The Role of Fir Species in the Silviculture of British Forests

Kastamonu Üni., Orman Fakültesi Dergisi, 2012, Özel Sayı: 15-26 Kastamonu Univ., Journal of Forestry Faculty, 2012, Special Issue The Role of True Fir Species in the Silviculture of British Forests: past, present and future W.L. MASON Forest Research, Northern Research Station, Roslin, Midlothian, Scotland EH25 9SY, U.K. E.mail:[email protected] Abstract There are no true fir species (Abies spp.) native to the British Isles: the first to be introduced was Abies alba in the 1600s which was planted on some scale until the late 1800s when it proved vulnerable to an insect pest. Thereafter interest switched to North American species, particularly grand (Abies grandis) and noble (Abies procera) firs. Provenance tests were established for A. alba, A. amabilis, A. grandis, and A. procera. Other silver fir species were trialled in forest plots with varying success. Although species such as grand fir have proved highly productive on favourable sites, their initial slow growth on new planting sites and limited tolerance of the moist nutrient-poor soils characteristic of upland Britain restricted their use in the afforestation programmes of the last century. As a consequence, in 2010, there were about 8000 ha of Abies species in Britain, comprising less than one per cent of the forest area. Recent species trials have confirmed that best growth is on mineral soils and that, in open ground conditions, establishment takes longer than for other conifers. However, changes in forest policies increasingly favour the use of Continuous Cover Forestry and the shade tolerant nature of many fir species makes them candidates for use with selection or shelterwood silvicultural systems. Supporting evidence is provided by analysis of the regeneration in a long term study of transformation of first rotation conifer plantations. The need to adapt forests to climate change has identified some other silver fir species from southern Europe and Asia as having potential to help increase the resilience of British forests against the impacts of a warmer climate. This paper is the first review of experiments, operational experience with, and the potential role of silver firs in British forestry for more than 20 years. It suggests that previous reviews of the potential role of Abies species have been unduly pessimistic and that there should be an expanded place for silver fir species in British forestry in the future. Keywords: Abies, Silviculture, Provenance, Continuous cover forestry, Climate change Introduction to improve the landscape and provide The four countries of the United Kingdom domestic supplies of timber (House and (England, Northern Ireland, Scotland and Dingwall, 2003). This interest included the Wales) fall within the Atlantic zone of north- trialling of species that were not native to the western Europe with a native woodland British Isles and which were introduced from cover composed mainly of temperate continental Europe, from North America or broadleaved species (e.g. Quercus spp., from other parts of the world. The early years Fraxinus excelsior, Betula spp.), although of the last century saw the start of concerted there are outliers of the boreal forests in the attempts to restore forest cover through Scots pine (Pinus sylvestris) dominated areas afforestation of marginal agricultural lands. of northern Scotland. Apart from Scots pine, The expansion of the forest area has no other European conifer of commercial continued until the present day so that the importance (e.g. Norway spruce – Picea forest area of the United Kingdom now abies; European silver fir – Abies alba) is amounts just over three million hectares or native to the British Isles. All four countries 13 per cent of the land area (Forestry share a similar history of centuries of Commission, 2011a). The primary aim of the deforestation and unsustainable forest early decades of the afforestation programme management (e.g. Smout, 2003) so that at the was to produce a timber resource for beginning of the twentieth century forest industrial purposes and the programme was cover was very low, being less than five per based on the use of fast growing and mostly cent in Great Britain (Forestry Commission, non-native conifer species which could 2011a). However, by the early years of the tolerate the exposed sites and impoverished seventeenth century, there was increasing soils where planting was concentrated. The interest in the creation of woods and forests result has been the transformation of the 15 Kastamonu Üni., Orman Fakültesi Dergisi, 2012, Özel Sayı: 15-26 Mason Kastamonu Univ., Journal of Forestry Faculty, 2012, Special Issue British forest resource from broadleaves to (also western red cedar - Thuja plicata, and conifers in around 