Closed-canopy ancient woodlands, as distinct from wood pasture, usually contain a proportion of old trees but the growth-habit of trees in closed canopy makes them less likely to reach a great age. Such woodlands can, however, contain a high proportion of veteran trees of lesser age, where management practices have allowed these to remain.
In many cases, ancient woodlands have been planted up for commercial forestry. These areas, which are known as Planted Ancient Woodland Sites (PAWS), often contain ancient trees. This is especially true of former wood pastures which, despite their great cultural value, may have been especially vulnerable because trees could easily be planted amongst their open canopies. Ancient trees in PAWS eventually tend to become smothered by competing vegetation. Research undertaken by the Oxford Forestry Institute on behalf of The Woodland Trust has indicated that more than half of the PAWS in Britain may contain such ‘drowning’ ancient trees PAWS often contain just a scatter of ancient trees but such trees were frequent in 7% of the sites sampled.
In many PAWs, relict ancient trees, coppice stools and fallen decaying wood — hidden away or on the edges of plantations — are invaluable refuges for an amazing proportion of rare and threatened species, especially fungi, insects, bats and lichens. The old trees in themselves provide real ‘hotspots’ of species-abundance and diversity and their crowns often cast less shade than the ‘matrix’ of planted trees, allowing the survival of an understorey and of ground flora, together with the associated animals and fungi. Even stumps of large trees can be important, representing the tip of the iceberg of underground reservoirs of biodiversity. And in four out of ten sites surveyed, intact felled trees remained from the previous Ancient Semi Natural Woodland.
Restoration of sites with ancient trees will require special care, since such trees and decaying wood habitats are very sensitive to rapid changes in their microclimate.