Dissertations / Theses on the topic 'Shifting cultivation'

Succession following shifting cultivation was studied in secondary forests (5 to 40 years old) and a primary forest in Bragantina region, Para, Brazil. Secondary forests covered 62% of the study area (89 km² ) and crops and pasture 18%. Soil analyses showed an increase in pH, exchangeable calcium, magnesium and potassium and a decrease of organic matter and exchangeable aluminium, immediately after burning. Organic matter and extractable phosphorus increased with forest age, exchangeable aluminium and potassium were the same in both secondary and primary forests and exchangeable calcium and magnesium remained higher in the secondary forests. The highest densities of individuals and the least basal area and height were found in the younger secondary forests. The number of woody species (≥5 cm dbh) 250-m2 plot ranged from 8 to 17 in the secondary forests and 17 to 27 in the primary forest. Ordination and classification of floristic data suggested four successional communities. The forests regenerated readily and studies showed: the largest seed bank (0-5 cm) in the 5-years-old forest (1190 ± 284 seeds m-2) and a decrease with age to 137 ±19 seeds m-2 in the primary forest; the highest seed rain in the 5-years-old forest (883 ± 230 seeds m-2) and least in the primary forest (220 ± 80); 46% of the smaller plants (≥1 m tall, < 5 cm dbh) were seedlings and 54% were sprouts in the 5-years-old forest but in the 10-years and 20-years-old forests, seedlings (81%) predominated; adult plants (≥5 cm db h) in 5 to 20-years-old plots regenerated mainly from sprouts. Even after about 90 years of shifting cultivation the region has the potential for forest regeneration and the soil nutrients are able to recover to values similar to those in the primary forest. This raises the hope that, if a land use plan for Bragantina could be implemented, then it would be successful.

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第17166号
農博第1960号
新制||農||1005(附属図書館)
学位論文||H24||N4716(農学部図書室)
29905
京都大学大学院農学研究科森林科学専攻
(主査）教授 大澤 晃, 教授 太田 誠一, 教授 北山 兼弘
学位規則第4条第1項該当

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第14690号
農博第1772号
新制||農||971(附属図書館)
学位論文||H21||N4463(農学部図書室)
UT51-2009-D402
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 縄田 栄治, 教授 舟川 晋也, 教授 太田 誠一
学位規則第4条第1項該当

Despite the long history of anxiety about shifting cultivation practices by small-scale farmers in Central African forests causing deforestation, this is the first study that examines the temporal and spatial dynamics of shifting cultivation landscapes and the influence of landscape configuration on secondary vegetation regrowth in fallows. This is important not least because, within the landscape matrix, fallow vegetation is crucial to alleviate effects of losses of forest vegetation, and biodiversity as well as negative impacts on carbon balance. Moreover, fallows provide food, beverage, fuel, building and medicinal products harvested from a diversity of plant species, whose value for local livelihoods is well known.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第5427号
農博第758号
新制||農||649(附属図書館)
学位論文||H5||N2561(農学部図書室)
UT51-93-F184
京都大学大学院農学研究科熱帯農学専攻
(主査)教授 重永 昌二, 教授 久馬 一剛, 教授 古川 久雄
学位規則第4条第1項該当

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A floresta Amazônica vem sendo ameaçada pelas mudanças no uso da terra para a expansão da fronteira agrícola, provocando uma simplificação taxonômica e funcional, e em consequência gerando impactos negativos na relação da biodiversidade e funcionamento dos ecossistemas. Assim, o objetivo principal desta pesquisa foi avaliar os efeitos dos modeladores ecológicos sobre a diversidade taxonômica e funcional (alfa e beta) e sua relação com funcionamento ecossitêmico durante a sucessão secundária de uma floresta Amazônica, no estado Amazonas, Venezuela. Por este motivo, esta pesquisa foi dividida em sete capítulos, dois capítulos para descrever os efeitos do padrão de uso da terra sobre a recuperação da diversidade e perda da resiliência florestal, dois capítulos para explicar os efeitos dos modeladores ambientais e antropogênicos sobre a diversidade taxonômica e funcional (alfa e beta) e os efeitos sobre o funcionamento ecossitêmico durante a sucessão, e três capítulos como recomendações para o manejo e conservação de florestas da Amazônia. Utilizamos dados de inventário de plantas de 63 parcelas (1000 m 2 , 20 x 50 m) em seis locais com florestas secundárias de cinco e 10 anos de regeneração depois de um até seis ciclos de agricultura itinerante para avaliar o efeito de diferentes intensidades de uso da terra, bem como a fertilidade do solo na recuperação da diversidade e estrutura da floresta. Também analisamos as mudanças na diversidade e composição das espécies arbóreas após um único ciclo de agricultura itinerante, utilizando dados de 45 parcelas distribuidas em quatro florestas secundárias (5, 10, 15, e 20 anos de idade após do cultivo) e uma floresta madura (> 100 anos). Dentro de cada área de amostragem se estabeleceram três parcelas de 1000 m 2 (20 x 50 m para árvores com DAP > 5 cm). Em cada área foi coletada uma amostra de solo a diferentes profundidades (0-10 cm, 10-30 cm). Assim, analisamos padrões ecológicos e modeladores ambientais da diversidade taxonômica e funcional (alfa e beta), e os efeitos do tempo de sucessão e qualidade do solo (fertilidade e textura) sobre a estocagem de biomassa acima do solo através da diversidade funcional e dominância funcional durante a sucessão secundária. Usamos diferentes métodos estatísticos e tipos de modelos para testar estas relações ecológicas. Neste estudo, demostramos como a intensidade do uso da terra induz uma perda de resiliência florestal, de forma contrária se evidencia que com disturbios intermediários depois de um único ciclo de agricultura ocorre uma rápida recuperação da diversidade, atingindo aproximadamente um 70% da riqueza de uma floresta madura depois de 20 anos. No entanto, a recuperação da composição das espécies nesse mesmo período atingiu uma média de 25% em relação à floresta madura. Nosso estudo mostra que a diversidade beta explica até 70% da variação na riqueza total de espécies entre os sítios, provavelmente devido a que as manchas desmatadas estão inseridas dentro de uma matriz de floresta madura. Este contexto ecológico também justifica o elevado turnover taxonômico durante a sucessão. Assim, a diversidade funcional foi menor do que a diversidade beta taxonômica, provavelmente devido a um menor turnover funcional em comparação com o turnover taxonômico. Nossos resultados proporcionam importantes evidências sobre relação biodiversidade-função ecossistêmica durante a sucessão secundária de uma floresta tropical Assim, os modelos de equação estruturais testados sobre dominância funcional e diversidade funcional, permitiram explicar variações na biomassa acima do solo de forma individual. O tempo de sucessão foi o melhor preditor para explicar variações da biomassa acima do solo em todos os modelos SEM explorados, seguidamente da textura solo que teve afeitos significativos positivos sobre a biomassa acima do solo, em comparação à fertilidade do solo que apresentou efeitos negativos e não significativos. Nosso estudo contribui no entendimento da relação BEF ao longo da sucessão secundária, e pode ajudar a predizer como as florestas tropicais respondarão aos cenários futuros de mudanças climáticas. Por esse motivo, discutimos que para aumentar a eficiência na implementação de estratégias REDD+ em florestas da Amazônia, é necessário compreender simultaneamente a relação de padrões e processos dos ecossistemas florestais com o sistema sócio-ecológico, através da análise de preditores biofísicos e antropogênicos, a partir de um nível local para uma escala regional.
The Amazon forest is being threatened by land use changes for the agricultural expansion, causing a taxonomic and functional simplification, and consequently generating negative impacts on the relation of biodiversity and ecosystem functioning. Thus, the main objective of this research was to evaluate the effects of ecological drivers on taxonomic and functional diversity (alpha and beta) and their relationship with ecosystem functioning during the secondary succession of an Amazon forest, in Amazonas state, Venezuela. For this reason, this research was divided into seven chapters, two chapters to describe the effects of the land use pattern on the recovery of diversity and loss of forest resilience, two chapters to explain the effects of environmental and anthropogenic drivers on taxonomic diversity and functional (alpha and beta) and effects on ecosystem functioning during the succession, and three chapters as recommendations for the management and conservation of Amazonian forests. We used plant inventory data from 63 plots (1000 m 2 , 20 x 50 m) at six sites with five and 10 year regeneration secondary forests after one to six cycles of shifting cultivation to evaluate the effect of different intensities of use land, as well as soil fertility in the recovery of forest diversity and structure. We also analyzed changes in the diversity and composition of tree species after a single cycle of shifting cultivation, using data from 45 plots distributed in four secondary forests (5, 10, 15, and 20 years old after cultivation) and a mature forest (> 100 years). Within each sampling area three plots of 1000 m2 (20 x 50 m for trees with DBH> 5 cm) were established. In each area a soil sample was collected at different depths (0-10 cm). Thus, we analyzed ecological and environmental drivers and patterns of taxonomic and functional diversity (alpha and beta), and the effects of stand age and soil quality (fertility and texture) on the storage of above-ground biomass through functional diversity and functional dominance during the secondary succession. We use different statistical methods and types of models to test these ecological relationships. In this study, we show how the intensity of land use induces a loss of forest resilience. On the contrary, it is evident that with intermediate disturbances after a single cycle of agriculture a rapid recovery of diversity occurs, reaching 70% of the richness of one mature forest after 20 years. However, the recovery of the species composition in the same period reached an average of 25% in relation to the mature forest. Our study shows that beta diversity accounts for up to 70% of the variation in total species richness among sites, probably because deforested patches are embedded within a mature forest matrix. This ecological context also justifies the high taxonomic turnover during the succession. Thus, the functional diversity was lower than the taxonomic beta diversity, probably due to a lower functional turnover in comparison to the taxonomic turnover. Our results provide important evidence on the relation between biodiversity and ecosystem function (BEF) during the secondary succession of a tropical forest. Thus, the structural equation models (SEM) tested on functional dominance and functional diversity allowed to explain variations in the above-ground biomass individually. The succession time was the best predictor to explain above- ground biomass variations in all SEM models, followed by soil texture that had significant positive effects on above-ground biomass compared to soil fertility that had negative effects and not significant. Our study contributes to the understanding of the BEF relationship throughout the secondary succession, and may help predict how tropical forests will respond to future scenarios of climate change. For this reason, we have argued that in order to increase the efficiency in the implementation of REDD+ strategies in Amazonian forests, it is necessary to simultaneously understand the relationship of patterns and processes of forest ecosystems with the socio-ecological system, through the analysis of biophysical and anthropogenic predictors, from a local level to a regional scale.
Tese não possui título em português.

