Fire is a recurrent disturbance that removes above ground vegetation in many locations throughout the world, including the Sydney region. Many species in fire-prone locations, and most species in the Sydney region, form soil seedbanks and regenerate through post-fire germination. However, a germination response is determined by the fire regime acting as a selective pressure over a sufficient period of time, rather than a single fire. The components of the fire-regime are intensity, season, type and frequency. The natural fire regime is dominated by warm-season fire, but management burning is conducted in cooler seasons. Cool season burning produces lower levels of germination than warm season fires in a number of locations with Mediterranean-type climate, but the effects of cool season burning on species composition in the relatively aseasonal Sydney region is unknown. An experimental approach was adopted to address this lack of knowledge. Fire can be simulated using heat shock and smoke (fire cues), and the seasonal factors of temperature and water availability can be reproduced in the laboratory. I have investigated the effect of various combinations of heat shock and smoke, of various pre-and post-fire cue temperatures, of prefire cue hydration status, of various post-fire cue water availabilities, and of accelerated aging before application of fire cues on germination of a number of species forming soil seedbanks in the Sydney region. A degree of primary dormancy was overcome in most species by the combination of heat shock and smoke in the current investigation. Fire intensity is expected to influence germination, as germination of most species was increased by the combination of heat shock and smoke within a narrow heat shock range.The interaction between ambient temperature and the level of heat shock may affect germination. Soil water content, and thus seed moisture content at the time of a fire may interact with the level of heat shock to affect both germination and survival of a seed. The age of a seed may also affect its germination response to fire. The above factors are predicted to affect the germination of species differently, and thus season of fire is expected to alter species composition. Such predictions can be readily field-tested / Doctor of Philosophy (PhD)

Fire is a recurrent disturbance that removes above ground vegetation in many locations throughout the world, including the Sydney region. Many species in fire-prone locations, and most species in the Sydney region, form soil seedbanks and regenerate through post-fire germination. However, a germination response is determined by the fire regime acting as a selective pressure over a sufficient period of time, rather than a single fire. The components of the fire-regime are intensity, season, type and frequency. The natural fire regime is dominated by warm-season fire, but management burning is conducted in cooler seasons. Cool season burning produces lower levels of germination than warm season fires in a number of locations with Mediterranean-type climate, but the effects of cool season burning on species composition in the relatively aseasonal Sydney region is unknown. An experimental approach was adopted to address this lack of knowledge. Fire can be simulated using heat shock and smoke (fire cues), and the seasonal factors of temperature and water availability can be reproduced in the laboratory. I have investigated the effect of various combinations of heat shock and smoke, of various pre-and post-fire cue temperatures, of prefire cue hydration status, of various post-fire cue water availabilities, and of accelerated aging before application of fire cues on germination of a number of species forming soil seedbanks in the Sydney region. A degree of primary dormancy was overcome in most species by the combination of heat shock and smoke in the current investigation. Fire intensity is expected to influence germination, as germination of most species was increased by the combination of heat shock and smoke within a narrow heat shock range.The interaction between ambient temperature and the level of heat shock may affect germination. Soil water content, and thus seed moisture content at the time of a fire may interact with the level of heat shock to affect both germination and survival of a seed. The age of a seed may also affect its germination response to fire. The above factors are predicted to affect the germination of species differently, and thus season of fire is expected to alter species composition. Such predictions can be readily field-tested / Doctor of Philosophy (PhD)

