Succession

Darnley Mill and the surrounding area has a rich and extensive industrial history, but today little visible evidence remains on the ground. The mines have disappeared due to extensive land filling and the kilns and railway lines have been overgrown by vegetation or now form well used paths. Darnley Mill itself has been redeveloped and is now the Ashoka Restaurant, although it still retains the old mill building. The rest of the site has been reclaimed by nature through a process of re-colonisation and ongoing natural succession. This process can occur relatively quickly – the last mining operations in Darnley were in the 1960s, yet very little visible evidence can be seen on the ground only 40-50 years later.

Succession is a natural process that happens when plants are able to persist on a site without being disturbed. These plants will either have been deposited as seeds by animals or the wind, or have been present in the soil seed bank before germinating.

The initial population of plants that colonise a site is known as the pioneer vegetation, normally made up of flowers, grasses and annual plants. These plants tend to be fast growing, short lived and spread effectively over long distances by seed, which is normally wind blown. Such plants can usually survive nutrient poor soil conditions and are opportunistic in their colonisation of an area.

The ongoing process of succession facilitates itself as vegetative material dropped by colonisers improves the soil conditions and allows different species to grow. Over time slower growing plant species begin to become dominant, these include scrub (e.g. hawthorn), longer-lived trees (e.g. birch and willow) and perennial plants.

Following scrub vegetation a woodland community evolves, with changes being heavily influenced by soil conditions. These woodlands include even slower growing tree species like oak and Scots pine, which can live for approximately 500 and 350 years respectively. The final stage of succession is known as the climax community, this varies due to soil and environmental conditions. For example in wetter (nutrient rich) areas the climax community consists of willow and alder trees, whereas in dryer conditions it consists of birch and oak woodland. The climax community maintains itself in a state of continual renewal as old trees die, succession begins again in the gaps created. These patches are easily colonised, as neighbouring vegetation spreads and soil conditions are improved. The time scale for this process varies, with a range of factors such as persistence of soil seed bank, isolation, substrate condition and disturbance being important.

The successional process can be seen at Darnley Mill. Currently the area consists of tall herbs, grasses and scrub. The climax community would normally be semi-natural woodland, similar to that in Waulkmill Glen. Due to nutrient enrichment from lime mining the resulting climax community at Darnley Mill may be more alkaline, nutrient rich, broadleaved woodland compared to the current mixed woodland associated with Waulkmill Glen. Different plant communities support different animal communities. Past industrial uses at Darnley Mill may as a result ultimately lead to a greater wealth of species and biodiversity across the country park as a whole.