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Ecological succession – how biological communities re‐assemble and change over time following natural or anthropogenic disturbance – has been studied since the birth of ecology, and the resulting theoretical framework underpins many aspects of the discipline. Recently, the mechanistic basis of classic succession theory has been advanced by studies of plant and microbial interactions, functional traits, and retrogressive stages of ecosystem development. This special issue brings together a series of papers that highlight these contemporary novel approaches and how our understanding of ecological succession has advanced.Four key themes emerge from the issue: (a) generalizations about succession, (b) the influence of dispersal and habitat size on successional trajectories, (c) changes in plant functional traits during succession, and (d) belowground community interactions during long term during ecosystem development.Synthesis. The articles in the special issue highlight novel perspectives on succession theory, revealing the importance of historical contingency, disturbance severity, dispersal limitation, functional traits, and belowground community processes in determining patterns of ecosystem development. Together, they reinforce the importance of ecological succession in understanding the response of plant and microbial communities to disturbance in a changing world. The articles in the special issue highlight novel perspectives on succession theory, revealing the importance of historical contingency, disturbance severity, dispersal limitation, functional traits, and belowground community processes in determining patterns of ecosystem development. Together, they reinforce the importance of ecological succession in understanding the response of plant and microbial communities to disturbance in a changing world. [ABSTRACT FROM AUTHOR]

1. In a recent paper, we analysed the effects of climate, soil and logging disturbance on tree and forest growth (Toledo et al. 2011a). We took advantage of one of the largest data sets in the Neotropics, consisting of 165 1-ha plots and over 62 000 trees distributed over an area of c. 160 000 km2, across large environmental gradients in lowland Bolivia. The main findings were that climate was the strongest driver of spatial variation in tree growth, whereas soils had only a modest effect on growth and that the effect of logging disappeared after a few years. 2. Ferry et al. (2012) suggest that we underestimated the disturbance effects on growth because of a supposedly wrong coding of Time After Logging (TAL) for unlogged plots. Although we have good biological reasons why we coded TAL like we did, we checked Ferry et al.'s suggestions for recoding and found no differences in variables that significantly explained tree and forest growth. We agree, however, that for future research, it is important to go beyond simple descriptors such as time after logging and basal area logged, to better describe the variation in logging impact found in areas under forest management. 3. Ferry et al. claim that we did not define basal area growth properly. We believe this is a semantic issue, as we clearly defined basal area growth as the net change in basal area. This net basal area change in Bolivian forests is indeed relatively high compared to other studies, which may be attributed to the higher soil fertility and biogeographic differences in species composition and their traits. 4. Synthesis. Many apparent discrepancies in the ecological literature arise because tropical forest ecologists tend to see the world from the perspective of their 'own' forest (despite clear biogeographic differences) and try to capture the same ecological processes using different variables and measurement protocols. To advance our understanding and go beyond single-case studies, we need to assemble large databases, quantify forest dynamics and disturbances in similar ways, be aware of differences among forests and analyse environmental dose-response curves. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fluctuations in population abundances are often correlated through time across multiple locations, a phenomenon known as spatial synchrony. Spatial synchrony can exhibit complex spatial structures, termed 'geographies of synchrony', that can reveal mechanisms underlying population fluctuations. However, most studies have focused on spatial extents of 10s to 100s of kilometres, making it unclear how synchrony concepts and approaches should apply to dynamics at finer spatial scales.We used network analyses, multiple regression on similarity matrices, and wavelet coherence analyses to examine micro‐scale synchrony and geographies of synchrony, over distances up to 30 m, in a serpentine grassland plant community.We found that species' populations exhibited a geography of synchrony even over such short distances. Often, well‐synchronized populations were geographically separate, a spatial structure that was shaped mainly by gopher disturbance and dispersal limitation, and to a lesser extent by relationships with other plant species. Precipitation was a significant driver of site‐ and community‐wide temporal dynamics. Gopher disturbance appeared to drive synchrony on 2‐ to 6‐year timescales, and we detected coherent fluctuations among pairs of focal plant taxa.Synthesis. Micro‐geographies of synchrony are an intriguing phenomenon that may also help us better understand community dynamics. Additionally, the related geographies of synchrony and coherent temporal dynamics among some species pairs indicate that incorporating interspecific interactions can improve understanding of population spatial synchrony. [ABSTRACT FROM AUTHOR]

In the southern Great Lakes Region, North America, between 19,000 and 8,000 years ago, temperatures rose by 2.5–6.5°C and spruce Picea forests/woodlands were replaced by mixed‐deciduous or pine Pinus forests. The demise of Picea forests/woodlands during the last deglaciation offers a model system for studying how changing climate and disturbance regimes interact to trigger declines of dominant species and vegetation‐type conversions.The role of rising temperatures in driving the regional demise of Picea forests/woodlands is widely accepted, but the role of fire is poorly understood. We studied the effect of changing fire activity on Picea declines and rates of vegetation composition change using fossil pollen and macroscopic charcoal from five high‐resolution lake sediment records.The decline of Picea forests/woodlands followed two distinct patterns. At two sites (Stotzel‐Leis and Silver Lake), fire activity reached maximum levels during the declines and both charcoal accumulation rates and fire frequency were significantly and positively associated with vegetation composition change rates. At these sites, Picea declined to low levels by 14 kyr BP and was largely replaced by deciduous hardwood taxa like ash Fraxinus, hop‐hornbeam/hornbeam Ostrya/Carpinus and elm Ulmus. However, this ecosystem transition was reversible, as Picea re‐established at lower abundances during the Younger Dryas.At the other three sites, there was no statistical relationship between charcoal accumulation and vegetation composition change rates, though fire frequency was a significant predictor of rates of vegetation change at Appleman Lake and Triangle Lake Bog. At these sites, Picea declined gradually over several thousand years, was replaced by deciduous hardwoods and high levels of Pinus and did not re‐establish during the Younger Dryas.Synthesis. Fire does not appear to have been necessary for the climate‐driven loss of Picea woodlands during the last deglaciation, but increased fire frequency accelerated the decline of Picea in some areas by clearing the way for thermophilous deciduous hardwood taxa. Hence, warming and intensified fire regimes likely interacted in the past to cause abrupt losses of coniferous forests and could again in the coming decades. [ABSTRACT FROM AUTHOR]

Modifications of Amazonian forests by pre‐Columbian peoples are thought to have left ecological legacies that have persisted to the modern day. Most Amazonian palaeoecological records do not, however, provide the required temporal resolution to document the nuanced changes of pre‐Columbian disturbance or post‐disturbance succession and recovery, making it difficult to detect any direct, or indirect, ecological legacies on tree species.Here, we investigate the fossil pollen, phytolith and charcoal history of Lake Kumpaka, Ecuador, during the last 2,415 years in c. 3–50 year time intervals to assess ecological legacies resulting from pre‐Columbian forest modification, disturbance, cultivation and fire usage.Two cycles of pre‐Columbian cultivation (one including slash‐and‐burn cultivation, the other including slash‐and‐mulch cultivation) were documented in the record around 2150–1430 cal. year BP and 1250–680 cal. year BP, with following post‐disturbance succession dynamics. Modern disturbance was documented after c. 10 cal. year BP. The modern disturbance produced a plant composition unlike those of the two past disturbances, as fire frequencies reached their peak in the 2,415‐year record. The disturbance periods varied in intensity and duration, while the overturn of taxa following a disturbance lasted for hundreds of years. The recovery periods following pre‐Columbian disturbance shared some similar patterns of early succession, but the longer‐term recovery patterns differed.Synthesis. The trajectories of change after a cessation of cultivation can be anticipated to differ depending on the intensity, scale, duration and manner of the past disturbance. In the Kumpaka record, no evidence of persistent enrichment or depletion of intentionally altered taxa (i.e. direct legacy effects) was found but indirect legacy effects, however, were documented and have persisted to the modern day. These findings highlight the strengths of using empirical data to reconstruct past change rather than relying solely on modern plant populations to infer past human management and ecological legacies, and challenge some of the current hypotheses involving the persistence of pre‐Columbian legacies on modern plant populations. [ABSTRACT FROM AUTHOR]

Increasing temperatures and human activity are likely to reduce fire return intervals in the seasonal tropics. Anticipating how more frequent fires may alter forest community structure and composition requires understanding how fire intensity and species‐specific responses to fires interact to drive fire‐induced mortality for large numbers of species. We developed an analytical framework to estimate unobserved fire intensities and species‐ and size‐specific susceptibility to fire using observed mortality data.We used census data from a 50‐ha forest dynamics plot in western Thailand to better understand species and community responses to a fire that burned ∼60% of the plot in 2005. Trees species, size and status (live, dead) were censused just before the fire (2004) and again 5 years later (2009). We jointly estimated a map of relative fire intensity and species‐specific size‐dependent background and fire‐induced mortality. We then calculated the time required for individuals of each species to reach a fire‐safe size threshold (the age at which the fire‐induced mortality probability was <50%). To better understand community‐level responses to fire, we compared results among different species groups (canopy status, forest‐type association).Our model‐derived map of fire intensity closely matched the field survey taken in the days after the fire. On average, individuals growing at the 95th percentile growth rate for most species groups required ∼5 years to reach their species' fire‐safe size threshold, while individuals growing at the median growth rate required ∼17 years (assuming growth <1 cm diameter at breast height was similar to growth >1 cm). However, understorey species associated with the seasonal evergreen forest took 1.8 times longer than average to reach their fire‐safe size threshold, with one species requiring up to 190 years.Synthesis. Our approach provided insights into spatial patterning of fire intensity in a seasonal tropical forest and species‐ and size‐specific susceptibility to fire‐induced mortality. Our results suggest increasing fire frequency will have the greatest impact on slow‐growing understorey species of the evergreen forest. In addition, our model accurately predicts the growing dominance of a fast‐growing understorey species, Croton roxburghii; Euphorbiaceae, common to evergreen and deciduous forests that can reach its fire‐safe size threshold in 1.3 years. [ABSTRACT FROM AUTHOR]

