Thesis (M. Agr. St.)--University of Queensland, Gatton, (2002?). / Includes bibliographical references.

Thesis (M. Agr. Sc.)--University of Queensland, 2003. / Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2002. / Typescript (photocopy). Includes bibliographical references (leaves 69-76). Also available on the World Wide Web.

Lake sediments from inland endoreic (saline) lakes in the semi-arid Ebro Basin, NE Spain have been analysed to provide a history of lake level, vegetation, catchment erosion and anthropogenic activity over the last 10,000 years. Analysis was undertaken for pollen, macrofossils (seeds, Cladocera ephippia, Chironomid head capsules etc), charcoal, geochemistry (total cations/trace metals, sulphate, carbonate & LOI) and sediment composition. Fourteen AMS radiocarbon dates provide dating control. Seven cores were investigated from 4 seasonal playa lakes, I shallow (<1.5m) semi-permanent salt lake, 1 deep (5.0m) permanent salt lake and 1 Medieval-age reservoir. Over 40 surface samples were also taken to investigate modern analogue environments. A review of the use and interpretation of saline lake macrophytes (seeds & pollen), Cladocera and Chironomids in palaeolimnology is provided, with special emphasis on those found in Spanish salt lakes. Taphonomic problems and nearshore-offshore facies were also investigated using a surface sample transect across a small playa lake. A surface sample pollen data set from 30 lakes in the Ebro Basin is presented and the implications for palaeo-interpretation discussed. The sensitivity of the pollen record as a climate indicator is investigated using 6 sites across a climatic gradient from sub-humid to semi-arid. Lake level reconstruction is based on an 8 stage semi-quantitative palaeohydrological model, developed from a surface sample data set from 32 lakes ranging from temporary to permanent, and hypersaline to freshwater. A simple hydrological model for groundwater fed lakes is also discussed which can be used to quantify these palaeohydrological changes. The early Holocene (<9.3-8.6Kyr BP) was characterised by semi-arid extreme continental conditions in the Ebro Basin, with an extensive Juniper thurifera woodland. Lake levels rose to their highest point in the Holocene between 8.6-7.2Kyr BP when evergreen oak and pine forest dominated. This is interrupted by a short recession in lake level between 8.2-7.6Kyr BP. A distinct regional early-Neolithic fire and clearance event occurs between 7.7-7.3Kyr BP. A drop in lake level and development of a monospecific pine forest (P. halepensis) indicates warmer and drier conditions in the mid Holocene (7.2-5.4Kyr BP). Evergreen oak reappears as forest cover declines after 5.4Kyr BP, although this is not marked by any increase in charcoal or cultivation indicators. Low groundwater but moderate lake levels (4.0-2.7Kyr BP) may be linked to high summer storm frequency and low winter rainfall. This coincides with catchment erosion and valley floor alluviation. Lake level rises again significantly between 2.7-1.8Kyr BP during Iberian and Roman times when archaeological evidence indicates a peak in population. Agriculture changes from small scale pastoral to small scale arable without any further decline in woodland cover. A rapid fall in lake level at ca. 1.8Kyr BP is followed by complete forest recovery (P. halepensis) and depopulation, until major deforestation around 1.4Kyr BP marks the arrival of the Visigoths/Arabs and extensive nomadic pastoralism. Intensive grazing pressure or lower temperatures resulted in Juniperus increasing again between 1.4-0.4Kyr BP. This also coincides with a second period of catchment erosion and valley floor alluviation. After ca. 0.4Kyr BP, lake levels have increased along with extensive olive cultivation and the development of modern (irrigated) arable agriculture.

No description available.

