Mechanisms of succession on fallow lands

Vegetation changes during succession can be regarded as plant-to-plant replacement processes. For deeper insight into the nature of these process we need to investigate the mechanisms involved. Therefore two experiments with herbaceous plant communities were analyzed. The data confirm the view that all three types of interaction: competition, coexistence by niche separation, and cooperation, act together. Likewise it can be concluded that the three models of succession proposed by Connell & Slatyer (1977) are not exclusive but describe mechanisms acting together in the same succession process. Evidence is given that seasonal events can act like a switch and influence the successional trend at a later time. It is, therefore, not meaningful to differentiate between fluctuations in the sense of yearly oscillations and the successional trend itself.Dedicated to Prof. Dr Dr h.c. Heinrich Walter on the occasion of the 90th anniversary of his birthday.     

Models,mechanisms and pathways of succession

The study of succession has been hampered by the lack of a general theory. This is illustrated by confusion over basic concepts and inadequacy of certain models. This review clarifies the basic ideas of pathway, mechanism, and model in succession. Second, in order to prevent inappropriate narrowness in successional studies, we analyze the mechanistic adequacy of the most widely cited models of succession, those of Connell and Slatyer. This analysis shows that models involving a single pathway or a dominant mechanism cannot be treated as alternative, testable hypotheses. Our review shows much more mechanistic richness than allowed by these widely cited models of succession. Classification of the mechanisms of specific replacement, called for by existing models, is problematic and less valuable than the search for the actual mechanisms of particular seres. For example, the “tolerance” mechanism of succession has at least two contrasting meanings and is unlikely to be disentangled from the “inhibition” mechanism in field experiments. However, the understanding of particular species replacements through experiment and knowledge of the conditions of a particular sere and species life histories is a reasonable and desirable goal. Finally, we suggest the need for a broad mechanistic concept of succession. Thus, based on classical causes of succession that have survived recent scrutiny, we erect a framework of successional mechanisms. This framework aims at comprehensiveness, and specific mechanisms are nested within more general causes. As a result of its breadth and hierarchical structure, the framework performs two important functions: First, it provides a context for studies at specific sites and, second, is a scheme for formulating general and testable hypotheses. The review of specific successional mechanisms and the general mechanistic framework can together guide future work on succession, and may foment the development of a broad theory.     

Plant strategies and secondary succession on Brittany heathlands after severe fire

Abstract. Plant succession on heathlands subjected to major fire disturbance and humus burn in 1976 was studied over twelve years following burning. Life history strategies of principal heathland species are described with reference to concepts outlined by Grime (1979) and Whittaker & Goodman (1979). Heathlands and closely related communities are characterised by dominance of speciestolerant of physical stress (‘S’ strategists) whereas species which colonise disturbed sites are closer to rude-rals (‘R’ strategists). After severe burning three main successional patterns were identified. They depend on water and nutrient availability relative to temporal population dynamics. Recovery of heathland is often retarded due to monospecific dominance, e.g. of Polytrichum commune, Molinia caerulea and Betula pubescens. These patterns of secondary succession illustrate the inhibition model advanced by Connell & Slatyer (1977).     

The influence of patch demographics on metapopulations, with particular reference to successional landscapes

The classical view of metapopulations relates the regional abundance of a species to the balance between the extinction and colonization dynamics of identical local populations. Species in successional landscapes may represent the most appropriate examples of classical metapopulations. However, Levins‐type metapopulation models do not explicitly separate population loss due to successional habitat change from other causes of extinction. A further complication is that the chance of population loss due to successional habitat change may be related to the age of a patch. I developed simple patch occupancy models to include succession and included consideration of patch age structure to address two related questions: what are the implications of changes in patch demographic rates and when is a move to a structured patch occupancy model justified? Age‐related variation in patch demography could increase or decrease the equilibrium fraction of the available habitat occupied by a species when compared to the predictions of an unstructured model. Metapopulation persistence was enhanced when the age class of patches with the highest species occupancy suffered relatively low losses to habitat succession. Conversely, when the age class of patches with the highest species occupancy also had relatively high successional loss rates, extinction thresholds were higher that would be predicted by a simple unstructured model. Hence age‐related variation in patch successional rate introduces biases into the predictions of simple unstructured models. Such biases can be detected from field surveys of the fraction of occupied and unoccupied patches in each age class. Where a bias is demonstrated, unstructured models will not be adequate for making predictions about the effects of changing parameters on metapopulation size. Thinking in successional terms emphasizes how landscapes might be managed to enhance or reduce the patch occupancy by any particular metapopulation     

