Broccoli is a vegetable crop of increasing importance in Australia, particularly in south-east Queensland and farmers need to maintain a regular supply of good quality broccoli to meet the expanding market. However, harvest maturity date, head yield and quality are all affected by climatic variations during the production cycle, particularly low temperature episodes. There are also interactions between genotype and climatic variability. A predictive model of ontogeny, incorporating climatic data including frost risk, would enable farmers to predict harvest maturity date and select appropriate cultivar – sowing date combinations. The first stage of this research was to define floral initiation, which is fundamental to predicting ontogeny. Scanning electron micrographs of the apical meristem were made for the transition from the vegetative to advanced reproductive stage. During the early vegetative stage (stage 1), the apical meristem was a small, pointed shoot tip surrounded by leaf primordia. The transitional stage (stage 2) was marked by a widening and flattening to form a dome-shaped apical meristem. In the floral initiation stage (stage 3), the first-order floral primordia were observed in the axils of the developing bracts. Under field conditions, the shoot apex has an average diameter of 500 &plusmn; 3 µm at floral initiation and floral primordia can be observed under a light microscope. Sub-zero temperatures can result in freezing injury and thereby reduce head yield and quality. In order to predict the effects of frosts, it is desirable to know the stages of development at which plants are most susceptible. Therefore, the effects of sub-zero temperatures on leaf and shoot mortality, head yield and quality were determined after exposure of plants to a range of temperatures for short periods, at different stages of development (vegetative, floral initiation and buttoning). Plants in pots and in the field were subjected to sub-zero temperature regimes from –1 °C to –19 °C. Extracellular ice formation was achieved by reducing temperatures slowly, at a rate of -2 °C per hour. The floral initiation stage was most sensitive to freezing injury, as yields were significantly reduced at –1 °C and –3 °C, and shoot apices were killed at –5 °C. There was no significant yield reduction when the inflorescence buttoning iv stage was subjected to –1 °C and –3 °C. Although shoot apices at buttoning survived the –5 °C treatment, very poor quality heads of uneven bud size were produced as a result of arrested development. The lethal temperature for pot-grown broccoli was between –3 °C and –5 °C, whereas the lethal temperature for field-grown broccoli was between –7 °C and –9 °C. The difference was presumably due to variation in cold acclimation. Freezing injury can reduce broccoli head yield and quality, and retard plant growth. Crop development models based only on simple thermal time without restrictions will not predict yield or maturity if broccoli crops are frostdamaged. Field studies were conducted to develop procedures for predicting ontogeny, yield and quality. Three cultivars, (‘Fiesta’, ‘Greenbelt’ and ‘Marathon’) were sown on eight dates from 11 March to 22 May 1997, and grown under natural and extended (16 h) photoperiods in a sub-tropical environment at Gatton College, south-east Queensland, under non-limiting conditions of water and nutrient supply. Daily climatic data, and dates of emergence, floral initiation, harvest maturity, together with yield and quality were obtained. Yield and quality responses to temperature and photoperiod were quantified. As growing season mean minimum temperatures decreased, fresh weight of tops decreased while fresh weight harvest index increased linearly. There was no definite relationship between fresh weight of tops or fresh weight harvest index and growing season minimum temperatures > 10 °C. Genotype, rather than the environment, mainly determined head quality attributes. ‘Fiesta’ had the best head quality, with higher head shape and branching angle ratings than ‘Greenbelt’ or ‘Marathon’. Bud colour and cluster separation of ‘Marathon’ were only acceptable for export when growing season mean minimum temperatures were < 8 °C. Photoperiod did not influence yield or quality in any of the three cultivars. A better understanding of genotype and environmental interactions will help farmers optimise yield and quality, by matching cultivars with time of sowing. Crop developmental responses to temperature and photoperiod were quantified from emergence to harvest maturity (Model 1), from emergence to floral initiation (Model 2), from floral initiation to harvest maturity (Model 3), and in a combination of Models 2 and 3 (Model 4). These thermal time models were based on optimised base v and optimum temperatures of 0 and 20 °C, respectively. These optimised temperatures were determined using an iterative optimisation routine (simplex). Cardinal temperatures were consistent across cultivars but thermal time of phenological intervals were cultivar specific. Sensitivity to photoperiod and solar radiation was low in the three cultivars used. Thermal time models tested on independent data for five cultivars (‘Fiesta’, ‘Greenbelt’, ‘Marathon’, ‘CMS Liberty’ and ‘Triathlon’) grown as commercial crops on the Darling Downs over two years, adequately predicted floral initiation and harvest maturity. Model 4 provided the best prediction for the chronological duration from emergence to harvest maturity. Model 1 was useful when floral initiation data were not available, and it predicted harvest maturity almost as well as Model 4 since the same base and optimum temperatures of 0 °C and 20 °C, respectively, were used for both phenological intervals. Model 1 was also generated using data from 1979-80 sowings of three cultivars (‘Premium Crop’, ‘Selection 160’ and ‘Selection 165A’). When Model 1 was tested with independent data from 1983-84, it predicted harvest maturity well. Where floral initiation data were available, predictions of harvest maturity were most precise using Model 3, since the variation, which occurred from emergence to floral initiation, was removed. Prediction of floral initiation using Model 2 can be useful for timing cultural practices, and for avoiding frost and high temperature periods. This research has produced models to assist broccoli farmers in crop scheduling and cultivar selection in south-east Queensland. Using the models as a guide, farmers can optimise yield and quality, by matching cultivars with sowing date. By accurately predicting floral initiation, the risk of frost damage during floral initiation can be reduced by adjusting sowing dates or crop management options. The simple and robust thermal time models will improve production and marketing arrangements, which have to be made in advance. The thermal time models in this study, incorporating frost risk using conditional statements, provide a foundation for a decision support system to manage the sequence of sowings on commercial broccoli farms.

