Impact of tree crowns on grass quality and structure in a semi-arid rangeland in southwestern Zimbabwe

Abstract

Understorey areas in semi-arid rangelands can be a habitat for high-yielding palatable grasses. Selective grazing of these grasses can result in their replacement by less palatable grass species, normally found in open areas. An experiment, at Matopos Research Station, sought to establish whether the understorey micro-environment improves the quality and structure of open-area grasses that invade understorey areas. Herbaceous quality (ash, nitrogen, neutral detergent fibre, acid detergent fibre) and structure (height, leaf:stem ratio, tuft circumference, tiller number) of the dominant species of open-area grasses were measured. Tuft circumference and tiller numbers were the only measurements that differed between the same species growing under tree crowns and in open areas in one of the three sites. The appropriate management responses to changes in understorey species composition are discussed.

Keywords: Acacia karroo; botany; grass; grass quality; grass structure; Matopos Research Station; palatability; rangelands; re-establishment; selective grazing; semi-arid; Terminalia sericea; tree crowns; trees; understorey grasses; Zimbabwe; ash; change; composition; fibre; grasses; grazing; habitat; management; measurements; neutral detergent fibre; nitrogen; numbers; rangeland; response; species composition; structure; tiller; understorey

African Journal of Range & Forage Science, Vol. 15(3), pp. 97–101