This thesis explores how Katuic-speaking indigenous groups in the Central Annamitic Cordillera of Vietnam and Laos understand their environment – hills, streams and forest. Katuic eco-cosmology assumes that the natural landscape is imbued with spirit agents, with whom people must continuously communicate lest misfortune will strike and their livelihoods fail. The thesis posits the hypothesis that these spirit beliefs, and a variety of taboo notions accompanying them, can be interpreted as expressions of a complex socio-environmental adaptation. Today, the indigenous groups in the study region are confronted with a massive development- and modernisation push on two fronts – that of the global development industry on the one hand, and the implementation of national development policies and programs as part of the high-modernist state project in communist Vietnam and Laos, on the other. A second objective of the thesis, then, is to examine the effects of this multi-layered and multi-scaled confrontation on indigenous cosmology, livelihood and landscape. It is argued, this confrontation at the development frontier can be conceived of as an interface between different ontologies or reality posits – one animist, articulated in a relational stance towards the landscape; the other, a naturalist or rationalist ontology, expressed as an objectivist stance towards nature and embodied in the high-modernist development schemes and programs unfolding in the region with the aim of re-engineering its indigenous societies and exploiting its natural resources.      Large parts of the Central Annamites were severely impacted by the Vietnam War; uncounted numbers of minority people were killed, or had their villages destroyed or relocated while defoliants, bombs, and forest fires ravaged the landscape. In the decades that followed the war, the entire social and natural landscape has been reshaped by national development policies and the modernist visions that underpin them. The thesis attempts to understand this physical and cultural transformation of the landscape, focusing particularly on the gradual breakdown of the complex indigenous socio-religious institutions that appear to have played an important functional role in maintaining the pre-war structure of the landscape. The thesis is based primarily on fieldwork carried out between 2004 and 2009 in the provinces of Quảng Nam and Thừa Thiên–Huế in Vietnam and Sekong in Laos.

Shifting cultivation is considered to be a key cause of deforestation in the tropics as agriculturalists transform the rain forest into cropland and later allow for its regeneration through fallowing. Forest fallows strongly influence the ecological and economic potential of shifting cultivation, yet, secondary forest management among shifting cultivators remains poorly understood. This study focuses on secondary forest management among peasant households in a land-abundant ejido, near the Calakmul Biosphere Reserve of Mexico. Data were gathered through in-depth household interviews and field visits with 44 households, accounting for more than 450 fields. Striking differences were found in fallowing practices in Nuevo Becal. The holding of secondary forest is related to access to male labour, wealth in land-assets, household age, and the holding of pasture. Fallow length at the plot level is associated with household age, land holding size and the manner in which land is acquired. Fallow periods tend to be longer for cycles begun from primary forest and appear to have become longer over time. This study demonstrates the importance of the microdynamics that influence differential land use decisions among households under apparently similar environmental and macroeconomic conditions.

O sistema agrícola itinerante (SAI), uma das formas mais antigas de agricultura, continua sendo praticado pelas comunidades quilombolas do Vale do Ribeira-SP. Entretanto, as atuais restrições da legislação ambiental brasileira, a maior integração ao mercado, e a influência de instituições e políticas públicas, estão entre os principais motivos da diminuição desta prática. A produção para o consumo doméstico do SAI está sendo substituída pela agricultura permanente e comercial de pupunheira para palmito, apoiada por incentivos governamentais como créditos financeiros e assistência técnica especializada. Este projeto teve como objetivo avaliar a produtividade entre os diferentes sistemas de cultivo e entre áreas submetidas a diferentes tempos de pousio, discutindo os motivos e os impactos desta transição, sua sustentabilidade, assim como os impactos econômicos para as comunidades. Utilizamos a unidade doméstica como unidade de análise para a organização social do trabalho; para cada atividade reconstituímos o itinerário técnico através de entrevistas semiestruturadas e visitas a campo; e para estimar a capacidade de remuneração dos diferentes sistemas agrícolas utilizamos o cálculo do valor agregado líquido. Durante onze meses acompanhamos a implantação das roças para consumo doméstico e o manejo do cultivo permanente de pupunheira para palmito. Os resultados mostram que há uma tendência de que em capoeiras mais jovens (entre 10-15 anos de pousio) o tempo destinado ao trabalho seja menor quando comparado com o tempo destinado ao trabalho em capoeiras avançadas (com mais de 25 anos de pousio). Entretanto, devido ao tamanho reduzido da amostra não foi possível testar sua significância. Já para a avaliação da produtividade entre os diferentes sistemas, a agricultura permanente se mostrou mais eficiente em termos de renda e no uso do trabalho, do que o SAI. Entretanto, ao considerarmos a multifuncionalidade da agricultura, o SAI desempenha um papel não só de produção de alimentos e fibras, mas também é parte de um complexo de relações socioambientais que incluem a manutenção da diversidade cultural, da agrobiodiversidade e da preservação ambiental.
The shifting cultivation system (SCS), one of the oldest forms of agriculture, is still practiced by quilombola communities in the Vale do Ribeira - SP. However, current restrictions of the Brazilian environmental legislation, increased market integration, and the influence of institutions and public policies, are among the main reasons for the decrease in this practice. The production of SCS for domestic consumption is being replaced by permanent and commercial cultivation of peach palm, supported by government incentives such as financial claims and specialized technical assistance. This project aimed to assess the productivity of the different cultivation systems and between areas under different fallow lenghts, discussing the reasons and the impacts of this transition, its sustainability and economic impacts for communities. The household was used as the unit of analysis for social work organization; for each activity we recomposed the technical itinerary through semi-structured interviews and field visits; to estimate the remuneration capacity of the different farming systems used the added net value. During eleven months we monitored the implementation of the cultivated fields for domestic consumption and the management of permanent cultivation of peach palm. Our results showa tendency for lower worktime in fields with younger fallows (10-15 years) when compared to older ones (25 years).However, due to the small sample size after the abandonment of the fields by some farmers it was not possible to test its significance. As for the evaluation of productivity between the two different systems, permanent agriculture was more efficient in terms of income and the use of labor than SCS. However, when the multifunctionality of agriculture is considered, SCS plays a role not only in food and fiber production, but is also part of a complex socio-environmental relations that include the maintenance of cultural diversity, agrobiodiversity and environmental preservation.

