This thesis addresses the issue of interactions between neighbouring plants by looking at theory and models used in the study of wild plants with a view to applying them in the design of agroforests. In Part I difficulties of designing mixed crop stands are considered. Grime's model of the ecological strategies pursued by wild plants is described and its potential usefulness pointed out. Experimental results are presented suggesting that stress tolerant trees may interfere less with an understorey component than do competitive trees through the different patterns of spatial occupation manifested by their roots. Part II describes a statistical method to determine how any measurable attribute of one plant depends on the proximity and/or other characters of neighbouring plants. The method overcomes the need for unfeasibly large numbers of treatments encountered by conventional field trial methods. The method has the potential to offer a firm basis for the design of optimized plant production systems; and will also allow ecologists to detect and quantify interactions between wild plants in the field. Part III, using concepts of Evolutionary Game Theory, examines the question of cooperation in plants: both between the green plant and its associated vesicular-arbuscular mycorrhizal (VAM) fungi; and between neighbouring green plants connected by common VAM fungal hyphae. Exploring the implications for plants of Axelrod and Hamilton's (1981) Game Theoretic approach to the evolution of cooperative behaviour, it examines a logical problem in the view that the relationship between a green plant and associated VAM fungus is mutually beneficial. That the association is of mutual benefit would be insufficient to explain its persistence, and the fact that it does persist tells us something about its structure. It is shown that no logical paradox exists in postulating the simultaneous existence of competition for resources and of resource-sharing cooperation between a given pair of neighbouring green plants; and that at least a certain minimal type of cooperation may be deemed to exist between connected plant neighbours. Putting together findings from two fields - direct nutrient transfers and biotic specialisation - solves problems for both, and provides evidence for inter-plant cooperation. Possible evolutionary stages through which cooperation could have passed are discussed. Given this theory it can no longer safely be assumed that plants do not cooperate, and experimental results are presented suggesting that they may be able to. Scientific and economic implications are indicated for all three areas covered. Fertile ground exists for further research and suggestions are made for directions and methods.

Brazil is the world's sixth largest cocoa producer with 270,000 tonnes of cocoa produced per year. In a world with an increasing demand for chocolate, but with agriculture threatened by climate change, the chocolate industry is worried about a possible shortage of cocoa. Furthermore, growing cocoa is a main cause of deforestation. However, in the state of Bahia, Northeast Brazil, cocoa is grown in traditional agroforests called 'cabrucas' which maintain a forest cover. Cocoa, an understorey crop, is planted under the shade of native Atlantic Forest trees and exotic fruit trees introduced by the farmers. These cabrucas have high conservation value but very low cocoa yield. In my thesis I investigate the factors limiting cocoa yield and how to increase yield in cabrucas. I explore the role of shade trees and the nutrient dynamics in litterfall. Finally, I explore the risk that climate change could represent for cocoa production in the future by looking at the effects of an unexpected drought caused by an El Niño Southern Oscillation (ENSO) event between November 2015 and May 2016. My study is based on data collected in permanent transects in 32 randomly chosen cabruca farms in Barro Preto a municipality of Bahia over a period of three years. I also established littertraps in 10 cocoa farms where I intensively studied nutrient dynamics and cocoa yield per tree over 12 months. My results showed that unproductive trees, low cocoa tree density, high shade cover and high cocoa mortality due to drought were the main factors limiting cocoa yield in cabrucas. Surprisingly, adding fertilisers to the cocoa trees did not increase yield. This suggests that there is no nutrient deficiency in cabrucas. In the farms, I found 69 species of shade trees for an average density of 125 ± 32 trees per hectare. Half of the species of shade trees were Atlantic Forest species of conservation value. The litterfall experiment showed the shade tree species and the quantity of litterfall produced, can affect the number of cocoa pods per tree. In cabrucas, a higher number of cocoa pods was found on cocoa trees under shade trees than under no shade. Finally, I showed that the exceptionally severe ENSO-related drought caused 80% loss in yield and 11% cocoa tree mortality in Barro Preto. Climate models predict an increased frequency of strong ENSO events in the future. Farmers in Bahia are not prepared to face regular drought events. The 2015/16 drought affected the dynamics of cocoa production in Brazil: it accelerated the decrease of extensive wildlife-friendly cocoa production in Bahia whereas it increased the development of cocoa production in intensive low shade plantations in the state of Pará. This suggests that climate change could be a threat to traditional cocoa agroforests in Bahia. Developing wildlife-friendly certification schemes and Payment for Ecosystem Services to internalise the value of forest conservation and to encourage farmers to maintain their shade trees could save cabruca systems from going extinct.

