Over the past century, woody plants and shrubs have increased in abundance at the expense of grasslands in many semiarid regions. The availability and concentrations of nutrients influence the relative success of plants, but the effects of fire frequency on soil nutrients is unknown for semiarid grasslands. On the gunnery ranges of Fort Huachuca in southeastern Arizona, study sites were established to examine the effects of fire frequency on soil biogeochemistry, plant biochemistry, and δ¹³C values in soil organic matter (SOM). The sites were on homogeneous granitic alluvium where wildfire frequency history is known from 1973 to present and no cattle grazing has occurred in recent decades. Subplots represent fire frequencies of no burns, 3 fires per decade, and 5 fires per decade. The "no burn" plot has abundant C₃ Prosopis veleruina (mesquite) trees, whereas the burned plots are open C₄-dominated grasslands with scattered mesquite trees. Prosopis trees have altered SOM pools by the concentration of plant nutrients and the addition of isotopically light shrub litter. Frequent fires have altered the basic geochemistry and nutrient availabilities of the soil, and the changes appear to be significant enough to affect plant growth. Soil pH increases with burning frequency, and TOC, total nitrogen, and plant -available phosphorus show significant increases on the infrequently burned plot. Burning is advantageous for preservation or restoration of grasslands, as total living grass biomass is greater on the two burned plots. Root biomass is significantly lower on the "frequently burned" plot. Concentrations of the key nutrients nitrogen and phosphorus are reduced in plants on the burned sites compared to plants on the unburned site. Fires help re-distribute nutrients but evidence of nutrient concentrations and δ¹³C values are retained in SOM for many decades. Estimates of bulk carbon turnover rates range from 112 to 504 years. Evidence for modern C₃ shrub expansion is found in the shift of SOM δ¹³C values from values characteristic of C₄ grasses to C₃ shrubs in surface soil layers. δ¹³C(SOM) values indicate that the Holocene and Late Pleistocene were dominated by C₄ grasslands, and the pre-Late Pleistocene vegetation was a C₄-grass savanna with abundant C₃ plants.

The KwaZulu-Natal Drakensberg, South Africa, is predominantly a grassland ecosystem maintained by fire. The effect of the current burning regime on invertebrate and flowering forb diversity in this ecosystem is poorly understood. The overall aim ofthis study was to contribute towards the development of an effective burning regime for the KwaZulu-Natal Drakensberg that will conserve invertebrates and indigenous forbs, two major components of biodiversity. The objectives were to examine the effect of fire and fire frequency on flowering forb and invertebrate species diversity, to determine whether fire frequency, time since last burn or locality were influencing species composition, and to identify potential biodiversity indicators that reflect overall species richness for use in monitoring of invertebrates and forbs. Sampling took place in March, September and November of 2002 at Giants Castle Game Reserve. Invertebrates were sampled using sweep netting and targeted netting along transects, yellow pan traps and soil quadrats. Invertebrate taxa sampled were ants (Formicidae), butterflies (Lepidoptera), grasshoppers (Orthoptera), leafboppers (Cicadellidae), bees (Apoidea), bee flies (Bombyliidae), hover flies (Syrphidae), robber flies (Asilidae), spiders (Araneae), earthworms (Oligochaeta) and millipedes (Diploda). These were identified to species level with the assistance of taxon experts. Flowering forbs were sampled using five replicates of five by five metre quadrats randomly placed in each site. Overall flowering forb and invertebrate species diversity was higher in grasslands that were burnt for two consecutive years in 2001 and 2002 than in grasslands that were not burnt during those two years. Frequently (annual) and intermediately (biennial) burnt grasslands had significantly higher invertebrate and flowering forb diversity than infrequently (five years without burning) burnt grasslands. This, together with the fact that grasslands burnt during the year of sampling had higher species richness than grasslands burnt two and five years previously suggests that invertebrates and forbs are generally resilient to fire and many forb species appear to be stimulated by fire. However, each burn frequency had its own suite of unique flowering forb and invertebrate species. Invertebrate communities were influenced mostly by locality and the length of time past since the last fire and flowering forb communities were influenced mostly by the length oftime past since the last fire. Fire frequency had the least influence on both invertebrate and forb communities. Ecological succession occurred after each fire in the invertebrate communities but forb communities appear to need more than five years without fire for ecological succession to occur. The findings of this study therefore suggest that using a combination of three fire frequencies would result in patches of grassland in various stages of ecological succession, and would conserve species unique to each burning frequency, and would therefore conserve maximum diversity. Flowering forb species richness and certain invertebrate taxa (ants, leafboppers, spiders and bees) have the potential to act as indicators of overall invertebrate species richness for use in monitoring programmes. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

