Sandy succession, often called a psammosere, is the step-by-step transformation of bare sand into a complex, soil-rich ecosystem. It unfolds over decades to centuries as waves of organisms colonize raw sand, each generation changing the habitat enough to allow the next to take hold. On coastal dunes, the process creates a visible gradient: sparse, salt-tolerant pioneers nearest the shore give way to dense shrubland and eventually woodland further inland. The sequence is surprisingly predictable in its broad outlines, but the details depend on climate, sand supply, and whether humans have left the system alone.
How It Starts on Bare Sand
The earliest stage of sandy succession begins with a problem most plants cannot solve. Raw sand holds almost no water, contains virtually no organic matter or nutrients, shifts with every gust of wind, and on coastal dunes gets blasted with salt spray. Only a handful of specialist grasses and herbs can survive these conditions. On European and North American Atlantic coasts, marram grass (Ammophila arenaria) is the classic pioneer. Its trick is counterintuitive: being buried in sand actually makes it grow faster. Experiments show that moderate burial stimulates shoot growth within days, and root mass increases significantly even at fairly deep burial levels. At the highest burial intensities, root biomass still climbs even though the above-ground parts struggle, anchoring the plant and trapping more sand in a self-reinforcing cycle.
1Botanica. Variation in Growth Response of Coastal Dune-Building Grass Species Ammophila Arenaria and Leymus Arenarius to Sand BurialNot all pioneer grasses use the same strategy, though. Lyme grass (Leymus arenarius), another common dune-builder, responds to burial differently. Rather than simply packing on root mass, it tends to shift its growth toward elongating its leaf sheaths, stretching upward to stay above the accumulating sand. Its root mass can actually decrease under deep burial. These differences matter because they mean that two species sharing the same patch of foredune may be coping with sand movement in fundamentally different ways, and the balance between them shapes how fast the dune grows and stabilizes.
2Botanica. Variation in Growth Response of Coastal Dune-Building Grass Species Ammophila Arenaria and Leymus Arenarius to Sand BurialThe Functional Shift from Beach to Backdune
If you walk inland from the tideline on a Mediterranean or Atlantic coast, you cross a living timeline. Each zone represents a later stage of succession, and the plants inhabiting it have measurably different survival strategies. Research on Mediterranean coastal dunes shows that the pioneers nearest the sea are fast-growing opportunists adapted to harsh, unpredictable conditions. As you move inland and conditions become less extreme, the dominant plant strategy shifts toward stress tolerance. Species in the older, more stable backdune zones invest in tougher, longer-lasting leaves rather than rapid reproduction.
3Estuarine, Coastal and Shelf Science. Mediterranean coastal dune vegetation: Are disturbance and stress the key selective forces that drive the psammophilous succession?This is not just a casual observation about leaf shape. It reflects a deep functional reorganization of the plant community across the dune gradient, from species that gamble on quick growth and prolific seeding near the shore to species that hunker down and conserve resources in the more sheltered interior. The diversity of strategies involved is greater than many ecologists initially expected, and it suggests that psammophytes have evolved multiple independent solutions to living on sand rather than following a single template.
4Estuarine, Coastal and Shelf Science. Mediterranean coastal dune vegetation: Are disturbance and stress the key selective forces that drive the psammophilous succession?How the Sand Itself Changes
Plants are the most visible agents of sandy succession, but the real transformation happens underfoot. As vegetation establishes, dead roots and leaf litter begin mixing into the upper sand layers. This accumulation of organic matter, slow at first, eventually changes the sand’s ability to hold water and nutrients. Studies of Lake Huron sand dunes found that the oldest, most advanced successional zones had higher organic matter content, greater moisture-holding capacity, and elevated concentrations of available potassium and magnesium compared to younger dune zones. Calcium levels in the surface soil were actually lower in these older zones, a sign of chemical weathering over time.
5Canadian Journal of Botany. Microenvironment of Lake Huron sand dunesThe physical microclimate changes too. Older dune zones with denser vegetation experience less air turbulence and slightly warmer air temperatures. These seemingly small shifts create feedback loops. More moisture and nutrients support more plant growth, which adds more organic matter, which holds more moisture. This self-reinforcing process is what drives succession forward, and it is why disturbing a late-stage dune system is so much harder to undo than preventing the disturbance in the first place.
