Thesis (M.A.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains v, 32 p. : ill. (some col.), maps Includes abstract. Includes bibliographical references (p. 31-32).

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 23, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. John J. Bowders, P.E. Includes bibliographical references.

Thesis (M.F.)--Oregon State College. / Includes bibliographical references (leaves 107-109). Also available on the World Wide Web.

Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains x, 173 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 163-169).

Thesis (M.A.)--Carleton University, 1988. / Also available in electronic format on the Internet.

The objective of this study was to describe the dynamics of post-clearcutting forest floor N on mesic sites in the wet subzone of the Coastal Western Hemlock biogeoclimatic zone. Post-clearcutting release of N was examined by measuring the following parameters for a chronosequence of five sites ranging in age from an old-growth forest to a 26-yr-old stand: forest floor N capital; rate of in situ mineralization of forest floor; rate of decomposition of cellulose; concentrations of inorganic-N and total-N in soil solution; and adsorption of inorganic-N by ion exchange resin bags. Effects of the post-clearcutting release of N on tree growth were assessed by measuring foliar N levels and height growth of Abies amabilis (Dougl.) Forbes advanced regeneration. The following sinks for the mineralized forest floor N were investigated: accumulation in plant biomass; solution transfer of inorganic-N and total-N from the forest floor to storage in the upper mineral soil. Based on the difference between the old-growth and the 6- year-old forest floor N capitals, post-clearcutting mobilization of forest floor N was estimated to be 950 kg.N.ha⁻¹ . Although not significant (P=.05), rates of cellulose decomposition were about 3 times higher in the young clearcuts than in the old-growth stand. Indicators of N availability, including in situ rates of mineralization, soil water concentrations and ion exchange resin bags, revealed higher levels of nitrate in the forest floor and/or mineral soil in the 3- and 6-year-old clearcuts than in the other sites. Nitrate concentrations declined to pre-clearcut levels by 8-10 years after clearcutting. %N and N content of current needles, and 1983 height increment of amabilis fir regeneration reflected the pattern of N availability. Of the observed change in forest floor N (kg.N.ha⁻¹ ) over the 10 year post-clearcutting period, plant biomass accumulation accounted for 105 and solution transfer from the forest floor for 187. Together, this amounts to 1/3 of the observed decline of 950 kg.N.ha⁻¹ Potential rates of denitrification in the 5- and 12-year-old clearcut forest floors were 2-5 times greater than in the old-growth stand. The potential rates were sufficiently high to provide a plausible explanation for the post-clearcutting decline in forest floor N. / Forestry, Faculty of / Graduate

Evapotranspiration from a forest clearcut was measured over two growing seasons as part of a larger study of the microclimate of forest clearcuts and microclimate modification by site preparation. Pinegrass is the dominant species on clearcuts in the dry southern interior and is the major competitor with coniferous seedlings. This paper examines the water use of a pinegrass dominated clearcut and the response of surface conductance to environmental variables. Evapotranspiration was derived from eddy correlation measurements of sensible heat flux and measurements of net radiation and soil heat flux. 419 hours of daytime energy balance data from the summers of 1987 and 1988 were analyzed. A rearranged form of the Penman-Monteith equation was used to calculate hourly mean surface conductances for the clearcut. Leaf area measurements were used to calculate stomatal conductance from surface conductances. Stomatal conductance was modelled using boundary-line and non-linear optimization techniques. The most successful model (R² = 0.71) was obtained using non-linear optimization with stomatal conductance as a non-linear function of saturation deficit at the leaf surface (D₀) and solar irradiance. D₀ was calculated from measured evapotranspiration and surface conductance. Response of stomata to saturation deficit would be expected to be better correlated to D₀ than D measured at a reference height above the canopy. Stomatal conductance was also modelled as a function of D (measured at 1.3 m) and solar irradiance. The resulting model (R² = 0.50) was poor compared to that based on D₀. Saturation deficit and temperature were found to be highly correlated both at 1.3 m above the canopy and at the leaf surface. Use of air temperature in the conductance model caused R² to decrease. No relationship between stomatal conductance and volumetric soil water content was found. Hourly evapotranspiration rates calculated using modelled surface conductances agreed well with measured rates.(R² = 0.89). Evapotranspiration was also modelled using the Priestley-Taylor approach. The mean hourly a for all daylight data was found to be 0.81. This simple model was found to give comparable results to the stomatal conductance based model (R² = 0.85). / Land and Food Systems, Faculty of / Graduate

