Module 7 of 9 · Text
Succession
COMMUNITY - ALL POPULATIONS OF DIFFERENT ORGANISMS LIVING AND INTERACTING IN PARTICULAR PLACE AT SAME TIME
SUCCESSION - CHANGES OVER TIME IN THE SPECIES THAT OCCUPY A PARTICULAR AREA
WHY BARREN LAND BECOMES COLONISED
- GLACIER RETREATS, DEPOSITS ROCK
- SAND PILED INTO DUNES BY WIND/SEA
- VOLCANOES ERUPT, DEPOSITS LAVA
- LAKES/PONDS CREATED BY SUBSIDING LAND
- SILT AND MUD DEPOSITED AT RIVER ESTUARIES
- COLONISATION BY PIONEER SPECIES - E.G LICHEN -
Features of pioneer species
- tolerance to extreme conditions
- ability to fix nitrogen from atmosphere because soil non existent or few nurtrients
- ability to phoptsyntheises, not reliant on another species
- rapid germination of seeds, no period of dormancy
- production of many wind dispersed seeds/spores, can reach isolated area
2. PIONEERS DIE, PUT ORGANIC MATERIAL IN SOI, ALLOWS RECYCLING TO START, INCREASES MINERAL IONS IN SOIL. CAN SUPPORT COMMUNITY OF SMALL PLANTS. E.G MOSSES. ABIOTIC ENVIRONMENT CHANGED,
3. THICKER LAYER OF NUTRIENT DENSE SOIL BUILT UP. SPECIES CHANGE ABITIOIC ENVIRONMENT, MORE SUITABLE FOR ORGANISMS THAT FOLLOW, E.G GRASSES (TERTIRARY COLONISER)
4. CLIMAX COMMUNITY
- TREES
- STABLE STATE COMPRISES A BALANCED EQUILIBRIUM OF SPECIES WITH FEW IF ANY NEW SPECIES REPLACING THOSE THAT HAVE BECOME ESTABLISHED.
- DETERMINED BY MAIN ABIOTIC FACTOR, E.G TREES MANY BNOT GROW ON HIGH MOUNTAINS
- STABLE EQUILIBRIUM WITH PREVAILING CLIMATE
- UK = DECIDUOUS WOODLAND
- LESS HOSTILE, MORE NUTRIENT DENSE, HIGH SOECIES DIVERSITY AND STABILITY,
- MORE NICHES AND HABITAT VARIETY
- LESS HARDY SPECIES CAN SURVIVE
- MORE COMPLEX FOOD WEBS, INCREASED BIOMASS
- BIODIVERSITY DECREASESA AS DOMINANT SOECIES OUTCOMPETES OTHER SPECIES
RECOLONISATION - LAND ALTERED, RETURN TO CLIMAX COMMUNITY MORE QUICKLY DUE TO SPORES/SEEDS IN SOUIL, INFLUX OF ANIMALS THROUGH DISPERSAL/MIGRRATION