Western boreal peatlands have diverse ground covers of Sphagnum and brown mosses that have important hydrological controls on peatland-atmosphere interactions. Since peatland mosses are non-vascular, their shoot structural morphologies and community growth forms affect the storage and fluxes of water that are critical for maintaining productivity and evaporative functions. While many of the mechanisms of capillary rise are fairly well understood for Sphagnum mosses, there is less information on the water dynamics in communities of Tomenthypnum nitens, a dominant brown moss species in northern rich fens. This study investigated how the different hydrophysical characteristics of moss and peat profiles of T. nitens from a rich fen and intermixed Sphagnum angustifolium and Sphagnum magellanicum, from a poor fen affect capillary flow and water retention to support evaporation and productivity; and how different groundwater and atmospheric sources of water affected these processes. Laboratory investigations indicated volumetric water content and gross ecosystem productivity decrease with water table depth for both mosses without the advent of precipitation, with Sphagnum capitula retaining 10-20% more water than T. nitens due to its moss structure and pore connectivity with the water table. Consequently, Sphagnum capillary rise was sufficient to sustain both high pore-water pressures for evaporation and high water content for productivity at all water table depths due to a gradual shift in average water-retaining pore sizes with depth. The structure of T. nitens moss turfs, consisting of live shoots and a basal layer of old, partially decomposed shoots sometimes overlying well-decomposed peat makes capillary rise more difficult, requiring extremely low matric pressures at the surface, sometimes causing desiccation of the uppermost portions of moss shoots, and hence reduced productivity. Additional nocturnal sources of atmospheric water from dew, distillation, and vapour fluxes provide small, but potentially critical sources of water to rewet desiccated moss shoots for early morning productivity for both T. nitens and Sphagnum mosses. Investigations in the field, however, indicated that with frequent precipitation to rewet the moss and the turf base to refill large pores, evaporative demands at the T. nitens moss canopy could drive capillary flow from the water table to maintain adequate θ for productivity. T. nitens mosses also can grow in turfs disconnected from the underlying iii peat, so that the basal layer temporarily retains water from precipitation for capillary rise. Thus, while capillary connection of the T. nitens moss turf with the underlying peat and water table is not critical to maintain productivity, it grows in a relatively large range of elevations from the water table, compared to Sphagnum and feather mosses. Rewetting of the capitula and the raising of the water table by precipitation provided higher water matric pressures within the moss matrix, and along with high evaporative demands, provided the mechanisms for sufficient capillary flow for productivity. Thus, Sphagnum could grow in habitats far from the water table like feather mosses, although the latter did not require capillary rise for productivity. Furthermore, disequilibrium between water vapour and liquid in the pores of T. nitens in the near-surface suggested pressures calculated with the Kelvin equation may not provide an accurate characterization of actual matric pressures in the moss. However, as the disequilibrium is caused by vapour pressure gradients between the moss and the atmosphere, it is likely a driving factor that helps maintain vapour and capillary water fluxes to provide moisture for T. nitens and other mosses. These results illustrate hydrological mechanisms that explain how moss growth form and habitat are linked. As such, the Sphagnum and T. nitens mosses are well adapted to maintain capillary in their poorly drained habitats in western boreal peatlands.

A agricultura familiar da região Sudeste do Pará tem sido apontada como uma das grandes modificadoras da cobertura vegetal amazônica, isso ocorre devido a intensidade de suas práticas e o manejo inadequado dos solos. Esses pequenos estabelecimentos familiares têm apresentado problemas com a disponibilidade dos recursos hídricos, qualidade dos solos, consequentemente, baixa produção vegetal. Perante esta problemática, o objetivo desta tese foi o de conhecer o solo a partir de caracterização morfológica, química e físico-hídrica de duas topossequências, uma com vegetação nativa e outra com pastagens em área de agricultura familiar. A fim de alcançar o objetivo, a presente pesquisa foi composta das seguintes etapas: (i) caracterização morfológica, química e física dos solos em duas topossequências e tipologia dos horizontes com utilização da análise estrutural; (ii) estudos físico-hídricos dos solos, curva de retenção de água no solo e condutividade hidráulica, a partir dos compartimentos encontrados pela análise estrutural; (iii) análises hidroestruturais dos solos, a partir de metodologia ainda não aplicada em solos amazônicos, as curvas de retração; e (iv) relação de parâmetros físico-hídricos e hidroestruturais dos solos com uso de análise multivariada. Os resultados obtidos permitiram a visualização dos solos em diferentes