The projected increase of shrubs across the Arctic is expected to alter patterns of snow cover, which may affect the phenology and survival of arthropods such as spiders. In this study, we simulated shrub encroachment on a series of tundra plots and examined the effects on the spider assemblages during the following growing season. Our simulated shrub treatment did not affect the abundance or composition of spider communities over the season; however, adults from the dominant genus Pardosa (Lycosidae) had significantly higher body mass on treatment plots. This difference in mass was observed following snow melt and persisted until halfway through the growing season. Given the importance of spiders as arthropod predators and as food sources for breeding birds, such a change in summer body mass could represent a shift in spiders’ functional contributions to Arctic ecosystems.

Most studies of under-bark microclimate have been restricted to observations of a few coniferous trees in wooded southern latitudes. This limitation is worrying because of emerging wood-boring pests that specialize on deciduous trees in Canada, such as emerald ash borer (Agrilus planipennis). Using a large data set that includes 60 ash trees spread across both urban and woodlot sites in 6 different Ontario locations, I found that the under-bark microclimate of deciduous trees can provide wood-boring beetles with an environment in which temperatures which differ from air temperature. On average, daily minimum under-bark temperatures are significantly warmer than air temperatures in the winter months. At temperatures low enough to cause substantial cold-temperature mortality to emerald ash borer, the difference between under-bark and air temperature can be large. In addition, I observed that the difference between daily minimum under-bark and air temperature can vary, and consequently that assumptions of a constant level of difference between the two are not valid. In the spring season, I found that daily under-bark temperature maxima on the south side of the tree are significantly warmer than air temperature maxima. This difference lead to faster predicted development times for beetles in the southern under-bark microclimate of urban trees as compared to predictions based on air temperature, suggesting that city trees may impact overall population dynamics. While it is clear that under-bark temperatures differ from air temperatures, and are important to predicting possible range and population growth of wood-boring insects, large scale measurements of microclimate conditions are not feasible. I tested the ability of a simple Newtonian cooling model to predict under-bark temperature extremes using weather station data. While the model did not predict daily under-bark temperature maxima accurately, predictions of minima were quite accurate (1.31˚C average root mean squared error), especially when compared to the errors from assuming under-bark temperature is the same as air temperature (3.20˚C average root mean squared error). I recommend use of the Newtonian cooling model to predict under-bark temperature minima of deciduous and coniferous trees.

A study was conducted to examine the impact of diet and cold weather on the excretion of nitrogen (N) and phosphorus (P) from beef cows, and the potential for these nutrients to be lost to waterways or as greenhouse gases (GHG). Feces and urine were collected from mature cows fed low-quality forage supplemented with DDGS to 0%, 10%, and 20% ww-1 in the fall of 2008 and winter of 2009. A detailed nutrient analysis was performed to determine forms of N and fractions of P in excreta. Feces, urine, and a simulated bedding pack were then applied to grassland to determine soil GHG emission. Cattle receiving DDGS supplementation excreted greater proportions of labile P in feces and greater concentrations of P in urine. The 20% DDGS diets had greater nitrous oxide emission from urine patches and greater proportions of available N in urine and feces.

A study was conducted to examine the impact of diet and cold weather on the excretion of nitrogen (N) and phosphorus (P) from beef cows, and the potential for these nutrients to be lost to waterways or as greenhouse gases (GHG). Feces and urine were collected from mature cows fed low-quality forage supplemented with DDGS to 0%, 10%, and 20% ww-1 in the fall of 2008 and winter of 2009. A detailed nutrient analysis was performed to determine forms of N and fractions of P in excreta. Feces, urine, and a simulated bedding pack were then applied to grassland to determine soil GHG emission. Cattle receiving DDGS supplementation excreted greater proportions of labile P in feces and greater concentrations of P in urine. The 20% DDGS diets had greater nitrous oxide emission from urine patches and greater proportions of available N in urine and feces.