Biotopes associated with railway corridor in valley of the river Tichá Orlice (Eastern Bohemia, Czech Republic) ABSTRACT Expansion, invasion or decline of plant species caused by environmental changes belong to the most important phenomenons associated with vegetation cover development. In spite of their often initiation by human activities the above mentioned processes continue then spontaneously and uncontrollably. This study is concentrated to the effect of these mechanisms on the biotope structure along the Tichá Orlice River (Eastern Bohemia, Czech Republic) - in its lowland landscape segment of the canyon character where the second axis of the valley (river flow is the first one) is created by railway line more than 150 years of local history. The case study has the general aim: to treat the present and/or future impact of described trends to plant biota and the degree of its influencing. My diploma thesis investigates functional impact and mutual interaction of the two main migration pathways of exotic species - the T.Orlice river and the railway corridor. It presents qualitative and quantitative changes in plant components of local (semi)natural biotopes by mean of interrelationships among selected ecological groups of species (neophytes, expansive species, and ephemeroids). At the same time, this...

Les changements globaux, notamment les changements d'usage des terres, modifient profondément le fonctionnement des écosystèmes et la biodiversité et, ont déjà impacté de nombreux services écosystémiques. La disparition de ces écosystèmes souligne la nécessité de préserver les zones intactes, et la restauration des zones détruites ou perturbées peut permettre de venir en appui aux efforts de conservation et minimiser les dommages. Ce travail a pour objet d’étude les campos rupestres, des pelouses néotropicales d’altitude, faisant partie du Cerrado (savane brésilienne), qui recèlent une importante biodiversité et qui, comme bien d'autres écosystèmes de montagne, fournissent de précieux services écosystémiques tels que la filtration de l’eau. Ils ont été, et sont encore, grandement affectés par les activités humaines (les travaux de génie civil, les carrières ou les mines). Le premier objectif de cette thèse était de décrire l'écosystème de référence, afin de définir clairement un objectif de restauration et mesurer les progrès et le succès de la restauration. Nous avons montré que les campos rupestres sont composés d'au moins deux communautés végétales distinctes (une avec un substrat caillouteux et l’autre avec un substrat sableux), chacune ayant une composition en espèces et une structure particulières ainsi qu’une grande biodiversité. La phénologie reproductive varie au sein des communautés herbacées: la majorité des espèces fleurissent et fructifient pendant la saison des pluies, d'autres se reproduisent en revanche durant la saison sèche. Tout au long de nos 2 années de suivis phénologiques, certaines espèces dominantes, notamment des Poaceae, n'ont pas été observées en fleur impliquant une dispersion limitée de ces espèces vers les zones dégradées. Les communautés végétales de campos rupestres ne sont pas résilientes aux fortes perturbations: plusieurs années après, presque aucune des espèces cibles n’ont été trouvées en zones dégradées, les sols ont complètement été modifiés et les banques de graines ne se sont recomposées qu’avec des espèces rudérales non désirées. Selon le modèle des filtres, une communauté résulte d’un pool régional d’espèce sélectionné par un ensemble de filtres : de dispersion, abiotique et biotique. Les interventions de restauration mises en place avaient pour but d’agir sur ces différents filtres afin de diriger la dynamique des communautés végétales. Nous avons mis en place trois protocoles de restauration in-situ (le transfert de foin, la translocation d’espèce et la translocation de plaque de végétation) pour restaurer les deux types de communautés de campos rupestres identifiées. Le transfert de foin n’a pas permis la restauration des communautés végétales de campos rupestres en raison de l’importante altération des sols et, surtout, à cause de la mauvaise qualité des graines. En effet, nos études de germination ont montré que, alors que certaines espèces de Xyridaceae et Velloziaceae germent très bien, certaines espèces dominantes de Poaceae, de Cyperaceae ou d’Asteraceae ont des graines soit vides, soit non viables, soit dormantes ; le semis se révèle alors peu efficace. Nous n’avons pas mis en évidence d’effet positif du feu sur la germination des espèces de campos rupestres. La translocation d'espèces s’avère un succès pour une