changed significantly(P>0.05). The plant aboveground biomass of Leguminosae and Gramineae were increased significantly by water addition (101.3% and 57.9%)(P<0.05). The coverage and aboveground biomass of plant community were significantly increased by 43.2% and 112.4% under water and nitrogen addition together, respectively. Water and nitrogen addition together also significantly increased the coverage (75.5% and 47.3%) and aboveground biomass (139.3% and 85.7%) of Leguminosae and Gramineae(P<0.05). Compared with nitrogen addition, water and nitrogen addition together significantly increased the height, coverage, aboveground biomass of plant community and different functional groups (Leguminosae and Gramineae)(P<0.05). (2) The Pielou index of plant community was decreased significantly by water addition, nitrogen addition, water and nitrogen addition together (11.7%, 8.7% and 10.2%)(P<0.05). (3) Plant community stability was improved by water addition, water and nitrogen addition together in desert grassland, while reduced by nitrogen addition. The effect of plant community stability by water addition was better than that of water and nitrogen addition together. The results indicated that the plant community structure would be affected by nitrogen deposition and precipitation increment in desert grassland. The positive effects of the increased precipitation on plant community stability in desert grassland may potentially offset negative effects of nitrogen deposition. Increased precipitation might lead to the increase of plant community aboveground biomass and plant community stability in desert grassland.

Grazing by large ungulates often increases plant species richness in grasslands of moderate to high productivity. In a mesic North American grassland with and without the presence of bison ( Bos bison), a native ungulate grazer, three non-exclusive hypotheses for increased plant species richness in grazed grasslands were evaluated: (1) bison grazing enhances levels of resource (light and N) availability, enabling species that depend on higher resource availability to co-occur; (2) spatial heterogeneity in resource availability is enhanced by bison, enabling coexistence of a greater number of plant species; (3) increased species turnover (i.e. increased species colonization and establishment) in grazed grassland is associated with enhanced plant species richness. We measured availability and spatial heterogeneity in light, water and N, and calculated species turnover from long-term data in grazed and ungrazed sites in a North American tallgrass prairie. Both regression and path analyses were performed to evaluate the potential of the three hypothesized mechanisms to explain observed patterns of plant species richness under field conditions. Experimental grazing by bison increased plant species richness by 25% over an 8-year period. Neither heterogeneity nor absolute levels of soil water or available N were related to patterns of species richness in grazed and ungrazed sites. However, high spatial heterogeneity in light and higher rates of species turnover were both strongly related to increases in plant species richness in grazed areas. This suggests that creation of a mosaic of patches with high and low biomass (the primary determinant of light availability in mesic grasslands) and promotion of a dynamic species pool are the most important mechanisms by which grazers affect species richness in high productivity grasslands.

Question:How does fire influence species richness and diversity in subtropical grassland in southern Brazil?Location:Recurrently burned grassland in Porto Alegre, Brazil (30°03′S, 51°07’W; max. altitude 311 m a.s.l.) and abandoned grassland near São Francisco de Paula, Brazil (29°47′S, 50°22’W; ca. 900 m a.s.l.).Methods:In the burned grassland, between‐year changes in community composition and single‐plot diversity, species number and vegetation structure were analysed in two consecutive years for plots with different time since last fire. Responses to fire of individual species were analysed. At the abandoned site, diversity, species number and vegetation structure were examined.Results:Species number and small‐scale species turnover were highest ca. one year after the burn, and decreased as caespitose grasses increased in cover with time since fire until reaching a stable, but less diverse state three to four years after a fire. The abandoned grassland showed higher dominance of caespitose grasses and lower richness and diversity.Conclusions:Fire clearly leads to a short‐term increase in species richness and diversity at the plot scale, as competitive interactions are being reduced and recruitment possibilities are high in early post‐fire vegetation development. Overall community composition does not change after a fire. While small herbs seem to be slightly favoured in the early post‐fire environment, no clear group of fire following species (absent in vegetation unburned for longer) was observed. The results indicate that the community is adapted to the current fire regime and is being maintained under the influence of fire.