L’étude de la phénologie des plantes est primordiale pour comprendre leur réponse aux changements globaux. Alors que de nombreuses études ont été consacrées à la phénologie aérienne, les difficultés d’observations de la phénologie des parties sou terraines d’une plante, font que leurs déterminants sont encore trop peu connu. La dynamique racinaire est considérée comme jouant un rôle clef dans le cycle et la séquestration du carbone dans le sol, et il est aujourd’hui important de surmonter les difficultés méthodologiques afin de mener des études sur la dynamique racinaire sur plusieurs années en conditions non-contrôlées. Notre premier objectif ici était donc de mettre au point et d’évaluer différentes techniques d’observation de la croissance racinaire sur le terrain. Le modèle choisi pour cela est le noyer hybride (Juglans L.), en système agroforestiers. L’utilisation du scan incorporé au smartphone s’est avéré être le meilleur compromis pour l’acquisition d’image à partir de rhizotrons, excepté en cas d’automatisation de la prise d’images, où la caméra automatique constitue la meilleur alternative (jusqu’à 4 mois d’autonomie). Notre deuxième objectif était de déterminer en milieu naturel les facteurs prédominants de la dynamique racinaire. Nous avons en particulier (i) testé l’hypothèse de la synchronicité des phénologies aériennes et racinaires de la plante, (ii) évalué l’effet de fluctuations climatiques sur la dynamique racinaire dans des environnements contrastés (climats méditerranéen, océanique, continental), (iii) et cherché à comprendre si cette réponse aux facteurs externes était conditionnée par la typologie racinaire. Les résultats ont permis de montrer l’indépendance des phénologies aériennes et racinaires, mais la synchronisation des croissances racinaires et radiale du tronc. Le principal facteur influençant la dynamique racinaire est la température du sol, et à moindre mesure l’humidité du sol avec des effets contrastés selon le climat. Les réponses des dynamiques racinaires aux variables environnementales sont propres à chaque site, avec un fort impact de l’ordre topologique sur les taux d’initiation et de survie. Ces résultats permettront non seulement une meilleur compréhension du jouait par les systèmes racinaires sur le cycle du carbone, mais aussi l’amélioration des modèles écophysiologiques. De futurs études sont néanmoins nécessaires d’autres études sont attendues pour renforcer les connaissances acquises dans ce projet, sur la compréhension des déterminants de l’initiation, de la croissance, et de la longévité racinaire des arbres, notamment via la création de bases de données et l’utilisation de méta-analyses / The study of phenology is primordial to understand tree response to climate change. Although many studies have examined shoot phenology, the difficulties in observing root system growth have resulted in a poor understanding of root phenology. As root system dynamics are considered as playing a major role in carbon cycling and sequestration, it is necessary to overcome methodological difficulties, so that root demography can be studied in the field and over several years. Our first objective was therefore to develop and evaluate methods for studying root system growth in the field. Studying mature hybrid walnut (Juglans L.), growing in agroforests, We showed that smartphone scanners are the best adapted tool for acquiring high quality images of tree roots growing in field rhizotrons. However, time-lapse cameras were good alternatives when a fully automated method was required (up to 4 months autonomy). Our second objective was to determine the main drivers of walnut hybrid root growth in field conditions. In particular, (i) We hypothesized that shoot and root phenologies were asynchronous, (ii) We evaluated the effect of environmental factors on root growth along a latitudinal gradient comprising three climates (Mediterranean, oceanic and continental) and (iii) We determined how phenology and environmental factors influenced root dynamics depending on root morphology and topology. Results show that flushes of fine root growth are not synchronized with budburst and leaf expansion, but are synchronized with stem and coarse root radial growth. Soil temperature was on the whole the main driver of root growth, and to a lesser extent, soil humidity, but which had contrasting effects on root growth. Root topological order had a major influence on root response to environmental variables, reflected in root elongation, production and longevity. Results will be highly useful not only for a better understanding of the role that root systems play in the carbon cycle, but also for tree ecophysiological models. Future studies should expand the knowledge gained here into a global understanding of the drivers of tree root initiation, growth and longevity, through the creation of databases and the use of meta-analyses.

