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Glossary - S

Sapwood
Living wood making up the outer annual rings of tree trunk through which water from soil is conducted up the tree.
Sawlogs
Material of at least 14 cm top diameter that is destined to be sawn into planks or boards.
Scarification
The breaking-up of the ground surface by machine prior to planting. Used on well-drained ground.
Scrub
Area of poorly formed trees or bushes unsuitable for conversion to timber.
Seed
Small, usually rounded body, sometimes with a wing or wings to aid wind dispersal, that develops from the fertilisation of the ovule, and from which a new plant develops after germination.
Seed orchard
Orchard where trees are grown for seed production rather than timber.
Seed year
Year when a lot of seed is produced of a particular species or several species over wide area. Usually the year following a good summer. See also Mast year.
Seedling
Young tree grown from seed, either in the forest naturally or in a nursery, prior to being transplanted or planted out in the forest.
Selective thinning
Where trees are removed or retained on their individual merits systematic thin.
Semi-natural woodland
Woodland with natural characteristics (predominantly native species of trees, ground plants and animals) where wood production is not a primary objective, this term is used rather than natural because the woodland may have originally been planted or have been managed for wood production in the past.
Sessile
Describing fruits which are not borne on a stalk.
Shade bearer
A tree that will grow in the shade of others. See also Light demander.
Shelter belt
Trees and shrubs planted in a comparatively narrow strip to provide protection, usually of farmland.
Shrub layer
Shrubs and bushes, i.e. woody plants without a single main stem, occurring well below the forest canopy.
Silviculture
Cultivation of trees as crop with the primary objective of producing wood products.
Silviculture
The care and cultivation of forest trees.
Simple
Term describing a leaf that is not divided into leaflets, e.g. oak.
Skidder
Tractor used to pull pole length timber along the ground.
Skyline
A type of extraction by cable crane using a fixed overhead line wire.
Small diameter roundwood
See Pulpwood.
Snedding
Removal of branches from a felled tree.
Softwood
Term used to describe the wood of coniferous trees, or conifers themselves, although in fact the wood is not always softer than the 'hardwood' of broad-leaved trees.
Softwood
The wood of coniferous trees or conifers themselves.
Species
A group of plants or animals that inter-breed.
Spot weeding
Weeding of individual trees rather than a continuous band. Usually applies to chemical weeding when it is cheaper to spot weed (less chemical is used) and it is better for the environment (chemicals are only applied where they are absolutely needed.)
Spring wood
Thin-walled cells laid down in stems and branches in the early part of the growing season. It is of lighter colour than the summer wood in most species.
Stand
A fairly uniform collection of trees, composed of one or a few species, comprising one age class, from either artificial or natural regeneration.
Standard
A single tree grown as an individual amongst coppice. A large nursery grown tree produced for amenity planting.
Standing sales
Sales of timber quality trees whilst they are still standing based on the assessment of their volume. The buyer is responsible for getting the trees felled. Timber is also sold "at stump" or "at roadside" based on felled measure.
Standing volume
Measurement of quantity before trees are felled, usually expressed as cubic metres overbark standing.
Stocking
The density of trees in a plantation, measured in stems per hectare.
Stumpage
Income from selling timber less total expenditure for a particular project/compartment or a Forest District. Expressed as £/m³ standing.
Sub-soiling
Disturbing the soil below the ground surface. See Ripping.
Succession
Changes that occur in vegetation as bare ground is progressively colonised by different species, ending in climax vegetation.
Sucker
Shoot arising directly from a root or at base of a stem.
Summer wood
Thick-walled cells laid down in the middle of the growing season in stems and branches. Usually darker than the adjoining spring wood and thus showing up as a ring in cross-section.
Super-Sitka
An improved strain of Sitka spruce which has better shape and faster growth than normal.
Surplus
Income from selling timber less forest cost for a particular project/compartment/area/Forest District. Expressed as £/m3 standing or as a total sum.
Sustainable development
Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.
Sweep
The natural bend in a log or tree, generally applied to long gentle bends.
Swipe
A machine which cuts grass and other vegetation by means other than sharp blade, i.e. rapidly rotating chain or disc. Also used as a verb to describe the operation carried out with the machine, e.g. swiping a ride or fire-break.
Systematic thinning
Removal or thinning on a predetermined basis without regard to the quality of the individual trees, e.g. removal of whole lines of trees on a numbered sequence. Also called mechanical thinning.
Systems biology
The study of how function at all levels of biological hierarchy emerges from the interactions between the components of biological systems. Research typically involves quantitative experimentation plus mathematical analysis and reconstruction.