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During primary succession, the abundance of different species and their associated plant traits change over time. Understanding how plant traits linked to colonising and competitive abilities change through succession is important for determining whether community assembly can be predicted. Examining this across more than one taxon group can reveal if these patterns are generalisable.Here, we investigated primary succession on bare chalk for a chronosequence spanning 33 years for two different taxa, vascular plants and bryophytes. We examined how abundance changed through succession, and how this related to species' colonising and competitive abilities, using relevant plant traits for each taxa. A zero‐inflated beta regression model was used to investigate the effects of traits on both presence/absence and abundance‐when‐present of vascular plants and bryophytes.Vascular plants with a larger specific leaf area were more likely to occur later in succession. Vascular plants, which were hemicryptophytes, wind dispersing and had a lower canopy height, were more likely to increase in abundance‐when‐present during succession.Bryophytes with a larger spore diameter were more likely to occur later in succession. Shorter bryophytes with a greater frequency of sporophyte production had a higher abundance early in succession, representing their high colonising abilities. Whereas later in succession larger bryophytes, with a mat or weft life form and low sporophyte frequency were more abundant, indicating a shift towards greater competitive abilities.Synthesis. This study has revealed different patterns for vascular plants and bryophytes regarding colonisation and changes in abundance through succession, and the associated traits linked to colonising and competitive abilities. Although some traits were found to influence abundance through succession for vascular plants, these were often contrary to the expected pattern representing the change from colonising to competitive abilities, whereas for bryophytes, there was more evidence for this shift with successional age. This suggests that general theories on succession‐linked plant traits should not be relied upon in isolation for the prediction of community assembly. Context, particularly successional age in relation to the available species pool is also key. [ABSTRACT FROM AUTHOR]

Plant community succession is structured by initial richness, plant consumer pressure and soil resource supply. These drivers influence species' trait trade‐offs that underlie temporal changes in plant community diversity. Importantly, how these drivers interact with each other and through time and whether they act on different facets of plant community diversity by promoting different plant trade‐off strategies remains poorly understood.We experimentally manipulated initial plant richness, consumer pressure via pesticide spraying and soil resource supply via fertilization across 4 years of old field succession. We then allowed natural colonization and extinction to occur and examined how the three drivers influenced succession. Specifically, we examined changes in temporal dynamics by conducting yearly taxonomic cover surveys and measuring light penetration to the ground. In the third year, we measured vegetative height and specific leaf area (SLA), and investigated seed mass using a trait database.Higher initial richness, lower consumer pressure and increased soil resource supply all decreased colonizing species richness and light availability and variably altered species evenness. These effects generally acted additively rather than interactively in driving community diversity during succession. However, soil resource supply suppressed consumer pressure effects on species richness and light availability, while consumer pressure and soil resource supply modified initial richness effects on light availability. Treatments acted on different trait identities, revealing different mechanisms underlying taxonomic responses. Initial richness effects on seed mass of colonizing species were modified by soil resource supply. Decreased consumer pressure increased intraspecific community height and decreased interspecific SLA. Increased soil resource supply increased community height, SLA and seed mass.Synthesis. Our results suggest species' resource strategies underlie plant diversity responses to consumer pressure and soil resource supply. Resource addition promoted resource‐acquisitive species; consumer pressure disadvantaged resource‐conservative species. Meanwhile, initial richness altered subsequent community composition primarily through persistence of early residents. We show that community responses to drivers of succession depend on underlying trait trade‐offs of resident species, and these trade‐offs influence community diversity across succession. [ABSTRACT FROM AUTHOR]

Studies of succession have a long history in ecology, but rigorous tests of general, unifying principles are rare. One barrier to these tests of theory is the paucity of longitudinal studies that span the broad gradients of disturbance severity that characterize large, infrequent disturbances. The cataclysmic eruption of Mount St. Helens (Washington, USA) in 1980 produced a heterogeneous landscape of disturbance conditions, including primary to secondary successional habitats, affording a unique opportunity to explore how rates and patterns of community change relate to disturbance severity, post‐eruption site conditions and time.In this novel synthesis, we combined data from three long‐term (c. 30‐year) studies to compare rates and patterns of community change across three 'zones' representing a gradient of disturbance severity: primary successional blast zone, secondary successional tree blowdown/standing snag zone and secondary successional intact forest canopy/tephra deposit zone.Consistent with theory, rates of change in most community metrics (species composition, species richness, species gain/loss and rank abundance) decreased with time across the disturbance gradient. Surprisingly, rates of change were often greatest at intermediate‐severity disturbance and similarly low at high‐ and low‐severity disturbance. There was little evidence of compositional convergence among or within zones, counter to theory. Within zones, rates of change did not differ among 'site types' defined by pre‐ or post‐eruption site characteristics (disturbance history, legacy effects or substrate characteristics).Synthesis. The hump‐shaped relationships with disturbance severity runs counter to the theory predicting that community change will be slower during primary than during secondary succession. The similarly low rates of change after high‐ and low‐severity disturbance reflect differing sets of controls: seed limitation and abiotic stress in the blast zone vs. vegetative re‐emergence and low light in the tephra zone. Sites subjected to intermediate‐severity disturbance were the most dynamic, supporting species with a greater diversity of regenerative traits and seral roles (ruderal, forest and non‐forest). Succession in this post‐eruption landscape reflects the complex, multifaceted nature of volcanic disturbance (including physical force, heating and burial) and the variety of ways in which biological systems can respond to these disturbance effects. Our results underscore the value of comparative studies of long‐term, ecological processes for testing the assumptions and predictions of successional theory. We combined data from three 36‐year studies to compare rates and patterns of community change across a gradient of disturbance severity on Mount St. Helens volcano. We found community change relationships with disturbance severity run counter to theory predicting that change will be slower during primary than during secondary succession. Rather, the similarly low rates of change after high‐ and low‐severity disturbance reflect differing sets of controls. Sites subjected to intermediate‐severity disturbance were the most dynamic. Succession in this post‐eruption landscape reflects the complex, multifaceted nature of volcanic disturbance and the variety of ways in which biological systems can respond to these disturbance effects. [ABSTRACT FROM AUTHOR]