Arid and semi-arid rangelands are important ecosystems that are consistently degraded through disturbances such as wildfires. After such disturbances, the invasion and dominance of annual grasses, like cheatgrass (Bromus tectorum L.), can lead to an overall loss of ecosystem productivity and an increase in fire frequency. To reduce weed dominance, native and introduced perennials species are typically be seeded in the fall. High mortality is seen from these seeded plant communities due to germinated seed being exposed to freezing, drought, fungal pathogens, and other biotic and abiotic stressors during winter months. We utilized wet-thermal accumulation models to first further validate the theory that germination from seeded plant populations occurs during periods of high environmental stress, and then to establish the practicality of abscisic acid seed coatings as a technology that could circumvent winter germination and mortality. In Chapter 1, we developed an excel workbook called Auto-Germ using Visual Basic for Applications, which allows users to estimate field germination timing based on wet-thermal accumulation models and field data. We then used Auto-Germ to model seed germination timing for 10 different species, across 6 years, and 10 Artemisia-steppe sites in the Great Basin of North America. We estimated that for the majority of the species analyzed, a mid to late-winter planting was required on average for the majority of the population to germinate in the spring. This planting time would be logistically difficult for many land managers, due to freezing and/or saturated soil conditions. In Chapter 2, we utilized wet-thermal accumulation models to evaluate the use of abscisic acid (ABA) to delay germination of Pseudoroegneria spicata (Pursh) Á. Löve (perennial native bunchgrass) across 4 years and 6 Artemisia-steppe sites. Germination models estimated that ABA seed treatments typically would delay germination of fall sown seed to late winter or early spring when conditions may be more favorable for plant establishment. Based on these results, we recommend both the use of wetthermal accumulation models as a tool in educating researchers and land managers in knowing when seeding practices should occur, and the further study of ABA seed coatings as a technology that may improve plant establishment of fall sown seeds.

The cultivation of medicinal plants, like marigold, is increasing in Brazil and is an alternative for cultivation in small areas. For this reason it is important to know about its bioclimatic requirements and its phenometric characteristics in order to obtain maximum quality and yield. Thus, the main goals of this work were: evaluate the effect of temperature on Calendula officinalis L. seed germination, testing 15°C, 20°C, 25°C 30°C and 35°C, in the presence and absence of light; determine the phyllochron in three sowing dates (04/06/2005, 06/23/2005 and 10/03/2005); evaluate the effect of the different sowing dates and hydric supply (100%, 85%, 70% and 55% of field capacity) on flower flavonoids and; determine the fresh and dry matter production of the different organs in different sowing dates and when submitted to a 21-day hydric deficient period from flowering on. It was observed that the highest seed germination percentage occurs at the temperature of 20°C, and that temperatures higher than 30°C are harmful to seedlings; sowing dates interfere on the phyllochron and on the number of leaves on both the main and on the first lateral stem; the relation between the thermic sum and plant biomass production is highly significant, the growth of plants being higher in the April and June sowing dates as compared to those of October; water supply in the substratum and the accumulated thermic sum interfere on the growth parameters, the plants submitted to lower water availability in the substratum (55% and 70%), even after rehydration, do not recover fresh and dry matter production along the growing cycle; the best sowing dates for seed production are those of April and June, and for the production of fresh and dry matter of flowers the April date; there is no significant effect of hydric deficiency on flower and seed production parameters; high temperatures cause deleterious effects on growth of plants; Quercetin and Rutin contents on flowers vary along the plant development and with sowing dates, being higher in warmer dates; there is effect of hydric deficiency on plants and; submitted to a hydric supply in the substratum of 55% and 70% of the field capacity at flowering initiation and for a three-week period were favored in the concentration production of Rutin and Quercetin in the flowers. / O cultivo de plantas medicinais, como a calêndula, é crescente no Brasil e uma alternativa para produção em pequenas áreas. Para isso é importante conhecer suas exigências bioclimáticas e suas características fenométricas para se obter o máximo de rendimento e com qualidade. Assim, os objetivos, neste trabalho, foram: avaliar o efeito da temperatura na germinação das sementes de Calendula officinalis L., testando 15°C; 20°C; 25°C; 30°C e 35°C, na presença e na ausência de