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University of Fort Hare (2013)

Long-term ecological effects of rangeland burning, grazing and browsing on vegitation and organic matter dynamics

Ratsele Clement Ratsele

Titre : Long-term ecological effects of rangeland burning, grazing and browsing on vegitation and organic matter dynamics

Auteur : Ratsele Clement Ratsele

Université de soutenance : University of Fort Hare

Grade : DOCTOR OF PHILOSOPHY IN PASTURE SCIENCE 2013

Résumé
To proffer a sustainable solution to ecological degradation in rangeland ecosystems as a consequence of fire, grazing and browsing, an understanding of rangeland ecological processes is vital. Due to the complexity of ecological processes and their interrelationships, it is usually difficult or expensive to directly measure status of ecological processes. Therefore, biological and physical characteristics are often used to indicate the functionality of ecological processes and site integrity. Long-term effects of fire, grazing and browsing on characteristics of the vegetation and organic matter and their subsequent effects on selected rangelands ecosystem ecological processes was conducted at Honeydale section of the University of Fort Hare farm in the Eastern Cape Province of South Africa and Matopos Research Station in Zimbabwe. In this study, attributes of biotic community integrity (species richness, composition and diversity), soil stability (basal cover, standing dead grass biomass, tuft to tuft distance, tufts diameter, canopy distance and stem to stem distance), productivity and plant vigour (grass yield, total canopy volume, plant height, canopy height, canopy diameter, main stem diameter, sprouts diameter and number of sprouts) and hydrologic function and nutrient cycling (grass litter biomass, soil organic carbon and microbial biomass carbon) were used to estimate long-term effects of burning, grazing and browsing by goats on the functionality of ecological processes in the rangeland ecosystem. Burning did not have differential effect on grass species richness (P>0.05), woody species diversity as well as compositional percentage for D.eriatha, C.plurinodis, S.fimbriatus, A.karro and E.rigida. Burning increased decreasers and increaser II species proportions and reduced (P ≤ 0.05) grass yield, total canopy volume, tree height, canopy height main stem diameter and sprouts diameter. Long-term burning, grazing, and goats browsing had differential effects on site stability. The effects on basal cover, tuft to tuft distance, tufts diameter, canopy distance and basal distance as a consequence of long-term burning, grazing, and goats browsing were not significantly different, whereas the effects on standing dead grass biomass as a result of long-term burning frequencies were significantly different. Long-term effects of burning followed by ten-year period of fire exclusion had significantly different effects on tuft-tuft distance but did not have statistically different effects on tufts diameter, canopy distance and basal distance. Long-term burning grazing and browsing had significantly different effects on attributes of hydrologic functions and nutrient cycling in the rangeland ecosystem (grass litter biomass, SOC and BMC). Long-term effects of burning followed by ten-year period of fire exclusion had significantly different effects on grass litter biomass, and SOC. Through their effect on vegetation and organic matter characteristics, burning, grazing and browsing could influence functionality of selected rangeland ecological processes such as biological community integrity, productivity and plant vigour, site stability, hydrologic function and nutrient cycling.

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