Comparative post-fire water relations of selected reseeding and resprouting fynbos plants in the Jonkershoek Valley, Cape Province, South Africa

R.E. Smith, D.M. Richardson
1990 South African Journal of Botany  
Leaf area development has been proposed as a simple predictor of post-fire streamflow response in the mountain catchments of the south-western Cape, South Africa. Implicit in this proposal is the assumption that transpiration rates per unit leaf area of reseeders and resprouters are similar. This assumption was tested by studying the water relations of selected fynbos plants after a fire in a mountain catchment in the Jonkershoek Valley near Stellenbosch for nearly two years. Stomatal
more » ... Stomatal conductances and xylem pressure potentials were measured and transpiration rates were estimated for three reseeding species and four resprouting species. There was no clear difference between the daily transpiration rates of reseeding and resprouting plants. The shallow-rooted resprouters responded similarly to the reseeders; moderate water stress (-3 to -4 MPa) and reduced transpiration « 1 mmol m-2 S-1) were experienced during the first two summers after fire. The deeprooted resprouters did not show water stress during summer, and transpiration rates were moderate throughout the year. Annual patterns of water use per unit leaf area were similar for reseeders and resprouters. Leaf area may therefore be used as a simple predictor of post-fire streamflow response. Daar is voorgestel dat blaaroppervlakontwikkeling as 'n eenvoudige voorspeller van na-brandse stroomvloeireaksie in die bergopvanggebiede van die Suidwes-Kaap, Suid-Afrika, kan dien. Hierdie voorstel impliseer dat die transpirasie-tempo per eenheid oppervlakte van saaiers en uitspruiters soortgelyk is. Hierdie veronderstelling is getoets deur die waterverhouding van sekere fynbos plante te bestudeer vir 'n tydperk van amper twee jaar na 'n brand in 'n bergopvanggebied in die Jonkershoekvallei naby Stellenbosch. Blaarkonduktansie en xileemdrukpotensiaal is gemeet en die tranpirasie-tempo van drie saaierplantsoorte en vier uitspruiterplantsoorte is beraam. Daar was geen noemenswaardige verskil tussen die daaglikse transpirasie-tempo's van saaiers en uitspruiters nie. Die uitspruiters met vlak wortelstelsels en die saaiers het 'n soortgelyke reaksie getoon; in albei gevalle is matige waterspanning waargeneem (-3 tot -4 Mpa) en het verminderde transpirasie plaasgevind « 1 mmol m-2 S-1) gedurende die eerste twee somers na die brand. By die diepgewortelde spruiters is waterspanning nie gedurende die somer waargeneem nie en transpirasie-tempo's was matig dwarsdeur die jaar_ Die jaarlikse patroon van waterverbruik per eenheid blaaroppervlakte was soortgelyk vir saaiers en uitspruiters. Blaaroppervlakte kan dus gebruik word as 'n eenvoudige voorspeller van na-brandse stroomvloei reaksie.
doi:10.1016/s0254-6299(16)31007-9 fatcat:vi3rwsqignap3ng7zpk7ulqrsm