luz; determinar o filocrono em três épocas de semeadura (06/04/2005; 23/06/2005 e 03/10/2005); avaliar o efeito das diferentes épocas de semeadura e de suprimento hídrico (100%, 85%, 70% e 55% da capacidade de campo) nos flavonóides das flores e; determinar a produção de massa seca e fresca dos diferentes órgãos em diferentes épocas de semeadura e quando submetida a um período de 21 dias de deficiência hídrica a partir do florescimento. Foi constatado que a maior percentagem de germinação das sementes ocorre à temperatura de 20°C, e temperaturas superiores a 30°C são prejudiciais às plântulas; as épocas de semeadura interferem no filocrono e no número de folhas da haste principal e da primeira haste lateral; a relação entre a soma térmica e a produção de biomassa de plantas é altamente significativa, sendo o crescimento das plantas maior nas épocas de abril e junho do que naquelas da época de outubro; o suprimento de água no substrato e a soma térmica acumulada interferem nos parâmetros de crescimento, sendo que as menores disponibilidades de água no substrato, de 55% e 70%, mesmo após a reidratação não recuperam a produção de massa fresca e seca ao longo do ciclo; as melhores épocas de semeadura para a produção de sementes são as dos meses de abril e junho e para a produção de massa fresca e seca de flores, a do mês de abril; não ocorre efeito significativo da deficiência hídrica nos parâmetros de produção de flores e de sementes; temperaturas elevadas causam um efeito deletério no crescimento das plantas; os teores de Quercetina e Rutina nas flores variam ao longo do desenvolvimento das plantas e nas épocas de cultivo, sendo mais elevados nas épocas mais quentes; há efeito da deficiência hídrica na planta e; as plantas submetidas a um suprimento hídrico no substrato, de 55% e 70% da capacidade de campo, no início do florescimento e por um período de três semanas, foram favorecidas na produção de concentração de Rutina e de Quercetina nas flores.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The knowledge of plants response to grazing, with emphasis on growing and senescence processes is necessary to improve the natural grasslands usage and efficiency. Based on this, this work aimed to study morphogenic characteristics of predominant natural grasses in the central region Rio Grande do Sul State (RS), under rotational grazing based on thermal time intervals. The study was carried out at Universidade Federal de Santa Maria area, in Santa Maria/RS city, from September 2010 to March 2011, in a completely randomized experimental design, with two treatments: 375 degree day and 750 degree day grazing intervals and three repetitions. Morphogenic characteristics were measured on Andropogon lateralis Nees, Aristida laevis Nees, Axonopus affinis Chase, Paspalum notatum Fluegge and Paspalum plicatulum Michx. grass species, chosen based on functional typology. There was no significant difference between the treatments, but it was verified among species and seasons. The largest leaf appearance rates, and the the smallest leaf appearance intervals, were observed on P. notatum and A. affinis species. A. laevis e P. plicatulum showed the largest leaf lifespan and leaf elongation rate. Spring is characterized as the growing season, with highest leaf appearance and elongation values, and summer is marked by the flowering initiation, represented by internodes elongation and reduction of morphogenic characteristics. P. notatum is the grazing species with the greatest adaptative potential. / O conhecimento das respostas das plantas à desfolha, com ênfase para os processos de crescimento e senescência, é necessário a fim de melhorar o uso e eficiência das pastagens naturais. Com base nisso, o trabalho teve por objetivo estudar as características morfogênicas de gramíneas nativas predominantes na região central do Rio Grande do Sul (RS), submetidas a pastoreio rotativo com intervalos determinados por somas térmicas. O trabalho foi desenvolvido no município de Santa Maria/RS, em área da Universidade Federal de Santa Maria, de setembro de 2010 a março de 2011, em um delineamento experimental inteiramente casualizado, com dois tratamentos, intervalos de pastoreios de 375 graus-dia e de 750 grausdia, e três repetições. Foram realizadas medições de características morfogênicas nas espécies vegetais Andropogon lateralis Nees, Aristida laevis Nees, Axonopus affinis Chase, Paspalum notatum Fluegge e Paspalum plicatulum Michx. selecionadas a partir de uma tipologia funcional. Não houve diferença significativa entre os tratamentos, mas houve entre espécies e entre estações. As maiores taxas de aparecimento foliar e os menores intervalos de aparecimento de folhas são observados nas espécies P. notatum e A. affinis. A. laevis e P. plicatulum apresentam as maiores durações e taxas de elongação foliares. Primavera se caracteriza como a estação de crescimento, com valores superiores de aparecimento e elongação foliar, e verão é marcado pelo início do florescimento, representado pelo alongamento dos entrenós e redução nas características citadas acima. P. notatum é a espécie com maior potencial adaptativo ao pastejo.