Successional theory lacks an explicit, conceptual integration across types of disturbances and biomes. Most successional research addresses site‐ or process‐specific questions, but extrapolation of the findings to broad scales is limited.Studies of plant succession are often distinguished by the severity of the disturbance that triggers them (severely disturbed: primary; less severely disturbed: secondary). Here, we examine the common assumption that primary and secondary succession differ. We use two anthropogenic disturbances for this comparison, mining and ploughing.Successional generalizations are confounded by a complexity of environmental factors including climatic and geographic variation. We address these issues by contrasting succession across multiple biomes.We selected 166 studies of succession on mining sites (n = 73) or abandoned fields (n = 93) that allowed us to compare successional trajectories in terms of the likelihood of a return to target vegetation, changes in species richness, type of trajectories, and the importance of alien species.Success of both types of succession (a return to target vegetation) differed significantly among biomes, with more likely success in cold than warm biomes (for both primary and secondary seres) and in humid than arid biomes (primary seres only). Primary seres were also more likely than secondary seres to have increases in species richness, a predominance of divergent trajectories, and a lower likelihood that alien species influenced succession.Synthesis. The probability of reaching target vegetation by spontaneous succession is generally greater in biomes at higher versus lower latitudes. Primary and secondary seres differed regarding species richness, trajectories, and the role of alien species. Our results highlight that broad generalizations about succession are possible, despite a paucity of comparable data and our use of only two types of anthropogenic disturbances. Any generalizations that might be found among seres across disturbances and biomes will provide a practical framework for land managers to guide restoration efforts, particularly in poorly studied areas. The probability of reaching target vegetation by spontaneous succession is generally greater in biomes at higher versus lower latitudes. Primary and secondary seres differed regarding species richness, trajectories, and the role of alien species. Our results highlight that broad generalizations about succession are possible, despite a paucity of comparable data and our use of only two types of anthropogenic disturbances. Any generalizations that might be found among seres across disturbances and biomes will provide a practical framework for land managers to guide restoration efforts, particularly in poorly studied areas. [ABSTRACT FROM AUTHOR]

Plant mutualists including arbuscular mycorrhizal (AM) fungi have been postulated as being important drivers of plant community diversity and succession. Late successional plants have been shown to be more responsive to AM fungi and more sensitive to AM fungal species identity, which could generate positive feedback and potentially accelerate succession.We test the effect of AM fungi on plant diversity and on frequency dependence predicted by positive plant–AM fungi feedback across a successional gradient. We created prairie mesocosms comprised of a majority of early successional, equal abundance, and a majority of late successional plant species. We inoculated these mesocosms and a field restoration experiment with 14 different communities of AM fungi from late successional prairies that varied in levels of species richness.Overall, we found that AM fungi increased plant diversity and this was driven by the response of late successional plant species to mycorrhizae. Our results indicate that AM fungal composition is more important than AM fungal diversity per se. We found that the effect of inoculation with a single species or groups of AM fungi depended on whether those fungi benefited late successional plant species. Early successional plants consistently exhibited negative frequency‐dependent growth regardless of fungal composition, while late successional plants demonstrated positive frequency‐dependent growth in our mesocosms—but only in the presence of beneficial AM fungal species. These results are consistent with positive plant–mycorrhizal feedbacks accelerating plant community successional trajectories once late successional plants establish. Mesocosm results were mirrored with field inoculation assays where we found that beneficial AM fungi facilitated late successional plant establishment.Synthesis. Our results provide support for beneficial arbuscular mycorrhizal fungi being a primary mechanism for positive plant–soil feedback driving plant community succession, as late successional seedlings grew faster and larger when their neighbours were also late successional plant species when they were associated with beneficial arbuscular mycorrhizal fungi. We found that this positive feedback thereby accelerated succession in mesocosms and in the field. Our results provide support for beneficial arbuscular mycorrhizal fungi being a primary mechanism for positive plant–soil feedback driving plant community succession, as late successional seedlings grew faster and larger when their neighbours were also late successional plant species when they were associated with beneficial arbuscular mycorrhizal fungi. We found that this positive feedback thereby accelerated succession in mesocosms and in the field. [ABSTRACT FROM AUTHOR]

Most fragmentation research focuses on the effects of carving up old‐growth forests, but less is known about influences of habitat fragmentation on secondary succession in patches of regenerating forests.Working with forest dynamics on islands in a vast lake created by a hydroelectric dam in China (the Thousand Island Lake), we sampled 29 islands that were cleared of forest during dam construction in 1959 and then underwent succession. Measurements taken in 2009–2010 and 2014–2015 evaluated community assembly during succession, based on species diversity, functional traits and structural properties.Forests on small islands remained at relatively early stages of compositional succession: species richness was low, and communities were dominated by early‐successional species, with few animal‐dispersed and shade‐tolerant plants. However, these islands had accumulated similar above‐ground biomass density to that on larger islands, mostly in the stems of a fast‐growing pine species. Island size was the key driver of secondary succession in regenerating forest fragments, while isolation had comparatively little effect. Edge effects were important for species composition and functional composition.Synthesis. Habitat fragmentation resulting from the creation of an artificial lake affected community assembly, with fewer late‐successional species on smaller islands. Maintenance of large fragments is critical for the rapid succession of forests. Paradigms on habitat fragmentation effects drawn from old‐growth forest studies are unlikely to hold in regenerating forest fragments. Restoration activities should consider landscape patterns to accelerate secondary succession of regenerating forests. Forests on small islands remained at relatively early stages of compositional succession: species richness was low, and communities were dominated by early‐successional species, with few animal‐dispersed and shade‐tolerant plants. Maintenance of large fragments is critical for the rapid succession of forests. Restoration activities should consider landscape patterns to accelerate secondary succession of regenerating forests. [ABSTRACT FROM AUTHOR]

