The woodwasp Sirex noctilio is one of the most serious invasive pests of Pinus plantations in the southern hemisphere. Extensive control programs have been developed to manage this pest, of which biological control has been a major component. This thesis examined the factors that could influence the control of S. noctilio in South Africa. A critical comparison of S. noctilio infestations and control efforts throughout the southern hemisphere revealed that control has not been uniformly effective, and local adaptation of control strategies is likely required as S. noctilio moves to new areas. The parasitic nematode Deladenus siricidicola is considered the primary biological control agent of S. noctilio. This nematode also feeds on the fungal symbiont of S. noctilio, Amylostereum areolatum. Possible factors influencing the success of this nematode in the summer rainfall areas of South Africa were examined. Data from a field trial revealed that moisture content of the wood influences inoculation success and this is influenced by the time of inoculation and the section of the tree inoculated. Laboratory-based assays revealed that incompatibility between the strain of A. areolatum and D. siricidicola was unlikely to be the cause of low inoculation success with the nematode, but that artificial inoculations could be affected by competition of A. areolatum with sapstain fungi. The parasitic wasp Ibalia leucospoides is another biological agent for S. noctilio. Mitochondrial and nuclear DNA sequence data reflected the extensive introduction of I. leucospoides into the southern hemisphere, followed by genetic bottlenecks that fixed only a few haplotypes in the introduced populations. Promoting awareness of S. noctilio in the forestry community has also been an important component of the control strategy. Data from a survey questionnaire showed that the awareness campaign had been generally successful, but the lack of basic knowledge to identify S. noctilio and its symptoms and the poor reach of the awareness media to some sectors of the forestry community, was of concern. This thesis has contributed towards understanding the factors that influence the control of S. noctilio in South Africa, with relevance to other regions where S. noctilio has been introduced. / Thesis (PhD)--University of Pretoria, 2010. / Zoology and Entomology / Unrestricted

South Africa lags behind the rest of the world with regard to the availability of allometric biomass information. There is a complete lack of site specific allometric data for Pinus radiata in the southern Cape region, impeding investment in the renewable energy sector. This shortcoming was addressed by developing up-scalable, single tree biomass models. These models quantify the aboveground biomass of rotation age P. radiata grown in the southern Cape across a range of site conditions. The models use diameter at breast height (DBH) to predict the aboveground component biomass. A nutrient loss risk potential was assigned to each biomass component. Nineteen trees were destructively harvested using a full fresh weight sampling approach. Basic density was determined using a water displacement method, while Newton’s volume equation was used for stemwood volume determination. Log linear models were simultaneously regressed through seemingly unrelated regression (SUR) using the “Systemfit” R statistical package to force component additivity. A categorical variable was applied to the models, grouping the data into two Site Index (SI) based categories, namely “Low” SI and “Medium to High” SI, to account for inter-site variability. The corrected Akaike Information Criteria (AICc) and coefficient of determination (R2) was used to determine the goodness of fit of the models. The McElroy R2 for the SUR system was 0.95. Biomass models were developed that are able to predict various tree component masses at high levels of certainty within site and stand attribute ranges similar to this study. The importance of accurate, site specific wood basic density was demonstrated by its substantial weighting on stem and hence total biomass. Results showed that the stemwood mean basic density range was between 503 kg m-3 and 517 kg m-3 for the “Low” SI sites and 458 kg m-3 for the “Medium to High” SI sites. Site quality can have a major impact on the models, particularly on poorer sites where stemwood production is proportionally less than other tree components. Total aboveground biomass was estimated to range between 58.61 odt ha-1 and 70.85 odt ha-1 for “Low” SI sites, and 185.31 odt ha-1 to 266.58 odt ha-1 for “Medium to High” SI sites. Stemwood biomass accounted for 65% of the total aboveground biomass for “Low” SI sites and 70% for “Medium to High” SI sites.

