Akademisk avhandling--Uppsala. / Bibliography in "Viktigare förkortningar" (p. [xi]-xv) Bibliographical footnotes.

Thesis--Zürich. / Cover title. Vita. Includes bibliographical references (p. [vii]-ix) and index.

Inaug.--diss.--Münster i.W. / Cover title. Lebenslauf. Literatur-angabe: p. [3]-8.

Thesis--Uppsala. / Bibliography: p. [108]-110.

Afhandling--Copenhagen.

Thesis--Copenhagen. / "Kilde-og litteraturforkortelser": p. [9]-13.

This thesis is concerned with analysing the interactions between smallholder sheep farming systems and the sustained maintenance of communal grazing resources in the temperate region of Mexico. The study was carried out in the parish of Coajomulco, which is located in the mountainous region south of Mexico City. Sheep production is a traditional agricultural activity in the region and extensive grazing is practised in the parish's communal forest. In 1988 the area was decreed as protected by the Ministry of Environment, and agricultural practices were highly regulated. Although sheep flocks could still have access to the forest, the establishment of an exclusion zone resulted in the inability of sheep farmers to make use of 48 % of the communal grazing area. Thus, the objectives of this thesis were concerned with finding a way of enhancing the development of the local smallholder sheep farming whilst concomitantly protecting the forest ecology. The ultimate objective of this thesis was to develop a spatial optimisation model for the grazing management of the communal land. This model produced the optimal distribution of flocks in time and space according to the characteristics of both the grazing resources and the sheep population. Prior to the development of the optimisation model, it was necessary to characterise the basic elements that affected the supply and demand of forage. Thus, under a farming systems research framework, the plant and animal elements of the farming system were characterised. The managerial and biological influences that defined the sheep grazing patterns were investigated and their resulting effects discussed. Participatory techniques were included as the core of the characterisation methodology. Findings derived from the characterisation were utilised to assist in the development of a geographical information system (GIS) and the application of biological simulation models. Two models, one that simulated flock dynamics and another that simulated sheep performance, were used. Subsequently, a two-way link was established between the simulation models, the GIS and the optimisation model.

Monte Carlo simulations are used to investigate the conformational and orierjtational properties of lipids and proteins in a bilayer membrane. in the first instance, linear, hard-core tri-atomics are used to represent the two-dimensional projections of the lipid molecules. Studies on lipid only systems show that the average number of gauche rotations and the cross-sectional area of the lipids decrease with increasing density. There is no long range orientational order within the lipids but the local orieritational order increases with increasing density. No first order phase transitions are observed though a glassy solid is observed at high densities. The properties of the bulk lipid are unchanged upon the addition of protein molecules represented by hard discs of varying sizes. The nearest neighbour lipids are unchanged conformationally but are found to exhibit a high degree of orientational ordering around the proteins preferring to have the long axis of their projections parallel to the proteins surface. The degree of ordering increases with increas-ing density and decreasing curvature of the protein. The lateral pressure is almost independent of protein size or concentration if expressed as a function of the bulk lipid density. The hard-core of the lipids is softened to a site-site Lennard-Jones potential. The particles are found to cluster within the periodic cell used. There is a critical density below which the average number of gauche rotations and the cross-sectional area change little and the local orientational order increases. Above this density these properties are the same as for the hard-core systems. The structure, indicated by the radial distribution functions, is much greater than that for the hard-core systems and is almost independent of density. The invariance of the lipid conformations and the observed lipid-protein orientational order resolve the conflict that has arisen in the past regarding the presence or absence of an annulus of lipid around integral protein molecules. The different experimental methods are seen to examine different lipid properties.

