Secondary succession is the process by which a biological community rebuilds itself after a disturbance that damages or removes most of the living organisms but leaves the soil and its buried seed bank largely intact. Wildfires, hurricanes, logging, and the abandonment of farmland are the classic triggers. Because the soil, seeds, root fragments, and microbial communities survive, recovery during secondary succession is substantially faster than primary succession, where life colonizes bare rock or fresh volcanic deposits with no existing soil at all. How fast, and how completely, the ecosystem bounces back depends on the severity of the disturbance, what was growing there before, and whether new pressures like invasive species get in the way.
How Secondary Succession Differs from Primary Succession
The defining difference is the starting point. Primary succession begins on substrates that have never supported life or have been stripped down to bare mineral surfaces, such as cooled lava flows, newly exposed glacial till, or fresh sand dunes. Everything has to arrive from scratch: soil-forming organisms, windblown seeds, nutrients. Secondary succession skips that long opening chapter because the soil already exists. Organic matter, nitrogen, phosphorus, fungal networks, and dormant seeds are all still present in varying degrees. That head start is enormous. A comparison across biomes found that primary successions were more likely to show steady increases in species richness over time, while secondary successions tended to start with higher richness and follow more variable trajectories, partly because alien species played a larger role in secondary settings.
What Triggers It
Almost any disturbance that removes the aboveground community without destroying the soil qualifies. The most studied triggers include wildfire, agricultural abandonment, storm damage, and timber harvest. Each leaves a different legacy in the soil, and that legacy shapes what comes next.
Fire is a particularly well-studied trigger because its severity varies so much from one burn to the next. In lightly burned soils, microbial communities and nutrient cycles may barely change. In severely burned soils, the picture is different: researchers studying secondary succession after forest fire found that recolonizing plants had a much stronger effect on soil bacterial communities and nutrient levels in severely burned patches than in lightly burned ones, boosting nitrogen, organic carbon, microbial biomass, and enzyme activity.
Abandoned farmland, sometimes called “old fields,” is the other major starting condition. Decades of tillage, fertilization, and altered hydrology leave a lasting imprint on soil chemistry and seed banks. The assembly of plant communities on old fields has been one of the richest sources of data on how succession actually works, and the growing global trend of farmland abandonment means these landscapes are becoming more ecologically significant, not less.
The Stages of Recovery
Secondary succession does not follow a rigid sequence of steps like a recipe, but it does have a recognizable general pattern: fast-growing, sun-loving species dominate first, then gradually give way to slower-growing, shade-tolerant species that define the mature community. Ecologists sometimes describe this in loose phases.
Early Colonizers
In the first months to years, annual weeds, grasses, and fast-germinating herbs fill the open ground. These species share a set of traits: high photosynthetic rates, small seeds that disperse easily, and short lifespans. In Mediterranean ecosystems, early successional herbs were found to have high leaf area relative to leaf weight, produce foliage continuously through the growing season, and escape summer drought simply by completing their life cycle before it arrives.
In tropical forests, the equivalent role is played by pioneer trees. A detailed study of secondary succession in Southeast Mexico tracked three dominant pioneer tree species over 35 years and found a clear relay pattern. The fastest colonizer, Trema micrantha, peaked in density and then vanished within about 15 years. Cecropia peltata lasted roughly 28 years. Trichospermum mexicanum persisted beyond 31 years. Each species showed a hump-shaped rise and fall in population density, and the speed at which seedlings recruited and mature trees died determined how long each species held its place.
Intermediate Stages
As the canopy begins to close, light at ground level drops and the conditions that favored pioneer species disappear. Shrubs, perennial grasses, and shade-tolerant saplings start to replace the early colonizers. A 30-year study of forest understory dynamics found that canopy cover increased fourfold over the study period and stem density rose by about 75 percent, while understory richness and biomass declined by roughly 30 to 40 percent, driven mostly by the loss of the early colonizing species rather than the suppression of species that had survived from the pre-disturbance forest.
Research on tropical saplings identified distinct syndromes along this gradient. Species with higher photosynthetic rates, shorter adult statures, and lighter seeds did well in the bright conditions of young secondary forests. Species classified as “long-lived pioneers” or “late successional” had trait profiles suited to surviving in the shade of an increasingly dense canopy or reaching the upper canopy in older forests.
Late Succession and Maturity
Eventually the community comes to be dominated by large, long-lived species whose traits are geared toward persistence rather than rapid colonization. In Mediterranean secondary succession, the late-stage trees had dense leaves capable of tolerating desiccation and large bodies that could tap deep resource pools. Throughout eastern deciduous forests in the United States, seed mass and wood density both increase with stand age, reflecting a broad shift from fast-growing, light-seeded ruderals to heavier-seeded, slower-growing competitors and stress-tolerators.
