A weighted key species method for monitoring changes in species composition of Highland Sourveld

Abstract

The use of key species for indexing veld condition in relation to the fire/grazing impact has potential for monitoring change in the Highland Sourveld of Natal. Weightings are calculated for previously identified key species. A weighted‐averages approach is used in a modified Weighted Key Species Method of indexing veld condition. Veld condition indices calculated using the method are highly correlated with rankings along a previously identified grazing gradient (r=0,85). Weightings are provided for indicator species that can be generally used for monitoring vegetation changes in the Highland Sourveld. The method has the advantage of being able to determine the position of a sample site on a grazing gradient, and thereby make inferences as to the grazing/burning history of the site.

Die gebruik van sleutelspesies vir die indeksering van die verwantskap tussen veldtoestand en die invloed van brand of beweiding hou moontlikhede vir die monitering van verandering in die Hoogland‐suurveld van Natal in. Wegings is vir vorige geïdentifiseerde sleutelspesies bereken. Geweegde gemiddeldes word in ‘n aangepaste Geweegde‐sleutelspesiemetode vir die indeksering van veldtoestand gebruik. Die indekse vir veldtoestand wat met die metode bereken is, is hoogs gekorrelcer met die rangordes langs ‘n voorheen‐geidentifiseerde bewei‐dingsgradient (r=0,85). Wegingsfaktore word vir indikatorspesies wat algemeen vir plantegroeiverandering in die Hoogland‐suurveld gebruik kan word, voorsien. Die voordeel van die metode is dat die posisie van ‘n monsterperseel op ‘n beweidingsgradient bepaal kan word waardeur afleidings oor die monsterperseel se geskiedenis van beweiding/brand, gemaak kan word.

Additional index words:

• Grazing gradient
• ordination
• range condition