The objectives of this study were to study wood property variation in Pinus patula from different physiographic sites, the interrelationship between wood properties and the effects of some forest site factors on wood properties and their within-tree variation. The wood properties considered were density, transverse shrinkage, grain angle and stiffness (modulus of elasticity). Ten trees were taken from each of seventeen sites selected during a previous study of soil ecology and tree growth patterns on the escarpment of Mpumalanga in South Africa. This is a complex physiographic region with several different growth sites within a relatively small geographical area. The key finding of the study was that the effect of radial distance from the pith (i.e. the age of the tree) was highly significant and accounted for most of the variation of the trees sampled. Although the effect of site on the selected wood properties was highly significant, its effect accounted for a relatively small percentage of the total variation in each case. Consequently, solid wood processors must take into account the large variation within a tree when implementing strategies to minimise the downgrade of timber as result of excessive board distortion and/or inferior strength. There were significant correlations between wood density and density slope, radial shrinkage, shrinkage ratio and stiffness and also significant correlations between wood stiffness and density slope and radial shrinkage. Density and grain angle both showed significant correlations with the most important climatic factors. ‘Growth days’ (which is an index reflecting the number of days per year when soil moisture is not a limiting factor for plant growth) was identified as one of the principal growth factors influencing the selected wood properties, because of it’s strong relationships with wood density, density slope, grain angle and stiffness. Regression models were developed to predict wood density and grain angle from growth variables. The results show that those wood properties that correlate with geographic representable site variables can be included in site classification and evaluation systems, to assist in predicting growth in terms of volume yield and wood quality.

Pinus patula is the single most important commercial plantation forest tree species in South Africa. It accounts for 52% approximately (700,000 ha) of total commercial plantation area in the country and is utilised for saw logs and pulp and paper production. P. patula is a tropical pine species indigenous to Mexico. Excellent ex situ conservation and range-wide provenance trials have been established for P. patula in South Africa and South America. These highly organised trials provide the opportunity to perform association genetic studies with the long term aim to identify trait linked markers for future molecular improvement of P. patula. In this study, the first gene-based assessment of allelic diversity in P. patula was performed. This pilot study focused on two cellulose biosynthetic genes as representatives of wood formation genes and assayed molecular evolution parameters such as nucleotide diversity, allelic diversity and linkage disequilibrium (LD) in a species-wide reference population of P. patula. Two novel cellulose synthase (CesA) genes were isolated and characterised in P. patula. One of these genes, PpCesA1, is putatively involved in the biosynthesis of secondary cell walls of tissues such as xylem (wood), while the other, PpCesA2 is proposed to be associated with primary cell wall formation in rapidly growing tissue types. The genomic DNA copies of PpCesA1 and PpCesA2 were 6025 bp and 6365 bp in length, respectively. The corresponding cDNA sequences encoded 1083 and 1058 amino acids, respectively, and differed considerably from each other (73% amino acid identity). Both amino acid sequences contained the key domains and motifs characteristic of functional CESA proteins isolated in other higher plants. Phylogenetic analysis revealed that PpCesA1 was most similar (99%) to its putative ortholog in Pinus taeda, PtCesA3, and PpCesA2 was highly similar to a putative ortholog in Pinus radiata, PrCesA2 (99% identity). This phylogenetic analysis supported previous findings that the divergence between the primary and secondary cell wall associated CESA proteins occurred before the divergence of angiosperms and gymnosperms approximately 300 million years ago. A fragment of a putative paralogous gene copy of PpCesA1, named PpCesA1-B was also isolated. The