Fire occurrences in the Everglades have increased since hydrologic alterations began, yet the vulnerability of Everglades peat to combustion during wildfires has yet to be determined. Natural fire regimes help maintain ecosystem functions and services and disruptions of natural disturbance regimes can have detrimental impacts, jeopardizing ecosystem health. Severe peat combustion can destroy native vegetation, alter microtopography, and release large amounts of stored carbon into the atmosphere. To create a better understanding of the mechanistic controls on Everglades ground fires, the soil's physical properties within several sites of Water Conservation Area 3 and how changes in water table affect these physical characteristics were determined. Areas disturbed by hydrologic alterations contain higher mineral content and therefore require lower water content to combust when compared to preserved regions. Changes in water tables have a significant effect on soil moisture and lower water tables drastically increase the vulnerability of a region. / by James Johnson. / Thesis (M.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

by Yau Mei-sze. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 130-141). / Abstract --- p.i / Acknowledgements --- p.iii / List of Tables --- p.iv / List of Figures --- p.v / Chapter CHAPTER 1 --- INTRODUCTION / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Fire as an ecological factor in Hong Kong --- p.3 / Chapter 1.3 --- Conceptual framework of the study --- p.6 / Chapter 1.4 --- Objectives of the study --- p.10 / Chapter 1.5 --- Significance of the study --- p.12 / Chapter 1.6 --- Organization of the thesis --- p.12 / Chapter CHAPTER 2 --- STUDY AREA / Chapter 2.1 --- Location --- p.14 / Chapter 2.2 --- Climate --- p.16 / Chapter 2.3 --- Geology --- p.18 / Chapter 2.4 --- Soil --- p.19 / Chapter 2.5 --- Vegetation --- p.20 / Chapter CHAPTER 3 --- EFFECTS OF HILL FIRE ON SOIL CHEMICAL PROPERTIES / Chapter 3.1 --- Introduction --- p.21 / Chapter 3.2 --- Methodology --- p.26 / Chapter 3.2.1 --- Sampling --- p.26 / Chapter 3.2.2 --- Soil reaction --- p.27 / Chapter 3.2.3 --- Total Kjeldahl nitrogen (TKN) --- p.27 / Chapter 3.2.4 --- Mineral nitrogen (ammonium and nitrate nitrogen) --- p.27 / Chapter 3.2.5 --- Total phosphorus --- p.28 / Chapter 3.2.6 --- Available phosphorus --- p.28 / Chapter 3.2.7 --- "Exchangeable K, Na, Ca and Mg" --- p.28 / Chapter 3.2.8 --- Exchangeable A1 and H --- p.29 / Chapter 3.2.9 --- Organic carbon --- p.30 / Chapter 3.2.10 --- Carbon : nitrogen ratio --- p.30 / Chapter 3.3 --- Statistical analysis --- p.30 / Chapter 3.4 --- Results --- p.31 / Chapter 3.4.1 --- Effects of fire on soil chemical properties --- p.31 / Chapter 3.4.1.1 --- Soil acidity --- p.31 / Chapter 3.4.1.2 --- Nutrient cations --- p.32 / Chapter 3.4.1.3 --- Total Kjeldahl nitrogen and mineral N --- p.33 / Chapter 3.4.1.4 --- Soil organic matter and C:N ratio --- p.33 / Chapter 3.4.1.5 --- Total and available phosphorus --- p.33 / Chapter 3.4.2 --- Seasonal changes of soil chemical properties after fire --- p.34 / Chapter 3.4.2.1 --- Soil pH and exchangeable acidity --- p.34 / Chapter 3.4.2.2 --- Nutrient cations --- p.35 / Chapter 3.4.2.3 --- Total Kjeldahl nitrogen and mineral N --- p.36 / Chapter 3.4.2.4 --- Soil organic matter --- p.37 / Chapter 3.4.2.5 --- Total and available phosphorus --- p.38 / Chapter 3.5 --- Discussion --- p.38 / Chapter 3.5.1 --- Effects of fire on soil chemical properties --- p.38 / Chapter 3.5.1.1 --- Immediate effects of fire on soil acidity --- p.38 / Chapter 3.5.1.2 --- "Immediate effects of fire on organic matter, N and P" --- p.40 / Chapter 3.5.1.3 --- Immediate effects of fire