No description available.

No description available.

In mountains throughout western North America, large, mixed-severity fires produce a mosaic of low and high tree mortality. Following wildfire, plant communities may recover to their pre-fire state, or may remain altered in composition and structure. In this study I quantified the extent to which fire severity influenced post-fire vegetation composition and structure in comparison to pre-fire states in the Santa Catalina Mountains, Arizona, USA. I used a stratified random design that sampled plots across ecological units and fire severity classes. Tree diameter at breast height (DBH), shrub cover, and seedling and sapling density was recorded by species in five plant communities: oak/pinyon/juniper woodland on hills landscapes of mixed lithology; Madrean pine-oak forest/woodland on granite, gneiss, or metasedimentary rock; Madrean oak/conifer/manzanita on rock outcrops; ponderosa pine forest on granite, gneiss, and similar rocks; and mixed conifer forest on metasedimentary landscapes. Subsets of these data were then used to reconstruct overstory vegetation present when the Bullock (2002) and Aspen (2003) fires occurred. Data from a 1984 pre-fire study was used to substantiate the overstory reconstruction and to determine shrub understory components. I tested the hypothesis that tree mortality was a determinant of post-fire shrub cover, and calculated post-fire importance values (IVs) of tree and shrub components. Ordination and non-metric multidimensional scaling (NMS) of IVs confirmed that overstory reconstruction aligned with 1984 field surveys. Tree mortality was a predictor of post-fire shrub cover, but only with certain species in specific ecological units. Ordinations indicated that tree composition in post-fire plots has diverged from that in pre-fire plots in all but the oak/ pinyon/juniper community. Ordination of shrub components indicated novel configurations of post-fire communities, including association of pre-fire mixed conifer elements with oak woodland elements. The intermixing of tree species in mid- and higher-elevation communities with those historically confined to lower elevation community types suggests that recent fires has disrupted vegetation inertia and initiated novel ecological change. The re-structuring observed within these community types are in agreement with projections that disturbance and climate change will interact to facilitate the spread of lower elevation species to higher elevation zones. Fire x climate interactions may therefore trigger long-lasting changes to ecosystem structure in ways not predicted by models of fire-effects or climate-effects occurring in isolation from each other.

No description available.

Plants with similar traits compete for resources. If related taxa share similar traits, phylogenetic relationships may predict competitive outcomes. Although plants compete for pollinators, flowers are rarely considered in community-assembly theory. I tested the hypothesis that plant communities are structured by competition for pollination. I inventoried communities at three spatial scales, measured seven flower traits, and tested the observed patterns against those generated by a null model to judge if community members were more or less similar in floral traits than expected by chance. I also measured the phylogenetic relatedness of community members to gauge trait-conservatism. Clustering of visually attractive traits suggests they promote facilitation of pollinators while over-dispersion of morphological traits suggests they partition pollinators in to avoid competition. Communities were phylogenetically even, but relatedness did not explain floral trait patterns. I suggest that flowers represent an ecological niche through which species can be sorted.

A novel interpretation of leaf mass variation in plants has been recently proposed based on its relationship with variation in leafing intensity – number of leaves produced per unit remaining above-ground dry mass. It is now widely established that between species variation in these two traits is strongly, negatively (and isometrically) correlated for woody and herbaceous species. Possible fitness advantages of higher leafing intensity (requiring smaller leaf size) can be interpreted in terms of the greater concentration of axillary meristems (larger ‘bud bank’), which may provide greater potential deployment flexibility for growth or reproduction. However, no research to date has addressed how these two traits are related at different scales, specifically at the between-individual (within-species) level, or between sexes in dioecious species. For the majority of 24 herbaceous angiosperms studied here, between-individual (within species) co-variation in leaf size and leafing intensity displayed as an isometric trade-off. For the few species with allometric trade-offs, plants with smaller body size produced disproportionately more leaves, indicating a possible mechanism for promoting reproductive economy when plant size is suppressed (e.g. by competition). For two out of three woody dioecious species, and two out of three herbaceous dioecious species, males tended to produce more, smaller leaves than females, possibly promoting pollen dispersal through a more broadly-spaced floral display (developing from more numerous axillary meristems). In contrast, the larger (but fewer) leaves in females may serve to maximize local photosynthetic resources available for axillary fruit and seed maturation. Males and females did not differ in branching rates associated with differences in leafing intensities, but in one herbaceous species, higher leafing intensity in males was associated with higher flower production than in females. In the larger 24-species data set, there was no evidence that species with higher leafing intensity (providing more axillary meristems) was associated with either a greater magnitude or a greater flexibility in branching or flowering intensity. Additional studies are required to explore the possibility that large ‘bud banks’ of axillary meristems (conferred by high leafing intensity) may promote effective mechanisms for tolerating environmental variability, responding to damage (e.g. from herbivory), and/or maximizing reproductive economy. / Thesis (Master, Biology) -- Queen's University, 2009-10-27 21:20:03.509

