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Presentation on theme: "Saltmarshes."— Presentation transcript:

1 Saltmarshes

2 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

3 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

4 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)

5 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

6 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

7 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

8 Saltmarshes

9 Saltmarshes

10 Saltmarshes

11 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

12 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

13 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

14 Saltmarshes Animals:marine invertebrates, deposit feeders, burrowing worms, oligochaete and polychaete worms, crustaceans, ragworms, bivalve molluscs, gastropods, crabs, fish, insects, birds, rabbits

15 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

16 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

17 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

18 Sand Dunes

19 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)

20 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

21 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….

22 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

23 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

24 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

25 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

26 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

27 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

28 Sand Dunes

29 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

30 Sand Dunes

31 Sand Dunes Habitats/Dunes2.htm

32 Sand Dunes Influence of size and also humans (management, disease) Affects biodiversity Machair – April 20th

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