The interaction between nutrient availability and disturbance frequency on the diversity of benthic marine communities on the north-east coast of England

1. Several theoretical models predict under what conditions maximum species diversity can be maintained, and they are often used to develop effective ecosystem management plans. 2. Two models that are currently used to predict patterns of species diversity were empirically tested in marine subtidal benthic communities of different successional stages. 3. The two models were: the interactive effects of nutrient availability and disturbance frequency proposed by Kondoh (2001; Proceedings of the Royal Society London B, 268, 269-271), and the intermediate disturbance hypothesis (IDH) proposed by Connell (1978; Science, 199, 1302-1310). 4. Interactive effects were found to be transient and only occurred in the older communities, while the unimodal pattern suggested by the IDH was not supported in either successional stage. 5. It is concluded that these models are very general and thus lack sufficient explanatory power. Both models require a number of specific prerequisites for maximum diversity to be found, and though applicable in many different ecosystems they need to be refined as tools in order that they can be effectively used in habitat management plans.     

Primary succession of Bistorta vivipara (L.) Delabre (Polygonaceae) root‐associated fungi mirrors plant succession in two glacial chronosequences

Glacier chronosequences are important sites for primary succession studies and have yielded well‐defined primary succession models for plants that identify environmental resistance as an important determinant of the successional trajectory. Whether plant‐associated fungal communities follow those same successional trajectories and also respond to environmental resistance is an open question. In this study, 454 amplicon pyrosequencing was used to compare the root‐associated fungal communities of the ectomycorrhizal (ECM) herb Bistorta vivipara along two primary succession gradients with different environmental resistance (alpine versus arctic) and different successional trajectories in the vascular plant communities (directional replacement versus directional non‐replacement). At both sites, the root‐associated fungal communities were dominated by ECM basidiomycetes and community composition shifted with increasing time since deglaciation. However, the fungal community's successional trajectory mirrored the pattern observed in the surrounding plant community at both sites: the alpine site displayed a directional‐replacement successional trajectory, and the arctic site displayed a directional‐non‐replacement successional trajectory. This suggests that, like in plant communities, environmental resistance is key in determining succession patterns in root‐associated fungi. The need for further replicated study, including in other host species, is emphasized.     

植物群落演替过程中植物生理生态学特性及其主要环境因子的变化

对20世纪80年代以来有关植物群落演替的生理生态学机制研究的主要结果进行了综述.演替早期和演替后期各种植物所处环境常有很大差别.演替早期的生境具有开放性和光照充足等特点,各环境因子富于变化;演替后期的生境由于植被的缓冲作用,一般较为封闭和稳定,各环境因子在空间尺度上的异质性较强.演替早期和演替后期群落不仅物种组成不同,而且在演替不同阶段中出现的物种的生理生态特性以及对环境的适应性也有很大差别,这些物种的生理生态差异使得物种更替现象经常发生, 也使得演替能够顺利进行.在全球气候变化影响下,生态系统将会出现更多的次生演替和长时间停留于演替早期阶段的情况.     

Patterns and mechanisms of plant succession after fire on Artemisia-grass sites in southeastern Idaho

Cover data for plant species on eight environmentally similar sites that were each burned in a different year (from 2 to 36 years ago) were used to construct a composite sequence of vegetational change after fire on Artemisia-grassland sites in southeastern Idaho. Some species were early successional such as Lithospermum ruderale, and some late successional: Artemisia tridentata, A. tripartita, and Gutierreza sarothrae. But many species: Purshia tridentata, Symphoricarpos oreophilus, Amelanchier alnifolia, Chrysothamnus viscidiflorus, Achillea millefolium, Agropyron dasystachyum, and A. spicatum were present in both early and later stages. Shannon and Simpson indices of diversity and species richness indicated little change in alpha diversity through time. This was attributed mainly to the limited change in species composition from early to later stages. The general pattern of succession is compatible with the tolerance model of Connell & Slatyer (1977) in most respects. Species traits relating to persistence through a disturbance or re-establishment on the site, and tolerance of competition shape the course of succession on a site. Perennial grasses and forbs which sprout from the base after fire are the first species to dominate the sites. Sprouting shrubs, which require some years to regrow to their pre-fire form, are prominent by the sixth year. Shrubs which rely on dispersal become co-dominants in later stages, at which time some herbaceous species are reduced oreliminated. The pattern of succession can differ due to presence or absence of species with particular traits.     