Cassava (Manihot esculenta Crantz) is a native plant of Brazil and the base of multiple products, iincluding ethanol. Rio Grande do Sul State is a minor producer of cassava in Brazil, especially in the Central Region of the State. The objective of Chapter I in this Dissertation was to determine the phyllochron, the final leaf number (FLN) on the main stem (MS) and on simpodial branches of a cassava variety in different planting dates ia subtropical climate. The objective of Chapter II in this Dissertation was to characterize some development and growth parameters, and yield components of stem and tuber roots of a cassava variety in several planting dates in the Central Region of Rio Grande do Sul State. A field experiment was conducted in Santa Maria, RS, Brazil, with cassava variety FEPAGRO RS 13, in a 16,000 plants ha-1 plant density. Treatments were four planting dates (26 Sep. 2006, 18 Oct. 2006, 08 Nov. 2006, and 28 Nov. 2006) in a completely randomized design, with sampling in the plots. Weekly measures of leaf number in six plants per plot were done for determining the phyllochron and the final leaf number on the MS, first order (RS1) and second order (RS2) branches. The phyllochron (oC day leaf-1) on the MS, RS1 and RS2, and the thermal time for developmental phases were estimated using a base temperature of 14oC. Leaf area was calculated from weekly measured of length the largest lobule of individual leaves and the leaf área index (LAI) was calculated by the sum of the area of individual leaves divided by the area o fone plant (0.64 m2). Other growth variables were measured during the winter when plants were not growing and right before harvesting. At harvesting, fresh and dry yield of stems and tuber rootswere measured in six plants per plot. The phyllochron and FLN varied with planting date, and are not different among stems in the same branching (RS1 and RS2). The phyllochron increased in the sequence MS<RS1<RS3 while the FLN had an inverse trend, i.e., MS>RS1>RS3. Early plantings hastened the onset of starch storage in the roots and date of RS1 appearance in this cassava variety. Maximum LAI was the greatest in the earliest planting date (LAI=7.7), decreased in the following planting dates, and increased again for the latest planting date (LAI=7.4). Growth of cassava variety FEPAGRO RS 13 decreased as planting date was delayed, and stems withing the same branching (RS1 and RS2) have different growth. There was interaction between planting dates and stems for the variables final stem length and final stem diameter. Among brances, final stem diameter was greater in the first planting date. Final plant heigth was greater in the two earliest planting dates. Stem yield was greater in the earliest planting date, while tuber roots yield was not different among planting dates. / A mandioca (Manihot esculenta Crantz) é uma planta nativa do Brasil e base de múltiplos produtos, incluindo o álcool. O Rio Grande do Sul detém uma pequena participação nacional na produção de mandioca, concentrada principalmente na região da Depressão Central. O objetivo do capítulo I dessa dissertação foi determinar o filocrono, o número final de folhas (NFF) na haste principal (HP) e nas ramificações simpodiais de uma variedade de mandioca em diferentes datas de plantio em condições de clima subtropical. O objetivo do capítulo II foi caracterizar alguns parâmetros de desenvolvimento, de crescimento e os componentes da produtividade de ramas e de raízes tuberosas de uma variedade de mandioca em várias datas de plantio na região da Depressão Central do Estado do Rio Grande do Sul. Um experimento de campo foi conduzido em Santa Maria, RS, com a variedade FEPAGRO RS 13, na densidade de 16.000 plantas ha-1. Os tratamentos foram quatro datas de plantio (26/09/2006, 18/10/2006, 08/11/2006 e 28/11/2006) no delineamento experimental inteiramente casualizado com amostragem na parcela. Para a determinação do filocrono e número final de folhas da HP, ramificações de primeira (RS1) e segunda (RS2) ordem, foram realizadas contagens semanais em seis plantas por parcelão. Foi estimado o filocrono (ºC dia folha-1) para HP, RS1 e RS2 e a soma térmica para as fases de desenvolvimento, considerando a temperatura base para esta variedade de mandioca de 14ºC. A área foliar foi calculada apartir de medidas quinzenais do comprimento do maior lóbulo das folhas de uma planta em cada parcelão e o índice de área foliar (IAF) verde foi calculado somando-se as áreas individuais das folhas e dividindo-se pela área de solo ocupada por uma planta (0,64 m2). As outras variáveis de crescimento foram medidas durante o repouso invernal antes da colheita. No momento da colheita foram coletadas as variáveis de produtividade da parte aérea (ramas) e das raízes tuberosas nas seis plantas marcadas de cada parcelão e após determinadas a matéria fresca e seca dessas variáveis. O filocrono e NFF variaram com as datas de plantio. Dentro das ramificações simpodiais RS1, RS2, o filocrono e o NFF não são diferentes entre as hastes. O filocrono aumentou na seqüência HP<RS1<RS2 e o NFF teve variação inversa HP>RS1>RS2. Plantios mais cedo aceleram o desenvolvimento até o início da acumulação de amido (IAA) e até a ramificação simpodial de primeira ordem (RS1) dessa variedade de mandioca. O IAF máximo foi maior para o plantio em 26/09/2006 (IAF=7,7) e decresceu nas duas próximas datas, sendo elevado para a última data de plantio 28/11/2006 (IAF= 7,4). O crescimento da mandioca variedade FEPAGRO RS 13 decresceu com o atraso na data de plantio, e dentro de cada ramificação RS1 e RS2 as hastes têm crescimento diferentes. Houve interação entre datas de plantio e hastes para a variável comprimento e não para a variável diâmetro final das hastes. Entre as ramificações, o diâmetro final dos ramos foi maior para a primeira data de plantio. A altura final de plantas foi maior para as duas primeiras datas de plantio. A produtividade de ramas foi maior na primeira data de plantio enquanto a produtividade de raízes tuberosas não diferiu entre as datas de plantio.