Thesis (MSc (Conservation Ecology and Entomology)--University of Stellenbosch, 2006. / The Restionaceae is a dominant family in the Fynbos Biome, an area in which fire plays a role as an important disturbance, yet little is known about their population dynamics. Two species of the Restionaceae (Thamnochortus insignis and T. erectus) are economically important as thatching reed and differ in their life-histories. This study aims to determine the effects of variation in life history (sprouter vs. non-sprouter) on the population structure and dynamics of T. erectus (“wyfies riet”, sprouter) and T. insignis (“mannetjies riet”), a non-sprouting species. A matrix-modelling approach based on field data collected by Ball (1995) is used to determine population growth rates, stable stage distributions and stage sensitivity and elasticity for the two species with no disturbance present. The sprouter (T. erectus) shows a positive population growth rate (λ >1) and greater persistence within all stages. The non-sprouting species (T. insignis) shows a negative population growth rate (λ <1) between disturbances as well as greater seed production, germination and growth between stages. Based on the population dynamics of these two species, further research was done to understand the effect of disturbance (harvesting and fire) on these species. A matrix modelling approach was used to determine which disturbance frequency maximises population output and success. Harvesting as well as fire results in a decline in T. insignis populations. A five year frequency for harvesting results in the greatest output of adult plants with the lowest effect on the population, and a fire frequency of 50 to 65 years is recommended. Testing indicates that the model underestimates the number of adults in the population and thus the model is conservative. T. erectus populations grow despite fire or harvesting; thus any reasonable harvesting (3-5 year frequency) and fire (10+ years between fire) regime would ensure population persistence. As data were limited it was not possible to test the results although T. erectus appears resilient to disturbance and therefore a predetermined regime is not as important as in T. insignis. Recommendations to farmers are made based on these results.

In this thesis, aspects of the reproductive biology of four Banksia species that display in various combinations all the life histories currently recognised in the genus were compared. Species like banksias, from fire prone regions of the world are typically characterised by life histories (traits and organs) that in reference to fire response allow them to be classified as seeders or sprouters. Plants killed by fire and that rely on seed for regeneration are called seeders and those that have the capacity to survive fire and produce vegetative sprouts are called sprouters. The species are Banksia ericifolia, Banksia integrifolia, Banksia oblongifolia, and Banksia serrata. The study was conducted in the Sydney region of Australia, which was arbitrarily divided into North, Central, and Southern provinces for sampling across species. It has been generally hypothesised that several traits are likely to be associated with seeders and sprouters. However, these traits were not always clearly apparent from the author’s studies. It is argued one reason for the anomalies in the expected associated traits is a result of a tendency to assume a evolutionary history that is based on fire as being the primary selection pressure. / Doctor of Philosophy (PhD)

