Axelrod (1958) suggested that the late Tertiary shift in regional climate -- the elimination of summer rains -- had a profound influence on the evolution of biotic provinces in the American southwest. In particular, the taxa endemic to biotic provinces characterized by summer drought, e.g., the Mojave Desert, should be derived from ancestors that likely inhabited regions of summer rain, e.g., the Chihuahuan Desert. Further, the derived features of summer-drought taxa should be related to water stress. I examined Axelrod's thesis, using a combination of phylogenetic systematics, physiological ecology, and vicariance biogeography. The first chapter is a cladistic study of the pinyon pines, 13 taxa of small trees that range from the summer-wet regions of Mexico to the summer drought regions of Nevada and California. A parsimony analysis using twenty morphological characters showed that the most recently derived pinyons are from regions of summer drought. The "summer-drought" taxa are characterized by relatively few needles per fascicle. Because fewer needles per fascicle results in a reduction in the needle surface-to-volume ratio, Haller (1965) hypothesized that fewer needles in pines is an adaptation to reduce transpirational water loss. The second chapter reports on a two year study of the xylem pressure potentials of single- and double-needled fascicles of hybrid pinyons in central Arizona. The results showed no significant differences between single- and double-needles. I concluded that either needle morphology does not effect water relations, or that the relatively high precipitation during the study did not allow significant water stress to occur. The third chapter uses the methods of vicariance biogeography to search for a common pattern of relationship between southwestern biotic provinces, as indicated by the relationships of their endemic taxa. Using a biogeographic parsimony analysis, I compared the area cladograms of six taxa -- junipers, pinyon pines, the composite Palafoxia, hedgehog cactus, desert tortoises, and gecko lizards. The most parsimonious area cladogram supports Axelrod's (1958) hypothesis, but also shows that some taxa, notably the junipers, support other patterns of area relationships, e.g., summer-drought primitive. I suggest that there is no single pattern of area relationships because of the effects of the Pleistocene (including dispersal and extinction) and vicariance events other than the Tertiary climatic change, e.g., the separation of the Baja peninsula from mainland Mexico during the Miocene.

[Truncated abstract] Generally hydrologic and ecologic models operate on arbitrary time and space scales, selected by the model developer or user based on the availability of field data. In reality rainfall is highly variable not only annually, seasonally and monthly but also the intensities within a rainfall event and infiltration properties on semi-arid hillslopes can also be highly variable as a result of discontinuous vegetation cover that form mosaics of areas with vegetation and areas of bare soil. This thesis is directed at improving our understanding of the impacts of the temporal representation of rainfall and spatial heterogeneity on model predictions of hydrologic thresholds and surface runoff coefficients on semi-arid landscapes at the point and hillslope scales. We firstly quantified within storm rainfall variability across a climate gradient in Western Australia by parameterizing the bounded random cascade rainfall model with one minute rainfall from 15 locations across Western Australia. This study revealed that rainfall activity generated in the tropics had more within storm variability and a larger proportion of the storm events received the majority of rain in the first half of the event. Rainfall generated from fontal activity in the south was less variable and more evenly distributed throughout the event. Parameters from the rainfall analysis were then used as inputs into a conceptual point scale surface runoff model to investigate the sensitivity of point scale surface runoff thresholds to the resolution of rainfall inputs. This study related maximum infiltration capacities to average storm intensities (k*) and showed where model predictions of infiltration excess were most sensitive to rainfall resolution (ln k* = 0.4) and where using time averaged rainfall data can lead to an under prediction of infiltration excess and an over prediction of the amount of water entering the soil (ln k* > 2). For soils susceptible to both infiltration excess and saturation excess, total runoff sensitivity was scaled by relating drainage coefficients to average storm intensities (g*) and parameter ranges where predicted runoff was dominated by infiltration excess or saturation excess depending on the resolution of rainfall data were determined (ln g* <2). The sensitivity of surface runoff predictions and the influence of specific within storm properties were then analysed on the hillslope scale. '...' It was found that using the flow model we still get threshold behaviour in surface runoff. Where conditions produce slow surface runoff velocities, spatial heterogeneity and temporal heterogeneity influences hillslope surface runoff amounts. Where conditions create higher surface runoff velocities, the temporal structure of within storm intensities has a larger influence on runoff amounts than spatial heterogeneity. Our results show that a general understanding of the prevailing rainfall conditions and the soil's infiltration capacity can help in deciding whether high rainfall resolutions (below 1 h) are required for accurate surface runoff predictions. The results of this study can be considered a contribution to understanding the way within storm properties effect the processes on the hillslope under a range of overall storm, slope and infiltration conditions as well as an improved understanding of how different vegetation patterns function to trap runoff at different total vegetation covers and rainfall intensities.

