京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第19027号 / 農博第2105号 / 新制||農||1030(附属図書館) / 学位論文||H27||N4909(農学部図書室) / 31978 / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 大澤 晃, 教授 髙部 圭司, 教授 北島 薫 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Doctor of Philosophy / Department of Agronomy / Johanna A. Dille / Challenges in weed management include occurrence of multiple weed species in the field, variable emergence among weed species, different spatial distribution and weed densities, which leads to the persistence of weed patches. The overall objective of this research was to understand the interaction of weed emergence, weed density, herbicide choice, and herbicide rate in soybean. Specific objectives were 1) to characterize the seedbank and emergence patterns of shattercane (Sorghum bicolor L.), prickly sida (Sida spinosa L.), and ivyleaf morningglory (Ipomoea hederacea Jacq.) including initial, peak, end, and duration of emergence in response to crop and herbicide treatments in soybean, and 2) to evaluate large crabgrass (Digitaria sanguinalis L.), shattercane, Palmer amaranth (Amaranthus palmeri S.), and velvetleaf (Abutilon theophrasti Medik.) mortality and dry weight reduction in response to herbicide rates across varying weed densities as well as to determine the influence of velvetleaf growth stage and density on herbicide efficacy. In the emergence study of 2006 to 2008, four treatments were nocrop, no-residual herbicide, half-rate of residual herbicide and full-rate of residual herbicide. Reduction in weed emergence was observed over the years in the same species patch. Species emerged in mid-May in both years, coinciding with soybean planting. Extended emergence was observed for shattercane when moisture was low and temperature high, while for prickly sida and ivyleaf morningglory, extended emergence was observed when moisture was high and temperature low. Applying residual herbicide decreased weed emergence. Herbicide choice was the whole plot, herbicide rates were subplots and weed densities were sub-subplots in field experiments conducted in 2006 and 2007. Shattercane was more susceptible to both glyphosate and clethodim than large crabgrass. Increasing large crabgrass density reduced percent mortality with clethodim, while with glyphosate, density did not affect both species mortality. Shattercane dry weight was reduced to 0 g per plot with 0.1X labeled rate of clethodim or glyphosate while 0.5X of the labeled rate reduced dry weight of large crabgrass to 0 g per plot. For broadleaf weeds, higher percent mortality was observed with glyphosate than with lactofen at high densities. Palmer amaranth was more susceptible than velvetleaf. Velvetleaf response was density dependent, such that increasing density did not increase dry weight. Velvetleaf growth stage was of importance, as stage affected herbicide efficacy, with higher mortality achieved at the two-leaf stage than the four- and six-leaf stages. For glyphosate, 0.125X of labeled rate on velvetleaf density of 5 seedlings per pot achieved more than 90% mortality when applied at the two-leaf stage, but dropped to 60 and 50% mortality when applied at the four- and six-leaf stage, respectively. The trend was the same for velvetleaf at a density of 30 seedlings per pot, which had 80, 60, and 55% mortality for the two-, four-, and six-leaf stages, respectively. Weed managers and farmers have the opportunity to better select herbicide choice and rate based on weed species, weed emergence patterns, and weed density.

This thesis deals with important factors that affect the temporal organization of emergence and early survival of Baltic salmon (Salmo salar L.). The study population was obtained from the Norrfors hatchery (63°50'N,20°05'E), Umeälven (Ume river) in Northern Sweden. The main objectives of the thesis has been to study; a: the effect of female and egg characteristics on embryonic survival, b: the effect of egg size, temperature and photoperiod on the emergence pattern and c: the impact of early or late emergence on survival in relation to predation and limited territorial space. The main results are summarized as follows: (1) Fecundity and egg size increased with increasing weight of females. No effect of female size were found on egg colour. Longer impoundment and later stripping increase egg colour. Egg mortality was not correlated with egg colour. Stripping date was found to have the strongest effect on mortality. (2) Egg size had no effect on the timing of emergence but fry of different egg size emerged synchronously. Fry from large eggs left the gravel as heavier fry and with a larger proportion of yolk left compared to fry from small eggs. (3) The number of days and number of degree days from hatching to 50% emergence decreased exponentially with increasing temperature. Synchronization of emergence increased with increasing temperature. Fry emerged with more yolk at 12 °C compared to 6 °C. (4) Eggs kept in a LD 16:8 light regime hatched mainly during the light period, while eggs kept in constant darkness hatched continously over a 24 hour period. Alevins kept at different light regimes (light>4h) from hatching until emergence left the gravel during the dark period. Daylength had no effect on the annual onset of emergence. (5) In a laboratory stream channel, predator presence at emergence increased mortality especially in early emerging fry. If the predator was introduced after completed emergence high mortality was noted among late emerging fry. The presence of fish predators and a limited territorial space for fry seemed to make early and late emergence hazardous and to favour a "peak" emergence. In the presence of a predator the fry changed their behaviour by reducing their swimming activity. / digitalisering@umu.se