The boreal forest is confined to the Northern Hemisphere and is the most continuous and extensive forest in the world. In North America boreal forest extends from the Pacific to Atlantic coast spanning over 10° latitude. White spruce (Picea glauca (Moench) Voss), black spruce (P. mariana (Mill.) B.S.P.), and trembling aspen (Populus tremuloides Michx.) are among the dominant tree species. Black spruce and trembling aspen may form pure stands and occupy similar sites as their edaphic amplitudes overlap; however, spruce is rare on water-deficient sites and aspen does not tolerate excess water. Despite many studies conducted in the North American boreal forest, little is known about relationships between the boreal understory vegetation and softwood or hardwood canopy species in different climate regions. Furthermore, the variation in species diversity and succession between the stands dominated by coniferous trees and those dominated by broadleaved trees within the same region is unknown. The objectives of this study are to determine (1) the difference in the species diversity and floristic composition of understory vegetation between black spruce and trembling aspen stands within the same climatic region, and (2) how the species diversity and floristic composition of understory vegetation in each stand type vary with climate, and soil moisture and soil nutrient conditions.

The three major components in the site classification of the biogeoclimatic ecosystem classification system are: climatic regimes, soil moisture regimes (SMRs) and soil nutrient regimes (SNRs). Both SMRs and SNRs can be identified in the field using soil characteristics and indicator plants. In the case of SMRs a quantitative classification was also developed that allow comparison of SMRs in different subzones. However, similar quantitative classification has not yet been developed for SNRs. This pamphlet summarizes and compares the results of several regional studies conducted in different biogeclimatic zones. Each of theses studies aimes to develop a quantitative SNR classification (Table 1). The comparison will examine: (1) how well the field-based classification matches quantitative classification, and (2) which direct measures distinguish best between field-identified SNRs.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This study was developed in Serra do Sudeste and Encosta do Sudeste physiographic regions of Rio Grande do Sul state. The objective was to identify the physical and hydraulic soil properties related to forest yield sites in two distinct areas, including physical-structural properties and soil available water capacity (AW) of Argissolo Vermelho-Amarelo Distrófico típico, Argissolo Vermelho-Amarelo Distrófico latossólico (ARG) and Neossolo Quartzarênico Órtico típico (NEO), as well as perform parameterization of the Physiological Principles to Predicting Growth model (3-PG). In the two sites with high (ARG) and low (NEO) productive potential capacity, the growth and productivity of stands characterization was based on data from forest inventories and from destructive sampling and cube by Smalian method of 30 trees of medium quadratic mean diameter (dg). Soil properties were determined in undisturbed and disturbed soil samples, taken from 0.00-0.10, 0.10-0.20, 0.20-0.40, 0.40-0.60, 0.60-0.80, 0.80-1.00 e 1.00-1.20 m soil depths, in 12 sampling points. Eucalyptus yield was different in the ARG (from clay loam to clay texture) and NEO (sandy texture) areas, characterized by mean values of 373.9 m³ ha-1 and 272.3 m³ ha-1, for 89-months-old stands. In the ARG, AW ranged from 0.100 up to 0.304 cm3 cm-3. The highest soil bulk density (BD; 1.64 Mg m-3) was observed in the 0.00-0.10 and 0.10-0.20 m soil layers. Multiple regression analysis with BD and macroporosity (Mac) of the 0.40-0.60 m soil layer had r2 ~ 0.22 in variance estimation of mean annual volume increment (MAIV). Soil air permeability (Kar) was the main soil property related to productivity in ARG stands. In the NEO (sandy texture) areas, AW ranged from 0.025 up to 0.04 cm3 cm-3 and BD had the highest values (1.60 Mg m-3) in the 0.80-1.00 m soil layer. The BD determined from surface up to 0.60 m explained 14% of MAIV variance and 27% of the total height variance (h). Multiple regression that included BD and Kar of the surface layers explained around 23% of mean annual stem biomass increment (MAISB) variance. In the