seule espèce, Paspalum erianthum. Pour les autres, les dommages causés au niveau des racines lors de la translocation limitent probablement leur survie. Enfin la translocation de plaques de végétation s’avère être la méthode la plus efficace permettant à de nombreuses espèces d’être réintroduites en zones dégradées. En raison de la faible résilience des campos rupestres dans lesquels les plaques de végétation ont été prélevées, cette méthode ne peut être envisagée que pour sauver des habitats dans le cas extrême où leur destruction est inévitable. Face à la difficulté de restaurer les campos rupestres, leur protection et leur conservation doit être une priorité / Global environmental changes, especially land-use changes, have profound effects on both ecosystem functioning and biodiversity, having already altered many ecosystem services. These losses emphasize the need to preserve what remains; however when conservation programs are not sufficient, restoring areas that have been destroyed or disturbed can improve conservation efforts and mitigate damages. This work focuses on campos rupestres, Neotropical grasslands found at altitudes, which are part of the Cerrado (Brazilian savannas). They host a great biodiversity with a high level of endemism and, like other mountain ecosystems, provide valuable ecosystem services, such as water purification and recreational services. They have been and still are being impacted by human activities, such as civil engineering construction, quarrying or mining. The first objective of this thesis was to describe the reference ecosystem in order to aim for a clear restoration target and to monitor progress and success. We show that campos rupestres are composed of at least two distinct plant communities (i.e. sandy and stony grasslands), each having a specific composition and structure, hosting a great biodiversity. Several phenological patterns occur among the herbaceous communities: the majority of species flowers and fruits appear during the rainy season but other patterns can be observed. During our 2-year survey, some dominant species belonging to Poaceae, among others, were not observed reproducing, which implies limited chances to disperse on degraded areas. Campo rupestre vegetation is not resilient following a strong disturbance: several years after the disturbance, almost no native species are encountered on the degraded areas, soils are completely altered and seed bank recomposes only with non-target ruderal species. According to the filter model, a local community is a subset of the regional species pool determined by a set of dispersal, abiotic and biotic filters. Acting on the different filters to influence the plant community was the core of our restoration interventions. We then applied three in-situ restoration protocols (hay transfer, species translocation and turf translocation) to restore both kinds of grassland. Hay transfer does not allow the restoration of campo rupestre vegetation because of soil alteration and mainly because of poor seed quality. Indeed, germination studies show that, while some Xyridaceae and Velloziaceae have a high germinability, some dominant Poaceae, Cyperaceae or Asteraceae species have embryoless, unviable or dormant seeds, which makes seeding less efficient. There is no evidence that fire-related cues enhance germination in campos rupestres. Species translocation is successful for only one species, Paspalum erianthum; for the others, root damages probably impede survival. Finally, turf translocation is the most successful method, since numerous species are re-introduced on degraded areas. However due to the low resilience of pristine campos rupestres where turfs are taken from, turf translocation can only be considered in the case of habitat rescue, in circumstances when complete habitat destruction is otherwise unavoidable. Face to the difficulty to restore these peculiar grasslands, the protection and the conservation of campos rupestres must be made a high priority

From the Proceedings of the 1976 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 29-May 1, 1976, Tucson, Arizona / The general hydrologic characteristics, selected climatic factors, and soil properties of the high-elevation grasslands are compared to the surrounding forest. Evidence shows that water yield could be increased by 1-1/2 to 2 inches if snow could be held where it falls. It may be possible to establish tree windbreaks in the grassland by altering the microclimate during establishment, and introducing mycorrhiza with the planted seedlings. This conclusion is supported by good survival in a 2-year planting trial.