"Slash-and-burn" agriculture, or shifting cultivation, is perceived by many to be the leading cause of land degradation in tropical forests. Performed mainly by resource-poor farmers, shifting cultivation is the most widespread form of agriculture in the tropics. Concern over its environmental impacts has led to calls throughout the twentieth century for alternatives by policy-makers and development planners. This study employs a constructivist framework, post-colonial perspectives, and rhetorical methods to understand the images which support such assertions regarding shifting cultivation, primarily in policy-oriented depictions. Elements of Kenneth Burke's "dramatistic" method are used, including the analysis of hierarchies which structure discourse, and pentadic analysis.
Ph. D.

Researchers recognize the need to better understand the factors influencing indigenous land use in order to design sustainable tropical forest management programs. A key relationship that has been long overlooked in peasant societies is the one between communal labor access through social networks and land acquisition/accumulation. This study examines land distribution and labor patterns in traditional agriculture of a lowland and a upland community on the Maranon River near Iquitos, Peru. Data were gathered through household interviews (n=76) and field visits (n=396) between June and November 2001. Results reveal marked variations in access to land and communal labor between and within communities. Household age, initial land wealth and initial inputs of labor are crucial in explaining land and labor inequalities within villages. This research contributes to a better understanding of the factors that give rise to local heterogeneity in wealth holdings and livelihood strategies, necessary tools to promote conservation throughout the region and beyond.

Wild plant resources are harvested and managed by people in a variety of land-uses but few studies examine the interactions of landscape dynamics and the use and availability of wild plant resources. I address this question using a case study of common property lands with a history of community forestry and traditional shifting cultivation. Specifically I ask: What is the perceived importance of plant resources obtained in agricultural and forest environments? Have forest and agricultural land-use/land covers changed? How do landscape changes, and in particular shorter fallow times, influence the availability and use of plant resources?
The perceived importance of wild plant resources was studied using free-listing and ranking exercises with focus groups of men and women. Remote sensing and interviews served to analyse landscape dynamics (1976-2000) and to identify local forest conservation regulations. The impact of shorter fallow times on the availability of forage and firewood in agricultural fields was assessed by sampling 26 fields derived from short to long fallows, while a household survey served to characterize patterns of firewood collection.
Men attributed highest importance to commercial forest products, while resources most valued by women were domestic resources obtained in a variety of environments. High rates of forest retention were observed; conservation was focused on forests with high densities of commercial products. The agricultural zones shifted from a mosaic of diverse successional stages to a homogeneous landscape dominated by younger fallows and shorter fallow periods; these changes led to reductions in the availability of firewood and some forage species. Firewood collection was related to accessibility; areas with the least amount of firewood available (short-fallow cycles and low forest cover) experienced the highest collection pressure.
The findings demonstrate that indigenous territories can be very dynamic, even when rates of forest conservation are high, and that changes in land-use and landscape structure have important implications for the availability and use of wild plant resources. A conceptual model linking landscape dynamics to wild plant use is proposed and the significance of the results for community-based conservation initiatives is discussed.

Orientadora: Profª. Drª. Helena França
Coorientador. Prof. Dr. Leandrro Reverberi Tambosi
Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Ciência e Tecnologia Ambiental, Santo André, 2018.
Esse trabalho objetivou mapear e quantificar a agricultura itinerante praticada pelas populações tradicionais caiçaras na região do atual Parque Estadual do Prelado (PEP), uma das unidades de conservação do Mosaico de Unidades de Conservação Juréia-Itatins (MUCJI), situado na região litorânea sul do estado de São Paulo, entre 1962 e 2011. Fotografias aéreas de 1962, 1972, 1981, 2000 e 2011 foram digitalizadas, ortorretificadas e interpretadas em Sistema de Informações Geográficas (SIG). As roças foram mapeadas e quantificadas em relação ao número e área. Constatou-se que 12,4% da área do PEP foi manejada pela agricultura, e que os 87,6% restantes não foram usados para essa atividade nos últimos 60 anos. As áreas cultivadas estavam distribuídas pelas bordas do Parque, sobre a Floresta Ombrófila Densa de Terras Baixas, próximas às estradas e rios, mesmo que distantes das unidades domésticas. No ano de 2011, 95% da área que havia sido utilizada previamente para agricultura estava regenerada como floresta, e apenas 0,05% da área total do PEP permanecia como roça. A análise indicou que 40% das áreas manejadas não apresentaram a classe de roças em nenhum mapeamento dos anos estudados, sugerindo que essas áreas só foram cultivadas nas décadas anteriores a 1960; nos 60% restantes, ou houve cultivo por duas ou mais décadas, ou o pousio foi inferior a 10 anos. A agricultura itinerante, que vinha diminuindo desde a década de 1960, apresentou ruptura praticamente definitiva após a criação da unidade de conservação em 1986.
The purpose of this work is to map and quantify the shifting cultivation practiced by traditional communities caiçaras in the region of Prelado State Park (PEP), one of the units of the Juréia-Itatins Conservation Units Mosaic (JICUM) located in the southern coastal region of the state of São Paulo between 1962 and 2011. Aerial photographs from 1962, 1972, 1981, 2000 and 2011 were scanned, orthorectified and interpreted in a Geographic Information System (GIS). The plots were mapped and quantified in relation to the number and area. It was found that 12.4% of the PEP area was managed by traditional practices of shifting cultivation, and that the remaining 87.6% was not used for this activity in the last 60 years. The cultivated areas were distributed along the edges of the Park, over the Dense Ombrophilous Forest of the Coastal Plain, close to the roads and rivers, even if far from the houses. In 2011, 95% of the area that had previously been used for shifting cultivation was regenerated as forest, and only 0.05% of the total area of the PEP remained as a traditional agriculture. The analysis has indicated that 40% of the areas which were managed by traditional agriculture was not cultivated prior to 1960; in the remaining 60%, there was no agricultural management for two or more decades, or perhaps there was fallow for less than 10 years. Shifting cultivation, which was decreasing since the 1960s, suffered a definitive rupture after the creation of the protected area Jureia-Itatins Ecological Station in 1986 (later converted in JICUM).

