No description available.

Le système racinaire, lien essentiel entre la plante et le sol quoi qu'essentiellement invisible, reste encore aujourd'hui peu étudié dans son ensemble. Les plantes étant ancrées au sol via leur système racinaire, leurs facultés d'adaptation et de survie sont donc très dépendantes de leurs capacités à savoir tirer profit de l'espace qui les entoure, notamment par l'intermédiaire de leur système racinaire. Certains arbres font néanmoins partie des plus grands et plus anciens êtres vivants de la planète, preuve s'il en est de leur capacité d'adaptation au milieu dans lequel ils poussent et aux changements environnementaux pouvant survenir dans le temps. Dans le cas des plantations, les contraintes anthropiques imposées se heurtent parfois aux limites de cette formidable capacité d'adaptation. Les travaux développés dans la première partie de cette thèse font l'objet de deux articles publiés et se concentrent sur une revue bibliographique des connaissances sur l'enracinement profond. Le rôle vital du système racinaire pour la plante est ainsi mis en avant ainsi que ses fonctions dans le continuum sol-plante-atmosphère. Son rôle essentiel, souvent sous-estimé dans le stockage du carbone, est également abordé. Les différentes techniques permettant d'accéder aux systèmes racinaires in situ sont passées en revue et nous présentons la technique du puits d'accès que nous avons utilisé pour observer les racines jusqu'à 5 mètres de profondeur. Nous avons également développé nos propres outils de prise de vue par l'intermédiaire de scanner à plat ainsi qu'un outil d'analyse d'images ( IJ_Rizo) aujourd'hui disponible en ligne.Dans la deuxième partie du mémoire, nous nous consacrons à l'étude du système racinaire de l'hévéa adulte (Hevea brasiliensis) dans le nord-est de la Thaïlande. Premier producteur mondial de caoutchouc naturel, la Thaïlande a fortement développé ses plantations d'hévéas allant jusqu'à étendre son exploitation au-delà de sa zone climatique naturelle, dans des zones à fortes contraintes hydriques. Dans ce contexte, nous avons étudié la saisonnalité et la dynamique des racines fines pendant trois ans ainsi que leur contribution au cycle du carbone. Nous avons pu mettre en évidence la continuité de la dynamique racinaire indépendamment des périodes de défoliation mais en lien avec la saisonnalité de la pluviométrie. Nous avons également pu caractériser la faible différenciation de la dynamique racinaire de 0 à 4,5 mètres de profondeur dans un tel contexte. La troisième partie de la thèse concerne l'étude du teck (tectona grandis), espèce endémique d'Asie du Sud-Est, et notamment du Laos dans la région de Luang Prabang. Le développement de sa culture sous forme de plantations mono-spécifiques se poursuit depuis les années 80. En appliquant la technique d'exclusion de pluie pendant 2 ans sur des arbres d'une plantation d'une vingtaine d'années, nous avons observé l'influence du régime de précipitations sur l'enracinement. Un arrêt pratiquement total de croissance des racines en surface et en profondeur a ainsi été mis en évidence. Nous concluons, dans le cas d'espèces à une forte dépendance à la ressource en eau de surface, à un impact direct sur l'état physiologique et une stagnation de la croissance des troncs. Certains individus ont démontré une capacité d'adaptation en modifiant leur cycle de foliation / défoliation accompagné d'une reprise de la croissance des troncs lors de la deuxième année du régime de sécheresse imposé. Nous avons également démontré l'importance de l'enracinement fin pour le stockage du carbone qui, dans ce contexte, représente plus de 45 % du carbone total, soit environ le double des données publiées dans la littérature.Les données obtenues pour les espèces étudiées dans ce mémoire pourront être utilisées pour la modélisation de scenarios simulant le changement climatique et le changement d'usage des terres. / The root system is essential but essentially invisible. Plants are anchored to the soil through their root system; their adaptation and survival abilities are highly dependent on their ability to learn to take advantage of the space that surrounds them. Certain trees are nevertheless some of the largest and oldest living species on the planet- evidence of their ability to adapt to changes in their environment. Within managed anthropogenic constraints, particular species are vulnerable. It is clear that a wide range of parameters are likely to influence the root system and its operation, which offers many entry points to improve our understanding of a root's capacity for expansion, its dynamics, its role within the plant itself and within the soil plant atmosphere continuum. Available data on the extent and dynamics of plant roots includes several thousand references. However, the vast majority of these observations were made within the first meter of the soil profile. Data acquisition for the fine and/or deep roots is currently limited by constraints of time and financial resources. To overcome this lack of information, while trying to assess root dynamics under different environmental conditions, many models have been developed. However, it is still difficult to describe the complexity of root development in the community and to integrate its "plasticity".To understand such a complex environment, we