on cation nutrients --- p.41 / Chapter 3.5.2 --- Seasonal changes of soil chemical properties after fire --- p.42 / Chapter 3.5.2.1 --- Seasonal changes of soil acidity after fire --- p.42 / Chapter 3.5.2.2 --- Seasonal changes of nutrients after fire --- p.43 / Chapter 3.5.3 --- Overall fertility of the fire-affected soil --- p.44 / Chapter 3.6 --- Conclusion --- p.46 / Chapter CHAPTER 4 --- NITROGEN MINERALIZATION AFTER FIRE / Chapter 4.1 --- Introduction --- p.48 / Chapter 4.2 --- Methodology --- p.52 / Chapter 4.2.1 --- In situ incubation --- p.52 / Chapter 4.2.2 --- "Determination of N mineralization, leaching and uptake" --- p.53 / Chapter 4.3 --- Statistical analysis --- p.55 / Chapter 4.4 --- Results --- p.56 / Chapter 4.4.1 --- Seasonal variations of nh4-N and no3-N --- p.56 / Chapter 4.4.2 --- "Net ammonification, leaching and uptake" --- p.57 / Chapter 4.4.3 --- "Net nitrification, leaching and uptake" --- p.58 / Chapter 4.5 --- Discussion --- p.59 / Chapter 4.5.1 --- Post-fire ammonification --- p.59 / Chapter 4.5.2 --- Post-fire nitrification --- p.62 / Chapter 4.5.3 --- Net nitrogen mineralization of the burnt soil --- p.65 / Chapter 4.6 --- Conclusion --- p.68 / Chapter CHAPTER 5 --- EFFECTS OF LIME AND PHOSPHORUS ON THE MINERALIZATION OF NEW BURNT SOIL / Chapter 5.1 --- Introduction --- p.70 / Chapter 5.2 --- Methodology --- p.73 / Chapter 5.2.1 --- Sampling of soil --- p.73 / Chapter 5.2.2 --- Lime treatment --- p.73 / Chapter 5.2.3 --- Phosphorus treatment --- p.74 / Chapter 5.2.4 --- Combined lime and phosphate treatment --- p.74 / Chapter 5.3 --- Statistical analysis --- p.75 / Chapter 5.4 --- Results --- p.75 / Chapter 5.4.1 --- Chemical properties of the unamended soil --- p.75 / Chapter 5.4.2 --- Lime treatment --- p.76 / Chapter 5.4.2.1 --- Effect of lime on nh4-N production --- p.76 / Chapter 5.4.2.2 --- Effect of lime on no3-N production --- p.78 / Chapter 5.4.2.3 --- Effect of lime on PO4 production --- p.78 / Chapter 5.4.2.4 --- Effect of lime on exchangeable A1 --- p.78 / Chapter 5.4.3 --- Phosphorus treatment --- p.79 / Chapter 5.4.3.1 --- Effect of phosphorus on NH4-N production --- p.79 / Chapter 5.4.3.2 --- Effect of phosphorus on NO3-N production --- p.80 / Chapter 5.4.3.3 --- Effect of phosphorus on PO4 production --- p.80 / Chapter 5.4.4 --- Combined lime x P amendment and mineralization of N and P --- p.81 / Chapter 5.4.4.1 --- Effect of lime x P on nh4-N production --- p.81 / Chapter 5.4.4.2 --- Effect of lime x P on NO3-N production --- p.83 / Chapter 5.4.4.3 --- Effect of lime x P on po4 production --- p.83 / Chapter 5.5 --- Discussion --- p.83 / Chapter 5.5.1 --- Effect of soil acidity on ammonification --- p.83 / Chapter 5.5.2 --- Effect of soil acidity on nitrification --- p.88 / Chapter 5.5.3 --- Effect of lime on the mineralization of P --- p.89 / Chapter 5.5.4 --- Effect of combined lime x P on the mineralization of N and P --- p.89 / Chapter 5.6 --- Conclusion --- p.90 / Chapter CHAPTER 6 --- VEGETATION REGENERATION AND NUTRIENT COMPOSITION AFTER FIRE / Chapter 6.1 --- Introduction --- p.92 / Chapter 6.2 --- Methodology --- p.96 / Chapter 6.2.1 --- Vegetation regeneration analysis --- p.96 / Chapter 6.2.2 --- Chemical analysis --- p.96 / Chapter 6.3 --- Results --- p.97 / Chapter 6.3.1 --- Vegetation regeneration --- p.97 / Chapter 6.3.2 --- Nutrient composition of regenerated species --- p.100 / Chapter 6.3.2.1 --- Total Kjeldahl nitrogen --- p.100 / Chapter 6.3.2.2 --- Total phosphorus --- p.101 / Chapter 6.3.2.3 --- Potassium --- p.102 / Chapter 6.3.2.4 --- Calcium --- p.103 / Chapter 6.3.2.5 --- Magnesium --- p.104 / Chapter 6.3.2.6 --- Sodium --- p.105 / Chapter 6.4 --- Discussion --- p.106 / Chapter 