Darwin's naturalisation hypothesis posing that phylogenetic distance of alien species to native residents predicts invasion success, and Elton's diversity–invasibility hypothesis posing that diversity of native communities confers resistance to invasion, are both rooted in ideas of species coexistence. Because the two hypotheses are inherently linked, the mechanisms underlying them may interact in driving the invasion success. Even so, these links and interactions have not been explicitly disentangled in one experimental study before.To disentangle the links between the two hypotheses, we used 36 native grassland herbs to create greenhouse mesocosms with 90 grassland communities of different diversities, and introduced each of five herbaceous alien species as seeds and seedlings. We used phylogeny and four functional traits (plant height, specific leaf area, leaf size, and seed mass) to calculate different measures of phylogenetic and functional distance and diversity. Specifically, we tested how the alien–native distance (phylogenetic or functional) and the native diversity (phylogenetic or functional) affected each other in their effects on germination, seedling survival, growth, and reproduction of the aliens.Overall, our results supported both hypotheses. Multivariate functional distance based on four traits jointly had stronger positive effects than phylogenetic distance and the univariate ones based on each trait separately. Moreover, the aliens were more successful if they were more competitive by being taller and having larger leaves with a lower SLA than the native residents. Univariate functional diversity based on each trait separately had stronger negative effects than phylogenetic and multivariate functional diversity. Most importantly, we found that the effects of alien–native phylogenetic and multivariate functional distance became stronger as diversity increased. Our analyses with single traits also showed that the strength of the effects of both alien–native hierarchical functional distances (indicative of competitive inequalities) and absolute functional distances (indicative of niche differences) increased at higher diversities, where competition is more severe.Synthesis. Our study explicitly demonstrates for the first time how the mechanisms underlying the two classical invasion hypotheses interact in driving invasion success in grassland communities. This may help to explain some of the puzzling results of studies testing either of the two hypotheses. This study explicitly demonstrates how the mechanisms underlying the two classical invasion hypotheses, Darwin's naturalisation hypothesis and Elton's diversity–invasibility hypothesis, interact in driving the success of alien species in experimental grassland communities. Our findings could help explain some of the puzzling results of studies testing either of the two hypotheses. [ABSTRACT FROM AUTHOR]

Successional change following disturbance is a fundamental ecological process that remains central to understanding patterns in plant ecology. Although succession has been studied for well over a century, understanding of the patterns and processes of change is still inadequate, partly because of the dearth of long‐term studies.Here, we use, as a model system, a volcanic disturbance that is widespread and of global relevance. We examine succession in old‐growth conifer forest understories following burial by tephra (aerially transported volcanic ejecta) in the 1980 eruption of Mount St. Helens. Using four sites with different initial conditions and amounts of disturbance (tephra burial), we sampled plant communities at years 1, 20, and 36 since the eruption using permanent plots representing two treatments: undisturbed tephra and control plots from which tephra was experimentally removed. By using this long‐term data, we were able to gauge change through time and differences between tephra‐disturbed and control plots.In tephra‐impacted plots, cover reached preeruption levels by year 36 except for bryophytes at three sites and shrubs at one site. Cover in control plots also increased significantly for all growth forms except bryophytes, remaining above that on tephra plots at the same site in most situations. Sites generally increased in species richness first, and then gradually increased in evenness and Shannon's diversity; after 36 years, differences between control and tephra‐impacted plots remained at only one site. Community composition was stable in one site and shifted gradually through time at the two other sites, and differences between plot types persisted at one site. Communities change over 36 years could relate to various endogenic and abiotic factors.Synthesis. These data suggest that, while recovery to the predisturbance status occurs in some cases, recovery is site‐specific. Understorey communities can be dynamic, even in old‐growth forests, and may still be responding to disturbance over three decades later. Long‐term experimental studies are key to understanding succession patterns and generalizations about the importance of initial conditions, disturbance intensity, and the complexity of interactions that determine vegetation change. Succession following disturbance may follow predictable trajectories or result in surprising outcomes. During 36 years following tephra deposition from the 1980 eruption of Mount St. Helens (USA), understories recovered in some but not other old‐growth forests, and plant communities demonstrated dynamic responses in both natural tephra and cleared plots. Long‐term measurements were key to understanding complex community change in response to volcanic disturbance. [ABSTRACT FROM AUTHOR]

A central aim of invasion biology has been to identify key functional differences between native and exotic species to determine which traits may be responsible for invasion success and impacts. There are two primary ways that differences may exist between native and exotic species—the traits of the local species pools may differ, or the way that the traits interact with their environment may differ.We explored leaf nutrient concentrations as functional traits that directly link to plant metabolic processes by sampling healthy, mature leaves from 119 native and exotic taxa across a wide range of successional statuses in New Jersey, USA. Leaf nutrient concentration data (carbon, calcium, magnesium, nitrogen, phosphorus, potassium) were paired with long‐term community dynamics from the Buell–Small Succession Study to evaluate abundance‐weighted trait values over succession for native and exotic species.After accounting for differences across growth forms, there were minimal differences in foliar nutrients based on plant origin, with only lower leaf carbon and higher leaf potassium in exotic species. However, these differences were not sufficient to generate overall differences between native and exotic species in a multivariate analysis. In contrast, the successional trajectories of the abundance‐weighted trait values for most leaf nutrients differed strongly between native and exotic plants. While this pattern may be partially attributable to variation in the species pool for carbon and potassium, successional processes generated differential sorting, suggesting underlying differences in how the same traits function in native and exotic assemblages.Synthesis. These results suggest that both variation in the species pool and variation in the successional selection of plant traits can generate functional differences between native and exotic plants. Assessments of trait differences between native and exotic species will require information on traits and plant performance to unambiguously link traits to function in dynamic plant communities. Analysis of a long‐term dataset suggests that both variation in the species pool and variation in the successional selection of plant traits can generate functional differences between native and exotic plants. Assessments of trait differences between native and exotic species will require information on traits and plant performance to unambiguously link traits to function in dynamic plant communities. [ABSTRACT FROM AUTHOR]

Primary succession encompasses the earliest and most fundamental stages of community assembly. The relative contributions of plant dispersal and ecosystem development, the main drivers that control the rate of primary succession, remain largely unknown, in spite of their central roles in community organization in general. Understanding the contribution of dispersal is especially critical because it casts light on our ability to manage succession resulting from climate change or anthropogenic disturbance.Here, we review the literature in order to understand when and where dispersal limits primary succession. Studies from many systems (tropical, temperate, boreal, arctic, alpine, floodplain forest, desert, mines, volcanic eruption and glacier forelands) show that dispersal limitation occurs consistently in the early stages of primary succession, suggesting that this is a general pattern. On the other hand, we found strong biases in study sites towards the Northern Hemisphere, temperate regions, volcanic eruptions and glacier forelands, which suggests that there are risks in drawing general conclusions about the importance of dispersal for primary succession for other biomes.Little is known about the contribution of dispersal to the later stages of primary succession. We present a recently developed method, multiscale chronosequence comparison that compares rates of succession in similar systems at relatively small and large spatial scales. Rapid succession at small scales compared to large scales suggests that seed dispersal influences succession over time periods of centuries and also limits the development of ecosystem functions such as vegetation cover and soil carbon accumulation.Synthesis: Dispersal limitation likely matters not only in the early stages but also in the late stages of primary succession by controlling the rate at which new species arrive. Both the accumulation of comparable case studies and novel approaches, such as multiscale chronosequence comparisons and factorial experiments, in contrasting biomes, are necessary to clarify the generality or context dependency of the role of dispersal in future primary successions undergoing changing climate. Dispersal limitation likely matters not only in the early stages but also in the late stages of primary succession by controlling the rate at which new species arrive. Both the accumulation of comparable case studies and novel approaches, such as multiscale chronosequence comparisons and factorial experiments, in contrasting biomes, are necessary to clarify the generality or context dependency of the role of dispersal in future primary successions undergoing changing climate [ABSTRACT FROM AUTHOR]