must work toward establishing a definition of objectives and the tools necessary to develop and implement them. The work developed in the first part of this thesis is the subject of two articles and focuses on a literature review about deep roots. The vital role of the root system for the plant is well highlighted, as is its impact as a link within the atmosphere. We discuss the role of deep roots in carbon storage, which is critical and often underestimated. The different techniques for accessing the root systems in situ are also considered, and we present our access technique for observing the roots down to depths of five meters. We have also developed tools for shooting through a flatbed scanner and image analysis ( IJ_Rizo ) now available online.In the second part of the thesis, we focus on the study of root systems of adult rubber trees (Hevea brasiliensis L. RRIM 600) in the northeast of Thailand. Thailand has greatly expanded its acreage to extend its operations beyond its natural climate zone, into areas of high water stress. In this context, we studied the seasonality and dynamics of fine roots for three years and their contribution to the carbon cycle. We were able to highlight the continuity of root dynamics during independent periods of defoliation, yet link these to the seasonality of rainfall. We were also able to characterize the low differentiation of root dynamics at 0 to 4.5 m of depth in this context.The third part of the thesis concerns the study of teak particular to the region of Luang Prabang, Laos. By applying the rain exclusion technique for 2 years on a plantation of twenty-year-old trees, we observed the influence of precipitation patterns. During the period of water stress, an almost total cessation of root growth, at the surface and significant depths, has been highlighted. We conclude that in the case of species with a high dependence on water resources there is a direct impact on the physiological state and stagnated trunk growth. Some individuals have demonstrated an ability to adapt by changing their foliation/defoliation cycle, accompanied by a resumption of trunk growth during the second year of imposed drought. We also demonstrated the importance of rooting as a means of carbon storage, which in this context represents more than 45% of total carbon- roughly double the amount published in other literature .The data obtained for the species studied in this paper can be used for modelling scenarios simulating climate change and changing land use.

No description available.

The growth and productivity of kauri (Agathis australis (D. Don) Lindl.) in even-aged single-species planted stands and mixed-aged second-growth natural stands has been studied. Stand-level models of height, basal area and whole-tree volume were developed. Kauri growth and productivity in planted stands up to 83 years old were compared to that of natural stands that were up to 196 years of age. Within natural stands, the effect of thinning treatments on growth and productivity was also assessed. Models of growth and productivity were initially developed for each of the three different kauri stand types independently (planted, second-growth unthinned and thinned). Combined data sets allowed for the development of single models that were able to fit all stands. A Schumacher equation with local slope parameter and asymptote bounded at 45 m gave the best fit for height growth, while a von Bertalanffy-Richards equation in difference form with local slope parameter gave the best fit for basal area growth. Kauri in all stand types were found to be slow to establish with little height growth in planted stands for the first five years after planting, and for the first 25 years in natural stands. Similar trends were observed for basal area and whole-tree volume development. Models developed in this study are relevant only to kauri in the “ricker” or monopodial form irrespective of age, and for stands from 320-2000 stems/ha. Kauri growth and productivity in planted stands was substantively better than that in second-growth stands. Planted kauri had height increment of 0.4 m/yr for periods of up to 30 years. At age 50, planted kauri was predicted to be 20 m in height, over twice the height of kauri in natural stands, and to be 28.1 m by 100 years. Basal area at age 50 averaged 64.9 m2/ha for all planted stands, and was predicted to be 98.2 m2/ha at age 100. Whole-tree volume was predicted to increase by 11.7 m3/ha/annum for all stands, but was as high as 20.6 m3/ha/yr in one 70 year old stand. The maximum productivity of kauri was observed in one high-performing young kauri planted stand where whole-tree volume increment in excess of 30 m3/ha/yr were predicted for a period from age 15-30. Carbon sequestration was calculated from the volume model and predicted to be 316 t C/ha and 1168 t CO2/ha at age 100. Mortality of kauri in planted stands was as high as 3.9%/yr for individual stands, over their entire rotation to date. For all stands, mortality averaged 0.56%/yr. The highest mortality occurred in the years before the first assessment and averaged 0.64%/yr for all stands. From the first to the last assessment mortality averaged 0.30%/yr. Where mortality in individual stands was above the average rate the dominant cause was drought. The growth and productivity