Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on August 6, 2009. Major professor: Dr. Lauren Garner. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Agriculture with specialization in Crop Science." "June 2009." Includes bibliographical references (p. 37-49).

There has been an increased interest in characterizing and interpreting ecological heterogeneity over space and time in the past two decades. This is mainly due to the renewed recognition of the significance of heterogeneity in ecological theories. However, studies that have combined both spatial and temporal aspects of heterogeneity have been rare. A unified approach to define and quantify heterogeneity has also been lacking. Designed to overcome these problems, this study was conducted in a 40-year-old Pinus elliottii Engelm. forest at the Savannah River Site near Aiken, SC, USA with the following specific objectives: 1) to characterize the spatial patterns of soil and forest floor variables (moisture, pH, soil available nitrogen and phosphate, forest floor and soil carbon and nitrogen), 2) to examine the dynamics of these spatial patterns in response to two types of disturbance: whole-tree harvesting and girdling, and 3) to evaluate some of the current methods for quantifying ecological heterogeneity. In response to both disturbance treatments, spatial heterogeneity measured by sample variance showed a marked "increase and then decline" temporal pattern in soil moisture, soil available nitrogen and phosphorus. Similar patterns were not found in total soil C and N, and total litter C and N. Harvesting resulted in greater and more drastic changes in the variations of soil nutrients and water than did girdling. Despite the popularity of semivariogram analysis in recent ecological studies, the technique did not provide consistent results on patterns of heterogeneity in our system. A simulation experiment demonstrated that semivariogram analysis may suffer from many problems when it is used to characterize patchiness, one form of heterogeneity. The results from this study have a number of implications. First, spatial patterns of soil resources are high dynamic. The dynamics of patterns in soil resources may partly account for the weak correlation between vegetation and soil observed in ecological literature. Second, heterogeneity may be most effectively quantified by first identifying quantifiable components and then quantifying these components individually. A common pattern can be sought by comparing patterns of different components of heterogeneity for a given ecological property and by comparing patterns of different ecological variables for a given component of heterogeneity. Third, compared to surveys, field manipulative experiments can provide information that link patterns with ecological processes. As such, this study adds to ecological literature valuable information on temporal changes of soil heterogeneity following disturbance and conceptual advances in the quantification of ecological heterogeneity. / Ph. D.

No description available.

No description available.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2007. / Härtill 5 uppsatser.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste estudo foram avaliadas a eficiência técnica e os custos da aplicação do tratamento silvicultural de desbaste de liberação seletivo, com anelamento e aplicação de herbicida (Tordon, 50% de diluição), em uma Floresta Ombrófila Densa no Estado de Roraima, manejada de acordo com os preceitos de exploração de impac o reduzido e legislação vigente. Para analisar o efeito das características das árvores na desvitalização, foi ajustado o modelo logístico binário, indicando uma menor velocidade de desvitalização para espécies secundárias. Foram aneladas 21,6 arv/ha para favorecer a liberação de 12 arv/ha, em uma relação de 1,8 competidores para cada Árvore Comercial potencial para Colheita Futura (ACCF) liberada. O resultado da aplicação do tratamento silvicultural demonstrou uma boa efetividade da técnica, alcançando 100% de mortalidade das árvores competidoras no período de 12 meses após o anelamento, com 69% das árvores desvitalizadas dentro do período de 6 meses. O custo por hectare atingiu valor total de R$ 77,88/ha, sendo o custo por árvore anelada de R$ 3,59 e o custo por árvore liberada de R$ 5,56. Ao analisar a distribuição dos custos, observou-se que 50% deveu-se ao insumo (no caso específico a aquisição do herbicida), 47% decorreu do custo da mão de obra, 2% deveu-se à aquisição de equipamento de proteção individual e 1% de materiais. O rendimento operacional alcançou 0,76 homem/dia.ha-1, abrangendo as atividades de localização das ACCF, identificação das competidoras, corte de cipós, anelamento e aplicação de herbicida. / This study presents the results of the analysis of technical efficiency and costs of silvicultural treatments carried out in a lowland Amazon rainforest logged under reduced impact logging guidelines. The silvicultural treatments consisted in the postharvest girdling and herbicide treatment (using the product Tordon in 50% solution) of remnant trees competing with future crop trees (FCTs). In order to analyze the effect of girdling on tree mortality, a binary logistic model was utilized. The model indicated a slower mortality process for secondary tree species. On average 21,6 competing trees per hectare were girdled in order to benefit 12 FCTs per hectare (on average 1,8 competitors for every FCT). Results demonstrate the high efficiency of the silvicultural treatments tested: mortality of competitors attained 69% within six months after girdling and 100% within twelve months after girdling. The total cost of girdling amounted to BRL 77,88 per ha, BRL 3,59 per girdled tree and BRL 5,56 per FCT. Of the total cost, 50% arose from production factors, especially herbicide acquisition, while 47% were labor costs. Only 2% of the total costs were generated from work safety equipment and 1% of other materials. The operative productivity attained 0,76 man days per hectare which included the activities competitor identification, climber cutting, girdling and herbicide application.