Heterotrophic succession within dung-inhabiting beetle communities in northern Spain

Successional patterns of beetles inhabiting dung pats were examined during May and July 1993 in a mountain area in northern Spain (Picos de Europa). Beetles belonging to six families were caught during the course of succession (30 d). Coprophagous beetles were more abundant in dung pats than predatory beetles (89 and 11 %, respectively). A trophic sequence was observed in relation to age of the dung, coprophagous beetles occurring earlier in the dung than predatory beetles. The pattern was observed on two occasions during the season, though succession proceeded somewhat faster in July than in May. These results suggest that food availability and microclimatic conditions in dung pats appear to determine the successional occurrence of beetle taxa. On the other hand, coprophagous species (Aphodius) were poorly segregated along the successional axis. Null models failed to support the hypothesis that successional overlap and differences in successional mean occurrence between species could be the result of competition. Successional patterns at the specific level probably reflect differences in behaviour, such as pat location, feeding, mating, egg-laying and larva requirements, rather than competitive replacement.     

Whole-canopy nitrogen-use efficiency of pioneer species in early secondary forest succession in Vietnam

The size hierarchy among plants during forest succession can be influenced by differences in nitrogen-use efficiency (NUE). During succession, soil nitrogen availability decreases, which increases the importance for species to use nitrogen efficiently. We compare whole-canopy-NUE and its underlying traits among pioneer species in a tropical forest over the first years of succession. At the leaf level, potential photosynthetic NUE (PPNUE: light-saturated photosynthetic rate/leaf N content) was partly positively correlated with species growth rate but not to species height. Canopy-NUE differed two-fold among species. The species with the highest PPNUE and growth rate but with a small stature had a high canopy-NUE and the tallest species had a low canopy-NUE. Differences in canopy-NUE appeared to be largely determined by leaf life span (LLS) and nitrogen resorption. A high LLS or a high resorption resulted in a high mean residence time of nitrogen and thus a high canopy-NUE. Canopy-NUE of a species was different between successional stands that differed in age and thus in height, leaf-area index, and resource availability. Thus, an increase in competitive pressure with succession did cause some changes in the use of nitrogen, except for one species. Species that are generally considered part of the same functional group (pioneer trees) can differ considerably in NUE and its underlying traits.     

Rate of succession in restored wetlands and the role of site context

Question: Are changes in plant species composition, functional group composition and rates of species turnover consistent among early successional wetlands, and what is the role of landscape context in determining the rate of succession? Location: Twenty‐four restored wetlands in Illinois, USA. Methods: We use 4 years of vegetation sampling data from each site to describe successional trends and rates of species turnover in wetlands. We quantify: (1) the rate at which composition changes from early‐successional to late‐successional species and functional groups, as indicated by site movement in ordination space over time, and (2) the rate of change in the colonization and local extinction of individual species. We correlate the pace of succession to site area, isolation and surrounding land cover. Results: Some commonalities in successional trends were evident among sites. Annual species were replaced by clonal perennials, and colonization rates declined over time. However, differences among sites outweighed site age in determining species composition, and the pace of succession was influenced by a site's landscape setting. Rates of species turnover were higher in smaller wetlands. In addition, wetlands in agricultural landscapes underwent succession more rapidly, as indicated by a rapid increase in dominance by late‐successional plants. Conclusions: Although the outcome of plant community succession in restored wetlands was somewhat predictable, species composition and the pace of succession varied among sites. The ability of restoration practitioners to accelerate succession through active manipulation may be contingent upon landscape context.     