Plant-soil interactions are temporally dynamic in ways that are important for the development of plant communities. Yet, during primary succession, the degree to which changing soil characteristics (e.g. increasing nutrient availabilities) and developing communities of soil biota influence plant growth and species turnover is not well understood., We conducted a two-phase glasshouse experiment with two native plant species and soils collected from three ages (early, mid- and late succession) of an actively developing glacial chronosequence ranging from approximately 5 to <100 years in age. The first phase assessed how soil abiotic characteristics and soil biota immediately influenced plant performance. In the second phase, we used conditioned soils to grow the same plant species and assessed how the direction and strength of plant-soil feedback ( PSF) varied through succession. We used high and low nutrient and soil sterilization treatments to isolate effects of abiotic and biotic factors on plant performance and to assess how patterns of PSF related to soil nutrients., For both species, our experiments revealed that the initial effect of soil biota on plant performance depended on successional stage. In soils collected from early-, mid- and late-succession stages, we observed neutral to negative, negative and positive effects of soil biota on plant performance, respectively., Plant-soil feedback varied with successional stage and depended on whether microcosms were supplied with nutrients. Under low nutrient conditions, soil conditioning by plants, unrelated to initial soil biota, was an important mechanism for positive PSF. Under high nutrient conditions, PSFs differed by plant species in early- and mid-succession soils, but were consistently neutral in late succession., Synthesis. Soil biota can affect the performance of pioneer plants over short gradients of ecosystem development, but the strength and direction of interactions depend on nutrient availability. Conceptual frameworks describing mechanisms of primary succession should acknowledge soil conditioning by previous plants as a potential mechanism of positive feedback. [ABSTRACT FROM AUTHOR]

Invasive herbivores can strongly affect ecosystems by reducing or removing native plant species, and early in primary successions they could have enduring consequences for plant community assembly and ecosystem functioning, although this has seldom been explored. Invasive brushtail possums ( Trichosurus vulpecula) browse from ground levels to forest canopies in New Zealand, including on plant species common early in primary succession., We used exclosures (fenced on the top as well as the sides) and corresponding control plots to study effects of brushtail possums on primary successions on bare landslide surfaces in the South Island of New Zealand. We then conducted repeated measurements of the plant community over 11 years and at the end also quantified soil abiotic and biotic properties., Above-ground, plant biomass increased from close to zero to > 1000 g dry mass m−2 after 11 years in both exclosures and control plots, with significantly more biomass of the N2-fixing tree Carmichaelia odorata in the controls. Brushtail possums reduced the biomass in the control plots of small-stature grasses and sedges in the first 3 years. Plant species richness was greater in control than exclosure plots throughout the experiment., Below-ground, soil carbon and nitrogen concentrations and the biomass of all major soil microbial groups were significantly greater in the control than exclosure plots, although soil nematode abundances were not. Below-ground effects could be attributed to the greater biomass of Carmichaelia in control plots., Synthesis. Our study shows that an invasive herbivore exerted strong effects on the rate and trajectory of primary succession by altering plant community assembly. Herbivore exclusion resulted in reduced biomass of a key N2-fixing tree that drives forest development, with important below-ground consequences. These results support a view that restoration of ecosystems needs to consider the consequences of altering plant community structure before removing invasive herbivores. [ABSTRACT FROM AUTHOR]

A broad and diversified group of compounds, secondary metabolites, are known to govern species interactions in ecosystems. Recent studies have shown that secondary metabolites can also play a major role in ecosystem processes, such as plant succession or in the process of litter decomposition, by governing the interplay between plant matter and soil organisms., We reviewed the ecological role of the three main classes of secondary metabolites and the methodological challenges and novel avenues for their study. We highlight emerging general patterns of the impacts of secondary metabolites on decomposer communities and litter decomposition and argue for the consideration of secondary compounds as key drivers of soil functioning and ecosystem functioning., Synthesis. Gaining a greater understanding of plant-soil organisms relationships and underlying mechanisms, including the role of secondary metabolites, could improve our ability to understand ecosystem processes. We outline some promising directions for future research that would stimulate studies aiming to understand the interactions of secondary metabolites across a range of spatio-temporal scales. Detailed mechanistic knowledge could help us to develop models for the process of litter decomposition and nutrient cycling in ecosystems and help us to predict future impacts of global changes on ecosystem functioning. [ABSTRACT FROM AUTHOR]

Herbivory can drive rapid evolution of plant chemical traits mediating defensive and competitive ability. At a geographic scale, plant populations that escape selection from their ancestral herbivores may evolve decreased defence and increased competitiveness. While contrasts between native and invasive populations of plants lend support to this hypothesis, such experiments cannot establish causal links between herbivory and evolved invasive phenotypes., Here, we conducted geographic contrasts, and coupled these with long-term selection experiments that directly test for evolutionary responses to herbivore exclusion. In common gardens, we contrasted Solidago altissima genotypes that were historically exposed or protected from herbivory across two experimental time-scales: (i) a natural experiment where plant populations evolved either with native herbivory (in Minnesota and New York) or evolved relatively free from herbivory for ˜100 years in Japan, and (ii) a 12-year manipulative experiment where plants were either exposed to ambient herbivory or treated with insecticide., In both experiments, plant populations responded to herbivore release by evolving increased production of root allelochemicals and interspecific competitive ability against Poa pratensis. While plant resistance to a beetle herbivore did not diverge between plant origins, we still observed parallel evolutionary shifts in leaf secondary metabolite and protease inhibitor production, which may confer resistance to diverse herbivore species., Synthesis. Observed evolutionary convergence for multiple plant traits, between the natural and manipulative experiments, emphasizes the role of insect herbivores as key drivers of plant adaptation and geographic differentiation. [ABSTRACT FROM AUTHOR]

