Glossary
| Alluvium: | sediment deposited by rivers and streams. It ranges from clays, through silts and sands, to gravels. |
| Argillite: | a sedimentary rock composed of clay particles which have been hardened and cemented. |
| Bank collapse: | mass movement of streambanks, once under-cut by scouring action of floodwater. |
| Biomass (vegetation): | the amount of plant matter growing on a given area of land; usually expressed in kilograms per hectare. |
| Blanking: | replacement of any seedling trees that have died and left blanks in a regular planting pattern. |
| Braided channel: | a river channel that has numerous branches, separated by exposed alluvial bars. |
| Carbon ignition: | conversion of soil organic matter to CO, gas by high-temperature reaction, when overlying vegetation is burned. |
| Check dam: | steel and concrete structure in mountain torrent, designed to trap sediment and prevent scour by debris flows. |
| Close planting: | plantation of trees sufficiently dense to form a continuous or close canopy. Seedling trees planted at densities of 1000 stems a hectare or more form a close canopy within 5 to 10 years, depending on species. Mature trees maintain a close canopy even if thinned to 200-400 stems a hectare. |
| Collapse hole: | circular hole in topsoil, caused by its collapse into a tunnel (under-runner) in the subsoil. |
| Condition: | a formal restriction on the way land is used, attached to a resource consent issued by a district or regional council, or written as a rule in a district or regional plan. |
| Debris dam: | timber and netting structure in hillside gully, designed to trap sediment and prevent scour by runoff. |
| Density (vegetation): | the thickness of plant cover growing on a given area of land; usually expressed as a percent of cover for grass, or as stems per hectare for trees. |
| Downs: | undulating, low hills, usually with slopes gentle enough to be cultivated. |
| Environmental effect: | any impact which a land use has on soil, water, air, plants or animals. |
| Enrichment: | planting timber trees (either exotic or indigenous) in regenerating scrub. |
| Ephemeral (stream): | watercourse which flows after heavy rain, and dries up during fine weather. |
| Erosion | the stripping of soil and weathered rock from landforms; creating sediment for transportation by water, wind or ice, and enabling formation of new sedimentary deposits. |
| Farm conservation plan: | map with attached schedule of erosion control measures, prepared by one of the former catchment boards (now taken over by regional councils). |
| Farm improvements: | buildings, yards, fences, tracks, drains, ponds, water reticulation. |
| Floodplain: | low-lying alluvium immediately adjacent to a river or stream, inundated as soon as it overflows its banks. |
| Gabion: | wire basket filled with rocks, used to stabilise riverbank or foot of unstable slope. |
| Greywacke: | a sedimentary rock composed of silt or sand particles which have been hardened and cemented. |
| Groundwater: | water which flows through pores and fissures in soil or rock beneath the water table. |
| Gullying: | erosion of soil or rock by ephemeral streams downcutting through hillslopes, after heavy rain. |
| Heavy soil: | soil with a high ratio of clay to sand or silt, sticky when wet, hard when dry, and difficult to cultivate. |
| Hill country: | steep land with slopes greater than 20 degrees, but low relief; typically 100 to 300 metres’ difference in elevation. Valley bottoms are usually narrow. |
| High country: | mountainous land with steep slopes and high relief; typically more than 300 metres’ difference in elevation. Slopes are usually separated by broad, flat valley bottoms infilled by alluvium. |
| Light soil: | soil with a high ratio of sand or silt to clay; aggregated when wet, but powdery and difficult to cultivate when dry. |
| Loess: | silt deposited by winds blowing across sparsely vegetated ground during the last Ice Age; mantles many plains, terraces and downs in the eastern South Island and southern North Island. |
| Loam: | soil with substantial proportions of clay, silt and sand, with an aggregated structure enabling easy cultivation whether wet or dry. |
| Mass movement: | erosion of soil or rock by gravity-induced collapse. Usually triggered by groundwater pressure after heavy rain, but can also have other causes, notably streams undercutting the base of a slope, or earthquakes. Movement can either be rapid and near-instantaneous (landslides, avalanches, debris flows) or slow and intermittent (earthflows, slumps). |
| Mudstone: | a sedimentary rock composed of silt and clay particles, compacted and weakly cemented together by a small quantity of lime. |
| Nitrogen volatilisation: | conversion of soil nitrogenous matter to NO and NO2 gas, by high-temperature reaction when overlying vegetation is burned. |