This study was conducted to determine if, and how, over storey proteoid shrubs affect the species richness of a southern Cape mountain fynbos community. Protea eximia, P. lorifolia and P. repens were the dominant overstorey shrubs in the community studied. The percentage canopy cover and density of overstorey protea shrubs before a fire were regressed against the a-diversity of understorey species after a fire, for spatial scales ranging from 1 - 100m². High canopy cover percentages (≥ 50%) and high densities (≥ 30 plants per 100m²) of overstorey proteas before a fire enriched the a-diversity levels of understorey species after a fire. The spatial scale at which α-diversity was measured affected results. The number of understorey species at a site, where overstorey proteas were absent for several fire-cycles, was compared with those where overstorey proteas persisted. The number of understorey species was least where the overstorey proteas were lacking for several fire-cycles, but results also depended on the spatial scale at which α-diversity was measured. The basal cover percentage and density of sprouting understorey species of two sites, burned at several short (6 year) fire-cycles and where overstorey proteas were lacking, were compared with those of an adjacent site which was not burned for 28 years and where the overstorey proteas persisted. Where several short fire-cycles eliminated the overstorey proteas, the basal cover percentage of understorey sprouters was approximately 32% higher than where the overstorey shrubs persisted. The number of understorey species in dense clumps of understorey sprouters was contrasted against those on 0.25m² quadrats located in the open and under burned skeletons of overstorey protease In dense clumps of sprouters the mean number of understorey species was less than half of that for quadrats located in the open, or for quadrats located under the burned protea skeletons. Species specific competitive interactions amongst overstorey protea and understorey sprouter species were examined for several pyric successional stages. Competitive interactions between overstorey proteas and understorey sprouters were evident in all pyric successional stages. Results indicate that the overstorey proteoid shrubs are important to restrain the competitive ability of understorey sprouters, to prevent homogeneity in post-fire regeneration niches and to amplify within-community patchiness of understorey species, which ultimately enhances the species richness of fynbos communities. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.

The geology, topography, soils and climate of the Namib Desert Park south of 23 S. Lat. are described briefly. The vegetation was investigated using the techniques of the Zurich - Montpellier school of phytosociology. Floristic and other site data were collected from 472 sites in the standard Braun - Blanquet manner and the techniques are described in some detail. These data are presented by means of phytosociological tables and detailed descriptions of each community. A total of 34 noda, communities and sub-communities, were delimited in the study area and the floristic and ecological relationships of these are discussed. Only a few of the communities can be assigned to syntaxa from other parts of the world or southern Africa because most of the Namib Desert communities seemed too different to be compared to associations from North Africa, the Middle East, South America or Australia on more than a superficial, structural basis. Very few data from other arid or semi-arid areas in southern Africa have received formal phytosociological treatment and there is therefore insufficient material to draw meaningful comparisons. The "foam structure" described by Volk & Geyger (1970) was found to be widely distributed in soils of the plains of the Namib Desert, and it was shown to have a profound influence on water penetration. The effects on vegetation development are discussed. The study generated a number of questions about the vegetation and ecosystems of the Namib Desert and some recommendations are made concerning future synecological and autecological studies. A list of species and synonyms of the names of all higher plants recorded in the study area are given in Appendix I. It is concluded that the Braun - Blanquet method is efficient in terms of time required to collect data which can be used for a number of purposes, but that a classification of vegetation ' should be followed up by autecological and detailed synecological studies of species (particularly those which characterize communities) and individual communities to determine the controlling factors more precisely and to enable more accurate predictions concerning the effects of management programmes to be made. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1976.