escalas, partindo de uma escala macro, onde foi observado a presença de 7 compartimentos diferenciados a partir dos atributos morfológicos, físicos e hídricos dos horizontes, até uma escala micro, de compreensão da porosidade do solo, e mudança de volume do solo quando o mesmo perde água. Observou-se um incremento de argila em profundidade que foi importante para as principais diferenciações encontradas. A curva de retenção de água no solo e a curva de retração do solo mostraram que a textura foi o atributo que mais contribuiu aos resultados encontrados. Na curva de retenção de água no solo, os parâmetros ? e n, foram sensíveis ao teor de argila e porosidade do solo, respectivamente. A curva de retração, apresentou sensibilidade à estrutura do solo, granular e em blocos subangulares, mais comuns nestes solos, relacionados também ao teor de argila. A oscilação do lençol freático contribuiu com o aparecimento de mosqueados, e indicou a deficiência de drenagem dos perfis, principalmente nos horizontes com maiores teores de argila. Espera-se que este estudo contribua ao entendimento do comportamento do solo, sob floresta e pastagem, bem como a nível mais geral, seja uma base de dados para futuros trabalho de modelagem e simulação de novos cenários de uso do solo em áreas de agricultura familiar. / Family agriculture has been identified as a major modifier of Amazonian vegetation cover, this is due to the intensity of their practices and inadequate soil management. These small family establishments have had problems with the availability of water resources, soil quality, consequently, low crop production. Faced with this problem, the main objective of this thesis was to know the soil from morphological, chemical and physical water characterization, of topossequences two, one with native vegetation and other with pastures in the area of family farming. To achieve the objective, the present research consisted of the following steps: (i) morphological and physical characterization of soils in two topossequences and typology of horizons with the use of structural analysis; (ii) hydrophysical, from soil water retention curve and hydraulic conductivity, with soil studies of the seven main compartments found by structural analysis; (iii) hydrostructural soil analysis in Amazonian soils, and (iv) the relations of soil hydrophysical and hydrostructural data using multivariate analysis. The results confirmed the presence of 7 compartments differentiated by their morphological, physical and hydraulic properties, to a micro scale, the understanding of and volume change soil when it loses water. There was an increase in depth of clay that was important for the major differences found. The soil water retention curve and soil shrinkage curve showed that the soil texture was determined its parameters and the slopes of their curves. The parameters ? and n, were sensitive to clay content and soil porosity, respectively. The shrinkage curve showed a sensitivity to the structure of the soil, subangular blocks and granular more common these soils, also related to the clay content. The fluctuation of the water table contributed to the appearance of mottling, and indicated a deficiency of drainage profiles, especially in horizons with higher clay. This study contributes to the understanding of the relations between the soils studied along the topossequence, and contributes with data that will be the basis for simulating new land use scenarios in areas of family agriculture.

A agricultura familiar da região Sudeste do Pará tem sido apontada como uma das grandes modificadoras da cobertura vegetal amazônica, isso ocorre devido a intensidade de suas práticas e o manejo inadequado dos solos. Esses pequenos estabelecimentos familiares têm apresentado problemas com a disponibilidade dos recursos hídricos, qualidade dos solos, consequentemente, baixa produção vegetal. Perante esta problemática, o objetivo desta tese foi o de conhecer o solo a partir de caracterização morfológica, química e físico-hídrica de duas topossequências, uma com vegetação nativa e outra com pastagens em área de agricultura familiar. A fim de alcançar o objetivo, a presente pesquisa foi composta das seguintes etapas: (i) caracterização morfológica, química e física dos solos em duas topossequências e tipologia dos horizontes com utilização da análise estrutural; (ii) estudos físico-hídricos dos solos, curva de retenção de água no solo e condutividade hidráulica, a partir dos compartimentos encontrados pela análise estrutural; (iii) análises hidroestruturais dos solos, a partir de metodologia ainda não aplicada em solos amazônicos, as curvas de retração; e (iv) relação de parâmetros físico-hídricos e hidroestruturais dos solos com uso de análise multivariada. Os resultados obtidos permitiram a visualização dos solos em diferentes escalas, partindo de uma escala macro, onde foi observado a presença de 7 compartimentos diferenciados a partir dos atributos morfológicos, físicos e hídricos dos horizontes, até uma escala micro, de compreensão da porosidade do solo, e mudança de volume do solo quando o mesmo perde água. Observou-se um incremento de argila em profundidade que foi importante para as principais diferenciações encontradas. A curva de retenção de água no solo e a curva de retração do solo mostraram que a textura foi o atributo que mais