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Oaks (Quercus spp.) have dominated eastern forests of the United States for centuries; however, current disturbance regimes discourage oak recruitment and allow shade-tolerant mesophytic species (e.g., maples, Acer spp.) to out-compete oaks. I assessed the effects of mesophication on bird communities by examining differences in breeding bird community structure, abundance, and diversity across 8 and 12 deciduous forest stands in southern Illinois during 2009 and 2010, respectively, using line transects, and by examining a 5-year monitoring data set from across the Shawnee National Forest in 2005-2009. I predicted that variation in bird community structure between maple- and oak-dominated forests can be explained by differential availability of foraging niches. Forest stands used in 2009-2010 were separated along a gradient of hard-mast tree composition, which was defined as the percentage of tree basal area in the stand contributed by oaks and hickories (Carya spp.). Linear regression and Akaike's Information Criteria were used to assess habitat-association models for 7 bird community metrics: bird species diversity, species richness, overall abundance, and abundance of aerial foragers, bark gleaners, foliage gleaners, and ground gleaners. Bird species diversity (Shannon-Wiener H') and species richness ranged from 2.97 to 3.15, and 29 to 37, respectively, over both years. Bird species diversity and species richness were best modeled by a negative relationship with % hardmast tree basal area across both years, whereas overall abundance was best modeled by a positive relationship with understory woody stem diversity. Detection rates for foraging guilds were best modeled by various metrics of habitat structure. Aerial foragers, bark gleaners, foliage gleaners, and ground gleaners responded positively to stem density, downed coarse woody debris density, basal area, and stem diversity, respectively. I used non-metric multidimensional scaling (NMDS) and analysis of similarity (ANOSIM) to examine the degree of dissimilarity among bird communities and site type. In 2010, the bird community differed overall, with communities in oak forests tending (P = 0.09-0.11) to differ those in non-oak and mixed-mesophytic sites. Analysis of a 5-year data set yielded similar results. All models tested for bird-species diversity and species richness were competing, suggesting no individual habitat factor was a strong predictor. Overall abundance and abundance of aerial foragers, bark gleaners and foliage gleaners showed negative relationships to hardmast basal area in all years combined. Ground gleaners responded positively to tree diversity. A post-hoc analysis revealed that overall bird abundance and abundance of foliage-, bark- and ground-gleaning guilds responded positively to an index of riparian areas. Resource use during the breeding season may be shifted to mesic habitats, possibly due to increased resource availability in terms of arthropods and water. Results indicated that mesophication may not have the predicted effects on forest-breeding bird communities, and that vegetation structure was more important in determining bird community structure than tree composition in small-scale forest stands during the breeding season. Resident and over-wintering bird species may be most affected by the loss of oaks due to use during time periods when mesic habitats do not supplement resources. Managers should consider maintenance of a diversity of forest types to maximize avian diversity.

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

A model was formulated to estimate tree component weight by geometrically describing the tree with basic tree parameters such as diameter, height, crown width, and crown length and the shape equations that relate them. The stem is divided into three sections with shape equations to describe the wood and bark in each section. The crown is divided into three sections with three equations. The main branch stems are described in three sections by six equations as in the stem. The shapes and their defining parameters provide a volume estimate for the tree components. The density of the wood and bark in each section of the stem and branches is estimated as a random variable. The density of the crown is defined by estimates of interwhorl distances and numbers of branches per whorl, both of which are random variables. The length of the branches also Influences the density of the crown because the weight of the needles and branchlets is a function of branch length. The density and volume of the components combine to give estimates of the weight of the components. In addition to this indirect calculation of tree component weight, the model calculates-the weight of individual tree components with equations having specific tree parameters as independent variables. The estimates of weight are used to calculate the quantity of slash per tree and the center of mass of each major tree component. The weights of the stump and the unmerchantable top are also calculated in conjunction with the slash calculations. The weights and centers of mass are produced in tabular form. The accuracy of the model is limited by the accuracy of the input data. The model was verified for Douglas-fir, western hemlock, and western redcedar. The verification procedure included manual calculations and comparison with other estimates of weight. The model in its present form can aid in understanding the quantitative effects on the tree of variation in the parameters which describe the tree. Because the weight and volume of the tree components influence their combustibility, the model can aid in describing the tree component of the forest fuel complex. New data and further analyses would be needed to determine the full potential and practical utility of the model described herein. / 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

Regeneration of forest stands is often complicated by the establishment and competition of brush on logged and burned-over areas. The encroachment of brush in the ponderosa pine type of Idaho, particularly Ceanothus velutinus, Dougl. presents a difficult problem to the forest manager. The brush competition severely reduces the growth rate of associated trees, thus extending the period necessary to grow a crop of trees. This situation may seriously limit the economic production of a wood crop of ponderosa pine. Any approach to the solution of brush problems should include a thorough understanding of brush ecology. Those phases of ecology dealing with reproduction and distribution of brush need special emphasis. It has been assumed that most of the brush on logged or burned-over areas originated from seed stored in the forest floor; yet little is known of the quantity or distribution of these seeds. This study was carried out to learn what kind, number and variability of seed is present in the forest floor, and to investigate the number of seed located in different forest conditions, aspects and soil layers. To achieve the above objectives, 48 square-foot, duff-soil samples were taken in the ponderosa pine type of the Boise Basin Experimental Forest in Idaho. Seeds were separated from the samples and major species identified, pretreated and germinated. Appropriate statistical techniques were employed to determine significant results among the different forest conditions, aspects and soil layers sampled.

A fire history study conducted for the Utah State University (USU) Experimental Forest using three distinct periods of fire frequency, historic (1700-1855), settlement (1856-1909), and suppression (1910-present), showed a decreased mean fire interval (MFI) during the settlement period and a greatly increased MFI during the suppression era. The difference was attributed to the influx of ignition sources during the settlement of the nearby Cache Valley, located 40 kilometers to the west. The interaction of settlers with the resource during logging and livestock grazing activities encouraged the high MFI and created the vegetal mosaic now observed on the study area. The elevation of the study area, 2377 m to 2651 m, places the site in the Engelmann spruce-subalpine fir zone (Picea engelmannii, Parry ex Engelm.-Abies lasiocarpa (Engelm. ex. Wats)). The suppression era and its corresponding increase in MFI has permitted the advancement of tolerant species in the understory of the intoleran lodgepole pine (Pinus contorta var. latifolia (Engelm. ex. Wats)) and aspen (Populus tremuloides Michx.). Continue suppression of disturbance from wildfire will allow the lodgepole pine cover type, which experienced the lowest MFI during the settlement period, to be further invaded by tolerant species, leading to a decrease in stand diversity and more intense fires when they do occur.

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