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.

Forest plantations in the southeastern U.S. are fertilized to increase growth on infertile, sandy soils. Nitrogen (N) and phosphorus (P) are the most common growth limiting nutrients. A key question that arises following fertilization of these soils is whether the applied fertilizer benefits only the current trees in the stand or also improves long-term site quality. The objectives of this study were to compare accumulation of N and P in the forest floor and mineral soil among unfertilized and fertilized plantations, determine soluble and residual N and P fractions and soluble carbohydrate and phenol fractions in foliage and litter, determine whether higher N in the forest floor from fertilization resulted in increased release of N from the forest floor and increased mineral soil N availability, and determine loblolly pine forest floor decomposition rate and release of nutrients in a simulated disturbance environment. Research was conducted at a 25-year old loblolly pine (Pinus taeda L.) plantation in NC (SETRES) and 13-year old loblolly pine and sweetgum (Liquidambar styraciflua L.) plantations in GA (Mt. Pleasant). Fertilization resulted in increases in mineral soil N that were likely to be temporary and not sustained following cessation of fertilization N applications. This was likely due to an inability of acidic, sandy mineral soils to retain NH4-N and NO3-N. The forest floor accumulated N due to slow release of N during decomposition. Fertilization with N results in only temporary increases in mineral soil N availability that occur during fertilizer application and from forest floor decomposition. Future changes in N availability are primarily determined by decomposition of the forest floor following a disturbance that accelerates decomposition. In contrast to N, fertilization of loblolly pine and sweetgum with P results in a long-term increase in site P availability. Fertilization with P has lasting effects by increasing mineral soil P in stable forms that can be made available for plant uptake over time suggesting increased supply of P to trees in the next rotation. Retention of P in the mineral soil was likely due to the tendency of acidic, sandy mineral soils to accumulate P in Al- and Fe-phosphates. / Ph. D.

The importance of humus form or forest floor as a principal component of terrestrial forest ecosystems has led to the development of a taxonomic classification of humus forms for BC (first approximation: Klinka et al. 1981; second approximation: Green et al. 1993). This classification, as all others, is based on the field-observable (morphological) features because we expect that they reflect differences in the nature and development of humus forms. However, there is a continuing need to test (1) whether humus forms that appear different are in fact different in their physical, chemical, and biotic properties, and (2) the portability of the classification outside the area in which it was developed. As a result of recent studies of the biotic component of humus forms and recent testing of the classification outside British Columbia (Scandinavia, southeastern Russia, and northeastern China), we have recognized several new diagnostic horizons, and hence new taxa. In this pamphlet, we present synopsis of the third approximation of the classification for review and testing. For more detailed information on the background, methodology, and classification of humus forms, the readers should consult Green et al. (1993). Each humus form is represented by the sequence of organic and mineral horizons that constitute the humus form profile. Identification of a humus form, i.e., giving it a name, requires description of the humus form profile – the identification of master and subordinate horizons. For this reason we have included a description of the horizon designations as well as a synopsis of the classification and a key to the identification of humus forms.

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In British Columbia, humus form identification is widely use to infer the level of plant-available soil nutrients. This identification is based on field-observable (morphological) features. We recognize three major humu forms: Mors, Moders, and Mulls - which are differentiated according to the type of F horizon, and the presence/absence of organic matter-enriched Ah horizons. Mors represent humus forms where decomposition is dominated by fungi, with slow decomposition rates and accumulations of organic matter on the soil surface. Mors are characterized by the presence of a Fm (m - mycogenous) horizon. In contrast, Mulls represent humus forms with high rates of decomposition and faunal activity resulting in organic matter being intimately incorporated into the upper mineral soil layer instead of accumulating on its surface. Intermediate on the humus form gradient from Mors to Mull are the Moders. Moders are similar to Mors in that they have accumulations of organic matter on the surface of the mineral soil but decomposition is not fungus dominated, so they lack the diagnostic Fm horizon. The central concept of the Moder is represented by the Leptomoder, which is characterized by a Fz (z - zoogenous) horizon with an active population of soil meso- and microfauna, fungal mycelia are not present or present in small amounts. When both fungal mycelia and faunal droppings can be found, but neither clearly predominate over the other, an Fa (a - amphimorphic) horizon results. Fa horizons are characteristic of Mormoders, an integrade between Mors and Moders. Considering the prevalence of Mormoders and Leptomoders in B.C. and the difficulties in identifying Fa horizons, the aim of this study was to determine whether the morphological features used to differentiate these two Moder humus forms reflects differences in their physical, chemical and biotic properties.

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Thesis (M.S.)--Miami University, Dept. of Botany, 2006. / Title from first page of PDF document. Includes bibliographical references.

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No description available.