parameterization of the model 3-PG we obtained estimates characterized by r2 higher than 0.9 for the wood volume with bark (V; m3 ha-1), wood biomass (BL; Mg ha-3) and total height (h), and equal to 0.78 for the diameter at breast high (dbh; cm). The statistical efficiency described by the Nash-Sutcliffe indicator had values higher than 0.8, while the PBIAS indicator showed a tendency of underestimation of less than 12%. In the validation process of the model, performed in unused portions in the parameterization, the results were similar to those obtained in the efficiency evaluation, except for the variable dbh, which was underestimated at the lowest ages. The results showed that the soils with high water availability have their physical quality, based on productivity, determined by the properties that represent the flow of solutes and gases, while coarse soils, highly drainable, have their productive capacity inversely related to BD. The 3-PG model was efficient and accurate for the estimation of E. saligna productivity in the observed climatic conditions, with a higher sensitivity for coarse textured soils. / O presente estudo foi realizado nas regiões fisiográficas da Serra do Sudeste e Encosta do Sudeste do estado do Rio Grande do Sul. O objetivo do estudo foi identificar as propriedades físico-hídricas dos solos relacionadas à produtividade dos sítios florestais, distintos quanto às propriedades físico-estruturais e à água disponível (AD), caracterizados pela presença de Argissolo Vermelho-Amarelo Distrófico típico e Argissolo Vermelho-Amarelo Distrófico latossólico (ARG) e de Neossolo Quartzarênico Órticos típicos (NEO), e ainda, realizar a parametrização do modelo Physiological Principles to Predicted Growth (3-PG). A caracterização do crescimento e produtividade dos povoamentos foi realizada por meio de inventários florestais e pela amostragem destrutiva e cubagem, pelo método de Smalian, de 30 árvores de diâmetro médio quadrático (dg). As propriedades físico-hídricas dos solos foram determinadas em amostras de solos de estrutura preservada e alterada, coletadas nas camadas de 0,00-0,10, 0,10-0,20, 0,20-0,40, 0,40-0,60, 0,60-0,80, 0,80-1,00 e 1,00-1,20 m, em 12 pontos amostrais. A produtividade foi distinta nas áreas ARG e NEO, com média de 373,9 m³ ha-1 e 272,3 m3 ha-1, aos 89 meses de idade. Nos solos ARG (classe textural franco arenosa a muito argilosa), a AD variou entre 0,100 e 0,304 m3 m-3, e os maiores valores de densidade do solo (Ds; 1,64 Mg m-3) foram observados nas camadas 0,00-0,10 e 0,10-0,20 m. Pela análise de regressão múltipla a Ds e a macroporosidade (Mac) da camada 0,40-0,60 m tiveram eficiência estatística com r2 ~ 0,22 na estimativa da variância do incremento médio anual em volume (IMAV). A permeabilidade do solo ao ar (Kar) foi a principal propriedade do solo relacionada à produtividade dos povoamentos das áreas ARG. Nas áreas NEO (classe textural areia) a AD variou entre 0,025 e 0,04 m3 m-3 e a maior Ds foi observada na camada 0,80-1,00 m (1,60 Mg m-3). A Ds determinada nas camadas acima de 0,60 m de profundidade explicou 14% da variância observada no IMAV e 27% da variância da altura total (h). Pela regressão múltipla a Ds e a Kar das camadas superficiais explicaram em torno de 23% da variância observada no incremento médio anual em biomassa de lenho (IMABL). Na parametrização do modelo 3-PG foram obtidas estimativas caracterizadas por r2 superior a 0,9 para o volume com casca (V; m3 ha-1), biomassa de lenho (BL; Mg ha-3) e altura total (h; m), e igual a 0,78 para o dap (cm). O indicador estatístico Nash-Sutcliffe teve valores superiores a 0,8, enquanto o indicador Bias percentual (PBIAS) apontou tendência de subestimativa inferior a 12%. No processo de validação do modelo, realizado em parcelas não utilizadas na parametrização, os resultados foram semelhantes aos obtidos na avaliação da eficiência, com exceção para a variável dap, que foi subestimada nas menores idades. Solos com alta disponibilidade de água podem ter sua qualidade física, com base na produtividade, determinada pelas propriedades que representam o fluxo de solutos e gases, enquanto solos de textura grossa, altamente drenáveis, têm sua capacidade produtiva inversamente relacionada a Ds. O modelo 3-PG foi eficiente e preciso para a estimativa da produtividade do E. saligna nas condições climáticas observadas, com maior sensibilidade para os solos de textura grossa.

