Seasonal changes in root biomass, root/shoot ratios and turnover in two coastal grassland communities in Transkei

Abstract

Estimates of root standing crop were made at approximately 3-month intervals from two grassland communities each with three treatments. Roots were extracted to a depth of 0.5 m using a corer and then separated from the soil by wet sieving and flotation. Peak standing crops of 4487 g m− 2 and 4737 g m− 2 for the two communities respectively, in autumn or early winter, were high relative to previously published figures. Lowest standing crops were recorded in summer. Treatment effects were masked by the high variation of the data. These high yields gave rise to high root/shoot ratios, which were decreased with aging of the sward and grazing of the above-ground biomass. Turnover times of 2–3 years were recorded. The need for root-depth profiles to facilitate standardization of results between researchers is emphasized. Beramings van die wortel biomassa is ongeveer 3-maandeliks op twee graslandgemeenskappe, onderwerp aan drie behandelings gemaak. Die wortels is met ‘n grondboor tot op ‘n diepe van 0.5 m verwyder en daarna van die grond geskei deur sifting en flotasie. Opbrengste van 4487 g m− 2 en 4737 g m− 2 vir die twee gemeenskappe in die herfs of vroeë winter was hoog in vergelyking met gepubliseerde syfers. Die laagste opbrengs is in die somer verkry. Die invloed van behandeling was onduidelik as gevolg van die hoë variasies in die data. Die hoë opbrengste het hoë wortel/loof verhoudings tot gevolg gehad, wat afgeneem het met toenemende ouderdom van die grasveld en beweiding van die bogrondse biomassa. Wortel vervanging van tussen 2 en 3 jaar is gevind. Die behoefte aan wortel-diepte profiele om standardisering van resultate tussen navorsers te bewerkstellig, word beklemtoon.