Thesis (M.S.)--Oregon State University, 1978. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 186-192).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Typescript. Vita. Description based on print version record. Includes bibliographical references.

Seven outbreaks of Douglas-fir tussock moth, Orgyia pseudotsugata McDunnough, have recurred in the interior of British Columbia since 1915. But little is known about their impacts on renewable resources in affected stands. A study was undertaken to examine effects of the most recent outbreak on understory vegetation and tree productivity near Kamloops, British Columbia. Dry weight forage production was sampled from 1m² circular plots under various levels of stand crown cover (0-96%) and density (0-45.9m²/ha), as modified by defoliation. Crown cover was determined using a moosehorn, and from vertical photographs obtained with a 160° lens mounted on a conventional camera. Stand density was determined using a 20 factor prism. Increment cores were obtained at breast height, and radial growth analysed under the Addo-X. Ring width behaviour was compared with occurrence of past outbreaks. The ecological literature on 0. pseudotsugata was reviewed. Negligible amounts of forage were obtained from many plots with undefoliated trees. In defoliated plots with live trees, total forage production ranged from 0.0 under 96% crown cover and 45.9 m²/ha density to 648.9 kg/ha under 50% crown cover and 16.0 m²/ha density. The average yield in small openings was 3667.4 kg/ha. High variability was evident. In one stand, two years following its defoliation and consequent death, total forage yields exceeded those from nearby small openings. Forage yield data were described better by logarithmic models than by hyperbolic ones, at 95% probability. Impacts on tree growth were not demonstrable one year following defoliation. Many trees recovered even from complete defoliation. Insect outbreaks and periods of slow tree growth coincided, but quite inconsistently. Apparently, most scattered infestation patches develop independently of each other. Grazing values should increase in seriously defoliated stands even without range seeding. On poor sites and in stands managed primarily for forage production, outbreaks of 0. pseudotsugata may be left alone without necessarily endangering remote stands. Selective control favoring better sites managed for tree production should improve efficiency of investing scarce funds in protection of the inventory. Tree growth and insect outbreaks may be under the influence of some regional climatic factor, but local factors are also important. A need remains for long term impact studies on tree growth, forage yield and nutrient status, and other resources. / Forestry, Faculty of / Graduate

Hieracium pilosella is an invasive weed of New Zealand's short tussock grasslands. Since the 1960s, the abundance of H. pilosella has dramatically increased; it is now thought to occur in 6 million hectares of New Zealand (Espie, 2001), predominantly in grasslands. It is at least common in 42% of this area (Espie, 2001). Ecology is inherently spatial and as plants closely interact with their direct neighbours, the spatial arrangement of plants is vital to their functioning. A handful of recently published articles have implicated spatial structure of plant communities in theories of plant competition, resource use and the invasion of plant communities. The aims of this thesis were to: 1) determine if there are consistent spatial patterns in New Zealand's short tussock grasslands at relatively small scales (i.e. spatial relationships between individuals); 2) investigate how the invasion of H. pilosella may be altering these spatial patterns; and 3) establish if the spatial patterns of species, life-forms and root systems are being altered in different ways. Spatial patterns of both tussock and inter-tussock species, life-forms and root functional groups were evaluated at a range of short tussock grassland sites across a gradient of H. pilosella invasion levels in Canterbury, using both join-count statistics and Ripley's K-function. A classification system for the root functional groups of vascular species in these communities was developed and applied. It was found that species, life-forms and root functional groups in short tussock grasslands had generally consistent spatial patterns across sites both within and between species. These patterns were variable between significantly different levels of H. pilosella ground cover. The type of spatial pattern exhibited, and the way it was altered differed between species, life-form and root functional groups. For example, tussocks exhibited increased regularity up to scales of 160 cm and increasing aggregation at scales up to 500 cm, with increases in H. pilosella abundance. In contrast, both Agrostis capillaris and herbaceous chamaephytes had increased aggregation across scales up to 160 cm. These differences in spatial patterns along the gradient of invasion are a strong indication that H. pilosella is structurally fragmenting New Zealand's short tussock grasslands. This fragmentation is likely to have far reaching effects including the disturbance of invertebrate communities and the disruption of ecosystem services including pollination, vegetation regeneration, and nutrient cycling.