From the Proceedings of the 1977 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 15-16, 1977, Las Vegas, Nevada / Increased nutritional and economic demands for agricultural products have dictated the need for greater and more efficient use of western grass forage. Vegetation manipulation is the quickest and most economical means of increasing forage. However , the hydrologic effects must be taken into consideration before embarking on a large scale vegetation manipulated program. This study discusses the hydrologic and erosion changes measured from a 110-acre semiarid watershed which was converted from brush to grass by root plowing and seeding. Significant changes were observed in rainfall-runoff relationships as average summer runoff was considerably in excess of predictions. Sediment yield also varied, and both of these results were tied to the change in vegetative cover and post conversion rainfall conditions.

Hlogoma Mountain is a small inselberg surrounded by farms and commercial forestry in the Underberg district (KwaZulu-Natal) within the Gs10 Drakensberg Foothill Moist Grassland. As little is known about the vegetation on Hlogoma, a survey was undertaken to classify, map and describe the plant communities occurring on the inselberg. A total of 100 (16 m2) randomly stratified sample plots were placed in homogeneous vegetation units within the 117 ha study area. A TWINSPAN classification, refined by Braun-Blanquet procedures, resulted in the identification of two major communities, five communities, 12 sub-communities and four variants. All communities were described and a vegetation map constructed. Ordinations identified key environmental variables that have an impact on the vegetation at the study site. A plant species checklist was created and analysed for floristic composition; rarity and threatened species; medicinal plants; endemism; phenology; flower colour and elevation range; species richness and plant community biodiversity. A total of 467 species were identified, represented by 271 genera and 87 families. Four Red Data species and a new Aspidoglossum species were discovered. Two near-endemic genera, two endemic species and 88 near-endemic species belonging to the Drakensberg Alpine Centre were found on Hlogoma. This study showed that Hlogoma Mountain is an inselberg with high plant species richness and endemism, and is a refuge of conservation importance for biodiversity. / Environmental Sciences / M. Sc.(Environmental Science)

La germination et la croissance hétérotrophe sont des phases clés de l'établissement des plantes. Ils sont sous contrôle génétique et affectés par la température. L'objectif de cette thèse est d'analyser la variabilité inter et intra-spécifique de cinq espèces prairiales dans leurs réponses à la température pendant la germination et la croissance hétérotrophe. Trente-deux populations de Lolium perenne, Festuca arundinacea, Dactylis glomerata, Medicago sativa, et Onobrychis viciifolia ont été évalués sous huit températures constantes entre 5 et 40°C.La nouveauté de ce travail vient de la large gamme de températures et le nombre de populations évaluées. Il a été observé que, au sein des espèces, la réaction des populations à la température indique une forte variabilité et des différences significatives. La germination n'a été pas observée à 40°C pour l'une des 23 graminées, l'O. viciifolia germé peu tandis que les variétés de M. sativa ont été peu affectées. La croissance hétérotrophe des 32 populations a été affectée par la température. La croissance des axes fortement fiable ou nulle à 40°C. Les courbes de réponse du taux de croissance maximale de l'axe sont asymétriques en forme de cloche.Des interactions significatives entre la température et la population ont été détectées pour la germination et la croissance hétérotrophe. La germination des populations des sites froids est renforcée par des températures plus chaudes et limité par les plus froids et vice-versa pour les populations chaudes adaptées. / Germination and heterotrophic growth are key phases for plant establishment. They are under genetic control and affected by temperature. The objective of this thesis was to analyse the inter- and intra-specific variability of five pasture species in their responses to temperature during germination and heterotrophic growth.Thirty two populations of Lolium perenne, Festuca arundinacea, Dactylis glomerata, Medicago sativa, and Onobrychis viciifolia were evaluated under eight constant temperatures between 5 and 40°C.The novelty of this work comes from the wide range of temperatures and the number of populations evaluated. It was observed that, within species, the response of populations to temperature shows high variability and significant differences. No germination was observed at 40°C for any of the 23 grasses, O. viciifolia germinated poorly while M. sativa varieties were little affected. Heterotrophic growth of the 32 populations was affected by temperature. The growths of the axes were negligible or lethal at 40°C. Response curves of maximum growth rate of the axis were asymmetric bell-shaped.Significant interactions between temperature and population were detected for germination and heterotrophic growth. Germination of populations from cold sites is enhanced by warmer temperatures and limited by colder ones and vice versa for warm-adapted populations. This study demonstrates that genetic variability does exist within the five studied species. This variability could be exploited to breed new varieties adapted to the future climate.

