Restocking with broadleaved species during the conversion of Tsuga heterophylla plantations to native woodland using natural regeneration

Abstract

The removal of conifers planted during the twentieth century on sites that had been woodland for many centuries, with the intention of restoring native broadleaved species, is an important aim of forestry policy in Great Britain. Current guidance generally advocates gradual removal of plantation trees using continuous cover silviculture and restocking by natural regeneration, but methods are largely untested. This study investigated natural regeneration of trees and shrubs at sites where western hemlock had been established either pure or in mixture with native broadleaved species. Western hemlock had been cleared from 70% of the sites. There were c. 10-300 stems ha -1 providing canopy cover of 10-90%; the predominant broadleaved canopy trees were ash, beech, birch and oak. The ground flora of all sites was species poor; bramble was the predominant vegetation type overall, but grasses, rushes and shrubs were relatively more abundant on open sites. A total of 15 native tree species were regenerating, birch was most common and at most sites there were few valuable broadleaved timber species. Although combined numbers of seedlings and saplings varied from 200 to 20,000 ha -1 , large areas of most sites had few regenerating trees and \10% of their area was becoming restocked with timber species. Relationships between seedling numbers and site characteristics were complex and varied with species, but there was a consistent positive relationship between the presence of nearby parent trees and the frequency and abundance of seedlings. The results indicate that the current reliance on natural regeneration may be unwise especially for those broadleaved species such as oak and beech which are valued for their timber.

Effects of clear-felling versus gradual removal of conifer trees on the survival of understorey plants during the restoration of ancient woodlands

“…The potential value of restoration is supported by the finding that ancient woodland features remain extant, if in poor condition, within most PAWS , and therefore provide a practical basis for restoration (Thompson et al, 2003;Harmer et al, 2011). Several categories of features are recognised; ancient woods have distinctive assemblages of species (Peterken, 1974;Kimberley et al, 2013), habitat characteristics and cultural artefacts (The Woodland Trust, 2009); for example woodland specialist flora, old trees and associated dead wood communities -especially on sites with a history of wood pasture (Hodge and Peterken, 1998), woodland archaeology (Rackham, 2003), and distinctive soil profiles (Ball and Stevens, 1981).…”

“…Since the 1970s, the important role of disturbance in forest ecosystems has been recognised and many http forest restoration techniques mimic natural disturbances such as fire and wind damage (e.g. Harmer et al, 2011Harmer et al, , 2013. In addition, restoration can also retain features such as deadwood (Lindenmayer et al, 2012), rely on natural regeneration from the seedbank (Hirata et al, 2011) or on planting of native deciduous species (Truscott et al, 2004;Madsen and Löf, 2005;Wang et al, 2010).…”

Relative contribution of ancient woodland indicator and non‐indicator species to herb layer distinctiveness in ancient semi‐natural, ancient replanted, and recent woodland

“…The potential of PAWS to recover the flora of ASNW through restoration (Pryor et al, 2002;Harmer et al, 2010;Bergès et al, 2017) F I G U R E 3 Beta herb layer species composition of: (a) Ancient Woodland Indicator (AWI) species and; (b) non-AWI species. Non-metric Multi-Dimensional Scaling with Jaccard distance.…”

New Silvicultural Treatments for Conifer Peri-Urban Forests Having Broadleaves in the Understory - The First Application in the Peri-Urban of Xanthi in Northeastern Greece

“…Moreover, in the thinning of the broadleaf trees in the lower stories, the best trees that are going to be favored are going to be the robust dominant having large dimensions trees, which will give strength and stability in the stand in the future. In Great Britain, it is considered that the fast conversion of conifer plantation to woodlands of native broadleaved species through clear cutting treatments under certain ecological conditions can be more preferable compared to the gradual removal of plantation trees [25,28,29].…”