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Surface fires are known to affect trees of different species differently, depending on the capacity of the bark to shield the cambium from heat. Tree bark characteristics differ among species and thus potentially influence the protective ability against cambium damage. The objectives of this study were to compare the protective role of bark against fire for selected indigenous and exotic species in the Western Cape, South Africa, and to investigate post-fire growth impacts following surface fire damage on Pinus radiata. In the first part of the study, trees were felled and billets of 25 cm height harvested from different heights along the trunk. Bark thickness, compass direction, stem diameter at breast height, bark moisture content and relative height of the sample in the stem were tested for their effect on heat insulation capacity of bark. Heating experiments were conducted at 400°C on the fresh billets with intact bark. Time to heat the cambium to lethal 60°C was determined. The second part of the study investigated the role of bark surface topology, bark density and bark chemical composition for its fire resistance. The same size billets were harvested from the lower trunk section of selected species. Surface topology was characterised by means of x-ray based computer tomography, density by moisture saturation method and bark chemical composition by thermo-gravimetrical analyses (TGA). The third part of the study investigated the impact of high intensity surface fires on growth of an 18 year old Pinus radiata plantation which was exposed to a ground fire 5 years prior to the analysis. Tree ring measurements were done on cores obtained by non-destructing coring method and various growth indices, based on yearly basal area increment (iBA) used to quantify growth response to the fire damage. Statistical analysis based on correlation, multi-model inference and multiple regression revealed no significant influence of compass direction and diameter at breast height. Heat resistance was mainly determined by bark thickness and to a lesser degree by moisture content. In several species relative height at the stem modulated the bark thickness effect. Higher up the stem bark of the same bark thickness offered less protection against heat. The results also suggest that in particular bark topology plays a role, while the correlations with bark density and chemical composition could not be secured statistically. A main finding was that fissures in the bark play a significant role. A regression model showed a significant influence of fissure width, fissure frequency and the minimum bark thickness to the cambium, which is a function of fissure depth. The results show that structural bark parameters are a necessary addition to explain heat resistance of bark. Statistical analysis employing one-way Anova and incorporating Tamhane’s T2 Post Hoc test revealed significant growth reductions following high intensity surface fire damage on Pinus radiata in the fire year with the impact being passed on to the following year. The recovery phase extended a two year period. During this time the trees showed increased diameter growth probably due to increased water availability. / AFRIKAANSE OPSOMMING: Dit is bekend dat oppervlakvure in bos-ekostelsels verskillende boomspesies verskillend affekteer, afhangende van die vermoë van bas om die kambium van hitte te beskerm. Baseienskappe verskil tussen spesies en het dus 'n potensiële invloed op die beskermende vermoë teen kambiumskade. Die doelwit van hierdie studie was om die beskermende rol van bas teen vuur te vergelyk tussen inheemse en uitheemse spesies in Wes-Kaapland, Suid Afrika asook om die na-vuur impak op groei te ondersoek met brandskade aan Pinus radiata. In die eerste deel van die studie is bome geoes en stompe van 25 cm lengte van verskillende hoogtes verwyder. Basdikte, kompasrigting, stompdiameter by borshoogte, basvoggehalte en die relatiewe hoogte van die stomp in die stam is getoets vir hul invloed op hitte-isolasiekapasiteit van bas. Verhittingseksperimente is gedoen teen 400 °C op die vars stompe wat steeds bas opgehad het. Die tyd om die bas tot by 'n skadelike 60 °C te verhit is bepaal. Die tweede deel van die studie het die rol van basoppervlaktopologie, basdigtheid, en die bas chemiese samestelling ondersoek in vuurweerstand. Dieselfde grootte stompe is geoes van die laer dele van die stam van uitgesoekte spesies. Oppervlaktopologie is bepaal deur middel van X-straal rekenaartomografie, digtheid deur die versadigingsvoggehaltemetode, en chemiese samestelling deur termo-gravimetriese analise (TGA). Die derde deel van die studie het die impak van hoë intensiteit oppervlakvure op groei van 18-jaar oue Pinus radiata ondersoek. Jaarringmetings is gedoen op inkrementboorsels wat nie-destruktief bekom is en verskeie groei-indekse, gebaseer op jaarlikse basale oppervlak aanwas, is gebruik om die groeireaksie op brandskade te kwantifiseer. Statistiese analise gebaseer op korrelasie, multi-model inferensie, en veelvuldige regressie het gewys dat kompasrigting en deursnee op borshoogte nie 'n beduidende invloed gehad het nie. Hitteweerstand was hoofsaaklik bepaal deur basdikte, en in 'n mindere mate basvoggehalte. By verskeie spesies het die relatiewe hoogte die basdikte-effek gemoduleer. Hoër in die stam het dieselfde dikte bas minder beskerming gebied as bas van laer in die stam. Die resultate impliseer dat basoppervlaktopologie ook 'n rol speel in hitteweerstand terwyl basdigtheid en chemiese samestelling nie 'n statisties beduidende rol gespeel het nie. 'n Belangrike bevinding was dat gleuwe of openinge in die bas 'n beduidende rol speel. 'n Regressiemodel wys dat 'n beduidende invloed deur gleufwydte, gleuffrekwensie en die minimum basdikte na die kambium. Die resultate wys dat strukturele basparameters 'n belangrike bykomende rol speel om hitteweerstand van bas te verduidelik. Die statistiese analise waar eenrigting ANOVA met Tamhane se T2 Post Hoc toets gebruik is toon dat ‘n beduidende groeivermindering teweeg gebring is in die Pinus radiata as gevolg van skade veroorsaak deur hoë intensiteit oppervlakvure waarvan die impak eers in die jaar na die vuur sigbaar was. Die herstelfase het oor twee jaar gestrek. Gedurende hierdie tyd het die bome 'n toename in deursneegroei getoon, waarskynklik as gevolg van verhoogde waterbeskikbaarheid.