Most studies of under-bark microclimate have been restricted to observations of a few coniferous trees in wooded southern latitudes. This limitation is worrying because of emerging wood-boring pests that specialize on deciduous trees in Canada, such as emerald ash borer (Agrilus planipennis). Using a large data set that includes 60 ash trees spread across both urban and woodlot sites in 6 different Ontario locations, I found that the under-bark microclimate of deciduous trees can provide wood-boring beetles with an environment in which temperatures which differ from air temperature. On average, daily minimum under-bark temperatures are significantly warmer than air temperatures in the winter months. At temperatures low enough to cause substantial cold-temperature mortality to emerald ash borer, the difference between under-bark and air temperature can be large. In addition, I observed that the difference between daily minimum under-bark and air temperature can vary, and consequently that assumptions of a constant level of difference between the two are not valid. In the spring season, I found that daily under-bark temperature maxima on the south side of the tree are significantly warmer than air temperature maxima. This difference lead to faster predicted development times for beetles in the southern under-bark microclimate of urban trees as compared to predictions based on air temperature, suggesting that city trees may impact overall population dynamics. While it is clear that under-bark temperatures differ from air temperatures, and are important to predicting possible range and population growth of wood-boring insects, large scale measurements of microclimate conditions are not feasible. I tested the ability of a simple Newtonian cooling model to predict under-bark temperature extremes using weather station data. While the model did not predict daily under-bark temperature maxima accurately, predictions of minima were quite accurate (1.31˚C average root mean squared error), especially when compared to the errors from assuming under-bark temperature is the same as air temperature (3.20˚C average root mean squared error). I recommend use of the Newtonian cooling model to predict under-bark temperature minima of deciduous and coniferous trees.

The thesis describes the development and survival of immature Ips typographus specimens at low temperatures under laboratory and field conditions. Further, the focus was identifying and characterizing the digestive enzymes present in the gut of adult I. typographus, their location in the gut and enzymatic fluctuation over a full calendar year, with a specific focus on digestion of cellulose.

The impact of outdoor cattle overwintering husbandry on soil fungal community at upland pastures was investigated. Soils with different intensity of cattle impact were surveyed and the fungal communities were studied by combination of culture-dependent and culture-independent microbiological methods. These analyses showed the substantial shift in biomass, functions, and species composition of fungal communities caused by cattle overwintering.

The long-term cattle impact on soil methanotrophs was investigated at cattle overwintering area located at the ecofarm in the South Bohemia. Four sets of soil samples were sampled in spring and fall of 2009 and 2010. Differences in methanotrophic community structure among experimental sites and were investigated by DGGE and MISA. Real-Time PCR was used for estimation of quantity of Type I methanotrophs. The CARD-FISH method was used to estimate the percentage shared and cell counts of Type I and Type II methanotrophs among all prokaryotic cells. Substantial part of the thesis was focused on optimization of methods used.