nÃo hà / Diante da expansÃo dos cultivos agroecolÃgicos e da permanÃncia de Ãreas de aplicaÃÃo da agricultura convencional no semiÃrido, fez-se necessÃrio um estudo cientÃfico para a detecÃÃo, atravÃs de uma anÃlise comparativa, das principais diferenÃas entre as modalidades, observando o espaÃo local em suas caracterÃsticas peculiares e impactos. Objetivamos analisar as prÃticas agrÃcolas em propriedades de uso convencional e agroecolÃgica em duas Ãreas de um mesmo municÃpio - Nova Olinda/CE, com as mesmas caracterÃsticas geofÃsicas e que hà mais de dez anos faziam uso de prÃticas especÃficas de cultivo. Tratou-se de um estudo exploratÃrio-descritivo com uma abordagem quanti-qualitativa, utilizando-se para a coleta de dados: formulÃrio, observaÃÃo direta sistemÃtica, entrevista, coleta e anÃlise de solo. Em relaÃÃo Ãs tÃcnicas de cultivo, o modelo agroflorestal destacou-se por utilizar o policultivo e o consÃrcio com outras plantas, onde se incluem em torno de 29 espÃcies nativas, a incorporaÃÃo de resÃduos orgÃnicos, o roÃo seletivo e o plantio direto. Outras tÃcnicas que foram igualmente importantes nesse sistema e amplamente utilizadas por este agricultor foram: coleta e extraÃÃo (frutos, raÃzes, folhas, favos, etc.), as quais envolvem a fruticultura, apicultura e cultivo de hortaliÃas. Neste modelo de cultivo dispensou-se o uso de agrotÃxico, pois a intenÃÃo era alcanÃar o controle natural por meio da cadeia biolÃgica, utilizando espÃcies vegetais. Como benefÃcios dessas tÃcnicas identificaram-se a manutenÃÃo do microclima adequado à biologia do solo; o controle de ervas daninhas e da erosÃo; maior permeabilidade Ãs chuvas; proteÃÃo do solo contra investidas direta do sol, da chuva e do vento; estabilizaÃÃo de ravinas e voÃorocas; e promoÃÃo da biodiversidade. Jà no modelo convencional, encontramos como o tipo de cultivo adotado o consÃrcio e a monocultura, onde as prÃticas de preparaÃÃo da terra incluem o roÃo e o destocamento, a queimada, a utilizaÃÃo de arados mecÃnicos e a capinaÃÃo. Como consequÃncias foram identificadas uma diminuiÃÃo abrupta da biodiversidade, reduÃÃo na capacidade de restituiÃÃo vegetal e desnudaÃÃo do solo com consequente aumento do Ãndice de erosÃo e empobrecimento da camada fÃrtil. Os Ãndices mineralÃgicos de fertilidade do solo sÃo maiores no Sistema Agroflorestal (SAF), e, que dada as tÃcnicas empreendidas pelo agricultor, tÃm uma tendÃncia a elevarem-se ao contrÃrio das empreendidas na Ãrea do Sistema Convencional (SC), que em geral empobrecem o solo, podendo assim levÃ-lo a Ãndices ainda mais crÃticos. Em relaÃÃo à produtividade, o Sistema Agroflorestal tambÃm destacou-se graÃas Ãs suas diferentes produÃÃes, que asseguram um maior nÃmero de fontes de renda, com uma consequente lucratividade. Compreendemos assim, que, em termos de produtividade e rentabilidade, o SAF apresentou-se mais vantajoso para o agricultor por diversos motivos, dentre os quais destacaram-se: mais fontes de rendas, maior produÃÃo por tarefa e mais seguranÃa em termos de produÃÃo tanto a nÃvel ambiental como econÃmico. Identificamos que o Sistema Agroflorestal apontou excelentes resultados e que superou a nÃvel de conservaÃÃo dos solos e dos ecossistemas, bem como de produtividade e rentabilidade, o Sistema Convencional adotado. Com isso, indicamos o modelo agroflorestal como rentÃvel e favorÃvel à adoÃÃo para os agricultores do semiÃrido nordestino. / In the face of the expansion of agroecological cultivation and the hitherto use of areas of application of conventional agriculture in the semi-arid region, it showed to be necessary a deeper and more scientific study for the detection, through a comparative analysis, of the main differences between these two types of cultivation, observing the local space in its peculiar characteristics and impact. This study aimed to analyze the agricultural practices in properties of conventional and agroecological use in two