Human activities modify the disturbance regimes of tropical forests. Since tropical forests host high biological diversity, understanding the role of biodiversity in ecosystem recovery pathways and the underlying ecological mechanisms is crucial to predict the fate of tropical ecosystems. Studies relying on regularly censused forest plots, rarely include disturbed forests, are not long enough to assess long‐term forest dynamics and often lack repeatability.We used an individual‐based model of tropical forest growth to assess the effect of species and functional diversity on long‐term ecosystem recovery from disturbance. We manipulated the number of species and functional assemblages across a large number of simulations and simulated different levels of disturbance. To investigate the ecological mechanisms that underlie the effect of biodiversity on forest functioning along recovery pathways, we partitioned the net effect of biodiversity on ecosystem properties into complementarity and selection effects over time.We found that functional diversity improved tropical forest resilience after a disturbance. The complementarity effect dominated soon after the disturbance but was progressively surpassed by a selection effect as more competitive species dominated the forest community. This pattern increased with the intensity of the disturbance.Synthesis. We found that the mechanisms through which biodiversity influences forest functioning depend on the ecosystem state, shifting from a dominant complementarity effect in recently disturbed systems to a selection effect in systems disturbed a long time ago. Our results thus suggest that the time since the last disturbance is a key to understanding biodiversity–ecosystem functioning relationships in tropical forests and can help reconcile previous contrasting results obtained with snapshots of ecosystem state in empirical studies. [ABSTRACT FROM AUTHOR]

The infrequent and unpredictable nature of earthquakes means that their landslide‐generated impacts on forests are rarely investigated. In montane forests, landslides are the main cause of tree death and injury during earthquakes. Landslides range from soil movements that uproot and bury trees over extensive areas to rock falls that strike individual trees. We examined unexplored relationships between tree survival and distance from an epicentre, soil‐available phosphorus (P) as an indicator of soil development and tree diameter. We expected decreased tree growth in damaged forests because of tree injury.We used a plot network, established in 1974 and resurveyed regularly ever since, to quantify survival and growth responses 6–30 km from the epicentre of a 1994 earthquake in New Zealand's Southern Alps. Our Bayesian analysis used 8,518 trees from 250 plots that representatively sampled a naturally monospecific Nothofagus forest. As the time‐scales over which responses could emerge were unknown, we compared relationships for a pre‐earthquake period with 0–5 years post‐earthquake, and with 5+ years post‐earthquake.Not all plots were affected by the earthquake. We found that 0–5 years post‐earthquake survival increased logarithmically with distance from the epicentre with lowered survival up to 20 km from the epicentre. Survival was low on plots with high soil‐available P. An inverted U‐shaped relationship between survival and diameter pre‐earthquake was not found 0–5 years post‐earthquake. This was because of surprisingly high survival by large trees. The earthquake most often suppressed 0–5 years post‐earthquake growth up to 15 km from the epicentre, but this was only apparent after accounting for more general growth differences among periods. The positive relationship between growth and soil‐available P pre‐earthquake and 5+ years post‐earthquake reflected enhanced growth on young soils. This contrasted with a negative effect of soil‐available P on growth 0–5 years post‐earthquake.Synthesis. Soil‐available P, tree diameter and distance from the epicentre independently determined how tree survival and growth responded to an earthquake. The impacts on survival and growth largely occurred 0–5 years post‐earthquake and suggests a level of resilience in mountain beech forests. [ABSTRACT FROM AUTHOR]

Community assembly changes fundamentally in response to disturbance following habitat destruction due to extreme events and human activities. There are several important aspects of community assembly that can be measured in response to disturbance or during species establishment. Of these measurable outcomes, metrics of taxonomic or species diversity (SD) are perhaps the most common and logistically the easiest to evaluate.It is increasingly evident that measurements of phylogenetic (PD) and functional trait (FD) diversity can provide more information than traditional measures of diversity and desirable and informative metrics to measure restoration outcomes. However, it is unclear whether FD and PD are drivers or a consequence of community assembly.This Special Feature highlights eight field studies and a review that have investigated how PD diversity and functional trait diversity can be used to better understand grassland community assembly following disturbance or during restoration, and how as potential drivers they can be manipulated experimentally or incorporated into evolutionary models. Topics include: colonizing species as a function of FD and PD; dominant species origin impacts on subordinate species FD; impacts of environmental gradients such as seed mix richness, first‐year precipitation and restoration age on FD and taxonomic diversity; impacts of drought and resource availability; and a synthesis of studies that measured FD and PD to determine if they provide similar or incongruent inferences for ecological and functional processes.The work in this Special Feature indicates that SD, FD and PD can act as drivers and passengers of community assembly, and often yield different insights. Environmental gradients such as soil nutrients, precipitation and environmental drivers like drought can influence FD and PD of assembling communities in predicted and unexpected ways.Synthesis. Results from the studies in this Special Feature highlight the importance of considering a multitude of ecological and evolutionary drivers of community assembly in grassland ecosystems. Studies pushing this field forward will be those that incorporate or study higher trophic levels, realistically incorporate climate change and disentangle the impacts of FD and PD. [ABSTRACT FROM AUTHOR]

The spread of invasive grasses across Earth are modifying fire cycles resulting in state changes in arid ecosystems. Disturbance, biotic resistance of native biological communities and propagule pressure, are likely the important factors influencing the spread of invasive grasses and their influence on changing fire regimes.Over a 5‐year period (2011–2016), we tested how the potential loss of biotic resistance of native plant and native rodent communities related to fire and rodent exclusion treatments, in concert with increased propagule pressure affected the establishment of Bromus tectorum L. (cheatgrass) and the spread of secondary fires.Our study results suggest that native plant and native rodent communities contribute to biotic resistance against cheatgrass invasion and that fire and high propagule pressure act to diminish biotic resistance by native communities. Five years into the study, cheatgrass establishment was 11‐fold greater in burned plots than in unburned plots (with native plant communities still intact), 2.4‐fold greater in rodent exclusion plots than rodent access plots and 1.8‐fold greater with increased propagule pressure. At the start of the experiment in 2011 cheatgrass was present in the experimental blocks but at very low density (<1 plant/m2). However, by 2016, burned‐rodent excluded plots were fully invaded (1625 stems/m2). High propagule pressure released cheatgrass from biotic resistance of rodent communities in post‐fire conditions but had minimal effects on the biotic resistance of native plant communities in unburned plots. Fire in combination with either rodent exclusion or high cheatgrass propagule pressure produced higher density cheatgrass stands that were positively correlated with the spread of secondary fires that are characteristic of invasive grass‐fire cycles.Synthesis. Loss of native plant cover or reduction in rodent populations due to fire, extreme climatic events or disease outbreaks, which are increasing with human activity, may provide windows of opportunity for invasive grasses to escape biotic resistance and reinforce invasive grass‐fire cycles. [ABSTRACT FROM AUTHOR]

Tree harvest and climate change can interact to have synergistic effects on tree species distribution changes. However, few studies have investigated the interactive effects of tree harvest and climate change on tree species distributions.We assessed the interactive effects of tree harvest and climate change on the distribution of 29 dominant tree species at 270 m resolution in the southern United States, while accounting for species demography, competition, urban growth and natural fire. We simulated tree species distribution changes to year 2100 using a coupled forest dynamic model (LANDIS PRO), ecosystem process model (LINKAGES) and urban growth model (SLEUTH).The distributions of 20 tree species contracted and nine species expanded within the region under climate change by end of 21st century. Distribution changes for all tree species were very slow and lagged behind the changes in potential distributions that were in equilibrium with new climatic conditions.Tree harvest and climate change interacted to affect species occurrences and colonization but not extinction. Occurrence and colonization were mainly affected by tree harvest and its interaction with climate change while extinctions were mainly affected by tree harvest and climate change.Synthesis and applications. Interactive effects of climate and tree harvest acted in the same direction as climate change effects on species occurrences, thereby accelerating climate change induced contraction or expansion of distributions. The overall interactive effects on species colonization were negative, specifically with positive interactive effects at leading edges of species ranges and negative interactive effects at trailing edges. Tree harvest generally did not interact with climate change to greatly facilitate or ameliorate species extinction. Our modelling results highlight the importance of considering disturbances and species demography (e.g. post‐harvest regeneration dynamics) when predicting changes in tree distributions. [ABSTRACT FROM AUTHOR]

