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There are many things to consider for managing land following the harvest of a tree crop, but the first is how to manage the coppice - the stems that naturally regenerate from the base of a harvested tree
Many Eucalyptus species coppice readily and overseas, large areas of blue gum plantations are actually managed in short rotations as coppice. It is generally accepted that a tree grown from coppice will produce greater yields than a seedling of the same age as the stems grow from a large and well-established root system.
There are three post-harvest options for the management of these types of plantations:
Clearing Coppice to revert to farmland
There are a number of methods being trialled to remove coppice and stumps post harvesting to return the area to farmland. Stumps have been mulched, some burnt and pulled out, some coppice has been killed off with herbicide with the slash pushed up into winrows for burning and some has been left to grow. More details will be available after our field day in May 2017
Coppicing involves a shoot reduction operation and removal of trash from the stumps.
Disturbance to the structure and function of a tree during harvest will result in some deaths. If coppicing, harvest operations must maximise the survival of stools (living stumps) from which coppice grows. Harvest timing affects stool survival and cutting in autumn is ideal unless the area is prone to frosts, when felling should be delayed until late winter. Cutting in summer will delay sprouting and increase the chance of the stool drying out and may also lead to the separation of bark from the stool.
The ideal stool should be 10 to 20 cm high, with a smooth surface on a slight angle (to shed water) with good bark attachment. Trash can be used to protect the stools while harvesting of nearby trees takes place, but should be removed before the coppice shoots begin to appear. A low-cut stool will direct growth into more choice stems which are stronger and less prone to wind damage.
Spreading trash is preferred so it acts as a mulch. Although trash retention may cause access problems and a fire hazard, it is desirable as it retains nutrients, conserves soil moisture and minimises erosion. Access problems can be partly overcome by directing the bulk of the trash into alternate rows
By pruning unwanted stems, growth can be channelled into selected stems, giving them a greater chance of survival to harvest. The ultimate aim is to maximise the wood volume of the utilisable stems and it is recommended that one or two shoots per stool are retained, with the following considerations
Current knowledge suggests it is best to decide the number of shoots to be retained for each individual tree by considering in combination:
Two shoots should be retained if:
Shoots should be removed when they are about 2 m in height (about 18 months of age after harvest in a typical area), when shears (rather than chainsaws) can still be used and the dominance of the selected stems limits new shoots.
Blue gum is capable of coppicing over many rotations. In the Nilgiri Hills in India it has been successfully grown for fuel wood in rotations of 10 years for the past century.
Extracts from Managing blue gum (Eucalyptus globulus) coppice TreeNote No. 35 May 2002
By Robert Archibald, CALM Science Division, Department of Conservation and Land Management, Kensington; Keith Little, Scottsville, South Africa; and Richard Harper, CALM Science Division, Kensington
Many Eucalyptus species coppice readily and overseas, large areas of blue gum plantations are actually managed in short rotations as coppice. It is generally accepted that a tree grown from coppice will produce greater yields than a seedling of the same age as the stems grow from a large and well-established root system.
There are three post-harvest options for the management of these types of plantations:
- Revert to farmland;
- Replant; new genetic material or species could deliver yield benefits but these would have to outweigh the costs of re-establishment.
- Coppice; on good quality sites where there is sufficient stocking it may be more economic to coppice. The cost saving in coppicing over replanting may be some 20 to 30 per cent. This difference arises from not only the saved costs of site preparation, seedlings and planting but also herbicides and fertiliser.
Clearing Coppice to revert to farmland
There are a number of methods being trialled to remove coppice and stumps post harvesting to return the area to farmland. Stumps have been mulched, some burnt and pulled out, some coppice has been killed off with herbicide with the slash pushed up into winrows for burning and some has been left to grow. More details will be available after our field day in May 2017
Coppicing involves a shoot reduction operation and removal of trash from the stumps.
Disturbance to the structure and function of a tree during harvest will result in some deaths. If coppicing, harvest operations must maximise the survival of stools (living stumps) from which coppice grows. Harvest timing affects stool survival and cutting in autumn is ideal unless the area is prone to frosts, when felling should be delayed until late winter. Cutting in summer will delay sprouting and increase the chance of the stool drying out and may also lead to the separation of bark from the stool.
The ideal stool should be 10 to 20 cm high, with a smooth surface on a slight angle (to shed water) with good bark attachment. Trash can be used to protect the stools while harvesting of nearby trees takes place, but should be removed before the coppice shoots begin to appear. A low-cut stool will direct growth into more choice stems which are stronger and less prone to wind damage.
Spreading trash is preferred so it acts as a mulch. Although trash retention may cause access problems and a fire hazard, it is desirable as it retains nutrients, conserves soil moisture and minimises erosion. Access problems can be partly overcome by directing the bulk of the trash into alternate rows
By pruning unwanted stems, growth can be channelled into selected stems, giving them a greater chance of survival to harvest. The ultimate aim is to maximise the wood volume of the utilisable stems and it is recommended that one or two shoots per stool are retained, with the following considerations
- Single stem coppices are more likely to create new coppice shoots
- A single stem will result in handling fewer logs at harvest
- Two-stemmed trees supress further shoots
- two stems have the potential to hinder harvesting
- With a two-stemmed tree, wastage is also likely to be slightly higher.
Current knowledge suggests it is best to decide the number of shoots to be retained for each individual tree by considering in combination:
- the characteristics of the shoots on the stool
- the surrounding stocking of live stools
- the size of the stool
Two shoots should be retained if:
- the area is not fully stocked
- the stool is not below average diameter for that stand
- the shoots are co-dominant and showing good growth and form
- the shoots are on opposite sides of the stool.
Shoots should be removed when they are about 2 m in height (about 18 months of age after harvest in a typical area), when shears (rather than chainsaws) can still be used and the dominance of the selected stems limits new shoots.
Blue gum is capable of coppicing over many rotations. In the Nilgiri Hills in India it has been successfully grown for fuel wood in rotations of 10 years for the past century.
Extracts from Managing blue gum (Eucalyptus globulus) coppice TreeNote No. 35 May 2002
By Robert Archibald, CALM Science Division, Department of Conservation and Land Management, Kensington; Keith Little, Scottsville, South Africa; and Richard Harper, CALM Science Division, Kensington