Urban trees provide a variety of benefits to human physical and mental health. However, prior research has shown that urban tree canopy is unevenly distributed; areas with lower household incomes or higher proportions of racial or ethnic minorities tend to have less canopy. Urban tree benefits are largely spatially-dependent, so this disparity has a disproportionate impact on these communities, which are additionally subject to higher rates of health problems. Planting programs are a common way that municipal and nonprofit urban forest organizations attempt to increase canopy in cities. Increasing canopy in underserved communities is a commonly desired outcome, but which of the wide range of programmatic strategies currently employed are more likely to result in success? This research uses interviews with planting program administrators, spatially referenced planting data, and demographic data for six U.S. cities in order to connect planting program design elements to equity outcomes. I developed a planting program taxonomy to provide a framework for classifying and comparing programs based on their operational characteristics, and used it along with planting location data to identify programs that had the greatest reach into low-income and minority area. I found that highly integrated partnerships between nonprofit and municipal entities, reduced planting responsibility for property owners, and concentrated plantings that utilize public property locations to a high degree are likely to improve program penetration into low-income and minority areas. These findings provide urban forestry practitioners with guidance on how to more successfully align planting program design with equity outcomes. / Master of Science

Increased demand for barley has changed the proportion of crops grown in Virginia and the Mid-Atlantic USA. Winter wheat is the predominant small grain crop, but barley can be a direct substitute, although much less of it is grown. Soybean is grown full-season and double-cropped after both small grains. Historically, wheat was the primary small grain in the soybean double-crop rotation because of its greater profitability. The barley-soybean cropping system is not a new concept in the region, but the literature is outdated. New agronomic and economic data that directly compares full-season soybean, barley-soybean, and wheat-soybean systems using modern cultivars and management practices is needed. The objectives of this research were to: i) determine soybean yield and compare cropping system profitability of the three cropping systems; ii) perform a breakeven sensitivity analysis of the three cropping systems; and iii) determine the effect of planting date and previous winter crop on soybean yield and yield components. Soybean grown after barley yielded more than full-season soybean in two of six locations and more than soybean double-cropped after wheat in three of six locations. Net returns for the barley-soybean system were the greatest. These data indicate that soybean double-cropped after barley has the potential to yield equal to or greater than full-season soybean or double-cropped soybean following wheat, but its relative yield is very dependent on growing conditions. The profitability comparison indicated that the barley-soybean cropping system was generally more profitable than the full-season soybean and double-cropped wheat-soybean systems. This conclusion was supported by the breakeven sensitivity analysis, but remains dependent on prices that have been extremely volatile in recent years. In another study, soybean yields declined with planting date at two of four locations in 2009, a year that late-season rainfall enabled later-planted soybean to yield more than expected. In 2010, soybean yield decline was affected by the delay in planting date at both locations. Winter grain did not affect soybean yield in either year. Yield component data reinforced these results and indicated that the lower seed yield in the later planting dates was due primarily to a decrease in the number of pods. / Master of Science

Call number: LD2668 .T4 1986 A47 / Master of Science / Agronomy