A literature survey indicated that little was known about the effects of commercial clearcutting on stream and watershed solution chemistry. To investigate these effects, five small watersheds were studied in the University of B.C. Research Forest. Three of the watersheds were equiped with weirs, stream height recorders, and soil-air-water thermographs. Soil pits were dug in the three calibrated watersheds and equiped with surface runoff collectors and hanging water column tension lysimeters. Samples of - precipitation above the forest, throughfall (through forest and slash), surface runoff, forest floor leachate, mineral soil leachate near the bottom of the rooting zone, groundwater, and streamwater - were collected at regular intervals and analyzed for pH, electrical conductivity, alkalinity as bicarbonate, K, Na, Mg, Ca, Fe, Mn, Al, Cl, P, N, S, and Si for periods of up to three years prior to clear-cutting and two years after clearcutting. Streamwater was also analyzed for dissolved oxygen and suspended sediment. Sampling was carried out for periods of up to three years prior to clearcutting and up to two years following clear-cutting. The streams were characterized by high discharges from late autumn until early summer and low discharges from May until October, with almost no contribution from snowmelt runoff. Response to precipitation was fairly rapid and it was hypothesized that stormflow arose mainly from flow of water through macrochannels in the soil. Visual observations and chemical data were consistent with this hypothesis. Evapotranspiration from the gauged watersheds was estimated to be about 85 cm per year by subtracting streamflow outputs from precipitation inputs and 65 cm per year using theoretical methods. The discrepancy between these two values was attributed to an unmeasured leakage of water, particularly from the untreated control watershed which rendered too low the streamflow outputs. There was an increase of 30.8 cm in runoff from one watershed, and 27.6 cm from another during the first six months of the dormant season immediately following clearcutting. During this period runoff from the control watershed was 141.5 cm. Stream temperatures underwent annual cycles with winter minima close to 0°C and summer maxima close to 17°C. Diurnal temperature fluctuations were slight and usually less than a few degrees. Clearcutting caused an increase in both maximum and minimum stream temperatures during the first dormant season following clearcutting. The few measurements which were made of suspended sediment, together with visual observations, indicated that concentrations were usually negligible in the streams. Dissolved oxygen concentrations in streams were usually close to 100% saturation and underwent annual cycles with maximum values in winter and minimum values in late summer and early autumn. Clearcutting had little effect on dissolved oxygen values during the cooler wetter months but caused very pronounced decreases during summer and early autumn. This was attributed to the biological and chemical oxygen demands of decaying slash in the streams. Stream chemistry exhibited little diurnal variation but considerable variation with discharge. Sodium, calcium, magnesium, dissolved silica, and bicarbonate concentrations, and electrical conductivity and pH decreased with increasing discharge, whereas potassium and nitrate concentrations exhibited some increases and some decreases. Chloride and sulphate concentrations were generally not significantly related to discharge. In the undisturbed ecosystems, chemical concentrations, pH, and electrical conductivity throughout the systems were generally highest in late summer and early autumn and lowest in winter and early spring. This was attributed to seasonal cycles of geological and biological activity with accumulation of weathering and decomposition products occurring during dry, warm summers. These were flushed through the system in autumn, with solutions becoming progressively more dilute throughout the winter until the onset of warmer weather. Nitrate concentrations tended to be higher in winter than in summer which was attributed to greater nitrogen uptake by organisms in summer. The most abundant ions in precipitation and throughfall were hydrogen, sulphate, and chloride, while calcium, bicarbonate, and sulphate were dominant in all the other types of water samples. There was a general increase in chemical concentrations to maximum values in forest floor leachate followed by a decrease to minimum values in groundwater, and a slight increase again in streamwater. The lowest pH values were in throughfall (4.0-4.5) followed by a steady increase through the system to maximum values in stream-water (6.5-7.0). Clearcutting increased the pH of water reaching the forest floor and surface runoff but decreased the pH of mineral soil leachate, groundwater, and streamwater. It generally decreased chemical concentrations in water reaching the forest floor and in surface runoff, and, to a lesser extent, in forest floor and mineral soil leachates, but it increased concentrations in groundwater and, to a lesser extent, in streamwater. A most notable increase throughout the system was in the concentration of potassium which was attributed to the relative ease with which potassium is leached from decaying vegetation. Increases in nitrate concentrations were particularly high in groundwater. Streamwater concentrations of potassium, iron, calcium, dissolved oxygen, and probably manganese, were significantly affected by clearcutting; concentrations of all these chemicals increased, except dissolved oxygen which decreased. Slight increases in magnesium, nitrate, sulphate, and chloride concentrations, and electrical conductivity, and decreases in pH and bicarbonate concentrations were also observed. All changes were most noticeable during the low flow periods of late summer and early autumn. There were no obvious effects on sodium, aluminium, ammonium, dissolved silica, and phosphate concentrations. In terms of chemical budgets, there was a general net loss of calcium, sodium, magnesium, potassium, and sulphur from all the watersheds, in their undisturbed state, while nitrogen was accumulated and phosphorus underwent very little change. The chloride balance changed from year to year with losses one year and gains the next. Chemical outputs increased relative to inputs with increasing precipitation so that net losses were greater in winter than in summer. Chemical budgets and stream chemistry at Haney were compared to the results of other studies, particularly one in the nearby Seymour watershed (Zeman, 1973). At Haney, clearcutting significantly increased potassium losses and decreased nitrogen gains in one watershed and significantly increased potassium, sodium, magnesium, and chloride losses in another watershed. From the nutrient viewpoint, it appears that clearcutting has not impaired the mechanisms for nutrient retention in the ecosystems of the type present in the study area. This may not be the case for all ecosystems in coastal B.C., or for other forestry practices, such as slashburning. The study has pointed out the need for further work to quantify the role of macrochannels in soils with respect to hydrologic and chemical behaviour of watersheds. It has also pointed out the danger of extrapolating to larger ecosystems the results of lysimeter studies. Chemical analysis of groundwater may offer a more accurate means of estimating chemical losses from soils than do lysimeters. / Forestry, Faculty of / Graduate