There is a growing concern that land use intensification is having negative effects on semi-natural grasslands and that it leads to a general loss of biodiversity among all types of formerly extensively managed grasslands of poor to medium nutrient richness. Since the 1950s, many Central European uplands have been subject to an increase in grassland cover as a result of changes in land use practices. Using such a landscape in Lower Saxony, Germany, as a model region, we assessed environmental factors that control grassland diversity, including plant community composition, species richness and pollination trait composition. In 2007, 189 vegetation sampling sites were randomly distributed among grasslands covering some 394ha within a 2500ha study area. Plant communities were classified using TWINSPAN and the effects of environmental factors (soil, topography, current management and habitat continuity) were analysed by canonical correspondence analysis and regression analysis reducing for the effects of spatial autocorrelation by using principal coordinates of neighbour matrices.We found a wide range of six species-poor (<15 plant spp.) to extremely species-rich (>27 spp.) grassland types under mesic to dry site conditions, including sown, Cynosurion, Arrhenatherion and semi-natural grasslands. Grassland community composition was best explained by soil factors and species richness and pollination type composition by combined effects of current management and habitat continuity. During the 1950/60s, the extent of grassland area within the studied landscape rapidly increased to more than double its previous extent, and in 2007, grasslands comprised 16%. Natura 2000 grassland types comprised 1% of the surveyed site and medium-rich, high-nature-value grasslands a further 5%. While the number of wind-pollinated plant species was equal among all grassland types, there was a parallel decline in insect-pollinated plants and overall median species richness in the grassland communities along a gradient of increasing land use intensity (mowing, nutrient supply). Moreover, insect-pollinated plants occurring in intensively managed grasslands were found to additionally have the ability for self-pollination. Species-rich grasslands – including semi-natural grasslands and a semi-improved, species-rich Arrhenatherion community – occurred exclusively on old sites (with >100 years of habitat continuity) that had been used for traditional sheep grazing (environmental contracting). Medium-rich Arrhenatherion grasslands were established primarily on less productive, formerly arable fields (<30 years). We conclude that conservation efforts should focus on extant species-rich grassland types and should aim to implement traditional land use practices such as sheep grazing. Additional restoration efforts should focus on establishing new grasslands on less productive sites in the proximate surroundings of species-rich grasslands to facilitate seed dispersal, but nitrogen deposition should be buffered where appropriate. These measures would enhance the interaction between nature reserves and agricultural grasslands and thus improve the ecological quality of grasslands at the landscape scale.

Recent theoretical developments involving community assembly on the one hand, and invasion biology on the other, suggest a gradual convergence in thought between what have been two largely separate theoretical initiatives. The term "invasibility" emerged in the field of invasion ecology to describe the susceptibility of environments to invasion by species from other regions of the world. Although Elton did not use the term "invasibility" in his pioneering book (1958), he did employ the concept, referring to an ecosystem's "vulnerability to invasion". Given its original definition, the concept of invasibility has been limited in its scope and use, with rather little application to the larger field of community ecology. However, our assessment and usage of the concept (Davis et al. 2000, 2001) has prompted us to consider invasibility as a more general condition of all environments. This expanded perspective of invasibility has caused us to reconsider some fundamental questions and issues regarding community assembly and species diversity as well as recent discussions involving the notion of metacommunities (Leibold and Miller 2004, Leibold et al. 2004). By metacommunity, we mean a set of local communities that are linked by dispersal of multiple, and potentially interacting, species (Leibold et al. 2004). Recent theoretical efforts to characterize community assembly processes have reemphasized understanding the importance of interactions between local and regional processes (Levine 2000, Hubbell 2001, Tilman 2004, Foster and Dickson 2004, Jiang and Morin 2004, Steiner and Leibold 2004, Leibold et al. 2004). There is general agreement that the diversity of the regional species pool and the extent of dispersal of the species from this pool throughout the region are the principal regional processes involved. However, investigators have emphasized the importance of different local conditions and processes, including productivity (Jiang and Morin 2004, Steiner and Leibold 2004), demographic stochasticity (Tilman 2004), ecosystem size (Fukami 2004), biotic limitation of diversity (Tilman 2004), and even extent of tree lean, the latter which affects colonization success of epiphyes (Snäll et al. 2005). We propose that the notion of invasibility can serve as a unifying concept in these discussions and thereby can facilitate current efforts to develop a more comprehensive and realistic theory of community assembly and metacommunity dynamics. We define "invasibility" as the susceptibility of an environment to the colonization and establishment of individuals from species not currently part of the resident community. By establishment, we mean that the persistence of colonizing individuals is due primarily to their ability to sustain themselves by accessing resources in their new environment, e.g. as opposed to surviving on resources imported from their original environment. Although a new species often subsequently spreads throughout its new environment, we believe that colonization and establishment are sufficient criteria to define invasibility, since a species can persist at a site indefinitely without spread, or even recruitment from reproduction, as