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Accueil du site → Doctorat → Allemagne → 2013 → Vegetation und Futterqualitätsaspekte des kommunalen Graslandes im Owamboland/Namibia : Bestimmungsgründe und Entwicklungsmöglichkeiten

Universitat Giessen (2013)

Vegetation und Futterqualitätsaspekte des kommunalen Graslandes im Owamboland/Namibia : Bestimmungsgründe und Entwicklungsmöglichkeiten

Ingrid Christian

Titre : Vegetation und Futterqualitätsaspekte des kommunalen Graslandes im Owamboland/Namibia : Bestimmungsgründe und Entwicklungsmöglichkeiten

Vegetation and forage quality aspects of the communal grassland in Owamboland/Namibia : determination factors and development options

Auteur : Ingrid Christian

Université de soutenance : Universitat Giessen

Grade : Doctor of Philosophy (PhD) 2013

Résumé
In order to assess determination factors and development options of communal pasture grounds in North-Central Namibia research was carried out into the relevant effects of two commercial pasture management systems and the communal pasture utilisation practice simultaneously. Research was carried out in three research areas and comprised monitoring of the coverage rates of the vegetation and edaphic factors as well as recording of pasture yields, the quality of available feeds and stocking rates. The management systems of two farms, representing two commercial pasture management systems – ‘Holistic Resource Management’ and ‘Controlled Selective Grazing’ were analysed. In the communal area a farming system analysis was carried out as an equivalent. In order to obtain definiteness on pasture assessment existing pasture assessment methods were examined, evaluated and developed further. In order to achieve results of general validity the research was planned in a way that further information could be obtained on important interactions, socio-economical conditions and on the application of research results (= perception and acceptance) by the different user groups. The results can be summarized as follows : 1. With the pasture assessment method of the Point Transect data on the current condition of the pasture allowing conclusions on the intensity of utilisation were ascertained. The Area Transect was less time consuming but more meaningful through the inclusion of edaphic factors and therefore suitable for long-term monitoring. 2. High vegetation coverage rates subject to high grazing pressure according to HRM criteria were achieved with sufficient precipitation (> 300mm) – close to the local average rainfall – and with perennial grass species as predominant part of the grass coverage rate. In terms of rainfalls below average and predominant annual grass species relatively high vegetation coverage rates were subject to low grazing pressure. 3. Grass species of communal pasture grounds were persistent since coverage rates of locations with an initially low coverage rate decreased relatively less in coverage than locations with an initially higher coverage rate. 4. The elasticity of the arid and semi arid pasture grounds was evidently higher than the one on which calculations for stocking rates were based by representatives of the conventional pasture management practise (= ‘Controlled Selective Grazing’). 5. In the commercial sector under controlled grazing independent from different management systems weather conditions influenced pasture yields to a larger extent. In the communal sector, however, causes of yield decline and of decrease in species diversity were found in interactions between the variability of rainfalls and uncontrolled grazing. 6. ‘Holistic Resource Management’ was more productive than the system of ‘Controlled Selective Grazing’ because of the more intensive utilization of the pasture. On short term yield reduction through the intensive utilization by HRM was not evident in the following vegetation periods. 7. The comparison of methods to assess pasture forage quality showed that with the enzymatical method compared to the in vitro rumen fluid method the digestibility of organic substance was underestimated by approx. 10%. The cause is evidently to be found in high contents of lignin in the feed leading to ADF figures up to > 50% and ADL figures up to > 4%. 8. It was concluded from the forage quality analysis that the dynamic of the fibre concentrations – ADF and ADL concentrations – as well as the crude protein concentrations are valid indicators to evaluate the intensity of grazing. 9. The relevance of HRM for communal pasture grounds turned out to be relatively high, since the holistic approach of the grazing system paid minor attention to the decrease of stocking rates and thereupon allowed to take traditional constraints of communal grazing practice into consideration.

Mots clés : semi-arid pasture grounds , monitoring , vegetation coverage rate, forage quality , pasture management ; semi-aride Weiden , Monitoring , Deckungsgrad , Futterqualität , Weidemanagement

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Page publiée le 16 novembre 2013, mise à jour le 8 janvier 2019