Submitted by (lucia.rodrigues@ufrpe.br) on 2016-09-01T14:49:07Z No. of bitstreams: 1 Rubeni Cunha dos Santos.pdf: 2841897 bytes, checksum: 50ded5df9e65f22470ec0b1cf72a74bd (MD5) / Made available in DSpace on 2016-09-01T14:49:07Z (GMT). No. of bitstreams: 1 Rubeni Cunha dos Santos.pdf: 2841897 bytes, checksum: 50ded5df9e65f22470ec0b1cf72a74bd (MD5) Previous issue date: 2012-02-24 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / At this study were compared the mathematical models adjusted by regression analysis to define the productive capacity using curves site index for hybrid clones of Eucalyptus ssp., In the Araripe, Pernambuco. The study area was located at the Experimental Station of the Agronomic Institute of Pernambuco - IPA, located in the municipality of Araripina, Pernambuco. The data were measured from 45 permanent plots with 15 treatments (clones of Eucalyptus sp.) in three repetitions, with a spacing of 3 x 2 m plot area was 294 m2, with util area of 150 m2, in a block design The first measurement was performed at the time two months after planting to verify the survival, after the planting all plots were measured every six months, with measurements at 2, 6, 12, 18, 24, 30 , 36, 42, 48, 54, 60, 66, 72, 78, 84, 90 months. For each measurement were recorded the tree total height and the diameter at the breast height (DBH) of all trees. However this work did not consider the first four measures, because the plants were still young and therefore had not yet competition and also influence of the treatments were suffering forestry. Three models were to perform the analysis of covariance, Five linear and five nonlinear models were adjusted for the data collected, age and height . The adjusted models were evaluated through the following statistics and precision adjustment: adjusted coefficient of determination (R2aj), coefficient of variation in percentage, and residual graphical analysis in percentage. The differences in slope detected by analysis of covariance indicated, accurately among the fifteen clones tested, indicating the existence of nine groups with different growth patterns. It was considered necessary to adjust the nine sets of site index curves with reference age of 72 months, with an interval of 2 meters among the curves. All equations tested to estimate the growth in height according to age showed a good fit, especially for nonlinear models. For the establishment of the nine sets of site index curves, we selected the Schumacher model, for simplicity and to estimate the heights of trees and with only two parameters and, especially, for having made some better residual graphical distributions. / Neste trabalho foram comparados modelos matemáticos ajustados por análise de regressão para definição da capacidade produtiva por meio de curvas de índice de sítio, para clones de Eucalyptus spp. na Chapada do Araripe, em Pernambuco. A área de estudo estava localizada na Estação Experimental do Instituto Agronômico de Pernambuco – IPA, no município de Araripina, Pernambuco. Os dados foram medidos em 45 parcelas permanentes distribuídas com 15 tratamentos (clones de Eucalyptus spp.) em 3 repetições, com espaçamento de 3 x 2 m e área de 294 m² por parcela, com área útil de 150 m2 dispostas em delineamento casualizado em blocos. A primeira medição em altura foi realizada aos dois meses após o plantio quando foi avaliada a sobrevivência, posteriormente todas as parcelas foram mensuradas a cada seis meses, tendo ao final do experimento as medidas aos 2, 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78, 84, 90 meses. Em cada medição foram registrados a altura total e o diâmetro a altura do peito (DAP) de todas as plantas presentes na área útil de cada parcela. Contudo neste trabalho não foram utilizadas as quatro primeiras medidas, pois as plantas ainda estavam jovens e, consequentemente, ainda não havia competição e também ainda estavam sofrendo influência dos tratamentos silviculturais. Foram selecionados três modelos e o que obteve os melhores resultados foram escolhidos para se realizar a análise de covariância .Foram ajustados 5 modelos lineares e 5 modelos não lineares para os pares de dados de idade e altura coletados, o quais foram avaliados por meio das estatísticas de ajuste e precisão: coeficiente de determinação ajustado (R2aj), coeficiente de variação em porcentagem (CV%) e análise gráfica de resíduos em porcentagem. As diferenças de inclinação detectadas pela análise de covariância indicaram, de forma precisa, entre os quinze clones testados, 9 grupos com diferentes padrões de crescimento. Foi considerado necessário o ajuste de nove conjuntos de curvas de índice de sítio, com idade de referência de 72 meses, com intervalo de 2 metros entre as curvas. Todas as equações testadas para estimar o crescimento em altura em função da idade apresentaram bom ajuste, com destaque para os modelos não lineares. Para o estabelecimento dos nove conjuntos de curvas de índice de sítio, foi selecionado o modelo de Schumacher, pelas estatísticas apresentada, pela simplicidade e por estimar bem as alturas das árvores com apenas dois parâmetros apresentando as melhores distribuições gráficas dos resíduos.