京都大学 / 新制・課程博士 / 博士(農学) / 甲第24238号 / 農博第2517号 / 新制||農||1094(附属図書館) / 学位論文||R4||N5409(農学部図書室) / 京都大学大学院農学研究科農学専攻 / (主査)教授 土井 元章, 教授 田尾 龍太郎, 准教授 中野 龍平 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Autumn senescence is a visually spectacular phenomenon in which trees prepare for the oncoming winter. The mechanism for regulation of autumn senescence in trees has been very hard to pinpoint. In this thesis the main focus is to investigate how autumn senescence is regulated in aspens (Populus tremula). Previous work has established that autumn senescence in aspens is under daylight control, in this thesis the metabolic status and the effect on autumn senescence was investigated. The metabolic status was altered by girdling which leads to accumulation of photosynthates in the canopy. This resulted in an earlier onset of senescence but also the speed of senescence was changed. At the onset of senescence the girdled trees also accumulated or retained anthocyanins. The nitrogen status of aspens during autumn senescence was also investigated, we found that high doses of fertilization could significantly delay the onset of senescence. The effects of various nitrogen forms was investigated by delivering organic and inorganic nitrogen through a precision fertilization delivery system that could inject solutes directly into the xylem of the mature aspens. The study showed that addition of nitrate delayed senescence, addition of arginine did not have any effect on the autumn senescence in aspens, and furthermore the nitrate altered the trees leaf metabolism that was more profound in high dosages of supplied nitrate.  Cytokinins are plant hormones believed to delay or block senescence, studies have suggested that the decrease of cytokinins and/or cytokinin signalling may precede senescence in some plants. To investigate how cytokinin regulates autumn senescence in aspens we profiled 34 cytokinin types in a free growing mature aspen. The study begun before autumn senescence was initiated and ended with the shedding of the leaves, and spanned three consecutive years. The study showed that the individual cytokinin profiles varied significantly between the years, this despite that senescence was initiated at the same time each year. Senescence was furthermore not connected to the depletion of either active or total cytokinins levels. The gene pattern of genes known to be associated with cytokinin was also studied, but no gene expression pattern that the profile generated could explain the onset of senescence. These results suggest that the depletion of cytokinins is unlikely to explain the tightly regulated onset of autumn leaf senescence in aspen.

