Red Cedar Inventory

**Bob Whitworth** · 5th March 2007, 08:47 PM

Red Cedar Inventory.

On my 125 acre [50 ha] farm I grow timber. It was previously cleared and I started planting in 1975 with mostly hoop pine, Gympie messmate and Queensland maple. I also have some natural regeneration of silver ash and red cedar.

In 1989 I sold one of my cedar trees and did quite well out of it. I then did an inventory of my red cedar trees just to see what I had and also to do some silvicultural treatment around each tree. By last year my notes were becoming quite a jumble and I decided to do a remeasure. This time I would number each tree as I measured it and place its position on a locality map. I have by now mostly completed the survey although I haven’t measured a couple of areas which are rather difficult. I registered all trees greater than 20 inches girth [16cm diameter] which is quite small and smaller than even I would saw up. The smallest that I will have sawn is 24 inches [20cms diameter].

These are the results. So far I have measured 658 trees. These girths are then considered as a circle and converted to an area giving a total [the word is] basal area of 402 square feet [37m2]. The stand table is made up of 20 inch class, 380; 30ins, 167; 40ins, 73; 50ins, 22; 60ins, 12; 70ins, 4; giving a total of 658 trees. As can be seen, my forest has a high proportion of small trees making it more the potential of timber than actual valuable timber now. The value is naturally in the larger trees.

The trees are very variable. Some are open grown in good sites and are putting on a lot of valuable diameter growth while others on poorer sites and with much severe competition from perhaps hoop pine, are growing much slower and have a form that is tall and thin. Consequently I haven’t taken the basal figure and estimated from this a volume because that is much more unreliable but I’d say for sure that I have well over 100 cubic metres of timber and probably approaching 200 cubic metres. A casual look at my forest, red cedar doesn’t seem all that prevalent but it is there in to me very significant volumes and at least growing at an acceptable rate if probably not that fast in most circumstances. Maybe the cedar component of my forest is growing at 10 cubic meters a year including recruits.

Drought is also a serious problem and some trees have died up on the slope and others have a developed a dead top which is very damaging for the formation of good timber. My biggest tree, a tree of over 100 inches girth, had developed a dead top and so I recently cut it and the wood from this is available including plenty of give away pieces. Others have died from lightning strikes and decay coming in from dead tops and old branch stubs.

Conventional forestry practice says that red cedar cannot be grown commercially. I believe that these figures from my inventory show that red cedar can in some circumstances be considered a commercial crop. Maybe it isn’t the tree that gives the quickest results but if the resource is there, it is worth knowing about and looking after.

**AlexS** · 5th March 2007, 10:11 PM

Interesting Bob. I'd heard that RC couldn't be grown densely enough to be commercial because of cedar cut moth, but you obviously have it growing with many other species. I'm not sure what the mechanism is, but maybe having a variety of species may harbour predators of the cut moth. Sounds like you have a worthwhile resource there, anyway.

**dadpad** · 6th March 2007, 12:58 AM

Bob have you thought about fertilising to see if it increase growth rates?
Sacrificial thinning may be worthwhile around those trees where growth rates are slower. You would need to check with someone more used to yourlocality but tradition would have us believe that each site can only support a given volume of timber. This is related to site fertility and rainfall. It matters not if you have 300 skinny trees or 100 fat trees the basal area the site will support stays the same.

By measuring a sample of trees (2% of stand is statistically significant) each year you can gauge growth rates. The standard thinking is that when trees cease to stack on diameter it is time to get rid of some.
Did you measure at breast height? (1.3 meters)

Mean annual increment (MAI) is the average growth per annum over the lifetime of the tree (diameter/years). Current annual increment (CAI) is the growth over the last 12 months. when current annual increment is less than or close to mean annual increment it is time to thin.

**Bob Whitworth** · 7th March 2007, 09:03 PM

Replies.

1/ Damage from the tip moth is a problem but it only seems to be serious when the trees are rather small. Yes it can seriously stunt their growth when young.

2/ I could fertilise the RC but access for many of the trees is difficult. I have fertilised my QM and they probably would like even more fertiliser.

My RC trees are scattered over my farm. I should do more un merch thinning but I tend to hold back hoping that I can find a market for the small diameter trees. I also haven’t worked out my preference between RC, QM, GM and HP.

I do measure by sample my plantations but with the RC, I need to go and check each tree to see if it needs any silvicultural assistance. It has been about 15 years since I have looked at some of the trees. While visiting each tree, I may as well measure it and allocate it a number and plot its position. A large tree can be quite valuable. Yes I measure at 4ft 3 ins which I think is 1.3m. I’ve probably measure about 90% of my RC resource.

About the CAI/MAI crossover point, this is only valid for volume while for me, larger trees are much more valuable than smaller ones. I intend to grow the trees as large as possible but this is subject to them having satisfactory growth and health. So far it is quite a problem because they seem to get more problems as they get older. Healthy fast growing trees are the best. They can also quickly grow over old branch stubs as well. The problem with opening up the forest too much is that it allows it to develop an even more vigorous lantana understory. A reservoir of large trees with which I can supply special orders for wide boards of quality timber is my aim. It may take many years, but I’ve made a start.

**dadpad** · 7th March 2007, 10:02 PM

Rob I hesitate to give you advice as I can't see your trees, land or experience your climate, however it may be that the die back problem could be solved by trace element or fertiliser application.
You certainly seem to know a bit about tree growing so any suggestion I make is general in nature.

Boron copper zinc and manganese are all vital trace elements. Although it has not yet been proven I believe boron may have an insect protective role. Boron is a well known "insecticide", or it may be that because the trees grow better with a reasonable supply of boron available they recover quicker from insect attack. Boron definitly promotes good straight growth in young trees with less double leaders.

It may well be that your part of the country does not suffer from boron deficiency but If you haven't checked this angle out it may be worth investigating.
Just rereading your post it does sound like drought stress though. well fertilised (i include correct trace element in that) will be more tolerant of drought stress.

I'd be interested to know if you had some trace element included when you fertilised. In particular boron and copper.

**Bob Whitworth** · 10th March 2007, 10:44 AM

Yes I have heard of the benefits of trace elements including boron. I know for sure that I’m deficient in boron because when I grow a few papaws they need the addition of boron. Most of my soil is granite derived and it is prone to being nutrient poor. It is also usually well drained especially on the slopes and I think it is the dry conditions in these situations that is the primary problem.

When I fertilised the maple, I didn’t add any trace elements although in retrospect I should have done so. Maple are very demanding requiring good well drained soil with plenty of moisture and can only be recommended in the best of sites. I also have a lot of silver ash as natural regeneration as well. It can handle the dryer conditions but is a bit of a problem tree because of proness to blue stain and lyctus borer.

Yes I did study forestry many years ago.

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