Despite the recognized role of soil arthropod fauna on nutrient cycling and decomposition processes, many aspects of the effects of sylvicultural methods in forest ecosystems upon their biology remain poorly understood. The long term effects of prescribed fires on soil arthropods in forest ecosystems in the Pacific Northwest have never been studied. Soil samples were taken from three sites located in the Willamette National Forest in 1992: paired sites that were either clear-cut without burning and clear-cut with burning 40 years ago. One hundred and eight samples were processed; the arthropods were separated, identified and counted. To study the biology and behavior of some arthropods, eight species of oribatid mites were reared in laboratory conditions. Their life cycle, feeding behavior and reproduction were studied. Results indicated that there were no statistical significant treatment differences either in terms of total numbers of organisms or biomass. However, the majority of the commonest taxa did show offsetting treatment responses. A total of 204 taxa were found in the three sites. The most important groups included Collembola, mites, and insects. Other groups also represented, but in smaller numbers, were spiders, symphylans, pseudoscorpions, and centipedes. Of all these groups, oribatid mites was the best represented and appears to be a useful indicator of disturbances. / Graduation date: 1995

Site preparation treatments are often used prior to the planting of clearcut forest lands to improve planter access and to increase the number and quality of planting spots. Most mechanical site preparation treatments alter the configuration and material composition of surface soil materials, and can have marked effects on soil properties important to seedling survival and growth. Effects of some of these treatments on soil moisture, soil temperature, rates of nitrogen mineralization, and the establishment of Picea glauca x engelmannii seedlings were examined on fresh, moist, and wet sites in the moist cold subzone of the Sub-boreal Spruce Zone in west-central British Columbia. Four types of microsite alteration were investigated: forest floor removal (spot scalping), soil mounds over inverted sections of forest floor (inverted mounds), mineral soil mounds over a mineral soil surface, and inversion of the forest floor and mineral soil in place. Soil temperature was monitored continuously and soil moisture weekly at the 10-cm depth in 16 combinations of site and microsite treatment during two growing seasons. The response of seedling height and diameter growth was monitored for three growing seasons. Effects of altering soil temperatures through mechanical treatments on rates of nitrogen mineralization were examined by incubating a standard soil material in a range of microsites created by six combinations of site and mechanical treatment. Effects of substrate quality and soil temperature on rates of nitrogen mineralization were examined in paired mounded and untreated spots in fresh, moist, and wet sites. In all sites, early growing season soil temperatures in the seedling rooting zone were substantially warmer in inverted mounds than in other treatments. Spot scalping increased temperatures slightly relative to controls in the fresh site, but had little or no warming effect on moist and wet sites. Inverted mounds became substantially drier than other treatments during periods of low rainfall, particularly in the fresh site. After three growing seasons, seedling height growth was greatest in inverted mounds, irrespective of site. Amounts of nitrogen mineralized in a standard soil material during incubation for 77 days in the field were significantly greater for samples placed in inverted mounds than for those placed in other microsite treatments. There was a significant positive correlation between amounts of nitrogen mineralized during field incubations and degree hour sums calculated for associated microsite treatments and sites. Both substrate quality and soil thermal regime affected rates of N mineralization in samples from paired mounded and untreated spots, and an interaction was observed between the two factors. / Graduation date: 1991

Forest soils with low bulk densities are often considered less susceptible to compaction than soils with higher bulk densities. The objective of this study was to determine if soil strength controlled the compression of soils with low bulk density. Four soils were selected for this evaluation. Three of these were andic soils with low bulk density and the fourth soil was a more dense, cohesive soil. Undisturbed samples of saturated and partly saturated soil were compressed in a one-dimensional consolidation test apparatus. Measurements with separate samples were at one of 7 normal stresses between 0.033 and 1.96 MPa. Shear strength of saturated soil was measured in direct shear tests. Primary consolidation of saturated soil was completed in less than one minute at all normal stresses. Shear stress and bulk density increased continuously during shear strain. The compression index of the cohesive soil was significantly larger (p<0.05) than that of the andic soils. The shear strength of andic soils (average cohesion intercept of 0.016 MPa and friction angle of 33.3°) was significantly higher (p<0.05) than the cohesive soil (cohesion intercept of 0.028 MPa and friction angle of 28.9°). When saturated, the cohesive soil was more compressible than the andic soils because of lower soil strength. A nonlinear model of soil compression was developed that accurately predicted the compressed density of saturated and partly saturated soil as a function of normal stress, initial bulk density of undisturbed samples, and degree of saturation. As degree of saturation decreased, the compressibility of the cohesive soil decreased more rapidly than it did for the andic soils. As a result, bulk density of dry cohesive soil increased less than it did for dry andic soils. Differences in the compressibility of soils were attributed to texture and clay mineralogy. The differences in the compressibility of these soils were much smaller than were the differences in bulk density. Decreasing water content affected the compressibility of the cohesive soil more than it affected the andic soils. Because soil strength controls the compressibility of these forest soils regardless of bulk density, it will also determine the susceptibility of soils to compaction by machines. / Graduation date: 1991