Hieracium pilosella is an invasive weed of New Zealand's short tussock grasslands. Since the 1960s, the abundance of H. pilosella has dramatically increased; it is now thought to occur in 6 million hectares of New Zealand (Espie, 2001), predominantly in grasslands. It is at least common in 42% of this area (Espie, 2001). Ecology is inherently spatial and as plants closely interact with their direct neighbours, the spatial arrangement of plants is vital to their functioning. A handful of recently published articles have implicated spatial structure of plant communities in theories of plant competition, resource use and the invasion of plant communities. The aims of this thesis were to: 1) determine if there are consistent spatial patterns in New Zealand's short tussock grasslands at relatively small scales (i.e. spatial relationships between individuals); 2) investigate how the invasion of H. pilosella may be altering these spatial patterns; and 3) establish if the spatial patterns of species, life-forms and root systems are being altered in different ways. Spatial patterns of both tussock and inter-tussock species, life-forms and root functional groups were evaluated at a range of short tussock grassland sites across a gradient of H. pilosella invasion levels in Canterbury, using both join-count statistics and Ripley's K-function. A classification system for the root functional groups of vascular species in these communities was developed and applied. It was found that species, life-forms and root functional groups in short tussock grasslands had generally consistent spatial patterns across sites both within and between species. These patterns were variable between significantly different levels of H. pilosella ground cover. The type of spatial pattern exhibited, and the way it was altered differed between species, life-form and root functional groups. For example, tussocks exhibited increased regularity up to scales of 160 cm and increasing aggregation at scales up to 500 cm, with increases in H. pilosella abundance. In contrast, both Agrostis capillaris and herbaceous chamaephytes had increased aggregation across scales up to 160 cm. These differences in spatial patterns along the gradient of invasion are a strong indication that H. pilosella is structurally fragmenting New Zealand's short tussock grasslands. This fragmentation is likely to have far reaching effects including the disturbance of invertebrate communities and the disruption of ecosystem services including pollination, vegetation regeneration, and nutrient cycling.

The importance of several factors in limiting recovery from defoliation was investigated in field-grown plants of Agropyron desertorum and Agropyron spicatum exposed to drought , natural or irrigated conditions. Leaf extension rate, components of leaf area production, number of metabolically active axillary buds and carbohydrate availability were examined on the same plants immediately after defoliation and/or in the following spring from 1984 until 1986. The diurnal course of leaf growth did not relate to turgor pressure in the expanded portion of leaf laminae. Rather growth was apparently associated with air temperature. Leaf extension rate was lower under drought than under better moisture levels during 1984 to 1986. For both species, reduced growth rates and shorter growth periods resulted in reduced tiller height, leaf number and leaf size under drought compared with natural or irrigated conditions in 1985 and 1986, but not in 1984. As a result, leaf area and/or yields were also lower under drought in 1985 and 1986, and lowest under drought plus defoliation in 1986. Production of daughter tillers immediately after defoliation was also lowest under drought. Regrowth capacity of both species was not limited by axillary bud number, size or viability immediately after defoliation under any water level in 1986. In early spring, however, tiller number and growth were lower on clipped than on unclipped plants of both species under drought and irrigated conditions in 1986, and under all water levels in 1987; this resulted in considerably reduced photosynthetic canopies on clipped plants. Crown and root total nonstructural carbohydrate (TNC) pools were higher under drought than under better moisture levels in A. desertorum and A. spicatum in early spring 1986. These high pools of TNC apparently enhanced the production of etiolated regrowth in both species when meristematic limitations did not exist in early spring. The productive potential of both Agropyron species will probably not be affected following a late and severe defoliation under drought. However, vegetative growth and/or productivity, and probably the persistence of these species in the community, will be reduced after two or more years of late and heavy defoliations under drought.

Global temperatures are expected to increase by 1.1 to 6.4°C over the next century and, over the same period, nitrogen inputs to terrestrial ecosystems are expected to increase as a result of increased crop fertilisation and atmospheric nitrogen deposition. Both of these global change drivers are expected to affect net carbon balance by increasing both gross primary production and ecosystem respiration, yet the balance between these processes, and the potential interactive effects of the drivers, require quantification. The ability to accurately predict the effects of warming and nitrogen addition on all components of terrestrial carbon balance will be critical in determining the likely positive feedback to rising atmospheric CO₂ from terrestrial ecosystems. Tussock grasslands are a widespread and important carbon store within New Zealand and are representative of temperate grasslands worldwide. This thesis addresses the question: Will tussock grasslands act as a positive feedback to rising atmospheric CO₂ concentration in response to soil warming and nitrogen addition? Using a combination of controlled-environment and field-scale studies of tussock grassland, net ecosystem carbon exchange was partitioned into gross primary production, ecosystem respiration and the autotrophic and heterotrophic components of soil respiration. Soil respiration in the field increased by 41% in response to a 3°C soil warming treatment and by 12% in response to a 50 kg N ha⁻¹ y⁻¹ nitrogen addition treatment. Only warming resulted in enhanced heterotrophic decomposition of soil organic matter (37% increase). However, a controlled-environment study indicated that caution must be used when interpreting temperature responses of heterotrophic respiration from root-free soils, as priming effects were shown to decrease the sensitivity of heterotrophic respiration to temperature. Measurements of net ecosystem exchange in the field showed that warming-enhanced heterotrophic respiration lead to a significant 49 g m⁻² reduction in net ecosystem carbon uptake. Neither nitrogen addition nor combined warming and nitrogen addition treatment resulted in significant changes in net ecosystem carbon balance. These results suggest that tussock grasslands will act as a positive feedback to rising atmospheric CO₂ concentration. However, increased nitrogen deposition will serve as a potential mitigating factor for climate driven feedbacks.