Leafy vegetables, lettuce (Lactuca sativa L. cv. Green Oakleaf), pak choi (Brassica sinensis L. cv. Oriental Taisai) and rocket (Eruca sativa L.), were planted in an open field at Lincoln University on January 2005. Plants were harvested at 5 cm cutting height above the growing point with three different harvest start times, early start (ES), mid start (MS) and late start (LS) of harvest respectively. There were three harvests during the growing season with a 4-week interval between harvests. Generally, lettuce produced significantly higher total FW/plant (208 g) than pak choi or rocket (123 and 102 g total FW/plant, respectively). Lettuce also produced significantly higher total FW/plant than pak choi or rocket in each treatment. Lettuce produced significantly more total saleable leaf FW/plant in the ES, MS and LS treatment (137.5, 120.9 and 169.3 g FW/plant), compared with pak choi (52.9, 100 and 92 g FW/plant) or rocket (31.5, 92.2 and 56.4 g FW/plant). Pak choi produced higher total saleable leaf FW/plant than rocket in the ES and LS treatments, but a similar total saleable leaf FW/plant in the MS treatment. The best time to start harvesting was the LS treatment for lettuce, while pak choi and rocket produced better yields in the MS and LS treatments. Results for total DW/plant showed that different harvest start times did not affect the total DW/plant in lettuce. However, pak choi and rocket produced less total DW/plant in the ES treatment compared to the MS or LS treatments. This was due to a faster recovery by lettuce. In addition, lettuce produced significantly higher DW/plant during regrowth at the second and third harvests than pak choi or rocket, even though it was significantly lower at the first harvest. It is likely that after harvesting greater carbohydrate reserves and greater remaining leaf area produced greater regrowth potential in lettuce. These results suggest that lettuce has the most regrowth potential, while rocket has more than pak choi in this reaping and regrowth system. When plants were harvested at the same cutting level, lettuce had the most remaining leaf area of the three species. This remaining leaf area for lettuce could be another reason for faster recovery and more regrowth potential. More reserves and remaining leaf area may also be the reason for more regrowth potential in rocket compared to pak choi. Another important reason for the better performance of lettuce was that temperatures during the growing season were in the range of optimum temperatures (12-21 ºС), except for the regrowth between the second and third harvests in the LS. This relates to higher photosynthetic rates and in turn leads to faster recovery and regrwoth. Lettuce was the most suitable crop in the reaping and regrowth system in this experiment. However, rocket might also be appropriate for this system, particularly if the price is high enough to make it economically viable.