Master of Science / Department of Agronomy / Rob M. Aiken / Mary Beth Kirkham / Prior studies indicate clumped planting can increase grain sorghum yield up to 45% under water deficit conditions by reducing tiller number, increasing radiation use efficiency, and preserving soil water for grain fill. The objective of this study was to evaluate effects of planting geometry on sorghum grain yield. The field study was conducted in seven environments with two sorghum hybrids, four populations, and two planting geometries. Crop responses included leaf area index, yield, and components of yield. Delayed planting decreased yield by 39%, and a later maturing hybrid increased yield, relative to an early hybrid, by 11% under water sufficiency. Clumped planting increased the fraction of fertile culms (culms which formed panicles) from 5-14%. It reduced the number of culms m-2 by 12% under water limiting conditions (at one of two locations) but increased culms m-2 16% under water sufficiency. Seeds per panicle and seed weight generally compensated for differences in panicles m-2, which were related to different planting population densities. Although agronomic characteristics of hybrids varying in maturity have been widely studied, little information exists concerning their physiological differences. Therefore, the objective of the greenhouse study was to determine if stomatal resistance, leaf temperature, and leaf chlorophyll content differed between two DeKalb grain sorghum [Sorghum bicolor (L.) Moench] hybrids. They were DKS 36-16 and DKS 44-20, of medium-early and medium maturity, respectively, when grown under field conditions in Kansas. Seeds were planted in a greenhouse. Stomatal resistance and leaf temperature were measured 55 days after planting with a Decagon Devices (Pullman, WA) diffusion porometer, and chlorophyll content was measured 119 days after planting with a Konica Minolta (Osaka, Japan) SPAD chlorophyll meter. The two hybrids did not differ in stomatal resistance, leaf temperature, chlorophyll content, height, and dry weight. Their difference in maturity was not evident under the greenhouse conditions. Future work needs to show if hybrids of different maturities vary in physiological characteristics

Chan, Fong Fiona. / Thesis submitted in: October 2001. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 165-178). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.v / Table of Contents --- p.vi / List of Tables --- p.ix / List of Figures --- p.x / List of Plates --- p.xi / List of Appendices --- p.xii / Chapter CHAPTER 1 --- INTRODUCTION / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- The problems --- p.3 / Chapter 1.3 --- Conceptual framework --- p.10 / Chapter 1.4 --- Objectives of the study --- p.13 / Chapter 1.5 --- Significance --- p.14 / Chapter 1.6 --- Organization of the thesis --- p.15 / Chapter CHAPTER 2 --- LITERATURE REVIEW / Chapter 2.1 --- Introduction --- p.17 / Chapter 2.2 --- Ecological rehabilitation --- p.19 / Chapter 2.3 --- Definition of exotic and native species --- p.20 / Chapter 2.4 --- Forest degradation --- p.21 / Chapter 2.4.1 --- Present situation of tropical forests --- p.21 / Chapter 2.4.2 --- Plantation history in Hong Kong --- p.22 / Chapter 2.5 --- Disturbances and rehabilitation strategies --- p.24 / Chapter 2.6 --- The role of plantation --- p.25 / Chapter 2.7 --- Exotic tree species versus native tree species --- p.28 / Chapter CHAPTER 3 --- THE STUDY AREA / Chapter 3.1 --- Location --- p.33 / Chapter 3.2 --- Climate --- p.35 / Chapter 3.3 --- Geology --- p.37 / Chapter 3.4 --- Soils --- p.38 / Chapter 3.5 --- Vegetation --- p.38 / Chapter 3.6 --- Planting designs and management --- p.42 / Chapter CHAPTER 4 --- SOIL CHARACTERISTICS AND PROPERTIES / Chapter 4.1 --- Introduction --- p.44 / Chapter 4.2 --- Methodology --- p.47 / Chapter 4.2.1 --- Sampling --- p.47 / Chapter 4.2.2 --- Soil texture --- p.49 / Chapter 4.2.3 --- Bulk density and porosity --- p.49 / Chapter 4.2.4 --- Penetration resistance --- p.50 / Chapter 4.2.5 --- Soil reaction and conductivity --- p.50 / Chapter 4.2.6 --- Organic carbon --- p.50 / Chapter 4.2.7 --- Total Kjeldahl nitrogen (TKN) --- p.51 / Chapter 4.2.8 --- Mineral nitrogen (ammonium and nitrate nitrogen) --- p.51 / Chapter 4.2.9 --- Total phosphorus --- p.51 / Chapter 4.2.10 --- Available phosphorus --- p.52 / Chapter 4.2.11 --- Exchangeable cations --- p.52 / Chapter 4.2.12 --- Exchangeable A1 and H --- p.52 / Chapter 4.3 --- Data processing and statistical analysis --- p.53 / Chapter 4.4 --- Results and discussion --- p.53 / Chapter 4.4.1 --- Physical properties --- p.54 / Chapter 4.4.2 --- Conductivity --- p.57 / Chapter 4.4.3 --- Soil reaction and exchangeable acidity --- p.57 / Chapter 4.4.4 --- Organic matter --- p.61 / Chapter 4.4.5 --- Total Kjeldahl nitrogen and mineral nitrogen --- p.63 / Chapter 4.4.6 --- C:N ratio --- p.65 / Chapter 4.4.7 --- Total and available phosphorus --- p.65 / Chapter 4.4.8 --- Nutrient cations --- p.67 / Chapter 4.4.9 --- Comparison with other disturbed sites --- p.69 / Chapter 4.5 --- Conclusion --- p.72 / Chapter CHAPTER 5 --- SURVIVAL AND GROWTH PERFORMANCE / Chapter 5.1 --- Introduction --- p.75 / Chapter 5.2 --- Methodology --- p.83 / Chapter 5.2.1 --- Sampling --- p.83 / Chapter 5.2.2 --- Data processing and statistical analysis --- p.85 / Chapter 5.3 --- Results and discussion --- p.85 / Chapter 5.3.1 --- Survival rate --- p.85 / Chapter 5.3.2 --- Growth performance between trial plots --- p.96 / Chapter 5.3.3 --- Growth performance among species --- p.100 / Chapter 5.3.4 --- Plantation management and species selection --- p.109 / Chapter 5.4 --- Conclusion --- p.113 / Chapter CHAPTER 6 --- FOLIAR COMPOSITION OF SPECIES / Chapter 6.1 --- Introduction --- p.116 / Chapter 6.2 --- Methodology --- p.121 / Chapter 6.2.1 --- Foliage sampling --- p.121 / Chapter 6.2.2 --- Chemical analysis --- p.123 / Chapter 6.2.2.1 --- Total Kjeldahl nitrogen (TKN) --- p.123 / Chapter 6.2.2.2 --- Total phosphorus and cation nutrients --- p.123 / Chapter 6.2.3 --- Data processing and statistical analysis --- p.124 / Chapter 6.3 --- Results and discussion --- p.124 / Chapter 6.3.1 --- Foliage composition of existing vegetation --- p.124 / Chapter 6.3.2 --- Foliage composition of planted species --- p.131 / Chapter 6.4 --- Conclusion --- p.143 / Chapter CHAPTER 7 --- CONCLUSION / Chapter 7.1 --- Summary of findings --- p.146 / Chapter 7.2 --- Implications of the study --- p.151 / Chapter 7.2.1 --- Silviculture involving native species --- p.151 / Chapter 7.2.2 --- Screening of species --- p.154 / Chapter 7.2.3 --- Native forest succession --- p.156 / Chapter 7.2.4 --- Potentials of native legumes --- p.158 / Chapter 7.3 --- Limitation of the study --- p.159 / Chapter 7.4 --- Suggestions for future study --- p.161 / REFERENCES --- p.165 / APPENDICES --- p.179

Chong Chun-wing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 151-165). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.v / Table of Contents --- p.vii / List of Tables --- p.x / List of Figures --- p.xii / List of Plates --- p.xiii / List of Appendix --- p.xiv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Waste management in Hong Kong --- p.1 / Chapter 1.2 --- Landfilling --- p.1 / Chapter 1.2.1 --- Definition --- p.1 / Chapter 1.2.2 --- Landfill design --- p.3 / Chapter 1.2.3 --- Waste degradation --- p.5 / Chapter 1.2.3.1 --- Landfill leachate --- p.5 / Chapter 1.2.3.2 --- Landfill gas --- p.6 / Chapter 1.2.3.3 --- Effective control of degraded by-products --- p.8 / Chapter 1.2.4 --- General practices after completion of landfills --- p.9 / Chapter 1.2.4.1 --- Final capping system --- p.9 / Chapter 1.2.4.2 --- Revegetation on final cover --- p.1 / Chapter 1.2.4.3 --- Post-closure management --- p.11 / Chapter 1.2.4.4 --- Afteruses --- p.12 / Chapter 1.3 --- Reclamation of closed landfills --- p.13 / Chapter 1.3.1 --- Selecting afteruse and setting ultimate ecological goal of a closed landfill --- p.14 / Chapter 1.3.1.1 --- Important considerations on landfill reclamation --- p.14 / Chapter 1.3.1.2 --- Land reclamation and ecosystem development --- p.14 / Chapter 1.3.1.3 --- Choice In Hong Kong --- p.16 / Chapter 1.3.2 --- Limitations to revegetation --- p.17 / Chapter 1.3.2.1 --- Physical problems --- p.17 / Chapter 1.3.2.2 --- Shallow soil --- p.18 / Chapter 1.3.2.3 --- Drought and waterlogging --- p.18 / Chapter 1.3.2.4 --- Nutrient deficiencies --- p.19 / Chapter 1.3.2.5 --- Landfill gas and leachate --- p.19 / Chapter 1.3.3 --- Selecting the suitable species --- p.20 / Chapter 1.4 --- Plantations and closed landfills --- p.22 / Chapter 1.4.1 --- The roles of plantations --- p.23 / Chapter 1.4.1.1 --- Enhancing soil development --- p.24 / Chapter 1.4.1.2 --- Modifying microclimate --- p.25 / Chapter 1.4.1.3 --- Facilitate natural invasion --- p.25 / Chapter 1.4.2 --- Exotics or natives? --- p.25 / Chapter 1.4.3 --- Knowledge learned from natural invasion --- p.27 / Chapter 1.4.4 --- Human management or aftercare --- p.28 / Chapter 1.5 --- Objectives of this research --- p.28 / Chapter 1.5.1 --- Knowledge gap --- p.28 / Chapter 1.5.2. --- Objectives --- p.29 / Chapter Chapter 2 --- Study Sites --- p.31 / Chapter 2.1 --- General descriptions --- p.31 / Chapter 2.2 --- Locations --- p.34 / Chapter 2.3 --- Climate --- p.36 / Chapter Chapter 3 --- Soil Status of Closed Landfills --- p.38 / Chapter 3.1 --- Introduction --- p.38 / Chapter 3.2 --- Materials and methods --- p.40 / Chapter 3.2.1 --- Landfill gas and soil moisture determination --- p.40 / Chapter 3.2.2 --- Soil sampling and analysis --- p.41 / Chapter 3.2.2.1 --- Soil sampling and preparation --- p.41 / Chapter 3.2.2.2 --- Soil texture and water retention --- p.41 / Chapter 3.2.2.3 --- Bulk density and total porosity --- p.41 / Chapter 3.2.2.4 --- Soil pH and electrical conductivity --- p.42 / Chapter 3.2.2.5 --- Organic carbon --- p.42 / Chapter 3.2.2.6 --- Nitrogen --- p.42 / Chapter 3.2.2.7 --- Phosphorus --- p.43 / Chapter 3.2.2.8 --- Cations --- p.43 / Chapter 3.2.3 --- Statistical analysis --- p.43 / Chapter 3.3 --- Results and discussion --- p.44 / Chapter 3.3.1 --- Landfill gas and soil moisture contents --- p.44 / Chapter 3.3.2 --- Soil physical properties --- p.45 / Chapter 3.3.2.1 --- Bulk density and porosity --- p.45 / Chapter 3.3.2.2 --- Texture --- p.47 / Chapter 3.3.3 --- Soil chemical properties --- p.47 / Chapter 3.3.3.1 --- pH and electrical conductivity --- p.47 / Chapter 3.3.3.2 --- Organic carbon and matter --- p.49 / Chapter 3.3.3.3 --- Nitrogen and C:N ratio --- p.50 / Chapter 3.3.3.4 --- Phosphorus --- p.51 / Chapter 3.3.3.5 --- Potassium --- p.52 / Chapter 3.3.3.6 --- Other major cations --- p.53 / Chapter 3.3.4 --- Comparison among sites --- p.53 / Chapter 3.3.5 --- Comparison with other degraded sites --- p.54 / Chapter 3.3.6 --- Implications --- p.55 / Chapter 3.4 --- Conclusion --- p.57 / Chapter Chapter 4 --- "Screening Native Species for Revegetating ""Recently Restored"" Landfills I: Drought Resistance Trial" --- p.58 / Chapter 4.1 --- Introduction --- p.58 / Chapter 4.2 --- Materials and methods --- p.60 / Chapter 4.2.1 --- Principles --- p.60 / Chapter 4.2.2 --- Species selection --- p.63 / Chapter 4.2.3 --- General experimental design --- p.65 / Chapter 4.2.4 --- Soil source and analysis --- p.68 / Chapter 4.2.5 --- Statistical analysis --- p.68 / Chapter 4.3 --- Results and discussion --- p.68 / Chapter 4.3.1 --- Soil used for filling the trial pots --- p.68 / Chapter 4.3.2 --- Chlorophyll fluorescence --- p.70 / Chapter 4.3.3 --- Standing leaf number --- p.72 / Chapter 4.3.4 --- Overall evaluation --- p.76 / Chapter 4.3.5 --- Features of the more drought resistant species --- p.78 / Chapter 4.3.6 --- Limitations for the study --- p.79 / Chapter 4.4 --- Conclusion --- p.79 / Chapter Chapter 5 --- "Screening Native Species for Revegetating ""Recently Restored"" Landfills II: Field Trial" --- p.81 / Chapter 5.1 --- Introduction --- p.81 / Chapter 5.2 --- Materials and methods --- p.82 / Chapter 5.2.1 --- Tree planting --- p.82 / Chapter 5.2.2 --- Site environmental factors --- p.83 / Chapter 5.2.3 --- Survival and growth responses --- p.85 / Chapter 5.2.4 --- Ecophysiological responses --- p.85 / Chapter 5.2.5 --- Statistical analysis --- p.85 / Chapter 5.3 --- Results and discussion --- p.86 / Chapter 5.3.1 --- Environmental factors of Plot TNP --- p.86 / Chapter 5.3.2 --- Survival rate --- p.88 / Chapter 5.3.3 --- General growth performance --- p.91 / Chapter 5.3.4 --- Seasonal growth performance --- p.95 / Chapter 5.3.5 --- Ecophysiological responses --- p.99 / Chapter 5.3.5.1 --- Fv/Fm --- p.99 / Chapter 5.3.5.2 --- Stomatal conductance --- p.100 / Chapter 5.3.5.3 --- Transpiration rate --- p.102 / Chapter 5.3.6 --- Species selection --- p.103 / Chapter 5.3.7 --- Limitations and further studies --- p.105 / Chapter 5.4 --- Conclusion --- p.106 / Chapter Chapter 6 --- "Screening Native Species for Revegetating ""Recently Restored´ح Landfills III: Different Management Practices" --- p.107 / Chapter 6.1 --- Introduction --- p.107 / Chapter 6.2 --- Materials and Methods --- p.108 / Chapter 6.2.1 --- General experimental design and seedling preparation --- p.108 / Chapter 6.2.2 --- "Survival, Growth and chlorophyll fluorescence responses" --- p.109 / Chapter 6.2.3 --- Soil source and analysis --- p.109 / Chapter 6.2.4 --- Statistical analysis --- p.110 / Chapter 6.3 --- Results and Discussion --- p.110 / Chapter 6.3.1 --- Soil physical and chemical properties --- p.110 / Chapter 6.3.2 --- Survival rate --- p.112 / Chapter 6.3.3 --- General growth peformance --- p.114 / Chapter 6.3.3.1 --- Height growth --- p.114 / Chapter 6.3.3.2 --- Basal diameter growth --- p.119 / Chapter 6.3.4 --- Chlorophyll fluorescence --- p.123 / Chapter 6.3.5 --- Implications --- p.124 / Chapter 6.4 --- Conclusion --- p.125 / Chapter Chapter 7 --- "Performance of Two Years Old Native Saplings Planted on A ""Recently Restored"" Landfill" --- p.126 / Chapter 7.1 --- Introduction --- p.126 / Chapter 7.2 --- Materials and methods --- p.127 / Chapter 7.2.1 --- "Study plots, species selection and tree sampling" --- p.127 / Chapter 7.2.2 --- Site environmental factors --- p.128 / Chapter 7.2.3 --- Survival and growth responses --- p.128 / Chapter 7.2.4 --- Ecophysiological responses --- p.128 / Chapter 7.2.5 --- Statistical analysis --- p.128 / Chapter 7.3 --- Results and discussion --- p.129 / Chapter 7.3.1 --- Environmental factors of trial plots TA & TB --- p.129 / Chapter 7.3.2 --- Survival rate --- p.131 / Chapter 7.3.3 --- General growth performance --- p.133 / Chapter 7.3.4 --- Seasonal growth performance --- p.137 / Chapter 7.3.5 --- Ecophysiological responses --- p.140 / Chapter 7.3.5.1 --- Fv/Fm --- p.140 / Chapter 7.3.5.2 --- Stomatal conductance --- p.141 / Chapter 7.3.5.3 --- Transpiration rate --- p.142 / Chapter 7.3.6 --- Evaluation of different species --- p.143 / Chapter 7.3.7 --- Effects of ages --- p.144 / Chapter 7.4 --- Conclusion --- p.145 / Chapter Chapter 8 --- General Conclusions --- p.146 / Chapter 8.1 --- Summary of findings --- p.146 / Chapter 8.2 --- Further studies --- p.148 / References --- p.151

Current and emerging threats to trees and forest ecosystems require a re-evaluation of the way forest genetic resources are managed. Governments in the United Kingdom and elsewhere are committed to the restoration, expansion and creation of new woodlands. Tree populations are often adaptively differentiated from one another, so a key question underpinning the success of planting schemes is the choice of seed origin. A long held understanding is that locally sourced seeds will have the best opportunity to tolerate conditions of the planting site (local provenancing). However, the rate at which the environment is changing introduces a great deal of uncertainty into decision making and there is concern that climate change is proceeding at rates faster than those with which locally adapted trees would be able to cope. As such, there are suggestions that seed collected from areas already experiencing the anticipated future conditions will improve the adaptability of forests (predictive provenancing). This thesis investigated outstanding questions relating to the merits of the local provenancing and predictive provenancing approaches, and the practical implementation of seed sourcing policy in British forestry. The validity of existing seed zone boundaries used under local provenancing was analysed for ancient semi-natural Scots pine Pinus sylvestris L. forests of Scotland. Vegetation description and analyses of climatic covariates revealed that the existing series of seed zones used to guide selection of planting stock for restoration do not necessarily environmentally match seed sources to planting sites under current conditions. Additional disparity is introduced when edaphic variation (or proxies for this) is considered. To determine whether future adaptation under local