Nestedness and successional trajectories of macroinvertebrate assemblages in man-made wetlands

Current successional models, primarily those based on floral succession, propose several distinct trajectories based on the integration of two key hypotheses from succession theory: convergence versus divergence in species composition among successional sites, and progression towards versus deviation from a desired reference state. We applied this framework to faunal succession, including differential colonization between active and passive dispersers, and the nested patterns generated as a consequence of this peculiarity. Nine man-made wetlands located in three different areas, from 0–3 years from wetland creation, were assessed. In addition, 91 wetlands distributed throughout the region were used as references for natural macroinvertebrate communities. We predicted the following: (1) highly nested structures in pioneering assemblages will decrease to lower mid-term values due to a shift from active pioneering taxa to passive disperser ones; (2) passive idiosyncratic taxa will elicit divergent successional trajectories among areas; (3) the divergent trajectories will provoke lower local and higher regional diversity values in the mid-term assemblages than in pioneer assemblages. Our results were largely congruent with hypotheses (1) and (2), diverging from the anticipated patterns only in the case of the temporary wetlands area. However, overall diversity trends based on hypothesis (3) did not follow the expected pattern. The divergent successional trajectories did not compensate for regional biodiversity losses that occurred as a consequence of pioneering colonizer decline over time. Consequently, we suggest reconsidering wetland construction for mitigation purposes within mid-term time frames (≤3 years). Wetlands may not offset, within this temporal scenario, regional biodiversity loss because the ecosystem may not support idiosyncratic taxa from natural wetlands.     

Understanding ecological community succession: Causal models and theories,a review

Critical review of explanations for patterns of natural succession suggests a strong, common basis for theoretical understanding, but also suggests that several well known models are incomplete as explanations of succession. A universal, general cause for succession is unlikely, since numerous aspects of historical and environmental circumstances will impinge on the process in a unique manner. However, after disturbance, occupation of a site by any species causes changes in the conditions at the site. Sorting of species may result, since different species are adapted to different regions of environmental gradients. Such sorting can generate several patterns of species abundance in time, but commonly results in sequential replacements of species adapted to the varying conditions. This may be due to constraints on species' strategies, or life history traits, placed by the limited resources available to the organism. These constraints often result in inverse correlation between traits which confer success during early and late stages of succession. Facilitatory or inhibitory effects of species on each other are best understood in terms of these life history interactions, perhaps as restrictions on, or as moderation of, these processes.Strong support for the importance of correlations in life history traits stems from comparisons of simulated succession with and without these correlations. These simulations are reviewed in some detail, and followed by brief reviews of other prominent models for succession. Several aspects of the confusion and controversies in the successional literature are then discussed, with a view to a more optimistic synthesis and direction for successional ecology.     

Phyllostomid bat assemblages in different successional stages of tropical rain forest in Chiapas,Mexico

Due to their role in seed dispersal, changes in the community of phyllostomid bats have direct consequences on ecological succession. The objective of this work was to document changes in the structure of bat assemblages among secondary successional stages of tropical rain forest in Chiapas, Mexico. Bats were mist-netted at ground level during 18 months in 10 sites belonging to 3 successional stages: four sites represented early succession (2–8 years of abandonment), four intermediate succession (10–20 years of abandonment), and two late succession (mature old-growth forest).We captured 1,179 phyllostomids comprising 29 species. Phyllostomid species richness was 17 (58% of all species) in the early stage, 18 (62%) in the intermediate stage and 24 (83%) in the late stage. The late successional mature forest possessed nine species that were exclusively found there, whereas early and intermediate successional stages contained only one exclusive species. Sturnira lilium, Artibeus lituratus, Carollia perpicillata, Artibeus jamaicensis and Glossophaga soricina represented 88% of all captured phyllostomid bats. Frugivores made up more than 90% of the species captured in early and intermediate successional stages and 84% in late successional forest. The Bray–Curtis index of dissimilarity showed a replacement of species through successional stages with the largest dissimilarity between early and late stages, followed by intermediate and late, and the lowest dissimilarity between early and intermediate stages. The number of gleaning insectivore species increased during succession. The carnivorous guild was exclusively found in the late stage (three species). We conclude that the late successional mature forest was the main reservoir for the gleaning insectivore and carnivore guilds; however, early and intermediate successional stages possessed a great diversity of species including many frugivores.     