6Canadian Journal of Botany. Microenvironment of Lake Huron sand dunesThe Hidden Role of Fungi
One of the less obvious forces pushing succession forward is underground: mycorrhizal fungi. These fungi form partnerships with plant roots, extending their reach into sand that the roots alone could not exploit effectively. When dune plants are buried by fresh sand, mycorrhizal fungi help them tap into the resources locked in the new deposit. Experiments with dune grasses showed that plants grown with mycorrhizal fungi and then buried in fungi-containing sand had the highest rates of carbon uptake, the largest leaf area, and the greatest overall biomass compared to plants without fungal partners.
7Functional Ecology. The role of mycorrhizal fungi in growth enhancement of dune plants following burial in sandThis partnership is especially important during the middle stages of succession, when sand is still mobile enough to bury established plants but stable enough to support more complex vegetation. The fungi essentially act as a nutrient-gathering network, letting plants survive burial events that might otherwise kill them. Without this fungal infrastructure, the transition from pioneer grassland to mixed shrubland would likely take much longer, and some species might not establish at all.
Microbial Communities Track Successional Stage
It is not just fungi. The entire microbial world in the sand shifts as succession progresses, and recent sequencing work has started to map these changes in detail. At Indiana Dunes National Park, researchers found that bacterial communities in the soil were clearly distinct across different successional stages. The primary factor separating them was the stage of succession itself, which accounted for roughly half of the variation in community composition when measured by certain diversity metrics.
8Journal of Great Lakes Research. Bacterial community structure across a sand dune chronosequence at the Indiana Dunes National ParkCoastal dune studies have added nuance to this picture. Different successional habitats harbor distinct soil communities that vary in both their species makeup and their functional roles. Interestingly, bacteria and fungi do not always peak in diversity at the same point. One study found that bacterial diversity was greatest in the interdune flats, while fungal diversity peaked in the foredunes.
9Journal of Coastal Research. Soil Microbial Community Diversity Varies by Coastal Dune Successional StageWork on Arctic sand dunes adds an important qualifier. While community composition changes significantly between early and late successional stages across every compartment examined (bulk soil, root interior, leaf interior, and the zone immediately around roots), overall microbial diversity measured by standard indices did not necessarily increase. In other words, succession reshuffles which microbes dominate without always increasing the total number of species present. The major microbial groups were shared between early and late stages, but their relative abundance shifted. Bacteria and fungi also appeared to follow different trajectories through succession, meaning you cannot assume that what holds for one kingdom holds for the other.
10PubMed. Microbial community composition but not diversity changes along succession in arctic sand dunesAnimal Life Follows the Plants
As vegetation structure becomes more complex through succession, the arthropod community responds. Research on arid dunes found that the semi-stabilized slopes, where vegetation cover was patchy but present, supported the highest abundance of invertebrates. More than half of the dominant species showed a clear preference for or avoidance of specific landscape units. Beetles, particularly darkling beetles, made up the bulk of individuals collected, and their distribution tracked habitat type closely.
11Global Journal of Ecology. Impact of spatial patterns on arthropod assemblages following natural dune stabilization under extreme arid conditionsThe interdune flats, despite being the most stable and often the most vegetated, actually had the lowest arthropod abundance in this system. This counterintuitive finding highlights that animal succession does not simply track vegetation density. The mix of bare sand and scattered plant patches on semi-stabilized slopes may offer a wider range of microhabitats, thermal regimes, and foraging opportunities than either fully bare or fully vegetated ground.
12Global Journal of Ecology. Impact of spatial patterns on arthropod assemblages following natural dune stabilization under extreme arid conditionsFreshwater Beneath the Dunes
An easily overlooked ecosystem service of dune succession is what happens to rainwater. As vegetation and organic matter build up, dunes begin to function as freshwater reservoirs. Rain infiltrates through the sand and collects in thin lenses of fresh groundwater that float above denser, saltier water below. Research along the Adriatic coast in Italy found that these freshwater lenses, where they exist, are typically only about one to two meters thick. Their persistence depends heavily on dune size and elevation, and human disturbance like nearby drainage ditches can prevent lenses from forming at all.
