3.1.6.4 - British Isles succession and plagioclimax

Lithosere processes and the Ingleborough setting

A lithosere begins on exposed rock. Weathering creates small particles and cracks; colonising lichens and mosses can trap material and add organic matter when they die. Where enough rooting material and moisture accumulate, grasses and herbs establish, followed potentially by shrubs and trees. Increased soil depth, shelter and nutrient supply change competitive conditions. Establishment still depends on dispersal and the rock's chemistry, drainage and exposure.

Ingleborough Complex in the Yorkshire Dales provides a named limestone setting. JNCC describes bare limestone pavement, calcareous grassland, scrub and woodland, including Colt Park Wood where grazing is excluded. Cracks called grikes provide shade, shelter and rooting spaces for woodland plants; exposed surfaces called clints offer harsher conditions. Limestone soils and alkaline chemistry differ from many acidic rock settings.

These neighbouring habitats illustrate environmental controls and management contrasts. They do not prove that every grassland patch is older than every bare rock patch, or that the present landscape is a measured chronological sequence. Restricted soil depth, exposure and continuing grazing can prevent the modelled progression to woodland. Use lithosere processes to explain possible change while distinguishing the observed habitat mosaic from an inferred history.

Hydrosere processes at Sweat Mere

A hydrosere develops from open water towards wetland and, where hydrological conditions permit, more terrestrial communities. Sediment accumulation and plant material can reduce water depth. Marginal and floating vegetation traps sediment and adds organic matter, creating surfaces suitable for later plants. This is terrestrialisation: water becomes occupied by vegetation and accumulated substrate. It differs from paludification, in which previously dry land becomes wetter and develops peat.

Natural England's 1994 citation for Sweat Mere and Crose Mere SSSI in Shropshire describes a particularly clear hydrosere at Sweat Mere. Remaining open water is surrounded by floating reedswamp dominated by lesser reedmace, with common reed also present. Tussock-sedge fen is followed spatially by grey willow and alder carr, with oak and downy birch woodland on drier peat. Carr means wet woodland. The citation describes habitats and their relationship, not a new survey in 2026 or a fixed duration for each transition.

Root tolerance of low oxygen and water-table position determine which plants can establish. If external water inputs remain high, fen or carr may persist rather than becoming dry woodland. Nutrient inputs, water-level changes and cutting can alter the pathway. Crose Mere has different lake and marginal conditions, so its evidence must not be substituted for Sweat Mere's sequence. The SSSI citation's 38.58 hectares refers to the whole designated site, not Sweat Mere's open-water area.

Temperate deciduous woodland and the climax model

Temperate deciduous woodland is a climatic-climax model for many British sites with adequate drainage and soil. Broadleaved trees such as oak lose leaves in the cool season, reducing water loss when growth is limited. Spring light reaches ground plants before the canopy closes; summer shade favours different tolerances. Fallen leaves return organic matter and minerals to soil, while decomposer activity varies with moisture and temperature.