A study was conducted during the period May to September, 1999 to determine the effect of phosphorus (P) supplementation to beef weaners grazing kikuyu (Pennisetum clandestinum) foggage during winter followed by hay towards the end of winter at Dundee in northern KwaZulu-Natal. Foggaging is defined as the practice of allowing herbage to accumulate on a pasture during the growing season (Gertenbach, 1998). This accumulated herbage is then utilized by grazing animals during the dormant season. A total of 200 crossbred beef weaners (average age six months and average weight 175 kg) was used in the trial. Animals were randomly allocated into five groups, each receiving a different supplemental treatment. The treatments were different levels of P supplementation, administered through free-choice P lick supplements, viz. at levels of 0 g P, 2 g P, 4 g P, 6 g P and 8 g P per animal per day. The experiment was divided into two phases. During the first phase (08-06-99 to 20-07-99) the weaners grazed kikuyu foggage and during the second phase (05-08-99 to 16-09-99) they received Smutsfinger(Digitaria eriantha) hay ad libitum. During phase 1 the average weight gain of the animals in Group 1 (receiving 8 g P/animal/day) was significant higher (6 kg/animal during trial) than that of the control group, which received 0 g P/day/animal. Phase 2 which represented a transition from winter to summer showed that Group 1 had an average weight loss of 0.88 kg/animal but the control group lost an average of 5.13 kg/animal. Throughout the trial blood was collected from five animals randomly selected from each group. Plasma inorganic P (Pi) concentrations remained between 1.94 and 2.58 mmol/L. The average trend during phase 1 was that the Pi concentrations increased, while during phase 2, Pi concentrations dropped more (P ¡Ü 0.5) in the animals of Group 1 (8 g P/animal/day) than in the control. This resulted that during the entire experimental period plasma Pi in Group 5 increased while that in Group 1 decreased. Before the animals entered a grazing strip, herbage samples were collected at 14 to 20 day intervals from the five strip grazed kikuyu camps. Samples were divided into leaves and stems which were analysed separately. Mean foggage calcium (Ca) and P concentrations ranged from 25.0 to 29.0 g/kg DM and 20.0 to 27.0 g/kg DM, respectively, while the Ca:P ratios ranged from 1.20:1 to 1.60:1. Calcium concentrations were significantly lower (P = 0.0026) in the stems than in the leaves of the kikuyu foggage, while P concentrations decreased significantly over time, resulting in extremely low foggage P concentrations towards the end of the grazing season. This decrease in P concentrations resulted in Ca:P ratios of above 1:1 instead of the reported ratios of below 1:1 in kikuyu herbage due to low herbage Ca concentrations. The Ca concentrations in the kikuyu in this study were in the same range as herbage concentrations reported in the literature, but P concentrations were much lower than the reported herbage P concentrations. As with the summer pastures we found that magnesium (Mg) concentrations (ranging from 2.1 to 2.6 g/kg DM) were adequate in terms of the requirements of most classes of ruminants. However, potassium (K) concentrations (ranging from 11.4 to 20.3 g/kg DM) were well in excess of animal requirements, and Mg absorption could be severely inhibited by the oversupply of K The sodium (Na) concentration in kikuyu foggage was, as with herbage, inadequate in terms of animal requirements. Zinc (Zn) and manganese (Mn) concentrations were well above animal requirements but below toxic levels. Copper (Cu) concentrations was above animal requirements during May (onset of the study) but decreased significantly to levels below minimum animal requirements. Selenium (Se) concentrations were found to be largely inadequate in terms of animal requirements. The neutral detergent fibre (NDF) levels in kikuyu foggage tended to increase with maturity while acid detergent fibre (ADF) levels did not vary significantly. Crude protein (CP) concentrations decreased as winter progressed to reach levels of < 60 g/kg DM in the dry foggage, indicating that supplementation of CP would be required by animals grazing the kikuyu foggage in mid-winter. It is concluded that if little or no gain is expected from weaners in winter, the Ca and P concentrations in the kikuyu foggage should be adequate. However, if even slight weight gains are required, supplementation of Ca and P would be necessary when the foggage is dry. The P and CP composition of pastures in general were closely correlated and had a seasonal pattern with maximum levels during summer and minimum levels during winter. We can therefore expect that pastures and kikuyu foggage low on protein will also have a P deficiency. In the dry winter we should therefore firstly supplement for protein and energy and then P. The supplementation of P during winter has not only been very positive (in other studies) with positive results on weight gain during the winter period but also during the months thereafter. It is concluded that beef weaners grazing kikuyu foggage in northern KwaZulu-Natal would require supplemental P to maintain their body weights during winter as well as beef weaners on Smutsfinger hay. The recommended level of P supplementation is 8 g P/animal/day. / Dissertation (MSc (Animal Science))--University of Pretoria, 2007. / Animal and Wildlife Sciences / unrestricted

Neonatal painted turtles (Chrysemys picta) spend their first winter inside the shallow, subterranean nest cavity where they completed embryogenesis. Consequently, hatchlings at high latitudes may be exposed to ice and cold during the winter. This study was undertaken to determine how long hatchlings withstand freezing at temperatures slightly below 0°C because tolerance for freezing has been proposed to be the key to survival by overwintering animals. A thermocouple was glued to the carapace of each hatchling. The animal was dipped in water to provide a site of nucleation of ice and was then placed into a glass jar that was partially immersed in a circulating bath at -2°C. Carapace temperature was monitored throughout the procedure. When a freezing exotherm was detected, timing of the freezing event began. Animals were maintained in a frozen state for 12-48 h prior to being warmed to room temperature. Of the 39 hatchlings, 22 did not survive, and mortality increased as the duration of freezing increased. Logistic regression indicates that no turtle would have survived in a frozen state for more than 54 h. These results indicate that hatchlings can survive only brief exposure to freezing of the body fluids. Thus, hatchlings cannot tolerate freezing during prolonged periods of cold.