Presentation on theme: "Priseres K.I 4 Plant successions from bare ground are known as priseres. There are four main types of priseres: Xerosere (Dry) Lithoseres where the plants."— Presentation transcript:
Priseres K.I 4 Plant successions from bare ground are known as priseres. There are four main types of priseres: Xerosere (Dry) Lithoseres where the plants colonise bare rock e.g. after glacial retreat, Snowdonia or a rocky shore, Oxwich Point, Gower or a newly created volcanic island (e.g. Surtsey, Iceland) Psammosere where plants colonise coastal sand dunes e.g. The south Gower - Oxwich Bay. Hydrosere (Wet) Hydroseres where the plants colonise fresh water, as at a pond margin e.g. Llanfihangel Gobion, Monmouthshire - ox-bow lakes Haloseres where plants colonise salt marshes and sea estuaries e.g. The North shore of the Gower, Lanrhidian salt marsh
Prisere : complete succession from initial inorganic (1) too wet/dry conditions to climatic climax vegetation (5?). e.g. Psammosere 1 5?
Initial conditions either too wet Or too dry Or too alternating wet / dry Possibly with salt Therefore only a few plants can tolerate these harsh conditions No soil BARE INORGANIC SURFACE Mosses and lichens COLONISERS PIONEER COMMUNITY
Climax vegetation is the vegetation which establishes itself on a given site for given climatic conditions (in the absence of human action) after a long time Climatic climax vegetation Witham Woods Oxfordshire
Climax Vegetation Plagioclimax subclimax (after deforestation, ploughing, burning Secondary succession Primary succession New inorganic (non-vegetated surface) Biotic subclimax Edaphic (soil) subclimax THE POLYCLIMAX THEORY Primary succession natural interruptions in primary succession Retrogressive succession due to disturbance (natural or human) Secondary succession
Seral Stages – temporary stages which develop over time leading to plant succession Time goes by (100s of years) or different spatial positions at one time
Subclimax An arresting factor halts development e.g. biotic (rabbits, goats, sheep: graze the land and prevent tree growth) e.g. edaphic (salty soil – hinders tree growth) Birch tree subclimax
Primary Succcession on heather moorlands (U.K.) Mosses, lichens, hardy grasses Grasses, herbs, some heather Tall shrubs e.g birch Pine, hazel Oak forest Post glacial recolonisation in the lower hills
From Oak Trees to Heather Moorland 1.After the Ice Age the primary succession to heather moorland occurred. 2.Humans cleared the trees for farming. The soils lost became leached and lost their fertility. The acid soils did suit heather. 3.Young shoots of heather are ideal for sheep grazing and the moorlands are used for hill farming. The grazing prevented the regrowth of shrubs and trees. 4.Periodic burning (muirburn) removes old wood, releases nutrients and encourages new shoots. The heather is maintained as a plagioclimax.
Oak forest PLAGIOCLIMAX Deflection by humans : cutting, burning, grazing Blanket bog Poor drainage Grassy heaths overgrazing burning Heather moorland Liming, fertiliser Improved pasture or arable farmland SHRUBBY HEATH