The coastal forests of Kenya represent a rare and threatened forest type which has over 3,000 plant taxa, of which about 500 are endemic. The patches which comprise this forest type include sacred forests, the kayas, that are rich in biodiversity. The aim of the study report was to investigate the phytosociological relationships in two selected kayas, Mtswakara and Fungo, and the plant utilisation by the people of the Duruma and Giriama tribes who live around these forests. The vegetation was sampled using the phytosociological approach developed by Braun-Blanquet. In kaya Mtswakara 51 relevés of 0.2 ha. were sampled and a total of 317 species from 191 genera in 79 families were recorded, representing 48 tree species, 134 shrubs, 82 herbs, 45 climbers, and 8 epiphytes. In kaya Fungo, 280 species from 213 genera in 74 families, representing 35 tree species, 125 shrubs, 73 herbs, 43 climbers, and 3 epiphytes, were recorded in 54 relevés. TWINSPAN classification of the data indicated the existence of four plant communities and six sub-communities in kaya Mtswakara; and three plant communities, four sub-communities, three stages, three sub-stages and one undetermined vegetation type in kaya Fungo. The phytosociological results indicated that diagnostic species for plant communities are not necessarily the dominant tree species; and interactions of edaphic factors, plant resource extraction, fire and grazing influenced the formation and distribution of vegetation types. The human populations living around the forests depend upon and utilise plant species found in the kayas to meet some of their basic domestic needs and cultural requirements. But, unlike in the past, the council of kaya elders (ngambi) cannot address all the forest management problems, due to factors such as increased disrespect of cultural traditions in the communities, increasing demands of forest plant resources due to population increase, conflicts between local faction groups claiming legitimacy in kaya management and socio-political changes. Surveys conducted in the local markets showed that although forest plants formed a small percentage of the building poles traded, the firewood trade was considerable. In addition to the regular market trade, there is a 'house-to-house' trade conducted by some community members who sell poles, timber planks and firewood which probably had been collected from the kayas. Although a considerable amount of pole resource wais available in the kayas the observed vegetation degeneration through plant resource extraction, fire, and grazing, was likely to be at a faster rate compared to the natural regenerative ability of the forests, thus threatening the existence of these kayas forests. The immediate challenges facing kaya conservation, therefore, include re-empowering the cultural management systems, and the provision of short-term and long-term alternatives for the forest plant resources in the face of increasing demand for the resources and social change. / Thesis (M.Sc.)-University of Natal, Durban, 2000. / People and Plants (UNESCO)

An area and a point-based technique were used together at each of the same 75 sampling sites (stands), on a Sourish-Mixed Bushveld farm, to collect data for the classification and mapping of the vegetation. Both sets of data were synthesized using the same computer program package and the efficacy of the resulting classifications as well as the efficiency of the two field sampling techniques was compared. Following this, a continuous 7 752 point (1 m apart) transect was carried out, traversing the farm, in order to determine the optimum scales at which to sample Sourish-Mixed Bushveld so as to increase classification efficacy and improve community boundary recognition. The results indicated that (1) the arbitrarily chosen sampling scale of 1:8 000 was too large for "farm-scale" studies; (2) the area-based method proved to be satisfactory in that the classification and vegetation map produced with this method were verified spatially and environmentally; (3) the point-based method was deficient as a classificatory and mapping tool at large scales, since too few species were recorded with this method to make any sense of the classification and mapping of the vegetation was not possible; (4) less time per species was spent using the area-based method but because more species per stand were recorded with this method, the point-based method was quicker per stand; (5) the area-based method was easier to use in dense vegetation and irregular terrain; and (6) the optimum sampling scales for Sourish-Mixed Bushveld, as indicated by the synthesis of the continuous transect data, are about 1:12 000, 1:50 000 and 1:250 000. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.