Interactions at multiple scales can shape how forest ecosystems respond to both climate change and disturbance. At landscape scales, feedbacks cause vegetation and wildfire regimes to alter one another, while forest patterns at local scales can result from feedbacks between plants and their abiotic environment. Consequently, disturbances and abiotic changes may give rise to forest patterns that further affect processes like wildfire.Examples may exist in the history of subalpine ribbon forests, which are alternating areas of forest and meadow where snow drifting and linear bands of trees depend upon each other. Just as ongoing climate changes may change snow levels and the dynamics in these forests, past climate changes and wildfires may have generated the conditions suitable for ribbon forests.To examine feedbacks in subalpine forests and the potential that climate changes and fires gave rise to ribbon forests, we obtained six fossil pollen records from a subalpine landscape in Colorado. Forests there may have responded to climate change and widespread wildfires ˜1,000 years ago when >80% of sites on the landscape burned within a century. The fires coincided with regional warming, but the extent of burning declined before the climate cooled, possibly driven by changes in fuel structure and composition.The pollen records indicate that large vegetation changes coincided with the widespread wildfires at five of the six sites. Pollen assemblages consistent with ribbon forests first became important at this time as sagebrush (Artemisia) and other meadow taxa increased and conifers, especially spruce (Picea) declined. The ribbon forests emerged as novel fuel breaks at the time when temperatures rose ˜0.5°C but the number of sites burned per century declined. Cooling during the Little Ice Age then expanded the openings and extent of ribbon forests, probably helping to reduce the frequency of fires across our sites to its minimum.Synthesis. The rise of ribbon forests in northern Colorado illustrates how climate and fire can interact to rapidly transform landscapes and disturbance regimes. The interactions can produce forest patterns with unexpected consequences such as reduced wildfire despite regional warming. [ABSTRACT FROM AUTHOR]

Exotic plant species commonly exploit disturbances more successfully than native plants. This outcome is widely attributed to the fact that disturbance reduces biotic resistance from native plant competitors. However, biocrusts, communities of mosses, lichens, and micro‐organisms, are a prominent component of semi‐arid grasslands occurring in the interstitial spaces between vascular plants. Biocrusts may provide an important source of biotic resistance to invaders, different from native plant competition, but poorly understood.We established a large‐scale field experiment to examine how intact versus disturbed biocrusts influenced the emergence and establishment of four native and four exotic plant species in intermountain bunchgrass systems over 2 years—one wet and one dry. We also conducted a complementary greenhouse experiment to explore how differences in moisture might influence biocrust effects on germination.In the greenhouse, biocrusts inhibited the germination of both native and exotic plants in the high moisture treatment only. In field experiments, biocrusts inhibited the overall emergence of exotic seedlings in the wetter of the 2 years and inhibited the establishment of exotic seedlings in both years, but they had no overall effect on the emergence or establishment of native seedlings. We found that intact biocrusts in intermountain grasslands can suppress the establishment of some exotic plants, but have much weaker effects on natives. They also suggest that water availability may influence biocrust effects on seed germination.Synthesis. Our results indicate that intact biocrusts may provide an important source of biotic resistance to exotic plant invasions in intermountain grasslands. Furthermore, precipitation inputs may mediate biocrust effects on plant establishment. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Abstract: Quantifying the variation in community‐level fine root (<2 mm) traits along ecological gradients or in response to disturbances is essential to unravel the mechanisms of plant community assembly, but available surveys are scarce. Whether fine root traits covary along a one‐dimensional economic spectrum, as previously shown for leaves, is highly debated. We measured six fine root traits at the community level along a 69‐year succession, with or without annual mowing, offering a unique design of two nested disturbances. We examined whether (1) there is variation and covariation in community‐level fine root traits along the succession and in response to mowing and (2) morphological root traits mirrored analogous leaf traits (using previously acquired data). Early‐successional communities were herbaceous‐dominated (48 ± 6% in <10‐year‐old plots) and possessed fine roots with high specific root length (SRL), low root dry matter content (RDMC) and low root carbon concentration (RCC), while later successional communities were dominated by woody species (56 ± 9% in >40‐year‐old plots) and possessed opposite trait values. Root nitrogen concentration (RNC) did not vary across communities along the succession. The trait values at community level were not affected by mowing, except for a reduction in root mass density. We found covariation of fine root traits across communities along two dimensions: the first dimension (60% of total variation) represented changes in root foraging capacity (related to SRL) and resource conservation (related to RDMC, RCC, mean root diameter), whereas the second dimension (17%–20% of the variation) represented variations in RNC, potentially related to root respiration and metabolism. Specific root length and specific leaf area were correlated regardless of the mowing regime, but there was no analogous relationship between leaf dry matter content and RDMC in mown communities, showing a decoupling in the investment in tissue density above‐ and below‐ground. Synthesis. Our study demonstrates coordinated variations of community‐level fine root traits along a succession gradient and provides evidence that fine root traits covaried along two dimensions, regardless of mowing regime. The relationship between leaf dry matter content and root dry matter content observed in unmown communities was modified by mowing, reflecting an uncoupled response to mowing. [ABSTRACT FROM AUTHOR]

Despite a large body of research documenting invasive plant impacts, few studies have followed individual invaded sites over decades to observe how they change, and none have contrasted how compositional impacts from invasion compare to ecosystem-process impacts over a multi-decadal time-scale., Using direct measurements of plant density and composition and of ecosystems processes, we evaluate how ecosystem structure, above-ground net primary production ( ANPP), and above-ground and soil nutrient pools compare over 25 years since fire and C4 grass invasions disrupted seasonally dry Hawaiian woodlands. We compare structure and function between primary woodland that has never burned and is largely native species-dominated, with sites that had been the same woodland type but burned in alien-grass-fuelled fires in the 1970s and 1980s. The sites have not experienced fires since 1987., We report here that woody plant composition and structure continue to be dramatically changed by the initial invasions and fires that occurred 25 years ago and invaders continue to dominate in burned sites. This is reflected in continued low plant carbon pools in burned compared to unburned sites. Yet ANPP and N storage, which were dramatically lower in the initial decade after invasive-grass fuelled fires, have increased and are now indistinguishable from values measured in intact woodlands. Soil carbon pools were resilient to both invasion and fire initially and over time., Above-ground net primary production has recovered because of invasion of burned sites by a non-native N-fixing tree rather than because of recovery of native species. This invasive N-fixing tree is unlikely to return C storage of the invaded sites to those of unburned woodland because of its tissue and growth characteristics and its interactions with invasive grasses. It does not facilitate native species but rather promotes a persistent invasive grass/N-fixer savanna., Synthesis. We conclude that fire, an unusual disturbance in this system, has perpetuated the dominance of these sites by invasive species and that despite the dramatic recovery of above-ground net primary production and N pools, the ecosystem continues to be in a distinctly different state than the pre-fire, pre- Melinis community. Thus, despite the absence of further disturbance (fire), there is no evidence that succession towards the original ecosystem is occurring. The fact that N pools and above-ground net primary production recover because of a new invader ( Morella faya), highlights the unpredictability of ecosystem trajectories in the face of altered regional species pools. [ABSTRACT FROM AUTHOR]

Tropical forests play an important role in the global carbon cycle, but the drivers of net forest biomass change (i.e. net carbon sequestration) are poorly understood. Here, we evaluate how abiotic factors (soil conditions and disturbance) and biotic factors (forest structure, diversity and community trait composition) shape three important demographic processes (biomass recruitment, growth and mortality) and how these underlie net biomass change., To test this, we evaluated 9 years of biomass dynamics using 48 1-ha plots in a Bolivian tropical moist forest, and measured for the most abundant species eight functional traits that are important for plant carbon gain and loss. Demographic processes were related to the abiotic and biotic factors using structural equation models., Variation in net biomass change across plots was mostly due to stand-level mortality, but mortality itself could not be predicted at this scale. Contrary to expectations, we found that species richness and trait composition - which is an indicator for the mass-ratio theory - had little effect on the demographic processes. Biomass recruitment (i.e. the biomass growth by recruiting trees) increased with higher resource availability (i.e. water and light) and with high species richness, probably because of increased resource use efficiency. Biomass growth of larger, established trees increased with higher sand content, which may facilitate root growth of larger trees to deeper soil layers., In sum, diversity and mass-ratio are of limited importance for the productivity of this forest. Instead, in this moist tropical forest with a marked dry season, demographic processes are most strongly determined by soil texture, soil water availability and forest structure. Only by simultaneously evaluating multiple abiotic and biotic drivers of demographic processes, better insights can be gained into mechanisms playing a role in the carbon sequestration potential of tropical forests and natural systems in general. [ABSTRACT FROM AUTHOR]

