Effects of disturbance by fire and tillage on the water relations of selected mountain fynbos species

The effects of fire and tilling on the water relations of three mesic mountain fynbos species, Leucadendron xanthoconus (Proteaceae), Erica cristata (Ericaceae) and Chondropetalum hookerianum (Restionaceae), were investigated. Measurement of the diurnal pattern of xylem pressure potential in young plants of a postfire community showed that tilling of the soil was associated with an increase in the availability of water, and with less stressed conditions in the Leucadendron and Erica plants. Chondropetalum seedlings, however, were equally stressed on both of these burned treatments. Relative to their mature counterparts in the unburned vegetation, Erica and Chondropetalum of the burned but untilled treatment were more stressed, whereas the Leucadendron plants showed no significant difference. The observed patterns of stress are interpreted in terms of the reduced vegetational cover following tilling, and the different rooting and seedling establishment strategies displayed by each of the investigated species. Findings of this study suggest that consideration of an altered water regime may be an important part of the management and conservation planning which regulates human impact on fynbos vegetation