O presente trabalho teve por objetivo compreender a dinâmica do manejo da agrobiodiversidade nos roçados de mandioca em comunidades ribeirinhas de várzea e terra firme das Reservas de Desenvolvimento Sustentável Amanã e Mamirauá, na Amazônia, e suas relações com as formas de organização da produção, do espaço e do trabalho adotadas pelos produtores. Para tal foi trabalhado um conjunto de metodologias baseados na teoria de sistemas agrários, análise de agroecossistemas, etnoecologia e análise genética utilizando microssatélites. Os resultados indicaram que: 1) Nas duas reservas existem três identidades produtivas, forjadas a partir da principal fonte de renda: agricultores, pescadores e agricultores-pescadores (desenvolvem as duas atividades com fins de comercialização); 2) Os ribeirinhos classificam diversos ambientes como aptos para a agricultura, e a partir deles diversos sistemas de cultivo, que variam em função do ecossistema (várzea ou terra-firme); 3) Existem duas racionalidades produtivas na agricultura (comercialização e auto-consumo), que moldam as racionalidades de manejo da agrobiodiversidade; 4) A diversidade específica e varietal nos roçados diminui à medida que se aumenta o grau de especialização produtiva, tanto da pesca, quanto da agricultura. Contudo, isso não se verifica do ponto de vista genético, uma vez que os genes estão bem distribuídos nas variedades e populações, independente da lógica produtiva; 5) Os roçados de mandioca da RDS Amanã e RDS Mamirauá são extremamente diversos geneticamente, apresentando altos valores de riqueza alélica, polimorfismo e heterozigosidade; 6) A diversidade genética está estruturada basicamente dentro de cada roçado, o que indica alto fluxo gênico entre as variedades de cada roçado e entre as variedades dos diferentes roçados, proporcionada principalmente pela troca de variedades entre agricultores, diminuindo a diferença entre roçados e aumentando a freqüência de diferentes alelos em cada roçado; 7) Os pescadores e as comunidades de várzea têm papel fundamental na dinâmica da agrobiodiversidade, pois abrigam grande número de espécies e variedades de mandioca nos roçados; 8) Portanto, em todas as comunidades a agricultura tem papel fundamental, o que denota que as estratégias de assessoria devem prever a dimensão de sistemas de produção em suas intervenções.
This study had the objective of understanding the agrobiodiversity management dynamics in roçados (swidden fields of cassava) in riverine communities of the Amanã and Mamirauá Sustainable Reserves in the Amazon and its relations with production, space and work management adopted by the families. The methodology adopted was based on the agrarian systems theory, agroecosystems analysis, ethnoecology and microsatellites genetic analysis. The results indicated that: 1) In the two reserves there are three productive identities, forged from the main source of economic income: agriculturists, fishing and agriculturist-fishing (they develop the two activities with commercialization aims); 2) The informers classify diverse environments as apt for agriculture, and from them diverse crop systems, that vary in function of the ecosystem (land-firm or floodplain); 3) There are two productive rationalities in agriculture (commercialization and self-consumption), which adapts to the rationalities of agrobiodiversity management; 4) The specific and varietal diversity in the roçados decreases as the level of productive specialization increases, both the fishing and agriculture. However, this is not verified in the genetic point of view, where the genes are well distributed in the varieties and populations, independent of the productive logic; 5) The roçados at the Amanã and Mamirauá SDR are extremely diverse, presenting high values of allelic diversity, polymorphism and heterozigosity; 6) The genetic diversity is structured basically within each roçado, which indicates high gene flow among the varieties of each roçado and among the varieties of the different roçados, promoted mainly by the exchange of varieties between agriculturists, diminishing the difference between roçados and increasing the frequency of different alleles in each roçado; 7) The floodplain fishing and communities have an important role in the agrobiodiversity dynamics, as they shelter a great number of species and cassava varieties in their roçados; 8) Therefore, in all the communities agriculture has an important role, which denotes that the extension strategies must foresee the production systems approach in their interventions.

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Based on the premise that the replacement of native forests by agroecosystems impacts the soil, were studied different forms of soil use compared to a fragment preserved forest. The study was conducted in an Entisol Quartzipsammentunder the family agriculture use for 22 years, managed under: SAF – Agroforestry system, PA - Pasture, RT - Slash and burn field and MA - Preserved forest. The management impacts on the soil were estimated by the changes in the accumulation and quality of the soil mulch and by the changes on the physical and chemical indicators of soil. The collect of soil mulch, the soil resistance to penetration, until 40 cm depth, and the collect of deformed and undeformed soil samples, for of physical and chemical analyzes, collected in seven repetitions for each system, layers 0-5, 5-10, 10-20 and 20-40 cm depths for two consecutive years and in two sampling periods (July 2010/2011 and January 2011/2012). The variables analyzed were: accumulation of soil mulch and its nutrient content, carbon stock on soil mulch and the soil, plant residue quality index, soil organic matter, soil acidity, exchangeable bases, cation exchange capacity, bases and aluminum saturation, strength penetration, bulk density, porosity and soil aggregation. The results showed that soil use with agroforestry system, even after 22 years of use, little differentiates itself from the preserved area. The conversion of forest in agroecosystems enhances the soil chemical properties and significantly reduces the stocked carbon in the soil mulch compartment, as noted in the “slash and burn” field. The soil use with pasture for successive years increases bulk density, strength penetration, microporosity and reduces soil macroporosity. In this study, clear distinctions between the forms of use and soil management were observed in stocks of litter on the soil surface and strength penetration.
Partindo da premissa que a substituição das florestas nativas por agroecossistemas impacta os solos, foram estudadas diferentes formas de uso do solo em comparação a um fragmento de floresta preservada. O estudo foi realizado em um Neossolo Quartzarênico sob uso da agricultura familiar por 22 anos, manejado sob: SAF – Sistema agroflorestal, PA – Pasto, RT – Roça de toco e MA – Mata preservada. Os impactos do manejo sobre o solo foram estimados por meio das mudanças ocorridas no acúmulo e qualidade da serrapilheira, indicadores físicos e químicos do solo. Coletas de serrapilheira, penetrometrias até 40 cm e amostras deformadas e indeformadas de solo, para fins de análises físicas e químicas, foram feitas em sete repetições por sistema de uso, nas camadas 0-5, 5-10, 10-20 e 20-40 cm, por dois anos consecutivos e em dois períodos de amostragem (Julho 2010/2011 e Janeiro 2011/2012). As variáveis analisadas foram: acúmulo de serrapilheira, teores de nutrientes na serrapilheira, estoque de carbono nos compartimentos serrapilheira e solo, índice de qualidade de resíduo vegetal, matéria orgânica do solo, acidez do solo, bases trocáveis, capacidade de troca de cátions, saturação por bases e alumínio, resistência do solo à penetração, densidade do solo, porosidade e agregação do solo. Os resultados apontaram que o uso do solo com sistema agroflorestal, mesmo após 22 anos de uso, pouco se diferencia da área preservada. A conversão da floresta em agroecossistemas potencializa os atributos químicos do solo e reduz, sensivelmente, o carbono estocado no compartimento serrapilheira, conforme observado na Roça de toco. O uso do solo com Pasto, por sucessivos anos, incrementa a densidade do solo, resistência à penetração do solo, microporosidade e reduz a macroporosidade do solo. Neste estudo, clara distinção entre as formas de uso e manejo do solo foram observadas nos estoques de serrapilheira sobre a superfície do solo e resistência à penetração.

This study deals with the Kinh (or Viet) majority people who have migrated from the lowland Red River Delta to the mountainous areas of northern Viet Nam, and their adjustment to a new social and physical environment. Its aim is to analyse the social and cultural consequences for these migrants when settling in communities populated with people who belong to the national ethnic minorities (the Tày, the Giay and the Ngan peoples). Focus is on impacts in new interactive situations. The case is a special one in that it focuses on majority people's adaptation to minorities, and to a lesser extent vice versa. The Kinhs' view of how a "civilised" landscape ought to look like and how to utilise the natural resources therein demonstrated to be a central theme when discussing restructuring of the migrants' livelihood. This fact indicates the cultural dimension in the exploitation of the natural landscape and the reconstruction of the subsistence system. In the process of adaptation to a new social environment (as well as to a new physical one), social interactions between the Kinh and the ethnic minorities have proven to be important steps towards integration. One factor that turned out to be decisive in the integration process is the harmonising of life cycle ceremonies (especially weddings and funerals) between the Kinh and the minorities. New knowledge is accumulated locally, based on pooled experience. The study concerns how new knowledge on natural resources management is formed through a mixture of the migrants' knowledge from the Red River Delta and the minorities' knowledge of the local area. With a background in the delta area the Kinh brought the old knowledge of advanced wet rice production with them when migrating to the highlands. The facts show that the influence on the subsistence system has not been a one-way flow. That is, not only has the Kinh changed the minorities' agriculture system, but also the minorities' systems have had an impact on the Kinhs' system so that it now is more adapted to the conditions in the highlands.