long as individual colonizers are able to establish and persist long enough for other colonists to replace them before they die. Although practical obstacles will often make it difficult to measure invasibility, conceptually, the quantification of invasibility is straightforward. For example, invasibility can be quantified as the probability of establishment per arriving propagule (Davis et al. 2000). (Formally, invasibility describes only a community's potential for being colonized. Whether that potential is realized is dependent on the presence and abundance of propagules.) Ultimately, a community's invasibility varies not only in time, but from species to species (and even from genotype to genotype within a species). At a particular moment in time, a community might be readily invasible to one species but not to another. Hypothetical changes in invasibility (I) of an environment over time to a particular species (a). Maximum invasibility (1.0) occurs when every arriving propagule successfully establishes. Since establishment success of arriving propagules is normally very low, the magnitude of the invasibility path shown for the hypothetical species has been exaggerated for illustrative purposes. The invasibility at a particular point (x) during the time period is indicated with an arrow. The invasibility of the environment to this species (Ia) over the time period shown (0–t) can be quantified as: . Whether or not a species is a long-term resident in the region or has been recently introduced to the regional species pool, the ability of colonizers to become established in a new community depends on the existence of available resources (Davis et al. 2000) and other site attributes of the new environment, such as the presence or absence of particular predators and pathogens (Shea and Chesson 2002) and the extent to which the physical conditions of the original environment match those of the new environment (Kolar and Lodge 2002). Community invasibility, then, is a general phenomenon, applying to all species and all communities, and represents a composite of local processes affecting community assembly. A central controversy in community ecology for the past forty years has been whether communities are mostly saturated with species or whether local community diversity is limited primarily by the richness of the regional propagule pool (MacArthur 1965, Ricklefs 1987, Cornell and Lawton 1992, Lawton 1999). This debate, like so many in ecology, can be traced back to Darwin (1859), who believed that competition limited diversity and that the earth was largely saturated with species: "The extinction of old forms is almost the inevitable consequence of the production of new forms." (Darwin 1859). The debate over the relative importance of local or regional processes in community assembly intersects with the diversity-invasibility controversy. The diversity-invasibility hypothesis, first proposed by Charles Elton (1958), holds that most available niches will already be occupied in species-rich communities and that thus these communities will be more resistant to invasion than species-poor communities, which are believed to contain more unoccupied niches. Many ecologists since have agreed with Elton (e.g. Tilman 1999, Knops et al. 1999, Naeem et al. 2000) while others have suggested that species rich communities sometimes may actually be more invasible (Lonsdale 1999, Stohlgren et al. 1999). Recent assessments have emphasized the role that spatial scale likely plays in the diversity-invasibility relationship (Levine 2000, Tilman 2004, Jiang and Morin 2004, Steiner and Leibold 2004), while others have questioned whether the relationship exists at all, other than as a statistical artefact (Fridley et al. 2004, Herben et al. 2004). Although we have participated in the diversity-invasibility debate (Davis et al. 2000, 2001), we now believe that the debate has been misdirected since Elton first proposed the diversity-invasibility hypothesis. The original, and hitherto uncontested, assumption of the diversity-invasibility hypothesis is that diversity (D) is the independent variable and invasibility (I) is the dependent variable. Thus, for more than forty years, ecologists have been debating the equation I=f(D). However, perhaps all along we should have been debating D=f(I). We believe that invasibility, not diversity, is the more fundamental essence of a community, and that diversity does not give rise to invasibility, but rather emerges from it. In other words, we believe that invasibility, a condition that represents the integration of many local processes, is one of the two major drivers of diversity at the local level, the other being regional processes involving dispersal from the regional species pool (Fig. 2). The proposed dispersal-invasibility model of metacommunity dynamics, showing that local patterns of diversity result from the interacting dual effects of invasibility, an attribute of a local environment or community, and the diversity of, and dispersal from, the regional species pool. The diagram shows that invasibility of community A (INVA) is a composite attribute, influenced by both physical and biological conditions, events, and processes operating at the local scale. Invasibility of communities is expected to vary over time due to changes in the local conditions, events and processes that, together, define invasibility. The regional species pool represents the species richness of the metacommunity and is made up of all the species residing throughout all the individual communities. As described in the text, in some circumstances, local invasibility can have a feedback effect on the richness of the regional species pool (feedback indicated by the dashed arrows between individual communities and the regional species pool). With this shift in perspective, invasibility is seen as a dynamic property of communities that is more fundamental than species diversity because it precedes species diversity. Invasibility exists and can be measured (at least theoretically) even in completely unpopulated environments. Although there would be no competition for resources from resident species in such cases (since no species are present), invasibility still exists as a measurable attribute of the environment, and would be affected by the absolute levels of resources present in the environment and by the extent