Knowledge of the potential productivity of a tree species becomes especially important when timber production is the primary management objective. However, direct determination of potential productivity is often not possible. For example, in situations where the site is unstocked, stocked with trees unsuitable for productivity measurement, or stocked with species other than the one of interest. In these cases, an indirect estimate using known characteristics of the site itself is required. Such estimates were made using regression to model site index with indirect measures of site quality for lodgepole pine (Pinus contorta) and interior spruce (Picea engelmannii × P. glauca) in the Sub-Boreal Spruce (SBS) zone of central BC. We tested the utility of these productivity relationship models for predicting the site index of lodgepole pine and interior spruce (Kayahara et al. accepted for publication).

Note: / The soil-solution partitioning of dissolved organic carbon (DOC) withinmineral soil horizons is primarily controlled by processes of adsorption and desorption. These abiotic processes largely occur within a short equilibration time of seconds to minutes, which generally occur faster than microbial processes. To characterise the adsorption of DOC to mineral soils, I used the Langmuir adsorption isotherm, which holds several advantages to the commonly used linear initial mass (IM) isotherm. One advantage to using the Langmuir isotherm is anestimation of the maximum DOC adsorption capacity (Qmax). The Qmax estimates the number of remaining DOC binding sites available on the mineral soil particle surfaces. I modified the traditional Langmuir isotherm in order to estimate the DOC desorption potential of native soil organic matter (SOC).[...] / Le partitionnement entre les solutions de sols du carbone organiquedissous (COD) dans les horizons des sols minéraux est essentiellement contrôle par les processus d'adsorption et de désorption. Ces processus abiotiques se déroulent normalement dans un bref temps d'équilibration variant de quelques secondes a quelques minutes, ce qui est en général plus rapide que les processus microbiens. Pour caractériser Fadsorption de COD aux sols minéraux, nous avons utilise l'isotherme d'adsorption de Langmuir. Cette isotherme présente plusieurs avantages par rapport a Fisotherme de masses initiales (IM) linéaires couramment utilisée, en particulier F estimation de la capacité d'adsorption maximale du COD (Qmax). Le Qmax estime le nombre de sites de liaison de COD restants a la surface du sol minéral. Nous avons aussi modifie Fisotherme de Langmuir traditionnelle afin d'évaluer le potentiel de désorption de COD de la matière organique du sol indigène (MOS).[...]

The soil-solution partitioning of dissolved organic carbon (DOC) within mineral soil horizons is primarily controlled by processes of adsorption and desorption. These abiotic processes largely occur within a short equilibration time of seconds to minutes, which generally occur faster than microbial processes. To characterise the adsorption of DOC to mineral soils, I used the Langmuir adsorption isotherm, which holds several advantages to the commonly used linear initial mass (IM) isotherm. One advantage to using the Langmuir isotherm is an estimation of the maximum DOC adsorption capacity (Qmax). The Qmax estimates the number of remaining DOC binding sites available on the mineral soil particle surfaces. I modified the traditional Langmuir isotherm in order to estimate the DOC desorption potential of native soil organic matter (SOC). / Sorption characteristics were derived for a broad range of52 mineral soils collected from 17 soil profiles spanning across Canada from British Columbia to Quebec. Mineral horizons with the greatest Qmax included the Fe-enriched B horizons of acidic Podzols and Volcanic soils, followed by B horizons not enriched in Fe, followed by A and C horizons. Podzol B horizons were distinct from all other horizons due to significantly higher desorption potential. Soil properties predicting the adsorption characteristics of DOC also predicted the adsorption characteristics of dissolved organic nitrogen (DON). Adsorption of DOC and DON was tightly coupled (R 2 = 0.86), however the ratio of DOC:DON in the final equilibrium solution lowered for 48 out of 52 minerals horizons. These results suggest that DON may be slightly more mobile than DOC. / A short-term (32 day) incubation was perform to establish the fate of indigenous soil C, relative to newly adsorbed soil C to four mineral soils with different adsorption characteristics. Soil columns were leached periodically and sampled for DOC and CO2 production. Two Fe-enriched mineral horizons with high adsorption capacity released low amounts of old SOC, yet released almost all of the newly adsorbed SOC. In contrast, two B horizons without Fe-enrichment released greater amounts of old SOC, and retained a greater fraction of the newly adsorbed SOC than the Fe-enriched horizons. These results identify a contrast between the fate of indigenous and newly adsorbed SOC on mineral soils with differing Qmax. / The final component of this study examined changes to the molecular structure of DOC after equilibration with mineral soils. Multiple techniques were used to assess changes in the molecular composition of DOC, including the analysis of aromatic content by specific UV absorbance (SUVA) and fluorescence spectroscopy, analysis of molecular weight distribution (MWD) with high performance size exclusion chromatography (HPSEC) and functional group analysis with Fourier transform infra-red spectroscopy (FTIR). The solution phase DOC generally showed a reduced aromatic content, along with the removal of organic compounds with carboxyl groups. The MWD of DOC was reduced after equilibration to mineral soils, and the reduction in average molecular weight was related to the Qmax of mineral soils. / The various components of this thesis have contributed to the overall understanding of controls on the adsorption of DOC and DON species to mineral soils of the Canadian temperate and boreal forest.