of kauri in second-growth stands was only marginally improved by thinning to reduce competition. The volume removed in thinning operations had not been replaced in the (up to) 50 years since thinning treatments were applied. At age 150, the predicted height of kauri in unthinned control and thinned stands were identical at 25.9 m. Basal area at age 150 was 64.5 m2/ha in unthinned stands and 52.6 m2/ha in thinned stands. Whole-tree volume was predicted to be 681 m3/ha in unthinned and 549 m3/ha in thinned stands. Volume increment peaked at 5.2 m3/ha/yr in unthinned stands and 4.7 m3/ha/yr in thinned stands. This study has shown that the worst growth and productivity of kauri in planted stands was better than that of the best natural stands. The difference in performance between plantation and second-growth kauri was most likely a result of a combination of lower site quality characteristics (soil type and fertility), stand structure and within-stand competition of natural stands. The data for planted kauri came from 31 permanent sample plots located in 25 planted stands. These stands ranged in age from 14-83 years at the last assessment, and ranged in stand density from 218-1800 stems/ha. The overall number of planted stands and plots from which data was available to develop models was small in comparison to many exotic forest species datasets. The majority of the planted stands were not silviculturally treated after planting, and considerable variation in establishment methods was recorded. The results of productivity from the models developed for planted kauri should therefore be considered to be conservative. The results of this study indicate an opportunity to grow kauri in plantations on good quality sites for the production of high quality sapwood timber over rotations of 60 years or less. They also indicate that second-growth stands will produce usable volumes of timber, but only over extended periods of time. To ensure that kauri in planted stands can meet the potential observed during the development of these models, a series of well-managed stands on a range of sites is urgently required where the effects of timely silviculture, including initial stand density, can be assessed, quantified and reported on. Further research on selection and breeding for the species would improve the early establishment and growth of planted kauri resulting in a reduced rotation length. Research on long-term management strategies that include continuous cover forestry may make the species an attractive proposition for carbon forestry and/or for the production of high quality, naturally durable heartwood. The dataset compiled for this study was the best data available. While it cannot as yet be used to develop prescriptions for the establishment and maintenance of planted kauri stands, it does provide clues and directions that should be pursued in further research, however.

Forest plantations in the UK are often established on seasonally waterlogged peaty gley soils which often require site preparation (drainage and mounding) to lower the water table and prepare planting positions. Substantial changes in the physical environment of peaty gley soils can accompany site preparation including fluctuations in soil temperature and soil moisture. These and other changes can all affect soil properties and decomposition processes and well as the dynamics of CO2, CH4 and N2O. A field experiment was established at Harwood Forest (NE England) to investigate the effects of three site management practices (drainage, mounding and fertilisation) frequently used for afforestation and replanting on peaty gley soils in the UK on soil properties and various of C and N, environmental variables (soil temperature, water content and water table height) and emissions of CO2, CH4 and N2O. The relationship between GHG emissions and environmental variables was also examined. The experiment was laid out in a factorial split-plot design. Drainage decreased C and N concentration in the 10 cm soil layer. The soil bulk density in the 0 to 20 cm soil layer was increased by mounding. Drainage and fertilisation increased soil CO2 efflux, whereas mounding did not affect soil CO2 efflux. All three practices affected soil CH4 fluxes with drainage reducing the fluxes and mounding and fertilisation increasing the fluxes. Nitrous oxide emissions were significantly affected by mounding and fertilisation, with mounding decreasing emissions and fertilisation increasing emissions. Soil temperature was the main environmental factor controlling soil respiration in this site. Over the two years study drainage and fertilisation increased the total greenhouse budget by 13.1% and 97.9%, while mounding caused a reduction of−17.6%. Drainage plus mounding reduced the total greenhouse budget by 6.9%, while drainage plus mounding plus fertilisation increased the total greenhouse budget by 101.8%. There is a potential for up-scaling GHG emissions from newly drained peaty gley for inclusion in the UK Land Use Land-Use Change and Forestry (LULUCF) Greenhouse Gas Inventory. However up-scaling and evaluation of the net emissions requires high quality data from different sites newly drained for afforestation. More studies are needed if net fluxes from newly drained sites are to the included in the LULUCF Greenhouse Gas Inventory.

