Thesis (Ph. D.)--Oregon State University. / Third progress report for grant NSF G-21015 initiated January 1, 1962. Contribution to project on Influence of interplanted and pure stands of red alder (Alnus rubra) on microbial activity and carbon-nitrogen transformations in soils of the Douglas-fir region. Progress report for NSF grant: G21015. Includes bibliographical references (leaves 152-164). Also available online.

Soil microbial communities can be characterized by community structure and function (community composition) across a spectrum of spatial scales, and variation in soil microbial composition has been associated with a number of environmental gradients. This study investigates the structure and function of soil microbial communities under mature, undisturbed forested sites across a range of regional climates in British Columbia and Alberta, and also examines the variation in community composition within sites. Phospholipid fatty acid analysis was used to investigate the structure of soil microbial communities and total soil microbial biomass at each site. Extra-cellular enzyme assays established the functional potential of the soil microbial community at each site. Multivariate analysis of the data showed that the soil microbial communities under different forest types did significantly separate along the regional climate gradient by both community structure and function, despite high local variation in the communities. Soil moisture content and soil organic matter concentration consistently exhibited the strongest relationship with microbial community characteristics, although the functional and structural responses to the external drivers were different. Microbial community function and structure also changed with soil depth but not with time of sampling. Microbial community function was related to the regional annual average precipitation gradient. Most of the locations exhibited unique microbial community functional profiles in their soil layers; however the enzyme activities in the samples from the driest (Ponderosa Pine) and wettest (Mountain Hemlock) locations were notably different from each other and from those of the other locations, especially in the organic layers. The moist maritime-influenced Coastal Western Hemlock (CWH) forest exhibited microbial community structural characteristics which were unique from those of the other forest locations. The higher abundance of bacteria relative to fungi in the CWH forest soils may be related to the significantly higher available nitrogen concentrations at this site. / Forestry, Faculty of / Graduate

Laboratory and greenhouse experiments were carried out with controlled burning and with seedling growth correlated to soil chemical changes. The surface of soil blocks from three sites of the Coastal Western Hemlock Zone were burned at two intensities and planted separately with seeds of Douglas-fir, western hemlock, and western redcedar. Growth data were recorded periodically and dry weights of the seedling crops were obtained to determine treatment differences. The burning procedure showed the insulating and cooling effects of the vaporizing soil moisture. The burning slightly increased germination of Douglas-fir and western hemlock, generally promoted fungal population, and initiated different chemical changes in the soil on each site. Dry matter production, for all species combined, varied with treatment for each site in the following decreasing order: Swordfern site - severely burned, moderately burned, unburned control; Moss site - unburned control, moderately burned, severely burned; Salal site - moderately burned, unburned control, severely burned. Comparisons of dry matter production on control blocks with that in nature indicated that the removal of blocks from the natural environment had significantly changed the original conditions. In consequence, new artificial sites were created. Consistent evidence of the rhizosphere effect was produced on soil pH by seedlings, especially by Douglas-fir. Dormancy was successfully broken in all plants and there was evidence of different responses in photo-periodism with each species. The highest dry matter production was directly related to increased soil pH, to increased partial cation saturation, and to increased concentration of available phosphorus but to a decreased cation exchange capacity. Cation exchange capacity was inversely related to the availability of nutrients. Decrease of cation exchange capacity proved to be a beneficial effect of fire. In this experiment, where the ash was not supplied as usual in a slash burn, the increased base saturation resulted from the decreased cation exchange capacity. As compared with field samples in August 1959, total nitrogen was lower in all blocks in June 1960. Nitrogen increased in the following year in all variants of the Swordfern site and somewhat in unburned control blocks of the Moss and Salal sites. The Swordfern site benefited from burning by accelerated mineralization, which substituted for the deprived seepage. Fire caused the least damage to this habitat. The Moss site suffered heavily by burning, which reduced humus, the main source of nutrition. The unburned blocks were benefited by fast decomposition of humus in the greenhouse. The Salal site's thick raw humus benefited from moderate burn, which removed part of the humus and acted as a fertilizer on the remainder. Severe burning was most harmful on this site by the destruction of the large part of humus. Rich soils, usually with seepage water, are less damaged by fire than poor soils with strong drainage. It is mainly because in rich soils organic matter is at least partly incorporated into the mineral horizon and acts readily after fire especially for nitrogen supply. / Science, Faculty of / Botany, Department of / Graduate