The vegetation communities that existed in the semi-arid intermontane basins and gorges of Central Otago prior to human settlement ~750 years B.P. are poorly understood. This is because of a lack of fossil evidence and complex restructuring by anthropogenic factors, especially increased fire frequency, and more recently mammalian grazing. There is also little information regarding the effect of the lost fauna on maintaining and structuring presettlement communities, both in Central Otago and throughout the eastern South Island dryland zone. This study aims to provide a clearer understanding of the functioning of pre-settlement ecosystems in dryland Central Otago, particularly the role of the largest vertebrate herbivores, the moa (Aves: Dinornithiformes), and to explore the implications of the extinct fauna for land conservation management across New Zealand. Late Pleistocene and Holocene vegetation communities of the Central Otago lowlands were reconstructed from plant macrofossils, including seeds, leaves, and wood, excavated from rockshelter, cave, and swamp deposits throughout the region. The macrofossils represent three main vegetation types: late Pleistocene to mid (late?) Holocene basin floor wetland herb associations, Olearia-shrublands surrounding these wetlands, and mid to late Holocene open scrubland and woodland in gorges and on low altitude slopes, dominated by filiramulate Olearia, Coprosma, and Corokia, with abundant lianes (Muehlenbeckia spp. and Rubus spp.) and understorey herbs. Many native tree and shrub species that are presently widespread in the Central Otago lowlands were rare or absent prior to anthropogenic fires (e.g. Discaria toumatou, Kunzea ericoides, Leptospermum scoparium). Other tree and shrub species once present are now extinct in the region (e.g. Coprosma obconica, Plagianthus regius, Pseudopanax ferox). The loss of these indigenous woody vegetation communities was a major factor contributing to the extirpation of many small bird species, and undoubtedly also reptile and invertebrate species, from the region. Plant macrofossils from rockshelters included remains of bird nests, identifiable by desiccated feathers and eggshell amongst them. These macrofossils include the first described plant remains from the nests of moa, which were constructed from a shallow bed of twigs of locally available shrubs and lianes. Many of the twigs are 25-30 mm in length and show evidence of having been clipped by moa bills. Desiccated coprolites, mostly of moa, but also specimens attributed to Finsch�s duck (Chenonetta finschi) and red-crowned parakeet (Cyanoramphus novaezelandiae), were recovered from rockshelter excavations. Moa species associated with a sample of coprolites were identified using ancient DNA analysis, and plant macrofossils from these were examined, together with previously unexamined moa gizzard content samples excavated from mires in the eastern South Island dryland zone. The results indicate that, in addition to previously reported browsing, upland moa (Megalapteryx didinus) and heavy-footed moa (Pachyornis elephantopus) also functioned as grazers, and seeds in their coprolites are dominantly of low shrubs and ground-cover herbs. Of particular interest was the higher than expected frequency of seeds from the currently rare and threatened 'spring annual' herbs; Ceratocephala pungens and Myosurus minimus subsp. novae-zelandiae (Ranunculaceae), suggesting further research on potential ecological relationships between moa and these plants would be worthwhile. The results of this study have provided a baseline for future conservation and restoration projects in the Central Otago lowlands.

Thesis (Ph. D.)--University of New South Wales, 2006. / Title from PDF title page (viewed on Dec. 11, 2007). Includes bibliographical references (p. 179-201).

The vegetation communities that existed in the semi-arid intermontane basins and gorges of Central Otago prior to human settlement ~750 years B.P. are poorly understood. This is because of a lack of fossil evidence and complex restructuring by anthropogenic factors, especially increased fire frequency, and more recently mammalian grazing. There is also little information regarding the effect of the lost fauna on maintaining and structuring presettlement communities, both in Central Otago and throughout the eastern South Island dryland zone. This study aims to provide a clearer understanding of the functioning of pre-settlement ecosystems in dryland Central Otago, particularly the role of the largest vertebrate herbivores, the moa (Aves: Dinornithiformes), and to explore the implications of the extinct fauna for land conservation management across New Zealand. Late Pleistocene and Holocene vegetation communities of the Central Otago lowlands were reconstructed from plant macrofossils, including seeds, leaves, and wood, excavated from rockshelter, cave, and swamp deposits throughout the region. The macrofossils represent three main vegetation types: late Pleistocene to mid (late?) Holocene basin floor wetland herb associations, Olearia-shrublands surrounding these wetlands, and mid to late Holocene open scrubland and woodland in gorges and on low altitude slopes, dominated by filiramulate Olearia, Coprosma, and Corokia, with abundant lianes (Muehlenbeckia spp. and Rubus spp.) and understorey herbs. Many native tree and shrub species that are presently widespread in the Central Otago lowlands were rare or absent prior to anthropogenic fires (e.g. Discaria toumatou, Kunzea ericoides, Leptospermum scoparium). Other tree and shrub species once present are now extinct in the region (e.g. Coprosma obconica, Plagianthus regius, Pseudopanax ferox). The loss of these indigenous woody vegetation communities was a major factor contributing to the extirpation of many small bird species, and undoubtedly also reptile and invertebrate species, from the region. Plant macrofossils from rockshelters included remains of bird nests, identifiable by desiccated feathers and eggshell amongst them. These macrofossils include the first described plant remains from the nests of moa, which were constructed from a shallow bed of twigs of locally available shrubs and lianes. Many of the twigs are 25-30 mm in length and show evidence of having been clipped by moa bills. Desiccated coprolites, mostly of moa, but also specimens attributed to Finsch�s duck (Chenonetta finschi) and red-crowned parakeet (Cyanoramphus novaezelandiae), were recovered from rockshelter excavations. Moa species associated with a sample of coprolites were identified using ancient DNA analysis, and plant macrofossils from these were examined, together with previously unexamined moa gizzard content samples excavated from mires in the eastern South Island dryland zone. The results indicate that, in addition to previously reported browsing, upland moa (Megalapteryx didinus) and heavy-footed moa (Pachyornis elephantopus) also functioned as grazers, and seeds in their coprolites are dominantly of low shrubs and ground-cover herbs. Of particular interest was the higher than expected frequency of seeds from the currently rare and threatened 'spring annual' herbs; Ceratocephala pungens and Myosurus minimus subsp. novae-zelandiae (Ranunculaceae), suggesting further research on potential ecological relationships between moa and these plants would be worthwhile. The results of this study have provided a baseline for future conservation and restoration projects in the Central Otago lowlands.