Climate change is predicted to increase the frequency and magnitude of extreme climatic events. These changes will directly affect plant individuals and populations and thus modify plant community composition. Little is known, however, about transgenerational effects (i.e. the influence of the parental environment on offspring phenotype and performance beyond the effects of transmitted genes) of climate extremes and community composition. Perennial plants have been particularly neglected. This impedes projections on species adaptations and population dynamics under climate change., Maternal plants of two widespread dwarf-shrub species ( Genista tinctoria and Calluna vulgaris) recurrently experienced extreme weather event manipulations each year (drought and heavy rain). To test for transgenerational effects of community composition, C. vulgaris maternal plants were grown in communities differing in the number of neighbouring species. After 6 years, seeds of maternal plants were collected at least 2 months after the final weather treatments. We assessed transgenerational effects of the extreme events and of altered community composition on germination and monitored the development of offspring over 2 years., We show that extreme events experienced by maternal plants influence offspring germination and growth beyond the seedling stage. Seeds produced by maternal plants experiencing stress, indicated by increased tissue dieback, germinated earlier in both observed species. We observed differences in leaf stoichiometry and growth rates for G. tinctoria offspring throughout the first year: Offspring from heavy rain-treated mothers showed reduced leaf C:N ratio and higher growth rates. Results further indicate that not only community density, as investigated in prior studies, but also community composition trigger transgenerational effects., Synthesis. Our findings show that variation in the maternal environment not only affects the number, but also the performance of offspring. Extreme climatic events, terminated before seed set, induce transgenerational effects. Species richness of mother communities can affect the stress level of target species and thereby germination regardless of community density. In contrast to prior studies, which revealed direct effects of chronic stress on plant individuals, this study emphasizes the importance of addressing transgenerational effects of extreme weather events when projecting future ecological responses and adaptation to climate change. [ABSTRACT FROM AUTHOR]

Facilitation through physical stress amelioration has been largely overlooked in subtidal marine ecosystems, where abiotic gradients are perceived to be benign. However, seemingly subtle changes in marine environmental conditions can alter community structure across vast areas, and therefore, the type of interactions and any refuge provided by marine foundation species. This could have substantial implications for community organization., We measured net recruitment rates of subtidal seaweeds under experimentally modified canopy densities, across 1000 km of coastline, to examine the nature of interactions between seaweed canopies and recruits., Contrary to expectations, facilitation, as evidenced by higher recruitment under canopies, was observed throughout all conditions for Scytothalia dorycarpa and under partial canopies at three of four locations for Sargassum spp., whilst competitive interactions remained prevalent for Sargassum under closed canopies., Supply side dynamics were also of major importance to recruitment success for Scytothalia. For Sargassum, the interaction strength between recruits and the canopy became increasingly positive towards lower latitudes, suggesting the canopy environment was mitigating stress across the latitudinal climate gradient., Synthesis. Positive interactions and stress amelioration play an important and previously unrecognized role in determining the recruitment success and viability of seaweeds in subtidal marine ecosystems. These results challenge long held paradigms about the general importance of canopy competition and force a rethink of how seaweed interactions affect habitat resilience to disturbances in subtidal ecosystems. [ABSTRACT FROM AUTHOR]

Abiotic variables are critical drivers of succession in most primary seres, but how their influence on biota changes over time is rarely examined. Landslides provide good model systems for examining abiotic influences because they are spatially and temporally heterogeneous habitats with distinct abiotic and biotic gradients and post-landslide erosion., In an 18-year study on 6 Puerto Rican landslides, we used structural equation models to interpret the changing effects of abiotic influences (landslide dimensions, slope, aspect, elevation, parent material and related soil properties) on seed plants (density and diversity), tree fern density, scrambling fern cover, canopy openness and soil development (nitrogen, soil organic matter, pH and cation exchange capacity)., Seven years after landslide formation, catchment size (the landslide area above the point of measurement) was the key abiotic factor influencing plants. The larger the catchment the greater was the diversity and density of seed plants. Conversely, the smaller the catchment the greater was the density of tree ferns and the cover of scrambling ferns., Eighteen years after landslide formation, landslide slope was the key abiotic influence. The greater the slope, the lower was the density and diversity of seed plants and the greater was the scrambling fern cover., Aspect, particularly east-facing slopes exposed to wind disturbances, positively influenced tree fern densities at both 7 and 18 years and negatively influenced seed plants and scrambling ferns at 18 years. Soils were least developed, that is, had lowest soil nitrogen and organic matter concentrations, after 18 years on steep slopes (like seed plants); soils were most developed near landslide edges, on hurricane-exposed slopes (like tree ferns) and where there were high soil potassium concentrations., Synthesis. Abiotic variables have important influences on plant succession on landslides and the relative influence of different abiotic variables changes with time. Improved predictability of temporal dynamics will rely not only on understanding the effects of initial disturbances and subsequent biological responses but also on the different and changing influences exerted by each abiotic variable. [ABSTRACT FROM AUTHOR]

Summary 1. Functional diversity has been suggested as an important descriptor of an assemblage and as an indicator of ecosystem function. However, there has been little testing of recent functional diversity measures on field data and across environmental gradients of disturbance and productivity. This study tested how three recently developed measures of functional diversity behave in practice and what could be deduced about assembly rules operating in the systems studied. 2. Data from 30 plant communities in a small area, comprising arable fields, mown and grazed grasslands, moorland and woodland, were analysed in terms of these diversity indices. Functional Divergence, Evenness and Richness were independent of each other, but Richness correlated to species diversity through the sampling effect. 3. As evidenced by reduced Functional Richness, habitat filtering operated at a significant proportion of the sites sampled. Functional Richness was also reduced against expectations at high levels of both productivity and disturbance. Functional Divergence showed no clear patterns, but Functional Evenness showed a clear promotion by disturbance and a reduction at high standing biomass. 4. Synthesis. Knowledge of how functional diversity is related to the environment provides indications of the processes governing community assembly, and the possibility of developing them as measures of ecosystem function. [ABSTRACT FROM AUTHOR]

Summary 1. Traditional views of ecological disturbance emphasize the role that physical disturbances play in reducing competition between populations and maintaining species coexistence. I present an alternative view that employs a simple Lotka-Volterra model to demonstrate how disturbance resistance, disturbance resilience and resource storage can increase competition between individual perennial plants of similar growth form along a resource supply gradient. 2. In contrasting the growth of individual genets of two hypothetical species, I assumed that traits associated with inherently low module (i.e. plant part) mortality in infertile soils resulted in greater resource storage, but traded off with maximum potential net photosynthesis rates and thus disturbance resilience. 3. The species with more persistent modules (the 'persistent' species) and greater storage produced larger genets and displaced the other species at low gross resource supplies as a result of pre-emption. 4. The species with the greater net photosynthesis rate (the 'resilient' species) gained a size and competitive advantage with increasing gross resource supply, provided senescence of its modules was sufficiently low or there was a constant and equivalent rate of damage to portions of the genets of both species. 5. Selection for disturbance resistance was greater in the persistent species than in the resilient species, which in turn increased the former's competitive ability in moderately resource-rich, disturbance-prone environments. 6. Synthesis. Both resistance and resilience to disturbance potentially increase a species' competitive ability by allowing that species to interfere with the recovery of its competitors from disturbance. Contrary to the view that disturbances must be eliminated from competition experiments to accurately measure the potential for competition to structure plant communities, I conclude that the opposite is true. [ABSTRACT FROM AUTHOR]

The existence of many types of monodominant forests is readily explainable by ecological theory (e.g. early successional forests). Nevertheless, monodominant stands sometimes occur in areas where a much higher diversity typically occurs. Such 'classical monodominance' is not currently readily explained by ecological theory. We briefly review the published mechanisms suggested to cause classical monodominance and then combine them into a new probabilistic conceptual framework to better understand why these systems occur. We build on two theories proposed to explain monodominance: a lack of exogenous disturbance over long periods and species-specific life-history traits. We suggest that certain traits under certain conditions may generate positive feedbacks leading to a greater probability of monodominance being achieved. Such positive feedbacks have the potential to drive a typically diverse system towards a monodominant one. Synthesis. Classical monodominance in tropical forests is hypothesized to be attained when a group of traits occur together under low exogenous disturbance conditions, this giving rise to a series of positive feedbacks. The presented framework links the differing mechanisms proposed in the literature to explain classical monodominance and shows there are potentially alternative routes to monodominance, thus reconciling apparently contradictory observational and experimental results. [ABSTRACT FROM AUTHOR]

1. The experimental removal of early successional species can explain how plant communities change over time. 2. During a 7.3-year period, early successional woody species, scrambling ferns and tree ferns were removed from a total of 10 landslides in the Luquillo Experimental Forest in north-eastern Puerto Rico. 3. Early successional woody plants in combination with tree ferns decreased species richness and cover of forbs and increased richness of late-successional woody plants compared to removals, facilitating long-term forest development. 4. Dense stands of scrambling ferns decreased both forb and woody plant richness compared to removals, inhibiting forest development. 5. Stands of monospecific tree ferns initially increased woody plant richness compared to removals, but overall decreased woody plant richness and cover, inhibiting forest development. 6. Synthesis. Early successional species both facilitate and inhibit succession on tropical landslides, but detailed predictions of successional trajectories remain elusive and are influenced by stochastic processes including arrival order, the life-form of colonizing species and their competitive interactions. [ABSTRACT FROM AUTHOR]

