Saltmarshes
Saltmarshes
• Saltmarshes often found in upper reaches of an estuary (and elsewhere)
• Sand/Clay/Silt and/or organic materials• Minerogenic or organogenic marshes• Classification into: open coast marshes;
back-barrier marshes; estuarine-fringing marshes; embayment marshes; loch or fjord-head marshes
Saltmarshes
• Evidence of accretion (but also erosion)• Controlling Factors: sediment supply;
tidal regime; wind-wave climate; movement of relative sea level
• Tidal cycles, inundation, accretion• Saltmarsh ecosystems are sensitive to
changes in sea level and isostatic adjustments to the level of the land
Saltmarshes
• Tidal range and exposure• Submergence and emergence marsh• Low, middle and high marsh• Accreting salt marshes can gain height
and prograde (increase in seaward extent)
• Saltmarshes can build in height (vertical accretion) but can also suffer subsidence (compaction of sediments)
Saltmarshes
A salt marsh is "born" by the arrival of a seed or the rafting of a plant of the cord grass Spartina alterniflora. The grass spreads asexually by means of a subterranean rhizome system. The grass becomes dense and forms a baffle, which encourages the deposition of fine particulate sediment, including organic matter (salt marsh peat). This, in effect, causes a rise of the sediment surface and makes the habitat more terrestrial. As this happens, other somewhat less salt-tolerant grasses are able to invade. Eventually, this series of invasions and takeovers leads to a vertical zonation of grasses and a spread of the entire marsh system.
SAS = Spartina alterniflora - short form
SP = Spartina patens, the next higher grass species
Saltmarshes
• Topography of saltmarsh results from the interaction of the processes of deposition, erosion, and sediment consolidation
• Formation of Creeks and Salt Pans• Primary and Secondary Pans• Creek or Channel Pans• Microtopography
Saltmarshes
• Slope and presence of creeks and salt pans influences the distribution of animals and plants
• Zonation of vegetation (low, medium, high)• Number and distribution affected by
location in saltmarsh, but also local climate e.g precipitation as well as evapotranspiration
• Many species of plants and animals
Saltmarshes
Saltmarshes
Saltmarshes
Saltmarshes
• Flora: Salicornia and Sarcocorni (glassworts), Spartina (cord-grass), Juncus (rushes), Plantago (plantains), and Limomium (sea-lavendars) - grasses are often very common ( Spartina anglica, Puccinellia maritima, Festuca rubra, Agrostis stolonifera, Phragmites australis, Spartina alterniflora
Saltmarshes
• Developmental zonation• Many saltmarshes are very old - well
established• Zonation may be well established• Vegetation succession (organisms and
environment - Autogenic versus Allogenic factors)
• Varying nutrient, fluvial and groundwater fluxes between saltmarshes and estuaries
Saltmarshes
• Net importers / Net exporters of nutrients (nutrient flux)
• In maritime saltmarshes: tides influence sedimentation rates, ionic relationships, water regime, photosynthesis, and ability of seedlings to establish
Saltmarshes
• Animals:marine invertebrates, deposit feeders, burrowing worms, oligochaete and polychaete worms, crustaceans, ragworms, bivalve molluscs, gastropods, crabs, fish, insects, birds, rabbits
Saltmarshes• Facultative mutualisms between Spartina
alterniflora and the marsh mussel Geukensia demissa and between and fiddler crabs Uca pugax
• Fiddler crabs increase soil aeration• Mussels deposit nitrogenous
wastes • Spartina anglica - invades
intertidal flats rich in invertebrates and promotes reclamation
• In some places losing ground - oil pollution and accumulation of fine-grained sediment
Saltmarshes• Saltmarsh dynamics• Seasonal growth and dieback• Halophytes and Glycophytes• Seasonal biomass accumulation• Rainfall and salinity affects vegetation
cover/survival• Seasonal behaviour in animals e.g. birds• Impact of grazing on plants and succession• Biomass, productivity and energy flow• Algal productivity: creek sides, plant stems
Saltmarshes
• Spartina alterniflora marsh• Ecological processes involved in terms
of the overall carbon balance• Ecological processes in the water:
phytoplankton, filter feeding, particle feeding, microbial assimilation
• Ecological processes in the marsh sediments
• Tidal exchange for transport of organic matter
Sand Dunes
Sand Dunes
• Large supplies of sand moved onshore by wind
• Integrated beach-dune system• Deflation / Abrasion / Saltation / Surface
Creep• Sand dunes found around the World• Dynamic environment but can become fixed• Some are devoid of vegetation others are
not (phytogenic)
Sand Dunes
• Different classifications of dunes• Shape or form, orientation (parabolic,
transverse, longitudinal)• Characterised by spatial distribution of
sand, height, presence/absence of vegetation, topography
• Formation (and duration) dependent upon supply of sand, obstacles, rate of sand transport, wind direction/speed, changes
Sand Dunes
• Transect through dunes: sea, foreshore, strandline, backshore, embryo dunes, mobile (young or yellow dunes), (lower) unconsolidated dunes, consolidated (mature) grey dunes, and the maritime sward (dune heath) (also dune slacks)
• From sea to land: ground wind speed, influence of salt spray, soil pH and levels of soil calcium, and sodium diminish whilst….