50 years (Mason, 2007). western hemlock - Tsuga heterophylla) with Thus the non-native conifer Sitka spruce more widely used species such as Sitka (Picea sitchensis) is now the major tree spruce and Douglas fir (Pseudotsuga species in Britain, particularly in Scotland, menziesii) (Aldhous and Low, 1974). The and accounts for a substantial proportion of results suggested that both Abies species, but the domestic timber supply. particularly grand fir would grow as fast as The most authoritative account of the or faster than Sitka spruce, especially on species trialling in the early decades of the more fertile and sheltered sites in western afforestation programme was provided by Britain. Grand fir was found to be the fastest MacDonald et al. (1957) who proposed that growing commercial conifer in the British an introduced tree species has to go through Isles with an estimated productivity of 32 m3 three stages before it can recommended for ha-1 yr-1 on favoured sites (Aldhous and Low, widespread operational use in forestry. 1974; Table 1). However, these benefits were These stages are, in turn: the planting of a offset by concerns over higher establishment candidate species as individual trees in costs because of slow initial height growth arboreta and parks where the specimens can and over the relatively low density of the be given careful attention; the establishment timber of both species, which was of small plots of more promising species in compounded by a comparatively high forest gardens where comparative incidence of drought cracks. performance can be evaluated; and finally the Partly as a consequence of these concerns creation of trial plantations of the best and also because of the increasing species on a wider range of sites to determine availability of genetically improved strains of performance under more testing conditions. Sitka spruce (Lee and Matthews, 2004), Amongst the genera covered in that review interest in the use of Abies species in British was the Abies genus where the performance forestry has remained at a relatively low of 34 members of the genus was discussed level since the 1970s. This is despite with three (European silver fir - A. alba, information becoming available (Lines, grand fir - A. grandis, and noble fir - A. 1979) to suggest that correct provenance procera) being considered of silvicultural choice could speed up early height growth importance for British forestry while four and so reduce establishment costs, while more (A. amabilis, A. concolor, A. Kerr (1999) argued that using European nordmanniana, and A. veitchii) were thought silver fir as a shade tolerant component of to have commercial potential (MacDonald et mixed species stands should reduce the risks al., 1957). They considered European silver of damage to this species from Adelges fir to be ‘an example of an exotic [species] of nordmannianae. More recently, there has some importance in its day which is no been interest in increasing tree species longer planted’ due to the serious damage diversity as part of a strategy of adapting caused by the aphid Adelges nordmannianae. forests to projected climate change (Read et However, the high productivity of grand fir al., 2009). Thus a number of Abies species was felt likely to encourage the use of this (A. alba, A. amabilis, A. borisii-regis, A. species on better quality sites while noble bornmuelleriana, A. cephalonica, A. cilicica fir’s tolerance of exposure would find it a and A. nordmanniana) have been specifically place in the silviculture of upland regions of mentioned as having a potential role in an Britain. adaptation strategy for British forests (Read These findings resulted in an increase in et al., 2009; Tables 6.5 and 9.1). There is the planting of grand and noble fir so that by also greater recognition of the potential role the mid 1960s there were over 4000 ha of of a wider range of alternative silvicultural these species in British forests (Aldhous and systems to clear felling in support of Low, 1974). Therefore, a further review of multifunctional forestry (Mason, 2007). these operational trials was carried out to These trends have resulted in increasing compare the performance of and financial interest in the potential role of Abies species return from plantations of grand and noble fir as a component of the future forests in 16 Kastamonu Üni., Orman Fakültesi Dergisi, 2012, Özel Sayı: 15-26 Mason Kastamonu Univ., Journal of Forestry Faculty, 2012, Special Issue Britain (Wilson, 2011). However, much of contained between 9 and 14 different species the information to support the case for an and species mixture combinations in a increased use of Abies species in British randomised block design with three forestry is scattered and anecdotal: the replicates of each treatment and

Load more