Forest encroachment is understood to be the main reason for prairie grassland decline across the United States. In Texas and Oklahoma, juniper has been highlighted as particularly opportunistic. This study assesses the usefulness of three remote sensing techniques to aid in locating the areas of juniper encroachment for the LBJ Grasslands in Decatur, Texas. An object based classification was performed in eCognition and final accuracy assessments placed the overall accuracy at 94%, a significant improvement over traditional pixel based methods. Image biomass was estimated using normalized difference vegetation index (NDVI) for 1 meter resolution IKONOS winter images. A high correlation between the sum of NDVI for tree objects and field tree biomass was determined where R = 0.72, suggesting NDVI sum of a tree area is plausible. However, issues with NDVI saturation and regression produced unrealistically high biomass estimates for large NDVI. Canopy height model (CHM) derived from 3-5m LiDAR data did not perform as well. LiDAR typically used for digital elevation model (DEM) production was acquired for the CHM and produced correlations of R = 0.26. This suggests an inability for this particular dataset to identify juniper trees. When points that registered a tree height where correlated with field values, an R = 0.5 was found, suggesting denser point spacing would be necessary for this type of LiDAR data. Further refining of the methods used in this study could yield such information as the amount of juniper tree for a given location, fuel loads for prescribed burns and better information for the best approach to remove the juniper and ultimately management juniper encroachment into grasslands.

MSc (Botany) / Department of Botany / Plant populations are determined by many elements that impose demographic filters. Following disturbance, in African savanna woodland trees regenerate both sexually and vegetatively. Vachellia karroo (Hayne) Banfi and Galasso, family Fabaceae and sub family Mimosideae, commonly known as “sweet thorn” or “soetdoring” (Afrikaans), is a leguminous shrub common throughout Southern Africa. Its distribution range is from the Southwestern Cape northwards into Namibia, Angola, Botswana, Zambia and Zimbabwe. It is a pioneer species and has the ability to encroach rapidly into grassland grazing areas. Therefore, V. karroo is considered the most important woody invader of grasslands in South Africa. This study aimed at investigating the population biology and ecology of V. karroo in the clay waterlogged site of the Nylsvley Nature Reserve. Plant height, stem circumference, canopy cover, distance between individuals were measured and disturbance levels on individuals of V. karroo were estimated during sampling. The results showed that the population of V. karroo display an adequate growth curve thus implying that the population of V. karroo in the Nylsvley Nature Reserve is healthy and viable. More mature healthy individuals were found in September and December, than during June and July; this is obviously because early summer season, and in September most of the savanna plant species were starting to actively recover from the winter dry season. This is confirmation enough that the population of V. karroo is expanding in the clay waterlogged areas of Nylsvley Nature Reserve.