Darbo tikslas: nustatyti augavietės, įveisimo ir apsaugos technologijų įtaką ąžuolo želdinių būklei. Darbo objektas: Kėdainių miškų urėdijos Dotnuvos bei Skaistgirio girininkijose esantys paskutinio dešimtmečio ąžuolo želdiniai. Metodai: siekiant nustatyti augaviečių, įveisimo ir apsaugos technologijų įtaką ąžuolo želdinių būklei tirti ąžuolo želdiniai Nds; Lds; Nfs; Lfs augavietėse su 2 arba 3 pakartojimais. Naudota miško želdinimo darbų, želdinių ir žėlinių apskaitos ir vertinimo metodika, esančia teisės akte Miško atkūrimas ir įveisimas (teisės aktų rinkinys) – Vilnius, 2005, 116 – 121 p. Vadovaujantis šia metodika tirti 7 metų amžiaus ąžuolo želdiniai laikinų apskaitos aikštelių metodu (100 – 400 m ploto), jas išdėstant plote galimai vienodais atstumais, tipingose vietose želdavietės įstrižainių kryptimis. Apskaitos aikštelių skaičius priklausė nuo sklypo ploto: kai sklypo plotas 3 ha ir mažesnis apskaitos aikštelės apėmė ne mažiau 5 % sklypo ploto, kai 4 – 5 ha – 4 %, kai 6 – 10 ha – 3 %, kai daugiau nei 10 ha – 2 %. Apskaitos aikštelėse vertinti šie rodikliai: - vidutinis ąžuolo želdinių aukštis (10 cm tikslumu), pridedant prie jų analogiško aukščio ąžuolo savaiminukus, augančius vienas nuo kito ne arčiau kaip 0,7 m atstumu; - gyvybingų ąžuoliukų skaičius; - elninių žvėrių pažeidimai pagal pažeidimo tipą; - ligų pažeidimai. Tyrimo rezultatai apdoroti dispersinės analizės metodais. Rezultatai: atliktais tyrimais nustatyta, kad didžiausias vidutinis aukštis ir... [toliau žr. visą tekstą] / The aim of our investigation: to determine the infuence of different sites tipes, planting and protecion technologies on the oak plantations quality. Object of the investigation: 7 years oak plantations in Kėdainiai State Forest Enterprise. Methods: Our investigation was carried out in 100 - 400 m sample plots according to the methodology of statute of reforestation and afforestation in different types of forest sites (Nds; Lds; Nfs; Lfs). According to this metodology sample plots were set out in the diagonal direction on the 7 years oak plantations. Sample plots were used to determine: - middle height of oak stands; - density; - the intensity of injuries made by animals and pathogens. Investigation data was processed using methods of „ANOVA“. Results: it was determined that the greatest heigth of oaks plantations is in Nds and Nfs forest sites; forest sites has no significant effect on oak seedlings density, but it was estimated significant effect on viability of oak plantations; the prevalence of foliar pathogen Oaks midlew is significantly higher in L hydrotope; there is no significant effectiveness between individual shelters and circle-shaped fence; soil preparation has significant effect on viability of oak plantations in L hydrotope.