Unidades de conservação possuem o objetivo de preservar a natureza, evitando o desmatamento e promovendo a sustentabilidade do meio ambiente. Contudo, para que estas atendam aos propósitos para os quais foram criadas, sem acarretar prejuízos sociais ou conflitos com as populações locais, estudos aplicados interdisciplinares são essenciais, agregando conhecimento útil à gestão e ao planejamento das unidades de conservação. Sob a ótica da ciência da complexidade, o objetivo principal deste trabalho foi desenvolver modelos que auxiliassem na compreensão das mudanças no uso e cobertura da terra, realizassem simulações de cenários futuros, e permitissem observar os efeitos da implantação de políticas de preservação sobre a paisagem. Construímos modelos dinâmicos baseados em cadeias de Markov e autômatos celulares, aliados a técnicas de geoprocessamento. Os modelos foram aplicados a um estudo de caso, o Parque estadual do Itinguçu, ao longo de uma série temporal de materiais aerofotográficos de quase 50 anos (1962-2010). Os resultados dos modelos mostraram que a implantação da unidade de conservação foi essencial para barrar o desmatamento, mas que as práticas tradicionais de agricultura itinerante não estavam diretamente relacionadas à conversão da área de floresta, indicando que a incompatibilidade entre preservação e presença humana, muitas vezes usada como justificativa para a implantação de unidades de proteção integral, deve ser reavaliada sob outra perspectiva. Os resultados também apontaram para um desempenho satisfatório do modelo de Markov em projetar tendências, apesar de possuir certa aleatoriedade na alocação dos elementos no espaço. O incremento do autômato celular diminuiu tal aleatoriedade, mas não foi tão eficiente em reproduzir as tendências observadas nas matrizes de transição quanto o modelo de Markov. Concluímos que a metodologia aplicada no presente trabalho foi útil para compreendermos as mudanças na paisagem da área de estudo, e que a escolha do modelo (Markov ou Markov com autômato celular) deve ser feita com base em uma análise criteriosa caso a caso, em conformidade com as prioridades do estudo a ser realizado. Espera-se que esta pesquisa possa fomentar a discussão sobre o uso desta metodologia como uma ferramenta para planejamento e análise de políticas de conservação da natureza e gestão do território
Conservation units have the purpose to preserve the nature, avoiding the deforestation and promoting the environment sustainability. However, for these to be effective in that purpose, without causing social injuries or conflicts with the local population, interdisciplinary applied studies are essential and must be made by different areas of science, adding useful knowledge to the management of protected areas. Under the vision of the Complexity Science, the main goal of this research was to develop models that help in understanding the land use and cover changes, perform simulations of future scenarios, and allow observing the effects of the implementation of conservation policies on the landscape. We built Markov and cellular automata models, allied to the geoprocessing techniques. The models were applied to a case study, the Parque Estadual do Itinguçu, over a time series of aero photographic materials of almost 50 years (1962-2010). The results of the models showed that the implementation of the conservation unit was essential to stop the deforestation, but the traditional practices of shifting cultivation were not directly related to the conversion of forest area, indicating that the incompatibility between conservation and human presence, often used as justification for the implementation of some strict protection units, should be reviewed from a different perspective. The results also pointed to a satisfactory performance of the Markov model to project trends, despite having certain randomness in the allocation of elements in space. Add cellular automata to model decreased this randomness, but was not so effective in reproducing the observed trends in transition matrices than the Markov model. We concluded that the methodology applied in this study was useful for understanding the changes in the landscape of the study area, and that the choice of model (Markov or Markov with cellular automata) should be based on a careful analysis in accordance with the priorities of the study to be applied. We hope that this research can encourage the discussion of this methodology as a tool for analysis of conservation policies of nature and land management

