In order to determine if weed control as practised during the establishment phase of tree growth had a beneficial and long term (over a six to eight year rotation) impact on tree performance, a Eucalyptus hybrid clone (GC304) was planted in a field trial in 1990. The trial was situated in the coastal Zululand region near the KwaZulu-Natal town of Mtunzini. Nine different vegetation management treatments were imposed from establishment. These included a weedy control, a manually weeded treatment, a chemically weeded treatment, a 1.2 m row and 1.2 m inter-row weeding, a 0.5 m radius ring weeding, a complete weeding except for a 0.5 m radius ring around the tree, and the use of two legume cover-crops, Mucuna puriens (cowpea) and Vigna sinensis (velvet bean). Initial improvements in tree performance from these competition control treatments were detected from 60 days after planting, and were maintained over seven growing seasons. This occurred despite the absence of competitive vegetation after the first growing season due to reduced light, following crown canopy closure. There were strong indications that initial competition was mainly for moisture and possibly also for nutrients, rather than competition for light. Initially those trees that had weeds within their immediate vicinity were most affected (weedy control, inter-row weeding and the complete weeding except for a 0.5 m radius around the tree). With time, tree performance was more closely related to an increase in the percentage of the area kept free of weeds. The best performing treatment at felling, the manually weeded control, produced 17.1 % and 38.5 % more merchantable timber than the 1.2 m row weeding and the weedy control, at an increased profit of 8 % and 27 %, respectively. Two forms of competition (interspecific and intraspecific competition) were evident in the weedy control at different stages of tree development in contrast to the one (intraspecific competition) in the manually weeded treatment. Interspecific competition resulted in greater variability between the trees in the weedy control by the time canopy closure had occurred. This differentiation in tree size was further enhanced by asymmetric intraspecific competition once the trees had become established. The onset of intraspecific competition was first detected 995 days after planting for the manually weeded treatment and 1641 days after planting for the weedy control. Of the various competition indices that were tested in order to try and explain this differential growth in terms of individual tree performance, none was able to do so to complete satisfaction. The growth rates of different tree size classes were therefore compared for the weedy control and manually weeded treatment. The diverging slopes of the different stem area classes indicated that the larger trees were growing at the expense of the smaller trees. This type of competition is known as asymmetric intraspecific competition. In addition, a comparison was made between the slopes for the weedy and weedfree treatments for similar stem area classes. No significant difference was detected, indicating that similar size classes in these two treatments grew at similar rates. Trees from three treatments were selected (manually weeded treatment, 1.2 m row weeding treatment and the weedy control) and tested for the wood and pulping properties of density, active alkali consumption, extractable content, screened pulp yield, pulp yield per hectare and fibre length and coarseness. The use of Canonical Variate Analysis to determine if there were differences between the three treatments for the variates measured, indicated that they were significantly different. There was a significantly positive trend of an increase in density, extractable content and active alkali consumption with increased weed control. A possible explanation for this could be that the larger trees of the manually weeded treatment were under more stress (from increased intraspecific competition) during the latter phase of their growth. This was demonstrated by comparing the growth rates for these three treatments. The smaller trees of the 1.2 m row weeding treatment and the weedy control exhibited a lower rate of decline. As no significant difference was detected for screened pulp yield between the treatments, any differences in the pulp yield per hectare values could be attributed to differences in the merchantable volume. There was a 22.6 % and 40.8 % increase in the pulp yield per hectare for the manually weeded treatment in comparison to the 1.2 m row weeding treatment and the weedy control. The planting of cover-crops, although beneficial in terms of weed suppression, caused significant tree suppression. This occurred despite the fact that their initial biomass accumulation was slower than that of the natural weed population. Of the two cover-crops, the use of the velvet bean was not considered suitable due to its vigorous vining habit which affected the growth form of the trees. Subsequent work suggests that if the beneficial qualities of cowpeas are to be realised (that of weed suppression, erosion control and nitrogen fixation), a delay in their planting by three months after establishment of the trees should alleviate any negative impacts on tree growth. