A description of the development and subsequent use of an integrated and semi-stochastic computer simulation model, <I>GHAFORGROM</I> (Ghana Forest Growth and Yield Simulation Program), designed to investigate forest tree dynamics and also predict growth and yield of timber in the tropical forests of Ghana is presented. This simulator considers many aspects of natural forest growth including species-group-specific individual tree diameter growth based on competition, mortality and recruitment. The 687 tree species used in these studies have been aggregated into 13 species groups. The simulator is based on a new individual tree-based distance-dependent diameter increment model. Diameter increment of a tree is predicted by a multiplicative composite function of initial diameter, relative tree dominance index, and (or) categorical site index. The based function of diameter increment on diameter is an extension of a power-exponential growth function. The relative tree dominance index of a subject tree is defined in terms of a new competition index. This index is the sum of the ratios of volume of overtopping competing trees to the volume of the subject tree, where the competitor trees are within a radius of 20 m of the subject tree for large-sized trees and 1.5 m of the subject tree for medium- and small-sized trees. The probability of mortality of a tree is defined in the form of a logistic function based on the explanatory variables of functions of diameter and stand density, including basal area per hectare and volume per hectare for each species group. The total amount of recruitment at 10 cm diameter is predicted as a linear function of stand basal area, stand volume and categorical site variables. It is hoped that the model will provide practical steps to improved natural tropical forest management in Ghana, leading to higher sustainable timber yields.

Using data from temporary and permanent sample plots various functions describing different stand parameter relationships were developed for P. patula growing at Sao Hill, Southern Tanzania. The functions include equations for: a Weibull diameter distribution, a single tree diameter increment, stand basal area, mortality, and height/diameter relationship. Also site index curves based on a Chapman-Richards equation were constructed, and a compatible taper/volume estimation system was developed. The functions were integrated into a micro-computer model SIMUL in BASIC language. The model is capable of estimating saw-log and pulp-log volumes for different spacings and thinning regimes. Inputs to the model are: initial and simulation ages, stocking/ha, stand mean and standard deviation of diameter at breast height (dbh), basal area/ha, site, dominant height, and minimum diameters and lengths of saw-logs and pulplogs. The output gives yearly values/ha for; stocking, total volume, total basal area/ha, means for dbh, height and tree volume, mortality number and volume/ha, and volumes of saw-logs and pulplogs as out-turn from subsequent thinnings and the final clearfelling. Validation with independent data showed that the model works satisfactorily. Experimental runs at different levels of spacing and thinning regimes suggested that the current thinning schedule at Sao Hill is too heavy and results in loss in total volume. The highest utilizable volumes (mainly saw logs) may be obtained by using the current spacing of 2.7 x 2.7m followed by one thinning at the age of about 11 years to leave about 1100 stems/ha, with a rotation age of 25 years. This treatment is also justified economically giving the highest present value at an interest rate of 3%. The current rotation age 15 years (unthinned) for the production of pulp wood only is ideal to produce the required dimensions (10-20 cm diameter) of pulp logs. SIMUL is recommended for use at Sao Hill and the technique may be adopted for other plantation species in Tanzania with new parameter estimates for the equations.

Forest growth models are important to the forestry community because they provide means for predicting future yields and exploring different forest management practices. The purpose of this thesis is to develop an individual tree forest growth model applicable for the province of Nova Scotia. The Acadian forest of Nova Scotia is a prime example a mixed species forest which is best modelled with individual tree models. Individual tree models also permit modelling variable-density management regimes, which are important as the Province investigates new silviculture options. Rather than use the conventional regression techniques, our individual tree growth and yield model was developed using neural networks. The growth and yield model was comprised of three different neural networks: a network for each survivability, diameter increment and height increment. In general, the neural network modelling approach fit the provincial data reasonably well. In order to have a model applicable to each species in the Province, species was included as a model input; the models were able to distinguish between species and to perform nearly as well as species-specific models. It was also found that including site and stocking level indicators as model inputs improved the model. Furthermore, it was found that the GIS-based site quality index developed at UNB could be used as a site indicator rather than land capability. Finally, the trained neural networks were used to create a growth and yield model which would be limited to shorter prediction periods and a larger scale.

Basal area and dominant height growth and survival models incorporating general response to silvicultural treatments for loblolly pine stands were developed using data from various silvicultural experiments across Southern United States. Growth models for treated stands were developed by multiplying base-line growth models with modifier response functions/multipliers accounting for effects of thinning, fertilization, and control of competing vegetation. Chapman-Richards functions were used to model the base-line growth. Separate response functions to mid-rotation thinning and fertilization effects were developed. The thinning response function was based on duration and rate parameters and is sensitive to stand age at the time of thinning, time since thinning, and intensity of thinning. The fertilization response functions were based on Weibull distribution and the magnitude of responses varies with time since application of fertilizers, type of fertilizer elements applied, and rate of application. Response functions were integrated as a multiplier to base-line models. Response to early control of competing vegetation was incorporated into base-line models through multiplier factors. Multiplier factors were calculated based on growth difference between treated and untreated stands. A difference function, derived from differential equation with age, initial stand density, and site index served as the base-line survival model. The survival model was adjusted for thinning treatment by including an additional independent variable that represents thinning intensity. No adjustment was required for survival model in response to fertilization and competing vegetation control. All growth models were unbiased and had adequate performance in predicting basal area and dominant height following treatments. Models were developed to represent general growth trends in response to treatments. The response functions developed here can be viewed as general response functions. / Ph. D.