1. We simulated two key components of severe hurricane disturbance, canopy openness and detritus deposition, to determine the independent and interactive effects of these components on woody plant recruitment and forest structure. 2. We increased canopy openness by trimming branches and added or subtracted canopy detritus in a factorial design. Plant responses were measured during the 4-year study, which followed at least 1 year of pre-manipulation monitoring. 3. The physical conditions of canopy openness and detritus deposition in our experiment resembled the responses to Hurricane Hugo, a severe category 4 hurricane that struck this forest in 1989. 4. Canopy detritus deposition killed existing woody seedlings and provided a mechanical barrier that suppressed seedling recruitment. The increase in understorey light caused by canopy trimming stimulated germination from the seed bank and increased seedling recruitment and density of pioneer species several hundred-fold when hurricane debris was absent. Many significant interactions between trimming and detritus deposition were evident from the manner in which seedling density, recruitment and mortality changed over time, and subsequently influenced the composition of woody stems (individuals ≥ 1 cm d.b.h.). 5. When the canopy was trimmed, stem densities increased > 2-fold and rates of recruitment into the stem size class increased > 25-fold. Trimming had no significant effect on stem mortality. The two dominant species that flourished following canopy trimming were the pioneer species Cecropia schreberiana and Psychotria berteriana. Deposition of canopy detritus had little effect on stems, although basal area increased slightly when detritus was added. There were no evident effects of the interactions between canopy trimming and detritus deposition on stems. 6. Synthesis. The separate and interactive effects of canopy openness and detritus deposition result in variable short-term trajectories of forest recovery. However, the short interval of increased canopy openness due to hurricane impacts and its influence on the recruitment of pioneer trees is the dominant factor that drives short-term recovery and may alter long-term structure and composition of the forest. [ABSTRACT FROM AUTHOR]

1. Testing the comparative strength and influence of age and area of islands, proximity of source propagules and disturbances on community assembly, species diversity and vegetation structure has proved difficult at large scales. The little-studied rain forests in the Tropical South Pacific (TSP) provide a unique study area to investigate determinants of community dynamics, with islands varying in age, isolation, area and cyclone frequency. We tested the effects of biogeographical factors and cyclone frequency on the species composition, species diversity and forest structure of old-growth rain forest using 1-ha inventory plots on 12 islands between New Guinea and the Solomon Islands. 2. As predicted by the General Dynamic Model of Oceanic Island Biogeography, the biogeographical variables of archipelago age and island area are the most important factors affecting species richness and diversity, with older and larger islands having higher richness and diversity. There is no significant effect of cyclone frequency on species diversity. 3. The theory that diversity drives endemism is not supported in this system as endemism is not correlated with species diversity. Instead, age and isolation of an island best explain patterns of endemism, with the latter suggesting dispersal limitations between archipelagos. 4. Proximity to source area influences species composition of lowland tropical rain forests in the TSP, which is also supported by a strong correlation between geographic distance and floristic similarity. Vector-fitting onto non-metric multidimensional scaling suggests that archipelago age and cyclone frequency may, in addition to proximity to source area, influence species composition. This implies that a species’ tolerance to cyclones affects its abundance at different cyclone frequencies. 5. Synthesis. Both biogeographical variables (island area and isolation) and cyclone frequency appear to affect community assembly in lowland rain forests in the TSP. While species are hence not ecologically equivalent, interspecific ecological differences do not seem to affect the overall patterns of species diversity, which are mostly determined by biogeographical variables, as predicted by the neutral theory. [ABSTRACT FROM AUTHOR]

1. Changes in the frequency and intensity of disturbances are expected to occur during the coming decades as a consequence of climatic changes. Mountain forests are sensitive to climate variability, disturbances and changes in human activities; this is particularly true for subalpine forests located close to the limits of tree-growth. Here we test the role of surface fires on the structure and the dynamics of a subalpine forest compared to a control stand not affected by fire events for at least two centuries. 2. The fire events are deduced from fire scars, the age-structure from tree-ring counting, regeneration from sapling and seedling counts, necromass from the volume of woody debris, and the understorey structure from shrub and herb cover, height and biomass. Land-use history is assessed from livestock and human inventories. 3. Four surface fires occurred during the last 200 years in the burned stand. Tree density is greater in the burned stand, and, even 50 years after the last fire, burning could still be having a positive effect on regeneration density. Land-use history, mainly grazing by cattle and sheep, explains the modern forest structure through its promotion of Larix decidua. The understorey composition is the same within the two stands, suggesting a rapid recovery of dwarf shrubs ( Rhododendron ferrugineum and Vaccinium myrtillus) after the latest fire, which coincided with the final change in land-use. The exception is V. vitis-idaea cover, which is higher in the control stand. The removal of livestock in the 1940s indirectly triggered a decline in L. decidua regeneration, which was formerly promoted by grazing and trampling. Conversely, Pinus cembra seedlings have begun to establish during the last 70 years. 4. Synthesis. Expansion of forests dominated by P. cembra is expected during the 21st century, unless current global warming leads to a significant and lethal increase in fire frequency, that is, a reduction of fire-return intervals, which would reduce the number of sexually mature trees. The re-introduction of grazing could maintain the mixed subalpine forests, whereas surface fires would alter the woody debris load, promoting greater regeneration of L. decidua and P. cembra. [ABSTRACT FROM AUTHOR]

1. In severely disturbed habitats, the onset of resprouting as a persistence strategy might be problematic for tree species which do not accumulate sufficient reserves before the first disturbance event. This is due to the trade-off between the growth of reserves required to recover after disturbance and that of photosynthetic tissues. 2. In humid savannas, fire prevents trees from invading the whole landscape and nearby gallery forests have a completely different floristic composition. We test if the variations of survival during the first years of a young tree's life can explain the exclusion of forest species and the dominance pattern within savanna species. 3. Every six months for four years, we censused all seedlings and resprouts in 1 ha area of an annually burned savanna, to estimate their seasonal survival rates. We used capture–recapture statistical models to control for the probability of missing seedlings in the tall grass. 4. There were two main distinct patterns of survival among seedlings: ‘fire-responding’ species showed a 20–80% decrease in survival during the dry season, interpreted as mainly due to fire; ‘drought-responding’ species showed 20–80% variations in survival positively correlated to early-growing-season rainfall. 5. Yearly averaged survival probabilities of seedlings ranged between 0.10 and 0.63, reaching 0.850–0.996 for > 3-year-old resprouts of savanna species. Forest species showed no increase in survival with age. 6. A 4-year-survival-probability analysis showed that forest species were excluded from the savanna at the seedling stage. No parameter of the early survival curve related to the abundance of savanna species at the adult stage. 7. Synthesis. Savanna tree species follow two mutually exclusive main patterns of early survival probably related to fire and early-wet-season drought. The exclusion of forest species is consistent with a build up of reserves that is too slow due to the growth-resistance trade-off. We conclude from these findings that the use of resprouting as a persistence strategy is heavily constrained by disturbance frequency and imposes strong trade-offs on plant growth strategy. [ABSTRACT FROM AUTHOR]

1. When a plant species is introduced into a new range, it may differentiate genetically from the original populations in the home range. This genetic differentiation may influence the extent to which the invasion of the new range is successful. We tested this hypothesis by examining Senecio pterophorus, a South African shrub that was introduced into NE Spain about 40 years ago. We predicted that in the introduced range invasive populations would perform better and show greater plasticity than native populations. 2. Individuals of S. pterophorus from four Spanish (invasive) and four South African (native) populations were grown in Catalonia, Spain, in a common garden in which disturbance and water availability were manipulated. Fitness traits and several ecophysiological parameters were measured. 3. The invasive populations of S. pterophorus survived better throughout the summer drought in a disturbed (unvegetated) environment than native South African populations. This success may be attributable to the lower specific leaf area (SLA) and better water content regulation of the invasive populations in this treatment. 4. Invasive populations displayed up to three times higher relative growth rate than native populations under conditions of disturbance and non-limiting water availability. 5. The reproductive performance of the invasive populations was higher in all treatments except under the most stressful conditions (i.e. in non-watered undisturbed plots), where no plant from either population flowered. 6. The results for leaf parameters and chlorophyll fluorescence measurements suggested that the greater fitness of the invasive populations could be attributed to more favourable ecophysiological responses. 7. Synthesis. Spanish invasive populations of S. pterophorus performed better in the presence of high levels of disturbance, and displayed higher plasticity of fitness traits in response to resource availability than native South African populations. Our results suggest that genetic differentiation from source populations associated with founding may play a role in invasion success. [ABSTRACT FROM AUTHOR]

