Plant succession is the process by which the mix of species in a given area changes over time in a roughly directional way, with early-arriving plants gradually giving way to later ones until the community reaches a relatively stable state. A bare patch of volcanic rock, an abandoned farm field, or a patch of forest leveled by wildfire will all, if left alone, go through a recognizable sequence of plant turnover. The process can take decades to centuries, and it involves far more than just which seeds land first. Underground fungal networks, soil chemistry, seed banks buried in the dirt, the feeding habits of insects and grazing mammals, and even the fruit traits of individual tree species all steer where succession goes and how fast it gets there.
Primary and Secondary Succession
Ecologists split succession into two broad categories based on starting conditions. Primary succession begins on surfaces that have never supported plant life or where all biological material has been wiped clean: fresh lava flows, newly exposed rock after a glacier retreats, or sand dunes that have just formed. There is no soil to speak of, no seed bank waiting underground, and no root fragments ready to resprout. Everything has to arrive from scratch.
Secondary succession starts from a more forgiving baseline. After a fire, a logged forest, or a plowed field is abandoned, the soil is still there, seeds are already buried in it, and root systems may still be alive. Recovery tends to be much faster because the biological infrastructure is partly intact. Research on heathland soils in southeastern Australia, for example, found that the seed bank exerts a strong influence on which species show up after a fire, with different species varying in how long their seeds persist underground. That buried reservoir of seeds essentially pre-loads the recovery trajectory before the first visible sprout appears.
1Plant Ecology. Soil seed bank dynamics in post-fire heathland succession in south-eastern AustraliaThe distinction matters in practical terms. A restoration project on a former mine site with no topsoil is dealing with primary succession conditions and will need far more intervention than one on an abandoned pasture where the soil seed bank is intact.
The Classic Sequence on Bare Ground
Primary succession on glacial forefields offers some of the clearest real-world examples because the glacier’s retreat exposes rock surfaces of known age. In subalpine forests following glacial retreat, researchers have tracked how mosses colonize early, with cover and biomass starting low on the freshest surfaces, then climbing steeply. One study on a glacier forefront found moss cover peaked at about 79% in an early stage, then dropped sharply before rising again to roughly 93% at a later stage as the forest canopy matured.
2PubMed Central. Canopy‐Mediated Dynamics of Moss Communities in Primary Succession: Coupling of N₂‐Fixation and Biomass Accumulation in Subalpine Forests Following Glacial RetreatThat non-linear pattern, a rise followed by a crash followed by another rise, reflects something important. Succession is not a smooth escalator from bare rock to mature forest. As the canopy opens and closes through different stages, the species underneath boom and bust in response. Mosses, for instance, thrive in early light-rich conditions, get shaded out as shrubs and young trees establish, then recover later when a mature canopy creates the cool, moist conditions they prefer.
How Species Replace Each Other
One of the oldest questions in ecology is why early species eventually lose their foothold. Three broad mechanisms have been debated since the 1970s. In facilitation, early arrivals improve conditions for later species, for example by building soil or fixing nitrogen, essentially engineering their own replacement. In tolerance, later species simply cope better with declining resources like light or nutrients. In inhibition, established species actively resist newcomers, and it takes a disturbance or the death of the incumbent to open space.
Real communities tend to involve all three processes at once, and their relative strength shifts depending on species richness and density. Experimental work testing these classic models found that increasing the richness of early colonists actually inhibited succession, but only when initial abundance was high, likely because a dense, diverse mat of early species formed an impenetrable barrier to new arrivals. In contrast, increasing the abundance of early colonists at low richness tended to facilitate succession, because a few dominant early species modified the habitat in ways that helped latecomers.
3PubMed Central. Connell and Slatyer’s models of succession in the biodiversity eraThis means the answer to “what drives succession” depends on who is already there. A monoculture of one pioneer grass may facilitate the next wave of plants. A rich, packed assemblage of many pioneer species may lock the system in place for years.
Shade Tolerance and the Forest Example
In temperate forests, one of the most visible engines of succession is shade tolerance. Pioneer tree species like birches, aspens, and pines need full sunlight to germinate and grow. They colonize gaps quickly but produce seedlings that cannot survive under their own canopy. Shade-tolerant species like hemlocks, beeches, and maples germinate in dim conditions and slowly grow up beneath the pioneers. Over decades to centuries, the shade-tolerant trees overtop the pioneers, which die without replacement.
Analysis of forest inventory data across the United States has confirmed that shade-tolerance-driven succession operates as a primary factor in forest dynamics, particularly in the central-north and northeastern regions. The study also linked the strength of this process to climatic variables, meaning that shade-tolerance succession is not equally powerful everywhere; in drier or more fire-prone regions, disturbances interrupt the process before shade-tolerant species can take over.
4PubMed Central. An appraisal of the classic forest succession paradigm with the shade tolerance indexWhat Happens Underground
Succession is not just about what you can see aboveground. The soil beneath a recovering landscape undergoes its own transformation, and the organisms living in it play a surprisingly active role in determining which plants succeed.