areas of the same municipality â Nova Olinda/CE, with the same geophysical characteristics and that they have been using the specific practice of cultivation for more than ten years. This was an exploratory and descriptive study with a quanti-qualitative approach, using for data collection: formulary, systematic direct observation, interview, collection and analysis of soil. In relation to the techniques of cultivation, the agroforest model was put in evidence for using polyculture, partnership with other plants in which was included around 29 native species, incorporation of organic remains, selective cut and direct planting. Other techniques which were equally important in that system and widely used by this cultivator were: collection and extraction (fruits, roots, leaves, honeycombs, etc.), which involve horticulture (fruits and vegetables) and apiculture. In this model of cultivation, agrochemicals were not used, since the intention was to reach the natural control through the biological chain using vegetable species. As the benefits of those techniques, it was identified the maintenance of the microclimate which was adequate for the biology of the soil; control of weeds and erosion; greater permeability to water; protection of the soil against direct sunlight, rain and wind; stabilization of eroded areas; and promotion of biodiversity. In the conventional model, mono and partnership are the adopted types of cultivation; the practices of soil preparation include the cut and removal of remaining stems, fire, use of mechanical rakes and weeding. As consequences, it was identified an abrupt diminishing of the biodiversity, reduction in the capacity for vegetal restitution and soil bareness with the consequent increase in the erosion index and diminishing of the fertile layer. The mineralogical indexes of soil fertility are higher in the Agroforest System (AFS), and, due to the techniques used by the cultivator, they have a tendency to increase; on the contrary, in the Conventional System (CS), the techniques used generally diminish the soil fertility, thereby taking the soil to more critical indexes. In relation to productivity, the Agroforest System was put in focus due to its different productions, which provide a higher number of sources of income with consequent profitability. It was grasped then that in terms of productivity and profitability, the Agroforest System was more advantageous to the cultivator due to various reasons, among them it was highlighted: more sources of income, greater production per hectare and more security and terms of production, not only at the environmental level but also at the economic one. It was identified that the Agroforest System showed excellent results and it outperformed at the level of soil and ecosystem conservation, as well as in productivity and profitability, the adopted Conventional System. Therefore, the Agroforest model is considered profitable and favorable to the adoption by the cultivators from the semi-arid region of the Brazilian North-East

O café é uma importante comoditty agrícola de exportação no mundo e o Brasil ocupa posição de destaque, como o maior produtor e exportador mundial. Contudo, é um produto bastante vulnerável às flutuações de preço no mercado. Nesse sentido, a diversificação da produção pode ser uma importante estratégia para manter o equilíbrio econômico da propriedade. O presente estudo teve como objetivo avaliar o efeito de diferentes níveis de radiação solar no crescimento e na produção do cafeeiro (Coffea arabica L.), bem como na qualidade do café. A pesquisa foi conduzida no período de janeiro de 2002 a agosto de 2005, na ESALQ/USP, em Piracicaba-SP (22°42’30" S, 47°38’00" W - altitude 550 m). O experimento foi composto de seringueira adulta clone PB 235 e cafeeiro cv. Obatã IAC 1669-20, plantado em janeiro de 2002 no sub-bosque do seringal, interfaceando as árvores de seringueira e em