Following review of several potential methods, growth tables for five defined coastal Virginia forest types were derived graphically by employing Gehrhardt's formula and published normal-yield information. The resultant tables depict the current periodic annual cubic-foot growth per acre expected of coastal Virginia forests on average site, by age class and cubic-foot stocking. / Master of Science

The ongoing drought in the US Southwest (SW) has led to particularly large and severe wildfires, tree die-off events, insect outbreaks, and increased forest stress levels. These disturbances underscore the vulnerabilities of SW dry conifer forests to climate change and past land-uses. Climate projections show a clear upward trend in regional temperatures, which will lead to accelerated heat-related stressors and disturbances in the coming decades. Already, more than 20% of the dry conifer forests of the SW have been severely impacted. This number is likely to grow, but we lack a clear picture of where, when, and to what degree other forest areas will be affected. Here, I apply dendroecological methods to evaluate patterns and processes that might determine greater or lesser vulnerability in dry conifer forests. Much of this work stems from critical concerns voiced by the Navajo Forestry Department (NFD). Long-term and representative data are necessary for the NFD, as they are responsible for closely managing over 250,000 hectares of forests and woodlands for the traditional products and ecosystem services that their forests provide for the Navajo people. The first study takes a multi-century perspective on changing fire regimes across Navajo forests, and places current forest structure and recent severe events in a long-term context. We found that surface fires were frequent across the landscape from at least the late-1500s until 1880. Navajo settlement of the area began to affect the fire regimes with added small fires in some areas beginning in 1700. By 1832, the rise of traditional pastoralist practices and transhumant migrations reduced fire activity in areas of greater use. Conditions changed following the establishment of the Navajo reservation in 1868, as livestock herds grew rapidly and initiated a near-synchronous and widespread collapse of fire regimes across the study area by 1880. The legacies of this change in land use are greater forest densities and higher fuel loads in some areas, raising the vulnerability of the forest to more severe fires. The second study assesses one of the most dramatic long-term consequences of recent high-severity fires in the SW, the rapid post-fire transition of dry conifer forest to oak-dominated shrubfields. To assess probable successional trajectories and interactions with climate change of recently converted forests, we reconstructed the age structures and fire regimes of some of the largest and oldest shrubfields in the Jemez Mountains of northern New Mexico. We found that shrubfields are a resilient configuration to drought and fire, historically burning at the same rates and under similar climate as dry conifer forests. Dense shrubfields pose a significant challenge to conifer recruitment from competition effects, with our sites persisting for over 100 years in the absence of burning and through periods of favorable climate to conifers. Given future warming favoring oak over pine, and projected trends in fire activity and high-severity fire behavior, we expect much more forest area to convert to shrubfield, especially in the absence of restoration efforts to reduce crown fire potential.Finally, we evaluate landscape-scale variability in tree growth response to regional climate across the Navajo forest. Projections of climate-induced forest decline often omit upper-elevation and mesic sites because they are not represented in regional tree-ring chronology networks. We found that these stands had much lower response to 20th century droughts than mid to lower elevation stands, and that targeted tree-ring sites are consistently more correlated with regional climate. However, as temperature-driven atmospheric moisture demand has remained above average since ~1997 in the study area, the upper-elevation trees are now nearly as responsive to regional climate as lower elevation xeric sites, probably due to increased moisture limitations. Recent warming has thus synchronized tree growth to an unprecedented extent across this large landscape and regionally.

The main goal of this thesis was to improve our understanding of the long-term effects of establishment treatments and climate change on lodgepole pine and white spruce growth in the western boreal forests. My dissertation also investigated the combined effects of climate and competition on white spruce and trembling aspen growth in boreal mixtures. In the first part of the thesis I evaluated the effects of site preparation treatments on growth of lodgepole pine and white spruce in north-eastern British Columbia. Results indicate that mechanical site preparation can provide yield gains of up-to 10 percent for pine and spruce at 60 and 80 years, respectively. These stands are showing a Type 1 growth response which implies that the treatment effect will eventually cease 90-100 years after planting. In the second part of the thesis I explored pine and spruce growth in relation to past climate and site preparation. Results indicate that up-to 45% and 37% of the respective variation in spruce and pine growth can be explained by selected climatic variables. Future projections indicated that height growth of young pine plantations in the sub-boreal zone could benefit (in the short term) from longer growing seasons by up-to 12% on untreated stands. Untreated young spruce plantations in the boreal zone may suffer height growth decreases of up-to 10% due to increased drought-stress. Vegetation control and mechanical site preparation treatments appear to mitigate effects of climate change to some extent. In the third part of the thesis I explored the combined effects of climate and trembling aspen competition on spruce and aspen growth using data from a long-term study in the boreal zone. Results indicate that climate variables and initial size of the tree can account for significant portions of the annual growth of spruce. Including an estimate of aspen competition in the equations improved the predictive ability of these models. Evidence of the inter-annual variability in aspen competitiveness on spruce and aspen growth indicates that the stress-gradient hypothesis can be applied in boreal mixedwood forests. / Forest Biology and Management