PpCesA1-B gene fragment was found to differ from PpCesA1 by 22 nucleotide polymorphisms and its non-allelic (paralogous) status was confirmed by segregation analysis in P. patula. In order to gain an understanding of molecular genetic variation that might affect wood formation in P. patula, we sequenced multiple allelic variants of PpCesA1, PpCesA1-B and PpCesA2, which we sampled from a species-wide reference population of P. patula. The average levels of nucleotide diversity were found to be low for all three genes (π ≈ 0.0015), which may be a property of functional members of the CesA gene family. As a result of the low nucleotide diversity, only small numbers of pair-wise informative sites were available for LD analysis and the decay in LD could only be studied in PpCesA2 where it was found to decay very rapidly (within 200 bp). Tests of neutrality suggested that the exon sequences of PpCesA1 and PpCesA2 were under significant positive (adaptive) selection. Comparison of levels of nucleotide diversity and selection in different parts of the two genes indicated that the highest levels of adaptive selection occurred in areas where amino acid substitutions could alter protein structure or function. This study provides valuable insights for designing future allele discovery efforts in P. patula with the ultimate goal of developing gene-based markers for the molecular improvement of wood formation in this tree species. / Dissertation (MSc (Genetics))--University of Pretoria, 2009. / Genetics / unrestricted

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Ambiental, Florianópolis, 2016. / Made available in DSpace on 2016-09-20T04:08:29Z (GMT). No. of bitstreams: 1 341916.pdf: 5133339 bytes, checksum: df06f36343e385ea735505346fe2c265 (MD5) Previous issue date: 2016 / A presente pesquisa investiga a aplicação das madeiras Pinus elliottii (pinus) e Drepanostachyum falcatum (bambu) como elementos filtrantes no tratamento de água para abastecimento descentralizado. Essa linha de pesquisa é inovadora, visto que existem poucas publicações sobre esse assunto a nível mundial. Esse trabalho busca dar continuidade a outros estudos sobre filtração em madeira, realizados no Laboratório de Potabilização das Águas (LAPOA), da Universidade Federal de Santa Catarina (UFSC). Os experimentos foram realizados envolvendo as seguintes etapas: 1) Caracterização das espécies por imagens obtidas por microscopia eletrônica de varredura (MEV); 2) Ensaios de adsorção do azul de metileno em serragem; 3) Ensaios de filtração frontal, aplicando as espécies pinus e bambu como elementos filtrantes. Os resultados demonstraram que as dimensões das estruturas que permitem a passagem de água na madeira pinus são menores que no bambu. O valor estimado do pH de carga superficial da serragem de pinus foi de 4,9 e do bambu de 5,9, o que indica que para adsorção de substâncias catiônicas o pH da solução deve ser maior que o pH de carga superficial do adsorvente a ser utilizado. A máxima capacidade adsortiva estimada para adsorção do azul de metileno em serragem do pinus foi de 47 mg L-1 e do bambu de 38 mg L-1 a 35 °C e pH 6,5. Ambos os adsorventes testados seguem o modelo cinético de pseudosegunda ordem e o modelo da isoterma de Langmuir. Sendo o processo de adsorção favorável segundo o fator de separação (0 < RL < 1) obtido pelos parâmetros de Langmuir. Segundo o modelo de Arrhenius, a energia de ativação (88 kJ mol-1) obtida para o adsorvente pinus representa um processo químico. Os elementos filtrantes de pinus promoveram maior remoção de turbidez (de 88 % a 98 %) quando comparado aos de bambu (máxima de 98 %), com turbidez máxima de 2,2 uT para o pinus. Isso possivelmente ocorreu devido ao menor diâmetro das estruturas anatômicas do pinus quando comparado ao bambu. Observou-se passagem de substâncias orgânicas para a água produzida pelos elementos filtrantes, por meio das análises de absorbância (? = 254 nm) (aumento de até 428 %) e COT (aumento de até 3280 %). O comprimento dos elementos filtrantes influenciou na qualidade da água produzida pelo bambu, o que não ocorreu na madeira pinus, fato que pode ser explicado pela diferença entre as estruturasanatômicas que promovem a retenção de turbidez, no pinus (margos, pontoações e traqueídeos), e no bambu (vasos metaxilema). Por fim, o pinus foi o elemento filtrante que apresentou melhor eficiência na remoção de turbidez, e também nos ensaios de adsorção do azul de metileno nesta pesquisa.