EQ1 Flashcards
Vegetation Stabilisation of Sediment
Vegetation can stabilise unconsolidated sediment + protect it from erosion
-plant roots bind sediment together=harder to erode
-plant stems+leaves covering ground surface protect sediment from wave erosion+tidal/LSD erosion when exposed at high tide
-prevent wind erosion at low tide
vegetation stabilisation of sediment
increases rate of sediment accumulation
- Plant stems + leaves interrupt flow of wind + water, reducing their velocity + encouraging deposition.
- When vegetation dies it adds its organic matter (hummus) to the soil.
- Unconsolidated sand, silt + clay, freshly deposited at the coast r v harsh environment for plants.
Vegetation Stabilisation of Sediment
coast is harsh enviroment for plants bc:
-exposed to high wind speeds at low tide.
-Lack of shade =high diurnal (daily) temp range.
-submerged in salty water for half the day.
-evaporated sea spray makes sediment saline.
-Salt is highly porous + permeable, so rain water drains quickly- so plants have little fresh water.
-Submerged sediment has its pores saturated with salt water - there’s no oxygen for plant roots to respire with.
-Sand lacks nutrients.
Vegetation Stabilisation of Sediment
pioneer plants
-first plants to colonise freshly depositedd sediment (in embryo dunes)
-they modify enviroment:
1. Stabilising sediment
1. Adding organic matter that retains moisture, contributes nutrients+provides shade.
1. Reduce evaporation in sand.
-Now, slightly less hardy plants can colonise the sediment. They add more organic matter, stabilise existing sediment and trap more.
plant succesion
-the changing structure of a plant community over time as an area of initially bare sediment is colonised.
-so its how diff plant communities occupy an area over time
-seral stage=each step in plant succesion
-end result of plant succesion is called a (climatic) climax community
-PS on sand=psammosere
types of plants on sand dunes
-Xerophytic: withstand dry weather to colonise bare sand
-halophytes: withstand high concentrations of salt from sea water
1.embryo dunes form when litter=barrier to trap sand
2.its colonised by X pioneer plants (lymegrass, sea couch grass+sea rocket)they stabilise sand +allow marram grass(mg) to colonise
3.MG forms yellow dune
4.as MG dies it adds hummus to sand=makes soil.= grey dune(fixed)- plants like gorse
5.dune now above high tide level, so rain washes salt from soil=less saline
6.soil=imporved nutrients+moisture retention so non-xerophytic plants colonise dunes until climax plant community form=in equilibrium w climate+soil conditions
6.-eg bramble,pine,birch
marram grass
-waxy leaves: limit water loss via transpiration+resist windblown sand abrasion
-roots: can grow 3m to reach down water table+stem can grow 1m a year to avoid burial by deposited sand
-allow dunes to grow, rapidly forming yellow dune (mainly sand not soil )
-reduce waterloss via transpiration+withstand temps upto 60*
blowouts
-gaps formed when storms erode sections of yellow dune via wind/wave action
-overtime, deposition of sediment+recolonisation of veg rebuild dunes damaged areas
-but, wind may have blown away dry sand, reaching heavier wet sand at water table. marshy dune slack may form w/fresh water plants- marsh orchids
Salt Marsh Successional Development
-halophytic plants=adapted to saline conditions to colonise mud
-halosere=plant succesion in slaty water
* Estuarine areas are ideal for salt marshes because:
-they’re sheltered from strong waves (so mud + silt can be deposited)
-rivers transport supply of sediment to river mouth, which may be added to by sediment flowing into the estuary at high tide
halosere
salt marsh succesion
- mix of fresh+sea water in estuary=clay particles stick +sink=flooculation
- blue-green algae+gut weed colonise mud, exposed low tide
- algae binds mud,adds organic matter+trap sediment
- -as sediment thickens, water depth= reduced+mud covered by tide for less time
- halophytic glasswort+cord grass colonise, marsh=still low+covered by high tide
- accumulation of organic matter+sediment^height of marsh until its only covered by spring tides
- high marsh=colonised by less hardy plants: sea: aster,laveneder, thrift+scurvy grass
- rain washes salt out high marsh allowing land plants to colonise
- continues til climax community(cc) is reach
-in uk CC=decidous oak fores or conifeous pine forest in n scotland
salt marsh succesion
better version
▪ Algal Stage - Gut weed & Blue green algae establish as they can grow on bare mud, which their
roots help to bind together=flocullation
▪ Pioneer Stage - Cord grass & Glasswort grow, their roots begin to stabilise the mud allowing
the estuarine to grow.
▪ Establishment Stage - Salt marsh grass & Sea asters grow, creating a carpet of vegetation and
so the height of the salt marsh increases.
▪ Stabilisation - Sea thrift, Scurvy grass & Sea lavender grow, and so salt rarely ever gets
submerged beneath the marsh.
▪ Climax vegetation - Rush, Sedge & Red fescue grass grow since the salt marsh is only
submerged one or twice a year.
dune lifecyle
Everyone Follows Shrek For Money
- mitigation: form when sand is obstructed +continous supply allows to build up+form embryo dune
- embryo: youngest, mainly in summer+wash away in winter. pioneer species here-stabilise+colonise
- foredune: taller, marram grass stabilises it+more veg cover. more resilient to storms so can stay in position for yrs
- semifixed: pretty stable, still some exposed sand, still accrete sand from beach+sand can be blown over ridge+inand to grow dunes behind=yellow dunes
- fixed: grey dunes, build up more hummus, better at holding water, so support large shrubs. sand can blow thru them via blowouts+SFD+wind
- mature: furthest from beach, oldest+little exposed sand, lots of broken down organic matter=accesible to large plants+trees
how veg stabilises coastal landforms
▪ Roots of plants bind soil together which helps to reduce erosion=flocullation
▪ When completely submerged, plants provide a protective layer for the ground and so the
ground is less easily eroded.
▪ Plants reduce the wind speed at the surface and so less wind erosion occurs.