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Submitted by Mario BC (mario@bc.ufrpe.br) on 2016-07-08T13:15:47Z No. of bitstreams: 1 Najara de Moura Fontenele.pdf: 1210360 bytes, checksum: 9ede2a655da04fe9b34050590329d2e4 (MD5) / Made available in DSpace on 2016-07-08T13:15:47Z (GMT). No. of bitstreams: 1 Najara de Moura Fontenele.pdf: 1210360 bytes, checksum: 9ede2a655da04fe9b34050590329d2e4 (MD5) Previous issue date: 2016-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The aim of this work was compare and evaluate the productivity, mean annual increment (MAI), survival and mortality of 15 clones of Eucalyptus conducted in two systems: tall trees and coppice; recommend which clones have higher volumetric yields to supply the energetic matrix of the region; define the best system; compare the volume of tall trees regime with coppice and native vegetation; to define the technical rotation age; perform financial analysis of coppice; compare energy sources used in the region and indicate the clone most economically viable. The experiment was conducted in Araripe Experimental Station of the Agronomic Institute of Pernambuco (IPA) in Araripina - PE. It was tested 15 treatments represented by clones of the Eucalyptus hybrids with four repetitions in spacing of 3.0 m x 2.0 m, with 25 plants in the useful area of the plot. The trees were rigorously measured by the Smalian method in both systems. The statistical procedure was performed by a completely randomized design. The treatment means were compared by the Scott-Knott test at 5% probability that separated the 15 clones into three groups. The highest production was obtained with the clone C39 (E. urophylla hybrid) with 72.99 m3/ha, but this volume in coppice was lower than in tall trees. The technical rotation age was 60 months. According to the financial analysis of the systems, it was decided that the tall trees at 60 months has increased revenue and volume when compared to coppice. Both presented better results than the native forest. The net present value (NPV) was positive in four considered interest rates. Eucalyptus spp. compared to sustainable forest management plans of Caatinga (PFM) has increased productivity in a shorter rotation, it is economically and environmentally viable because its use as an energy source reduces the use of native vegetation for the same purpose, thus reducing the devastation of the native vegetation. / Objetivou-se neste trabalho comparar e avaliar as produtividades, incremento médio anual, sobrevivência e mortalidade de 15 clones de eucaliptos nos sistemas de condução por alto fuste e talhadia; recomendar quais clones possuem maiores rendimentos volumétricos para suprir a matriz energética da região; definir o melhor sistema de condução; comparar o volume do regime de alto fuste com a talhadia e com a vegetação nativa; definir a idade de rotação técnica na talhadia; realizar análise financeira da talhadia; comparar fontes energéticas utilizadas na região e indicar a mais economicamente viável. O experimento foi conduzido na Estação Experimental do Araripe do Instituto Agronômico de Pernambuco (IPA), em Araripina – PE. Foram testados 15 tratamentos representados por clones de híbridos de eucaliptos com 4 repetições em espaçamento de 3,0 m x 2,0 m, com 25 plantas na área útil da parcela. As árvores foram cubadas rigorosamente pelo método de Smalian nos dois sistemas. O procedimento estatístico foi realizado por meio de um delineamento inteiramente casualizado. As médias dos tratamentos foram comparadas pelo teste de Scott-Knott ao nível de 5% de probabilidade que separou os 15 clones em três grupos. A maior produção foi obtida com o clone C39 (Híbrido de E. urophylla) com 72,99 m3/ha, porém este volume em talhadia foi inferior ao de alto fuste com 166,17 m3/ha. A idade de rotação técnica foi de 60 meses. De acordo com a análise financeira dos sistemas, foi observado que o alto fuste aos 60 meses possui maior receita e volume quando comparado a talhadia. Ambos foram superiores à vegetação nativa. O Valor Presente Líquido (VPL) foi positivo em quatro taxas de juros consideradas. O Eucalyptus spp. nos sistemas de alto fuste e talhadia quando comparado aos Planos de manejo florestal sustentado da Caatinga (PFMS) possui maior produção e em menor tempo de rotação, é viável economicamente e ambientalmente, pois seu uso como fonte energética diminui o uso da vegetação nativa para o mesmo fim, atenuando assim sua devastação.