<br> / Abstract : This research investigates the use of wood Pinus elliottii (pine) and Drepanostachyum falcatum (bamboo) as filter elements in decentralized water supply treatment. This line of research is innovative, since there are few publications on this subject worldwide. This work aims to continue further studies of filtration in wood, carried out in the Laboratório de Potabilização das Águas (LAPOA), in Universidade Federal de Santa Catarina (UFSC). The experiments were performed in the following steps: 1) Characterization of species by images obtained by scanning electron microscopy (SEM); 2) Methylene blue adsorption tests on sawdust; 3) Front flow filtration tests, applying the pine and the bamboo as filter elements. The results showed that the dimensions of the structures that allow the passage of water in the pine are smaller than in the bamboo. The estimated value of the zero charge pH of pine sawdust was 4.9 and of bamboo 5.9, indicating that for adsorption of cationic substances the pH of the solution must be greater than the zero charge pH of the adsorbent to be used. The maximum adsorption capacity estimated for methylene blue adsorption in pine sawdust was 47 mg L-1 and 38 mg L-1 in bamboo at 35 °C and pH 6.5. Both absorbent tested follow the kinetic model of pseudo second order and the Langmuir isotherm model. The adsorption process is favorable according to the separation factor (0 <RL <1) obtained by the Langmuir parameters. According to the Arrhenius model, the activation energy (88 kJ mol-1) obtained for the adsorbent pine represents a chemical process. The pine filter elements promote higher turbidity removal (88 % to 98 %) when compared to the bamboo?s (maximum 98 %), with a maximum turbidity of 2.2 NTU for pine. This possibly occurred due to the smaller diameter of the anatomical structures of pine compared to bamboo. It was observed the passage of organic substances to the water produced by the filter elements through analysis of absorbance (? = 254 nm) (increase of up to 428 %) and TOC (increase of up to 3280 %). The length of the filter elements influenced the quality of water produced by the bamboo, which did not occur in the pine wood. This can be explained by the difference between the anatomical structures that promote the retention of turbidity in pine (Margos, pits and tracheids) and in the bamboo (metaxylem vessels). Finally, the pine filter element showed the best efficiency in the removal of turbidity, and also in the methylene blue adsorption experiments in this study.

Submitted by Nathália Faria da Silva (nathaliafsilva.ufv@gmail.com) on 2017-07-14T12:03:50Z No. of bitstreams: 1 texto completo.PDF: 569083 bytes, checksum: 35693ca619d39da2f6814f39b945b072 (MD5) / Made available in DSpace on 2017-07-14T12:03:50Z (GMT). No. of bitstreams: 1 texto completo.PDF: 569083 bytes, checksum: 35693ca619d39da2f6814f39b945b072 (MD5) Previous issue date: 2001-10-10 / O País produziu em 1999 cerca de 3,5 milhões de toneladas das principais resinas termoplásticas, e, desse total, mais de 65% foram destinados às indústrias de embalagens plásticas. Estas embalagens, após absorvidas pelo mercado consumidor, são descartadas como resíduos pós-consumo e, por não serem biodegradáveis, tornam-se um sério problema ambiental. Este material rejeitado, após recuperado, poderia ser utilizado, em associação com a madeira, como matéria-prima para produção de chapas aglomeradas. Com o propósito de avaliar essa possibilidade, foi objetivo do presente estudo produzir chapas de partículas em camada única por meio da combinação desses materiais. Assim, empregando- se três níveis de poliestireno (PS) (0, 25 e 50%), dois níveis da mistura contendo poliestireno e polietileno tereftalato (PET/PS) (5/20 e 10/40%), três níveis de adesivo (0, 4 e 6%) à base de uréia-formaldeído e fenol-formaldeído e três níveis de solução de poliestireno em tolueno (0, 4 e 6%), combinados com três níveis (0, 50 e 75%) de partículas de madeiras de Pinus elliottii e Eucalyptus grandis, foram produzidas 164 chapas com dimensões aproximadas de 400 x 400 x 10 mm e de densidade final desejada igual a 0,60 g/cm³, geradas a partir de 82 tratamentos com duas repetições visto que para cada espécie de madeira foram produzidas seis chapas sem adesivo. As chapas produzidas tiveram as suas propriedades físicas e mecânicas determinadas em conformidade com a norma ASTM D-1037-91. Os resultados obtidos foram comparados com os mínimos exigidos pela norma ANSI/A 208.1-1993 (Wood Particleboard). Os valores experimentais, das propriedades mecânicas, com exceção daqueles das chapas produzidas