In the 400-600 mm annual rainfall zone of the Sahel, soil fertility is the main determinant of yield in rainfed millet cropping systems in all but the driest years. Numerous on-farm and on-station experiments have addressed the issue of improving soil fertility. Yet the widespread use of the experimental results is restricted by the highly site specific millet response to fertility management practices due to high spatially variable soil properties as well as high intra- and inter-annual rainfall variability. Mathematical soil-crop growth simulation models could therefore suitably complement experimental research to support decision making regarding soil fertility under variable rainwater supply conditions. The objective of this thesis was therefore to develop the biophysical basis for the use of crop-soil models in decision support regarding water and soil fertility management and risk mitigation strategies in rainfed millet-based systems of Sahelian Niger. Because farmers rely on multiple cultivars with variable length of growing cycle due to sensitivity to temperature and photoperiod as part of their risk management strategies we first characterized seven Sahelian millet genotypes and parameterized the Agricultural Production Systems Simulator (APSIM-millet model). The cultivars include three improved cultivars (CIVT, ICMV-IS-89305, ZATIB) and four landraces (Ankoutes, Hainikirey, Maewa and Zongo). Our research showed that only one of the cultivars, Maewa, was very photosensitive contrary to the six others. The majority of the agronomic state variables (leaf number, leaf area, biomass and grain yield) were negatively affected by late sowing (associated with lower air temperatures). This characterization enabled to compute for the first time in the Sahel the principal eco-physiological or genetic millet parameters (thermal times of development phases, leaf area dynamics) of crop growth models (e.g. APSIM, DSSAT). To gain confidence in the use of the APSIM model for decision support in the Sahelian environment, it was successfully tested to reproduce the agronomic state variables under non-limiting water and nutrient supply conditions. Moreover the APSIM model satisfactorily reproduced the millet CIVT cultivar response to water x N interaction from the combined application of crop residue, cattle manure and mineral fertilizer during two years and for contrasted rainfall conditions. Using the model with site and cultivar specific parameterization, we implemented two applications for decision support. A 23-year, long term factorial numerical experiment showed that a moderate N application of 15 kg N/ha is more appropriate for smallholder, subsistence farmers than the usual 30 kg N/ha recommendation. Although it implies a lower long term average yield than at 30 kg N/ha, the application of 15 kg N/ha guarantees both a higher minimum yield in extreme dry years and a lower inter-annual variability, thereby increasing food security and reducing farmers vulnerability. In the second model application, we integrated GIS information (land tenure, spatially distributed weather data, fertility management) and the APSIM model in a 12-year yield simulation to show that the spatial dispersion of fields of a household throughout the village territory (farmer risk management strategy) leads to more uniform yields across households and reduces the inter-annual yield variability in the Fakara region of Niger. Our research breaks the ground for several other applications of the use of crop-soil simulation models in millet-based systems in the Sahel, e.g. climate change impact and food crisis mitigation. / Dans la zone Sahélienne avec 400 à 600 mm de précipitation annuelle, la fertilité des sols est le principal facteur déterminant des rendements du mil pluvial hormis lors des années plus sèches. De nombreuses expérimentations au champ et en station ont abordé la question de l’amélioration de la fertilité des sols. Cependant, l’extrapolation de ces résultats, et a forciori leur utilisation par les agriculteurs, est limitée par le fait que la réponse du mil à ces pratiques de fertilité dépend fortement des propriétés des sols très variables dans l’espace ainsi que de la pluviométrie annuelle et sa répartition intra-annuelle. Les modèles mathématiques et dynamiques de simulation de la croissance des plantes peuvent donc utilement compléter la recherche expérimentale pour l’aide à la décision en ce qui concerne la gestion de la fertilité des sols dans diverses conditions d’alimentation hydrique. L’objectif de cette thèse était donc de développer les bases biophysiques pour l’utilisation de modèles de croissance des cultures en vue de leur utilisation comme outils d’aide à la décision en matière de gestion de l’eau et la fertilité des sols dans les systèmes de culture à base de mil en zone sahélienne du Niger. Puisque les paysans utilisent de multiples variétés de mil avec des cycles de croissance variables en tant qu’élément dans leurs stratégies de gestion des risques, nous avons d’abord caractérisé sept génotypes de mil Sahelien en vue de la paramétrisation du model dynamique APSIM (Agricultural Production Systems Simulator). Trois variétés améliorées (CIVT, ICMV-IS-89305, ZATIB) et quatre variétés locales paysannes (Ankoutes, Hainikirey, Maewa et Zongo) ont été étudiées. Notre recherche a montré que seule une des variétés, l’écotype Maewa, est très photosensible contrairement aux six autres. La majorité des variables agronomiques (nombre de feuille, surface foliaire, biomasse et rendement en grain) ont été négativement affectées par un semis tardif (associés à des températures de l’air plus faibles). Cette caractérisation a permis de calculer pour la première fois au Sahel les principaux paramètres éco-physiologiques du mil (durée thermique des phases de développement, dynamique de la surface foliaire), indispensables aux modèles dynamiques de croissance des plantes tels qu’APSIM et DSSAT. Le modèle APSIM a permis de reproduire avec succès les variables agronomiques de 6 des 7 variétés de mil en condition nonlimitante d’apport en eau et en nutriments. De plus, le modèle APSIM a reproduit de manière satisfaisante la réponse de la variété améliorée CIVT à l’interaction de l’eau et de l’azote suite à l’apport combiné de résidus de récolte, de fumier de bétail et d’engrais minéral sur deux années ayant des pluviométries contrastées. Ceci a permis de renforcer la confiance dans l’utilisation du modèle APSIM comme outil d’aide à la décision dans l’environnement Sahélien. Sur base du modèle APSIM ainsi paramétrisé pour des conditions spécifiques de site et de variété, nous avons développé deux applications en matière d’aide à la décision. Une expérimentation factorielle numérique à long terme (23 ans) a révélé que l’application d’une dose modérée d’azote (15 kg N/ha) est plus appropriée dans le contexte d’une agriculture de subsistance que la recommandation habituelle de 30 kg N/ha. Bien qu’elle implique un rendement moyen à long terme inférieur à celui obtenu avec 30 kg N/ha, l’application de 15 kg N/ha garantit un plus grand rendement minimum pendant les années sèches extrêmes et une variabilité inter-annuelle plus faible, ce qui permet de garantir une meilleure sécurité alimentaire tout en réduisant la vulnérabilité des paysans. Dans la deuxième application du modèle, nous avons intégré des données SIG (parcellaire villageois, données climatiques et de pratiques de gestion de fertilité distribuées dans l’espace) et le modèle APSIM dans une simulation de rendement de mil sur 12 années. Ceci a permis de montrer que la dispersion spatiale des champs d’un ménage dans le terroir villageois (stratégie paysanne de gestion du risque) permet l’obtention de rendements plus uniformes entre ménages au sein du même village et de réduire la variabilité inter-annuelle des rendements de chaque ménage dans la région de Fakara au Niger. Notre recherche ouvre la voie à plusieurs autres applications de l’utilisation des modèles dynamiques de croissance des plantes dans les systèmes à base de mil au Sahel, par exemple dans l’étude de l’impact des changements climatiques et de prévention des crises alimentaires.

