Phytomass and ecological significance of Chrysocoma ciliata L. within the Lets’eng-la-Letsie catchment area of Lesotho, southern Africa

Abstract

The Lets’eng-la-Letsie wetland is an official Ramsar site, but the wetland and upland catchment areas suffer from overgrazing, erosion and over exploitation. Chrysocoma ciliata has a reputation as an unpalatable invader and is particularly common on the drier northern slopes. The objectives of the study were to quantify the phytomass of this shrub with the aid of a developed allometric phytomass quantification technique and to evaluate the ecological significance of this shrub within the area. Highly significant (p < 0.001) positive regressions with coefficients of determinations as high as r² = 0.94 between phytomass and plant canopy diameter were achieved.
The upland slopes support a high density of more than 35 000 C. ciliata plants ha⁻¹ with a phytomass of more than 3 600 kg DM ha⁻¹ and a correspondingly low herbaceous phytomass of 446.57 kg DM ha⁻¹. The edible parts of the plants (flowers, leaves and shoots <2.0 mm in diameter) were estimated to be 1 198 kg DM ha⁻¹, with a crude protein content of 8.84%. There was evidence that C. ciliata is intolerant of wet conditions and the degradation of the catchment areas will result in drier soil profiles, which will favour the further spread of this species.

Keywords: allometric, land degradation, livestock grazing