contribuiu aos resultados encontrados. Na curva de retenção de água no solo, os parâmetros ? e n, foram sensíveis ao teor de argila e porosidade do solo, respectivamente. A curva de retração, apresentou sensibilidade à estrutura do solo, granular e em blocos subangulares, mais comuns nestes solos, relacionados também ao teor de argila. A oscilação do lençol freático contribuiu com o aparecimento de mosqueados, e indicou a deficiência de drenagem dos perfis, principalmente nos horizontes com maiores teores de argila. Espera-se que este estudo contribua ao entendimento do comportamento do solo, sob floresta e pastagem, bem como a nível mais geral, seja uma base de dados para futuros trabalho de modelagem e simulação de novos cenários de uso do solo em áreas de agricultura familiar. / Family agriculture has been identified as a major modifier of Amazonian vegetation cover, this is due to the intensity of their practices and inadequate soil management. These small family establishments have had problems with the availability of water resources, soil quality, consequently, low crop production. Faced with this problem, the main objective of this thesis was to know the soil from morphological, chemical and physical water characterization, of topossequences two, one with native vegetation and other with pastures in the area of family farming. To achieve the objective, the present research consisted of the following steps: (i) morphological and physical characterization of soils in two topossequences and typology of horizons with the use of structural analysis; (ii) hydrophysical, from soil water retention curve and hydraulic conductivity, with soil studies of the seven main compartments found by structural analysis; (iii) hydrostructural soil analysis in Amazonian soils, and (iv) the relations of soil hydrophysical and hydrostructural data using multivariate analysis. The results confirmed the presence of 7 compartments differentiated by their morphological, physical and hydraulic properties, to a micro scale, the understanding of and volume change soil when it loses water. There was an increase in depth of clay that was important for the major differences found. The soil water retention curve and soil shrinkage curve showed that the soil texture was determined its parameters and the slopes of their curves. The parameters ? and n, were sensitive to clay content and soil porosity, respectively. The shrinkage curve showed a sensitivity to the structure of the soil, subangular blocks and granular more common these soils, also related to the clay content. The fluctuation of the water table contributed to the appearance of mottling, and indicated a deficiency of drainage profiles, especially in horizons with higher clay. This study contributes to the understanding of the relations between the soils studied along the topossequence, and contributes with data that will be the basis for simulating new land use scenarios in areas of family agriculture.

In der Wintersaison 2005-2006 wurde ein Split-Split Plot-Design Feldversuch mit drei Wiederholungen für jede Behandlung von Kartoffeln, als Indikatorpflanze, unter den ariden Bedingungen der Kharga Oasis in der Westlichen Wüste von Ägypten durchgeführt. Drei Bewässerungslevel (100 %, 80 %, und 60 % of ETc) mit Tröpfchenbewässerung, zwei Mulchvarianten (Zuckerrübenabfall ohne und mit 24 ton ha-1) und 4 Kompostraten (0, 12, 24, und 36 ton ha-1) wurden getestet. Generell und als Ergebnis einer Regressionsanalyse der Versuchsvarianten ohne Kompost war die beste Variante die Tröpfchenbewässerung bei 80% ETc unabhängig ob gemulcht oder nicht gemulcht wurde. Andererseits die Variante mit 36 t Kompost und mit 24 t Mulch ergab die besten Ergebnisse bei 60% of ETc sowohl beim Ertrag und den Ertragskomponenten, bei den hydrophysikalischen Eigenschaften, bei der Bodenwasserretention, beim Wasserverbrauch, bei den Pflanzenkoeffizienten, der Wassernutzungseffizienz, der Düngernutzungseffizienz sowie beim Nettogewinn. Wird die Rate der Kompostgabe aber auf 24 ton ha-1 reduziert, die höchsten Nettogewinne bei der lokalen Vermarktung als auch signifikant beim Kartoffelexport werden erreicht. / Under the arid condition of Kharga Oasis in the Western Desert of Egypt, split-split plot design field experiment with three replications for each treatment using potato as an indicator plant was carried out during the winter season 2005-2006. Three irrigation levels of water regime (100 %, 80 %, and 60 % of ETc) using drip irrigation system, two treatments of soil covering (sugar cane wastes at the rate of 0 and 24 ton /ha) and compost rates (0, 12, 24, and 36 ton ha-1) were tested. In general and as a result of the triple interaction among the studied treatments, using drip irrigation either with soil mulching or not, 80 % of ETc as a water regime was the best. On the other hand, reducing drip irrigation water level at 60% of ETc in mulched soil that was treated with 36 ton ha-1 of compost recorded the highest values yield and yield components, soil hydrophysical properties, soil water retention, water consumption, crop coefficients, water economy water use efficiency, fertilizer use efficiency, net profit. But reducing the compost rate to 24 ton ha-1 attained the highest net profit for local potato consumption and achieved the best significant net profit for exportation.