In this thesis I investigate the influence of aggression by females in setting breeding density and maintaining monogamy in a population of willow ptarmigan (Lagopus lagopus). The aims of the study were: 1) to test the hypothesis that female willow ptarmigan determine their own breeding density by spacing behaviour, independently of male density; 2) to evaluate the effect of interactions between the sexes on final breeding density; and 3) to examine factors which may constrain willow ptarmigan populations to monogamy. Sex ratio of the population was altered in spring by continuous removal of most males and females from separate plots. The effect of removals on numbers of the same and the opposite sex was monitored. The following results were obtained and conclusions reached: 1) Females and males defend territories against individuals of the same sex, and this behaviour prevents some potential recruits from breeding. Physiologically mature yearling females and males settled in response to the removal of territorial birds of like sex. 2) Density of territorial males may not determine the number of females that breed. Females settled at high density, despite a reduction in the density of males, defended territories against each other within the enlarged territories of the remaining males, and mated polygynously. 3) Settlement patterns and subsequent territory sizes of males may affect density of both males and females. Females preferred territories of medium to large size, and males with smaller territories often remained unmated. Competition by yearling males for limited space on the breeding area may reduce territory size below that acceptable to females. Females may also alter settlement patterns of males by ignoring territorial boundaries of males and inciting interactions between neighboring cocks. 4) Unshared male vigilance is not essential to, but may improve, female reproductive success in years of high predation. Polygynous females had similar breeding success and survived as well as monogamous females, except in a year of high nest predation when they suffered higher nest loss. 5) The aggressive behaviour of females may prevent polygyny from occurring in unmanipulated populations, if a polygyny threshold exists. Females are able to defend territories which are similar in size to those of males and thus can prevent secondary females from settling. Results of this study indicate that aggressive behaviour of females in a monogamous species may be an important factor in regulating population density. Future studies should examine physiological and ecological factors influencing agonistic behaviour of females and should attempt to manipulate female aggressiveness to test whether changes in this behaviour can cause changes in population density. / Science, Faculty of / Zoology, Department of / Graduate

The detrimental effects of climate change and the threat of diminishing fossil fuel reserves is forcing society to search for renewable sources of energy. Energy can be derived from the biomass of plant material by co-fire combustion with coal or on its own for the production of electricity. Energy can also be created by converting the plant biomass into ethanol, a gasoline substitute. When converted into bioenergy, plant biomass from Short Rotation Woody Crop (SRWC) systems has the potential to offset the use of fossil fuels if the yields can be maintained at profitable levels. The effect of first year application of nitrogen (N) fertilizer on willow biomass production in a SRWC system is not well understood. Using field and growth chamber studies, the objectives of this study were to 1) determine biomass production in the growing seasons following a single application of N fertilizer in the year of planting, 2) determine the N recovery for five willow clones using a 15N tracer, and 3) evaluate the effects of various types and rates of fertilizers on biomass production. Objectives 1 and 2 were addressed in a field fertilization study conducted on agricultural lands in the Moist Mixed Grassland ecozone and at tree nursery in the Boreal Transition ecozone. Willow cuttings were planted and fertilized with 100 kg N ha-1 of granular ammonium nitrate. Twelve trees were fertilized with 5 kg N ha-1 of double 15N-labeled ammonium nitrate and 95 kg N ha-1 of granular ammonium nitrate. In the first growing season trees were browsed to a uniform height making biomass measurements unrepresentative of production potential. Annual shoot biomass production in the second year, however, was 0.39 to 2.0 Mg ha-1 and was not found to be significantly different between fertilizer treatments. Nitrogen recovery by entire trees ranged from 2.87 to 10.6 % in the first growing season and 0.39 to 2.95 % in the second growing season. Objective three was addressed in a growth chamber study. Willow cuttings were planted in pots and fertilized with 0, 50, 100 and 200 kg N ha-1 of granular ammonium nitrate and 100 kg N ha-1 of composted cattle manure. After a 90 day growth period shoot biomass production was significantly greater on the Prince Albert soil (1.28 to 5.34 g tree-1) than on the Saskatoon soil (1.18 to 3.59 g tree-1). No consistent trend between fertilizer treatments was observed. Further exploration into fertilization of willow SRWC systems should consider the application of multiple nutrient fertilizer blends, various rates and year of application to gain a better understanding of nutrient requirements of willow for the entire growth period.

