Seasonal progression of plant water relations in fynbos in the western Cape Province, South Africa.

Plant xylem pressure potentials and leaf conductances to water loss were measured in the spring and summer at two sites in the western Cape Province, Republic of South Africa. The measurements were to test the hypothesis that the fynbos of South Africa was equivalent to the chaparral of California, therefore a period of plant water stress, similar to the period measured in chaparral species, should occur in flynbos species during the dry summer. The measurements indicated little or no plant water stress in most fynbos species at both sites. The sites were similar in plant water relations in spite of a more than twofold difference in annual precipitation. The minor differences in plant water relations can be explained in terms of different vegetation cover and different vapor pressure deficits during the measurements. The results support the conclusion that the arid fynbos may be equivalent to chaparral, but the majority of the fynbos is equivalent to coniferous and broad-leaved evergreen forest in California.