Two watersheds on the southern end of Havens State Wildlife Management Area, Roanoke County, Virginia, were sampled for vascular plant species richness. Two-hundred and forty-eight species were identified. Three methods of sampling for species richness in eastern forests were compared: timed-search meanders, belt transects, and plots. Meanders and transects located more species in the same amount of time as plots. Plot sampling encompassed only two-thirds of the richness known from the site. Species-area and species-effort relationships were described by exponential models (number of species = In (area + 1), and number of species = In (time + 1)). Models were used to predict numbers of species which might have been found had more area been sampled or had more time been spent searching. Species-area models yielded more conservative, and probably more accurate, predictions than species-time models. Predictions of species numbers were reasonable for areas as large as 60 ha, but were rather large for areas the size of Havens (2800 ha). Sufficiency of search effort was judged using species-area and species-effort curves. However, it was difficult to tell whether the curves approached horizontal or not. Therefore, this was not a good technique to judge sampling adequacy. Species composition observed by each of the three methods was different. Composition of species lists was 65% similar between meanders and transects, and only 51-58% similar between plots and other methods. These figures were within an expected range. A combination of two methods or repeated meanders was recommended in order to identify a higher proportion of the species present. Seasonal and observer differences, and the effect of learning and taxonomy on richness estimates were discussed. / Master of Science

Thesis (PhD(For))--Stellenbosch University, 2012. / The subtropical ecosystem of the Zululand coastal plain is prized by the South African commercial plantation forestry industry for its rapid clonal Eucalyptus growth, short rotations (6 to 7 years) and high yields. This region is typified by sandy soils that are low in clay and organic matter, have small nutrient reserves and are poorly buffered against nutrient loss. The subtropical climate induces rapid decomposition of residues and tree litter resulting in small litter nutrient pools and rapid nutrient release into the soil, particularly after clearfelling. A combination of large nutrient demands through rapid growth, rapid nutrient turnover and small soil nutrient reserves implies that sites in this region are sensitive and may be at risk of nutrient decline under intensive management. The work in this study set out to determine the risk of nutrient depletion through harvesting and residue management on a site within the Zululand region, to assess nutritional sustainability and the risk of yield decline in successive rotations. Some bulk biogeochemical cycling processes of macro-nutrients nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) were assessed, and assessments also included sodium (Na). An existing Eucalyptus stand was clearfelled and treatments were imposed on the residues after broadcasting to simulate various levels of nutrient loss through levels of harvesting intensity and residue management. These included residue burning (Burn), residue retention (No-Burn), fertilisation (stem wood nutrient replacement), whole tree harvesting and residue doubling. Outer blocks of the stand were not felled, but included as replicates of an undisturbed standing crop treatment. Biogeochemical nutrient cycling processes were assessed primarily in the standing crop, Burn and No-Burn treatments, in the assumption that these represented the furthest extremes of nutrient loss. Data collection commenced a year prior to clearfelling and continued to two years and six months after planting with key data collection over a 20.1 month period from clearfelling to canopy closure (one year after planting). Water related nutrient pools and fluxes were assessed as atmospheric deposition (bulk rainfall, throughfall and stemflow) and gravitational leaching to 1m soil depth. Drainage fluxes were predicted using the Hydrus model and real-time soil moisture data. Zero tension lysimeters collected soil solution for chemical analysis. Sequential coring in the 0 to 30cm soil layer was used to determine in situ soil N mineralisation. Soil chemical and physical properties were assessed over the first meter of soil at clearfelling and new crop canopy closure to determine soil nutrient pools sizes. Biomass nutrient fluxes were assessed