6.4.1 --- Vegetation regeneration after fire --- p.106 / Chapter 6.4.2 --- Nutrient composition of regenerated species --- p.108 / Chapter 6.4.3 --- Recovery and erosion control --- p.112 / Chapter 6.5 --- Conclusion --- p.112 / Chapter CHAPTER 7 --- CONCLUSION / Chapter 7.1 --- Summary of findings --- p.114 / Chapter 7.2 --- Implications of the study --- p.118 / Chapter 7.2.1 --- Is hill fire hazardous or beneficial to the local environment? --- p.118 / Chapter 7.2.2 --- Mechanisms to conserve nutrients in a fire-prone environment --- p.121 / Chapter 7.2.3 --- Natural regeneration or reforestation? --- p.122 / Chapter 7.3 --- Limitations of the study --- p.123 / Chapter 7.4 --- Suggestion for future study --- p.126 / REFERENCES --- p.130

The majority of the vegetation types occurring on Malilangwe Estate, in the south-eastern lowveld of Zimbabwe, are dominated by Colophospermum mopane (mopane). Over the past 30-50 years the stand density of these mopane vegetation types has increased, and an investigation was undertaken to determine the effect of season of burning and type of fire on mopane woodlands. From this study the following was ascertained: 1) A single predictive equation cannot be used over all seasons to estimate standing crop (fuel load) using the standard disc pasture meter procedure. The calibration equations developed using this procedure accounted for between 39 and 72% of the variation in standing crop, illustrating the high variation in basal cover of the grass sward, as well as the variation between months. Although the revised procedure, developed for areas with low basal cover, accounts for a lot more of the variation in standing crop, this procedure was not used to estimate standing crop over the study period because the calibration equation covered a number of vegetation types, and was not specific to the mopane woodlands. 2) Standing crop tracks effective rainfall (monthly rainfall divided by monthly pan evaporation) closely, with a lag period of less than one month. Standing crop can be estimated using a predictive equation that utilizes effective rainfall from the previous month. There is a positive relationship between peak standing crop and rainfall. A predictive equation was developed to estimate peak standing crop, using annual rainfall. Standing crop declines through the dry season as effective rainfall decreases, and this 'decrease function' allows for the estimation of the standing crop for a particular month, after peak standing crop is reached. 3) Two leaf quantification equations were developed for mopane trees in the south-eastern lowveld of Zimbabwe, one for coppicing and for non-coppicing individuals. These allow for the estimation of leaf dry mass from measured canopy volume. 4) There was no significant difference between the fire intensities attained for the three seasons of burning. Over all seasons, head fires were significantly more intense than back fires. 5) Percentage topkill after late dry season burns was significantly higher than topkill after early dry season burns. There was no significant difference between mid and late dry season burns, and head fires led to significantly more topkill than back fires. Plants < 150 cm experienced significantly more topkill (80 %) than did individuals > 150 cm (44%). 6) Fire per se led to an increase in stand density over all seasons and types of fire, but this change was not significant. Fire did not influence the nett recruitment of new individuals. Height class one (0-50 cm) and three (151-350 cm) were impacted most by fire. This reflects a change in tree structure, with an increase in the amount of leaf material in height class three, and a subsequent decrease in the amount of material in height class one. 7) The effect of season of burning on the change in tree height was significant, whereas the effect of type of fire was not significant. All treatments, except early dry season back fires, led to a reduction in tree height, whereas trees in the no burn areas increased in height. 