Riparian areas connect terrestrial and aquatic environments. The objectives of this research were to compare the vegetation community composition and structure eight years after harvesting and to explore successional trends among buffer widths at year eight after disturbance and in a chronosequence. A series of small clearcuts were harvested in 1998 in a 70 year old second growth stand at the Malcolm Knapp Research Forest and 0m, 10m and 30m reserve zones were established adjacent to the streams. Each treatment was replicated 3 times and 3 unharvested streams were identified as controls. Overstory and understory vegetation was measured annually from the year of harvest. Canopy density was measured using a densiometer. For comparative purposes, four vegetation plots were added in riparian areas within an 1868 and an old-growth stand during the summer of 2006. Eight years after harvesting, understory vegetation development is affected by buffer width due to higher light levels, and species richness in the 10m and 0m buffers is higher than in the 30m buffer and control. Shrubs and deciduous trees dominate the 0m and 10m buffer treatments. Proximity to the stream does not affect the composition and abundance of species with the exception of herbs and mosses. In the 10m and 30m buffer treatments, up to 15% overstory trees were windthrown in the first 2 years after harvest producing large canopy gaps. Consequently, the understory development in the 10m and 30m buffers is more like that in the 1868 and old-growth stands than in the controls, but these treatments still lack the very large trees and microsite heterogeneity of the older stands. In the unharvested controls, self-thinning continues and there has been 30% mortality of mostly smaller trees over the past 8 years. However, overstory density remains high. The 0m buffer was quickly colonized by shrubs and ferns and within the last 2 years has become dominated by juvenile deciduous trees. Overall, the 10m buffer balances timber production with the maintenance of overstory and understory structure dynamics. The combined effect of light from the edge and partial windthrow is accelerating succession towards a more mature or ‘old-growth’ condition.

No description available.

This thesis examines the use of multi-spectral remotely sensed data in the management of the North York Moors, an upland area of heather moorland in northern England. A series of ground radiometer surveys and airborne simulations are analysed to determine the relative importance of spatial, spectral and temporal resolution as characteristics of earth resources satellites in this environment. Particular reference is made to the potential for selecting and combining data from the Landsat MSS, TM and the SPOT HRV sensors. The results show that spectral resolution can be critical in isolating and recognising elements of the moorland community by their spectral response, especially at the most detailed levels of vegetational description. Temporal resolution has little effect on the discrimination of targets within the heather dominated areas but affects the separability of the major communities of heather, bracken and sedges. Change in spatial resolution has no clear effect on the spectral uniformity and spectral separation of the elements of the heather dominated areas. The interaction between spectral and spatial resolution is more important in isolating the major communities, where the requirement for spatial precision is balanced against the need to suppress spectral variation within the moorland. The hypothesis that multi-spectral remotely sensed data can provide critical information on the distribution and status of moorland vegetation is not refuted in this thesis. Remotely sensed data would make the greatest contribution to management if linked to other spatial data as part of a Geographical Information System. In the absence of such a formal structure satellite imagery can still provide a regular and unique inventory of the moorland habitat which will increase the efficiency of management.

No description available.

Alpine and arctic treelines have been viewed as sensitive indicators of global climate change. While many treelines have advanced under warmer climate regimes in recent decades, the response has not been uniform. Some of this variability may be attributable to the impacts of herbivores. This study investigates the interacting effects of herbivory, climate, and understory vegetation on mountain birch establishment at treeline in the Scandes Mountains of northern Sweden. An extensive dendrochronological database was created to determine periods of establishment, which were then regressed against reindeer (Rangifer tarandus, L.) population data and historical climate data. Vegetation classifications were also created and analyzed to determine if establishment patterns vary by understory vegetation type. I have tested the hypothesis that tree establishment varies within the treeline ecotone and that high reindeer stocking levels negatively impact establishment. Weakly positive responses to herbivory were observed in patterns of tree establishment at treeline. This indicates that reindeer may modestly promote treeline advance at low densities, contradicting some previous research, but many of the results were not statistically significant. The climate variables found to have significant relationships with establishment were inconsistent across herding districts and aggregation levels. No connections between vegetation assemblages and establishment or between vegetation assemblages and reindeer use were observed.