monocultivo (pleno sol). Os tratamentos foram constituídos por um gradiente de luminosidade de 25, 30, 35, 40, 45, 80, 90, 95, 98, 99 e 100%, formado por linhas de cafeeiros plantados a diferentes distâncias das árvores de seringueira, tanto dentro como interfaceando o seringal e em monocultivo (pleno sol). O delineamento experimental utilizado foi de blocos casualizados, com 11 tratamentos e 4 repetições. As variáveis analisadas foram relativas ao crescimento (diâmetro do caule e da copa, altura inicial da copa e altura da planta, área foliar total, massa seca acima do solo, número de ramos e nós e comprimento dos internódios, área foliar individual, TAL, RAF, AFE, IAF, TCA, TCR) e produção do cafeeiro (produtividade, rendimento e índice de bienalidade de produção), bem como referentes a qualidade do café (maturação dos frutos, classificação dos grãos por peneira e análise sensorial da bebida). O crescimento e a produtividade do cafeeiro, assim como a qualidade do café foram modificados pela disponibilidade de irradiância. O crescimento e a produtividade aumentaram com o incremento de irradiância. O incremento de irradiância a partir de 70% praticamente não alterou o acúmulo de massa seca da parte aérea da planta e sob elevado sombreamento a massa seca foi muito baixa. A produtividade do cafeeiro alterou muito pouco a partir de 60% de radiação e a aproximadamente 70% se estabilizou. De modo oposto, houve uma melhoria da qualidade do café à medida que foi intensificado o sombreamento, obtendo-se frutos com maior uniformidade de maturação, grãos de maior tamanho e bebida de melhor qualidade. / Coffee is an important exporting agricultural commodity in the world and the Brazil is in a leading position as the world’s largest exporting producer. However, the product is quite vulnerable to market price floating. In that scenario, diversifying products can be an important strategy to keep the economic equilibrium of the property. The aim of this study was to evaluate the effect of different levels of solar radiation on the growth and production of coffee (Coffea arabica L.), as well as coffee quality. The research was conducted from January 2002 to August 2005 at ESALQ/USP, in Piracicaba-SP (22°42’30" S, 47°38’00" W - altitude 550 m). The experiment comprised an adult rubber tree, clone PB 235, and coffee cv Obatã IAC 1669-20, grown in January 2002 in a rubber tree understory, interfacing with rubber trees and monocrop trees (sun exposed). The treatments included a 25, 30, 35, 40, 45, 80, 90, 95, 98, 99 and 100% luminosity gradient, formed by coffee plant rows grown at different distances from the rubber trees, both within and interfacing with the rubber tree plantation and monocrop (full sun). The experimental design was that of random blocks with 11 treatments and 4 replications. The analyzed variables were those related to growth (trunk and crown diameter, initial height of canopy, plant height, total leaf area, above-ground dry mass, number of branches and nodes and internodes length, single leaf area, NAR, LAR, SLA, LAI, G and RGR,) and coffee production (productivity, yield and rate of biannual production), as well as those related to coffee quality (fruit maturity, bean size and sensorial analysis of the beverage). The coffee growth and productivity, as well as the quality, were modified by irradiance availability. The growth and the productivity increased with the solar radiation increment. The irradiance increment starting from 70% practically did not change the accumulation of the plant above-ground dry mass and under high shading the dry mass was very low. The productivity of the coffee plant chanded a little starting from 60% of radiation and the approximately 70% were stabilized. Instead, a coffee quality improvement was observed as shading was intensified, with more maturation uniformity fruit, larger grains and better quality drink.

No description available.

