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Response to fertilization is a function of the degree to which nutrients are limiting growth, the capacity of individual trees to respond to nutrient inputs, the degree to which other factors limit growth, and the possible extrinsic effects of treatment (e.g., root mortality due to fertilizer-induced soil pH effects). Recognition and examination of these factors is essential if response to fertilization is to be predictable. Over the past 25 years numerous western hemlock fertilizer trials have shown responses ranging from negative to positive with no clear trends. Theories for this erratic response include: (a) different nutritional requirements during different stages of stand development; (b) high native N availability or low supplies of other nutrients (P and S, in particular); (c) differential adverse effects of N fertilizers on surface roots, mycorrhizal populations and P nutrition; (d) a requirement for slow release N; and (e) induced water stress. The objective of this study was to develop site-specific guidelines for western hemlock fertilization decision-making for industrial use. This study reports on the first and third growing-season response to two different fertilizer treatments, and identification of possible relationships between fertilizer response and site and stand conditions.

The influence of salal on tree growth has attained considerable attention in coastal British Columbia. Field observations, surveys, and studies in the CWH zone have indicated poor growth performance of crop tree species in salal-dominated plantations and natural immature and old-growth stands. Where sites have been burned and planted, tree growth has improved; similar effects have been observed for naturally regenerated stands. Immature stands that developed after wind disturbance or harvesting feature rapid growth and nearly complete absence of salal. As studies have shown that ericaceous plants negatively impact tree growth, the salal on potential harvest sites has been considered undesirable. This study examined (1) the possible influence of salal on the stand, soil nutrient status and site index, and (2) the relations between site index, salal, plant communities, and site in disturbed, immature, coastal Douglas-fir ecosystems. We compared vegetation and environmental characteristics of 101 ecosystems, and examined differences in foliar and soil nutrient characteristics and site index between stands with high and low salal cover through analysis of variance (ANOVA) and regression analysis.

Site classification in the biogeoclimatic ecosystem classification system is based on three differentiating properties: climatic regimes (expressed by biogeoclimatic subzones or variants), soil moisture regimes (SMRs), and soil nutrient regimes (SNRs). A SNR represents a segment of a regional soil nutrient gradient, i.e., soils which provide similar levels of plant-available nutrients over a long period. SNRs are identified in the field using a number of easily observable soil morphological properties and indicator plant species. However, we need to know to what extent soil nutrient properties support these indirect field-estimates. There have been several studies that quantitatively characterize regional soil nutrient gradients in different climatic regions, but no study has yet been done in the subalpine coastal forest (Mountain Hemlock zone). Influenced by a maritime subalpine boreal climate, high-elevation coastal soils differ from low-elevation soils by having a thicker forest floor and a higher organic matter content. In the study summarized here, relationships between soil chemical properties and field-estimated SNRs are examined and soil chemical properties and field-identified SNRs are related to the site index of Pacific silver fir (Abies amabilis (Dougl. ex Loud.) Forbes) - one of the major timber crop species in the Coastal Western Hemlock and Mountain Hemlock zones.

