A psammosere is the sequence of plant succession that has been initiated on sand. A psammosere is an intermediate stage in

ecological succession Ecological succession is the process of how species compositions change in an Community (ecology), ecological community over time. The two main categories of ecological succession are primary succession and secondary succession. Primary successi ...

, known as a

seral community A seral community is an intermediate stage found in ecological succession in an ecosystem advancing towards its climax community. In many cases more than one seral stage evolves until climax conditions are attained. A prisere is a collection of s ...

, that begins life on newly exposed coastal sand. The most common psammoseres are

sand dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, flat ...

systems. Psammosere is a form of

xerosere Xerosere is a plant succession that is limited by water availability. It includes the different stages in a ''xerarch succession''. Xerarch succession of ecological communities originated in extremely dry situation such as sand deserts, sand dune ...

succession, meaning it begins in an environment with limited to no

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

availability.

History

Psammosere's literal meaning is “originating on sand". It was named by Frederic E. Clements who described the sequence in ''Plant Succession'' 1916, although it had also been observed by

Henry Chandler Cowles Henry Chandler Cowles (February 27, 1869 – September 12, 1939) was an American botanist and ecological pioneer. A professor at the University of Chicago, he studied ecological succession in the Indiana Dunes of Northwest Indiana.Smith, S. & ...

after he conducted several studies on the sand dunes surrounding

Lake Michigan Lake Michigan ( ) is one of the five Great Lakes of North America. It is the second-largest of the Great Lakes by volume () and depth () after Lake Superior and the third-largest by surface area (), after Lake Superior and Lake Huron. To the ...

, which was influenced by the work of

Eugenius Warming Johannes Eugenius Bülow Warming (3 November 1841 – 2 April 1924), known as Eugen Warming, was a Danish botanist and a main founding figure of the scientific discipline of ecology. Warming wrote the first textbook (1895) on plant ecology, ta ...

Sand dune systems

Psammosere at Skinnet beach near Tongue - geograph

In a psammosere, the

organism An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...

s closest to the sea will be

pioneer species Pioneer species are resilient species that are the first to colonize barren environments, or to repopulate disrupted biodiverse steady-state ecosystems as part of ecological succession. Various kinds of events can create good conditions for pi ...

: halophytes (salt-tolerant species) such as

littoral The littoral zone, also called litoral or nearshore, is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely i ...

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

and glasswort, with marram grass stabilising the dunes. Progressing inland, many characteristics of the ground change which helps determine the natural succession of the dunes. For instance, the drainage slows down as the land becomes more compact and the soils improve in quality, and the pH drops as the proportion of

seashell A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer usually created by an animal or organism that lives in the sea. Most seashells are made by Mollusca, mollusks, such as snails, clams, and oysters ...

fragments reduces and the amount of

humus In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...

increases. Sea purslane,

sea lavender ''Limonium'' is a genus of about 600 flowering plant species. Members are also known as sea-lavender, statice, caspia or marsh-rosemary. Despite their common names, species are not related to the lavenders or to rosemary. They are instead in Plu ...

, meadow grass and heather eventually grade into a typical non-maritime

ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

. The first trees (or pioneer trees) that appear are typically fast-growing trees such as

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...

birch A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech- oak family Fagaceae. The genus ''Betula'' contains 3 ...

willow Willows, also called sallows and osiers, of the genus ''Salix'', comprise around 350 species (plus numerous hybrids) of typically deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions. Most species are known ...

rowan The rowans ( or ) or mountain-ashes are shrubs or trees in the genus ''Sorbus'' of the rose family, Rosaceae. They are native throughout the cool temperate regions of the Northern Hemisphere, with the highest species diversity in the Himalaya ...

. In turn these will be replaced by slow-growing, larger trees such as ash and

oak An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...

. This is the

climax community In scientific ecology, climax community or climatic climax community is a historic term for a community of plants, animals, and fungi which, through the process of ecological succession in the development of vegetation in an area over time, hav ...

, defined as the point where a plant succession does not develop any further because it has reached equilibrium with the environment, in particular the

climate Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteoro ...

. The later stages of a psammosere appear when the sand stops moving due to lower wind speeds. These lower wind speeds can be because of distance from the shoreline or the formation of higher dunes, acting as windbreaks, or a combination of both of these factors. The process by which different stages succeed each other is known as "plant colonisation".

Effect on pH

In an idealised model of a coastal psammosere at the seaward edge of the sand dune, the pH of the soil is typically alkaline/neutral with a pH of 7.0/8.0 particularly where shell fragments provide a significant component of the sand. Further inland, the soil's pH decreases as the soil gets more acidic. Tracking inland across the dunes, a

podsol Podzols, also known as podosols, spodosols, or espodossolos, are the typical soils of coniferous or Taiga, boreal forests and also the typical soils of eucalypt forests and heathlands in southern Australia. In Western Europe, podzols develop on he ...

develops with a pH of 5.0 – 4.0, followed by mature podsols at the climax with a pH of 3.5 – 4.5.

Human effects

Psammosere succession is also extremely vulnerable to human activities. At beaches, footpaths over dunes will trample grass, creating exposed sand. This exposed sand can be blown away very easily, leading to the roots becoming exposed and neighbouring plants dying. This creates blowouts, which can set back psammosere succession. Efforts have also been made to improve the psammosere in some regards. In some areas, pine trees are an invasive species and can take over heathland. The

National Trust The National Trust () is a heritage and nature conservation charity and membership organisation in England, Wales and Northern Ireland. The Trust was founded in 1895 by Octavia Hill, Sir Robert Hunter and Hardwicke Rawnsley to "promote the ...

in the UK encourages people to pull up small Pine trees as they can leave needles on the ground, which can prevent further psammosere succession through the dropping of needles.

References

External links