8) Burning in any season, and implementing either type of fire, led to an increase in the number of stems. Mid dry season burns led to the highest increase in number of stems. However, the more intense the fire the smaller the increase in number of stems. 9) All three seasons of burning (head and back fires) led to a significant decrease in maximum canopy diameter per tree, while the maximum canopy diameter of trees in the no burn areas increased. Mid dry season burns resulted in the greatest decrease in canopy diameter. 10) The effect of burning on the change in leaf dry mass per tree was highly significant. All three seasons of burning led to a decrease in leaf dry mass, while there was no difference between head and back fires. Leaf dry mass in the control areas increased however. High fire intensities led to the greatest decrease in leaf dry mass, late dry season head fires having the greatest decrease. This study suggests that mopane plants face a constraint due to fire and/or browsing, and a tradeoff occurs between canopy volume, canopy diameter, canopy area; and number of stems. Fire leads to an increase in the number of stems through coppicing, while canopy volume and leaf dry mass decreases. This decrease is either (i) a tradeoff in response to increasing stem number, or (ii) a reduction in canopy because additional leaves on the new stems contribute to photosynthesis. The most important response to season of burning is the altered phenophase (phenological stage) of the plant. Early dry season burns cause the trees to be leafless during the early dry season (when unburnt trees are carrying full leaf), and then to be in leaf at the end of the dry season (when unburnt trees are leafless). It would appear that fire disturbance initiates leaf senescence after burning, and then leaf expansion earlier than normal i.e the whole leaf senescence/growth process is brought forward. Trees in late dry season burn areas remain leafless at the start of the rains, while trees in unburnt areas are carrying leaf. Being leafless these trees do not photosynthesize during this time, and it is proposed that the grass sward is advantaged by the reduced competition from the tree component. The consequences of these two changes in phenophase could not be addressed in this study, but are pertinent questions that must be answered if mopane woodland dynamics are to be more fully understood. Management recommendations for (1) the removal of unacceptable moribund grass material, or (2) the reduction of encroachment by woody species on Malilangwe Estate are also given. In an attempt to combat the increase in stand density of mopane it is recommended that high intensity head fires be implemented, when standing crop (fuel load) is sufficient and climatic conditions are conducive to maintaining high intensity fires. These should be carried out at the end of the dry season, before the onset of the rains. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

Thesis (M.S.)--Oregon State University, 1997. / Typescript (photocopy). Includes bibliographical references (leaves 158-167). Also available on the World Wide Web.

Thesis (M.S.)--Brigham Young University. Dept. of Chemical Engineering, 2005. / Includes bibliographical references (leaves 89-95).

Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 79-86). Also available on the World Wide Web.