Mycorrhizal fungi, the fungi that form partnerships with plant roots and help them absorb water and nutrients, follow their own successional arc. On a glacier forefront studied in the Alps, plants that lacked mycorrhizal partnerships dominated the youngest, most recently exposed sites, while the proportion of mycorrhizal plants increased steadily as the community aged.
5PubMed Central. Mycorrhiza-plant colonization patterns on a subalpine glacier forefront as a model system of primary successionThis pattern makes intuitive sense. The earliest colonizers of bare rock have to be self-sufficient because the fungal networks do not exist yet. But as soil develops and fungal communities establish, plants that can partner with mycorrhizae gain a competitive edge, drawing more nutrients from the growing soil. Over time, the fungal community itself diversifies, with different genera of fungi replacing each other in a sequence that parallels the plant turnover happening above. On contaminated or degraded soils, restoration projects have found that fungal diversity increases alongside plant diversity during recovery, with small-spored fungal genera giving way to larger-spored ones as conditions improve.
6PubMed Central. Review: roles of mycorrhizal symbioses and associated soil microbiomes in ecological restorationAnimals as Successional Drivers
Plants do not go through succession in a vacuum. The animals eating, trampling, and dispersing them shape the trajectory at every stage.
Insect herbivores can redirect succession by selectively weakening certain plant species, altering the competitive balance and effectively picking winners.
7Journal of Ecology. Long‐term impacts of insect herbivores on plant populations and communities A beetle that preferentially feeds on a dominant shrub, for example, can open space for species that would otherwise be outcompeted. Mammalian grazers have similar effects. In a study of grey-dune communities, plots exposed to herbivory by mammals had lower aboveground plant mass because of defoliation, but higher species richness and diversity. Grazing knocked back the dominant species enough to let rarer plants gain a foothold, including a threatened species that benefited specifically from the disturbance herbivores created.8Journal of Vegetation Science. Mammalian herbivory alters structure, composition and edaphic conditions of a grey‐dune community
Seed dispersal by birds and bats also plays a direct role, especially in tropical landscapes. Research on deforested tropical land found that the fruit traits of pioneer trees strongly influenced which bird species visited and how many seeds they dropped. Plots planted with pioneer trees bearing carbohydrate-rich fruits attracted more than twice the species richness and density of birds and seeds compared to plots with lipid-rich pioneers, and outperformed wind-dispersed pioneers by over 80%.
9Journal of Applied Ecology. Fruit traits of pioneer trees structure seed dispersal across distances on tropical deforested landscapes: Implications for restorationIn other words, which pioneer tree you plant in a restoration project can determine the entire community of birds that shows up, and therefore which seeds they carry in from the surrounding landscape. The choice of the first tree ripples forward through decades of succession.
When Succession Gets Stuck or Goes Sideways
The textbook image of succession as a smooth march toward a mature “climax” community is a simplification. Real landscapes frequently stall, loop, or veer into entirely unexpected states.
Invasive species are one of the most common causes of derailment. When non-native plants colonize a recovering site, they can alter soil chemistry, shade out native seedlings, or monopolize pollinator attention so thoroughly that the native successional pathway is blocked. Research on heavily invaded ecosystems has shown that invasive species can push a site into an alternate stable state, a self-reinforcing community where further change toward the native trajectory is unlikely without active management intervention.
10Forest Ecology and Management. Facilitating natural succession in a heavily invaded ecosystemAlternate stable states also occur without invasive species. In the Serengeti–Mara ecosystem, grasslands and woodlands exist as two self-reinforcing states on the same landscape. Both are stable, and the system can flip between them depending on rainfall and fire frequency rather than following a single linear path.
11Global Ecology and Biogeography. Alternative stable states and spatial indicators of critical slowing down along a spatial gradient in a savanna ecosystem More broadly, many degraded ecosystems show nonlinear responses to disturbance: recovery does not simply retrace the trajectory of degradation, meaning you cannot just remove the stressor and expect the system to rewind on its own.12Ecological Solutions and Evidence. Alternative stable states: Evidence from natural ecosystems and implications for ecological restoration
Succession in Water
Succession is not limited to terrestrial environments. Aquatic and wetland systems undergo their own version, sometimes called hydrarch succession, in which open water gradually fills in with sediment and organic matter until it transitions to marsh and eventually dry land.
Estuarine wetlands on Great Barrier Island in New Zealand offer a detailed case study. Pollen analysis of sediment cores revealed a linear sequence starting with mangroves, followed by estuarine marsh plants. From there, succession branched into two pathways: one driven by autogenic peat accumulation and one driven by sediment input from the surrounding terrain. The marine sedimentation phase was predictable and orderly, but the later freshwater phase depended on local hydrology and sediment dynamics, producing varied outcomes at different sites.
13Journal of Vegetation Science. Application of palynology to describe vegetation succession in estuarine wetlands on Great Barrier Island, northern New ZealandThis pattern, a predictable early phase followed by a branching, context-dependent later phase, echoes what terrestrial ecologists find as well. The early stages of succession tend to be more universal and repeatable. The later stages are where local quirks of soil, climate, and history start to dominate.