Esta tese é um estudo de Ecologia Humana realizado no contexto de duas comunidades remanescentes de quilombo da região do Vale do Ribeira (Médio Ribeira, SP). Portanto, avalia as interações socioambientais entre as comunidades humanas e as biológicas que constituem o bioma Mata Atlântica na região. Especificamente, esta interação é investigada a partir da dinâmica da fertilidade dos solos, a qual é um subsídio fundamental para o estabelecimento e a manutenção da atividade agrícola quilombola sob os processos ecológicos desse ecossistema florestal. O sistema agrícola quilombola baseia-se nos processos ecológicos da floresta e corresponde ao amplamente conhecido Sistema Agrícola Itinerante (SAI). Desta forma, o manejo do SAI quilombola transfere parte dos nutrientes do complexo solo/vegetação para a produção de cultivares, destinada à subsistência destas populações: o arroz, o milho, o feijão e a mandioca. A principal questão teórica que envolve o SAI é como é possível manter o equilíbrio entre o balanço dos nutrientes mantidos no complexo solo/vegetação da floresta, em face da retirada de parte deles do sistema devido à perturbação antropogênica. Esta tese avaliou os impactos do SAI quilombola sobre o solo da Mata Atlântica no Médio Vale do Ribeira (SP). Dentro deste enfoque ecológico, avaliou também se o SAI quilombola mantém o equilíbrio da dinâmica de nutrientes do complexo solo/vegetação da floresta, ou seja, se o sistema é sustentável. As duas comunidades estudadas se originaram a partir de contingentes de escravos forros, libertos ou fugidos na região há pelo menos dois séculos, e adotaram o SAI quilombola como principal atividade de subsistência na Mata Atlântica. Esta prática histórica definiu em grande parte a composição e a configuração da paisagem que se observa atualmente na região. A dinâmica da fertilidade do solo sob o SAI quilombola foi avaliada em áreas com vegetação secundária passível de ser convertida, de acordo com a lei (10 anos de pousio) e áreas com 25-30 anos de pousio, consideradas mais adequadas pelo etnoconhecimento ecológico quilombola. Portanto, o objetivo central desta tese é avaliar os impactos do SAI quilombola sobre o solo numa área de mata atlântica no Médio Vale do Ribeira (SP). Os objetivos específicos são: (1) Analisar a qualidade dos solos nas diferentes fases do SAI - Conversão, Cultivo e Pousio (este último, em período inicial e em biossequência em florestas secundárias em diferentes estádios de regeneração submetidas ao uso agrícola); (2) analisar o papel do fogo sobre a qualidade do solo (nutrientes, SOC, propriedades físicas e biológicas); (3) verificar se o solo apresenta-se num processo conservativo ou de degradação nas áreas submetidas ao cultivo itinerante. Dois métodos foram empregados para esta investigação. O método diacrônico avaliou a dinâmica da fertilidade do solo nas etapas de conversão e cultivo do SAI quilombola, o efeito do fogo sobre a temperatura dos solos nas roças experimentais e a estimativa da biomassa destas áreas a partir de uma equação alométrica desenvolvida com o uso do método destrutivo de pesagem da biomassa epígea. O método sincrônico avaliou a dinâmica da fertilidade do solo sob o SAI em áreas com diferentes classes de idade de pousio e comparou-as com os solos de floresta madura. Os resultados obtidos apresentaram interesses ecológicos, socioambientais e políticos. Com as duas revisões apresentadas (descritiva e sistemática) conclui-se que o SAI tem potencial como um sistema agrícola sustentável ecologicamente. Os resultados do estudo diacrônico mostraram que não há diferença significativa entre as roças de 10-15 anos e 20-25 anos na condição de fertilidade do solo antes do início do ciclo, assim como para a eficiência do fogo utilizado e a quantidade de nutrientes que este disponibiliza para solo através das cinzas. A temperatura sob o fogo não variou acima de 10°C nos solos, condição que não gera impactos negativos às suas propriedades. O estudo sincrônico apresentou uma definição de pousio, a qual definiu o papel do mesmo como o de garantir a manutenção dos nutrientes do complexo solo/vegetação das florestas tropicais submetidas ao SAI. Encontrou que o protagonista na dinâmica dos nutrientes no SAI quilombola é a decomposição do material botânico não queimado durante, principalmente, o período do pousio, e não o fogo. Os dois métodos permitiram a descrição de um modelo de Slash/Mulch de SAI denominado aqui de Mulch/Slash/Burn, o qual agrega o Mulch, muito defendido como uma alternativa para o fogo, mas também o fogo, considerado fundamental para os agricultores itinerantes. Permitiram concluir que o etnoconhecimento dos quilombolas estava correto em reivindicar que o SAI seja realizado a partir de roças em estádios tardios e não iniciais como previsto em lei. Conclui-se que para garantir a sustentabilidade do SAI quilombola do ponto de vista ecológico deve-se manter o modelo tradicional de manejo do complexo solo/vegetação praticado por estas populações, baseado no etnoconhecimento transmitido pelos antepassados. Na escala da paisagem recomenda-se também manter o modelo tradicional de manejo, pois as atuais políticas de desenvolvimento, sociais e de conservação têm gerado a substituição gradual dos SAIs para agricultura perene comercial como verificou-se em outras regiões do mundo. Os gestores públicos devem aproximar-se destas populações tradicionais e apoiá-las de acordo com os seus conhecimentos tradicionais, além de apresentar soluções embasadas em estudos técnico-científicos buscando melhorar as condições socioambientais dos envolvidos. Portanto, o modelo tradicional do SAI quilombola apresenta sustentabilidade socioambiental, e assim foi até meados da década de 50 do século XX. Desde então vem sofrendo transformações de diversas ordens, as quais, além de comprometer sua sustentabilidade, podem levar à completa extinção do sistema. Neste sentido, o desenvolvimento e a melhoria da qualidade de vida das populações quilombolas do Vale do Ribeira deveriam ser situados em políticas de desenvolvimento territorial rural mais amplas, em consonância com o debate internacional sobre descentralização da governança florestal. Estas políticas, sobretudo, deveriam trabalhar na escala da paisagem, buscando atingir metas de conservação e desenvolvimento numa matriz paisagística diversificada e multi-uso
This thesis is a study of Human Ecology within the context of two remaining quilombolas communities in the Ribeira Valley region (SP). Assessing therefore the environmental interactions between the human and biological communities that make up the Atlantic Forest biome in the region. This interaction was specifically investigated from the dynamics of soil fertility, which is a key benefit for the establishment and maintenance of quilombola agricultural activity under the ecological processes of this forest ecosystem. The quilombola agricultural system is based on the ecological processes of the forest which correspond to the widely known Shifting Cultivation System (SCS). Thus, the farming at the quilombola SCS transfers a portion of the nutrients of the complex soil/vegetation to produce cultivars used for the livelihood of these populations: rice, corn, beans and manioc. The main theoretical question that involves the SCS is how it can maintain the equilibrium between the balance of the nutrients maintained in the complex soil/vegetation of the forest when confronted with their removal from the system due to the anthropogenic disturbance. This thesis has assessed the impact of the quilombola SCS on the soil of the Atlantic Forest in the Middle Ribeira Valley (SP). Within this ecological approach, it also evaluated if the quilombola SCS maintains the equilibrium of the nutrients\' dynamic in the complex soil/vegetation, that is, if the system is sustainable. The two studied communities originate from the freed, rescued or escaped contingent of slaves in the region around two centuries ago, and who adopted the quilombola SCS as the main subsistence activity in the Atlantic Forest. This historical practice has largely defined the composition and the configuration of the landscape that is currently observed in the region. The dynamics of fertility of the soil under the quilombola SCS was evaluated in areas with secondary vegetation that could be converted, in accordance with the law (10 years of fallow) and areas with 25-30 years of fallow, which is considered as more appropriate by the quilombola ecological ethnoknowledge. Therefore, the main objective of this thesis is assessing the impact of the quilombola SCS on the soil in a rainforest area in the Middle Ribeira Valley (SP). The specific objectives are: (1) analyzing the quality of the soil at the various stages of the SCS - Conversion, cultivation and fallow (the latter in the initial period and the biosequential sampling in secondary forests in different regeneration stages that were subjected to agricultural use); (2) analyzing the role of fire on the quality of the soil (nutrients, SOC, physical and biological properties); (3) verifying if the soil is in a conservative or degradation process in areas that were subjected to shifting cultivation. Two methods were used for this investigation. The diachronic method assessed the dynamics of soil fertility in the conversion and cultivation phases of the quilombola SCS, the effect of fire on the temperature of the soil in the experimental plots, and estimated the biomass of these areas using an allometric equation that was developed using a destructive method of weighing the epigeal biomass. The synchronous method evaluated the dynamics of soil fertility under the system in areas with different fallow age groups and compared them with those of mature forest soils. The results showed ecological, social, environmental and political interests. The two presented reviews (descriptive and systematic) led to the conclusion that the SCS has potential as an environmentally sustainable agricultural system. The results of the diachronic study showed no significant differences in the condition of the soil fertility between the areas with 10-15 years and 20-25 years before the beginning of the cycle, as well as in the efficiency of the fire used and the quantity of nutrients that is provided to the soil through the ashes. The temperature under the fire did not vary above 10 ° C in the soil, a condition that did not generate a negative impact on their properties. The synchronic study presented a definition of fallow, defining its role as the one to ensure the maintenance of the nutrients of the complex soil /vegetation of tropical forests subjected to the SCS. It was found that the protagonist in the dynamics of the nutrients of the quilombola SCS is the decomposition of botanic material, especially during the fallow period and not burned by the fire. Both methods enabled the description of a model of Slash/Mulch of SCS herein called Mulch/Slash/Burn, which adds Mulch, which has been quite advocated as an alternative to fire, but also the fire, considered crucial by shifting cultivators. They showed that the ethnoknowledge of the quilombolas was correct when claiming that the SCS should be conducted in farms at late successional vegetation stages and not initial, ones as provided by law. In conclusion, to ensure the sustainability of the quilombola SCS from an ecological standpoint, one must maintain the traditional farming model of the complex soil/vegetation that is practiced by these populations, based on the ethnoknowledge transmitted by their ancestors. On the landscape scope, keeping the traditional farming model is also recommended, since the current development, social and preservation policies have led to the gradual replacement of the SCS by commercial perennial agriculture systems, as verified in other regions of the world. Public managers should approach these traditional communities and support them according to their traditional knowledge, in addition to presenting them with solutions based in technical and scientific studies seeking to improve social and environmental conditions for those involved. Therefore, the traditional model of the quilombola SCS presents environmental sustainability, as was the case until the mid-50s of XX century. Since then it has undergone transformations of various orders, which, in addition to compromising their sustainability, can lead to the complete extinction of the system. In this sense, the development and improvement of the quality of life of the quilombola populations of the Ribeira Valley should be based in broader rural territorial development policies aligned with the international debate on decentralization of forest governance. These policies, above all, should work at the landscape scope, seeking to achieve conservation and development goals in a diversified and multi-use landscape matrix