Successional theories

Succession is a fundamental concept in ecology because it indicates how species populations, communities, and ecosystems change over time on new substrate or after a disturbance. A mechanistic understanding of succession is needed to predict how ecosystems will respond to land-use change and to design effective ecosystem restoration strategies. Yet, despite a century of conceptual advances a comprehensive successional theory is lacking. Here we provide an overview of 19 successional theories (‘models’) and their key points, group them based on conceptual similarity, explain conceptual development in successional ideas and provide suggestions how to move forward. Four groups of models can be recognised. The first group (patch & plants) focuses on plants at the patch level and consists of three subgroups that originated in the early 20th century. One subgroup focuses on the processes (dispersal, establishment, and performance) that operate sequentially during succession. Another subgroup emphasises individualistic species responses during succession, and how this is driven by species traits. A last subgroup focuses on how vegetation structure and underlying demographic processes change during succession. A second group of models (ecosystems) provides a more holistic view of succession by considering the ecosystem, its biota, interactions, diversity, and ecosystem structure and processes. The third group (landscape) considers a larger spatial scale and includes the effect of the surrounding landscape matrix on succession as the distance to neighbouring vegetation patches determines the potential for seed dispersal, and the quality of the neighbouring patches determines the abundance and composition of seed sources and biotic dispersal vectors. A fourth group (socio-ecological systems) includes the human component by focusing on socio-ecological systems where management practices have long-lasting legacies on successional pathways and where regrowing vegetations deliver a range of ecosystem services to local and global stakeholders. The four groups of models differ in spatial scale (patch, landscape) or organisational level (plant species, ecosystem, socio-ecological system), increase in scale and scope, and reflect the increasingly broader perspective on succession over time. They coincide approximately with four periods that reflect the prevailing view of succession of that time, although all views still coexist. The four successional views are: succession of plants (from 1910 onwards) where succession was seen through the lens of species replacement; succession of communities and ecosystems (from 1965 onwards) when there was a more holistic view of succession; succession in landscapes (from 2000 onwards) when it was realised that the structure and composition of landscapes strongly impact successional pathways, and increased remote-sensing technology allowed for a better quantification of the landscape context; and succession with people (from 2015 onwards) when it was realised that people and societal drivers have strong effects on successional pathways, that ecosystem processes and services are important for human well-being, and that restoration is most successful when it is done by and for local people. Our review suggests that the hierarchical successional framework of Pickett is the best starting point to move forward as this framework already includes several factors, and because it is flexible, enabling application to different systems. The framework focuses mainly on species replacement and could be improved by focusing on succession occurring at different hierarchical scales (population, community, ecosystem, socio-ecological system), and by integrating it with more recent developments and other successional models: by considering different spatial scales (landscape, region), temporal scales (ecosystem processes occurring over centuries, and evolution), and by taking the effects of the surrounding landscape (landscape integrity and composition, the disperser community) and societal factors (previous and current land-use intensity) into account. Such a new, comprehensive framework could be tested using a combination of empirical research, experiments, process-based modelling and novel tools. Applying the framework to seres across broadscale environmental and disturbance gradients allows a better insight into what successional processes matter and under what conditions.     

Temporal variation in the influence of forest succession on caterpillar communities: A long‐term study in a tropical dry forest

Forest succession can influence herbivore communities through changes in host availability, plant quality, microclimate, canopy structure complexity and predator abundance. It is not well known, however, if such influence is constant across years. Caterpillars have been reported to be particularly susceptible to changes in plant community composition across forest succession, as most species are specialists and rely on the presence of their hosts. Nevertheless, in the case of tropical dry forests, plant species have less defined successional boundaries than tropical wet forests, and hence herbivore communities should be able to persist across different successional stages. To test this prediction, caterpillar communities were surveyed during eight consecutive years in a tropical dry forest in four replicated successional stages in Chamela, Jalisco and Mexico. Lepidopteran species richness and diversity were equivalent in mature forests and early successional stages, but a distinctive caterpillar community was found for the recently abandoned pastures. Species composition tended to converge among all four successional stages during the span of eight years. Overall, our results highlight the importance of both primary and secondary forest for the conservation of caterpillar biodiversity at a landscape level. We also highlight the relevance of long‐term studies when assessing the influence of forest succession to account for across year variation in species interactions and climatic factors. Abstract in French is available with online material.     