O café é uma importante comoditty agrícola de exportação no mundo e o Brasil ocupa posição de destaque, como o maior produtor e exportador mundial. Contudo, é um produto bastante vulnerável às flutuações de preço no mercado. Nesse sentido, a diversificação da produção pode ser uma importante estratégia para manter o equilíbrio econômico da propriedade. O presente estudo teve como objetivo avaliar o efeito de diferentes níveis de radiação solar no crescimento e na produção do cafeeiro (Coffea arabica L.), bem como na qualidade do café. A pesquisa foi conduzida no período de janeiro de 2002 a agosto de 2005, na ESALQ/USP, em Piracicaba-SP (22°42’30” S, 47°38’00” W – altitude 550 m). O experimento foi composto de seringueira adulta clone PB 235 e cafeeiro cv. Obatã IAC 1669-20, plantado em janeiro de 2002 no sub-bosque do seringal, interfaceando as árvores de seringueira e em monocultivo (pleno sol). Os tratamentos foram constituídos por um gradiente de luminosidade de 25, 30, 35, 40, 45, 80, 90, 95, 98, 99 e 100%, formado por linhas de cafeeiros plantados a diferentes distâncias das árvores de seringueira, tanto dentro como interfaceando o seringal e em monocultivo (pleno sol). O delineamento experimental utilizado foi de blocos casualizados, com 11 tratamentos e 4 repetições. As variáveis analisadas foram relativas ao crescimento (diâmetro do caule e da copa, altura inicial da copa e altura da planta, área foliar total, massa seca acima do solo, número de ramos e nós e comprimento dos internódios, área foliar individual, TAL, RAF, AFE, IAF, TCA, TCR) e produção do cafeeiro (produtividade, rendimento e índice de bienalidade de produção), bem como referentes a qualidade do café (maturação dos frutos, classificação dos grãos por peneira e análise sensorial da bebida). O crescimento e a produtividade do cafeeiro, assim como a qualidade do café foram modificados pela disponibilidade de irradiância. O crescimento e a produtividade aumentaram com o incremento de irradiância. O incremento de irradiância a partir de 70% praticamente não alterou o acúmulo de massa seca da parte aérea da planta e sob elevado sombreamento a massa seca foi muito baixa. A produtividade do cafeeiro alterou muito pouco a partir de 60% de radiação e a aproximadamente 70% se estabilizou. De modo oposto, houve uma melhoria da qualidade do café à medida que foi intensificado o sombreamento, obtendo-se frutos com maior uniformidade de maturação, grãos de maior tamanho e bebida de melhor qualidade. / Coffee is an important exporting agricultural commodity in the world and the Brazil is in a leading position as the world’s largest exporting producer. However, the product is quite vulnerable to market price floating. In that scenario, diversifying products can be an important strategy to keep the economic equilibrium of the property. The aim of this study was to evaluate the effect of different levels of solar radiation on the growth and production of coffee (Coffea arabica L.), as well as coffee quality. The research was conducted from January 2002 to August 2005 at ESALQ/USP, in Piracicaba-SP (22°42’30” S, 47°38’00” W – altitude 550 m). The experiment comprised an adult rubber tree, clone PB 235, and coffee cv Obatã IAC 1669-20, grown in January 2002 in a rubber tree understory, interfacing with rubber trees and monocrop trees (sun exposed). The treatments included a 25, 30, 35, 40, 45, 80, 90, 95, 98, 99 and 100% luminosity gradient, formed by coffee plant rows grown at different distances from the rubber trees, both within and interfacing with the rubber tree plantation and monocrop (full sun). The experimental design was that of random blocks with 11 treatments and 4 replications. The analyzed variables were those related to growth (trunk and crown diameter, initial height of canopy, plant height, total leaf area, above-ground dry mass, number of branches and nodes and internodes length, single leaf area, NAR, LAR, SLA, LAI, G and RGR,) and coffee production (productivity, yield and rate of biannual production), as well as those related to coffee quality (fruit maturity, bean size and sensorial analysis of the beverage). The coffee growth and productivity, as well as the quality, were modified by irradiance availability. The growth and the productivity increased with the solar radiation increment. The irradiance increment starting from 70% practically did not change the accumulation of the plant above-ground dry mass and under high shading the dry mass was very low. The productivity of the coffee plant chanded a little starting from 60% of radiation and the approximately 70% were stabilized. Instead, a coffee quality improvement was observed as shading was intensified, with more maturation uniformity fruit, larger grains and better quality drink.

No description available.

No description available.

No description available.