Eucalyptus: an overlooked alternative to Sitka spruce? Choosing resilient species is vital in a world of climate change, says Willie Beattie.
clImate change aﬀects us all, and sadly some of our most productive and iconic tree species, including larch and ash, are becoming more susceptible to disease during seasonal changes. If we make wrong species choices now it will take a lifetime to rectify our decisions. The fall-back productive species has become Sitka spruce but foresters across Scotland are beginning to consider other species. Sitka will remain a staple for the foreseeable future, but other viable species that will thrive in a plantation and produce a decent crop within a comparable lifespan must now be considered, particularly in the more silviculturally challenging areas of the north and western seaboard. During a search for alternative species, I was introduced to Bryan Elliot of Devon Forestry Consultants with a view to trialling eucalyptus species. My ﬁrst thought was that the only trial sites our clients had available were nutrientdeﬁcient, exposed and prone to frost, but Bryan assured me that he had eucalyptus varieties to suit almost all our site conditions. This spring we began to trial six varieties of eucalyptus on north-west coast sites with varying fertility, exposure levels and some without fence protection from deer. Each variety has diﬀering strengths and growth rates so it will be an interesting exercise to see what does well over the ﬁrst growing season. One of the primary species that establishes well and has great year-round growth characteristics is Eucalyptus glaucescens, a mountain plateau gum that tolerates temperatures as low as –18˚C, and once established within a plantation environment can withstand low temperatures over a long period. At the invitation of Ben Clinch of Darnaway Estate near Inverness, a small coupe of Eucalyptus glaucescens was planted within an existing mixed broadleaf/conifer forest. The trees are only 38 months old and were an average of 3.5 metres tall, the tallest being more than 6 metres. The spacing was relatively open with survival of the ﬁttest the main managerial criterion. The plugs were planted three years ago with no pre-plant preparation on a conifer cutover site and then as a speciﬁc eucalypt trial plot, it was left to its own devices. The spacing is currently in the region of 500 stems per hectare and though openly spaced, apical dominance traits are evident throughout. There are more than suﬃcient numbers and evenly spaced trees to establish a ﬁnal crop, and canopy closure will occur in at least a couple of years’ time. This trial has shown that once established,
Eucalyptus glaucescens is robust and has shown no sign of any frost inhibiting growth factors. The lack of grass competition control, post-planting, is the primary reason for the lack of successful tree numbers. Once established, survival has been consistent over the past few years with the recent cold weather and subsequent drought conditions over 2018 having no impact. Eucalypts, with their rapid growth rates and the relatively high caloriﬁc value of their timber, may be a promising alternative species for woodfuel/biomass production in the right conditions. It is a species entirely happy on many sites in Scotland and extensive establishment is being carried out on a number of locations in 2019. The eucalypts that thrive in Scotand are sourced from Tasmania and Victoria provenances which, in some regions, have a lower average annual temperature range than anywhere in the UK.
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Page 22 | Forestry matters | Summer 2019 | galbraithgroup.com
Eucalyptus glaucescen can tolerate temperatures as low as –18˚C.
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