Soil samples taken from a clearcut and adjacent uncut site of a Douglas Fir and Western Hemlock old growth forest in the Cascade Range of southern Washington showed greatly reduced adult and juvenile population densities of macro-phytophagous, microphytophagous, and predatory soil acari in the clearcut. These effects appeared to be due to high lethal summer litter temperatures and reduced pore spaces due to scarification. Also, the number of species of acari in the clearcut was lower than in the control after clearcutting.

I studied two aspects of the ecology of amphibians in southwestern Quebec, an area characterized by a mosaic of small forests interspersed by cultivated land and by the presence of rare species at the northern limits of their distribution. One aim was to determine how forest age after clearcutting affected woodland amphibians. Path analysis was used to compare different causal effects of forest age on Plethodon cinereus density in 22 deciduous forests of 30, 60 and $>$90 years old. Repopulation of Plethodon followed forest litter recovery, 30 to 60 years after clearcutting. However, the effect of forest age was overridden by that of microtopography and soil texture. Rana sylvatica seemed also sensitive to clearcutting while Bufo americanus, Ambystoma maculatum and A. laterale seemed much less sensitive. / A second aim was to determine the status and habitat of stream salamanders at the northern edge of the Adirondacks. Sixty stream sections were sampled. Eurycea bislineata was widespread (in 47 sites) and abundant, especially where rocks were numerous on the shore. The distributions of Gyrinophilus porphyriticus (8 sites) and, to a lesser extent, of Desmognathus fuscus (11 sites) were positively correlated with altitude and the presence of forest. It is proposed that these locations might offer the temperate and oxygenated waters needed by these species during winter and summer. (Abstract shortened by UMI.)