to which the physical environment, including the disturbance regime, compromises the colonists' ability to access those resources (Fig. 2). Thus, invasibility is not a peripheral feature of a community relevant only to a particular subset of species and ecological processes, but describes a general and fundamental condition of all environments. As shown in Fig. 2, the invasibility of an environment is influenced by the interaction of biological and physical processes operating at the local scale. Physical conditions include basic life constraints, such as temperature, water availability (for terrestrial organisms), O2 or CO2 levels (for aquatic organisms), and presence or absence of a necessary substrate, e.g. soil, rocky crevices, etc. Food web interactions, both within and between trophic levels, can either increase or decrease the invasibility of an environment for a particular species, or group of similar species, depending on the nature of the interactions. Facilitative effects of species often involve modifying physical conditions, events, and/or processes, such as increasing gross resource levels (e.g. legumes), ameliorating harsh physical conditions (e.g. nurse plants), and introducing disturbances (e.g. burrowing animals), but they also may provide benefits such as pollination and increased ability to access resources (e.g. mychorrizal fungi). While each of the individual physical and biological processes plays a role, ultimately it is the integrated sum of the processes, the environment's invasibility, that is the local driver of diversity. The primary effect of an environment's invasibility on local diversity is as a filter of incoming propagules. A more invasible environment means that more of the dispersing propagules will be able to become established, thereby increasing diversity whenever the newly established propagules represent a new species. If invasibility represents the accessibility of an environment to all prospective colonizers, then species-rich communities must be, or have been in the past, quite invasible, at least periodically. Unless a community's high diversity is due primarily to in situ speciation, colonization by new species must have been a common occurrence at some point in its history. Logically, it cannot be any other way. The highly invasible nature of species-rich grasslands is not a new discovery, but has been known for some time. Grubb (1976) noted that much of the diversity of species-rich limestone grasslands consisted of annuals, biennials and short-lived perennials that only persisted in the system by continual regeneration from seed. Van der Maarel and Sykes (1993) pointed out that high rates of turnover of species and individuals were typical of limestone grasslands in Sweden. Later, they showed that this was also true for species-rich grasslands on other continents (Sykes et al. 1994). Stampfli and Zeiter (2004) found similar high turnover and rates in their study of a species-rich semi-natural meadow in Switzerland. Further evidence that species-rich limestone grasslands are not strongly structured by interspecific competition are findings that most species appear to be distributed at random relative to each other (Pearce 1987, Mahdi and Law 1987, Mahdi et al. 1989, Campbell et al. 1991). We agree with Leibold et al. (2004) that invasibility at the local level can generate some feedback to the species pool at the regional scale (Fig. 2), although we believe this feedback is likely quite small, at least for metacommunities consisting of a large number of local communities, for the following reasons. An environment with low invasibility will support a community comparatively low in species richness, meaning that species not residing in this community must reside in other local communities in order to remain a part of the regional species pool. Thus, environments with low invasibility are supporting a smaller proportion of the regional species pool than highly invasible, and hence more species-rich, environments. As long as there are many species-rich environments, it is unlikely that one, or a few, low-invasibility environments will reduce the regional species pool. However, as the proportion of low-invasibility environments increases, colonization events throughout the metacommunity will not be able to keep pace with local extinction rates of some species, resulting in the regional extinction of some species, and hence a decline in the richness of the regional species pool. Lawton (1999) described a one-dimensional continuum of communities, ranging from what he referred to as Type I communities, the diversity of which seemed to be determined primarily by regional processes, e.g. diversity of the regional propagule pool, to Type II communities, which seemed to be governed more by local processes, e.g. species interactions and habitat suitability. The perspective we are presenting allows us to consider invasibility (local processes) and diversity of the regional species pool (regional processes) as two largely independent variables that can be presented orthogonally to construct a simple two-dimensional graphical representation (Fig. 3) of the dispersal-invasibility model of metacommunity dynamics presented in Fig. 2. In this visual framework, differences in local diversity are seen to arise from differences in the richness of regional species pools and the invasibility of the respective local environments. For example, Region A (Fig. 3) characterizes environments with high invasibility that encounter rich regional species pools. Examples of this environment type are tropical rain forests and coral reefs. Both environments experience periodic disturbances that facilitate the introduction of new species and the persistence of resident species (Sale 1977, Connell 1978, Hubbell 2001), and the species diversity of the regional species pool is very high in both cases. Distribution of different community types and environments shown as a function of local invasibility and the regional species pool using a graphical representation of the diversity-invasibility model presented in Fig. 2. Region B (Fig. 3) characterizes environments with high invasibility, but diversity is limited by a comparatively poor regional species pool. Temperate environments and many islands represent this region type. For example, temperate forests also experience frequent