Waterbalans studies in geselekteerde subhabitatte van 'n Burkea-Savanna
| dc.contributor.advisor | Opperman, D. P. J. | |
| dc.contributor.advisor | Van Rooyen, D. J. | |
| dc.contributor.author | Moore, Arno | |
| dc.date.accessioned | 2017-01-26T11:23:28Z | |
| dc.date.available | 2017-01-26T11:23:28Z | |
| dc.date.issued | 1980-11 | |
| dc.description.abstract | English: During this project the field-water balances in four subhabitats of the Burkea savanna in Phase II of the Savanna Ecosystem Project at Nylsvley were studied.The project included a study of the water redistribution patterns in the soil, the determination of the changes in soil moisture storaqe over depth as well as the determination of evapotranspiration losses in the E. pallens, O. pulchra, G. flavescens and B. africana subhabitats. The water-use efficiencies in the E. pallens, O. pulchra and G. flavescens subhabitats in terms of mm Et (daily)/ unit leaf area for the species E. pallens association (grasses), O. pulchra and G. flavescens, and for the subhabitats as a whole, were calculated. Water is the basic driving force and limiting factor in the Burkea-savanna, anq a basic knowledge of the natural field-water balances is essential for further plantphysiological and other research aimed at the understanding of the natural plantphysiological processes in the Burkea savanna ecosystem. There is a high degree of root -integration in the Burkea savanna, and the three subhabitats E. pallens, O. pulchra and G. flavescens were hydrologically isolated by means of poly-ethylene strips in order to interpretate the hydrological processes on a subhabitat basis. The soil-water balance, based on changes in soil moisture storage, was used in calculating evapotranspiration losses. Soil-water content was, determined gravimetrically and by means of the neutron scattering technique. The neutron probe used in this study was calibrated in the field for Nylsvley conditions. Leaf area determination was necessary as a criterium against which the water-use in the isolated subhabitats could be evaluated. Different methods and techniques were used in determining the leaf area of grasses, 0.pulchra and G. flavescens. The results are given as soil-water redistribution curves, daily evapotranspiration losses (mm) and water-use efficiency in terms of daily Et (mm)/unit leaf area. The redistribution curves show that water-uptake occurs mainly in the top 60 cm of the soil profile in the E. pallens and O. pulchra subhabitats. Deeper in the soil profiles water was available for uptake even throughout the dry months. In the G. flavescens and B. africana subhabitats water-uptake took place throughout the soil profile and no water was available during the dry months. Redistribution of water in the soil profile was rapid and a shower of + 50 mm redistributed within + 12 hours to a depth of 90 cm. No statistical meaningful differences in evapotranspiration losses were fOundĀ· between the four subhabitats. There were, however, some tendencies and it seemed that the evapotranspiration losses were the highest from G. flavescens subhabitats, followed by B. africana subhabitats, E. pallens subhabitats and finally O. pulchra subhabitats. This was found for periods from four to seven days after a shower. As far as water-use efficiency is concerned, no statistical meaningful difference was found. It appeared, however, that G. flavescens used the most water per unit leaf area. Highly statistical meaningful differences were found between water-losses from sites with a transpiring grass cover; sites with a non-transpiring (dead)_grass cover; and sites with no grass cover (bare). Unfavourable weather-conditions resulted in smaller differences than could be expected under conditions of desication. | en_ZA |