The detrimental effects of climate change and the threat of diminishing fossil fuel reserves is forcing society to search for renewable sources of energy. Energy can be derived from the biomass of plant material by co-fire combustion with coal or on its own for the production of electricity. Energy can also be created by converting the plant biomass into ethanol, a gasoline substitute. When converted into bioenergy, plant biomass from Short Rotation Woody Crop (SRWC) systems has the potential to offset the use of fossil fuels if the yields can be maintained at profitable levels. The effect of first year application of nitrogen (N) fertilizer on willow biomass production in a SRWC system is not well understood. Using field and growth chamber studies, the objectives of this study were to 1) determine biomass production in the growing seasons following a single application of N fertilizer in the year of planting, 2) determine the N recovery for five willow clones using a 15N tracer, and 3) evaluate the effects of various types and rates of fertilizers on biomass production. Objectives 1 and 2 were addressed in a field fertilization study conducted on agricultural lands in the Moist Mixed Grassland ecozone and at tree nursery in the Boreal Transition ecozone. Willow cuttings were planted and fertilized with 100 kg N ha-1 of granular ammonium nitrate. Twelve trees were fertilized with 5 kg N ha-1 of double 15N-labeled ammonium nitrate and 95 kg N ha-1 of granular ammonium nitrate. In the first growing season trees were browsed to a uniform height making biomass measurements unrepresentative of production potential. Annual shoot biomass production in the second year, however, was 0.39 to 2.0 Mg ha-1 and was not found to be significantly different between fertilizer treatments. Nitrogen recovery by entire trees ranged from 2.87 to 10.6 % in the first growing season and 0.39 to 2.95 % in the second growing season. Objective three was addressed in a growth chamber study. Willow cuttings were planted in pots and fertilized with 0, 50, 100 and 200 kg N ha-1 of granular ammonium nitrate and 100 kg N ha-1 of composted cattle manure. After a 90 day growth period shoot biomass production was significantly greater on the Prince Albert soil (1.28 to 5.34 g tree-1) than on the Saskatoon soil (1.18 to 3.59 g tree-1). No consistent trend between fertilizer treatments was observed. Further exploration into fertilization of willow SRWC systems should consider the application of multiple nutrient fertilizer blends, various rates and year of application to gain a better understanding of nutrient requirements of willow for the entire growth period.

Willow bioengineering is an alternative erosion management technique that includes the use of living and inert willow material. It is successfully used across North America, Europe and Asia but, due to lack of public awareness of the technique or concerns about its effectiveness, it is currently used only occasionally in southern Manitoba. To provide insight into possible biological limitations upon the use of willows to prevent erosion a combination of field experiments and observational studies of new bioengineering sites was carried out across southern Manitoba. The results indicate that first year willow cutting survival is likely to be below 50% unless planted within 100cm of fall low water level. Using taller cuttings may improve survival as they develop greater numbers of shoots early in the growing season, but taller cuttings have a greater chance of being cut down or even pulled from the ground by beaver. Flooding had a negative effect of shoot numbers during the first year after planting, although it did not impact survival. In 2012 flood levels were lower at the majority of sites than the long term mean; more extensive flooding may have a more negative effect upon the cuttings. Maximum shoot length was reduced by high water levels, but was improved by cutting proximity to low water later in the summer. More research is needed to better understand the effect of high water levels on long term survival. Combining live willow with erosion blanket helps reduced substrate loss during establishment and also prevented willow bundles from being removed by beaver reducing the potential of project failure.

Thesis (M.S.)--University of Wisconsin--Madison, 1969. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Short rotation woody crops have gained global interest as an alternative energy source to fossil fuels. The availability of this resource is, however, dependent on successful research trials and the identification and quantification of the environmental controls on rapid growth. Knowledge of willow root dynamics is required to determine belowground and aboveground growth relationships, and to provide valuable inputs for the development of a willow carbon model. The objectives of this study were to 1) determine fine root turnover, biomass, and productivity of six willow clones over two growing seasons at four locations in Saskatchewan using the minirhizotron method; 2) determine fine root biomass and fine root carbon sequestration of six willow clones over one growing season at four locations in Saskatchewan using the soil coring method; and 3) determine lateral coarse root structure of six willow clones at two locations in Saskatchewan.<p> Monthly fine root biomass and production was estimated for six willow clones in Saskatoon, Saskatchewan using repeated minirhizotron observations from May to September of 2008 and 2009. Fine root biomass increased from 0.78 Mg ha-1 in May 2008 to 25.75 Mg ha-1 in September 2009. Significant differences were seen between months throughout each growing season, but not between the clones. Mean monthly productivity reached its peak of 8.00 Mg ha-1 in July 2009. Mean turnover for all the clones was 0.96 yr-1 and mean longevity was 1.04 yr-1. The high fine root biomass estimates determined by the minirhizotron method in Saskatoon suggest that this method is not suitable for use in a Vertisolic soil. There was no significant effect of clone on fine root productivity, biomass, turnover or longevity (P < 0.05).<p> Fine root biomass estimates from the soil cores were lower than those from the minirhizotron method. The mean fine root biomass value in Saskatoon for September 2008 was 0.298 Mg ha-1. Mean fine root biomass at each site from September 2007 to September 2008 ranged from 0.022 Mg ha-1 to 0.915 Mg ha-1. Mean root carbon content ranged from 0.010 to 0.426 Mg C ha-1. Fine root biomass and root carbon content were significantly different between each site, with the exception of Saskatoon and Estevan (P < 0.05). Differences in fine root estimates between the sites are suggested to be a function of the soil texture and moisture accessibility at each site. This research indicates that willow roots in Saskatchewan find initial establishment difficult in low moisture, fine textured soils. Also, approximately 44.6 % of fine root biomass is comprised of C, and decomposes to form soil organic matter. Therefore, fine roots have potential to store substantial amounts of carbon if growing conditions are suitable.

