The precision of assessing components of the condition of moist tall grassveld

Abstract

The precision of a rapid technique previously developed to assess veld condition in three grassveld types in Natal was investigated. Three plots were assessed four times on each of three occasions during a growing season. Because basal cover tends to be low, and since it is binomially distributed, it is a poor statistic for rapid techniques. Measuring the proportions of ecological groups and the species composition score has satisfactory precision. On 19 out of 20 occasions the composition score obtained from assessing a single plot once lies within ± 4,5 units of a large sample mean which may range between 0 and 100 units. Assessments should be done during the growing season, and standardised with respect to plant phenology, burning and mowing.

Uittreksel

Die presiesheid van ‘n ratse tegniek wat voorheen ontwikkel is om veldtoestand in drie grasveltipe in Natal te bepaal is ondersoek. Drie persele is elkeen by drie geleenthede gedurende die groeiseisoen vierkeer gewaardeer. Omdat basaalbedekking geneig is om laag te wee, en sedert dit ‘n binomiale verspreiding het, vir ratse tegniëke is dit ‘n siegte statistiek. Meting van die proporsie ekologiese groepe en spesiesamestellingtelling het genoegsame presiesheid. Op 19 van 20 geleenthede behoort die sames tellingtelling, wat een keer bepaal van ‘n enkele perseel is, binne ± 4,5 eenhede van die gemiddelde van baie bepalings te wees. Die gemiddelde het ‘n moontlike omvang van 0 tot 100 eenhede. Bepalings behoort gedurende die groeiseisoen uit re voer word en moet met betrekking tot plantfenologie, veldbrand en veldsny gestandardiseer.

Notes

Present address: Dept. of Pasture Science, University of Natal, P.O. Box 375, Pietermaritzburg 3200