Hundreds of studies have evaluated the dynamics of plant invasions and their impacts on native plant communities and ecosystem functions, but most are limited in duration to only one or a few years. As such, we have a poor understanding of how invader dynamics and impacts change over time., This special feature presents six studies that use literature reviews, field studies and experiments to examine long-term patterns in invader effects on species, communities and ecosystems. All studies in the special feature focus on data collected over multiple years and two studies provide data that cover multiple decades., One study provides a review and framework for understanding how invaders impact plant-mycorrhiza mutualisms and two studies focus on long-term ecosystem changes in response to invasion and fire. The next two studies examine how invaders respond to successional change and climate conditions over time, and the final study shows that invaders can shift selection regimes and the evolutionary trajectory of native plant populations., Synthesis. Articles in this special feature demonstrate changes in the dynamics of invasive plant populations and their community and ecosystem impacts over time. Together they illustrate that findings from a snapshot in time may poorly describe years-long outcomes of invasions, and they highlight the need for long-term studies of biological invasions. [ABSTRACT FROM AUTHOR]

A plant that causes specific changes to soil biota may either positively or negatively affect the performance of the plant that subsequently grows in that location. These effects, known as plant-soil feedback, can affect plant species diversity at multiple spatial scales., It has been hypothesized that positive plant-soil feedback reduces alpha (local) diversity by allowing dominance by early-arriving species, but increases gamma (regional) diversity by promoting community divergence (increased beta diversity) through the emergence of alternative stable states. In contrast, negative plant-soil feedback has been thought to increase alpha diversity by allowing local species coexistence, but to reduce gamma diversity by promoting community convergence (reduced beta diversity). Although widely accepted, these hypotheses do not consider the possibility that plant species differ in their effect on, and their response to, a given other species via soil biota. In reality, plant-soil interactions can be complex, with the strength of the interactions variable between plant species. Using a basic simulation model of plant community assembly, we investigated how complex plant-soil interactions might affect plant diversity during succession., When we included only positive or negative intraspecific plant-soil feedback in the model, with no variation in the strength of interspecific plant-soil interactions, results were consistent with the conventional hypotheses. When we allowed the strength of plant-soil interactions to differ between species, plant-soil interactions enhanced alpha diversity initially and beta and gamma diversity subsequently. Diversity enhancement occurred not necessarily because alternative stable states emerged, but primarily because complex plant-soil interactions lengthened the time during which local species composition changed. Due to the longer time for changes in species composition, the high level of beta and gamma diversity at the early stage of succession was maintained for a long time despite eventual community convergence. Thus, diversity enhancement was often transient, though long-lasting, making the conventional concept of alternative stable states inadequate for explaining diversity., Synthesis. Based on these findings, we propose the new hypothesis that complex plant-soil interactions enhance plant species diversity by delaying community convergence. This hypothesis highlights the role of plant-soil interactions as a driver of long-lasting transient dynamics of community assembly. [ABSTRACT FROM AUTHOR]

Legacy effects of plant influences on abiotic and biotic soil properties can result in priority effects that influence the structure and composition of plant communities. To better understand the role of these plant-soil interactions, here we expand the concept of plant-soil feedbacks from a within-species approach (intraspecific plant-soil feedback) to a between-species approach (interspecific plant-soil interactions). In a greenhouse experiment, we tested how the early successional Jacobaea vulgaris affects its own performance and the performance of 30 co-occurring plant species via changes in abiotic and biotic soil conditions. In addition, we examined the reciprocal effect of the co-occurring species on J. vulgaris. Our study had three important results. First, J. vulgaris exhibits strong negative plant-soil feedback. Secondly, there were large differences among the co-occurring species in interspecific plant-soil effects on J. vulgaris growth. Approximately, half the species reduced J. vulgaris performance, whereas the other half had no effect. Thirdly, soil conditioned by J. vulgaris had a positive or neutral effect on the growth of the co-occurring species. To test the soil effects of entire plant communities, in 10 old-fields that differed in time since abandonment we recorded the identity of all plants surrounding J. vulgaris individuals. We calculated the weighted soil effect of this community on J. vulgaris and the reciprocal effect of J. vulgaris on the community. There was a positive linear relationship between time since abandonment and the weighted feedback effect of J. vulgaris on the plant community. We suggest three mechanisms how the legacy of plant-soil interactions may enhance the rate of succession through priority effects: early successional plant species exert negative plant-soil feedback; co-occurring plant species cause negative interspecific plant-soil effects to the early successional species; and the early successional species have overall positive interspecific plant-soil effects on the co-occurring plant species. Synthesis. The performance of an early successional species can be reduced directly by the legacy effects of intraspecific plant-soil feedback, as well as indirectly by the legacy effects of both intra- and interspecific plant-soil interactions. These intra- and interspecific plant-soil interactions can prioritize transitions of plant species in plant communities. [ABSTRACT FROM AUTHOR]

1. Conceptual models of ecosystem development commonly predict a phase of initial colonization characterized by the nucleation, growth and coalescence of discrete patches of pioneer plants. Spatiotemporal dynamics during subsequent development may follow one of three different models: the classical model, in which initially discrete patches of competitive dominant (secondary) colonists coalesce to form a homogeneous cover; the patch dynamics model, in which renewal mechanisms such as disturbance create a shifting mosaic of patches at different stages; and the geoecological model, in which the vegetation gradually differentiates along edaphic gradients related to the underlying physical template. 2. These models of spatiotemporal dynamics were tested using vegetation and soil data from an 850-year chronosequence, comprised of seven lava flows on Mt Hekla, Iceland. The scale and intensity of spatial pattern were quantified on each flow using spatial analyses (mean-variance ratios, quadrat variance techniques and indices of autocorrelation). Changes in spatial pattern with increasing terrain age were compared with predicted trajectories, in order to identify which of the models of spatiotemporal dynamics was most consistent with the observations. 3. The early stages of ecosystem development were characterized by colonization of the pioneer species, especially Racomitrium mosses, in discrete patches (‘Pioneer colonization stage’, < 20 years), which then grew laterally and coalesced to form a continuous, homogeneous carpet (‘Pioneer expansion stage’, 20–100 years). Later in the sequence, higher plants established in discrete patches within this pioneer matrix (‘Higher plant colonization stage’, 100–600 years). Over time, heterogeneity re-emerged at a larger spatial scale as the vegetation differentiated according to topographic variations in the underlying substrate (‘Differentiation stage’, > 600 years). 4. Synthesis. The spatiotemporal dynamics observed in the early stages of this succession were consistent with a model of pioneer nucleation in micro-scale safe sites, followed by growth, coalescence and eventual fragmentation of pioneer patches. The spatial patterns which emerged later in development support the geoecological model, with spatial differentiation of vegetation related to meso-scale substrate topography. The findings provide insight on how vegetation patterns emerge at different stages of ecosystem development in response to differing scales of heterogeneity in the underlying physical environment. [ABSTRACT FROM AUTHOR]