Mathematical modelling of ecological succesion—a review

The present review gives an account of the applicability of mathematical modelling in ecological succession studies. The ability of particular model types to solve problems of both theory and management is discussed. The Markovian models are found to be useful for short term predictions, but of very limited value for theoretical considerations. Finally, the predictability of successional pathways is discussed. It is argued that the less we understand about processes in vegetation dynamics, the more we will see the course of succession as random and unpredictable.     

Early development of subtidal macrofaunal assemblages: relationships to period and timing of colonization

Colonization and successional development of very diverse subtidal assemblages on rocky surfaces are not clearly understood. Artificial units of habitat (AUHs) made of nylon pot-scourers were used to test predictions from various models of succession. An experiment was designed in an attempt to unconfound the period of deployment (equals age of succession) from the time-period during which AUHs were deployed. AUHs were deployed in two sites, 100 m apart, for 1 month, starting at 0, 1, 2 and 3 months, for 2 months, starting 0 and 2 months and for 4 months from 0 month. Ninety-nine taxa were recorded in the AUHs. Successional change was not due to nett accumulation of taxa, nor simply to longer-term AUHs sampling successive different periods of time. Assemblages developing over the same period were different, but only a small amount of the variability was seasonal. Assemblages converged as period of deployment increased. There was less change from one to two months than from two to four months in the development of assemblages, but some of this was due to seasonal difference between the first and last two months. There were no differences between sites in any of the analyses of structure of assemblages. Few individual taxa showed consistent patterns of changing abundance with length of deployment. Different types of organisms showed markedly different patterns of arrival. The increase in number of species of gastropods was much smaller than the corresponding increase in number of taxa of polychaetes. Succession in these assemblages is complex and variable, but shows some repeated patterns. Fitting these to models of succession is only partially successful and new models are needed for very diverse assemblages.     

On the dynamics of vegetation: Patterns of environmental and vegetational change

Summary Ecological succession theory deals with temporal change in biological communities. It consists largely of generalizations based on temporal sequences inferred from spatial ones. The predictive content of the theory is low, since predictions are derived from unconditional trends rather than conditional laws. There exist several conflicting theories purporting to explain successional change, but their empirical vacuousness prevents an assessment on empirical terms. It is argued here that one can nevertheless advocate a theory which accounts for the ubiquity of successional change and explains the most conspicuous characteristics of the successional process, even though it cannot predict the detailed dynamics. Such a theory is derived here from an analysis of adaptive strategies.It is also pointed out that a persistant confusion exists in the ecological literature between what are considered to be the driving forces of successional change, competition and reaction. The former is taken to be an instantaneous type of interaction, whereas the latter has historical (cumulative) aspects. It is not at all obvious whether interactions of the historical type play an important role in driving vegetational change, although it is usually suggested that they do.     

Early gap successional pathways in a Fagus-Acer forest preserve: pattern and determinants

Abstract. Many theories of forest succession imply that terrestrial plant community composition within a region tends to converge toward a climax community. That is, given similar climatic and edaphic conditions, succession at different sites within an area will lead to comparable species compositions, a pattern referred to as successional convergence. In this study, we examine changes in plant composition within forest canopy gaps over a 17-yr period to identify potential patterns of successional convergence and to ascertain the factors controlling the successional pathway. To do so, we: (1) sampled 36 forest canopy gaps in Hueston Woods Nature Preserve in 1977, 1981, 1985, 1989 and 1993, (2) evaluated changes in the similarity of gap composition over this period, and (3) examined gap composition in each year as a function of variables describing gap habitat, seed source proximity, and disturbance history. Results indicated an initial pattern of successional divergence, with gaps exhibiting increased dissimilarity over the first 10–12 years of succession. We attribute this initial period of divergence to the effects of differential seed inputs from edge individuals and heterogeneity of available light due to differences in gap size. Recent surveys, however, indicated that gap composition has become more similar as competition within gaps has become more intense. In these samples, gap composition is closely linked to site conditions, including slope, soil conditions, and site exposure. Finally, while these patterns may suggest equilibrium-oriented dynamics, non-equilibrium processes such as repeat disturbances are also evident at Hueston Woods and will likely play an important role in determining future successional pathways.