How Long Recovery Takes
This is one of the most common follow-up questions, and the honest answer is that it depends enormously on what you are measuring and where you are. Soil properties tend to bounce back first, sometimes within a single decade. Plant function, meaning rates of growth and nutrient cycling, recovers within a couple of decades. Structure and species diversity take longer, on the order of two and a half to six decades to reach 90 percent of old-growth values. Biomass and species composition are the slowest, needing more than 12 decades.
Tropical secondary forests illustrate this gap well. In Costa Rica, researchers found that aboveground biomass accumulated rapidly in early succession, reaching about 52 percent of old-growth levels after 20 years. Species richness, however, had recovered only about 31 percent of old-growth richness in the same period. A broader analysis across Neotropical secondary forests estimated a median time of five decades for species richness to fully recover, with roughly 80 percent recovery after 20 years. Species composition, meaning the specific mix of species rather than just how many there are, was only 34 percent recovered after 20 years and is projected to take centuries to match old-growth forests.
After wildfire, the timeline follows a similar pattern. A review of post-wildfire recovery found that in a temperate climate with an average fire regime, abiotic soil factors can be restored within about a decade, while vegetation composition needs 15 to 25 years. Structure, meaning the height, layering, and spatial arrangement of the forest, lags further behind.
What Happens Underground
Most of what you see in secondary succession, the grasses and shrubs and trees filling in, is being shaped by events you cannot see. Soil microbes, and especially mycorrhizal fungi, play a surprisingly active role. These fungi form partnerships with plant roots, extending threadlike networks through the soil that help plants access water and nutrients, especially phosphorus. In return, the plant feeds the fungus sugars.
Field evidence suggests that mycorrhizal fungi may actually arrive at disturbed sites before plants do, priming the soil for colonization. A study of co-occurring plant and fungal communities during succession found that despite the assumed low dispersal capacity of these fungi, they appeared to be successful early colonizers of disturbed sites, and their composition was strongly correlated with plant community composition at fine spatial scales.
This relationship matters for restoration. Experiments have shown that reintroducing native mycorrhizal fungi, whether from whole-soil inoculants or lab-grown cultures, can accelerate plant succession and improve the establishment of native plants following disturbance. Mycorrhizal fungi have also been shown to help prevent invasion by alien plant species, adding another layer to their influence on successional outcomes.
When Succession Gets Stuck
Not every disturbed landscape marches neatly toward a mature community. Invasive species are one of the most common reasons succession stalls or veers off course, a phenomenon ecologists call “arrested succession.”
In a 20-year study of old-field succession on abandoned farmland in Argentina, four exotic grasses maintained 50 to 70 percent cover throughout the entire study period. Native perennial grasses were present from the beginning and slowly increased in the number of species per plot, but they never exceeded about 30 percent cover and only in brief peaks. The researchers identified alternative community states for early, mid, and late succession connected by complex, interweaving pathways, some of which were arrested states dominated by exotic grasses.
A similar pattern shows up in other grasslands. Research on old-field succession found that the recovery of native grasses was constrained by two things working together: limited seed arrival and the prior occupation of the site by exotic grasses. Native species could only re-establish at the expense of displacing the exotics, which is far harder than colonizing open ground.
In tropical dry forests, the situation can be even more severe. A field experiment in the Brazilian Caatinga found that highly disturbed areas with invasive species present had impoverished plant assemblages dominated by a few herbs, shrubs, and subshrubs, indicating a scenario where succession had essentially stopped. The invasive plants acted as barriers to forest regeneration, potentially precluding the persistence of native species and undermining the forest’s ability to recover.
Animals Change Too
Succession is not only a plant story. As vegetation structure shifts, so does the animal community. A study of mixed-species bird flocks across forest succession found a clear pattern tied to the fast-slow continuum of life histories. In early successional stages, the flocks were composed of fast-living species: smaller-bodied birds with larger clutch sizes. As the forest matured and vegetation complexity increased, offering more niches and resources, these species were gradually replaced by slower-living species with larger bodies and smaller clutches. The intermediate stage was a mix of both. Vegetation complexity, including tree size, height, diversity, and canopy cover, appeared to shape both the network structure and functional composition of these bird communities.
How Ecosystems Beyond Forests Recover
Secondary succession is not exclusive to forests and grasslands. Wetlands and coastal marshes follow their own versions of the process, sometimes with strikingly different dynamics.