Short rotation woody crops have gained global interest as an alternative energy source to fossil fuels. The availability of this resource is, however, dependent on successful research trials and the identification and quantification of the environmental controls on rapid growth. Knowledge of willow root dynamics is required to determine belowground and aboveground growth relationships, and to provide valuable inputs for the development of a willow carbon model. The objectives of this study were to 1) determine fine root turnover, biomass, and productivity of six willow clones over two growing seasons at four locations in Saskatchewan using the minirhizotron method; 2) determine fine root biomass and fine root carbon sequestration of six willow clones over one growing season at four locations in Saskatchewan using the soil coring method; and 3) determine lateral coarse root structure of six willow clones at two locations in Saskatchewan.<p> Monthly fine root biomass and production was estimated for six willow clones in Saskatoon, Saskatchewan using repeated minirhizotron observations from May to September of 2008 and 2009. Fine root biomass increased from 0.78 Mg ha-1 in May 2008 to 25.75 Mg ha-1 in September 2009. Significant differences were seen between months throughout each growing season, but not between the clones. Mean monthly productivity reached its peak of 8.00 Mg ha-1 in July 2009. Mean turnover for all the clones was 0.96 yr-1 and mean longevity was 1.04 yr-1. The high fine root biomass estimates determined by the minirhizotron method in Saskatoon suggest that this method is not suitable for use in a Vertisolic soil. There was no significant effect of clone on fine root productivity, biomass, turnover or longevity (P < 0.05).<p> Fine root biomass estimates from the soil cores were lower than those from the minirhizotron method. The mean fine root biomass value in Saskatoon for September 2008 was 0.298 Mg ha-1. Mean fine root biomass at each site from September 2007 to September 2008 ranged from 0.022 Mg ha-1 to 0.915 Mg ha-1. Mean root carbon content ranged from 0.010 to 0.426 Mg C ha-1. Fine root biomass and root carbon content were significantly different between each site, with the exception of Saskatoon and Estevan (P < 0.05). Differences in fine root estimates between the sites are suggested to be a function of the soil texture and moisture accessibility at each site. This research indicates that willow roots in Saskatchewan find initial establishment difficult in low moisture, fine textured soils. Also, approximately 44.6 % of fine root biomass is comprised of C, and decomposes to form soil organic matter. Therefore, fine roots have potential to store substantial amounts of carbon if growing conditions are suitable.

Thesis (M.S.)--Montana State University--Bozeman, 2005. / Title from PDF t.p. (viewed on June 10, 2006). Chairperson, Graduate Committee: Richard J. Aspinall. Includes bibliographical references (p. 93-105).

No description available.

Continuous measurements of the energy and radiation balance were made during the 1991 growing season over a dwarf willow-birch forest located near Churchill, Manitoba. The ecological setting is described in terms of both the nature of the substrate and the morphology and distribution of the plant species. Intensive measurements of stomatal conductance and xylem pressure potential for several species were taken on three fair weather days. These represented a wide range of air temperatures and leaf-to-air vapour pressure deficits and allowed the quantification of the surface-atmosphere interactions. The very dynamic and important role of the vegetation in the evaporative process is illustrated. The willow-birch forest consists of six main species which have colonized the recently emerged coastline. There is a wide range in the plant height, rooting networks, and above-to-below ground plant mass. A mature leaf area index of 0.81 m^2 m^-2 was reached within 15 days after the onset of growth. The substrate consists of a 20 cm moderately saline organic layer situated on top of sand. Soil moisture was high, with at least some of the roots of all plants residing within the saturated zone throughout the growing season. The influence of the vegetation on both the radiation and energy balance is illustrated by partitioning the growing season into growth, mature and senescence periods. A strong relationship between surface albedo and vegetation growth indicates that the canopy is more effective in reflecting than in trapping radiation. As the canopy matures, the addition of transpiration to the overall evaporation dramatically increases the magnitude of the latent heat flux at the expense of the sensible heat flux. A sensitivity analysis indicates that evaporation is highly sensitive to the canopy resistance. The sensitivity of evaporation to canopy resistance, in turn, is a function of the ratio of canopy-to-aerodynamic resistance. Strong seasonal and diurnal trends are shown in the sensitivity of evaporation to net radiation, canopy resistance, and aerodynamic resistance. Diurnal stomatal conductance measurements indicate that some species show a pronounced midday stomatal closure. A conceptual model is developed which attributes this behaviour to differences in the sensitivities to the leaf-to-air vapour pressure deficit. A non-linear boundary line analysis of stomatal conductance indicates species-specific responses to irradiance, air temperature, leaf-to-air vapour pressure deficit, and xylem pressure potential. The results of the boundary line analysis are coupled with a modified version of the Penman-Monteith combination model. The model predicts evaporation accurately when the canopy is mature, and indicates that 80% of the evaporation originates from the plants (transpiration). The model is used to examine the potential effects of species composition and climate change on evaporation. This illustrates the important and variable role that vegetation can play in determining responses to climate change. / Thesis / Master of Science (MSc)