ecological succession Flashcards
define succession
changes to the structure and composition of a harsh ecosystem as new species colonise the area causing changes to abiotic factors
what are the names of the stages of succession for water, rock and sand
1) hydrosere
2) lithosere
3) psammosere
what is a pioneer species
the first species to colonise a harsh environment
outline succession
1) a species adapted for survival of harsh condition’s colonise the extreme habitat such as bare rock- this is a pioneer species
2) as time passes populations increase as pioneer species cause changes to abiotic factors increasing suitability for new species which couldn’t survive before
3) as new species colonise changes continue increasing suitability even more so new species colonise
4) this process of new species colonising, thriving and then dying out continues until a community of species develops which remains dominant as long as the climate doesn’t change- a climax community is reached
what is a sere
the name given to the sequence of stages in ecological succession
explain the process of a hydrosere formation
1) pioneer species colonises a water body such as algal spores brought via flying birds or insects
2) lake edges start colonising rooting plants but water too deep for such plants so only floating plants colonise
3) colonisation of new plants increases food supply increasing animals which colonise
4) plants grow and die filling lake with DOM as well as soil causing water to become shallower
5) continues until shallow enough for rooting plants to survive- emergent plants outshade submerged plants so they die
6) as sediments increase water recedes and aquatic species decrease
7) soil accumulates until it can support large trees that survive in waterlogged soil
8) transpiration of trees removes water so soil dries out
9) now it can be colonised by tress such as oak with denser canopies shading out smaller plants
10) a climax community is reached
what is a plagioclimax
occurs when human activities cause the deflection of a climax community as the activity prevents the continuation of succession
define a climax community
a self-perpetuating stable ecosystem which has reached dynamic equilibrium therefore no further changes occur
what will happen if the human activity which produced the plagioclimax stops
secondary succession will eventually re-establish the climax community
how are plagioclimax habitats maintained- provide an example
1) usually maintained via the traditional activities which created them eg
- hay meadow= mowing
- lowland heathland= grazing/burning
define secondary succession
the change in structure and composition of an ecosystem which has previously been colonised but destroyed for some reasons such as forest fires or human activities
why does secondary succession occur faster than primary succession
- the soil is already present
- seeds remain undamaged beneath the soil
- species are already present in surrounding areas