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 95-100). Also available on the World Wide Web.

The world we live in is changing rapidly. Ecological, economic and social aspects and understandings are all undergoing paradigm shifts. Communities, farmers and individuals in arid zones are experiencing climate changes, more so than city dwellers. A better understanding of the current thinking in range ecology and management, especially of arid environments, is critical to the management of these delicate, complex systems. Ecosystems in equilibrium or in disequilibrium react differently to management and reclamation efforts. An understanding of the basic principles and how they evolved is important in order to apply these principles correctly in the management of arid zones. The use of keystone species and simple technologies, such as water harvesting and mulching, can all be used to reclaim and manage the arid zones. Understanding the differences between systems in equilibrium and disequilibrium can be used as a guide for planning appropriate future research in the arid zones. Searching for new indigenous species to help in the reclamation of arid zones is of the utmost importance. An ecological criterion was used to identify potential plant species for reclamation of degraded arid rangelands of southern Africa. Tripteris sinuatum and Sutherlandia microphylla were identified as possible candidates. Germination studies, with seeds harvested from naturally occurring plants, were conducted for both species. Treatments were based on the natural seed dispersal mechanisms for both species. S. microphylla has the potential to become an important plant species for reclamation purposes in arid zones of southern Africa. Not only potential new species should be sought, but also the management of species, already in use, are of critical importance. The relative palatability and survival of 16 different Atriplex species and accessions were determined at two different localities in the arid Northern Cape Province of South Africa. Significant differences were found between species at both localities. It is believed that because of the variety of species in the Atriplex genus, relative palatability and survival should be used to determine which of the different species could be useful under specific climatic and soil conditions. The establishment and reaction of Atriplex nummularia and Cassia sturti were tested for season of planting and the use of a stone mulch at two locations in the Northern Cape Province of South Africa. A. nummularia reacted the best to a moderate pruning treatments, while Cassia sturtii reacted best to severe pruning. These results should aid in the management of planted fodder plantations. Numerous attempts at improving natural veld have failed in the past. An examination of landscape function and the potential to harvest water in localized areas should drive veld improvement in arid zones. Seeds from two different plants species (Tetragonia calycina and Tripteris sinuatum) were used to inter-seed a bare patch in the Northern Cape Province of South Africa. The two species, with two treatments, (brush packing or not) in two different locally occurring eco-topes, were used to determine plant establishment. The water run-on eco-tope showed a significantly higher plant establishment percentage than the water run-off eco-tope. The establishment of perennial grass species was also found on the water run on eco-tope, three years after establishing the reclamation site. Such sites could form an important link in biodiversity conservation. / Dissertation (MSc Agric (Pasture Science))--University of Pretoria, 2007. / Plant Production and Soil Science / unrestricted

Degradation of rangeland resources leading to the desertification process is viewed in terms of human and climatic influences. While climatic impacts are important, resource utilization as practiced by man is the major cause of desertification. A multi-objective .decision methodology is developed here which is intended for the analysis of alternative management plans of rangeland watersheds under climatic variability. First, a system model is employed to portray the dynamics of a rangeland as it would respond to climatic changes and different grazing intensities. This approach allows for an interaction of inputs such as rainfall, solar radiation, and temperature with the state of the system which is a range condition index, and with outputs such as production and sediment yield. A simulation package is developed to implement the system model by actually using available data and providing some output values for production and sediment yield. At this stage a number of alternative management plans are identified. The information obtained from the simulation as well as other information of interest are represented by performance criteria, leading to an array of alternative versus criteria. Then, management plans need to be evaluated as they would impact the criteria. A multiobjective decision making technique is selected to perform the analysis for an identification of prefered management alternatives.

Bibliography: leaves 146-152.

Bibliography: leaves 146-152 / 152 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, 1987