13Journal of Hydrology. Natural and anthropogenic factors affecting freshwater lenses in coastal dunes of the Adriatic coastThis freshwater storage capacity is a direct product of succession. Bare, unvegetated sand lets rainfall run off or evaporate quickly. As organic matter accumulates and the soil structure develops through successional stages, water retention improves, and the conditions for maintaining a freshwater lens become more favorable. Where dunes have been degraded or flattened by development, this hydrological function is lost, often with consequences for the vegetation and wildlife that depend on shallow groundwater access.
When Succession Gets Hijacked
Sandy succession can be diverted or arrested by both invasive species and deliberate human planting. Dune-stabilizing invasive plants are a widespread problem because they suppress the natural sand movement that early-successional species depend on. In northern California, researchers studied two federally endangered plants, both of which had higher frequencies in early successional microhabitats. One of the species, a perennial lupine, had higher projected population growth rates in early successional areas than in stabilized, late-successional habitats, mainly because seedling recruitment was so much better where sand was still moving. The conclusion was stark: these species need active sand disturbance to persist, and invasive plants that lock the dunes down threaten their survival.
14PLoS ONE. Early Successional Microhabitats Allow the Persistence of Endangered Plants in Coastal Sand DunesDeliberate afforestation has caused similar disruption. Across southern Europe and parts of North America, pine plantations were established on dunes in the 19th and 20th centuries to halt sand movement that threatened infrastructure. In southwestern Spain, coastal pine plantations have been shown to strongly alter both the environmental factors and the plant zonation along the sea-to-inland gradient, particularly by reducing sand mobility and salt spray deposition.
15Estuarine, Coastal and Shelf Science. Effects of pine plantations on coastal gradients and vegetation zonation in SW SpainThe non-native Austrian pine (Pinus nigra) planted on Great Lakes dunes reduced cover of native dune vegetation and, at forest edges, appeared to accelerate succession toward a woody community at the expense of open dune habitat.
16Canadian Journal of Botany. Ecological effects of the non-native Pinus nigra on sand dune communitiesNitrogen and the Buckthorn Problem
One particular invasive shrub illustrates how profoundly a single species can alter dune chemistry. Sea buckthorn (Hippophae rhamnoides) hosts nitrogen-fixing bacteria in its roots, which means it pumps nitrogen into nutrient-poor dune sand. Research at coastal sites in Northern Ireland found that sand beneath mature sea buckthorn had nitrate-nitrogen concentrations several times higher than at control sites. Removing the buckthorn does not immediately fix the problem either: groundwater nitrate concentrations spiked dramatically after removal, with one monitoring well recording an increase of over 10 mg/l in the ten months following clearing. It took roughly two years for nitrate levels to begin dropping back toward acceptable thresholds.
17ScienceDirect. Removal of previously planted tree and shrub species and the impacts on the shallow groundwater chemistry of coastal dune systems in northern IrelandThis nitrogen loading matters because the whole premise of early dune succession is nutrient scarcity. Pioneer species are adapted to impoverished sand. When an invasive nitrogen-fixer enriches the soil, it gives a competitive advantage to later-successional or weedy species that would normally have to wait decades for organic matter to accumulate. The entire successional timeline gets compressed and skewed, often permanently changing which species can establish.
Restoring Sand Movement
Conservation managers have increasingly turned the traditional approach on its head. Instead of stabilizing dunes, they are trying to destabilize them, reintroducing the natural sand movement that maintains early successional habitats. One common technique is foredune notching: cutting V-shaped gaps through the established foredune ridge to let wind push beach sand inland again. A multi-site study in Wales found that notching produced an approximately fivefold increase in sand flux at intervention sites compared to controls, though the results varied enormously between locations. One site saw sand flux jump by over 200 grams per square meter per day at the closest monitoring point, while another showed almost no detectable change.
