General information about coppicing

Species and growth

When the tree is cut down, new shoots arise from dormant buds on the side of the stump, or from adventitious shoots around the edge of the cut surface. Root buds which are close to the stump can also produce coppice shoots, especially in hazel and birch. The buds are stimulated into growth by changes in plant hormone levels produced when the previous top growth is removed.

Most native broadleaved species coppice, but some are stronger than others. The species which produce the strongest growth over the longest time are ash, hazel, oak, sweet chestnut, field maple and small-leaved lime. Birch and black poplar only produce regrowth if cut young when the stump is fairly small. The native wild cherry, aspen and elm, and the introduced white poplar and grey alder produce suckers from the roots, rather than growing from the stump. Conifers die if cut to the stump.

The number of shoots produced depends on the species, and the age and size of the stool. In the first season a large number of shoots, between 50 and 150, are produced, but self-thinning occurs and most die off. By the middle of the rotation, between 5 and 15 may be left. Artificial thinning is not often done, although this can be used to maximise growth per stem, where demand is for larger size poles.

Regrowth varies according to the site, the condition of the stools and the species. Where unchecked by browsing, regrowth may be as much as 3m (10’) in the first season for willows, 1.5-1.8m (5-6’) for ash, hazel, sycamore and sweet chestnut, 1m (3’) for aspen and field maple, and 600mm (2’) for hornbeam. There is an even greater increment in the second year, and then growth slows in following years. The canopy may close in the second or third year for the more vigorous species.

Short rotation coppice is grown for less than 10 years before being cut. Long rotation coppice is grown for more than 20 years.

The following table shows the main coppice species, together with their uses, rotation, spacing and number of stools per hectare (and acre). This information relates to good quality, single-species coppices which are regularly managed (‘in-cycle’). Neglected coppices, grown beyond their optimum rotation, are likely to have fewer stools per hectare, with gaps where stools have died, and fewer, larger poles from each stool. The main use will be for firewood. Depending on the mix of species, mixed species coppice should be grown on about a 15 year rotation at 1000 stools/hectare (400/acre), with main uses for fencing, furniture and firewood.

Table 9a: Short rotation coppice

Table 9b: Long rotation coppice

Yield

The yield will depend on the spacing of the coppice stools, the rotation and the quality of management. Site factors, such as soil fertility, moisture and shelter are also important. The following figures are for commercial coppices, where the aim is to maximise yield.

The mean annual increment over a coppice rotation (dry wood per hectare per year measured down to 5cm diameter) is about 2.5 tonnes for sycamore, birch, ash, lime, oak, alder and sweet chestnut. For poplar and willow it is about 6 tonnes/ha/yr. If twigs are included, sweet chestnut yields about 4 tonnes/ha/yr. Hazel, including all material down to 2cm diameter, yields about 2.5 tonnes/ha/yr (Evans, 1984). The total yield for example for hazel cut at year 10 of a rotation should be about 25 tonnes/ha.

Short rotation coppice willow grown on a three year rotation for energy production can produce very high yields, of 8-20 tonnes of dry wood/ha/yr. This includes all woody material, which is machine harvested and converted to woodchips before being burnt for heating or to generate electricity (Macpherson, George, 1995).

Sweet chestnut

A 15-year-old commercial sweet chestnut coppice should yield products as shown below.

Table 9c: Yield per hectare of commercial sweet chestnut coppice

Hazel

A hectare of eight- or nine-year-old, well-stocked hazel coppice will produce 25,000 to 30,000 rods 3-4.5m in length. These could be converted into 740 hurdles or about 185,000 thatching spars. (Equivalent of 10,000 to 12,000 rods per acre, 10-15’ in length, which could produce 300 of 6’ x 6’ hurdles or 75,000 thatching spars). In addition pea and bean sticks could be produced.

Coppice craftspeople require an average of 1.62 hectares (4 acres) a year to make a living, meaning that each person requires at least 12.96 hectares (32 acres) over an 8 year rotation.