För att pådriva utvecklingen mot ett mer hållbart Gävle kommer Gävle Energi AB implementera en ny säsongsbaserad kapacitetsmodell ifrån årsskiftet 2019. Som ska skapa ekonomiska incitament för energieffektivisering i fastigheter inom Gävles fjärrvärmenät. Denna studie kartlägger värmeenergianvändningen i en fastighet som riskerar en förhöjd totalkostnad för fjärrvärmen till följd av den nya prismodellen. Målet med studien är att reducera värmeenergianvändningen utan att investera i fastigheten, vilket möjliggörs genom att värmeenergitillförseln till fastigheten regleras. Genom att programmera ett års historisk data av temperaturer, solinstrålning, el- och värmeeffekter så prognostiseras värmetillförseln på samma sätt som fastighetens styrsystem Kabona Eco-pilot. Styrsystemet tillämpar en flytande inomhustemperatur vilket bidrar till att fastighetens värmetröghet inkluderas i värmeregleringen. Studien inkluderar två prognoser som jämförs med den verkliga värmeenergianvändningen och den nya kapacitetsprismodellen. Prognos 1 är baserad på en årscykel och prognos 2 baseras på intervallet november 2017 till mars 2018. Syftet med prognos 2 är att tillämpa en strategisk värmelaststyrning för att sänka värmekapacitetsbehovet vid -10˚C. Prognos 1 indikerar att en värmeenergibesparing på 26% kan uppnås. Prognosen tar hänsyn till solinstrålning och vissa delar utav den interna värmegenereringen. Utan att Diös fastigheter AB investerat i några energibesparingsåtgärder prognostiseras en besparing på 44 700SEK under ett års drift. Fastigheten har idag energiprestanda energiklass D och kommer efter besparingen att kunna uppnå energiklass C. Prognos 2 indikerar att en kapacitetsreducering kan uppnås motsvarande 46,1% samtidigt som den rörliga värmeenergianvändningen minskar. Totalt sett finns en besparingspotential på 47,8% och 216 700 SEK under perioden 2017-11-01 till 2018-03-31, dock med följd att inomhustemperaturen sjunker. / In order to continue the development towards a more sustainable city of Gävle, Gävle Energi AB will implement a new season-based capacity model by the year 2019. It creates economic incentives for energy efficiency in real estate’s within Gävle's district heating network. This report investigates how the heat energy is used for a building that risks an increased heat energy cost, due to the new pricing model. The aim of the study is to reduce the heat energy usage without investing in the building, which is made possible by regulating the thermal energy supply to the building. By programming one year of historical data of temperatures, solar radiation, power- and heat effects the heat supply is forecasted the same way as the building's control system Kabona Eco-pilot is working. The control system applies a floating indoor temperature, which contribute that the thermal inertia of the building is included in the heat load control. The study includes two forecasts that are compared to the actual heat energy use and the new capacity price model. Forecast 1 is based on an annual cycle and forecast 2 is based on the range of November 2017 to Mars 2018. The aim of forecast 2 is to apply a strategic heat load control to reduce the heat capacity needed at -10˚C. Forecast 1 indicates a potential heat energy saving of 26% even though Diös Fastigheter AB does not invest in any energy saving technology. A saving of approximately 44 700 SEK is forecasted for the annual cycle. The building has an energy class D and has the potential to achieve energy class C after the change of control system parameters. Forecast 2 indicates a potential capacity reduction corresponding to 46,1% while the variable heat energy consumption decreases. Overall, there is an approximated heat energy saving potential of 47,8%, which corresponds to 216 700 SEK, during the range of 2017-11-01 to 2018-03-31. Due to the consequence of a lower indoor temperature.