The largest area of commercial timber plantations in southern Africa is situated along the Eastern Transvaal Drakensberg Escarpment north of Nelspruit. The site requirements of tree species in this area are poorly understood. The purpose of this study was to examine site-tree relationships in the region and the implications of such relationships for the science of forestry. Pinus patula Schiede & Deppe in Schlecht. & Cham. was selected for the study as it is the most widely planted species in the region. In Chapter 1 the geology, geomorphology, climate, soils and vegetation of the study area are described. A geological map was compiled. Soil descriptions were based on 439 soil pits distributed so as to cover the range of site conditions in the area. The regression techniques used to identify key environmental factors and to model their relationships with tree parameters are described in Chapter 2, in which site-growth relationships specifically are investigated. In mature stands of P. patula 159 plots were established in such a way as to cover the widest variation in both site conditions and tree growth. The relationship between site index (mean top height at 20 years) and 100 site plus 10 stand parameters recorded at each plot was modelled by means of best-subsets, multiple and ridge regression. Several candidate models were compared on the basis of coefficient of determination and validation using independent data. The best model predicted the site index of the validation plots within 60 cm of the measured site index. The possible roles of the site variables identified by the models are discussed. In Chapter 3 site-foliar nutrient relationships are described. A close relationship was found between foliar and soil nutrient levels for the six major geological substrates. Site index was more accurately predicted from concentrations of individual foliar nutrients than from ratios of these nutrients. The Diagnosis and Recommendation Integrated System (DRIS), however, appeared to have greater potential for nutrient diagnosis. Provisional ORIS norms for P. patula were computed. In Chapter 4 the excessive accumulation of litter in P. patula stands was examined. Undecomposed litter layers were greater than 15 cm in thickness on nearly 25% of the 159 sites studied. Average litter layers contained greater amounts of nutrients than the underlying topsoil. Due to the colonization of the litter by tree roots, the degree of immobilization of nutrients in litter is not known. Environmental factors associated with variation in litter thickness were identified by models which explained up to 73% of the total variation. These factors are considered to act indirectly by promoting or retarding decay organisms. The possible implications of litter accumulation for the maintenance of site productivity are discussed. In Chapter 5 relationships between site and some wood properties are described. Although between-tree variation was larger than between-site variation, some important relationships with site were identified. 10% of all trees on the 159 plots had severe stem bumps. Most of the variables in a model to predict the severity of bumps could be interpreted as being associated with stem stability or exposure. The conclusion was that wind is probably the major cause of this defect. The findings of the study are summarized in Chapter 6. Particular attention is given to a synthesis of the possible roles of site factors in their relationships with the tree parameters investigated. There were strong relationships between tree parameters and mainly rainfall, altitude, soil wetness, exchangeable bases, effective rooting depth, slope position and geology. The single most deficient nutrient element appeared to be calcium. The implications for both research and management are outlined. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1990.

Thesis (M.S.)--University of Tennessee, Knoxville, 2008. / Title from title page screen (viewed on Sept. 23, 2009). Thesis advisor: Wayne K. Clatterbuck. Vita. Includes bibliographical references.

Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Red Lapacho is timber species with largest market value, considered along with Mahogany, as 'green gold' in areas of natural forest logging. Therefore, the objective of this study was to analyze the different factors that influence the growth of this species, taking into consideration the spatial and temporal dependence inherent to the data. A census of Red Lapacho individuals was carried out in a natural fragment of Subtropical Deciduous Forest with approximately 13 hectares of area. Quantitative morphological and diameter increment data were obtained for each tree of this species. Competitors defined by Bitterlich plots were measured and identified, and a regular grid with infill points of soil sampling were also analyzed. Spatial patterns of distribution of Red Lapacho and its dimensions had completely spatial randomness patterns. Sampled species richness from competitors was of 60 species and the competition generated by them had a random spatial pattern as well. A model for the height – diameter relationship using Generalized Additive Mixed Models (GAMM) produced better results when the latent spatial pattern was included in the model. The spatial patterns of nutrient availability were influenced by relief of the area and distance from the edge of the forest and grassland environments. Anionic nutrients were strongly influenced by the spatial dynamics of the two vegetation types while cations were influenced mainly by pedogenesis. The spatio-temporal Bayesian diameter increment model developed for the Red Lapacho trees showed that there was considerable inter – annual variation in tree growth. The spatial variation in tree growth was closely related to the pedogenesis of the area under study, more specifically, lower increments were observed in areas where the soil had signals of water influence in tits formation. Using site proxies based on geocentric, phytocentric and dendrocentric approaches was able to take into consideration the spatial variation in the growth of Red Lapacho trees and, all approaches may be utilized in the development of growth models. / O Ipê – Roxo é uma das espécies de madeira com maior valor de mercado, sendo considerado, juntamente com o Mogno, o 'ouro verde' em áreas de exploração de florestas naturais. Assim sendo, o objetivo deste estudo foi analisar os diferentes fatores que influem no crescimento desta espécie, levando em consideração a dependência espacial e temporal inerente aos dados. Foi realizado um censo dos indivíduos de Ipê – Roxo em um fragmento natural de Floresta Estacional Decidual com aproximadamente 13 hectares. Foram levantados dados morfométricos e de incremento em diâmetro de cada uma das árvores desta espécie. Os competidores definidos por parcelas de Bitterlich foram medidos e identificados e, uma grade regular com pontos de preenchimento para amostras de solo foram avaliados. Os padrões espaciais de distribuição das árvores de Ipê – Roxo e suas dimensões se adequaram à completa aleatoriedade espacial. A riqueza de espécies amostradas como competidores foi de 60 espécies e a competição por estas gerada também teve padrão espacial aleatório. A modelagem da relação hipsométrica das árvores utilizando Generalized Additive Mixed Models (GAMM) obteve melhor ajuste quando o padrão espacial latente foi incluso no modelo. Os padrões espaciais de disponibilidade dos nutrientes foram afetados pelo relevo da área e pela distância da borda dos ambientes florestal e campestre. Nutrientes aniônicos foram fortemente influenciados pela dinâmica espacial entre os dois tipos vegetais enquanto cátions foram influenciados principalmente pelo processo pedogênico. O modelo espaço – temporal Bayesiano de incremento em diâmetro desenvolvido para as árvores de Ipê – Roxo mostrou que existe considerável variação inter - anual do crescimento. A variação espacial do crescimento também se mostrou relacionada com o processo pedogênico da área sob estudo, sendo que menores incrementos foram observados em áreas onde o solo apresentou sinais de hidromorfismo. A utilização de estimadores de sítio baseados em índices geocêntricos, fitocêntricos e dendrocêntricos foi capaz de levar em consideração a variação espacial do crescimento de árvores de Ipê – Roxo e, todos podem ser utilizados para a construção de modelos de crescimento.