Sand Dunes
• Extent of vegetation cover, amount of organic matter, number of plant and animal species and overall stability increase
• Exposure and shelter (from wind and salt water) determine the type and distribution of plants
• Landform, soil and water regime have an influence on the vegetation
• Over time soils develop: mineral versus organic material e.g. in dune slacks
Sand Dunes• Mobility of sand through erosion will determine
where the vegetation grows• Sand often has little in the way of nutrients• Limiting levels of nutrients: nitrogen, phosphorous
and potassium• Shell fragments provide calcium• As the proportion of organic matter increases so
the ability of the soil to retain moisture and nutrients rises
• Fixed rather than mobile dunes will have more soil development
Sand Dunes
• Soil processes active e.g. leaching will wash out nutrients in soils (lower in the profile or out of the ‘system’)
• Vegetation once established will contribute e.g. organic carbon
• Access to water via the water table• Also dew formation (water carried in air
from sea) provides valuable moisture for shallow rooted plants in sand dunes
Sand Dunes• Dune slacks (wet and dry)• Presence of water dependent upon water
table (also from dew and rainfall)• Provides water supply for plants• Also capillary water - accessed via deep
rooting systems• Availabilty of water determines distribution of
plants• Besides vascular plants also presence of non-
vascular such as mosses and lichens
Sand Dunes• Vegetation in dune systems is affected by
grazing e.g. by rabbits• Exposure of soil and sand
to erosion• Affects species structure
and diversity• Also effects of trampling• Large areas of dunes often covered in marram
grass (rhizome fragments and also seedlings)• Sand traps
Sand Dunes• Vegetation: Ammophila arenaria P (marram),
Elytrigia juncea P (sand couch-grass), Honckenya peploides P (sea sandwort), Cakile maritima A (sea rocket), Euphorbia paralias P (sea spurge), Salsola kali A (prickly saltwort) - annuals, biennials, perennials
• Also lichens and mosses• Animal populations e.g. birds, reptiles
(lizards (Lacerta agilis; Lacerta vivipara) and snakes (Coronella austriaca), and insects
Sand Dunes
Sand Dunes• Stabilizing role of marram grass• Dieback of marram can be due
to poor aeration, mineral content deficiency, competition for nutrients, toxicity, natural senescence
• Soil biota (mycorrhizal fungi and nematodes) play a major role in vigour of marram
• Areas of deflation are ideal for the settlement of species such as meadow red fescue - source of water
• In some dune systems shrubs e.g. Sands of Forvie and forest e.g. Culbin Sands
Sand Dunes
Sand Dunes
www-biol.paisley.ac.uk/bioref/ Habitats/Dunes2.htm
http://www.geographyinaction.co.uk/Magilligan/Mag_intro.html
Sand Dunes• Influence of size and also humans
(management, disease)• Affects biodiversity• Machair – April 20th