Glossary for agroforestry

Compiled and edited by Peter Huxley and Helen van Houten, International Centre for Research in Agroforestry - 1997

land capability

The suitability of land for use without damage. Land capability (as ordinarily used in the United States) is an expression of the effect of physical land conditions, including climate, on total suitability for use without damage, for crops that require regular tillage, for grazing, for woodland and for wildlife. Land capability involves consideration of the risk of land damage from erosion and from other causes and also difficulties in land use owing to physical land characteristics, including climate.

land-capability classification

1. A grouping of soil survey mapping units into land-capability units, subclasses and general divisions.

2. A system for classifying land that is based on its capacity to support agriculture, grazing, forestry or its usefulness for recreation and conservation. The system is concerned with the fitness of land to support land use, rather than productivity, emphasizing soil erosion. See also land evaluation

land characteristic

An attribute of land that can be measured or estimated and that can be employed as a means of describing land qualities or distinguishing between land units of differing suitabilities for use.

land classification

A means of referring to systems of grouping land on the basis of its physical characteristics (including vegetation) without explicit assessment of suitability for kinds of land use.

land-equivalent ratio

The total area of sole crops required to produce the same yields as would be obtained when they are intercropped. The total land-equivalent ratio is the sum of the partial land-equivalent ratios of each component. Consideration has to be given to the planting density of the sole crops and the intercrop and to the management levels if sound comparisons are to be made. See also income-equivalent ratio

land evaluation

The process of assessment of land performance when used for specified purposes.

land facet

An area within which, for most practical purposes, biophysical conditions are uniform. All land within a land facet can be expected to respond similarly to management. Land facets often occur in regular sequences, within a land system (for example, hillcrest to valley floor). See also land unit

land occupancy

See crop succession

land race

Genetically variant population originating through selection and propagation by individual farmers, or in small areas of geographic isolation. See also provenance

land-suitability rating

The partial suitability of a land unit for a land-utilization type, based on one land quality, or a partial set of land qualities. Land-suitability ratings are combined to give a land-suitability class.

land system

An area with a recurring pattern of land facets. Initially identified and defined in terms of their land forms, then in terms of the full range of environmental factors involved (for example, 'undulating hills', 'coastal plain').

land unit

An area or type of land that posseses relatively homogeneous biophysical characteristics. All land within a land unit has similar resource potential and hazards; it is the basic unit for diagnosis of biophysical resource constraints and potentials. See also land facet

lapse rate

A measure of the decrease in temperature per unit increase in vertical height in the atmosphere (approximately 0.6oC per 100 m).

laterite

An iron-rich subsoil layer found in some highly weathered humid tropical soils that, when exposed and allowed to dry, becomes very hard and will not soften when rewetted. When erosion removes the overlying layers, the laterite is exposed and a virtual pavement results.

laterite soils

Soil groups found under tropical forest in humid conditions, characterized by a low silica sesquioxide ratio of the clay fraction, low base-exchange capacity, low clay activity, low content of most minerals and high stablity; often red.

latex

1. A thick white or whitish liquid produced by certain plants. For example, Antiaris toxicaria and Bridelia micrantha both have a latex sap. A more popular example is the rubber tree (Hevea braziliensis). Some types of latex can be harmful, especially if the latex gets into the eyes.

2. Milky juice, varying in thickness and colour,which flows from the tissue of some plants when they are cut.

Latin square

Experimental design that attempts to remove two sources of heterogeneity (row and column effects) from residual variation. A 5 x 5 square consists of 25 plots in 5 rows with 5 plots per row, and each treatment occurs once in each row and column.

lattice design

Incomplete block design (often used for variety or provenance trials) in which the number of treatments must be an exact square. See also alpha design

layer

1. A definable horizontal part of a plant canopy. See also stratified

2. In plant propagation, a shoot that puts out roots at the nodes when it comes into contact with the soil, naturally or artificially.

layering

1. The production of adventitious roots from a prostrate main stem or a branch in contact with the ground, enabling a potentially separate plant to be formed.

2. The rooting of an undetached branch or stem lying on or partially buried in the soil, or enclosed in other media, which is capable of independent growth after separation from the mother plant. See also air layering

leached soil

A soil where most soluble materials have been removed from the entire profile or removed from the layer and accumulated in a lower layer. See also leaching

leaching

The washing out of material from the soil, both in solution and in suspension. See also leached soil

leading edge rate

See rainfall intensity

leaf area duration

Leaf area index integrated over time.

leaf area index

The area of crop leaf per unit area of ground covered by the crop. Can also be estimated for single plants or hedgerows.

leaf area ratio

The ratio of the area of the assimilatory material of a plant to the total weight of the plant. Usually estimated as a mean leaf area ratio over the same period of time being used to examine net assimilation rate. Leaf area ratio = specific leaf area x leaf weight ratio.

leaf retaining

Applied to a plant whose leaves remain for more than one season. See also evergreen

leaf water potential

The total potential for water in a leaf, consisting of the balance between osmotic potential (arising from the presence of solutes), turgor pressure (the hydrostatic pressure developed in the cell in response to the osmotic potential and the tensile strength of the cell wall) and the matric potential (arising from the imbibitional forces of colloids and of capillaries in the cell wall). This determination of water deficit in leaves can be measured with a 'pressure bomb' or by psychrometric methods.

leaf weight ratio

Of a plant the weight of leaves compared with the total plant weight; usually averaged over a period.

leaf to total growth ratio

The change in leaf area in terms of change in total plant (dry) weight per unit of time. It indicates to what extent a plant is investing its dry matter production in leaf as distinct from non-assimilatory parts.