from litterfall, residue and litter decomposition, and above ground accretion into the tree biomass. Leaching and N mineralisation were monitored in the No-Burn, Burn and standing crop treatments only. Atmospheric deposition, while variable, was shown to be responsible for large quantities of nutrients added to the Eucalyptus stand. Nitrogen and K additions were relatively high, but within ranges reported in previous studies. Rapid tree canopy expansion and subsequent soil water utilisation in the standing crop permitted little water to drain beyond 1m resulting in small leaching losses despite a sandy well drained soil. Further leaching beyond this depth was unlikely under the conditions during the study period. Mineralisation and immobilisation of N also remained low with net immobilisation occurring. The standing crop was shown to be a relatively stable system that, outside of extreme climatic events, had a relatively balanced or positive nutrient budget (i.e. nutrient inputs minus outputs). Large quantities of nutrients were removed with stem-wood-only harvesting in the No-Burn treatment leaving substantial amounts on the soil surface in the harvest residues. Whole tree removal increased losses of all nutrients resulting in the largest losses of P and base cations compared to all other treatments. This was mostly due to high nutrient concentrations in the removed bark. Loss of N in the Burn treatment exceeded whole tree N losses through combustion of N held in the harvest residues and litter layer. The majority of K leached from the residues prior to burning and a relatively small fraction of the base cations were lost from the partially decomposed residues during burning. Ash containing substantial amounts of Ca and relatively large amounts of N and Mg remained after burning. Surface soil Ca and Mg was significantly increased by the ash which moved into the soil with rainfall directly after burning. Rapid soil moisture recharge occurred within a few months after clearfelling, increasing leaching from the upper 50cm of soil. Clearfelling increased net N mineralisation rates, increasing mobile NO3-N ions in the soil surface layers. Nitrate concentration peaked and K concentration dipped in the upper soil layers of the Burn treatment directly after burning. Deep drainage and leaching (beyond 1m depth) over the 20.1 month period was, however, not significantly different between the Burn and No-Burn treatments. Rapid soil moisture depletion and nutrient uptake with new crop growth reduced leaching fluxes to levels similar to the standing crop by six months after planting. Taking the full rotation into account, clearfelling induced a short-lived spike in N and cation leaching compared with the low leaching losses in the undisturbed standing crop. Soil N mineralisation over the 20.1 month period in the burnt treatment was half that of the No-Burn treatment. Growth and nutrient accumulation was significantly higher in the fertilised treatment than in other treatments up to 2.5 years of age. Growth in the Burn treatment was greatest compared to other treatments during the first few months, but slowed thereafter. No significant growth differences were found between all other treatments from a year to 2.5 years after planting. Early growth was therefore apparently not limited by N supply despite large differences in N mineralisation between Burn and No-Burn. Foliar vector analysis indicated that fertilisation improved growth initially through increased foliar N and P at six months after planting followed by Mg and Ca at one year. The Burn treatment was not nutrient limited. These growth results contrasted with similar international research on sandy tropical sites where growth was reduced after residue removal and increased after residue doubling. The combined nutrients released from pools in the litter layer or ash and soil in addition to atmospheric inputs were sufficient to provide most nutrients required to maintain similar growth rates across all treatments. This demonstrated the importance of residue derived nutrients to early growth nutrient supply. Reduced N mineralisation through a lack of substrate may limit N supply later in the rotation where residue had been removed. Construction of a nutrient budget for the system revealed that high levels of atmospheric inputs have the potential to partially replenish a large proportion N, K, and Ca lost during clearfelling, provided losses are constrained to stemwood removal only. However, loss of Mg that occurred primarily through leaching may not be replaced under the low Mg inputs recorded