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1999.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The study was carried out to evaluate the changes in the physical and chemical properties of a sandy soil and the tree growth after afforestation of an Eucalyptus forest planted in different spacing. It was accomplished an experiment planted with Eucalyptus dunnii Maiden planted on native grassland. The spacings of cultivation were 3,50x3,50m; 3,50x1,75m; 1,75x1,75m and 1,75x0,87m. The soil studied was an Alfisol located in São Francisco de Assis city. The experimental design was a complete randomized block with four replicates. It was studied physical and chemical properties of the soil before and after 24 and 36 months of old. Soil samples were taken, for each experimental unit, in the layers soil 0,00-0,10m; 0,10-0,20m; 0,20-0,40m to determine physical properties and layers ,00-0,10m; 0,10-0,20m; 0,20-0,40m; 0,40-0,60m; 0,60-1,00m to chemical properties. The soil physical properties measured were: bulk density, total, macro and microporosity and wet aggregate size distribution. The soil chemical properties measured were: water pH, exchange Calcium, Magnesium and Potassium, available Phosphorus, and Total Nitrogen and Organic Carbon. The trees growth was evaluated to 12, 18, 24, 30, 36 and 42 months old, it was measured breast height diameter (DAP) and height of the plants, the survival percentage was determined and calculated the basal area for hectare. The results indicate to Eucalyptus cultivation changed soil structure by reduce the aggregation, the bulk density and the macroporosity. However it is not observed effect of the plant spacing on the physical properties to 24 and 36 months of Eucalyptus cultivation. In the chemical properties the Eucalyptus cultivation reduced pH, Ca and K contents of the surface layers and increase Ca content of the deep layers, increase contents Mg contents of the surface layers and reduced in the 0,60-1,00m layer; reduced contents of the N and C in the surface layers. It is not observed effect of the spacing planting in the survival percentage until 42 months old. It was higher DAP in the large plant space, while the height was higher in the narrower plant spacing, however this resulted can be changed because the forest is in full fledge. The basal area per hectare was higher in the narrower plant spacing because of there are more plants. / O estudo foi realizado com o objetivo de avaliar as alterações ocorridas nas propriedades físicas e químicas de um solo arenoso e o crescimento das árvores após a implantação de povoamentos de eucalipto em diferentes espaçamentos. O trabalho foi realizado a partir da instalação de um experimento implantado com Eucalyptus dunnii Maiden em campo nativo, nos espaçamentos 3,50X3,50m; 3,50X1,75m; 1,75X1,75m e 1,75X0,87m, em um Argissolo Vermelho Distrófico no município de São Francisco de Assis (RS). O experimento foi instalado em delineamento experimental blocos ao acaso, com quatro repetições. As avaliações das propriedades físicas e químicas do solo foram feitas antes do plantio e após 24 e 36 meses de cultivo do eucalipto, em que foram coletadas, em cada unidade experimental, amostras de solo nas camadas 0,00-0,10m; 0,10-0,20m e 0,20-0,40m para a avaliação das propriedades físicas e nas camadas 0,00-0,10m; 0,10-0,20m; 0,20-0,40m; 0,40-0,60m e 0,60-1,00m para as propriedades químicas. As propriedades físicas do solo avaliadas foram: a densidade do solo, a porosidade total, a macroporosidade, a microporosidade, a distribuição do tamanho dos agregados estáveis em água. As propriedades químicas determinadas foram: pH em água, Cálcio, Magnésio e Potássio trocáveis, Fósforo disponível, Nitrogênio e Carbono Orgânico totais. As avaliações de crescimento das árvores foram feitas aos 12, 18, 24, 30, 36 e 42 meses após o plantio, foram feitas medições do diâmetro a altura do peito (DAP) e altura das plantas, determinada a porcentagem de sobrevivência e calculada a área basal por hectare. Os resultados indicam que o cultivo de eucalipto interferiu na estrutura do solo através da redução na agregação, na densidade e na macroporosidade. No entanto não se verificou efeito do espaçamento de plantio nas propriedades físicas do solo aos 24 e 36 meses de cultivo do eucalipto. Quanto às propriedades químicas, o cultivo do eucalipto promoveu redução do pH; e dos teores de Ca e K nas camadas mais superficiais e aumentou o Ca nas camadas mais profundas; aumentou os teores de Mg na superfície do solo e reduziu na camada 0,60-1,00m; reduziu os teores de N e C nas camadas superficiais. Não se verificou efeito do espaçamento de plantio na porcentagem de sobrevivência das plantas até os 42 meses de idade. Em relação ao crescimento, observou-se maior DAP nos espaçamentos mais amplos, enquanto a altura foi maior nos espaçamentos mais densos, entretanto, essa relação pode ser alterada, pois a floresta apresenta-se em fase de pleno desenvolvimento. Em relação à área basal por hectare, os espaçamentos mais densos apresentam área basal mais elevada devido ao maior número de plantas.

