A way to measure the spread of plants from a focus

Abstract

The relative frequency of occurrence of plants (or plant parts) is determined at increasing distances from a focus, where the relative frequency is unity. The area under the resulting frequency/distance curve is determined, as a measure of spread. Effect of treatments on spread can be compared by comparing these areas. A rate‐of‐spread index can be calculated from areas determined at successive times.

A model is proposed which enables the area under the curve to be estimated from only three (or even two) frequency determinations. The amount of field work is thereby much reduced.

Use of the model is illustrated by comparing the spread of Pennisetum clandestinum (kikuyu) and several Cynodon cullivars in a nursery.

UITTREKSEL

Die relatiewe frekwensie van voorkoms van plante (of gedeeltes van plante) word bepaal by toe‐nemende afstande vanaf ‘n middelpunt waar die relatiewe frekwensie een is. Die oppervlakte onder die frekwensie/afstand kromme word bepaal om te dien as ‘n maatstaf van uitbreiding. Die uitwerking van behandelings op uitbreiding kan vergelyk word d.m.v. vergelyking van hierdie oppervlaktes. Tempo van verspreiding kan afgelei word van oppervlaktes wat op agtereenyolgende tye bepaal is.

‘n Model waardeur die oppervlakte onder die kurwe met drie (of slegs twee) frekwensie bepalings geskat kan word, word voorgestel. Die hoeveelheid veldwerk word hierdeur heelwat verminder.

Gebruik van die metode word geillustreer deur die uitbreiding van Pennisetum clandestinum (kikoejoe) en verskeie Cynodon cultivars in ‘n kwekery te vergelyk.