No description available.

The adsorption behaviour of trace metals in soil may provide us with a way to more accurately predict and assess the toxicity of metals in the environment. This thesis reports efforts to apply surface complexation modeling to agricultural and forest soil and to relate model parameters to common soil properties. This study considered Ca, Cd, Cu, Pb and Zn but the methods here could be applied to other metals. In Chapter 2, the surface charge and adsorption behaviour of a set of Ap horizons was characterised using back-titration and batch adsorption techniques. With the objective of simplifying the application of the NICCA model to surface charge and cation adsorption in whole soils the parameters of the NICCA model were related to soil properties (Chapter 3). Four of the six surface charge parameters could be predicted from soil properties and this enabled me to reasonably predict the surface charge of a second group of soils from soil properties. These results suggest that it is possible to make reasonable predictions about the surface charge and adsorption behaviour of a given type of soil using some easily measurable soil properties and a set of generic NICCA adsorption parameters for that soil type. In Chapter 4 this idea is applied to the determination of lime requirement for the agricultural soils.

The objective of this study was to investigate K, Ca, and Mg immobilization in the stem of species typical of the hardwood forest of southern Quebec. The species examined included American basswood, sugar maple, and white ash from a rich site, and American beech, red oak, and red maple from a poor site. Firstly, rates of immobilization were evaluated over a time span of 40 years. Higher rates of immobilization in the wood only were generally observed on the rich site. Sugar maple immobilized Ca at an elevated rate during 1978--1997, in comparison to the other species on site. In the case of Ca for white ash, and Ca and Mg for red oak, a low wood element concentration and a high rate of growth was associated with a low rate of immobilization. Mean annual immobilization rates on a whole stem basis were also determined for the life of the tree. These results suggest that American basswood and red oak immobilize significant amounts of Mg and Ca in their bark, respectively. / In a second study, concentrations of K, Ca, and Mg across the radial section of the stem (heartwood, transitional, sapwood, and bark) were determined. In a majority of cases, the bark was highest in concentration of base cations. Whereas, for the woody portion of the stem, concentrations were generally highest in the heartwood.

Upland soils are a significant sink of atmospheric methane, but the organisms responsible for methane consumption have yet to be identified. The ecology of methanotrophs was investigated in a beech forest soil which exhibited atmospheric-methane-uptake. Maximal methane-oxidation was observed in the upper mineral layer between the organic and inorganic horizons at a rate of 3.1 +/- 0.3 nmoles CH 4 g [fresh wt soil]-1 d-1. A clone bank of the methanotroph pmoA gene was constructed by PCR amplification from soil DNA extracts. The PCR primers used coamplify the related amoA gene of ammonia-oxidizers. The clones recovered grouped into three clusters: Nitrosospira-like sequences, a group somewhat related to alpha-Proteobacteria methanotrophs and previously referred to as the RA14 group, and a cluster which could not be characterized as either amoA or pmoA sequences. No pmoA genes closely related to genera of cultured methanotrophs were obtained. The 16S rDNA was also targeted using eubacterial and methanotroph-specific primers. 16S rDNA sequence analysis revealed the presence of organisms distantly related to known methanotrophs. Methanotroph enrichment cultures were established by inoculating mineral salts medium with soil and incubating under an atmosphere of 10% methane in air. Gene sequencing from the enrichments indicated the presence of organisms belonging to the genera Methylosinus and Methylocystis. The results suggest that the dominant methanotrophs in the forest soil are not related to known organisms and do not grow under conditions typically used to isolate methanotrophs.