Thesis (M. Sc. (Horticulture)) -- University of Limpopo, 2018 / ‘Hass’ avocado fruit changes skin colour from green to purple and then black during ripening. However, markets importing South African avocado fruit have been complaining about the ‘Hass’ skin colour not changing to purple/black during ripening. Thus, the study aimed to investigate the effect of tree girdling, harvest time and ripening temperature on ‘Hass’ avocado fruit skin colour development during ripening. The mature ‘Hass’ avocado fruit were harvested from girdled and non-girdled trees during early (April), mid- (May) and late (June) harvest times. Upon arrival, in the laboratory fruit were cold stored at 5.5°C for 28 days. After storage, fruit were ripened at 25, 21 and 16°C for 8, 6 and 4 days, respectively. After withdrawal from clod storage fruit were evaluated for skin colour development, ripening and physiological disorders (chilling injury). Fruit from girdled trees showed high maturity (low moisture content) when compared with fruit from non-girdled trees during early and mid-harvest. With respect to skin colour development, the results indicate that skin eye colour development of fruit from girdled and non-girdled trees minimally increased from emerald green (1) to olive green (3) across all harvest times, ripening temperature and ripening duration. However, late season fruit from non-girdled trees improved to purple (4) when ripened at 21°C when compared with fruit from girdled trees. In terms of objective colour, lightness, hue angle and chroma decreased for fruit from girdled and non-girdled trees, across all harvest times, ripening temperature and ripening duration. Lightness and hue angle of fruit from girdled trees were slightly reduced when compared with fruit from non-girdled trees, throughout all harvest times, ripening temperature and duration. Early and mid-season fruit harvested from girdled trees showed rapid decrease of chroma when compared with fruit from non-girdled trees, throughout ripening temperature and x duration. In terms of softening, fruit from girdled trees showed higher firmness loss and ripening percentage within 6 (16°C) and 4 (21 and 25°C) days when compared with fruit from non-girdled trees during early and mid-harvest, whereas, late harvest fruit from girdled trees reached higher ripening percentage and firmness loss within 4 days throughout ripening temperatures. With respect to cold damage, late harvested fruit from girdled trees showed higher external chilling injury when compared with non-girdled trees, throughout ripening temperature. In general, girdling treatment improved fruit maturity, ripening rate and firmness loss. However, the incidence of variable skin colouring of ‘Hass’ avocado fruit during ripening was also prevalent in early harvested fruit from girdled tree, irrespective of ripening temperature. Keywords: girdling, harvest time, physiological disorder, ripening temperature, variable colouring

Thesis (M.Sc. (Horticulture)) --University of Limpopo, 2018 / ‘Hass’ avocado fruit changes skin colour from green to purple and then black during ripening. However, markets importing South African avocado fruit have been complaining about the ‘Hass’ skin colour not changing to purple/black during ripening. Thus, the study aimed to investigate the effect of tree girdling, harvest time and ripening temperature on ‘Hass’ avocado fruit skin colour development during ripening. The mature ‘Hass’ avocado fruit were harvested from girdled and non-girdled trees during early (April), mid- (May) and late (June) harvest times. Upon arrival, in the laboratory fruit were cold stored at 5.5°C for 28 days. After storage, fruit were ripened at 25, 21 and 16°C for 8, 6 and 4 days, respectively. After withdrawal from clod storage fruit were evaluated for skin colour development, ripening and physiological disorders (chilling injury). Fruit from girdled trees showed high maturity (low moisture content) when compared with fruit from non-girdled trees during early and mid-harvest. With respect to skin colour development, the results indicate that skin eye colour development of fruit from girdled and non-girdled trees minimally increased from emerald green (1) to olive green (3) across all harvest times, ripening temperature and ripening duration. However, late season fruit from non-girdled trees improved to purple (4) when ripened at 21°C when compared with fruit from girdled trees. In terms of objective colour, lightness, hue angle and chroma decreased for fruit from girdled and non-girdled trees, across all harvest times, ripening temperature and ripening duration. Lightness and hue angle of fruit from girdled trees were slightly reduced when compared with fruit from non-girdled trees, throughout all harvest times, ripening temperature and duration. Early and mid-season fruit harvested from girdled trees showed rapid decrease of chroma when compared with fruit from non-girdled trees, throughout ripening temperature and x duration. In terms of softening, fruit from girdled trees showed higher firmness loss and ripening percentage within 6 (16°C) and 4 (21 and 25°C) days when compared with fruit from non-girdled trees during early and mid-harvest, whereas, late harvest fruit from girdled trees reached higher ripening percentage and firmness loss within 4 days throughout ripening temperatures. With respect to cold damage, late harvested fruit from girdled trees showed higher external chilling injury when compared with non-girdled trees, throughout ripening temperature. In general, girdling treatment improved fruit maturity, ripening rate and firmness loss. However, the incidence of variable skin colouring of ‘Hass’ avocado fruit during ripening was also prevalent in early harvested fruit from girdled tree, irrespective of ripening temperature. Keywords: girdling, harvest time, physiological disorder, ripening temperature, variable colouring