provenancing may be restricted by limited pollen flow among populations of native Scots pine in Scotland, the timing of pollen production in five populations was estimated by repeatedly measuring strobilus development on a series of twenty trees over three consecutive springs. Differences in the mean predicted date of pollen production were found, with populations in the warmer west shedding pollen earliest each year, although the timing and differences in timing among populations varied from year to year, with shedding taking place earliest in the warmest of the three years and latest in the coolest year. A theoretical multi-patch, ecological genetic individual-based model (IBM) was developed to investigate the utility of different seed sourcing strategies (local versus non local provenance) and their capacity to help populations adapt to directional climate change. As well as being adapted to climate, which varied in a clinal pattern, individuals also had to be well adapted to the habitat conditions of the planting site in order to survive hard selection at the seedling stage. The model showed that population size of a new planting was reduced when planting stock adapted to the future conditions but not to current conditions was deployed. The differences were most severe when selection acted simultaneously on both the climate-related and the habitat-related phenotype. Finally, a series of in-depth qualitative surveys conducted with members of the domestic forest nursery and seed supply sector in Great Britain found that there are many difficulties associated with seed sourcing and the supply of trees. These problems arise due to a very limited ability to predict demand at the time of seed sowing, and lead to waste when demand is overestimated and importation of planting stock when demand is underestimated. Confidence and competitiveness in the domestic sector could be greatly improved by updating seed sourcing guidelines and by simplifying certain aspects of the process by which forest planting projects are funded.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2005. / Thesis documentation sheet inserted. Appendix reprints five journal articles and manuscripts co-authored with others. Includes bibliographical references. Also issued electronically via World Wide Web in PDF format; online version lacks appendix.

Thesis (M.S.)--University of Delaware, 2009. / Principal faculty advisor: Robert E. Lyons, Dept. of Plant & Soil Sciences. Includes bibliographical references.

Para cada subperíodo de desenvolvimento do trigo são produzidos diferentes órgãos, estando a formação do número destes órgãos dependente da duração de cada subperíodo. A temperatura, o fotoperíodo e a vernalização contribuem significativamente para a determinação da taxa de desenvolvimento da duração desses subperíodos. Neste contexto, este estudo objetivou apresentar um mapeamento da variabilidade temporal dos fatores de ambiente em Pato Branco, e discutir suas possíveis implicações para a expressão do potencial de rendimento de grãos de trigo. Também, buscou-se analisar os períodos do ano que ofereçam as melhores condições de ambiente, em termos de temperatura e radiação solar para a definição do aumento dos componentes de rendimento e desenvolvimento da cultura, buscando as melhores épocas de semeadura para as cultivares em estudo. O experimento foi conduzido durante os anos de 2008 e 2009 na Estação Experimental do Curso de Agronomia da UTFPR, em Pato Branco-PR (26º10’ S; 52º41’W e 750 m). O delineamento utilizado foi de blocos ao acaso, com três repetições no primeiro ano e com quatro repetições no segundo ano, em esquema bifatorial (cultivares BRS 208, BRS 220 e BRS Guamirim x sete épocas de semeaduras). As semeaduras foram efetuadas no período de: 06/05, 17/05, 31/05, 14/06, 28/06, 12/07 e 26/07 para o ano de 2008 e 02/05, 16/05, 02/06, 13/06, 30/06, 13/07, 24/07 para o ano de 2009. Assim, o presente estudo, inicialmente, determinou os diferentes subperíodos de desenvolvimento dos genótipos de trigo testados, assim delimitados: SE-EM, EM-DA, DA-ET, ET-AN, AN-MF. Os estádios de duplo anel e de espigueta terminal foram determinados morfologicamente, em 3 colmos colhidos a cada 48 horas. Para