disturbances, including fire, wind, and insect outbreaks, however the diversity of these environments is limited by the comparatively small number of tree species in the temperate regional pool. Whatever the ultimate cause(s) for regional differences in the diversity of species pools, the simple graphical representation of the proposed dispersal-invasibility model shows that diversity differences among similar environments from different regions of the world should be due primarily to differences in the richness of the respective regional species pools. Assuming similar environments in a single region encounter a similar species pool, differences in diversity among similar environments within a single region should be due primarily to differences in invasibility of the environments. Diversity can be suppressed by low levels of invasibility in the face of adequate, or even rich, species pools (Region C in Fig. 3) in several ways. Abundant resources may be available at a site in an absolute sense, but completely, or nearly completely, already sequestered by the residents. For example, over-harvesting of herbivorous reef fish has eliminated, or sharply reduced the extent of, grazing by fish in many reef ecosystems throughout the world, and is believed to have contributed to the recent domination of algae in these reefs (Stimson et al. 1996, McClannahan 1997). Even though these reefs most likely still encounter propagule pools rich in coral species due to the pelagic dispersal patterns of coral larvae (Karlson and Cornell 2002), the algal dominated reefs have become quite resistant to coral colonization since the algae have coopted virtually all available space, the key limiting resource in these environments. A terrestrial example of Region C (Fig. 3) is the species-rich limestone grasslands of northern Europe, the diversity of which can be drastically reduced by the invasion of the rhizomatous grass Brachypodiumpinnatum (Bobbink and Willems 1987, 1991, Hurst and John 1999). Even small patches of Brachypodium are markedly less diverse despite exposure to a diverse seed rain from surrounding species-rich grassland. Another way that diversity can be suppressed by low levels of invasibility even in the face of rich propagule pools (Region C, Fig. 3) is if a site is resource-poor in absolute terms. In such cases, even if few resources are sequestered by residents, and hence most are available to colonizers, the amount of available resources is still insufficient to support most new colonizers. For example, even if many plant species dispersed to an environment with sterile soils (whether historically nutrient poor or impoverished due to human activity), few would encounter sufficient resources to permit the species to establish successfully. Very high disturbance rates can also lead to low levels of invasibility. Although high disturbance rates would presumably free up considerable resources for both colonizers and residents, relatively few species would be sufficiently disturbance-tolerant to be able to colonize and persist in these environments and thereby take advantage of the abundant resources available. Annually cultivated agricultural lands are an example of this. The most species-poor communities are communities characterized by low levels of invasibility located in regions with poor regional species pools (Region D, Fig. 3). Examples of such environments are high-latitude sites in which successful colonization and persistence is limited by the harsh physical conditions and often low absolute levels of resources, and which encounter depauperate species pools. Remote rocky islands are another example of Region D communities, their limited regional species pools a product of their remoteness, and the low invasibility limited by the low absolute levels of resources. Several recent theoretical studies of community assembly have investigated some of the issues we have presented here. Tilman (2004) proposed an elaboration of classical competition theory, which he termed "stochastic niche theory", in which he emphasized the importance of the stochasticity of colonization and the interaction between the independent processes of "recruitment limitation" and "biotic limitation of diversity" in explaining patterns of invasion and community assembly. Like us, Tilman emphasized the essential interaction of regional and local processes in determining local patterns of diversity. However, his stochastic niche theory is still based in the traditional approach that conceives invasibility as the dependent variable, with diversity affecting invasibility via competition. Steiner and Leibold (2004) presented a theoretical model designed to provide insights as to why productivity-diversity relationships are usually unimodal at the local scale but monotonically increasing at larger spatial scales. Their model showed that high productivity should result in both high invasibility and high species turnover at the local level, which when combined with stochastic dispersal processes, would tend to produce different species compositions among different communities, resulting in high beta diversity, and the resulting montotonic increase of diversity with increasing spatial scale. Jiang and Morin (2004) created a productivity gradient in aquatic mesocosms stocked and invaded with different species of microbes that provided support for the that in productivity can produce the relationship between diversity and invasibility that is so often at larger scales. Steiner and model and Jiang and on a we believe is often with the invasibility of a site (Davis et al. 2000). Steiner and model and Jiang and findings represent a of the more general of local invasibility we are presenting that of invasibility being a composite (and attribute of an environment, which is with conditions, events, and processes in to Leibold et al. (2004) the new concept of metacommunity as a way to community ecology, the local patterns of community are affected by the larger regional species pools and local community processes may back and the larger scale regional In their Leibold et al. described that have both theoretical and on species and in whether or not individual communities vary in their attributes and to different species and whether or not the species involving dispersal and The model we are all of these For example, Fig. shows that communities not vary in