La culture du palmier à huile en milieu villageois prend de plus en plus d'ampleur dans les zones tropicales où elle contribue pour une part importante à l'économie des pays. Au Bénin, les palmeraies villageoises sont en forte expansion dans un climat particulier caractérisé par des déficits hydriques annuels élevés. Les caractéristiques assez particulières de ces palmeraies villageoises, comme l'association des cultures vivrières dans les jeunes palmeraies, l'absence de fertilisation minérale durant tout le cycle de culture et l'exportation de tout ou partie de la biomasse recyclable, nous interrogent sur la durabilité du système de production. L'étude a été conduite dans le département du Plateau au sud-est du Bénin (2°30 - 2°45 E et 6°35 - 7°45 N). Une première étape de diagnostic de typologie des palmeraies a permis de constater que les palmeraies villageoises appartiennent majoritairement à des petits producteurs dont les faibles moyens financiers ne permettent pas de planter de grandes superficies, ni d'appliquer une fertilisation minérale aux palmiers. Les antécédents culturaux sont pour la plupart des champs de cultures vivrières. Au jeune âge, les palmeraies sont associées à des cultures vivrières très variées. Les pratiques de restitution des sous produits de transformation, limitées à quelques grands producteurs et les modes de gestion des feuilles d'élagage, distinguent les palmeraies villageoises. La gestion des feuilles d'élagage commence à 7 ans d'âge des palmeraies et va d'une restitution quasi-totale en andain à une restitution nulle de ces feuilles au sol.Dans ce contexte, le mode de gestion des feuilles d'élagage dans les palmeraies villageoises peut induire des effets différents sur le système sol-plante, et son impact agronomique et environnemental mérite d'être exploré. A cet effet, la typologie des palmeraies a orienté le choix d'une chronoséquence de palmeraies représentant les deux modes contrastés de gestion des feuilles d'élagage : la restitution totale en andain (RT) et la restitution nulle (RN). Cette chronoséquence a servi aux études comparatives de l'effet de ces modes sur les compartiments sol et plante du système de production.Dans le compartiment sol, les stocks de matière organique, les paramètres physico-chimiques, l'activité microbienne et le statut de la matière organique ont été étudiés. Les études au niveau de la plante ont concerné dans un premier temps les paramètres de développement (densité, longueur et surface) des racines primaires, secondaires et fines. Et dans un second temps, les biomasses et minéralo-masses aériennes de la plante. Les études de biomasse aérienne ont nécessité la mise au point de méthodes non destructrices basées sur des équations allométriques d'estimations des biomasses de la feuille et du tronc. / Smallholder oil palm plantations are taking increasingly importance in tropical areas where the crop contributes significantly to the economy of the countries. In Benin, smallholder oil palm plantations are in expansion in a particular context characterized by high annual water deficits. Smallholder plantations are characterized in particular by the association of food crops with the young palms, the absence of mineral fertilization throughout the growing cycle and the removal of all or part of recyclable biomass. These specific characteristics raise some questions about the sustainability of the production system. The study was conducted in the region of Plateau located in southeast of Benin (2º 30-2º 45 E and 6 ° 35-7 ° 45 N). A first step diagnosis of the plantations' typology showed that small farmers own the major part of plantations. These small farmers have limited financial resources that neither allow them planting large areas nor applying mineral fertilizers. Food crops represent predominantly the previous cropping history of the plantations. The young palm trees are always associated with various food crops. Practices of mill residues recycling, limited to a few large producers, and the management of pruned fronds distinguish the smallholder plantations. Management of pruned fronds starts at 7 years old of the palm plantation. There are various ways of management of pruned fronds, from total recycling (RT) to no recycling at all (RN).In this context, the management of pruned oil palm fronds in smallholder plantations may induce different effects on the soil-plant system, and its agronomic and environmental impact deserves to be investigated. For this purpose, the typology of plantations allows to choose a chronosequence of palm plantations representing two contrasting ways of managing pruned fronds: RT of fronds piles and RN practices. This chronosequence was used to compare the effect of management of pruned fronds on soil and plant compartments.In the soil compartment, organic matter stocks, chemical parameters, microbial activity and status of organic matter were studied. The studies at the plant level concerned, first, the development parameters (density, length and surface area) of primary, secondary and thin roots; and second, the above ground biomass and mineral-mass of the plant. The studies of the aboveground biomass required to develop non-destructive methods based on allometric equations to estimate biomass of frond and trunk.On the agronomic view, the RT practice after 10 years of fronds recycling induced a significant effect on soil fertility parameters. Organic matter and nitrogen stocks at 0-50 cm depth increased by 70% and 50%, respectively, under frond piles compared to inter-rows without fronds. Surprisingly, the RN practice did not induce a decrease of organic matter stock over time. The increase of carbon and nitrogen stocks after 10 years of fronds recycling, improved soil parameters on the first 20 cm depth. The soil was enriched in organic matter (20gC.kg -1) and nitrogen (1.5gN.kg -1). The sum of exchangeable cations and cationic exchange capacity reached average values (7meq.100g -1) two times higher than the cases of no recycling of fronds. Calcium and magnesium contents increased while potassium contents are very low. The pH increased to 0.5 units and the soil shifted from acid to slightly acid status. Total recycling of fronds induced an increased soil microbial activity witch changed the quality of soil organic matter. So, the carbon content of fine organic fractions (< 20μm) increased to 40% at 0-5 cm and to 15% at 20-30 cm, compared to the no recycling of pruned fronds.

