Eucalyptus Biomass trials

Tray of Eucalyptus nitens ready for planting. The seedlings for the trial were raised at a commercial forestry nursery in Portugal, using seed sown in December 2000. Seedlings were delivered in late May 2001.	General view of part of the trial site on 3rd September 2001, just over 4 months from planting of the major part of the trial. The site was formerly planted with apples, and the eucalypts were planted in twin rows within the original strips that had been planted with apples. The inter-rows were maintained as mown grass. Treeguards were used primarily to facilitate chemical weed control in the planted strips.
General view on 27th November 2001 of part of the site planted on 28th May 2001.  Eucalyptus gunnii on the left, E. nitens on the right. The trees ceased growth around this time.	Eucalyptus nitens on 14th June 2002, 54 weeks after planting.
Eucalyptus nitens on 16th July 2002, 59 weeks after planting, taken from the same point as the photo on 14th June. Note the very rapid growth since then. No further weed control was necessary within the E.nitens planting strips after July 2002.	Eucalyptus nitens on 19th September 2002, less than 16 months from planting! This species achieved canopy closure during August, and the grass inter-rows became suppressed by the trees following this.
Eucalyptus gunnii on 19th September 2002, with E.nitens behind. Note the much lighter canopy of the E.gunnii; this does not suppress weeds readily and further chemical weed control was carried out.	There was a gale on 27th October 2002. The majority of the trees were unaffected but a few were blown over. This photo shows a stem section of one of the windblown trees – firewood logs in 17 months!!
Eucalyptus nitens in snow, 7th January 2003. The trees were unaffected by the snow and subsequent frosts. The tallest tree was 5.7m! Grass had largely disappeared from the inter-rows and a leaf litter had started to develop.	Eucalyptus gunnii in snow, 7th January 2003
The Eucalyptus nitens on 30th November 2004 , 3.5 years from planting	Inside the Eucalyptus nitens stand on 9th June 2005 , just before half of the stand was thinned
Logs from the thinning carried out on 9th June 2005 . The logs have been used as firewood. They had air-dried fully by October 2005.	The Eucalyptus nitens on 4th December 2006, 5.5 years from planting. The stand was windfirm in the gales experienced in winter 2006/7.

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General comments (January 2008)

The main parts of the trial provide a dramatic illustration of how potentially vigorous tree species can respond to being grown in the UK on a good quality lowland site using good standards of silviculture.

Growth data are being recorded.   At 47 months (3rd May 2005), the E. nitens were at least 12m tall, and average survival of trees from the two sources was 81%. The mean annual increment (MAI) of this species at this time was 24 m3/hectare/year, overbark.  Assuming that the basic density of the wood plus bark at this age is 420 kg/m3, then this represented a stem dry matter annual increment of 10 oven-dry tonnes (odt)/hectare/year.

In June 2005 half the area of E. nitens was thinned, removing 50% of the volume/60% of the trees, in order to examine the response of the remaining trees and also demonstrate that a useful yield of woodfuel can be obtained just 4 years from planting.   The two areas were measured 24 months later, in June 2007.  At this time, the unthinned area had grown at an MAI of 30 m3/ha/year, which equates to 12.7 odt/ha/year assuming a basic density of 430 kg/m3.  The current annual increment (CAI) for years 5 and 6 was 41.7 m3/ha/year.  There was no yield benefit or penalty from the thinning carried out in 2005, but a useful quantity of firewood logs was obtained from the thinnings. 

The data to date indicate that the Eucalyptus nitens stand is growing at a rate comparable to those of locations where the species is grown commercially on rotations of 8-10 years.   The growth rate of the unthinned trees in the six years from planting is likely to be a UK record.

Growth of the E. gunnii in the trial is also good, but substantially less than that of the E. nitens. Also, the form of the E. gunnii on the site is generally poor.

While the results to date from this trial are highly encouraging, it should be recognised that direct extrapolation of these results to other species, site types and regions is not straightforward. Furthermore, the economics and economic risks associated with such crop models need careful examination before they can be recommended for general use.

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