their attributes and is the as the communities not vary in their invasibility. Although we that invasibility should be a of diversity, rather than a our model does for feedback of community on invasibility. The large and diverse that web effects can have on invasibility (Fig. means that invasibility can be affected by the presence or absence of particular species that have a such as habitat and competition. et al. to such species as However, of this feedback is not the as the notion of effects between invasibility and diversity. for very the only all may be in which diversity has sometimes been found to invasibility et al. 1999, Naeem et al. but et al. 2004, Herben et al. 2004), we believe the relationship between invasibility and diversity is and not D=f(I). is very that ecologists are able to describe basic processes to and the general We believe that the simple two-dimensional model we have proposed an to and the general on the processes that In we believe the model can be to the effects on local and regional patterns of diversity of both human and can be in of their effects on regional species pools and the invasibility of particular local communities. The only we might suggest for these discussions is a more term for perhaps or of the For example, while increasing the availability of often in the domination of a small number of species that reduce diversity by to reduce invasibility and 2004, et al. (Fig. nutrient e.g. poor and can many species from a site they and et al. and 1999, and also a in invasibility and diversity (Fig. that a community's disturbance can reduce community invasibility, and thereby its diversity, if disturbance rates or increase or decrease and resource availability (Fig. the other hand, some disturbances, such as the of can increase an environment's invasibility by an disturbance (Fig. in patterns of local diversity that can be expected to result from and other due to local changes in invasibility and regional changes in the diversity of the species pool. The magnitude of the effect of these changes on local patterns of diversity for a particular and even the of the diversity will be influenced by site conditions and the species as well as by the and extent of the and other The and of species by has increased the diversity of species pools in many regions of the world 2001, et al. which has in in the diversity of many local communities within those regions and et al. (Fig. The presence of new species in the regional pool and their colonization and establishment in individual communities can either increase or decrease the invasibility of those communities (Fig. in the way that the community's invasibility is increased or by the presence of species. For example, the new species may resources thereby invasibility and community diversity (Bobbink and Willems 1987, 1991, Hurst and John or the new species may harsh physical conditions, thereby the introduction other species, including species, resulting in an increase in the diversity of the local environment 2004, and 2005). Invasibility and regional species pools, and hence patterns of diversity, are also to changes in et al. 2004). in of of events, and other processes are likely to the of successful as patterns of resource availability and physical Thus, depending on the particular changes a community due to its invasibility may either increase or decrease (Fig. In any changes in the of would be expected to be by of species, thereby a community's regional species pool (Fig. In a some environments would be expected to experience an increase in their regional species pools, e.g. environments, species pools might be expected to decline in regions that become more The notion that ecological communities are via and that this dispersal species of the respective communities is not new (MacArthur and Ricklefs However, there is in our understanding of local and regional processes a more model of metacommunity dynamics (Leibold et al. 2004). at least different have been proposed dynamics, species and the model (Leibold et al. 2004). of these are highly for example, on such as are in all other than species of these represent first in a comprehensive theory of is now is a more comprehensive and one that would be able to the key and of and that would provide a much more realistic of metacommunity dynamics (Leibold et al. 2004). Recent theoretical developments involving community assembly on the one hand, and invasion biology on the other, suggest a gradual convergence in thought in what have been two largely separate theoretical initiatives. We the presented will this we believe that the concept of invasibility, with the dispersal-invasibility model (Fig. 2), that we have presented can serve as an in which to and the conditions, events, and processes that the patterns of diversity we within and between local communities in different regions throughout the world. In we believe that the simple graphical representation of the model (Fig. thought and among can be by ecologists to and the general of ecological processes that and the way in which human can these processes (Fig. in this were by by the and the

본 연구는 환경부의 '전국 무인도서 자연환경조사 보고서(1999년∼2001년)'에서 발췌한 261개의 무인 도서를 대상으로 섬의 지리적 환경과 섬에 분포하는 관속식물의 종수 및 분포사이의 상관성을 구명하고자 수행하였다. 261개 도서의 평균 면적은 75,000㎡이며, 면적의 분포범위는 최소 1,l00㎡에서 최대 961,200㎡였다. 육지와의 최단거리 평균은 14.9km(150m∼51.4km)이었다. 261개 도서에서 관찰된 전체 종수는 30과 1,109 종으로, 각 도서당 관찰된 종수의 평균은 98.7종이었다. 자생식물은 1,003종(90.4%)이었으며, 귀화식물은 106종(9.6%)로 조사되었다. 그리고 조사된 전체 종수 중에서 국화과가 114종으로 가장 많았으며, 벼과 (90종), 콩과(54종), 장미과(53종) 순으로 나타났다. 261개 섬은 출현한 식물종의 구성에 근거하여 다차원척도분석을 실시한 결과 '남해그룹(130개 섬)'과 '서해그룹(131개 섬)'의 두 지역으로 뚜렷이 구분할 수 있었다. 서해그룹에 속하는 섬들은 남해그룹의 섬들에 비해 면적이 더 넓었으나(서해그룹 평균=93,000㎡, 남해그룹 평균=57,000㎡), 도서당 출현 종수는 적었다(서해그룹 평균=192, 남해그룹 평균=233). 또한 서해그룹보다는 남해그룹에만 한정적으로 분포하는 종들이 두 그룹을 구분하는데 더욱 큰 영향을 미치는 것으로 나타나서, 위도에 따른 식물 분포를 반영하고 있다. 출현하는 식물 종수에 가장 큰 영향을 미치는 인자는 섬의 면적이었으며, 육지와의 최단거리와 인간의 간섭 인자 순으로 나타났다. 식물종수에 미치는 환경인자들은 서해그룹과 남해그룹에서 각기 다르게 나타났으며, 남해그룹의 섬들이 서해그룹의 섬들에 비하여 육지와의 거리가 가깝고 단위면적당 출현 종수가 많았기 때문에 보다 다양한 환경인자들에 의해 민감하게 영향을 받는 것으로 생각된다. 