L'agriculture itinérante sur brulis (ai) est un mode de culture pratique sans intrant. Après deux ou trois cycles de cultures, la dégradation de la fertilité des sols contraint les agriculteurs à déplacer leurs cultures et le terrain est laisse en jachère. La jachère permet de reconstituer une biomasse, qui libèrera lors de la période de production suivante, après brulis, des éléments minéraux nécessaires à la croissance et au développement des cultures. Cette étude consistait, à fournir des éléments d'appui à la décision, dans le but d'une fixation à terme de ces systèmes traditionnels. Elle a nécessité que l'on présente une analyse de la gestion des systèmes d'q. I. , composante importante de la reproductibilité de la fertilité, et condition de la fixation. Dans un premier temps, la gestion spatiale de ces systèmes et leurs capacités à faire face aux contraintes agro-écologiques et socio-économiques du milieu, pour se reproduire, ont été étudiées. Cette étude a été effectuée à l'échelle du système agraire et plus précisément a l'échelle des systèmes de production qui correspondent au niveau des choix et décisions des agriculteurs. Dans un deuxième temps, l'évolution des composantes de la fertilité, susceptible d'influencer le rendement de manioc, a été analysée - le manioc constituant la principale culture de l'ouest Guyane -. Trois niveaux ont été considères : le système de culture qui permet de comprendre les modes de conduite et d'association des cultures, mais surtout la parcelle cultivée et la placette d'expérimentation, lieu de mesures et de suivi. Dans la première étape de ce travail, une capacité d'équilibration des abattis est établie à partir du modelé de Piaget. Cette typologie permet d'identifier 5 types fonctionnels d'abattis dans la région et 2 modes d'évolution. Dans la deuxième étape, lors d'un premier cycle d'abattis, après foret secondaire, l'évolution des stocks de carbone, d'azote et des bases échangeables montre qu'il n'y a pas de dégradation en relation avec la matière organique du sol. En revanche, on assiste à une diminution des bases échangeables suite à la mise en culture et en particulier du potassium. La comparaison de cette diminution avec les besoins de la culture, a permis d'identifier le potassium, comme facteur limitant la production
Shifting cultivation on brulis (ai) is a convenient method of cultivation without inputs. After two or three crop cycles, the degradation of soil fertility forces farmers to move their crops and the land is left fallow. Fallowing can be used to reconstitute a biomass, which will release during the next production period, after burning, the mineral elements necessary for the growth and development of crops. The purpose of this study was to provide support for the decision, with a view to eventually establishing these traditional systems. It required an analysis of the management of Qi systems, an important component of reproducibility of fertility, and the condition of fixation. At first, the spatial management of these systems and their capacity to cope with the agro-ecological and socio-economic constraints of the environment, to reproduce, were studied. This study was carried out at the scale of the agrarian system and more precisely at the level of the production systems which correspond to the level of the choices and decisions of the farmers. In a second step, the evolution of the components of fertility, likely to influence the yield of cassava, was analyzed - the cassava constituting the main crop of West Guiana. Three levels were considered: the cropping system that allows to understand the modes of behavior and association of crops, but especially the cultivated plot and the experimental plot, place of measurement and monitoring. In the first stage of this work, a balancing capacity of the giblets is established from the Piaget model. This typology makes it possible to identify 5 functional types of giblets in the region and 2 modes of evolution. In the second stage, during a first cycle of giblets, after secondary forest, the evolution of stocks of carbon, nitrogen and exchangeable bases shows that there is no degradation in relation to the material organic soil. On the other hand, there is a decrease in exchangeable bases following the cultivation and in particular potassium. Comparing this decrease with the needs of the crop, it was possible to identify potassium as a factor limiting production

L’occupation du sol en zone forestière de Yangambi dans la Cuvette centrale congolaise (RDC) change rapidement et la fragmentation forestière liée à l’agriculture itinérante sur brûlis est devenue l’un des processus dominant la dynamique paysagère. La présente étude s’est fixée comme objectif de suivre une approche microclimatique en transects pour déterminer la zone de lisière entre les jachères herbeuses et les forêts denses, et ce, afin de mieux comprendre les réponses des propriétés physico-chimiques du sol aux changements d’occupation du sol et à la fragmentation forestière. Deux zones les plus appréciées par les paysans pour leurs exploitations agricoles ont été choisies en fonction des unités pédologiques existantes :la série Yangambi et la série Yakonde. Des échantillons non perturbés du sol de 0-10, 10-20 cm, 20-30 cm et perturbés de 0-20 cm ont été prélevés dans les différentes occupations de sols après la détermination de la zone de lisière. Notre démarche a consisté à comparer les propriétés de sols identiques au plan de leur pédogenèse, sous jachère herbeuse, sous lisière et sous couvert forestier, de façon à quantifier l’effet de lisière sur les propriétés des sols, pour mieux connaître les conséquences édaphiques de la fragmentation des forêts par l’agriculture itinérante sur brûlis.

Les résultats obtenus ont montré que la zone de lisière entre les jachères et les forêts denses a une largeur de 70 m pour la série Yangambi et 68 m pour la série Yakonde. Les variations microclimatiques de la lisière en terme de température de l’air, sont intermédiaires (moyenne, minima et maxima) entre celles des jachères herbeuses et des forêts denses. La fragmentation des forêts par l’agriculture itinérante sur brûlis modifie profondément les propriétés physico-chimiques de sols dans les couches superficielles. Un des effets de changements d’occupation du sol et de la fragmentation est la présence d’horizons superficiels à texture sableuse au niveau des jachères herbeuses et des lisières forestières. La densité apparente et la conductivité hydraulique ont subit une importante dégradation sous les jachères herbeuses. A l’inverse, la lisière forestière assure une bonne structure conservatrice du sol (faible densité apparente et bonne conductivité hydraulique). Le sol des forêts denses présente des bonnes propriétés physiques et de ce fait, est pris comme référence à partir duquel les effets de dégradation physique du sol peuvent être appréciés.

Le potentiel chimique du sol (pH, phosphore assimilable, le taux de saturation en bases et la CECE) est meilleur au niveau des jachères herbeuses et des lisières forestières par rapport aux forêts denses suite à la pratique du brûlis qui permet de restituer au sol une fraction de la minéralomasse forestière par les cendres. Les teneurs en carbone et azote totaux du sol ont été significativement plus élevées sous les lisières forestières que sous les jachères herbeuses et les forêts denses. Les résultats de l’indice de Kamprath ont montré que, les lisières, en plus de contribuer à l’accroissement de carbone organique du sol, tendent à diminuer la toxicité aluminique de sols étudiés. A l’inverse, l’étude a mis en évidence une toxicité aluminique plus élevée sous la jachère herbeuse de la série Yangambi que sous la lisière. En parallèle, nous avons observé une baisse des teneurs en fer sous toutes les jachères et les lisières forestières.

Les pratiques de jachères cultivées et d’agroforesterie s’avèrent incontournables pour enrichir ces sols en matière organique, limiter l’érosion liée au brûlis afin de freiner le lessivage des nutriments, éviter le compactage du sol et assurer le maintien à long terme d’une bonne structure conservatrice du sol.

In the forest zone of Yangambi, located in the Central Congo Basin (DRC), land use is changing rapidly and forest fragmentation due to slash and burn agriculture has become one of the dominant processes of landscape dynamics. This study's main goal is to apply a microclimatic approach in transects to determine the edge area between the fallow grasslands and dense forests, and, in order to better understand the responses of the soil physico-chemical properties to changes in land use and forest fragmentation. Two most popular areas used by farmers have been selected on the basis of the existing soil units: the Yangambi and Yakonde series. Undisturbed soil samples at depths of 0-10 cm, 10-20 cm, 20-30 cm and the disturbed at 0-20 cm were collected from different the land use types after detecting the edge area. Our approach was to compare the properties of identical soils based on their genesis, under grass fallow, edge and forest cover, so as to quantify the effect of edge on the soil properties, to better understand the edaphic consequences of the forest fragmentation by slash and burn shifting cultivation.

The results showed that the edge area between fallow and dense forests has a width of 70 m for the Yangambi series and 68 m for the Yakonde series. Microclimatic variations of the edge in terms of air temperature are intermediate (average, minimum and maximum) between grass fallows and dense forests. The fragmentation of forests by slash and burn shifting cultivation profoundly modifies the physico-chemical properties of soils in the surface layers. One of the effects of changes in land use and fragmentation was the presence of surface layers with more sandy texture in the fallow grassland and forest edges. Bulk density and hydraulic conductivity undergo an important degradation under grass fallows. In contrast, the forest edge ensures a maintenance of the soil structure (low bulk density and good hydraulic conductivity). Dense forest soil has thus good physical properties and therefore is taken as the reference from which the effects of soil physical degradation can be appreciated.