lee side

The downwind, sheltered side. See also windward side

legume

A pod-bearing member of the Leguminosae family, one of the most important and widely distributed plant families (now split into Papilionaceae, Mimosaceae and Caesalpiniaceae). Included are many valuable food and forage species, such as peas, beans, peanuts, clovers, alfalfas, sweet clovers, lespedezas, vetches and kudzu. Not all legumes are nitrogen-fixing plants, for example, many of the Caesalpiniaceae do not form nodules.

lenticel

Organ that replaces stomata in the structure of the stem. It is often clearly visible, looking like a little nodule.

level

A particular amount or category of a factor, for example, in a fertilizer rate trial the levels of the factor nitrogen may be nil, 50, 100 and 200 kg of N per hectare. In a pruning and thinning trial the factor levels will be intensities and times of pruning and thinning. Different methods of cultivation, types of plant container, brands of herbicide and times of spraying are other examples of  'levels'. See also factor

level terrace

A terrace that follows the absolute contour, as contrasted with a graded terrace. Used only on permeable soils where conservation of moisture for crop use is particularly important or where outlet channels are impractical.

ley farming

Rotation of arable crops with two or more years of sown pasture.

ley pasture

A temporary pasture grown as a specific phase in a defined crop rotation sequence.

liana

Vinelike climbing plant that grows by supporting itself on others and that roots in the ground, germinating there and maintaining its contact with the soil (also spelled 'liane').

lift pruning

Removing the lower branches of trees being grown for timber, to elevate the crown and to obtain a better quality, knot-free log. For example, as with Pinus radiata grown in pasture in New Zealand and Australia. See also pruning

light-use efficiency

The rate at which a stand (that is, a unit area of vegetation) produces dry matter (or a harvested part) as a function of solar radiation received. Better expressed as a function of radiation actually intercepted. It is also termed dry matter to solar radiation ratio.

lignin

A 3-dimensional polymer (based on hydroxylated cinnamyl alcohols, for example) that is interspersed in networks of two-dimensional cellulose molecules forming micelles (small aggregations) in plant cell walls, which are thereby greatly strengthened. Lignified tissues decompose relatively slowly and give rise to humus.

lignotuber

1. A woody organ arising from an accessory meristem in the axils of cotyledons or leaves near the base of a stem and having a proliferation of dormant buds.

2. A swollen, woody structure at the base of many eucalypts (particularly 'mallees') containing dormant buds.

lime

In strict chemical terms, calcium oxide. In practical terms, a material containing carbonates, oxides or hydroxides or both. Used to neutralize soil acidity.

line

A population consisting of one (self line), a few (inbred line), or many (bulked line) parents and their offspring through several generations.

linear data

A data swarm whose projection onto any two-dimensional space, however oriented, gives a two-dimensional swarm with a long axis that is (approximately) a straight line. If any projection yields a (projected) swarm with a curved axis, then the data are nonlinear.

linear transformation

Changing the basis of the values of a data set describing the association of two variables so that when plotted they form a straight line.

line breeding

1. A system of breeding in which a number of genotypes that have been progeny tested in respect to some character or group of characters are combined to form a variety.

2. A system of mating in which closely related individuals are crossed with each other.

line thinning

Removing specified rows of trees in a plantation, such as every fourth row. See also mechanical thinning

litter

Uppermost layer, on the soil surface, of loose organic debris (for example, as in forests), consisting of freshly fallen or slightly decomposed organic materials. See also O horizon, soil horizon

live fence

A way of establishing a boundary by planting a line of trees and/or shrubs (the latter usually from large stem cuttings or stumps), at relatively close spacing and by fixing wires to them. If animals are to be kept in or out, more uprights (dead sticks) can be tied to the wires. Also called a 'living fence'. See also hedge, hedgerow

livestock system

A land unit comprising pastures, herds and auxiliary feed sources, transforming plant biomass into animal products.

livestock unit

A unit used in animal husbandry based on the amount of intake required for a mature Friesian cow (taken to be an average of 550 kg liveweight) and based, experimentally, on Y = 0.0234x x 1032 (where Y = the dry matter intake in kg day–1 and x = the liveweight of the animal in kilograms). Smaller animals (for example, sheep and goats) are assessed as appropriate fractions of a livestock unit. Sometimes called a 'cow equivalent'. See also stocking rate

loam

Soil containing a relatively equal mixture of sand and silt and a somewhat smaller proportion of clay; generally a desirable quality. May be subdivided into texture classes like 'sandy loam', 'silt loam' and 'clay loam'. Specifically, soil material containing 7 to 27% clay, 28 to 50% silt, and less than 52% sand. See also soil texture

lodging

The collapse of top-heavy plants, particularly grain crops, because of excessive growth or beating by rain.

loess

Mainly silt, transported and deposited by wind.

log

The part of the trunk that is suitable for use as timber.

long-day plant

Plants whose development is affected by photoperiodism, in particular where a process (for example, flowering) is promoted if the plant is subjected to day lengths above a critical length and so night lengths below it.

longevity

Long life, long duration of existence.

long shoot

Where there is shoot dimorphism, an extended shoot contributing to the architecture of a tree.

lopping

1. Cutting one or more branches of a standing tree, for example, for fuel or fodder. See also pruning

2. A technique used to collect fodder for animals by cutting side branches, not the main stem. Animals can be allowed to eat the lopped branches of the tree, or they can be carried to the animals as in a zero-grazing system.

lot

A plot of land.

lumber

Sawn timber. A unit of measure is the 'board foot', that is, a board 12 inches long by 12 inches wide by 1 inch thick. See also timber

lysimeter

A vessel or container placed below the ground surface to intercept and collect water moving downward through the soil in which vegetation can be planted, and which is isolated hydrologically from the soil around it. Lysimeters are used to study various aspects of the hydrological cycle. See also evapotranspirometer