따라서 이상의 결과들은 무인도서 생태계 보존을 위해 중요하게 활용될 것으로 기대되며, 앞으로 인간간섭과 귀화식물종이 무인도서 생태계에 미치는 영향에 대한 연구가 계속적으로 이루어질 것이다. Correlations among the island area, distance to mainland, latitude, longitude, human impacts, diversity and composition of vascular plants were investigated by analyzing data on 261 islands(10.3% of total number of islands in Korea) selected from the annual reports for 'the natural evironment survey of the uninhabited islands in Korea' published by 'Ministry of Environment' during three years from 1999. The area of surveyed 261 islands ranged 1,100 to 961,000㎡(average of 75,000㎡), and the distance to mainland ranged 0.15 to 51.5km (average of 14.9km). Total number of plant species recorded in those islands was 1,109 species throughout 30 families, and mean mumber of plant species of each island was 98.7 species. Native species were 1,003 species (90.4%), and exotic species were 106 species(9.6%). The families with the largest number of species was the Compositae with 114 species, and followed in the order of Gramineae(90), Leguminosae(54), and Rosaceae(53). The result of multi-dimensional scaling analysis based on the plant species composition showed that 261 islands were distinctly divided into two groups, western sea group(131 islands) and southern sea group(130 islands). The islands of western sea group(average area of 93,000㎡) had greatly larger area than them of southern sea group(average area of 57,000㎡), but the average number of species (average species of 192) per island were less than in southern sea group (average species of 233). And, the partitioning into two groups was responsible for the species restricted to southern than to western sea group. Therefore, this results suggest that the distribution pattern and the composition of plant species could be also affected by the latitude of the island. When the species-area model was applied to total island and plant species, these results indicate that the island area was the most significant predictor of plant species diversity, and the distance to mainland and the human impacts were also shown to be significant predictors of plant species richness. But when applied to both groups of islands by the stepwise selection method, the result showed that islands of southern sea group were greatly affected by the factors such as human impacts, distance to mainland and longitude than western sea group. For the purpose of conservation of natural ecosystem on the uninhabited islands in Korea, we will also examine how the human impacts and the invasion of exotic plant species will disturb the native species diversity.

Changes in the environment induced by anthropogenic impact or natural stressors are subject to bioindication. Most often, the anthropogenic stressors are the main object of bioindication research. Hemeroby and naturalness are considered as indicators of the level of anthropogenic transformation of ecosystems. Hemeroby is frequently used to assess disturbances in different types of vegetation. However, this concept has rarely been used to assess the impact on animals. According to the method of indicator values, species richness of a community is a marker of bioindication potential. The article compares the patterns of response of species richness of soil macrofauna and herbaceous cover communities in a city park, taking into account gradients of environmental factors, naturalness, and hemeroby. Within the study area, test plots were located. Soil macrofauna samples were taken at 105 points in each of the test sites, and soil hardness, electrical conductivity and soil temperature, litter height, and grass cover height were also measured. A geobotanical description of the vegetation cover was made within each plot. In the survey plots, 7.6 ± 3.0 plant species were found in the herbaceous layer. In soil samples, 6.8 ± 2.9 species of macrofauna were found. With an increase in the number of plant species in the herbaceous layer, the number of soil macrofauna species showed a downward trend. An increase in the number of soil macrofauna species is accompanied by a decrease in both naturalness and hemeroby of the plant community. The naturalness index does not depend on the number of plant species, but the largest number of plant species was observed under conditions of naturalness level from 0 to 1. With an increase in hemeroby, the number of plant species increases, although this relationship also has a nonlinear component. The largest number of plant species is observed at hemeroby levels from 45 to 65. Environmental factors and indicators of hemeroby and naturalness were able to explain 27% of the variation in the number of soil macrofauna species. Humidity regime and continentality did not affect the number of species. Increased variability in moisture conditions, carbonate content, and indicators of frost and cryoclimate contributed to an increase in the number of invertebrate species. Increases in acidity, mineral salts, nitrates, and soil aeration had a negative impact on the number of soil macrofauna species. Soil properties were able to explain 21% of the variation in the number of soil macrofauna species. Environmental factors and indicators of hemeroby and naturalness were able to explain 72% of the variation in the number of herbaceous plant species. Increases in moisture, acidity, mineralization, thermocline, and cryoclimate indicators had a negative impact on the number of plant species. Biological indicators can be used to assess complex environmental factors that are difficult to measure using instrumental methods. Bioindicators are also used to assess the level of anthropogenic transformation of ecosystems. The key concepts for solving this problem are the naturalness and hemeroby of plant communities, which are used as markers of ecosystem disturbance in general. Vegetation cover as a source of bioindication information can provide a biased assessment of the level of anthropogenic transformation due to its greater sensitivity to certain types of anthropogenic pressure. The potential of soil animals as a source of information on the level of anthropogenic transformation in the urban environment is quite significant. Species richness is a marker of the potential ability of a plant or animal community to provide reliable bioindication information. The bioindication complementarity of animal and plant communities is that the highest species richness of soil macrofauna is observed at a relatively low level of species richness of plant communities. Therefore, soil macrofauna can complement and clarify estimates of the level of anthropogenic transformation made using plant communities or can be an independent source of information for such estimates.