1. The effects of litter on seedling emergence (e.g. during succession from grassland to woodland) may not only depend on litter amount and environmental conditions but may also be related to litter types. We tested the effect of litter types, litter cover and soil moisture on the emergence of four congeneric pairs of grassland and woodland species. 2. We carried out a controlled pot experiment (Experiment I) using litter and species from two habitats (grassland vs. woodland), three levels of litter cover (low, medium, high) and two levels of water-addition (leading to constantly humid or intermittently dry substrate). Amounts of litter were adjusted to result in the same relative light reduction for both litter types. Consequently, we applied 2 g, 4 g and 8 g of grassland litter and 0.5 g, 1 g and 2 g of woodland (oak) litter per pot. 3. To separate the shade effect of litter from its mechanical plus chemical effects we exposed additional pots with seeds of the same species to deep shade conditions (Experiment II) corresponding to 4 g and 1 g of grass and oak litter, respectively. 4. Under intermittently dry conditions both litter types increased seedling emergence. In addition, we found a significant interaction between litter type and species origin: seedling emergence of woodland species was significantly lower from beneath grass litter than from beneath oak litter, whereas grassland species emerged equally well from beneath both litter types. Compared with seed germination under a shade cloth, seedling emergence of woodland species from beneath grass litter was reduced by 44%. Litter significantly affected soil humidity and the amplitude of diurnal temperature fluctuations. Differential effects of litter types on woodland and grassland species are probably related to litter structure. 5. Synthesis. Our experimental data present evidence that ecosystem specific litter effects slow down succession from grassland to woodland and that the effect size is controlled by the litter amount present and the environmental conditions. [ABSTRACT FROM AUTHOR]

1 Intact, closed canopied forests appear highly resistant to exotic plant invasions, but there are few experimental studies of this observation. To test this issue and explore the conditions that foster resistance, we experimentally added Norway maple ( Acer platanoides L.) seeds to intact forests for 3 years and monitored emergence, survivorship and height growth for 5 years. 2 Seed additions (250 seeds−1 m2) were replicated in situ in combinations of light (deep shade vs. small gaps), soil fertility (NO3 and pH), and variation in soil moisture as influenced by topography (hill slopes vs. flat areas at slope bases) in five eastern deciduous forests in central New York and southern Connecticut. We then parameterized a model with this data to project long-term rates of sapling recruitment. 3 Seedlings had high survival and low growth rates in the deep shade, suggesting that this species readily forms a seedling bank in intact forests. By age 5, annual survivorship reached 93% in deep shade and 98% in small gaps. Median seedling heights were ≤ 10 cm in all treatments after 5 years, though the largest seedlings were markedly taller in gaps. Mean year 5 densities of all experimental seedlings (ages 3–5 years) were 14 seedlings−1 m2 (± 2.4 SE) in the shade and 19 seedlings−1 m2 (± 3.5 SE) in small gaps. 4 While seedlings colonized in all conditions, resistance to invasion varied markedly; resistance was highest in deeply shaded, acidic conditions (pH < 4.5). Small gaps initially promoted invasion, but by age 4 shade survivorship rates were equivalent to gaps. Higher soil pH (especially > 6) also significantly increased survivorship, particularly in deep shade. Shading's main effect was to suppress height growth. Overall, the model predicted impressive sapling recruitment; even in deeply shaded, acidic conditions, approximately 1% of seeds emerge and survive to become saplings. 5 Intact forests only weakly resisted A. platanoides colonization, but strongly suppressed its rate of invasion. As such, the frequency of disturbance, though ultimately unnecessary for A. platanoides invasions, will strongly influence its near-term invasiveness. Dispersal limitation and slow stand dynamics appear to be the primary constraints on its current distribution. [ABSTRACT FROM AUTHOR]

1 The cover of plant species was recorded annually from 1988 to 2000 in nine spatially replicated plots in a species-rich, semi-natural meadow at Negrentino (southern Alps). This period showed large climatic variation and included the centennial maximum and minimum frequency of days with ≥ 10 mm of rain. 2 Changes in species composition were compared between three 4-year intervals characterized by increasingly dry weather (1988–91), a preceding extreme drought (1992–95), and increasingly wet weather (1997–2000). Redundancy analysis and anova with repeated spatial replicates were used to find trends in vegetation data across time. 3 Recruitment capacity, the potential for fast clonal growth and seasonal expansion rate were determined for abundant taxa and tested in general linear models (GLM) as predictors for rates of change in relative cover of species across the climatically defined 4-year intervals. 4 Relative cover of the major growth forms present, graminoids and forbs, changed more in the period following extreme drought than at other times. Recruitment capacity was the only predictor of species’ rates of change. 5 Following perturbation, re-colonization was the primary driver of vegetation dynamics. The dominant grasses, which lacked high recruitment from seed, therefore decreased in relative abundance. This effect persisted until the end of the study and may represent a lasting response to an extreme climatic event. Journal of Ecology (2004) 92, 568–576 [ABSTRACT FROM AUTHOR]

Summary 1 Direct observations of long-term plant succession can be made using quantified plant macrofossil records from peat bogs, providing a means to re-evaluate theories of succession previously based on time-space substitution studies or field stratigraphic surveys. 2 Multiple successions from fen towards raised mire recorded at Crymlyn Bog demonstrate that divergent pathways exist, even when initial conditions are similar within a single bog. 3 Over time-scales relevant to the later stages of mire succession, allogenic forcing factors are significant and may be responsible for driving the direction and rate of species turnover in both forward and reversed hydroseral successions. 4 Differences in the local climatic regime may be responsible for the contrasting character of the mid- and late-Holocene transitional mire communities represented in Core CRB93 at Crymlyn Bog. 5 Plant macrofossil analyses show that Sphagnum is not always a dominant part of the mire community before the establishment of raised peats. Other species including Eriophorum vaginatum , may be equally important ‘ecosystem engineers’ at the fen–bog transition. [ABSTRACT FROM AUTHOR]

