The influence of evergreen coniferous nurse-crops on the field layer in two woodland communities.
Abstract
Field observations and laboratory tests were made in 1984-87 on the effects on the field layer in oak/bracken/bramble woodland and ash/maple/mercury woodland after clear-felling and replanting in 1957-58 with either sessile oak (Quercus petraea) - nurse crop Norway spruce (Picea abies) and Douglas fir (Pseudotsuga menziesii) - or beech (Fagus sylvatica) - nurse crop larch (Larix decidua), at a National Trust woodland in Surrey, UK. Conifers reduced species content of the field layer; deep shade (particularly from March to May) and accumulation of litter and humus are shown to be responsible for field layer changes. Groups of oak were important sites for survival of some species (Hyacinthoides non-scripta), but others, such as Anemone nemorosa, were apparently eliminated. Composition of field layers from originally different woodland communities converged. High densities of dormant seeds persisted under nurse-crops for at least 25-30 years; seeds of species from the community present when coppicing or clearance was done predominated, and some woodland species (such as Luzula pilosa, Teucrium scorodonia) persisted, although many did not. Following nurse-crop removal, processes in the re-establishment of the field-layer are discussed.