sem adesivos, demonstram, quase que integralmente, que os produtos elaborados ultrapassam os valores mínimos requeridos, tornando-se, assim, aptos a serem comercializados. Quanto á absorção de água e inchamento em espessura, após 24 horas de imersão, todas as chapas à base de madeira/plástico excederam o valor máximo proposto pela norma. As chapas nas quais se aplicou a solução de poliestireno em tolueno foram, de modo geral, as que apresentaram os melhores valores para todas as propriedades. / In 1999 the Country (Brazil) produced around 3.5 million of tons of the main thermoplastic resins, and, of this total, more than 65% were used by the plastic containers industries. After being used by the consuming market, these containers are discarded as post-use residues and, since they are not biodegradable, they represent a serious environmental problem. This rejected material after being recovered, could be used, associated with wood, as raw material to produce particleboards. In order to evaluate this possibility, the objective of this study was to produce particleboards with a single layer by means of the combination of these materials. Thus, using three levels of polystyrene (PS) (0, 25 and 50%), two levels of the mixture containing polystyrene and polyethylene tereftalate (PET/PS) (5/20 and 10/40%), three levels of adhesives (0,4 and 6%) based on urea-formaldehyde and phenol- formaldehyde, and three levels of polystyrene in toluene solution (0,4 and 6%), combined with three levels (0, 50 and 75% of particles of wood of Pinus elliottii and Eucalyptus grandis, 164 boards with sizes around 400 x 400 x 10 mm and with a desired final density of 0.60 g/cm³ were produced from 82 treatments with two repetitions since for each wood species six boards were produced without adhesive. The boards had their physical and mechanical properties determined according to the standard ASTM D-1037-91. The results obtained were compared with the minimum requirements of the standard ANSI/A 208.1-1993 (Wood Particleboard). The experimental values of mechanical properties, except those of boards produced without adhesive, showed, in almost all cases, that the products surpass the required minimum values, this be coming suitable to be commercialized. However, the values of water absorption and thickness swelling, after 24 hours of immersion, of all boards based on wood/plastic exceeded the maximum value proposed by the standard. The boards treated with the solution of polystyrene in toluene were, in a general way, those that presented the best values for all properties.

Scots pine (Pinus sylvestris L.) is a long-term economically preferred woody species not only from the standpoint of its wood production but also thanks to its tolerance to extreme climatic factors, environmental modesty, and resistance to drought stress. In recent years, however, due to the action of the changing climatic conditions, this economically significant woody species withers. Its increment in the natural ecotype is affected by the adaptability to the increasing intensity of temperature extremes (prolonged heat waves). The combination of the lack of precipitation and extremely high air temperatures (even in the spring season) will significantly affect the resistance of this woody species to drought stress. This thesis is focused on the analysis of the secondary xylem and phloem cells formation of Scots pine depending on the physiological and morphological changes due to the affecting drought stress. Within the scope of the forming radial cells in individual growing seasons (2013–2016), it has been evaluated how the synergy of the specific factors affecting the overall anatomic structure of the annual ring and the vitality of the examined woody species was expressed in the formation, differentiation, and overall structure of the cells. During the four growing seasons (2013–2016), micro-cores (diameter 1.8 mm) were taken in weekly intervals in the research area in Sobesice of xylem and phloem (including the cambial zone) using the Trephor increment borer. From these micro-cores, permanent microscopic slides of the cross-section were made, on which the analysis of the cambial activity, cell formation, cell differentiation with time, and the evaluation of the morphometric parameters of the formed of xylem and phloem cells were performed. It was found that in each monitored growing season, the drought stress has shown, which was reflected by the dropped of the soil water potential (below -1 MPa) and the intensity of transpiration, which