Tree size the biggest driver of harvesting costs

October 19, 2018

By Andrew McEwan

I often ask people during harvesting training and consulting what they think is the most important factor to reduce harvesting costs. The answers can be quite varied, but usually include improving machine availability, improving machine utilisation, producing sufficient volumes to cover fixed costs, monitoring high risk cost inputs, meeting the productivity targets, having good operators and so forth.

These are of course all very important. However, if I had one magic wish to change something to reduce my harvesting costs, I wouldn’t use that wish on anything to do with the actual harvesting operation. I would wish to be able to consistently harvest the potential tree size that that specific site can produce.

As an example; if the potential of a site is to produce a 0.25m3 pulpwood tree, then that is what I hope to discover when arriving at that compartment.

This is of course because tree size is the biggest driver of harvesting costs. I frequently visit plantations and see quite clearly that the tree size being harvested does not match the site potential.

This brings us to the question of how should we manage the success of a silviculture forester?

In my mind it is quite simple. At rotation end, we can measure the actual site yield versus the site potential. If potential matches actual, then we have been successful. If not, then we have gone wrong and we need to determine why we missed the target.
But it is not that simple because the silviculture foresters cannot control all variables. They cannot control the quality of the genetic material that they must use, and often they have to plant sub-standard seedlings, or the incorrect clone and sometimes even species, or they run the risk of having excessive TUP areas.

They also rely on the harvesting operation taking the necessary precautions so as not to cause excessive site damage and disturbance.

Producing a tree with products desired by the market and realising site potential are the fundamental goals of a silvicultural forester’s existence. In order to achieve this, they need good genetic material, good quality seedlings, a site not damaged by harvesting, good site preparation, good silvicultural activities and good protection measures (fires, diseases and pests).
Harvesting only serves to convert the standing tree into a product desired by the market, and to ensure that it is delivered timeously in the quantity and quality desired. If we are going to start realising site potential, we will need to start managing all of these aspects with precision. Our measuring of the implementation of the above mentioned core aspects must be obsessive.
Everyone with a role to play in ensuring that site potential is reached should have that component included as part of their key performance areas. If it is only the silvicultural forester’s activities that are measured, then it is highly likely that site potential is still not going to be realised due to factors such as poor harvesting practice or seedling related problems. Once the full value chain from tree improvement to harvesting is properly measured, it will become clear where the obstacles to achieving site potential are.

A few weeks back I had the privilege of visiting a relatively small timber grower in Limpopo. I was amazed at the good growth, the uniformity of tree size and the quality of the silvicultural activities on the farm. Although I was observing compartments planted with Eucalyptus grandis seedlings, it could have been clonal material like that seen in coastal Zululand. The tree uniformity was remarkable and the growth excellent when compared back to the site potential. The grower was getting the fundamentals of forestry right.

Achieving site potential will not only result in a better return on investment for the silviculture input costs, but will result in a significant reduction of harvesting costs as well. But to achieve this, the entire forestry team has to play their part.

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