Following wildfires, plant materials are direct-seeded to limit erosion and annual weed invasion. Seedlings often fail to establish because selected plant materials are not always well adapted to local soil moisture and temperature conditions. In an effort to help improve plant materials selection and to evaluate sites potential revegetation, we have worked toward developing methodology to predict germination and root growth based on site specific soil moisture and temperature conditions. First, we characterized the seedbed environment of 24 sagebrush (Artemisia spp.) steppe sites throughout the Intermountain West to determine the wet-thermal time of five temperature ranges relevant to germination response and thermal-time model accuracy (Chapter 1). Second, we predicted potential germination for 31 plant materials at those same sites (Chapter 2). Third, in preparation to predict root growth at multiple sites, we characterized the drying patterns and the associated plant-available water for in the seedling root zone across nine woodland (Juniperus spp. and Piñus spp.) sites (Chapter 3). For all of these studies, we determined the effects of tree reduction and tree infilling phase at time of tree reduction. Our key findings are that seedbeds generally sum most wet-thermal time at temperature ranges where the germination rates fit thermal accumulation models quite well (R2 ≥ 0.7). The majority of plant materials summed enough wet-thermal time for a potential germination at most sites during the fall, early spring, and late spring. Soil drying primarily occurs from the soil surface downward. Drying rates and Plant available water associated with the first drying event increased with increasing soil depth. Root zone (1-30 cm) plant-available water increased before and decreased after the first spring drying event with increasing soil depth. Tree removal with increasing pretreatment tree infilling phase generally added progress toward germination, plant available water, and wet-thermal time in the seedbed and root zones of the sagebrush steppe in the Great Basin. Because soil moisture and temperature does not appear to be limiting for potential germination, combining germination and root growth models to create a more comprehensive model may allow for a more robust prediction for seedling survival. For either root growth or combined germination and root growth models, plant available water and wet-thermal time before the first spring drying period hold the most potential for successfully predicting seedling survival.

La germination est un processus clé qui conditionne la régénération des plantes dans leur milieu ainsi que leur distribution. Connaître les conditions thermique et hydrique qui permettent aux plantes de germer est un préalable nécessaire à l’identification des menaces qui pèsent sur elles et tout particulièrement dans un contexte de changement climatique. Les modèles en temps thermique et temps hydrique permettent de prédire la phénologie de germination sur le terrain en fonction des conditions climatiques dans l’environnement de la graine dépassant des valeurs seuil de température et de potentiel hydrique de base, Tb et Ψb (i.e. respectivement la température minimale et le potentiel hydrique minimum permettant la germination).Dans ce travail de thèse, il est donc question d’étudier l’écophysiologie de la germination à l’aide de ces modèles à deux échelles taxonomiques : (i) celle des plantes à graines et (ii) à l’échelle du genre Silene de la région PACA. Dans les deux cas le but est d’évaluer les contraintes évolutives des traits de réponse au climat de la germination ainsi que leurs liens avec les contraintes morphologiques et phénologiques des plantesLes résultats de cette thèse montrent un fort signal phylogénétique des traits de germination de la température de base et une plus grande labilité pour le potentiel hydrique de base quelle que soit l’échelle taxonomique considérée. En revanche, les liens avec les traits des plantes, tels que la masse des graines, sont plus variables et dépendent à la fois de l’origine biogéographique et de la longévité des espèces. / Germination is a key process in plant reproduction, a critical and irreversible phase conditioning the regeneration and distribution of plants. Understanding how temperature and water act on germination, is major step prior to identify risks plants may undergo under warming climate. Thermal time and hydrotime modelling of germination are useful tools to predict germination in the field as a function of climatic conditions above threshold value of temperature and water potential (respectively base temperature, Tb, and base water potential, Ψb) in a seed’s environment. This PhD thesis aimed at studying germination ecophysiology at two contrasted taxonomic scales: (i) for all seed plants and (ii) at the restricted level of the genus Silene in the Provence Alpes Côte d’Azur region. In both cases the objective was to evaluate evolutionary implications of the germination traits, Tb and Ψb and their link with plant morphological and phenological constraints. This work is structured in three parts : (I) Temperature but not moisture response of germination shows phylogenetic contraints while both interact with seed mass and life span ; (II) Germination ecophysiology in the Silene genus : thermal time and hydrotime models ; (III) Comparative ecology of Silene germination : relation with plant traits and climate.The mains results of this work show strong evidences of phylogenetic signal in base temperature and greater lability for base water potential at both taxonomic scales. The links with plant traits such as seed mass depend on biogeographical origins and life span.