Radiative transfer models (RTM) have been successfully used to simulate the effect of forest structural and biochemical characteristics, such as tree sizes and shapes, leaf area index (LAI), leaf angle distribution (LAD), on the canopy radiative budget. One particular use of RTM is the analysis of the reflected light by the canopy, which can be measured by remote sensing techniques. RTM allows a physically based interpretation of the reflectance quantity measured by satellite and can help disentangling the multiple source of variation of the reflectance signal. The DART model - Discrete Anisotropic Radiative Transfer - is one of the most complex three-dimensional RTM, since it uses an accurate mathematical approach of physical processes and a great realism of the landscapes under simulation. Its main simulation outputs are the reflectance of the scene (e.g. a forest stand) at particular spectral wavelength from bottom and top of the atmosphere, the simulation of satellite images, and the simulation of localized radiative budget. Despite the DART potential in analyzing biophysical parameters from remote sensing data, few studies report its application in forest plantations in Brazil, which can have a large number of important field measurements to parameterize the model. The main objective of this project is to evaluate if the DART RTM can help understand the satellite-measured canopy reflectance of Eucalyptus plantations and in particular if DART RTM can improve LAI estimation rather than use only empirical models, as spectral vegetation indices. DART model was parameterized using extensive in situ data obtained from a clonal test, part of the EucFlux project. The specific objectives were: i) parameterize the DART model at different growth stages and for different clonal materials of Eucalyptus plantations and compare simulated reflectance with high resolution satellite images acquired on the same site; ii) analyze the relationship between the Leaf Area Index (LAI) and Spectral Vegetation Indices (SVI) based on empirical relationships, and then use the DART model; iii) analyze the advantage and drawbacks of using a generic relationship or a clone-specific relationship between LAI and SVI, and find other criteria for grouping the genotypes in the same. In Chapter 2, we demonstrated the good performance of DART to simulate canopy reflectance of Eucalyptus forest plantations. The simulated reflectance was similar to those measured by very high resolution images from satellite, despite some discrepancies found in the near infrared region. Then, in Chapter 3, we showed that empirical relationships between LAI and SVI were able to give a reasonable precision for generic relationships; however, genotype-scale relationships gave even better results. The same methodology applied on a DART simulated dataset lead to the same conclusions. An intermediate possibility of grouping the genotypes regarding their litter or leaf optical properties gave intermediate performance. We finally concluded about the superiority of NDVI to estimate LAI using a genotype-specific calibration. Overall, DART simulated datasets created in this work enable to calibrate different LAI -SVI relationships in terms of genotypes, sensors and acquisition characteristics. / Modelos de transferência de radiação (MTR) têm sido utilizados com sucesso para simular o efeito das características estruturais e bioquímicas florestais, como tamanhos de árvores e formas, índice de área foliar (IAF), distribuição angular das folhas (DAF) e sobre o balanço de radiação. Um uso particular do MTR é a análise da radiação refletida pela copa, o que pode ser medido através de técnicas de sensoriamento remoto. O MTR pode permitir a interpretação física da quantidade de reflectância medido por satélite, e pode ajudar a diferenciar as múltiplas fontes de variação do sinal de reflectância. O modelo DART - Discrete Anisotropic Radiative Transfer - é um dos modelos tridimensionais de transferência de radiação mais complexos, uma vez que utiliza uma abordagem matemática precisa e um grande realismo na simulação das paisagens. Seus principais resultados de simulação são a reflectância da cena (por exemplo, um povoamento florestal) em determinado comprimento de onda espectral em relação ao topo e à base da atmosfera, a simulação de imagens de satélite e a simulação do balanço de radiação. Apesar do potencial do DART na análise de parâmetros biofísicos de paisagens florestais a partir de dados de sensoriamento remoto, existem poucos estudos sobre sua aplicação em povoamentos florestais no Brasil; que podem dispor de um elevado número de medições de campo importantes para a parametrização do modelo. O principal objetivo deste estudo foi avaliar se o DART pode ajudar a compreender o comportamento da reflectância do dossel das plantações de eucalipto oriunda de