Twenty Douglas-fir plantations, ranging from 5 to 15 years old, were examined on the east side of Vancouver Island. In all areas studied, salal was the dominant ground cover, and was suspected of being a major competitor with trees for water and nutrients. In each plantation, part of the area has been burned and part was unburned. Stocking of planted Douglas-firs was found to be greater on the burned than on the unburned areas of 16 sites and height growth of planted Douglas-firs was greater on the burned than on the unburned areas of 18 sites. Some degree of nitrogen deficiency was inferred for 17 sites, but was not attributed to burning. Height and percent cover of salal was greater on unburned areas. Differences in height growth and percent cover of salal between burned and unburned areas were seen to be greatest where inferred burn severity was high. Browsing of Douglas-fir was more prevalent on burned areas but did not result in height growth being less than on adjacent unburned areas. / Forestry, Faculty of / Graduate

Large wildfires in California cause significant socioecological impacts, and half of the federal funds for fire suppression are spent each year in California. Future fire activity is projected to increase with climate change, but predictions are uncertain because humans can modulate or even override climatic effects on fire activity. Here we test the hypothesis that changes in socioecological systems from the Native American to the current period drove shifts in fire activity and modulated fire-climate relationships in the Sierra Nevada. We developed a 415-y record (1600-2015 CE) of fire activity by merging a treering-based record of Sierra Nevada fire history with a 20th-century record based on annual area burned. Large shifts in the fire record corresponded with socioecological change, and not climate change, and socioecological conditions amplified and buffered fire response to climate. Fire activity was highest and fire-climate relationships were strongest after Native American depopulation-following mission establishment (ca. 1775 CE)-reduced the self-limiting effect of Native American burns on fire spread. With the Gold Rush and EuroAmerican settlement (ca. 1865 CE), fire activity declined, and the strong multidecadal relationship between temperature and fire decayed and then disappeared after implementation of fire suppression (ca. 1904 CE). The amplification and buffering of fire-climate relationships by humans underscores the need for parameterizing thresholds of human-vs. climate-driven fire activity to improve the skill and value of fire-climate models for addressing the increasing fire risk in California.

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.

Thesis presented for the Degree of Doctor of Philosophy at the University of the Witwatersrand / Successional changes in the vegetation after fire were studied in several fynbos communities of the south-western Cape Province of South Africa. The study sites were located in the mountains, at altitudes between 300 and 1000 m a.s.l., in areas with winter rainfall regimes -1 and annual precipitation of about 900 to 1000 mm. yr Soils are highly leached, derived principally from quartzites. The two main sites were Zachariashoek near Paarl, where summers tend to be rather dry, and Jakkalsrivier east of Grabouw, where summer drought is ameliorated by fog precipitation and cloudiness. Successional changes were followed for intervals of up to 10 yr between fires, as well as for similar periods in vegetation that had been unburnt for 25 yr. Vegetational changes were analysed by means of repeated floristic assessments on permanent quadrats and point-quadrat sampling of canopy cover composition on these and on larger plots. At Jakkalsrivier, recently burnt and long unburnt vegetation were also compared by paired samples. Demographic trends in populations of prominent shrub species were followed by repeated censuses of tagged samples in unburnt and recently burnt vegetation. Also at Jakkalsrivier, the effects of fire on resources available to plants were examined by sampling soil moisture and soil mineral nutrients, as well as by following trends in xylem pressure potentials in selected species of plants and analysing their foliar nutrient concentrations. Effects of fire on microclimate were tested by comparative studies on burnt and unburnt sites. All fynbos communities sampled proved to be highly stable in the face of fire. Essentially, the pre-fire species composition was regained in 2-3 yr in every case. Species were added after fire, partly because of the appearance of ephemerals with life histories tied to fire, but also because of the reappearance of longer-lived plants as well as through the readier detection of species in vigorous vegetative form. The species richness of the regenerating corrununities tended to be quadratically related to pre-fire biomass, as