There has been a noticeable shift in focus in biodiversity research in New Zealand over recent decades. Research has traditionally focused on biodiversity protection on the public estate, which was comprised primarily of ecosystems with lower productive potential (generally over 500m asl). Private lands generally have higher production potential and are often used for intensive cultivation and agricultural practices. They still however have significant potential for protecting biodiversity values. One of the key tools for protecting biodiversity values on privately owned lands in the Canterbury region are through legally binding QEII open space covenants and there is significant potential through industry certifications. QEII covenants are placed on the land in perpetuity and provide legally binding protection for biodiversity or landscape values within the covenant. This protection is voluntary and allows the land owner to continue to use the land for economic benefit providing it does not prove detrimental to biodiversity through monitoring outcomes. Case studies of QEII covenants that contain grazing clauses in the Canterbury region were used to determine what values are present and what monitoring is occurring in the field within these ecosystems. Photopoints and informal visual monitoring were the primary methods used by the QEII representatives to monitor vegetation in all of the covenants. Monitoring forms a critical feedback for all biodiversity protection. It is especially important to have an accurate feedback on vegetation condition and change from monitoring on properties that are grazed. Monitoring needs to be capable of providing sufficient information on vegetation change on these sites so that the most suitable grazing levels can be obtained by land managers. This thesis focuses on monitoring methods to ensure that this feedback is suitable and that the methods are cost effective. Current vegetation monitoring techniques were reviewed to determine which methods would be most suited to monitoring in these ecosystems where resources are tightly restricted and observers may not have existing skills and experience in monitoring these ecosystems. Methods reviewed were quadrats, transects, height-frequencies, photopoints, needle point, biomass, tagged plants, visual rank and remote sensing. Each method is described and then assessed on its suitability for monitoring tussock shrublands, with cost effectiveness being an important criterion. Of these methods quadrats, transects and height-frequencies were the most robust but also the most intensive and least cost effective methods. Visual rank, needle point and photopoints were the most cost effective, but are generally suited to monitoring single objectives. In most cases a combination of methods would be ideal to suit the objectives of the monitoring. QEII photopoint monitoring should follow guidelines more closely and include more complimentary information with their photographs. Clear monitoring objectives should be developed for every covenant that is grazed and these need to be determined before it is possible to accurately select appropriate monitoring methods. These objectives will also provide the monitoring program with more structure and direction. If possible a detailed management plan for each grazed covenant would be beneficial for values present. QEII are in a unique position, where they have the potential to develop a data base of biodiversity information for private land and contribute to other projects like the National Vegetation Survey (NVS).

There has been a noticeable shift in focus in biodiversity research in New Zealand over recent decades. Research has traditionally focused on biodiversity protection on the public estate, which was comprised primarily of ecosystems with lower productive potential (generally over 500m asl). Private lands generally have higher production potential and are often used for intensive cultivation and agricultural practices. They still however have significant potential for protecting biodiversity values. One of the key tools for protecting biodiversity values on privately owned lands in the Canterbury region are through legally binding QEII open space covenants and there is significant potential through industry certifications. QEII covenants are placed on the land in perpetuity and provide legally binding protection for biodiversity or landscape values within the covenant. This protection is voluntary and allows the land owner to continue to use the land for economic benefit providing it does not prove detrimental to biodiversity through monitoring outcomes. Case studies of QEII covenants that contain grazing clauses in the Canterbury region were used to determine what values are present and what monitoring is occurring in the field within these ecosystems. Photopoints and informal visual monitoring were the primary methods used by the QEII representatives to monitor vegetation in all of the covenants. Monitoring forms a critical feedback for all biodiversity protection. It is especially important to have an accurate feedback on vegetation condition and change from monitoring on properties that are grazed. Monitoring needs to be capable of providing sufficient information on vegetation change on these sites so that the most suitable grazing levels can be obtained by land managers. This thesis focuses on monitoring methods to ensure that this feedback is suitable and that the methods are cost effective. Current vegetation monitoring techniques were reviewed to determine which methods would be most suited to monitoring in these ecosystems where resources are tightly restricted and observers may not have existing skills and experience in monitoring these ecosystems. Methods reviewed were quadrats, transects, height-frequencies, photopoints, needle point, biomass, tagged plants, visual rank and remote sensing. Each method is described and then assessed on its suitability for monitoring tussock shrublands, with cost effectiveness being an important criterion. Of these methods quadrats, transects and height-frequencies were the most robust but also the most intensive and least cost effective methods. Visual rank, needle point and photopoints were the most cost effective, but are generally suited to monitoring single objectives. In most cases a combination of methods would be ideal to suit the objectives of the monitoring. QEII photopoint monitoring should follow guidelines more closely and include more complimentary information with their photographs. Clear monitoring objectives should be developed for every covenant that is grazed and these need to be determined before it is possible to accurately select appropriate monitoring methods. These objectives will also provide the monitoring program with more structure and direction. If possible a detailed management plan for each grazed covenant would be beneficial for values present. QEII are in a unique position, where they have the potential to develop a data base of biodiversity information for private land and contribute to other projects like the National Vegetation Survey (NVS).