Orientador: Jose Teixeira Filho / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-15T15:44:54Z (GMT). No. of bitstreams: 1 Tonello_KellyCristina_D.pdf: 3209931 bytes, checksum: ad807b85c48d80b43bb9c5e89fb27160 (MD5) Previous issue date: 2010 / Resumo: O crescimento e o desenvolvimento dos vegetais é conseqüência de vários processos fisiológicos controlados pelas condições ambientais e características genéticas de cada espécie vegetal. Este estudo teve por objetivo caracterizar o comportamento ecofisiológico da transpiração (E) e condutância estomática (Gs) de dois clones de Eucalyptus grandis x Eucalyptus urophylla (C041 e P4295) sob diferentes condições de disponibilidade hídrica no solo e em função de variáveis ambientais como radiação global (Rg), radiação fotossinteticamente ativa (Qleaf) e déficit de pressão de vapor da atmosfera (DPV). As aferições foram realizadas ao longo do período de fevereiro de 2007 a agosto de 2008 em três escalas de estudo designadas como vaso, parcela e bacia hidrográfica. Medidas de potencial hídrico antemanhã (?pd) foram realizadas para o acompanhamento das disponibilidades hídricas no solo. Após o conhecimento do comportamento ecofisiológico dos clones em função das variáveis ambientais e ?pd, buscou-se relacionar as respostas obtidas na escala vaso com as escalas parcela e bacia hidrográfica por meio de modelos ecofisiológicos desenvolvidos para a mudança de escala ao nível de folha. De acordo com os resultados, as variáveis ecofisiológicas estiveram diretamente associadas às variáveis ambientais e ao ?pd tanto para o clone C041 quanto para o clone P4295. Foram observados entre os clones comportamentos ecofisiológicos distintos quando associados à Qleaf, DPV e ?pd. Os clones apresentaram-se diferentes na amplitude de resposta de E e Gs em função de Qleaf e DPV entre as escalas, porém, observou-se a mesma tendência de comportamento, com exceção da relação Gs x DPV para o clone C041, entre escala vaso e parcela/bacia hidrográfica. Os modelos propostos para a mudança de escala de folha para folha mostraram-se satisfatórios, principalmente nas relações envolvendo a radiação fotossinteticamente ativa. Contudo, não apresentaram bons resultados para a extrapolação das respostas ecofisiológicas de Gs em função do DPV / Abstract: The growth and development of plants is a consequence of several physiological processes controlled by environmental conditions and genetic characteristics of each plant species. This study aimed to characterize the ecophysiological behavior of transpiration (E) and stomatal conductance (Gs) of two clones of Eucalyptus grandis x urophylla (C041 and P4295) under different soil water conditions and according to environmental variables such as global radiation (Rg), photosynthetic active radiation (Qleaf) and a vapor pressure deficit of the atmosphere (VPD). The measurements were performed during the period February 2007 to August 2008 on three scales of study designated as a pot, plot and watershed. Predawn leaf water potential (?pd) measurements were performed to monitor water availability in the soil. After the knowledge of the ecophysiological behavior of the clones on the basis of environmental variables and ?pd, sought to link the responses obtained in the pots scale with pot and watershed through ecophysiological models developed for scaling up leaf from leaf. According to the results, the ecophysiological behavior were directly associated with environmental variables and the ?pd both to the C041 as for P4295. Were observed among different clones ecophysiological behavior when associated with Qleaf, VPD and ?pd. The clones were different in amplitude of E and Gs as function of Qleaf and VPD between the scales, however, showed the same pattern of behavior, except for Gs x VPD for clone C041 between pot and plot / watershed scale. The proposed models for the scaling up from leaf to leaf were satisfactory, especially in relationships involving the Qleaf. However, they not provided good results for the extrapolation of ecophysiological responses of Gs as a function of VPD / Doutorado / Agua e Solo / Doutor em Engenharia Agrícola