The number of observed species is an index of the relative value of the site to be protected in relation to other sites. To date, most analyses pertaining to species richness have focused on breeding populations and sites. However, avian migratory bottlenecks are no less important for conservation and management purposes. Here we present an example with the use of bird ringing conducted at Eilat, Israel, between the years 1984-2000. We hypothesized that because Israel is located at the juncture of the three continents, we will have new species every year. During the 17 years, 139, 354 individuals of 268 species were ringed. The average of total birds ringed per year was 8197.3 and the average number of species was 113. Of 268 species ringed, 205 (76.5%) were passage migrants, 41 (15.3%) breeding species, and 22 (8.2%) were accidentals. We found a significantly positive correlation (r2=0.857, P=0.014) between the number of species caught each year and the number of operational net days. The number of species recorded annually correlated significantly with the number of individuals caught and the cumulative number of recorded species increased logarithmically throughout the study period. The greatest increase was recorded between the first and second years. Changes in the number of new species decreases non-significantly over the study period. Further, when the difference between the first and the second year is removed this relation is non-significant. It means that chances to catch new species for Eilat are always the same. In conclusion, a ringing station can expect to catch the largest proportion of species within the first three years of activity and then to catch two to three new species annually, i. e., at Eilat we should expect to catch 20 new species during the upcoming decade.

This chapter discusses the colonization and extinction events and species turnover. It shows how, in the face of ongoing colonization and extinction events, cumulative species numbers on islands increase while the number of residents at any one time remains nearly constant. The chapter also examines the parameters that affect species turnover and cumulative species counts. Species turnover can be measured within islands over time, and also between islands over space. The chapter also discusses the distance decay phenomenon, which means that nearby islands may share more plant species than islands which are far apart, and that species turnover may increase with the distance between the islands being compared.

Semi-natural, extensively managed grassland communities are among the most species-rich plant communities. The species number and floristic composition depend on numerous factors, both natural and associated with human activity, both present and past. In European countries, a system of subsidies for farmers is used to preserve extensive, usually unprofitable management of multi-species grassland communities. The development of specific recommendations requires knowledge of the main factors shaping grassland plant communities. A study was carried out in seven regions of the Polish Western Carpathians, in areas with traditional sheep grazing. Plant species composition (phytosociological relevés) of 517 plots were surveyed in different grassland types. For each plot, topographic parameters, i.e. slope, aspect and altitude, were recorded and land use in the past was read from historical maps. The aim of the study was to a) assess differences in the species composition of grassland vegetation between topographically and historically different regions of the Polish Carpathians, and b) to identify the main factors influencing species composition in each of these regions. Depending on the region, different factors contributed most to explaining the variation in the species composition and species numbers. Topographic factors played a decisive role. The type of past use (arable land or grassland) had little influence on current biodiversity. The results of the study indicate the need for a localised approach to developing principles for protection of grassland biodiversity.

The relationship was studied between shoot biomass, nutrient concentration in the soil and number of species per unit area. The study was carried out in two different parts of the Netherlands, the Gelderse Vallei (east of Amersfoort) and the Westbroekse Zodden (northwest of Utrecht). Four series of vegetation and soil samples were taken: one series in grassland and wetland communities, one series in grassland communities, one series in fen communities and one series in only one wetland community. The two series in grassland communities show a negative correlation between shoot biomass and species number and a positive correlation between shoot biomass and nutrient concentration in the soil. The opposite was found in the series in the fen communities: there was a positive correlation between species number and shoot biomass and a negative correlation between shoot biomass and nutrient concentrations. The series of samples that had been taken in only one wetland community showed an optimum curve for the relation between shoot biomass and number of species. It is concluded that in the plant communities studied the species richness per unit area increases with increasing productivity at low production levels ( 400–500 g/m2).