The chemical potential of the soil (based on pH, available phosphorus, base saturation and CECE) is better in the grass fallows and forest edges compared to dense forests due to the practice of slash and burn which allows restoration by adding nutrients to the soil through the ashes. The carbon and total nitrogen in the soil were significantly higher under forest edges than in fallow grasslands and dense forests. The results of the-Kamprath index shows the edges, in addition to contributing to an increase in soil organic carbon, tend to decrease the aluminium toxicity of studied soils. By contrast, the study revealed a higher aluminium toxicity under fallow grassland on the Yangambi series that under the edge and the forest. In parallel, we observed a decrease in iron contents in all fallow lands and forest edges.

The practices of cultivated fallows and agroforestry are proving unavoidable for enriching these soils in organic material, to reduce erosion related to slash and burn in order to curb the leaching of nutrients, to avoid soil compaction and to maintain a long-term well developed soil structure.

Doctorat en Sciences agronomiques et ingénierie biologique
info:eu-repo/semantics/nonPublished

Thesis (Ph. D.)--York University, 1999. Graduate Programme in Geography.
Typescript. Includes bibliographical references (leaves [388]-410). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ43436.

Increasing human populations, declining crop yields and reductions in per capita arable land area suggest that shifting cultivation as traditionally practiced in much of the humid tropics is no longer a sustainable farming practice. The use of nitrogen-fixing trees such as Leucaena leucocephala (Lam. de Wit) (leucaena) as a fallow species may be an important strategy to maintain or improve crop yields in shifting cultivation where natural resources are rapidly declining. A series of experiments comparing leucaena and non-leucaena fallows was conducted on sites with fallows established between 1977 and 1992 on the Island of Mindoro, Philippines to determine the impacts of leucaena fallows on rice yields, soil nutrient status and the sustainability of production in shifting cultivation in the study area. Rice yields and yield components were measured on 10 shifting cultivation fields. One burning experiment and a series of chronosequence studies in fallows of 1-4 years of age were conducted. Informal interviews with farmers were also conducted to determine perceptions and social impacts of leucaena as a fallow crop. Moisture content-adjusted grain yields (@0.14 g H20/g dry matter) were 3.8 t ha"1 following leucaena fallows and 2.71 ha"1 following non-leucaena fallows for an average yield response of 42%. This difference appears to relate most closely to soil N accumulated during the fallow period and N added through seedling biomass applied as a surface mulch during the cropping period. N-fixation of leucaena and possibly the inhibition of nitrification of ammonium ions as demonstrated by higher NH4 + concentrations in soils under leucaena were associated with (and may explain) these differences. Higher N levels appear to delay crop maturity, as evidenced by higher grain moisture contents in the leucaena treatment. Available phosphorus levels are low, but do not appear to differ between fallow types, although the size of phosphorus pools in the biomass and litter varied with fallow type. Ca and Mg were not limiting in either fallow type, due to the large soil pool of these nutrients. Organic phosphorus inputs to the rice crop are higher in the leucaena fallows when leucaena wood removals from the site are low. The greatest potential threat to sustainability of crop production following leucaena fallows is charcoal making and the potential losses of P from the system. There appears to be little disadvantage to burning leucaena fallow fields prior to planting. The most significant advantages of burning appear to be increased P availability and reduced weeding costs, although no difference in grain yield due to burning was detected. Leucaena can increase sustainability of shifting cultivation through higher N and P contributions that result in grain yield increases. Additional increases in yield are probably attainable with the use of a minimum fallow age of 3-4 years, timely weed control and use of high-yielding, traditional rice varieties.

La degradación del bosque tropical causada por la agricultura indigena tradicional y la explotación forestal comercial fue evaluada, en el sector central de la Reserva Forestal Imataca en la Guayana venezolana.El enfoque conceptual de paisajes permitió combinar dos niveles de análisis, local y paisajes, con el objeto de detectar las relaciones espaciales que forman patrones, gradientes y estructuras, útiles para el seguimiento y control de los usos del bosque tropical y su estado de conservación. La evaluación integró varios métodos orientados a describir y analizar la composición, estructura y distribución de las comunidades arbóreas, tomando en cuenta su condición: no perturbado o perturbado.Se levantó información social relativa a los usos de la tierra considerados, a través de visitas y mediciones en las áreas de producción de las comunidades Kariñas, al igual que en concesiones forestales tomadas como muestra. Un inventario forestal en parcelas muestra, permitió colectar datos sobre algunos parámetros estructurales del bosque, los cuales sirvieron de base para calcular índices tales como diversidad alfa y beta, complejidad estructural y otros. La detección y cartografía de los bosques no perturbados y perturbados segun el uso considerado, se hizo sobre imagenes de satélite Landsat, a las cuales se aplicó técnicas de percepción remota tales como analisis textural, indices de vegetación y cobertura fraccional.Se estimaron áreas de superposición entre territorios tradicionales Kariña y concesiones forestales comerciales, las cuales probablemente serán objeto de nuevos conflictos que pueden ser graves, considerando el proceso de demarcación de territorios indígenas tradicionales en curso, y la explotación minera próxima a comenzar.El interés de estudiar la compleja situación de la Reserva Forestal Imataca se debe a la necesidad de promover un modelo sustentable de manejo y conservación de bosques para la Guayana venezolana.

Fires are the primary method of deforestation and agricultural management in the tropics, but associated emissions such as aerosols, ozone, and carbon monoxide can have negative impacts on ecosystems, climate, and public health. Recent advances in satellite monitoring of fire activity, including using thermal anomalies for active fire detections and burn scar mapping of post-fire effects, have offered an unprecedented level of detail in understanding the magnitude and extent of fire activity. This dissertation aims to quantify the human health impact across populations in tropical regions by determining which areas are the most susceptible to transported fire emissions and how this exposure varies over time. The following chapters can be used to highlight critical conservation regions, not only for conserving ecosystems for biodiversity and climate benefits, but also for protecting public health. To address how fire emissions can affect regional populations, satellite observations of fire activity are combined with models of how tropical fire emissions are transported in the atmosphere. Satellites provide two primary pieces of information for this approach: 1) measurements of the distribution and magnitude of fire activity, and 2) categorization of fire types (such as agricultural burning or deforestation) by overlaying observed fire patterns on land use maps. Atmospheric models perform the crucial step of simulating how emissions evolve and where they are transported after release into the atmosphere. The following dissertation chapters are linked through exploration of fire emissions impacts from continental to local scales, including implementing fire emissions inventories into atmospheric models, quantifying population exposure to fire activity in Equatorial Asia, and projecting fire emissions associated with various future land use scenarios in Sumatra. Model estimates of aerosol concentrations are more influenced than trace gases by using finer temporal resolution fire emissions, due to interactions between emissions and modeled meteorology and transport. This in turn can impact air quality estimates by permitting higher peak concentrations. In addition, model results show that population exposure to fire emissions in Equatorial Asia is highly variable over time depending on the phase of the El Niño cycle; strong El Niño years can have fire contributions to fine particulate matter of up to 200 µg/m³ near fire sources, corresponding to 200 additional days per year over the World Health Organization 50 µg/m³ 24-hour fine particulate matter air quality target. These risks are not confined to people living near fire sources, but expose broad regional populations due to the atmospheric transport of emissions. Health impacts also depend on underlying fuel characteristics, with the future magnitude of Equatorial Asian fire emissions estimated to be strongly dependent on the level of protection given to fuel-rich peatswamp forests (contributing 33-48% of future emissions in the absence of protection). Collectively, these chapters emphasize variability in how tropical fire emissions affect regional population exposures to outdoor air pollution, and the need to consider the dependence of this public health effect on different fuel types and year-to-year variations in climate. The results described in this dissertation quantify direct benefits of conservation for people living near fire areas.