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Guide to design principles

Woodland Design In The Landscape - A Simple System for All Situations

Different species and difficult sites will not always respond in the same way to similar treatment. However, we think that our readers may find it useful if this year we explain what we call the WOODLAND IMPROVEMENT SYSTEM. It is a system for new planting in lowland Britain which combines simplicity and fits in with the often complicated grant constraints.

In general, planting should conform to the general pattern of the landscape, whether natural landforms or field patterns, and follow the same rounded or irregular shapes. Geometric patterns or regular shapes should be avoided. Introduce scallops of open space to avoid straight line appearances. Use your woodland edges to create species diversity.
There are 2 simple rules to follow.

Plant main trees in single species drifts--Don't use line mixtures

Create irregular shaped single species groups -- called 'drifts'-- of 9 to 40 trees of a species. Limit yourself to 3 to 4 main species with valuable timber crop production as a main objective for this area of the woodland. Emphasise irregularity by following land form and contour. Keep each group asymmetrical in both size and shape. Avoid squares, rectangles or diamonds. Use small groups of conifer nurses between the drifts or in the edges to build up microclimate and game roosting cover. Do not plant conifers within the drifts themselves.

Plant 3-4 rows only of woodland edge in species groups of three

Woodland edges require a minimum of 3 rows or 5 metres deep to create the optimal conditions for microclimate, amenity and for conservation, both ecological and biodiversity. 90% of all wildlife habitats has been shown by research studies to be found in the edges and woodland margins. The amount of woodland edge and its design depends on the site, its exposure and the weight of feeling towards wildlife, landscape definition, shooting and bird holding requirement. Orientation of rides is also important. Too much woodland edge may become uneconomic. A closer spacing layout is required than for the main drifts -- follow strictly the layout below.

The siting and the amount of woodland edge will create 'your woodland's' special character, reinforce wildfire corridors and enhance the growth of the main drifts to an important degree.

Row 1: Shrubs/hedging. 100 per 100m stretch. (e.g. Hawthorn, Blackthorn, Buckthorn, Guelder Rose)
Row 2: Minor Broadleaves. 67 per 100m stretch. (e.g. Crab Apple, Hazel, Birch, Rowan, Holly, Willow)
Row 3: Minor Broadleaves/Conifers. 50 per 100m stretch. (e.g. Larch, Norway Spruce, Alder, Cherry, Holm Oak)
Row 4: Major Broadleaves. 48 per 100m stretch. (e.g. Aspen, Sycamore)

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Climate Control - Wind & The Environment - "Come on" said the wind, "let's race again!"

The Basic Principle

The wind has a far greater effect on the environment than most people understand. Wind reduces both the air temperature and its ambient humidity. Increased wind speed means greater wind chill in most circumstances. The higher the humidity and temperature, the more the opportunity for photosynthesis. This has a direct effect on the amount of plant growth that can take place each and every day.

Shelter from plantations and shelterbelts has a dramatic effect on the wind speed at ground level and reduces the wind chili factor there, it will thus alter the whole microclimate on the adjacent land. Shelter protects crops, livestock, buildings and gardens from the ravages of strong prevailing winds. It greatly enhances the growth of crops, plants and trees within the sheltered area.

The aim of a shelterbelt is to divert the wind currents moving across the ground upwards without causing turbulence. It must act as a filter, allowing layers of slow moving warmer air to act as a transition zone to keep the main colder airstream from returning to ground level until it is a considerable distance downwind.

It should not produce a solid barrier which then produces high velocity eddies at ground or tree surfaces and so actually makes the situation worse.

Landscape Design

There is a close connection between the height of the trees in the shelterbelt and the distance downwind where protection is provided. Useful shelter is usually provided downwind up to about 20 times the height of the tallest row of trees. Therefore a shelterbelt 100 metres long and 15 metres high should protect up to 3 hectares (7.11 acres) downwind and will even give some small benefit upwind.

Height and uniform permeability of about 45% are the key elements of design. Too dense a shelterbelt causes major eddies and turbulence. The wind rising over a well designed woodland edge creates its own roof and forms a natural greenhouse, albeit without solar radiation gain, over a long distance downwind. Stock use less energy in keeping warm and crops and trees flourish better in the little understood but crucial interaction between plant physiology and microclimate. This interaction is best known and demonstrated in the tropical rainforest.

Well managed shelter is the characteristic and ancient feature of our farming landscape and combines with it all the benefits arising from diversity of habitats, wildlife and game cover. By designing within the rules below, the landowner creates a better environment for his own benefit and pleasure as well as for the future. The climatic improvement begins on a small scale immediately after the trees have been planted, growing each year with the trees.


The Eight Rules

1. WIDTH
Plant 4 rows of closely spaced trees and shrubs which will grow at different rates to different heights. An optimal planting pattern between the trees and between the rows is shown in the diagram on page 51; this is not a rigid pattern and both site problems and the landowner's preference must be considered.

2. LENGTH
Aim for an optimum length of 25 times the eventual height of the tallest trees. Otherwise the wind will reduce the sheltered area to a triangle and will go around the edges.

3. ENDS
Round the corners and preferably try to accomodate a small leg at each end to increase protection effect.

4. PERMEABILITY
The optimum permeability is 45%, Rows of old trees and spendthrift shelter generally make matters worse by increasing the wind speed through the lower areas. Some thinning will be required over time but no pruning.

5. GAPS
Avoid gaps, openings and re-entrants. If unavoidable, viz gateways, design oblique re-entrants to the prevailing wind.

6. REGENERATION
Regenerate old and ineffective shelterbelts by planting three new rows of shrubs and the smaller trees on the windward edge. Then thin and underplant the old belt, planting a shade bearing conifer nurse within.

7. FENCING
Keep the stock out with a new stock proof fence at least 3m from the first row.

8. WEEDING AND MAINTENANCE
Weed the trees twice for the first 3 years with an approved herbicide 0.5m radius around each tree. Don't brash or thin these 4 rows for 10 years.
If you can establish the shelter ahead of the main crop trees so much the better, but you do need 15m minimum width for the initial planting to qualify for WGS grant.

Grants are also available under FCGS. This will then become a potential 'timberbelt'.

Woodland Design, Planting, Grants and Management

Our sister company, Woodland Improvement Ltd offers a comprehensive forestry service to those who wish to create new plantations or manage existing woodlands. They offer professional advice on all aspects from woodland planning and establishment through to the felling and marketing of timber.

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