The Clements-Gleason Debate and Why It Still Matters
For over a century, ecologists have argued about whether succession follows a predictable, almost organism-like developmental pattern or whether it is a loose, probabilistic process driven by the individual responses of species. The two camps trace back to Frederic Clements, who viewed the plant community as a kind of superorganism progressing toward a fixed climax, and Henry Gleason, who saw plant communities as collections of individuals that happened to overlap based on their own tolerances and dispersal abilities.
The debate is often presented as a clean either/or, but a closer look at the original writings reveals that Clements and Gleason largely agreed on the causes of vegetation change. Their disagreement was more about methodology, specifically how to integrate those shared causes into a general theory. Clements favored a lawlike framework; Gleason preferred to emphasize the messiness of real vegetation.
14PubMed Central. Method and metaphysics in Clements’s and Gleason’s ecological explanationsModern ecology has largely sided with a synthesis. Yes, succession shows repeatable patterns, especially in the early stages. But no, the endpoint is not a fixed climax community predetermined by climate. Local disturbances, chance dispersal events, and the specific history of a site all introduce variability. The concept of a “climax” community has been mostly replaced by the idea of multiple possible stable states, shaped by the interplay of what has happened at a site and what continues to happen.
Climate Change and Shifting Trajectories
If succession depends on which species can tolerate local conditions, then changing those conditions changes the successional outcome. Climate change is already doing this. Modeling of forests in the Puget Lowlands of Washington State found that under a moderate emissions scenario, forest carbon dynamics and successional trajectories remained broadly consistent with historical patterns. But under a high emissions scenario, the successional trajectory shifted because individual tree species responded differently to rising temperatures and more variable precipitation.
15Forest Ecology and Management. Climate-driven changes in forest succession and the influence of management on forest carbon dynamics in the Puget Lowlands of Washington State, USAThe concern is not just that forests will grow differently, but that the species capable of colonizing disturbed sites in a warmer climate may not be the ones that historically played those pioneer roles. If the climate shifts faster than trees can migrate, succession after a disturbance might stall or produce novel community types with no historical precedent. Ecologists have flagged this as one of the urgent reasons for developing better successional frameworks, noting that predicting the effects of global change on succession and ecosystem recovery requires more sophisticated models than the field currently has.
16Ecosphere. A comprehensive framework for vegetation successionIndigenous Fire and Cultural Succession
Not all succession is “natural” in the sense of proceeding without human input. For thousands of years, Indigenous peoples around the world used fire as a tool to shape plant communities, and the landscapes that European colonizers encountered were often the product of this active management rather than undisturbed succession.
In the Karuk Aboriginal Territory of present-day northern California, researchers estimated that prior to colonization, cultural burning practices involved roughly 6,972 annual ignitions across the study landscape, averaging about 6.5 ignitions per fire steward per year. The combined effects of these intentional fires and natural lightning ignitions shaped the fire regime, the landscape mosaic, and the plant and animal resources available to the community.
17PubMed. Blending Indigenous and western science: Quantifying cultural burning impacts in Karuk Aboriginal TerritoryWhen colonization disrupted these burning practices, the landscapes did not revert to some pristine, pre-human successional trajectory. Instead, they followed new, often degraded pathways, with fuel buildup leading to catastrophic wildfire, loss of fire-dependent species, and the spread of shade-tolerant trees that had previously been kept in check. The ecological takeaway is that for many landscapes, “natural” succession includes human influence. Restoring healthy successional dynamics in these ecosystems requires reinstating the fire regimes that shaped them, ideally in collaboration with the Indigenous communities who developed those practices.
Practical Uses of Successional Science
Understanding succession has direct applications in restoration ecology, forestry, and land management. Successional models are used to predict how restoration projects will progress toward their goals, informing decisions about what to plant, when to intervene, and how long to wait.
18Restoration Ecology. The Scale of Successional Models and Restoration ObjectivesFor a land manager trying to restore a degraded site, the successional framework helps answer a cascade of practical questions. Is the site’s soil intact enough that secondary succession can proceed on its own, or does primary succession need to be jumpstarted with soil amendments and seeding? Are the right mycorrhizal fungi present, or do they need to be reintroduced? Will the pioneer species chosen attract the right seed-dispersing birds to bring in the next wave of plants? Is there a risk of invasive species locking the site into an alternate state that will need active removal?
The fruit-trait research from tropical landscapes, for instance, translates directly into planting recommendations: choosing pioneer trees with carbohydrate-rich fruits rather than wind-dispersed species can dramatically accelerate the natural recruitment of later-successional species by attracting more diverse bird communities. Similarly, understanding alternate stable states warns managers that simply removing a stressor, like grazing or pollution, may not be enough if the system has already crossed a threshold. Additional intervention, such as reseeding or removing invasive competitors, may be needed to push the system back onto a recovery trajectory.
As climate change reshapes species ranges and disturbance patterns, the old assumption that you can simply let nature take its course becomes less reliable. Restoration increasingly means not just mimicking historical succession but anticipating what succession will look like under future conditions, planting species that will thrive in the climate of 2060, not the climate of 1960.