The 70 craftspeople in Hampshire (1995) required 907 hectares (2,240 acres). Grants provided by Hampshire County Council funded 50% of the cost of restoring over 506 hectares (1,250 acres) of derelict hazel coppice between 1982-95, but the area of good quality in-cycle hazel coppice in the county was still not enough to meet the demand from coppice workers. In 1995 there was a requirement of 1,250 hectares (3,087 acres) of in-cycle coppice from the existing workforce, but only 750 hectares (1,852 acres) of in-cycle coppice were available, which included the areas which had been restored. (Hampshire County Council, 1995).

Coppice becomes a viable proposition for a landowner when the coppice is in good condition, properly in-cycle, with good access. Prices per hectare/acre, as paid by the coppice worker, should compare favourably with most broadleaved crops. There is the additional income from occasional felling of standards, and the value for wildlife, shooting, amenity and other uses.

Coupe size

The coupe, cant or panel is the block of coppice which is cut at any one season. A coppice woodland should be divided up into several coupes, which are cut in rotation over a period of years. The size of each coupe will depend on the labour available to cut it, the market for the products and other factors. As far as possible one should try to keep to the planned cycle, although this may be difficult with changing markets or other factors.

The size of coupe may be anything from a minimum of 0.1 hectare (0.25 acre), 0.5 hectare (1.2 acres) in larger woods, to a maximum of 1.2 hectares (3 acres). Small plots are more vulnerable to damage by deer, and to shading by surrounding trees. Coupes should not be larger than 25% of the total area of the wood, in order to maintain continuity of the coppice habitat.

Coupes should be square or rectangular in shape, to maximise the sunshine reaching the plot, and to minimise fencing costs. Avoid long narrow shapes and convoluted edges which will be more expensive to fence, and which will produce less vigorous growth. All coupes should have at least one edge which abuts a ride, so that the cut wood can be removed from the coupe without dragging it through another coupe. If necessary create more rides, as these are essential for efficient management of the wood, as well as themselves being valuable wildlife habitats. Take account of the need for deer management when planning the coupes and rides, with high seats sited for safe effective culling as necessary.

Plan the coupes so that cutting progresses sequentially around the wood, if possible with adjacent coupes cut in sequential order. To benefit wildlife, especially relatively static invertebrates, it’s important that species can easily move from one coupe to another as conditions change through the coppice cycle. Some examples of coupe layout and cutting sequence are given below.

At the end of each coppicing season, mark carefully on a map the areas which have been cut and date them, for future reference. Other details such as the volume of produce, man/days and so on can also usefully be recorded.

Coppice with standards

This traditional system combined the production of timber from standard trees grown on a long rotation, with coppice species beneath grown on a short rotation. For hazel, the general guide is that there should be one-third canopy closure by the standards at the start of the coppice cycle, increasing to two-thirds canopy closure at the end of the coppice cycle. The number of standards will vary according to their age and spread, from about 30 large mature standards per hectare, up to 150 young standards per hectare. To ensure continuity of canopy, a mix of ages is needed. The following gives an ideal age range at which to aim for standard oak or ash with hazel coppice.

Table 9d: Standard oak or ash with hazel coppice - 50 standards per hectare total, comprising:

From Hazel Coppice (Hampshire County Council, 1995).

New trees can be recruited from protecting natural regeneration, or from ‘singling’ coppice stools of suitable species, to leave one stem to grow up to form a standard. As well as oak and ash, other species can be grown as standards where they form a natural component of the wood, with the exception of beech and hornbeam, which cast too dense a shade. Small-leaved lime, hornbeam, wild-service, crab-apple or wild cherry may be suitable where they occur naturally. Sycamore and birch should be avoided as standards, as they spread too quickly by seed. Avoid bringing new species and new genotypes into the wood, but use natural regeneration wherever possible.