predicted from current succession theory. Most species in any corrununity (about 70% on average) regenerated vegetatively by sprouting after fire. The relative numbers of species that regenerated germinatively, i.e. the seeders, did not vary in a manner predictively related to corrununity biomass. There were relatively few species with specialised life histories based on reseeding, such as those with canopy-stored seed and ephemerals with presumably specialised requirements for germination. Virtually no recruitment could be found among plants in the older (about 25 yr) vegetation, in contrast with lowland fynbos sites, where recruitment of herbaceous species occurs, and some mountain fynbos sites on more fertile soils, where forest precursors may sometimes colonise. Canopy redevelopment after fire indicated similar resilience among the different corrununities, despite variation in regrowth rates. Pre-fire growth-form composition was restored within around 10 yr. Maximum leaf-area indices ranged from about 1,5 to 2,5, although corrununi ties on phreatic sites had leaf-area indices exceeding 3,0. There was no evidence for a suppression of the understoreys by overstorey layers, mainly because the latter were sparse despite the abundance of tall broad-sclerophyllous shrubs in certain habitats. This was because the taller shrubs had sparse or slender crowns, or both, and because mortality tended to thin the populations before dense canopies developed. Trends in the composition of the canopy varied among corrununities. corrununities in productive habitats, i.e. in this case on phreatic sites, were dominated in the early stages by a relatively luxurious growth of ephemeral herbs and soft shrubs which declined within around 3-4 yr. Other sites had very sparse ephemeral cover, the early stages being dominated mainly by Restionaceae, Cyperaceae, and other sprouting herbs, and sprouting and seeding shrubs, which were constituents of the pre-fire canopies. In this respect, the fynbos is clearly distinguished from the California chaparral, for example, where ephemerals tend to dominate the post-fire stages on most sites. There was no evidence that fire had any effect on the water relations of regenerating vegetation, although stream discharge is known to be increased by fire in these environments. There was tentative evidence, in enhanced foliar concentrations of some mineral nutrients, that regenerating species of climax plants exploited nutrients released in fire. However, any such responses were small, especially in comparsion with responses observed in chaparral, for example. Ephemeral shrubs had much higher concentrations of foliar nutrients overall than climax species, tending to confirm the correlations found in Australian heathlands between plant life-history and nutrient economy. The effects of fire on microclimate were pronounced, especially on the thermal and water vapour regimes experienced by seedlings and sprouts. These extremes did not, however, appear as water stress in regenerating plants. Despite relatively sparse canopies, mature vegetation did reduce light at the ground to levels likely to affect seedling recruitment and survival. Preliminary experiments with a local dominant shrub, Leucadendron xanthoconus, showed a pronounced intolerance of shading and hence that light attenuation by canopies must be implicated in successional processes. The demographic studies indicated that density-dependent effects were not important in survival of plants. Two species of fire ephemeral shrubs effectively died out within four years, being characterised by markedly higher growth rates than climax species and brief and early fecundities. Climax shrubs had more or less constant rates of mortality over time, though populations in unburnt vegetation tended to have slightly higher rates of mortality than young populations. Densities of seedling populations were very high, but mortality rates were extremely low. In summary, it may be said that the fynbos communi ties studied here are very stable under a given fire regime. Recovery is rather rapid, being apparently achieved within 10 yr. Not much change occurs in older vegetation, but there was a gradual attrition of populations of dominant shrubs, without recruitment, with rare exceptions. Summer droughts in these montane environments are evidently not sufficiently marked for water deficits to play a primary role in succession, so that fire has no effect on plant water relations. Nutrient responses are relatively weak, and masked in the plants by the low rates of metabolism in climax species. Succession after fire is distinguished by the recovery of pre-fire communities, and subsequent inhibition of recruitment. This inhibition is probably through the effects of canopies on microclimate, although the interactions between especially plants and animals have been implicated in succession in other studies. / AC2017