Polygonal plot method for estimating the canopy‐spread cover of shrubs

Abstract

An optical method for measuring canopy-spread cover of shrubs is described by means of an illustrated example. Boundaries of plots are hypothetical lines joining the centres of wholly visible shrubs or groups of shrubs surrounding the observation point. Plots are subdivided into triangular subplots to allow calculation of plot size as well as the percentage canopy-spread cover inside plots. A listing of a FORTRAN programme for the calculations can be supplied. UITTREKSEL'n Optiese opnamemetode vir die raming van kroonregimebedekking is bespreek met behulp van 'n ge'illustreerde voorbeeld. Perseelgrense is die denkbeeldige verbindingslyne tussen die midddpunte van volledig sigbaie struike of groepe struike rondom die waarnemingspunt. Vir die berekening van perseelgroottes asook persentasie ki'oonregimebedekking binne persele, is persele in di'ichoekige subpersele opgedeel. 'n FORT RAN -program vir berekenings kan voorsien word. INTRODUCTIONDifficulties often arise in studying the vegetative cover of shrubveld, particularly in the work of pasture scientists. Their interest is in those parts of the plant which are within easy reach of browsers. Changes in the availability of browse are important, because shrubs often provide the greatest part of the animal diet.Survey techniques for measuring canopy cover, such as the variable plot method of Cooper (1957), arc not primarily designed for measurements at a fixed height. The modified wheelpoint technique of Von Broembsen (1965) is not practicable if the shrubs are impenetrable; besides, it measures only basal cover. The descending-point method of Roux (1963) is suited only to shrubs of 0,7 m or less in height. For these reasons an attempt was made to develop an optical technique more adaptable to the needs of pasture workers.The aim was a method which could easily be applied. Measurements were to be limited to angular and distance readings. The topographic-tacheometric telemeter "Telelop", manufactured by Zeiss Jena, was found suitable for this purpose.

Comparison of crown cover estimates for woody vegetation in arid rangelands

“…1960;Fisser 1961;Coetsee & le Roux 1971;Hanley 1978;Holm et al 1984). Most of them are either too time-consuming or too imprecise to be of use in monitoring sites over extensive areas of arid rangelands, where the aim is to detect change with time.…”