Summary 1 The facilitative and inhibitory effects of a nitrogen-fixing shrub, Carmichaelia odorata , during primary succession were studied using both field measurements in a New Zealand temperate montane valley, and manipulative glasshouse experiments on seedlings of the three dominant tree species, Griselinia littoralis , Metrosideros umbellata and Weinmannia racemosa . 2During a stand development chronosequence of < 100 years in which Carmichaelia colonized, dominated and senesced, there was significant development of soil organic horizons and a large build-up of soil nitrogen, especially in the organic horizon. Soil organic matter and nitrogen levels across the sequence were strongly correlated with the main DCA axis of vascular plant species composition, along which there was change in dominance from herbaceous to woody species. Vegetation increased in height and light levels declined with stand development. 3Similar responses to shade that mimicked that in mature Carmichaelia stands suggested that inhibitory effects were likely to be uniform across the three tree species. 4Nitrogen, either added via Carmichaelia litter or in solution, enhanced shoot biomass and foliar nitrogen concentrations of all three tree species. Growth in soils of increasing development increased foliar nitrogen concentrations for Griselinia and Weinmannia , but not Metrosideros . 5Overall, Metrosideros was the least responsive to potential facilitative effects of Carmichaelia , and Griselinia exhibited the highest degree of plasticity of response. Future forest composition and spatial patterning of species in mixed stands here, as elsewhere, is likely to result from differential facilitative responses during early primary succession. [ABSTRACT FROM AUTHOR]

Abstract 1 We assess the robustness of a 1500-year palaeoclimate data base and forest gap model in simulating northern Scandinavian boreal forest succession since ad 500. We also evaluate trends in species abundance in a nemoral woodland in southern Scandinavia by comparing modelling results to palaeoecological data. 2 Simulated biomass trends for Picea, Pinus and Betula growing at Penningholmen (northern Sweden) are strikingly similar to those observed in the local pollen record, particularly in the replication of the early Little Ice Age (LIA) decline in Betula and the late-LIA dieback of Picea and Pinus. 3 LIA decreases in Betula may therefore be partly due to the effects of climate on its competitive interactions with Pinus, as well as the previously proposed effects of insect herbivory. 4 Simulations of Draved Forest (western Denmark), suggest that Tilia is under-represented in modern-day Scandinavian nemoral woodlands, and consequently that the present dominance of Fagus probably reflects strong human–plant interactions from as early as the beginning of the 17th century. 5 This study highlights the importance, despite general limitations associated with vegetation models, of model-data comparisons for understanding mechanisms and processes underlying past forest succession, and emphasizes the usefulness of forest models for reconstructing climate influences on past vegetation. [ABSTRACT FROM AUTHOR]

Presents a study on plant succession on coastal sand dunes of Lake Michigan. Materials and methods; Results and discussion.

Presents a study which evaluated the intensity of competition and herbivory on the growth of three plant species which are common in European temperate salt marshes. Methodology; Results; Discussion.

Deals with a study of the spatial patterns of plant succession along rivers. Study area; Methods; Results and discussion.

Investigates woodland succession in the Bialowieza Forest in Poland. Details on Bialowieza Forest; Information on studies on the successional aspects of the development of Bialowieza Forest; Methods used in the study; Results and interpretation; Discussion.

Summary We examined the impact of nitrogen addition on early successional dynamics and plant species diversity in replicate plots of an old-field succession treatment in south-western Michigan, USA, for 7 years following abandonment from agriculture. Nitrogen addition significantly increased above-ground plant biomass, but had no effect on the displacement or persistence of different life-history groups. Annual species made up a similar proportion of community biomass and decreased at equivalent rates in control and nitrogen-addition microplots. Perennial species biomass increased at similar rates in the control and nitrogen-addition microplots. Annual species dominated initially, but declined in abundance over the first 4 years and were replaced by biennials and then herbaceous perennials. The resulting high numbers of species losses and gains were not affected by nitrogen addition. Nitrogen addition did not affect mean species density or the Shannon index of diversity. There was also no temporal change in the similarity of species composition between control and nitrogen-addition microplots, indicating that nitrogen addition did not cause divergence over time in community composition. In year 7, similar species dominated the nitrogen-addition and control microplots, but there were differences in species composition and abundance of the subordinate species in each community. Only in year 6 of this study was there a significant negative relationship between community biomass and the Shannon diversity index. There was no significant relationship between community biomass and species density in any of the first 7 years following abandonment. Thus, the community response to increased biomass due to nitrogen addition was expressed primarily through changes in community structure, not richness. The effects of nitrogen addition on the early successional dynamics, species composition and consequently diversity of a plant community may depend on initial site conditions. The response to nitrogen enrichment may be slower in sites such as ours with fertile soils that become dominated by herbaceous perennial dicots. [ABSTRACT FROM AUTHOR]

Examines changes in community structure of tall tussock grasslands. Published models of succession in tall tussock grasslands; Relationship of community structure to site factors; Tendency towards guild proportionality; Factors that influence the changes in species association.

Studies the dynamics of populations of Filipendula ulmaria during succession in the Bilaowieza Forest from 1974 to 1990. Investigation of the pattern of growth and senescence of genets; Role of senescence in genet disintegration; Influence of individuals of different origin on population dynamics; Relationship between age structure of the population and succession.

Studies the factors affecting the plant succession of four bryophyte species. Important role of water type in mineral-rich fens; Influence of nutrient enrichment in some species; Role of interspecific interactions in all species replacement series.

Studies the species dynamics and nutrient accumulation during early primary succession in coastal sand dunes on the Dutch island of Schiermonnikoog. Determinants of variance in species composition; Influence of nitrogen in limiting above aground biomass production; Comparison of nitrogen content in the soil organic layer in the plains versus sand dunes.

Discusses results of a field experiment testing the hypothesis that photosynthetic performance of seedlings in a tropical forest depends on the successional status of the species. Capacity to utilize photon flux density; Rates of dark respiration; Mesophyll conductance; Quantum efficiencies.

Examines seed output, germination and growth of species during the succession from heatherland moorland to mature birch woodland. Decline of number of seeds of Calluna vulgaris with increasing age of birch stands; Persistence of soil seed stores of Agrostis capillaris; Comparison of the regrowth rate of vegetation on the open moor versus beneath the birch.

Discusses plant community succession from heather moorland to birch woodland. Changes in species dominance; Decline of Calluna vulgaries in shaded spots; Growth of birch Betula pendula and B. pubescens; Nutrient competition between plant species.

Examines the effects of changing light intensity and nutrient availability on the growth and competitive abilities of plant species during succession from heather moorland to birch woodland. Timing of the establishment of the plant species; Competitive dominance of Agrostis capillaris over Deschampsia flexuosa and Vaccinium myrtillus; Plant growth response to shade.