Laboratory lysimeters were used to investigate the behaviour, over time, of a humid west coast forest soil under intermittent primary municipal waste water irrigation. Mineral soil packed to a depth of 69 cm and to a uniform density of about 0.9 gm per cm³ was covered with a forest floor 9 cm thick. Sintered glass bead tensiometers were used to gauge the water potential distributions in the soil lysimeters. Irrigation and drainage systems were designed to maintain constant rates of waste water application and facilitate measurement of drainage rates. Two groups of soil lysimeters each with triplicate samples, were loaded with waste water at the rates of 0.23 cm per day ( 37 cm³ per day ) and 0.47 cm per day ( 75 cm³ per day ) for a period of 9 months. The soil lysimeters were incubated at a temperature of about 15.5 degrees Centigrade. The total amounts of nitrogen added to both groups of soil lysimeters were 223.7 gm and 436.9 gm or equivalent to 1.4 % and 2.7 % of the total nitrogen of the original soil, respectively. Renovations of wastewater in terms of nitrogen were 75 % and 43 % with respect to the two groups of soil lysimeters. Renovations in terms of phosphorus were more than 99 % in both groups of soil lysimeters. Retention of nutrients by the soil was increased with time under favourable aerobic conditions. Uptake of nutrients by vegetation in the field would minimize leaching losses. Results from this experiment indicated no significant changes in the physical and chemical behaviour of the soils. Proper design of the waste water irrigation system in terms of loading would maximize the efficiency of renovation without deteriorating the behaviour of the soils. / Land and Food Systems, Faculty of / Graduate

A study of the soils and soil capability classification for forestry of the Mission Tree Farm Licence No. 26 was carried out. The soil survey and soil chemical analyses were done in cooperation with the British Columbia Department of Agriculture, Soils Division, Kelowna, B. C. The purposes of the study were: to characterize the soils found in Compartment One, to determine the forest capability of these soils, to recommend management practices for these soils for forestry purposes, and to compare soil mapping at scales of 1:12,000, 1:15,840, 1:31,680, and 1:63,360. Fourteen soil series were recognized and used as criteria for the mapping units in this area. Ten soil series were established, described, and chemically characterized. Although the soil series could be morphologically recognized in the field, the chemical analyses exhibited very little characteristic differences among the series. Vegetation could not be used consistently as criteria for differentiating among the various mapping units. Landform was the chief aid in establishing the extent of the soil mapping units. Each soil series was rated for capability to produce commercial forest growth. The major tree species involved were western hemlock, Douglas-fir, and western red cedar. The soils were evaluated for forest management practices including, reforestation, road building, erodibility, logging practices, and species adaptation to specific soils. Four scales of mapping were compared and discussed in relation to their uses for specific purposes. For an area such as Compartment One on which good forest management is being practiced, mapping at the scale of 1:15,840 was ideal. / Land and Food Systems, Faculty of / Graduate

In mature forests, gains and losses of nitrogen may be dominated by the gaseous transformations, asymbiotic nitrogen fixation and biological denitrification. Both are reduction reactions and are affected by moisture conditions, temperature, pH, supply of organic carbon and the availability of mineral nitrogen. Gaseous nitrogen inputs, due to asymbiotic nitrogen fixation, and outputs, due to biological denitrification were quantified for a mature coniferous forest in southwestern British Columbia. Forest floor material, mineral soil, decaying wood, foliage and bark were incubated in an atmosphere of 0.1 atm acetylene to allow the simultaneous measurement of N₂0 production by denitrifying bacteria and acetylene reduction by free-living bacteria and blue-green algae. Forest floor material accounted for 80% of a total annual input of 0.8 kg N ha⁻1 a⁻1. Relatively small amounts of nitrogen were fixed in mineral soil, decaying wood and foliage and no indication of nitrogen fixation activity in bark was detected. Traces of denitrification were found, but gaseous output of nitrogen was effectively 0.0 kg N ha⁻1 a⁻1. It is hypothesized that this forest may prevent nitrogen Joss by outcompeting other sinks for mineral nitrogen, thereby allowing a slow accretion of nitrogen by asymbiotic nitrogen fixation and bulk precipitation input. / Forestry, Faculty of / Graduate

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

Atmospheric deposition of reactive nitrogen (N) from anthropogenic sources to forested systems may have acute and long-term deleterious impacts on tree species and water quality. Understanding how nitrate (NO3-) moves through the soil system and if it has the potential to be retarded from vertical or lateral leaching allows for a better understanding of the processes important for NO3- movement and export from forested watersheds. We examined four watersheds at Coweeta Hydrologic Laboratory (CHL) and determined that soil NO3- sorption is a mechanism for abiotic NO3- retention. NO3- sorption was best described with an S-shaped, sigmoidal model for B horizons that suggests that NO3- sorption to soil colloidal surfaces has a higher affinity for soil solution at low equilibrium concentrations. Parameter a, the sorption maximum, was most strongly correlated to ammonium oxalate extractable Al (Alo) and Mn (Mno), suggesting that amorphous Al and Mn oxides may be the primary source of positively charged sorption sites. Parameter b, the width of the sigmoid curve slope, was best predicted by %C in the soil; suggesting that C compounds may bind to and reduce the availability of positively charged exchange sites for NO3- sorption. Previously harvested watersheds exhibited larger variability in parameter values Xo, the inflection point of the curve, and b. High elevation watersheds had higher median values for Alo, Mno and the ration of oxalate to dithionite extractable Fe (Feo/Fed), suggesting that the soils at higher elevations are at earlier stages of pedogenic development and have more poorly crystalline Fe and Al oxides. The greatest potential for sorption maybe at an intermediate soil depth between where there is a significant decrease in biologically cycled C, phosphate and sulfate yet there is enough mineral weathering to provide the mineralogical structures that can support positively charged surfaces. / Master of Science

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