led to the stress reaction of the cambium. The reaction of the drought-stressed cambial zone has been expressed by the decreased activity (a sudden drop of the number of dividing cells) and subsequently, during the recurrence of precipitation, by the reactivation when an increase of the number of dividing cells was observed again. This factor initiated the formation of the intra-annual density fluctuations (IADF), i.e. the formation of the so-called false annual ring. The sensitive reaction of the cambium to the drought stress affected the cell production time, the number of formed cells, and also the time of differentiation of individual tracheids, which was expressed by the reduction of the radial dimensions and cell wall thickness of the tracheids. The artificially induced stress by stem girdling intensified the concurrent drought factor and in the area below the girdling, the cambial activity has stopped within two weeks after the performed treatment. The formed cells were not fully differentiated, so the zone of typically thick-walled cells of latewood was missing in the annual ring. The following growing season, the radial increment was only formed in the area above the girdling (without the latewood zone) and in the second half of the growing season, the trees gradually died. The activity of the plant hormone IAA was also affected by the drought in the summer season, when its concentration dropped below the measurability threshold (2 µg sample-1). At the time of the IAA concentration drop, latewood tracheids began to form and the phloem cell formation was completed. The synthesis and activity of the soluble low-molecular carbohydrates correlated with the course of the cambial activity and the cell differentiation phases, where the dynamics of the concentration also matched the timing of the formation of the individual cell formation phases. With phloem cells, a significant variability in the morphological dimensions has not been observed compared to xylem cells. The phenology of the needles indicated the cell wall formation phases and the initiation of the latewood tracheids. Due to the fact that the needles were fully formed in the season of the spring tracheids formation, their phenology did not reflect the drought stress which was recorded mainly in the summer season. Also, the increment of phloem was formed in the spring season. It has been presented for a long time that coniferous woody species react to the drought stress by thicker cell walls formation of the latewood tracheids. However, it has been observed within the scope of the research of this thesis that the water deficit affected the cambial activity, which has expressed itself on the intensity of the cell formation and the time of their differentiation. Due to this process, tracheids with smaller radial dimensions and a narrower cell wall were formed. This gradually causes structural changes of the formed annual ring, where the typically earlywood and latewood tracheids (classified according to radial dimensions and thicknesses of cell walls) may form independently on the growth seasonality. Especially in cases of IADF formation or in combination with the case where latewood is not even formed, a problem with the validity of the classification according to the so-called Mork’s criterion begins to occur. The understanding of the effect of the specific metabolic and physiological changes on xylem and phloem formation of Scots pine helps to clarify the issues of forestation and overall wood production of this economically significant woody species.

El trabajo realizado incluye varias aproximaciones para comprender las respuestas de los bosques de pinares de Pinus halepensis a diferentes condiciones ambientales y en concreto a las esperadas de acuerdo con las previsiones del cambio climático. En primer lugar, se propone una herramienta que permite la aplicación de una gestión forestal hidrológicamente orientada mediante el uso de datos LiDAR. En segundo lugar, se estudia en qué medida la humedad del suelo representa una variable adecuada para explicar las variaciones de crecimiento de Pinus halepensis en un gradiente de aridez. Además, se analizan las diferentes repuestas de la variable transpiración en esta especie, dependiendo de las características de sitio e intensidad de tratamiento de clara aplicado. Por último, se examina el crecimiento y el almacenamiento de agua en el tallo en un entorno de un experimento manipulativo con condiciones realistas de cambio climático en dos coníferas del semiárido.