| dc.description.abstract | Afrikaans: Tydens hierdie projek is die veldwaterbalanse in vier subhabitatte van die Burkea-savanna in Fase II van die van die Savanna Ekosisteemsprojek wat te Nylsvlei natuurvaat onderneem word, bestudeer. Die projek het 'n studie van die waterherverspreidingspatrone in die grond, die bepaling van die veranderings in grondvogvoorraad oor diepte asook evapotranspirasie-verliese in die vier subhabitatte E. pallens, O. pulchra, G. flavescens en B. africana behels. Die waterverpruiksdoeltreffendheid in die eersgenoemde drie subhabitatte is in terme van mm Et per dag/eenheid B.O. vir die spesies E. pallens assosiasie (grasse), O. pulchra en G. flavescens asook op 'n subhabitatsbasis bereken. Water is die primĆŖre dryfkrag en ook beperkende faktor in die Burkea - savanna en 'n basiese kennis van die natuurlike veldwaterbalanse is noodsaaklik vir verdere plantfisiologiese en ander navorsing wat daarop gemik Ls om die natuurlike plantfisiologiese prosesse in die Burkea savanna ekosisteem te verstaan. Wortelintegrasie kom tot 'n groot mate in die Burkea - savanna voor, en die drie subhabitatte E. pallens, O.pulchra en G. flavescenĀ§ is met behulp van poli-etileenstroke hidrologies geĆÆsoleer, sodat die hidrologiese prosesse op In subhabitat basis geĆÆnterpreteer kOn word. Die grondvogbalans, wat gebaseer is op die verandering in grondvogvoorraad oor tyd, is toegepas by die berekening van evapotranspirasie-verliese. Grondvogbepaling is gravimetries en deur van neutronvogmetings tegnieke gebruik te maak, gedoen. Vir die doel van neutronvogmeting, is die betrokke apparaat vir Nylsvlei-toestande in die veld gekalibreer voor gebruik. Blaaroppervlaktebepaling was nodig ten einde 'n kriterium te verkry waarteen waterverbruik in die geĆÆsoleerde subhabitatte geĆ«valueer kon word. Verskillende metodes en tegnieke is gebruik by die bepaling van die blaaroppervlakte van grasse in die algemeen, O. pulchra en G. flaveseens. Die resultate is verwerk en word weergee as grondwaterherverspreidingskurwes, daaglikse evapotranspirasieverliese (mm) en waterverbruiksdoeltreffendheid in terme van mm/Et per dag/eenheid B O. Wat die herverspreiding van grondwater betref, blyk dit dat by die E. pallens en O. pulchra subhabitatte, wateropname hoofsaaklik in die boonste 60 cm van die grondprofiel voorkom, terwyl vog in die ondergrond selfs in die droogste maande nog vrylik beskikbaar is. By die subhabitatte B. africana en G. flavescens vind wateropname deur die hele grondprofiel plaas. Waterherverspreiding in die grondprofiel vind vinnig plaas en na 'n reĆ«nbui van + 50 mm herversprei water binne + 12 uur tot op 'n diepte van 90 cm. Wat evapotranspirasie-verliese betref, bestaan daar nie statisties betekenisvolle verskille tussen die vier subhabitatte nie. Sekere tendense bestaan wel en dit blyk dat Et- verliese in G. flavescens subhabitatte die hoogste is, gevolg deur B. africana subhabitatte, E. pallens subhabitatte en laastens O. pulchra subhabitatte. Dit geld vir periodes van vier tot sewe dae na 'n reĆ«nbui. Wat waterver9ruiksdoeltreffendheid betref, is ook geen statisties betekenisvolle verskille tussen die W V D van grasse, Ochna en Grewia verkry nie, hoewel dit uit die resultate blyk dat Grewia die meeste water per eenheid blaaroppervlakte geĆ«vapotranspireĆ«r het. Hoogs betekenisvolle verskille in vogverliese vanaf persele met 'n transpirerende grasb.edekking; 'n nie-transpirerende grasbedekking; en geen grasbedekking nie, is gevind. Ongunstige weerstoestande het egter tot gevolg gehad dat die verskille nie so groot was as wat verwag kan word onder toestande van uitdroging nie. | af |
| dc.identifier.uri | http://hdl.handle.net/11660/5427 | |
| dc.language.iso | af | af |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Dissertation (M.Sc.Agric. (Animal, Wildlife and Grassland Science))--University of the Free State, 1980 | en_ZA |
| dc.subject | Soil moisture -- South Africa | en_ZA |
| dc.subject | Water quality (Hydrology) | en_ZA |
| dc.subject | Savannas -- South Africa | en_ZA |
| dc.title | Waterbalans studies in geselekteerde subhabitatte van 'n Burkea-Savanna | af |
| dc.type | Dissertation | en_ZA |