In estuarine marshes, recovery rates varied dramatically across a salinity gradient. Brackish and low-salinity marshes recovered three to ten times faster than salt marshes. The mechanism differed too: in low-salinity marshes, seedling colonization drove the fast recovery, with seed bank densities up to 24 times higher than in salt marshes. Salt marsh recovery relied more on vegetative runners, a slower process. The successional model also differed. Low-salinity marshes followed a tolerance model, where many species colonized from seed simultaneously and were slowly displaced by clonal grasses. Salt marshes followed a facilitation model, where early species modified the environment in ways that helped later species establish.
Constructed wetlands show yet another variant. A 35-year study of a freshwater mitigation wetland in New Hampshire found that the rate of species gain was very high in the first seven years after construction, then dropped sharply. Species loss and turnover rates also declined steadily over time, suggesting the community was stabilizing. After the initial burst of colonization, the wetland settled into a pattern of low but steady successional turnover.
Wet Versus Dry Forests Follow Opposite Paths
One of the more counterintuitive findings in succession research is that wet and dry tropical forests recover along opposite trajectories for wood density, a key trait linked to how trees allocate resources. In wet forests, succession proceeds from communities with low wood density toward high wood density, fitting the standard expectation that fast-growing, resource-acquisitive pioneers give way to denser, more conservative species. In dry forests, the direction reverses: early communities have high wood density, reflecting the need for drought tolerance in the harsh, sun-blasted conditions of a freshly disturbed site, and wood density decreases as the forest matures and conditions become less extreme. Over time, wet and dry forests converge, but their paths to get there are mirror images.
Restoration in Practice
Understanding secondary succession has direct practical value. One of the key decisions in ecological restoration is whether to let succession proceed on its own, called passive restoration, or to intervene actively by planting native species, removing invasives, or altering soil conditions.
The answer depends heavily on context. A meta-analysis of dryland agricultural ecosystems found that passive restoration through vegetation regrowth and grazing exclusion led to net positive outcomes but was more variable and generally less effective than active restoration. Passive soil restoration actually produced net negative outcomes in these settings, probably because of the severity of past degradation and ongoing environmental stressors. Active interventions, especially water supplementation, consistently produced positive results for soil, plant, and habitat targets.
In the U.S. Midwest, a comparison of passively restored old fields with actively restored tallgrass prairies told a similar story. The passively restored site, left to undergo spontaneous secondary succession, did not achieve the species diversity or richness of the actively restored prairie. The two sites diverged onto separate successional trajectories, with the old field making very little progress toward a native prairie state, likely because invasive plants had established a strong priority effect. The researchers recommended active removal of exotic species, augmentation with native plants including nitrogen-fixing legumes, and periodic prescribed burns.
Traditional Land Use and Secondary Succession
Not all human disturbance is created equal when it comes to how well succession proceeds afterward. In southern Mexico, researchers compared two styles of swidden agriculture, an approach where farmers clear forest patches, farm them briefly, then let them regrow. The traditional milpa system, which uses shorter cultivation periods and preserves more of the forest’s biological legacy, generated early fallows with greater diversity, more ecosystem services potential, and better prospects for early forest recovery compared to a more intensive semi-permanent system.
In the Bolivian Amazon, indigenous communities actively managed their fallow forests rather than simply abandoning them. Out of 280 species recorded in secondary forests following swidden agriculture, 123 were useful to the local population as food, medicine, or construction material. Most community members preferred mature forest for creating new fields but valued fallows for their crops, useful species, and the timber species regenerating within them. This kind of management blurs the line between “natural” succession and deliberate cultivation, and it challenges the assumption that secondary succession is something that happens only in the absence of people.
Climate Feedbacks and Future Uncertainty
Climate change adds a layer of unpredictability to secondary succession that researchers are still working to understand. In tropical second-growth forests, fire and cyclonic storms can create positive feedback loops: a severe storm opens the canopy, which dries the forest floor, which makes it more vulnerable to fire, which sets succession back further. Human activities that increase fire frequency or intensity can retard succession, and these effects interact with climate variability in ways that are difficult to predict.
The concern is not just that individual disturbances will become more frequent or severe, but that repeated disturbances may push ecosystems past thresholds from which secondary succession alone cannot recover. When you combine more intense wildfires with warmer and drier conditions, some landscapes may fail to regenerate to forest at all. Research on post-wildfire regeneration in the western United States found that while tree regeneration was abundant across most study plots, with a median density of over 4,400 stems per hectare, about 15 percent of plots fell below minimum stocking standards for timber production. Escalating wildfire severity and warming trends mean that forest regeneration after fire is no longer assured in many of these environments.