The Lesotho highlands are unique in many ways yet are at risk from severe degradation, primarily as a result of grazing and burning. This study aimed to determine whether recent (last 10-15 years) burning and grazing practices in the Sani region of eastern Lesotho are sustainable for the long-term survival of tussock grasses in the alpine belt. It was hypothesized that the alpine tussock grasses of Lesotho are being burnt and grazed at a rate that does not enable them to adequately recover between burns. A GIS based burn frequency and extent map was produced and indicated many small patchy burns (<100m2) were occurring within the Lesotho border, yet large scale burning (>10 000m2) occasionally breached the escarpment edge. Selected sites were monitored to determine the rate of growth and recovery of Merxmuellera drakensbergensis tussocks for a three year period (January 2009- December 2011). Increases were observed in basal circumference, living basal area and standing biomass yet the average height decreased across all sites and was attributed to grazing. A burn frequency of 4 burns per decade was found to be the optimum for retaining the greatest biomass, while a lack of burning for more than 9 years was suggested to result in a decrease in biomass. The leaves observed at a third of the diameter required the least average time of 6.3 years to recover to pre-burn heights as they are sheltered from environmental impacts and grazing. The middle tillers generally required the most time to recover to pre-burn heights (7.1 years) as the greatest competition for resources may be found in the centers as well as high possibilities of fire damage. The current burning activities are considered sustainable under the current levels of grazing occurring. The current levels of grazing are not advisable, especially as livestock numbers are increasing and grazing of the Sani region is becoming continuous throughout the year. A shortening of the average height of individuals within M. drakensbergensis communities is found, while increases were observed in invasive species cover. This research will add to the knowledge of environmental managers and hopefully actions may then be taken to better conserve the Lesotho highlands for future generations.

Graduation date: 1999

Mémoire (M.Ress.Renouv.)-- Université du Québec à Chicoutimi, 1991. / Bibliogr.: f. 58-63. Document électronique également accessible en format PDF. CaQCU

Background : The recorded history of veld burning in the Kruger National Park (KNP) started with the appointment of Colonel James Stevenson-Hamilton as warden of the Park (then the Sabie Game Reserve) in July 1912 and can be divided into five periods: From 1912 to 1926, a haphazard, and indecisive burning policy was practiced, mainly due to the perception that fire was unfavourable for the environment and because the means to combat veld fires were very meagre. From 1926 to 1948, in which period it was realized that fire was not only unavoidable over a large area such as the KNP, but also actually desirable, necessary and beneficial when applied with circumspection. During this period the capability to successfully introduce and apply a definite fire policy did not exist. From 1948 to 1956, prescribed burning was not practiced, but a network of graded firebreaks was being established (to create burning blocks), and wild fires were actively combated. From 1957 to 1993, during which period a definite prescribed burning policy was practiced, amended several times, but basically consisting of a triennial rotational system where blocks were burned by management. All fires of non-management ignition sources were combated. From 1993 to the present, when a policy of allowing lightning-ignited fires to burn freely was introduced, and fires of human origin were suppressed. The shift away from a rigid prescribed burning programme was because of the concern that the dominance of grass species characteristic of over utilised veld was a result of too frequent burning (Potgieter, 2001). Lightning fires probably played just as an important role in shaping African savanna in pre-industrial times as anthropogenic fires caused by preindustrial man. The role of post-industrial man as far as its influence on the creation of savanna is concerned is probably negligible, but significantly important in the role of maintaining savanna, although probably not more so than that of lighting fires. Fires caused by postindustrial man becomes suspect as far as the creation of savanna is concerned, because instead of the mere burning of the veld for the pure reasons of survival as practiced by pre-industrial man, a measure of commercialism crept in (Potgieter, 2001). Fire management of the KNP in pre-industrial times can be regarded in the same light as that of post-industrial times. Although the motive for burning the veld in the KNP was beyond reproach, the underlying reasoning was not. Managers’ thinking was geared towards preventing so called “devastating fires”, laying to waste large areas of the Park, not realising that this was in actual fact nature going about its business in this ecosystem. They therefore devised a system of firebreak roads, which was gradually extended to the extent that we now have more than 4000 km roads that must be maintained. This was all in the cause of preventing or managing lightning and arson fires. Given the above, a revision of the veld fire policy was extremely necessary. The mission statement hammered out during the revising process in 1993 underscored and supported the proposal put forward in 1992, that lightning fires should be recognised as a legitimate and completely natural phenomenon in the Lowveld ecosystem. This had to be weighed against the prevailing practice of combating all fires caused by lightning and non-management anthropogenic sources of fire. The essence of this policy would therefore be to allow lightning-fires to burn to their full extent i.e. if vegetation conditions (available biomass) are such that large areas will burn, then such burns will be permitted to proceed to their full extent with the provision that no more than 50% of the management unit will be allowed to burn out (no matter what the ignition source) in a specific fire season (Potgieter, 2001).

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.