in this study. Larger nutrient removals (i.e. stemwood plus other plant parts) placed a heavier reliance on the small soil nutrient pools at this site which can limit future productivity. More intense harvesting and residue management practices dramatically increased the risk of nutrient depletion. Losses of specific nutrients depended on a combination of clearfelling biomass removal, residue burning and subsequent leaching. Nitrogen losses due to harvesting and burning were more substantial than those due to leaching. Mg and K losses depended most strongly on the time after clearfelling before re-establishment of the new crop and rainfall patterns, while Ca and P losses depended directly on the amount of biomass removed. Depletion risk was the greatest for Mg and K through rapid leaching, even after stem wood only removal. Deep root uptake and deep drainage with associated cation loss needs to be investigated further to quantify ecosystem losses and recovery of cations displaced beyond 1m. Atmospheric deposition is one of major factors countering nutrient losses. However, atmospheric inputs may not be reliable as these may lessen in future through pollution control legislation and climate change. Changes in growth rate under poor nutrient management practices are small and difficult to detect relative to the large impacts of changing weather patterns (drought), wildfire and pest and disease. This makes it difficult to prove nutrient related growth decline. It may be possible that improvements in genetics, silvicultural technologies and atmospheric inputs may also be masking site decline (in general) and in part explain the lack of evidence of a growth reduction in the region. As the poorly buffered sandy soils on the Zululand Coast are at risk of nutrient depletion under the short rotation, high productivity stands, it may be necessary to stipulate more conservative harvesting and residue management practices. A more conservative stem-wood only harvesting regime is recommended, retaining all residues on site. Residue burning should be avoided if N losses become a concern. The length of the inter-rotation period must be kept short to reduce cation leaching losses. Site nutrient pools need to be monitored and cations may eventually need to be replenished through application of fertilisers or ash residues from pulp mills. Management practices therefore need to be chosen based on the specific high risk nutrients in order to maintain a sustainable nutrient supply to current and future plantation grown Eucalyptus.

隨著電腦和網際網路的快速發展，此兩者的結合，提供了許多的資訊商機。其中一項便是遠距教學的興起。遠距教學由最早的函授逐漸轉為以目前流行的Web-based資訊系統為教學平台。而為了讓遠距教學的推廣更加有效，本研究試圖瞭解學習者的心態，提出一個能夠有效解釋和預測學習者行為的模式，以提供相關研究人員參考。 本研究參考歷經實證的科技接受模式（Technology Acceptance Model），以此為基礎，發展出研究架構。並回顧相關網站品質的文獻，建構出屬於遠距教學的網站品質，並以此為外部變數，來推測影響使用者的行為。研究結果發現，本研究所使用的網站品質中，四個構面，以教材品質影響行為意圖的效用最大，其次是其次為服務互動，以及介面設計，最後是功能性。

Trembling aspen (Populus tremuloides Michx.) is one of the most common tree species in the boreal and temperate forests of North America. It grows on many different sites and associates with a variety of tree species. In BC, aspen is frequent throughout all submontane and montane continental forested zones. Relationships between environmental factors and forest productivity have been the subjects of many studies. Most of these studies, using various topographic, soil, physical and chemical properties as independent variables, had limited success in accounting for the variation in SI over a large geographic area. The objectives of this study were (1) to quantify relationships between aspen SI and environmental factors at two spatial scales, and (2) to develop predictive SI models from easily measurable environmental factors.

The influence of tree species on forest soils has been the subject of study for at least a century. Of particular interest have been western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn ex D. Don) – two of the most common tree species in coastal and southern British Columbia, but each with a different nutrient amplitude. It has generally been found that acid, mycogeneous Mor humus forms develop in hemlock stands, while less acid and more zoogenous Mormoder, Moder, or even Mull humus forms develop in redcedar stands. The objective of this study was to determine the influence of hemlock and redcedar, growing separately and together, on forest floor nutrient properties. The questions addressed were: (1) does each stand type have unique forest floor nutrient properties? and (2) can any forest floor nutrient property discriminate between stand types?

No description available.