1. The diversity and structure of communities are partly determined by how species partition resource gradients. Plant size is an important indicator of species position along the vertical light gradient in the vegetation. 2. Here, we compared the size distribution of tree species in 44 Ghanaian tropical forest communities, using data from 880 one-hectare plots and over 118 000 trees belonging to more than 210 species. 3. The size distribution of forest species showed a continuous normal or log-normal distribution, with many canopy species and a few large species, and varied from community to community. Multiple regression showed that this variation is related to rainfall and to disturbance. 4. Size distributions in wet forests were less skewed than those in dry forests, with a smaller proportion of big species and a smaller size range. At the same time they exhibited tighter species packing, resulting in higher species richness. Communities with high disturbance have less species packing and lower species richness. 5. Synthesis. We conclude that the factors that constrain organism size and species coexistence in these tropical forest tree communities differ from those known to operate on a number of well-studied animal communities. [ABSTRACT FROM AUTHOR]

1. Invading species typically need to overcome multiple limiting factors simultaneously in order to become established, and understanding how such factors interact to regulate the invasion process remains a major challenge in ecology. 2. We used the invasion of marine algal communities by the seaweed Sargassum muticum as a study system to experimentally investigate the independent and interactive effects of disturbance and propagule pressure in the short term. Based on our experimental results, we parameterized an integrodifference equation model, which we used to examine how disturbances created by different benthic herbivores influence the longer term invasion success of S. muticum. 3. Our experimental results demonstrate that in this system neither disturbance nor propagule input alone was sufficient to maximize invasion success. Rather, the interaction between these processes was critical for understanding how the S. muticum invasion is regulated in the short term. 4. The model showed that both the size and spatial arrangement of herbivore disturbances had a major impact on how disturbance facilitated the invasion, by jointly determining how much space-limitation was alleviated and how readily disturbed areas could be reached by dispersing propagules. 5. Synthesis. Both the short-term experiment and the long-term model show that S. muticum invasion success is co-regulated by disturbance and propagule pressure. Our results underscore the importance of considering interactive effects when making predictions about invasion success. [ABSTRACT FROM AUTHOR]

1. Nutrient availability, defoliation and soil disturbance are important factors that influence the richness of plant communities. However, few studies have examined the interactions between these factors, especially in harsh environments. We therefore examined the effects of fertilization, defoliation and soil disturbance on plant species richness in an alpine meadow in northern Sweden. 2. From 2002 to 2005, plots were fertilized, mowed and disturbed annually in a factorially designed experiment. Plant species richness, colonization and extinction were recorded in permanent subplots. Seedling densities and recruitment from seed of Potentilla crantzii were also estimated in order to examine the mechanisms whereby these treatments influence colonization by new species. 3. Species richness peaked in the absence of disturbance in unfertilized plots and with light disturbance in fertilized plots. Colonization by new vascular plant species, seed recruitment and seedling density were all increased by soil disturbance, suggesting that colonization was increased because conditions were more favourable for seed recruitment following the disturbance treatment. Extinction of species was highest in the mowed, intensively disturbed and unfertilized plots and lowest in the fertilized, lightly disturbed and unmowed plots. 4. Local extinction was negatively correlated with both moss and vascular plant biomass. Local colonization, seedling density and recruitment of P. crantzii were all strongly negatively correlated with the biomass of mosses. In contrast, the biomass of vascular plants was only weakly correlated with local colonization, seedling density and recruitment of P. crantzii. 5. This study suggest that the level of disturbance at which species richness peaks should move towards higher disturbance levels when productivity increases. However, lower extinction rates rather then higher colonization rates seem to be causing the increase in species richness following disturbance. [ABSTRACT FROM AUTHOR]

1 Severe winds are the predominant cause of natural disturbance in temperate forests of north-eastern and north-central North America. Conceptual models of the effects of wind disturbance have traditionally focused on the impacts of catastrophic disturbances and have painted a simple picture of how disturbance acts to maintain tree species diversity. These models ignore variation among species characteristics that could have important consequences for both resistance to and recovery from disturbance. 2 We integrated an empirically parameterized, mechanistic model of windstorm mortality (WINDSTORM) and a seed-mass-based dispersal and recruitment model into a spatially explicit, individual tree model of forest dynamics (SORTIE) in order to create simulated long-term ‘experiments’ designed to explore the sensitivity of forest composition and structure to species-specific resistance to and recovery from disturbance. 3 We found that species-specific variation in resistance to wind mortality interacted strongly with: (i) shade tolerance characteristics, (ii) the medium-term history of disturbances, (iii) the long-term average severity of the disturbance regime and (iv) seedbed substrate dynamics to influence tree population dynamics and successional trajectories. 4 We also examined how local and long-distance dispersal affect response to wind disturbance. Ignoring differences among local dispersal characteristics overestimates the importance of dispersal-limited species. Our results show that long-distance immigration maintains species coexistence only if the immigration rate is very high relative to local dispersal. Despite this, stand-scale models that ignore long-distance dispersal can underestimate population dynamics of dispersal-limited species. 5 Our results indicate that landscape-scale heterogeneity in structure and species composition in these forests is facilitated by synergisms between the stochastic nature of wind disturbance and complex interactions between species traits that govern: (i) resistance to disturbance, (ii) local dispersal and seedling establishment and (iii) competitive (i.e. growth/survival) traits that do not adhere to strict tradeoffs. 6 We conclude that wind disturbance has much more complex and variable effects on long-term dynamics of forest structure and composition than suggested by previous models. In particular, non-catastrophic disturbances can generate important variation in forest dynamics that can either lead to dominance by a single or small number of species, or facilitate species coexistence. [ABSTRACT FROM AUTHOR]

1 Competition, trophic interactions and abiotic disturbances play important roles in governing plant population dynamics, yet few studies have addressed their relative contributions or interacting effects. 2 We used Life Table Response Experiment (LTRE) analysis, coupled with stochastic analyses, to examine how a major abiotic disturbance, flooding, influences the fitness and population growth of a common riparian plant, Mimulus guttatus, and how this effect compares and interacts with that exerted by herbivory. 3 We also extended LTRE analysis to include nested factors, which enabled us to examine differences across experimental sites. These spatial contributions to changes in population growth rate, λ, were compared and contrasted with those derived for year and experimental treatments. 4 Flooding had direct positive impacts on population growth, while protection from herbivory benefited plants in both flooded and non-flooded areas. Spatial variation in plant performance was also substantial, with greater variation across experimental sites than temporal variation across years. 5 Our stochastic analysis revealed that the impact of herbivores on population growth was much greater when the environment fluctuated between years with and without flooding than in more constant environments. 6 Both flooding and herbivory exerted the majority of their impacts on plant performance via changes in adult summer survival. For flooded sites, this was surprising, given the small difference in summer survival between control and herbivore-exclusion treatments, and results from the high sensitivity of population growth to adult survival. 7 The importance of herbivory in flooded sites would have not been discerned had we not considered how adult survival interacts with other stages of the M. guttatus life cycle. Thus, in order to increase ecological understanding associated with shifts in community dynamics, experimental results should be placed in a life-history context. 8 Within disturbance-driven systems, the direct abiotic effects of factors such as flooding play a critical role in determining population dynamics. However, the biotic interactions that change as a consequence of disturbance can have equal and lasting impacts on population growth. [ABSTRACT FROM AUTHOR]

1 The theories of Grime and Tilman are ambitious attempts to unify disparate theories regarding the construction of plants, their interaction with the environment and the assembly of communities. After over two decades of parallel research, their ideas have not been reconciled, hindering progress in understanding the functioning of ecosystems. 2 Grime's theories do not adequately incorporate the importance of non-heterogeneous supplies of nutrients and how these supplies are partitioned over long time scales, are inconsistent regarding the importance of disturbance in nutrient-limited habitats and need to reconsider the carbon economy of shade-tolerant plants. 3 Failure to account for differences between aquatic and terrestrial systems in how resource supplies are partitioned led Tilman to develop a shifting set of theories that have become reduced in mechanistic detail over time. The most recent highlighted the reduction of nutrient concentrations in soil solution, although it can no longer be derived from any viable mechanistic model. The slow diffusion of nutrients in soils means that the reduction of average soil solution nutrient concentrations cannot explain competitive exclusion. 4 Although neither theory, nor a union of the two, adequately characterizes the dynamics of terrestrial plant assemblages, the complementarity in their assumptions serve as an important foundation for future theory and research. 5 Reconciling the approaches of Grime and Tilman leads to six scenarios for competition for nutrients and light, with the outcome of each depending on the ability of plants to pre-empt supplies. Under uniform supplies, pulses or patches, light competition requires leaf area dominance, while nutrient competition requires root length dominance. There are still important basic questions regarding the nature of nutrient supplies that will need to be answered, but recent research brings us closer to a unified set of theories on resource competition. [ABSTRACT FROM AUTHOR]