dados de imagens de satélite e, em particular, se DART pode melhorar a estimativa do IAF ao invés do uso somente de modelos empíricos como índices espectrais da vegetação. O DART foi parametrizado com extensos dados de campo adquiridos em um experimento com testes clonais do Projeto Eucflux. Os objetivos específicos foram: i) parametrizar o modelo DART em diferentes idades e com diferentes materiais genéticos de plantações de eucalipto e comparar a refletância simulada com imagens de satélite de alta resolução adquiridas no mesmo local; ii) analisar a relação entre o Índice de Área Foliar (IAF) e Índices Espectrais de Vegetação (IEV\'s) com base em relações empíricas, e, em seguida, usando o modelo DART; iii) analisar as vantagens e as limitações do uso de uma relação genérica ou uma relação específica do genótipo entre IAF e IV e encontrar outros critérios para agrupar os genótipos. No Capítulo 2 foi demonstrado bom desempenho do DART para simular a reflectância do dossel das florestas plantadas de eucalipto. As refletâncias simuladas foram semelhantes com as obtidas pelas imagens de satélite de alta resolução, apesar de algumas discrepâncias encontradas na região do infravermelho próximo. No Capítulo 3, foi mostrado que as relações empíricas entre os IEV\'s e os IAF\'s foram capazes de estimar com razoável precisão para as relações genéricas dos plantios. Contudo, as estimativas por genótipo deram resultados superiores. A mesma metodologia foi aplicada em um conjunto de dados simulados pelo DART com as mesmas conclusões. Uma possibilidade intermediária de agrupar os genótipos foi em função das propriedades ópticas da serapilheira ou das folhas, com desempenhos intermediários. Nós concluímos sobre a superioridade do NDVI para estimar o LAI usando uma calibração específica para cada genótipo. Em termos mais gerais, os dados simulados com o modelo DART utilizados neste trabalho permitiram calibrar diferentes relações IAF-IEV em função dos genótipos, sensores e características de aquisição.

O plantio de árvores para finalidades industriais é um tipo de uso do solo que gera controvérsias em vários países. Ao transformarem paisagens, afetam comunidades rurais alterando suas realidades material e simbólica. A redução da vazão dos corpos d\"água é um dos mais recorrentes pontos de discussão. No Brasil, o eucalipto é a espécie arbórea mais utilizada para fins industriais. Impulsionados pela produção de celulose, esses plantios estão presentes na região Vale do Paraíba Paulista. Esta pesquisa procurou identificar e analisar como as representações do efeito dos plantios de eucalipto nas vazões de cursos d\"água são construídas nos territórios rurais dos municípios de Caçapava, Santa Branca e Cunha. Entende-se que compreender essas visões é uma forma de reconhecer os conhecimentos de indivíduos que possuem experiências fundamentadas nesses territórios, interagindo com essa atividade econômica e lidando com as consequências advindas da mesma. Para tanto, realizamos uma série de noventa entrevistas semiestruturadas dialogando com as teorias das representações sociais e do construcionismo ambiental. Como resultado, compreendemos que as representações sociais que fundamentam este problema ambiental não são fixas, se transformam em conjunto com a sociedade e em diálogo com as modificações econômicas e técnicas que caracterizam o setor, bem como com as alterações dos contextos históricos, sociológicos, ambientais e culturais que distinguem a região. / Tree plantation for industrial purposes is a controversial land use in several countries. By transforming landscapes, they affect rural communities, changing their material and symbolic realities. Reduced waterflow is one of the most contentious issues. In Brazil, eucalyptus is the most commonly used tree species for industrial purposes. Driven by pulp production, these plantations are found in the Paraíba Valley region, São Paulo. The aim of this study was to identify and analyze how the representations of eucalyptus plantations effect on waterflows are constructed in the rural territories of Caçapava, Santa Branca and Cunha municipalities. It is recognized that understanding these visions is a way of acknowledging individuals who have grounded experiences in these territories, interacting with this economic activity and dealing with the consequences that arise from it. To do so, we carried out a series of ninety semi-structured interviews based on the theories of social representations and environmental constructionism. As a result, we understand that the social representations that underpin this environmental problem are not fixed. They change along with society and are linked to the economic and technical changes that characterize the sector, as well as the changes of historical, sociological, environmental and cultural contexts that distinguish the region.

