Report: Trees for steep slopes
Sustainable Forest Solutions
Reviewed by Mike Marden, July 2018.
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Please note that the web report is regularly updated whereas the pdf download above is dated July 2018.
|Species rating *|
|Early growth rate||5|
|Root decay rate||7|
In a nutshell
Very wind resistant but cannot cope with excessively dry conditions. Good potential for erosion control and timber production in steeplands.
Japanese cedar (Cryptomeria japonica) has a fairly narrow conical habit and can become a very large tree at over 45 m in height and 145 cm diameter in New Zealand (Knowles & Miller, 1997). Despite slower early growth than radiata pine, Japanese cedar is one of the largest volume producers of any plantation softwood species and in one 19 year old plantation near Gisborne achieved an annual increment of 39.4 m3/ha, with an average diameter of 38 cm at a stocking of 940 stems per hectare (Knowles & Miller, 1997). Best growth is achieved in warmer, wetter areas of the country such as the central and northern regions of the North Island (Knowles & Miller, 1997). Japanese cedar can tolerate damper soils than many other conifer species (Sampson, 2008).
Japanese cedar is an attractive tree and has been widely planted throughout the North Island and Northern South Island, sometimes in plantations (Knowles & Miller, 1997).
In its natural range Japanese cedar grows at altitudes of between 300 m and 1000 m in areas of fairly high rainfall (Knowles & Miller, 1997). In New Zealand at least 1000 mm of rainfall is required for best growth and although reasonably tolerant of frosts, late frosts can be damaging (Knowles & Miller, 1997). Although altitudes can exceed 600 m, best growth is below this (Knowles & Miller, 1997)
Japanese cedar is a windfirm species and can withstand severe windstorms without windthrow or breakage, although it may not withstand extremely exposed coastal situations (Knowles & Miller, 1997; Sampson, 2008). Japanese cedar is also moderately resistant to snow damage (Cairns, 2012).
Growth rates are likely to be considerably reduced on slip faces devoid of topsoil, where nutrient and moisture deficient (R. Appleton, pers. comm).
Silvicultural management should aim to minimise incidence of bark-encased knots. The species has small branches that self-prune to some extent, and the species is relatively shade tolerant. However, where trees become shaded height and diameter growth is restricted (Knowles & Miller, 1997).
Cutting-grown clones have been selected for good form and vigour (Sampson, 2008).
The suggested optimum regime is for an initial stocking of 1670 stems per hectare (2 m x 3 m), pruned to 6 m in three lifts aiming for a diameter over stubs (DOS) of no more than 16 cm, then thinned at 15 years to 800 stems per hectare, then again at 20-30 years down to 400 stems per hectare for a rotation length of 40-60 years (Knowles & Miller, 1997).
Japanese cedar is easy to establish either as seedlings or rooted cuttings and can be planted out either as well-conditioned bare-rooted stock, or as containerised stock (Knowles & Miller, 1997).
Japanese cedar is generally healthy in New Zealand and pests/pathogens are only of minor consequence (Knowles & Miller, 1997). Sampson (2008) found that "it has no diseases or pests of consequence and soil pathogens do not bother it at all". However, Japanese cedar is palatable to possums and deer or goats can nip off the leading shoot resulting in multiple leader growth (Knowles & Miller, 1997).
Regeneration has been recorded in the vicinity of planted trees but there are no reports of wilding spread (Knowles & Miller, 1997).
Wood of Japanese cedar is soft, low density, stable, coarse-grained and fragrant (Knowles & Miller, 1997). Japanese cedar has a relatively high proportion of moderately durable heartwood, which is red-brown in colour, sometimes with streaks of yellow or dark-brown.
The wood of Japanese cedar is not strong and not hard wearing, but being a decorative timber with good woodworking properties it is suitable for appearance applications. These include decorative panelling, joinery, furniture and ornamental posts and poles (Knowles & Miller, 1997). Japanese cedar heartwood is also suitable for exterior cladding.
In Japan the wood is used for structural applications such as framing and laminated beams. Characteristic strength values have not yet been determined for New Zealand material, nor for fixings. Until these are available Japanese cedar will not comply as a structural timber under the building code (D. Gaunt, pers. comm).
Disclaimer: The opinions and information provided in this report have been provided in good faith and on the basis that every endeavour has been made to be accurate and not misleading and to exercise reasonable care, skill and judgement in providing such opinions and information. The Author and NZFFA will not be responsible if information is inaccurate or not up to date, nor will we be responsible if you use or rely on the information in any way.