Recent geomorphic and hydrologic environments of a mid-latitude alpine basin are investigated under the integrative theme of paleohydrology. The aims of this research are: 1) to characterize the response of selected biological and geophysical elements to recent climatic change; 2) to determine the resolution and length of paleoenvironmental records in the study area; and 3) to ascertain the significance of observed and inferred environmental change over the Little Ice Age interval. Bella Coola River drains 5050 km² of glacierized mountains along the central coast of British Columbia. Biological elements examined on a basin-wide scale included: tree-growth in temperature and moisture-stressed environments, damage to trees in glacial and fluvial settings, pollen variations in a variety of sedimentary deposits and soil development. Geophysical elements include primarily glacio-lacustrine and floodplain sediments, glacier deposits and river channel morphology. A retrospective strategy was adopted by testing initially for the nature of relationships between synoptic climate, basin hydrology and element response during the period of instrument record (1900 AD to present). Inferences about pre-instrument environments were then made using the proxy data. Events of several types are characteristically mixed in a response record. Variations in Douglas and subalpine fir growth, glacio-lacustrine sedimentation rates, glacier fluctuations and shifting of the Bella Coola River reflect a combination of persistent and episodically extreme behavior. Glaciers appear to respond by advancing or retreating after departures in winter precipitation persistent for several years. Extreme events, particularly high-magnitude autumn floods, are not exclusively linked to a particular set of mean climatic departures. This makes inferences from proxy data such as floodplain deposits and flood-damaged vegetation difficult. Periods of increased flood frequency are supposed to relate to an increase in floodplain sedimentation. Except in very favorable circumstances, paleoenvironmental methods do not have the resolution promised. Climatic information recoverable from tree-ring data and glacio-lacustrine sediments is of considerably lower than annual resolution. Statistically based climate models using proxy data as independent variables produce low levels of explained variance. Proxy data sources in the basin were largely restricted to the last 300 to 4OO years or Little Ice Age interval. Most glaciers in the basin reached Little Ice Age maxima in the middle of the 19th century in response to below average temperatures and above average precipitation between approximately 1800 and 1855 AD. Tree-ring data and equilibrium line altitudes on glaciers indicate that precipitation was on average 25 to 30% greater than the 1951-1980 mean. Inferred below average temperatures in the early l8th century probably signaled the beginning of the Little Ice Age along the central coast; however, there was not a major response in glaciers until persistent positive departures in precipitation occurred. Recession of glaciers from Little Ice Age maxima was slowed by cooler and wetter conditions between I885 and 1900 AD. The persistence of warmer and drier conditions in the first half of the 20th century was exceptional in comparison with inferred climate of the last 330 years. Major floods in 1805/06, 1826, 1885 and 1896 correspond to intervals of increased precipitation. / Arts, Faculty of / Geography, Department of / Graduate

Pythium undulatum var. litorale Hohnk was found to infect Fucus distichus in the Squamish River estuary of southern British Columbia. This thesis adresses the questions of: 1.) whether this symbiosis can be found outside the Squamish River estuary, 2.) relationship of the infection within the estuary to the distribution of P. undulatum var. litorale in estuarine sediments, 3.) taxonomically defining those species associated with Fucus and/or in estuarine sediments, and 4.) the host parasite relationship as determined by means of histochemical and light microscope observations. Results indicated that outside the Squamish River estuary, associations between pythiaceous fungi and Fucus are uncommon in British Columbia coastal areas. Sampling of live and decaying Fucus plants from 10 field stations in British Columbia and Washington yielded only 4 species, the most common isolate being Phytophthora vesicula. Within the Squamish estuary, an association was found to exist between the distribution of P. undulatum var. 1itorale in the sediments and the distribution of infected Fucus plants. Sediment sampling from the Fraser River estuary, where Fucus does not occur, yielded P. undulatum var. litorale, suggesting that the fungus is probably indigenous to estuarine sediments. Numerous other species of Pythium were recovered from estuarine sediments, including P. butler i, P. carolinianum, P. catenulatum, P. gracile, P. torulosum , and P. volutum . Two taxa are described in detail. Pythium undulatum var. litorale was originally described by Hohnk (1953), but the varietal status was rejected by Waterhouse (1967). Arguments are presented for retention of the variety. Pythiogeten utriforme Minden is transferred to the genus Pythium and P. hohnkii is proposed as the nomen nova of this taxon. A discussion of the generic characteristics of the genus Pythiogeten is presented. In order to facilitate an understanding of the infection process by Pythium species, the anatomy and histochemistry of Fucus distichus were examined. Anatomically, F. distichus agrees with earlier reports of other species of Fucus. The internal structure of cells was found to agree with descriptions in earlier publications, although higher physode content was noted in F. distichus. Histochemical staining suggested that cell walls of Fucus are three layered; having an outer fucan-rich layer, a middle layer composed principally of alginic acid, and an innermost layer of cellulose. Several phenolic-indicating reagents were tested on both fresh and fixed/embedded Fucus tissue, resulting in some interesting new observations of phenolics in the matrix. The host-parasite interface of P. undulatum var. 1itorale and F. distichus was also examined by use of histochemistry and the light microscope. Macroscopically, the infection of F. distichus occurs behind the most recent dichotomy, and lesions are necrotic, firm (flaccid with age), and are pink-to-red in color. Microscopically, fungal hyphae are confined to the cortical and medullary regions. Hyphae appear to penetrate host cell walls by means of an enzymatic dissolution of the alginic acid and cellulosic portions of the cell wall. Use of the Periodic Acid/Schiff's reagent shows a distinct non-staining halo at the point where hyphae cross the cell wall. Pit connections between cortical cells were observed to break down with hyphae present in only one cell, suggesting that the fungus is capable of parasitizing several cells via digestion of pits. Gemmae were observed to form in both cortical and medullary cells. The response by Fucus to infection is an active one; a hypersensitivity reaction analagous to that of higher plants is observed. Cells in advance of fungal hyphae are observed to autolyse. Normally metabolically quiescent medullary filaments are observed to have an increase in general protein levels and to have increased physode content. Physodes become polarized within the medullary cells, and coalesce to form larger units, which are then delimited from the producing cell by a cross wall. The fate of these 'giant' physodes was not observed, but it is believed that these cells autolyse and release their phenolic contents to the matrix, as levels of phenolic-reactive material were observed to increase in this region. Coupled with the buildup,of phenolics in the matrix is a decrease in the fucan component of the matrix. Stress and tear lines appear between cells, and eventually this region serves as an abscission zone by which the infected portions are dropped out of the plant. Behind the abscission zone, medullary filaments undergo transverse divisions to form irregular, cuboidal cells which function as epidermis after abscission of the lesion occurs. / Science, Faculty of / Botany, Department of / Graduate