I studied the dispersion of winter wrens in 100-year-old, second-growth, coastal western hemlock forest at the University of British Columbia Research Forest in southwestern British Columbia from 1978-81. Male winter wrens were territorial on non-overlapping territories at an average density of 60 per km2. An average of 8% were polygamous. Females occupied generally non-overlapping home ranges at least during the breeding period, but were not shown territorial, although this possibility could not be excluded. Winter wrens were not uniformly distributed but showed differential use of various individual ecosystems (as mapped by Klinka 1976) and ecosystems grouped by forest floor habitats. Surplus, potentially territorial males were available during the breeding period which could have occupied the empty or sparsely occupied areas. Invertebrate food was more abundant in habitats used by winter wrens as compared to avoided habitats, and, food is proposed as a factor in habitat selection by winter wrens. I propose that winter wrens are spaced by territoriality and clumped by suitable habitat, and suggest that these two factors influence the patterns of dispersion of winter wrens in coastal western hemlock forest, and perhaps elsewhere as well. Klinka's ecosystems and grouped ecosystems were proposed as indicative of the distribution of winter wrens, and perhaps of other wildlife species generally. If so, ecosystems can arid should be used as the base for the study and management of wildlife in the province of British Columbia, and perhaps elsewhere as well. / Forestry, Faculty of / Graduate

If spacing behaviour of snowshoe hares limits juvenile survival and recruitment during summer, removal of this behaviour should produce an increase in these parameters. During the summers of 1980 and 1981 I removed all adults from an 8 ha trapping grid and all first litter juveniles from another. Experiments were conducted in the southwestern Yukon during a period when hare populations were at peak densities. The experimental removals did not increase survival, but recruitment relative to control areas was higher to the adult removal grid in 1980 and to both the adult removal and juvenile removal grids in 1981. To determine whether juveniles trapped for the first time were residents or immigrants, I implanted adult females with, calcium-45. This was passed to nursing young and could be detected by scintillation counting of a sample of bone tissue taken from new recruits. Any juvenile without radioactive calcium was classed as an immigrant. The increase in recruitment on the removal areas was due to increased immigration. The number of resident recruits was equal on all study areas. Results support the hypothesis that spacing behaviour limits juvenile immigration but not survival. However, immigration to control areas was also high with immigrants making up 70% of the total number of juveniles present on the areas in October. If food limits snowshoe hare numbers, addition of food should lead to increased numbers through higher survival and immigration. If food supply influences spacing behaviour of hares, home range size should decrease with food addition. I supplied peak (1980) and declining (1981) hare populations on 8 ha grids (one in 1980 and 2 in 1981) with laboratory rabbit chow for 1 - 4 months during March through June. Population size was determined by live-trapping and movements of animals were monitored by radio telemetry. Food addition decreased weight loss and improved survival of hares in both years. Onset of breeding was advanced in males but not females. In 1980, the number of males on the food addition area was 1.4 times higher than those on the control area while the number of females did not differ. In 1981, numbers of males and females were up to 3.6 and 3.2 times higher respectively on the food addition area as compared to those on ;the control area. The differences were due mainly to increased immigration. Residents responded to food addition by decreasing home range size in 1980 but not in 1981. Movement of immigrants, as monitored by telemetry, to the food addition area indicated that some established home ranges there while others returned to their old home ranges. Results support the hypothesis that hare densities are limited by winter food supply during the early decline phase of the cycle and possibly during the peak phase as well. A decrease in home range size was not necessary for immigration to occur. To examine the relationship of dispersal to changes in snowshoe hare numbers, I monitored dispersal of hares during a population increase, peak, and early decline (1978-1982). Two methods were used: 1) a conventional removal grid in which all animals caught each trapping session were removed and 2) telemetry monitoring of radio-collared individuals. The number of animals caught on the removal area was correlated with density on the control area but per capita dispersal rate was not. Both the number of dispersers and the per capita dispersal rate were highest during the period of peak densities on the control area. Dispersal, as measured by the removal grid, was not density dependent. Only 23 of 265 radio-collared animals dispersed during the study. Dispersal accounted for an average of 11% of the losses of radio-collared animals during the population decline. Results from both telemetry and the removal grid indicated that the decline in hare numbers was not due to dispersal. The amount of dispersal as determined by the removal grid was much higher than that determined by telemetry. The difference was more pronounced during the population peak and early decline. This was due to the removal grid over-estimating the average amount of dispersal that was occurring because it attracted animals to it. These results point to the need to be more critical of the underlying assumptions of the removal grid method as a way of monitoring dispersal. / Science, Faculty of / Zoology, Department of / Graduate