La production de bois à large échelle à des fins industrielles occupe des vastes terrains, modifie les paysages, les écossystèmes et provoque des changements aux sociétés locales. À Imbaú, Paraná, les données indiquent que plus de la moitié de sa surface est occupée par des plantations de bois. Par contre, les chiffres qui font référence à cette occupation n’expriment guère les impacts ressentis par les sujets qui vivent dans ces espaces. Dans ce sens, cette étude a pour objectif de comprendre quels impacts socio-environnementaux ce sont générés par l’expansion des plantations de bois et les changements dans les dynamiques locales. On a eu l’intention de comprendre cette réalité à travers les yeux de ceux qui sont impliqués dans ou touchés par l’activité. Pour cela, ont été adoptées les références de l’étude qualitatif ainsi que les études à propos des conflits socio-environnementaux. Les données ont été générées par des interviews, l’observation directe et un carnet de terrain. Dans le contexte étudié, les sujets ressentent les impacts résultants de l’expansion des plantations des arbres à partir de leurs espaces de vie, où se produisent les formes matériel et symbolique d’utiliser l’environnement. Cependant, les sujets adoptent des différents stratégies par rapport aux impacts comme l’adhésion aux plantations de bois, des processus de résistance et la contestation qui signale l’existence du conflit. À guise de conclusion, l’étude indique que le conflit socio-environnemental établi à Imbaú comprend, d'un coté, l’engagement des sujets qui vivent dans ces espaces pour préserver leurs lieux de vie en face de l’expansion des plantations de bois et, de l’autre, les transformations générées par cette expansion telles que la spécialisation productive, l’homogénéisation du paysage et la dégradation matériel et symbolique des espaces. / A produção de madeira em larga escala para fins industriais ocupa extensas áreas, transforma a paisagem, os ecossistemas e provoca mudanças nas sociedades locais. Em Imbaú, Paraná, estimativas do IBGE apontam que mais da metade da área do município está ocupada por plantações de espécies madeireiras chamadas genericamente, no contexto deste trabalho, de plantações de madeira. Entretanto, os números referentes a essa ocupação não expressam os impactos sentidos pelos sujeitos inseridos nesses espaços. Nesse sentido, este estudo tem por objetivo compreender que impactos socioambientais são gerados pela expansão das plantações de madeira e como afetam as dinâmicas locais. Buscou-se compreender essa realidade a partir do olhar dos sujeitos envolvidos e/ou atingidos pela atividade de produção de madeira no Município de Imbaú, Paraná. Para tanto, foi adotada como abordagem a pesquisa qualitativa e por referencial teórico os estudos sobre conflitos socioambientais. A geração de dados em campo foi realizada por meio de entrevistas semiestruturadas, observação direta e registro em diário de campo. No contexto estudado, observa-se que os impactos gerados pela expansão das plantações de madeira são compreendidos pelos moradores locais a partir de seus espaços de vida na medida em que afetam as formas material e simbólica de uso e apropriação do meio. Contudo, os sujeitos adotam diferentes estratégias em relação aos impactos dentre as quais a adesão ao cultivo de madeira se apresenta como forma de adaptação ao novo entorno e a contestação vocalizada pelo “grito dos atingidos” sinaliza processos de resistência e demarca a existência do conflito. Em suma, o estudo aponta que o conflito socioambiental instaurado pode ser compreendido como o embate pela continuidade dos espaços de vida empreendido pelos moradores locais em face da expansão dos espaços de produção de madeira caracterizados pela especialização produtiva, homogeneização da paisagem e esvaziamento material e simbólico desses espaços.