1 Data from elevations ranging from mixed hardwood-conifer forest at 600 m to subalpineAbies balsameaforest at 1120 m indicate that canopy gaps are not static but expand over time due to mortality of trees at the gap margin and coalescence of gaps. Gap expansion is more frequent than gap initiation. Ultimately such disturbance patches may become more extensive than is normally considered as typical of gap-phase disturbance, but the processes of development are the same.2 Disturbance agents involved in gap initiation tend to differ from those involved in gap expansion. Spruce beetle, dwarf mistletoe and most root diseases predominate as agents of gap initiation, while windthrow/windsnap, chronic wind stress and Armillaria root disease are important agents of gap expansion.3 Concepts of equilibrium gap-phase dynamics and a shifting-mosaic steady state do not fully account for the dynamics of these spruce-fir forests. A spruce beetle outbreak in the late 1970s/early 1980s killed most of a cohort of dominant, emergentPicea rubens. This epidemic initiated a long-term cycle of disturbance and release that is likely to be repeated in many years when a new cohort ofP. rubensbecomes sufficiently large to sustain another major bark beetle outbreak.4 Episodic disturbance agents affect long-lived, dominant species at infrequent but regular intervals (up to hundreds of years) and operate at the landscape level. Gap-phase cycles appear to be nested within the long-term cycle. Over the long term, episodic disturbance drives such‘nested bicycle’ dynamics.5 Spatial and temporal distribution of disturbance results not only from stochastic events such as storms, but also from host specificity of agents of disturbance, their tendency to attack certain age classes of trees, local and regional contagion, and susceptibility of trees at the edge of disturbance patches.Journal of Ecology(2004) 10.1111/j.1365-2745.2004.00937.x [ABSTRACT FROM AUTHOR]

1 The environmental conditions of a site are thought to influence its invasibility by exotic plants. We tested the effects of physical disturbance, water and nutrient addition on growth and survival of a total of 28 plant species from urban bushland remnants on low fertility Hawkesbury Sandstone soils in Sydney, Australia. Species were classified as native (to Australia, including the local community) or exotic (from outside Australia) and as non-invasive or invasive.2 In a glasshouse experiment the treatments were control (natural soil), added water, added nutrients and added water and nutrients. We found significant differences in response of the plant types to additional nutrients but not to water. Under additional nutrients, exotic invasive species had better survival than all other plant types. There were strong biomass responses to added nutrients for all plant types except native non-invasives. In contrast, the survival and growth of all plant types were similar under control and additional water treatments.3 In a field experiment the factors were site (high and low nutrient soils) and physical disturbance but survival differed between plant types only in relation to site. Exotic species had much better survival than native species at the high nutrient site only. Exotic invasive species had the strongest biomass responses to the high nutrient site while native and exotic non-invasive species showed relatively smaller growth responses.4 Differences between invasive and non-invasive plants were not consistent between exotic and native species. Exotic invasives had greater survival than exotic non-invasives under high nutrient conditions in both experiments, and only exotic invasives showed consistently strong biomass responses to nutrient addition. For native species, there were no differences between invasives and non-invasives in survival in high nutrient conditions in the glasshouse or field; however, only invasive species showed a positive growth response to high nutrient conditions.5 This study provides clear evidence that the success of exotic invasive species in this low fertility vegetation community is facilitated by the addition of nutrients. It would appear that on relatively infertile (particularly phosphorus-limited) sites, invasive species cannot take advantage of additional resources provided by physical disturbance or water addition due to overwhelming nutrient-limitation. We suggest that a combination of the environmental conditions (nutrient-enrichment) and invading species having traits that allow high survival and faster growth in response to nutrients, may allow successful invasion in Hawkesbury Sandstone communities.Journal of Ecology(2004) 10.1111/j.1365-2745.2004.00938.x [ABSTRACT FROM AUTHOR]

1 Most theory and empirical research on exotic invasions is based on the assumption that problematic exotics are much more abundant in the regions where they invade than in the regions where they are native. However, the overwhelming majority of studies on exotic plants have been conducted solely within the introduced range. With few exceptions, ecologists know surprisingly little about the abundance, interaction strengths and ecosystems impacts of even the best-studied exotics in their native range.2 We argue that taking a biogeographical approach is key to understanding exotic plant invasions. On a descriptive level, unambiguous quantification of distributions and abundances of exotics in native and introduced ranges are crucial. Experiments conducted at a biogeographical scale are also necessary to elucidate the mechanisms that enable highly successful exotics to occur at substantially higher abundance in their introduced vs. native communities.3 We summarize the leading hypotheses for exotic plant success. We assert that tests of these major hypotheses for invasions (the natural enemies, evolution of invasiveness, empty niche and novel weapons hypotheses) require comparative biogeographical approaches.4 In addition to focusing on comparative work in the native and introduced range, we also suggest other approaches that could yield important insight into processes that influence exotic success.5 Increased understanding of invasions has the potential to provide unique insight into fundamental ecological theory, including that on individualistic-holistic structure, the role of trophic interactions in population regulation, and the importance of co-evolution in communities.Journal of Ecology(2004) doi: 10.1111/j.1365-2745.2004.00953.x [ABSTRACT FROM AUTHOR]

1 The invasion ofBetulaspp. represents the moment of transition between European lowland heath and scrub ecosystems. We hypothesized thatBetulainvasion was controlled by a multivariate threshold, comprising factors that may be subdivided into seed and safe-site limitations, and that phosphorus availability was a key determinant of theBetulasafe-site.2 We performed a multifactorial field experiment in which seed rain, P-availability and disturbance were manipulated. All treatments had significant effects onBetulaseedling densities, with seed availability proving the single greatest limitation. P addition emerged as having highly significant effects 4 and 12 months after germination. Disturbance had an initially large positive effect that dwindled across time.3 Detailed descriptions of seedling density data were achieved by converting two factorial variables (seed rain and P availability) to a continuous form, including numerous covariates, and producing‘minimum adequate’ generalized linear models (MAMs). These provided accurate descriptions of the data (explained deviance typically> 70%) and delimited site conditions where transition was likely.4 Seed availability remained the most important factor, but the increased number of parameters in models describing densities of more mature seedlings suggested a temporal accumulation of recruitment limitations. Statistical modelling allowed for the subdivision of disturbance effects into those associated with a reduction in vegetation densities and the remaining‘direct’ effects, e.g. soil disturbance, which shifted over time from being positive to negative. The results also support the hypothesis that soil phosphorus sorption capacity (PSC) determines heath–scrub transition as many of the identified determinants are controlled, either directly or indirectly, by PSC.5 The study demonstrates that a combination of experimental and statistical modelling approaches can provide a detailed description of the factors controlling early stage invasion and may therefore have considerable utility in ecosystem management. Although site specific, the models illuminate the mechanisms by which many larger scale processes, e.g. burning and grazing, regulate the persistence of lowland heath ecosystems.Journal of Ecology(2004)92, 868–881 [ABSTRACT FROM AUTHOR]

Summary 1 Classifying species by shared functional characteristics is important if common functional response groups are to be identified among different taxa. 2 We investigated plant traits that determine the response of forest plant species to land use changes using literature data. Sources from eight European countries and four North-eastern American states, comprising 20 field studies yielded information on 216 forest plant species. For these species, data on 13 life history traits were collected. 3 Trait correlation structure was similar in the European and American data-sets and corresponded well to those described in the literature. The European and American herbs and the European graminoids were clustered into distinct emergent groups based on their plant traits. The profiles of the European and American emergent groups were similar. 4 Herb species belonging to emergent groups characterized by low dispersability (i.e. large seeds, low fecundity, unassisted dispersal) were relatively slow colonizers. Dispersability (and not recruitment) seems to be a key factor limiting the colonization of some forest plant species. The relationship between dispersability and colonizing capacity was less clear for graminoids. 5 A life history trait-based approach offers good opportunities to gain insight into the mechanisms behind species response to land-use change. [ABSTRACT FROM AUTHOR]

Summary 1 We elucidated the critical life stages and processes in the recruitment of Rhamnus ludovici-salvatoris , a dioecious shrub endemic to the Balearic Islands (western Mediterranean), populations of which have been shrinking in recent decades. We evaluated transition probabilities between all stages involved in regeneration from pollination to seedling recruitment, in order to determine the overall probability of an ovule in a flower becoming an established individual in a population. 2 We compared populations in an oak (Quercus ilex ) forest and in a more disturbed habitat (an abandoned field). We studied seed rain and probabilities of predation, germination and survival in the main microhabitats within each community. 3 High levels of seed predation after dispersal and unfavourable conditions (water deficit) during germination and recruitment periods were the most critical factors limiting population growth in both habitats. 4 The greater fecundity of shrubs in the abandoned field did not compensate for the lower probability of ovules recruiting new individuals in that habitat compared to the forest. 5 Spatial patterns of recruitment in this species cannot be predicted from seed dispersal patterns produced by frugivorous birds. In both habitats, but especially in the forest, there was strong spatial discordance between seed rain (most seeds were deposited under conspecifics) and seedling establishment. In the forest, most established Rhamnus are found under oaks, whereas in the abandoned field, saplings and juveniles are more equally distributed across different microhabitats. 6 This empirical study supports the idea that habitat disturbance, in general, may considerably alter the patterns of plant recruitment. For endemic species with restricted and rather small populations, the loss of natural habitat is likely to be detrimental for species’ persistence, as recruitment in disturbed sites is greatly reduced. [ABSTRACT FROM AUTHOR]

