Preliminary results on species selection by animals on sour grassveld

Roos, J. H.; Rethman, N.F.G.; Kotzé, G.D.

doi:10.1080/00725560.1973.9648699

Cited by 5 publications

(2 citation statements)

References 2 publications

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“…With a sampling intensity of 450 pointobservations for each treatment combination on each sampling date, and an abundance of the species in question, such discrepancies cannot be attributed to inadequate sample size. Thus it seems that although the technique has commonly been used (for example, Kruger & Edwards, 1972 ;Roos, Rethman & Kotze, 1973;Danckwerts, Aucamp & Barnard, 1983) it is not always reliable. In a situation where repeated observations are made in grazed veld, visual estimation of the degree of utilization is difficult, probably because the base-line, that is, the conception of the appearance of a previously grazed but currently un grazed plant, may change for each sampling occasion.…”

Section: Relative Utilizationmentioning

confidence: 99%

Reaction of three veld grasses to different schedules of grazing and resting. 1. Patterns of shoot growth

Barnes¹

1989

South African Journal of Plant and Soil

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Seven defoliation treatments involving grazing at three-weekly intervals with sheep until mid-January or midMarch, or for the whole growing season, at each of two stocking rates, or resting for the whole growing season, were applied on veld during the 1985-86 season. Mass per unit basal area of the shoot components, green leaf, dry leaf and stem plus inflorescence of populations of tufts of the three most abundant grass species, Heteropogon contortus, Themeda triandra and Trachypogon spicatus, was determined at intervals during the periods of rest. Relative utilization was estimated by observations on samples of tufts after each grazing occasion. Within treatments, growth patterns during rest periods of the populations of the three species were broadly similar, though production per unit tuft basal area decreased in the ratio 100:65:40 for Trachypogon, Themeda and Heteropogon respectively. Using the cumulative growth curves, absolute and relative growth rates for the whole shoot and green leaf in certain of the treatments were established. A pervasive feature of the growth patterns was a tendency towards senescence in the latter half of the growing season. Defoliation by grazing was only partially effective in delaying this process. Amounts of herbage of each species which were present at the start of the rest periods beginning in mid-January and mid-March were generally proportional to the stocking pressure prior to the rest. However, within species, there was a poor correlation between this result and estimated relative utilization.Sewe ontblaringsbehandelings insluitend beweiding met tussenposes van drie weke met skape tot middel Januarie of middel Maart, of vir die hele groeiseisoen, elkeen met twee veeladings, of rus vir die he Ie groeiseisoen, is op veld gedurende die 1985-86-seisoen toegepas. Massa per eenheid pol basale bedekking van die loot komponente, groenblaar, droe blaar en stingel-plus-bloeiwyse van populasies van polle van die drie mees algemene grasspesies, Heteropogon contortus, Themeda triandra en Trachypogon spicatus, is op intervalle gedurende die periode van rus bepaal. Relatiewe benutting is deur opnames in steekproewe van polle na elke beweidings-geleentheid geskat. Binne behandelings, was groeipatrone gedurende rusperiode van populasies van die drie spesies naastenby dieselfde, alhoewel produksie per eenheid basale bedekking in die onderskeie verhoudings 100:65:40 afgeneem het vir Trachypogon, Themeda en Heteropogon. Met gebruik van die kumulatiewe groeikurwe is absolute en relatiewe groeitempo's vir die hele loot en groenblaar in sekere behandelings vasgestel. 'n Opvallende eienskap van die groeipatrone was die neiging tot veroudering in die laaste helfte van die groeiseisoen. Ontblaring deur middel van beweiding was net deels effektief om die proses te vertraag. Die hoeveelheid materiaal van elke spesie teenwoordig by die begin van die rusperiode wat in middel Januarie en middel Maart begin het, was oor die algemeen in verhouding met die weidruk voor die rusperiode. Nogtans was daar bi...

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Section: Relative Utilizationmentioning

confidence: 99%

Reaction of three veld grasses to different schedules of grazing and resting. 1. Patterns of shoot growth

Barnes¹

1989

South African Journal of Plant and Soil

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show abstract

“…They also measured the height of the observed plants and used mean height of species between certain grazing treatments as an additional 1 indication of relative utilisation. Roos, Rethman & Kotze (1973), also working on veld in the Transvaal, recognised three levels of utilisation, namely, less than !5% utilisation, 16 to 30% utilisation, and over 50% utilisation. The relevant coefficients were 1/10, 1/3 and 1.…”

Section: F -Number Of "Fully Grazed" Plants Of a Species X 100mentioning

confidence: 99%