M.S.

Successful renovation of wastewater and sludge via land application depends upon sludge-induced soil changes associated with carbon (C) and nitrogen (N) cycles within the soil/plant system. The C, N, and hydrologic cycles within a soil/sludge system receiving a year-round, daily application of paper mill sludge were studied. Soil samples were collected from three locations on a land application site in the Piedmont of Virginia that had received papermill sludge applications for six, two, and no prior years. The average application rate was 4.4 cm/wk, each week of the year, with a N loading of 700 kg N ha⁻¹yr-⁻¹. The column study showed that C and N were still accumulating on the land application site after 6 years, but at a decreasing rate. Based on this study, C accumulation will level out after 13 years of application, but N will continue to accumulate for almost 30 years. As application period increased, soil bulk density increased in the O, A, and B horizons, the percentage of non-capillary porosity fell below 10% in the A horizon and approached zero in the B horizon, and there was a dramatic decrease in the soil's hydraulic conductivity in both the A and B horizons. Nitrogen leaching is expected to increase with time due to high amounts of N in the papermill sludge, a continued narrowing of the C:N ratio, a high percentage of nitrification, and low denitrification rates. Experimental timing and rates of sludge additions were imposed to alter the aerobic/anaerobic properties of the soil system to determine the conditions under which optimum C and N mineralization, nitrification, and denitrification would occur. Application rates were factorially arranged for single or multiple doses on a daily or alternating schedule. The C decomposition and N mineralization processes were both optimized with an increase in the length of cycle; they were maximized with an alternating 9 days on/9 off application schedule. The nitrification potential also increased with the length of cycling, with an average nitrification rate of 96%. Denitrification was minimal in all treatments, with an average denitrification rate of 16%. This was primarily attributed to movement of nitrate-N below the most biologically active zone in the soil column. Sludge renovation will ultimately depend upon the excess N being sequestered in plant biomass or denitrified. Proper management of these processes will ensure that wastes decompose, and that N is stored or evolved as a benign gas rather than leached at unacceptable levels. / Master of Science

The Surface Mining Control and Reclamation Act (SMCRA) of 1977 requires that mine operators reclaim mined land to achieve productivity levels equal to or greater than premined conditions. Presently, the standard for evaluating reforestation success is based solely on tree-seedling survival. This method is an estimator of stand density and not an indication of site productivity. There exists a need to evaluate mine soils based on their capability of growing merchantable timber. This model would aid the reclamation process by providing a means for assessing mine soils based on their quality and productivity. / Master of Science