This is in response to Euan Mason's comments early on height growth
response as shown in "Nelder" trials. (He quoted data from the New Zealand
Forest Research Institute, I used to work there and as they don't appear to
be connected to the network I will have to speak for them.)
Euan is quite correct in his description of early growth responses in
radiata pine. I worked in a section which deal with other species and we
found the same effect with eucalypts,(ie Australian hardwood species, grown
in NZ as an exotic.) That is, there seemed to be a growth response that
initially favoured the closer spacings. This changed with time and the
optimum spacing seemed to move from the densest to less dense stockings as
the years went by. Eventually the densest stockings exhibited less height
(and diameter) growth. We hypothesised that we were witnessing a shelter
effect that at first favoured the densest stockings, then a competition
effect as the trees grew to fully occupy the space then compete for
resources.
There is a published reference to some of this effect:
Menzies, Klomp, Holden and Hong. 1991: The Effect of Initial Spacing on
Growth and Crop Selection of Radiata Pine Seedlings and Cuttings. in
Menzies, Parrot and Whitehouse (eds), Efficiency of Stand Establishment
Operations, Proceedings of IUFRO Sysmposium, NZ FRI Bulletin No 156.
" There was a consistent effect of stocking on growth, with trees being
significantly taller in plots at higher stockings of 600 stems per hectare
or more." ( from the conclusions on page 163 of the Bulletin quoted above,
the paper cannot be summarised in one line and those interested should
follow up by reading the full thing.)
The address of the NZ FRI is PB 3020,Rotorua, NZ.
As to why this effect occurs, I don't know and the theories suggested by
Euan Mason are as good as anybody's.
Ryde James
___________________________________________________________________________
Ryde James | Forestry/Science
Tel: (61+6)249-4330 | Australian National University
Fax: (61+6)249-0746 | Canberra, ACT 0200
|
___________________________________________________________________________
email: Ryde.james@anu.edu.au
___________________________________________________________________________
Mail converted by
MHonArc 1.1.0