18Ecological Engineering. Dynamic dune restoration: Site-specific variability in sediment transport and soil response following notch creationSoil changes from notching were more modest. Organic matter dropped by about 29% at intervention sites, a meaningful shift back toward early-successional conditions but not a wholesale transformation. These results point to an honest limitation of restoration efforts: you can increase sand movement relatively easily, but reversing decades of soil development is harder and takes longer. The approach is increasingly popular across northwestern Europe, where managers aim to reconnect the beach-dune system and create habitat for species that depend on dynamic, shifting sand.
19Aeolian Research. Coastal dune dynamics in response to excavated foredune notchesSea-Level Rise and the Squeeze
Climate change poses a fundamental threat to the entire successional gradient. As sea levels rise, the beach narrows, and the space available for the earliest successional stages shrinks. Simulations of sea-level rise scenarios have demonstrated that beach erosion can constrain pioneer plant populations to such a narrow strip that the successional process breaks down entirely.
20Frontiers in Ecology and the Environment. Coastal erosion, global sea-level rise, and the loss of sand dune plant habitatsAt the same time, warming temperatures and changing precipitation patterns are driving vegetation growth further seaward and encouraging invasive species expansion. The combined effect is a kind of ecological squeeze: the beach erodes from one side while stabilizing vegetation advances from the other, compressing or eliminating the early successional zones that many specialist species require. Urbanization and sand mining compound the problem by removing dune material outright.
21Annual Review of Environment and Resources. Shifting Sands: Past, Present, and Future of Coastal DunesSandy Succession Away from the Coast
The process is not limited to beaches. Inland sand dunes, found from central Europe to desert margins, undergo their own version of succession. Biological soil crusts, thin living layers of mosses, lichens, cyanobacteria, and algae, often play the role that pioneer grasses fill on coastal dunes. Research on restored inland sand dunes showed that these crusts increased organic carbon, total nitrogen, and nutrient availability as succession advanced, while also acidifying the soil. The species composition of the crusts themselves changed with successional stage, driven by soil pH, nitrogen content, and water-holding capacity.
22SpringerLink (Plant and Soil). Mosaic of biological soil crusts and vascular plants contributes to the spatial heterogeneity of key soil properties at different successional stages of restored inland sand dunesOne interesting difference from coastal systems is that bare soil between crust patches in inland dunes actually had higher concentrations of inorganic nitrogen than the soil beneath the crusts. This suggests the crusts are actively converting nitrogen into organic forms and incorporating it into biomass, rather than simply accumulating it passively. The mosaic of crusted and bare patches creates a patchwork of soil conditions that supports a surprising range of plant and microbial life even at relatively early successional stages.
23SpringerLink (Plant and Soil). Mosaic of biological soil crusts and vascular plants contributes to the spatial heterogeneity of key soil properties at different successional stages of restored inland sand dunesWhat Ancient Dunes Tell Us
Palaeoecological records show that sandy succession has been cycling through phases of activity and stabilization for thousands of years, driven by climate shifts rather than anything humans did. Pollen and sediment records from southwest Slovakia reveal that during warmer, wetter periods in the last ice age, open dune fields stabilized under pine and birch woodlands, completing a successional sequence from bare sand to forest.
24Quaternary International. Interstadial inland dune slacks in south-west Slovakia: a multi-proxy vegetation and landscape reconstructionConversely, episodes of inland sand movement in northwestern Denmark were triggered by shifts toward cooler, wetter, stormier conditions, which increased coastal erosion and sent beach sand blowing inland. These sand invasions essentially reset the successional clock, burying established vegetation and restarting the process from scratch.
25Sedimentology. Sedimentology, stratigraphy and landscape evolution of a Holocene coastal dune system, Lodbjerg, NW Jutland, DenmarkThis long view is useful because it puts modern concerns in context. Sandy succession is not a one-way march toward forest. It is a cycle that climate and disturbance have interrupted and restarted repeatedly over millennia. The dune systems we see today are snapshots of a process that has never reached a permanent endpoint, and probably never will.