| Organic load: | the quantity of organic matter passing a stream reach in the course of a year. Usually expressed in terms of biological oxygen demand, i.e., the amount of oxygen consumed by micro-organisms as they break it down. |
| Outwash: | alluvial sand and gravel deposited by rivers draining glaciers during the last Ice Age; widespread on terraces and floodplains in the South Island. |
| Pair planting: | plantation of trees in pairs on either side of a hillslope watercourse, to prevent gully incision. |
| Regolith: | the basal layer of soil, composed of material that is still recognisable as weathered rock or other geological deposits (such as alluvium); grades upwards into overlying subsoil. |
| Resource consent: | permit issued by a district or regional council, allowing a change in the use of land (or other resources). Consents are only required if a district or regional plan identifies the proposed use as capable of causing adverse environmental effects. |
| Reversion: | spread of indigenous scrub across land that is lightly grazed or retired from grazing. |
| Retirement: | fencing of land to exclude grazing by stock. It may entail rank grass and weed, or reversion to indigenous scrub, or plantation of timber trees on the land that is no longer grazed. |
| Rilling: | erosion of surface soil particles by rainwater running off across the ground as district rills after heavy rain. |
| Riparian: | pertaining to riverbanks. |
| Rule: | a clause in a district or regional plan, either requiring an application for a resource consent if a particular change in land use is proposed, or allowing the change as of right, but subject to conditions designed to avoid adverse environmental effects. |
| Runoff: | water flowing across or through soil after rain. The term is sometimes also applied to water flowing in ephemeral channels. |
| Sandstone: | a sedimentary rock composed of sand grains, compacted and weakly cemented by a small quantity of lime. |
| Saturation: | penetration of all the pores and fissures in soil by water, so that air is excluded. |
| Scour: | erosion of channel beds and banks by streamflow. |
| Sediment load: | the quantity of sediment passing a stream reach in the course of a year. |
| Sheetwash: | erosion of surface soil particles by rainwater running across the ground as thin sheets after heavy rain. |
| Silviculture: | management of timber trees to improve quality and yield, principally by pruning and thinning; can also entail seedling selection, fertilising, spraying for disease and weed control. |
| Soil conservation: | measures which protect soil from excessive erosion, structural breakdown, nutrient loss or pollution; thereby minimising decline in its capacity to support plant and animal life. |
| Soil nutrients: | minerals in the soil that are beneficial for plant growth, principally the elements N, P, S, Ca, Mg, K and their derived compounds. |
| Soil structure: | the arrangement of soil particles and inter-particle spaces (pores and fissures). Good soil structure is beneficial for aeration, percolation of water, penetration by plant roots, resistance to stock treading, and load-bering capacity when cultivated. |
| Solute load: | the quantity of dissolved chemicals passing a stream reach in the course of a year. |
| Spaced planting: | plantation of trees sufficiently far apart that a close canopy cannot form. Depending on species, mature trees at a density of SO to 100 stems a hectare are widely enough spaced for pasture or other vegetation to grow inbetween. |
| Subsoil: | the mineral-rich layer of the soil, lying underneath topsoil and above regolith from which it is derived; weathered to a stage where the parent material (rock or sediment) or no longer recognisable. |
| Streamflow: | water flowing through permanent channels. |
| Tephra: | loose material, e.g., ash and pumice, deposited by volcanic eruptions; mantles extensive areas of the central North Island. Terrace: flat to gently sloping alluvial surface, elevated above floodplain level. |
| Till: | chaotic mix of clay and boulders deposited by glaciers during the last Ice Age. |
| Topsoil: | the uppermost layer of soil, rich in organic matter incorporated from the decay of plants and the activities of micro-organisms, intermixed with mineral matter derived from the underlying subsoil. |
| Torrent: | a steep, permanently flowing channel incised on a mountain slope; prone to flash flood and passage of debris flows after heavy rain. |
| Tunnel (under-runner): | a natural sub-surface cavity, formed by runoff flowing downslope through subsoil after heavy rain. |
| Weathering: | breakdown of rock or other geological materials (e.g., alluvium) into soil. by physical disintegration and chemical reaction. |
| Windblow: | erosion of surface soil particles by strong wind blowing across sparsely vegetated or bare ground. |
Contact for Enquiries
MAF Information Services
Pastoral House
25 The Terrace
PO Box 2526
Wellington, NEW ZEALAND
Fax: +64 4 894 0721
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