Summary 1 Summer floods whose severity is affected by flooding duration, submergence depth and underwater light availability, have a large impact on the zonation of riparian plant species. 2 We analysed the range and variability of these flooding components in the River Rhine and quantified their effects on the ability of Arrhenatherum elatius , Achillea millefolium , Rumex acetosa and Rumex crispus , to survive periods of submergence under experimental conditions. 3 Survival characteristics were used to model species’ lower distribution boundaries for extreme and average floods and were compared with the current field distribution. Different light conditions were simulated by implementing three scenarios of suspended load. 4 Extreme deep Rhine floods are characterized by very low median light transmission levels (i.e. below 0.5%). The largest survival responses in the experiment were observed at such low levels (0.4–3.5 µmol m-2 s-1 ). Strong effects of light were found in R. crispus and A. millefolium , but responses were weaker in A. elatius and R. acetosa . Submergence depth also affected survival, but not as strongly as light. 5 For the flood intolerant species (A. millefolium and A. elatius ) the average flood was predicted to have little effect on field distributions under normal light conditions. However, their actual field distributions in 2000 corresponded to the predicted lower boundaries in the extreme years. This suggests that extreme years determine the distributions of these species for many years. The suspended load scenarios significantly modified the predicted lower boundaries in both extreme and average years, implying that plant lower distribution limits may be significantly shifted upwards or downwards depending on the suspended load of the river system. 6 The predicted lower boundaries of the intermediately tolerant R. acetosa and the highly tolerant R. crispus for both extreme and average years were... [ABSTRACT FROM AUTHOR]

Summary 1 Using 18 years of permanent-plot data from a 4-ha stand, we investigated whether stand dynamics is predictable, i.e. driven by competition (inferred from species shade tolerances), or unpredictable (driven by frequent exogenous disturbance or other factors). We also considered whether small disturbance might accelerate or retard succession. The study involved dynamics of stems ≥ 4.5 cm diameter at breast height (d.b.h.) for 10 important species in a southern mixed hardwood forest 80 years after selective removal of Pinus taeda. 2 Shade-tolerant species (Ilex opaca , Fagus grandifolia , Magnolia grandiflora , Acer rubrum , Nyssa sylvatica ) increased in small d.b.h. classes, whereas intermediate (Quercus alba ) and shade-intolerant species (Q. nigra , Q. hemisphaerica , Liquidambar styraciflua , Pinus taeda ) did not. 3 Per-capita ingrowth was higher for shade-tolerant species (0.016–0.024) than for intermediate and shade-intolerant species (0–0.006), whereas mortality was lower ((0.006–0.015 vs. 0.019–0.035). 4 Over 18 years, ingrowth exceeded mortality loss slightly, resulting in an increase in number of stems of about 1%, from 995 to 1029 stems ha-1 ; average live basal area (BA; 35.9 m2 ha-1 ) varied by less than 2% over eight surveys spanning 18 years. Basal area increased substantially for three species (Ilex opaca , Pinus taeda , Acer rubrum ), and declined strongly for three others (Quercus nigra , Q. hemisphaerica and Fagus grandifolia ). 5 The stand d.b.h. distribution had a rotated sigmoid form which became flatter over time. Species d.b.h. distributions were mostly bell-shaped for intolerant species, and irregular-to-monotonic declining for shade-tolerant species. Over time, bell-shaped distributions moved to the right and irregular distributions remained irregular. 6 A hurricane in 1986 caused loss of 4.5% of standing BA. Compositional change was most rapid during the... [ABSTRACT FROM AUTHOR]

Summary 1 In 1997, a major windstorm blew down over 10 000 hectares of subalpine forest in Routt National Forest in north-western Colorado. We tested whether fire history and topographic variation, across the landscape, determined subsequent susceptibility to damage from this windstorm. 2 We combined dendrochronological techniques with a geographical information system (GIS) to examine the relationship between the effects of the blowdown and the spatial heterogeneity of the vegetation. We reconstructed the spatial fire history in a c. 4400 ha area by first identifying distinct patches in the landscape on aerial photographs, and then in the field by determining the disturbance history of each patch by dating fire scars, ages of post-fire cohorts and releases of remnant trees. 3 Both topographic position and fire history contribute to susceptibility to wind damage. Stands at higher elevations, on easterly slopes and closer to ridges were most affected. Younger stands (i.e. more recently affected by stand-initiating fires) were less affected particularly in areas affected by low–moderate severity blowdown (< 80% damage). The ecological effects of the very severe 1997 windstorm were mediated by the legacies of fires which occurred several centuries ago. Interactions between natural disturbances, such as fire and blowdown, lead to synergistic effects on forest dynamics, even when disturbance is infrequent. [ABSTRACT FROM AUTHOR]

Summary 1Forest canopy gap and community dynamics were studied in a 4-ha permanent plot of an old-growth evergreen broad-leaved forest dominated by Castanopsis cuspidata var. sieboldii and Distylium racemosum in the Tatera Forest Reserve, Tsushima Islands, south-western Japan. The forest was affected by a powerful typhoon in 1987 and was monitored from 1990 to 1997. 2In 1990, all woody stems ≥ 5 cm diameter at breast height (d.b.h.) in the plot were identified, mapped and marked, and the state of 1600 5 m × 5 m contiguous quadrats used to locate canopy gaps. Gaps occupied 17.1% of the plot, which contained 4494 tree and shrub stems (total basal area 63.48 m2 ha-1 ). Gaps were re-censused in 1997 and both marked and newly recruited (≥ 5 cm d.b.h.) stems were recorded in 1992 and 1997. 3Over 7 years the rates of canopy gap formation and closure were 0.72% year-1 and 1.61% year-1 , respectively, mortality and recruitment rates were 0.97% year-1 and 0.99% year-1 , and the rates of loss and gain in basal area were 0.95% year-1 and 0.83% year-1 . 4The mortality of stems was size-dependent, with those in middle size classes having the lowest rates. Mortality of stems was lower in canopy and higher in the understorey, while the proportion of stems killed by disturbances increased with height. 5Stems that died during the 7 years were predominantly located in newly created gaps, whereas stems were recruited into both established and new gaps. Deciduous broad-leaved species were largely restricted to gaps that remained open throughout the study. 6Both composition and structure of the forest changed in response to disturbance-related effects on canopy dynamics. [ABSTRACT FROM AUTHOR]

Summary 1 In order to investigate the use of plant functional types as an alternative to floristic descriptions of response to grazing, we analysed plant communities from a cattle grazing experiment conducted in grassy eucalypt woodland in subtropical Queensland, Australia. The two variables analysed (landscape position and stocking rate) accounted for similar proportions of variation in the vegetation ground layer, although forbs were more sensitive to slope position and perennial grasses were more sensitive to stocking rate. 2 As grazing pressure increased, perennial grasses declined, while the relative proportion of forbs and annual grasses increased. Detailed functional group analyses were conducted for the perennial grass and forb life-forms. Annual grasses were represented by only two species, preventing identification of functional types within this life-form. 3 We conducted a five-step analysis for both perennial grasses and forbs as follows: (i) defining grazing-related species response groups; (ii) defining species groups based on natural attribute correlations; (iii) identifying attributes that changed significantly with grazing; (iv) identifying syndromes by relating (ii) and (iii); (v) describing functional types from (iii) and (iv), and assessing them against actual species response. 4 Eight grass and eight forb functional types were identified. Of the taxa that had an observed response to grazing, 54% of the grass taxa and 57% of the forb taxa corresponded to one of these functional types in terms of meeting both grazing response and trait criteria. The five-stage analysis provided a comprehensive but complex approach to functional type identification. 5 The functional types identified can be summarized as follows. Low levels of grazing were associated with more medium-sized, moderately leafy perennial grasses with wind-dispersed or adhesive seeds, and more erect or twining forbs with large to medium sized seeds. High levels of grazing were... [ABSTRACT FROM AUTHOR]

1 Using the data in a recently published seed bank database for north-west Europe, we describe how a species’ seed bank behaviour can be characterized by a single ‘longevity index’, and investigate how representative the information in the database is of the north-west European flora. We also test the hypotheses that seeds of short-lived species are more persistent than those of long-lived species, and long-lived seeds are characteristic of species living in disturbed habitats. 2 The data are not representative of the north-west European flora as a whole; they are a fair reflection of a research effort that has been largely directed towards grassland and arable weeds. Data for rare species, non-agricultural habitats in general and wetlands, rocky habitats and native woodland in particular, are scarce or absent. 3 Annuals and biennials almost always have more persistent seeds than related perennials, and this difference is most striking when, as in Anagallis arvensis and Aphanes arvensis, the short-lived species have moved well away from the ‘core’ habitat of the family. Confamilial monocarps and polycarps do not differ consistently in seed mass. 4 Gradients of habitat disturbance are accompanied by predictable changes in seed persistence, which are themselves often (but not always) accompanied by parallel shifts in seed size. These results suggest that increasing habitat disturbance (i.e. increasing density-independent mortality) always selects for increased seed persistence, confirming both theory and previous analyses. However, increased seed persistence is not always associated with reduced seed size. This is because persistence depends not only on seed size, but on other traits, many of them physiological. In many habitats the probability of seed burial is strongly linked to seed size and shape, but in arable habitats cultural practices have broken this link. [ABSTRACT FROM AUTHOR]