determinação da maturação fisiológica, cinco espiguetas centrais de três espigas, totalizando 15 espiguetas por parcela foram amostradas a cada 72 horas e levadas a estufa, para após serem pesadas, considerando a maturação fisiológica quando apresentavam massa constante. Também, foram avaliadas as implicações do QF no rendimento dos genótipos testados. Foram analisadas as variáveis: altura de planta, massa seca da parte aérea e espigas, índice de colheita e os componentes de rendimento (espigas m-2, espiguetas espiga-1, grãos espiguetas-1 e massa de mil grãos). Conclui-se que não foi possível observar efeito claro, do quociente fototermal (QF) sobre a definição dos componentes de rendimento. Para o ano de 2008 o subperíodo AN-MF, esteve associado com o aumento do rendimento de grãos, somente para a cultivar BRS 220, correlacionando-se posteriormente com o aumento do QF e repercutindo no aumento da massa de grãos. Para o ano de 2009 não foi possível observar correlações do rendimento de grãos com a soma térmica. Entretanto foi verificado entre o QF e a soma térmica do subperíodo AN-MF, para a cultivar BRS Guamirim. Quanto ao rendimento de grãos, esse diferiu entre os anos de alta precipitação (2009) com relação ao ano de baixa precipitação (2008). As semeaduras realizadas nas datas de 30 de maio e 14 de junho ocasionaram os maiores rendimentos de grãos, para os anos de 2008 e 2009, respectivamente. / For each subperiod development of wheat are produced in different organs and is the formation of the number of these organs dependent on the duration of each subperiod. The temperature of the vernalization photoperiod and contribute significantly to determine the rate of development of the length of such sub-periods. In this context, this study aims to map the temporal variability of environmental factors in Pato Branco, and discuss its possible implications for the expression of yield potential of wheat. Also, we attempted to analyze the periods of the year that offer the best environmental conditions, in terms of temperature and solar radiation to define the increase in yield components and development of culture, seeking the best seasons to the cultivars studied. The experiment was conducted during the years 2008 and 2009 at the Experimental Station of Agronomy Course UTFPR in Pato Branco-PR (26º10'S; 52º41'W and 750 m). The experimental design was randomized blocks with three replications in the first year and four replications in the second year in a factorial scheme (BRS 208, BRS 220 and BRS Guamirim x seven sowing dates). The sowings were made in the period of: 06/05 17/05 31/05 14/06 28/06 12/07 and 26/07 for the year 2008 and 02/05 16/05, 02 / 06 13/06 30/06 13/07 24/07 for the year 2009. Thus, this study initially determined the different developmental sub periods of the wheat genotypes tested, so defined: SE-EM, EM-DA, DA-ET, ET-AN, AN-MF. The double ring stages and terminal spikelet were determined morphologically, 3 stalks harvested every 48 hours. To determine the physiological maturity, five central spikelets of three spikes, with 15 spikelets per plot were sampled every 72 hours and brought the oven, for after being weighed, considering the physiological maturity when they had constant weight. Also, we assessed the implications of QF yield of genotypes. The variables analyzed were: plant height, shoot dry weight and ear, harvest index and yield components (spikes m-2, spikelets spike-1, grains spikelet-1 and thousand grain weight). It is not clear effect was observed, photothermal quotient (QF) on the definition of component performance. For the year 2008 the subperiod AN-MF, was associated with increased grain yield, only for BRS 220, correlating with the later increase in QF and reflecting the increase in grain mass. For the year 2009 was not possible to observe correlations of yield with the thermal. However it was observed between the QF and the thermal sub-period of the AN-MF, for BRS Guamirim. The grain yield, this differed between the years of high rainfall (2009) with respect to years of low precipitation (2008). Cultivation procedures conducted on the dates of May 30 and June 14 showed higher grain yields for the years 2008 and 2009, respectively.