Studies the impact of insect herbivory on trifolium pratense growing in different successional age. Comparison of the performance of insecticide-treated plants and control plants with natural levels of insect hervibory; Difference in seed variability; Role of insect herbivory in reducing the survivorship of plants.

Examines the effects of canopy gaps, gopher mounds and grazing on colonization in a successional grassland. Effect of the formation of canopy gaps by the death of individual bunchgrasses and soil disturbances by gophers on colonization success; Assessment of species' abilities to colonize canopy gaps and gopher mounds.

Examines the colonization and inhibition abilities of species in a successional grassland in California. Prediction of population and community change; Successional change in undistributed sites; Dependence of species differences in colonizing ability on the different densities of seed rain.

Examines the species interactions in a successional grassland in California. Species distributions; Seed rain and seedling recruitment; Estimation of seed bank contribution to recruitment using seed exclosures.

Studies the dynamics of the tree layer of the Eragrostis pallens-Burkea africana savanna. General successional sequence; Detrimental effect of porcupines and fire on the development of a mature, closed-canopy woodland; Maintenance of Eragrostis pallens-Burkea africana savanna by porcupines and fire as a mosaic of grassland and small woodland patches undergoing cyclical successions.

Studies acidification and succession in flood-plain mire in the Norfolk broadland in England. Evidence for progressive base-depletion in parts of the fens remote from the river; Factors that influence the vertical movement of the fen mat.

Characterizes the patterns of plant succession in abandoned pastures in Eastern Amazonia. Vegetation composition, structure and biomass accumulation in the pastures; Features of the pastures' ecosystem.

(1) Vegetation dynamics during five years of succession following slash-and-burn agriculture in the upper Rio Negro region of the Amazon Basin were elucidated by combining (i) permanent plot studies of plant-replacement dynamics and productivity (ii) field analyses of the resource-procurement strategies of successional species and (iii) field experiments on the role of regeneration strategies, establishment microhabitats and nutrient availability in controlling succession. (2) The main study plot was dominated by grasses and forbs during the first year of succession and then by pioneer trees particularly Vismia spp. Pioneer trees exhibit greatest establishment m protected farm-site microhabitats, such as under fruit trees and among slash. By five years, Vismia mortality exceeded establishment and pioneer trees of the Melastomataceae were growing in the spaces vacated by Vismia. Primary forest species represented only 7% of all stems at this time. (3) The number of tree species (≥ 2 m tall) increased from seventeen (year 1) to thirtyfive (year 5). The number of pioneer species remained constant (about twelve) while the primary forest species increased slowly. Nevertheless most primary forest species were represented by only one individual after five years. (4) A key factor retarding succession is the slow rate at which primary forest species become established on abandoned farms. Diaspores of forest species that were artificially dispersed to a farm site had high rates of removal by animals. However, the probability that the diaspore of a species would escape removal and germinate increased as diaspore size increased. If these diaspores do germinate, they stand a high chance of surviving seedlings of five forest species transplanted to an abandoned farm showed over 90% survival after 4-5 years. (5) Due to burning and to decomposition of forest wood and root residues, there is a dramatic decline in carbon stocks during slash-and-burn agriculture. After five... [ABSTRACT FROM AUTHOR]

Examines the succession of diatom communities on sand grains. Transition from a flat two-dimensional community to an erect three-dimensional community; Diatom colonization; Influence of disturbance on community structure.

(1) A secondary succession on sandy soil in southern England is represented by seven experimental sites of known successional age. from the colonization of bare ground, through permanent pastureland to birch woodland. The development of the sites over 5 yr is described. (2) Communities of plants and phytophagous Coleoptera (weevils and leaf beetles) from sites of different successional age are defined using reciprocal averaging ordination. (3) The successional communities of phytophagous beetles are characterized by a sequence of dominant species, with the highest dominance occurring during very early colonization and mid-late succession; a pattern also seen in the herbs. (4) The species diversity of herbs and weevils is closely related throughout the succession. It is suggested that plant-species composition may be more important than plant structure in solely phytophagous groups of insects. (5) The host-plant associations of weevils and leaf beetles are discussed in terms of generalism-specialism and niche breadth. Measures for these are described. (6) The occurrence of a higher degree of generalism in weevils in late succession, than predicted in certain models of succession, is explained in terms of Rhoades' and Cates' theories of plant anti herbivore chemistry. [ABSTRACT FROM AUTHOR]

Determines the accumulation of elements by vegetation and their rate of uptake and release through litterfall in stands developed during 20 years after shifting agriculture in north-eastern India. Linear relationship of the elements in the above-ground living biomass to the age of the fallow; Annual rate of accumulation; Enrichment quotient of phosphorus, potassium, nitrogen, calcium and magnesium.

(1) Changes in vegetation structure, species composition, and species dominance were studied over the first twenty-two months of succession after the cutting and burning of several mature tierra firme (i.e. non-flooded) forest sites in south Venezuela in the upper Rio Negro region of the Amazon Basin. To explain the observed succession, additional field investigations were undertaken. (2) Four months after burning the density of plants was less than 1 m[sup -2]. The density of successional woody plants, forbs, and grasses increased rapidly from the fourth to the tenth month of succession. There was little change in plant density between the tenth and twenty-second month, but a large change in vegetation height occurred during this time By the twenty-second month a loose canopy of Cecropta spp was present at 5 m height. (3) Many of the forest tree species sprouted from the stump when cut but burning killed sprouts and significantly reduced the size of the seed bank. Nevertheless the first successional woody colonizers established from seed which survived the burn The first forb and grass colonizers established from seeds dispersed onto the site after the burn. (4) The common successional woody species had bat- or bird-dispersed seeds Many forbs and grasses had wind-dispersed seeds. (5) Population densities were low during the first months of succession because of the low density of propagules and because the low rainfall during this time was not favourable for seedling germination or establishment. The rapid increase in plant density after about the fourth month occurred because the early colonizers had then begun to produce and disperse locally, large numbers of seeds. (6) There were six distinct microhabitat types present on the sites after burning Most species tested showed distinct microhabitat preferences. [ABSTRACT FROM AUTHOR]

Studies the variability of some successional and climax plant assemblage-types using multiple discriminant analysis. Characterization of within- and between-type variability; Representation of between-type variability by the position of the assemblage-types; Significance of the unity of an early-successional assemblage-type.