Glossary

Biomass - This is the total weight of living individuals of one species, or a number of different species combined, in a specifically defined area. It is one way of measuring and comparing the abundance of living things in different places or circumstances. For example, one might measure the biomass of aphids on a selected plant, or make an estimate of total plant biomass in a particular habitat.

Bryophytes - are members of the plant division Bryophyta. Members of this division are characterised by being small, rootless, thalloid or leafy, non-vascular plants. It includes liverworts, hornworts and mosses.

Impervious - is a term used to describe materials which resist the passage of water. - i.e. water will not dissolve in them, nor pass through them in any way.

Invertebrates - This is a collective term for all those animals which do not belong to the phylum Chordata (i.e. those without a backbone, or vertebral column). This is a general term and is not a scientific classification.

Microhabitats - Organisms occupying the same general habitat may actually be living under very different conditions. A small habitat with significantly different environmental conditions, within a larger one, is termed a microhabitat (e.g. a community of animals living in mosses which are growing on tree trunks are occupying a moss microhabitat within the larger woodland habitat). Microhabitat is a relative term and does not imply a definite size of habitat, it merely denotes a smaller habitat within a larger one.

Pioneer - The first stage in a succession. A pioneer species is one which establishes early on in the colonisation of a new area.

Red Data Book - These are lists of species whose continued existence is threatened. Red Data Book species are classified into different categories of perceived risk. Each Red Data Book usually deals with a specific group of animals or plants (e. reptiles, insects, mosses). They are now being published in many different countries.

Stocking Rates - This is the number of animals put out to graze on a particular pasture. If the number of animals (stocking rate) is too high, then overgrazing will occur, with detrimental effects on the pasture. Too few animals may result in under-grazing, also often with attendant detrimental effects. The optimum stocking rate will vary with the type and size of pasture, and also with the type of animals being put out to graze. This is because different animals graze with different intensities and strategies. The stocking rate may also vary depending on the purpose of the grazing. If grazing is being used as a land management tool, then objectives over and above feeding stock and preserving pastures in good condition, may require differing stocking rates.

Succession - This is the process by which one community of plants and animals is gradually replaced by another. It is reasonably directional and hence to a certain extent, predictable (e.g. bare ground > pioneer weed species > grassland >scrub > woodland). Succession occurs because the original community modifies the physical environment in some way, making it more favourable for a different set of species. The first stage in a succession is termed the pioneer stage. Succession will then proceed through various other stages (seres), until a climax (or final) stage) is reached. The climax community is in equilibrium with the physical environment and succession proceeds no further. The length of each stage in a succession and its direction (i.e. the final climax community), will depend on local environmental conditions.

Thalloid - Description of a plant body composed of a thallus. A thallus is not differentiated into leaves, stems and roots but consists of a single cell, a colony, a filament of cells, or a large branching multicellular structure.

Turbury - Is the practice of turf or peat cutting. Turbury rights are the legal rights to cut turf and peat on common land, for use as domestic fuel. The distinction between turf and peat is somewhat blurred. Peat undoubtedly refers to the deposits of sphagnum moss on wet heaths. The interpretation of turf is less clear. It may just refer to the removal of the upper layers of soil together with their plant cover.