Increased frequency of severe drought events, coupled with rising air temperatures and vapor pressure deficits (VPD), pose a great threat to Mediterranean forests. Pinus halepensis Mill. is one of the most widespread species in the countries surrounding the Mediterranean basin. Thus, water use of this species plays a critical role in the regions water balance. Studying transpiration patterns and the mechanisms behind stomatal responses to the combined effects of changing VPD and soil moisture can help us improve estimation of forest water use in a changing climate. To improve the estimation of forest evapotranspiration in the Mediterranean basin, the objective of this thesis is to evaluate the transpiration patterns of Pinus halepensis and the role of this species in the soil-water balance under different environmental conditions. Two pine forests in the Turia river basin, eastern Spain, were monitored over a two-year period. The two locations were selected at contrasting altitudes and distances to the sea but within the same hydrological basin, to evaluate if this placement would change the relationship between environmental conditions and the water use of the pines. Sap flow measurements were obtained on a 30-minute interval together with soil moisture measurements and meteorological variables. A soil-water balance was performed on a forest plot-level using an eco-hydrological model in combination with the transpiration data, to assess the contribution of pine transpiration to actual evapotranspiration. Transpiration was dictated by changes in VPD, relative extractable water (REW) and the interaction between these two variables at both sites, indicating that the pines depended on water in the shallow soil layers, and this was restricted during large parts of the year. Except for low winter temperatures having a decreasing effect on transpiration only at the inland site, no significant differences were found in the relationship between environmental drivers and transpiration patterns between the two sites. Using a predictive model, sap flow was shown to be restricted on days of mean VPD values of 2.5 kPa, even when soil moisture levels were relatively sufficient (REW = 0.30), indicating a VPD threshold that decreases pine transpiration. This could potentially affect performance and survival of the species with predicted increases in air VPD. Transpiration levels were highly restricted throughout the first year demonstrating that physiological stresses were not limited to summer months. Using two-year old seedlings in an experiment under controlled conditions confirmed that high levels of VPD can have a decreasing effect on transpiration of P. halepensis (in response to instant changes from 1.5 kPa to 2.7 kPa), while there is an intermediate VPD range that increases transpiration (between 1.0 kPa – 1.5 kPa). This demonstrate how important it is to incorporate VPD changes when predicting forest water use under future climatic changes. Combining transpiration data with eco-hydrological modelling demonstrated that transpiration levels accounted for 62% of total ETa levels during two years of study. Interception levels where 32% of gross precipitation, representing a large water loss to the forest ecosystem. With increased frequency of drought events, soil moisture levels are predicted to become even more limited. Together with a rise in temperatures and consequently VPD, transpiration and growth are likely to be constrained.

The favorable growth of young loblolly pines (Pinus taeda L.) in response to controlling non-crop vegetation is well documented. However, the beneficial effects of non-crop vegetation on soil quality, nutrient cycling, and biodiversity have not been thoroughly explored. A study was conducted to determine the effects of harvesting-induced soil disturbance, bedding and chemical vegetation control on soil processes and productivity, and to characterize the effects of silvicultural treatments on non-crop vegetation dynamics. Study plots were established on a wet pine flat on South Carolina's lower Coastal Plain. Treatments included a range of 5 disturbance classes (undisturbed, compression tracked, shallowly rutted, deeply rutted and churned), two site preparation treatments (flat planted and bedded) and a gradient of vegetation control (no vegetation control, operational-level weed control and complete weed control). Soil disturbances had relatively small effects on soil quality. Soil compaction reduced soil aeration, but this condition was fully ameliorated by bedding. Churning did not degrade the soil physical environment in any measureable way, largely because slash and litter were incorporated into the surface soil. Bedding and churning increase soil biological activity, which increased nitrogen mineralization in excess of pine demand. When non-crop vegetation was chemically controlled, mineralization rates increased due to increases in surface soil temperatures. With less vegetation on the site, the amount of nitrogen sequestered was less, furthering the potential for nitrogen loss by leaching or denitrification. Soil quality improved somewhat with increasing levels of non-crop vegetation biomass; however, these beneficial effects were marginal during two years of operational vegetation control. The majority of dominant species on undisturbed treatment areas were woody, and soil disturbance, including bedding, reduced the proportions of these species. Silvicultural treatments had little effect on the prevalence of hydrophytic species on these wetland study sites. From a forest management point of view, for this site type, it appears that much is gained by reducing competition from non-crop vegetation; the benefits of controlling the density of non-crop vegetation for encouraging early pine growth are clear. While non-crop vegetation slightly improved system function by sequestering available nitrogen, increasing diversity and increasing soil quality, these improvements do not appear to be critical to forest function on these inherently high-quality sites. / Master of Science