• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 18
  • 3
  • 3
  • 1
  • 1
  • Tagged with
  • 29
  • 29
  • 15
  • 10
  • 7
  • 7
  • 6
  • 6
  • 6
  • 5
  • 5
  • 5
  • 5
  • 5
  • 5
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Women’s fuelwood collection and deforestation : Effects on women’s everyday lives and environments in Kabadio, Casamance and Diagane Barka, Sine-Saloum.

Tiainen, Sofia January 2019 (has links)
Previous research and literature commonly agree to the fact that women, especially rural women, is the most vulnerable group in society. Many of them tend to be found in the poorest sections of society. Women depend on natural resources for their livelihoods and are discriminated concerning labour division and access, control and knowledge about natural resources such as forests. Changes in the climate and natural degradation, especially forest degradation are threatening their livelihoods. Gender relations are structured around managing the environment where women are seen as major users and managers of the forests. The aim and the research questions of this study is to examine how women in Senegal experience that their everyday life and livelihood activities within fuelwood collection have been affected by deforestation. Furthermore, what reason do women see behind deforestation and the changes in their local environments. Semi-structured interviews were conducted with eleven women from two villages in southern Senegal in the region of Casamance and Sine-Saloum. All these women were involved in fuelwood collecting activities. The result of the study was analysed through previous research, feminist political ecology approach and through definitions of livelihood and sustainable development in order to explain women’s experiences and activities within fuelwood collection. The result found that all women experiences changes in their livelihoods because of deforestation. The amount of time spent on fuelwood collecting activities increased while it less time was left to other activities. Women’s income and resources from the forests reduced or disappeared and the main focus turned into cover the needs of the household. Women’s personal everyday lives have been negatively affected by deforestation. Heavy work had negative health effects on the women. Some women have left fuelwood collection for alternative sources of income because it has become too demanding. Furthermore, the results showed that women are worried about their future since they are in mutual need of forests as well as fuelwood to survive.
12

Múltiplas ameaças e um mosaico de manchas de habitat de diferentes qualidades: a persistência de mamíferos de maior porte em uma região de pós-fronteira na Amazônia / Multiple threats and a mosaic of habitat patches of varying quality: the persistence of large mammals across a post-frontier Amazonian region

Moraes, Paula Elias 21 September 2016 (has links)
A expansão das atividades humanas está associada a várias ameaças antrópicas que afetam a biodiversidade tropical, especialmente a perda e fragmentação de habitat, o continuado crescimento populacional humano e a expansão de infraestrutura, como estradas e rodovias. Embora seja esperado que as ameaças antrópicas interajam e criem mosaicos de manchas de habitat de diferentes qualidades, há ainda poucos estudos sobre os efeitos aditivos e interativos de diferentes ameaças sobre a biodiversidade ou sobre a capacidade de espécies nativas de usar remanescentes de diferentes qualidades. De fato, a maioria dos estudos focaram em apenas uma ou poucas ameaças isoladas, na escala do fragmento em vez da escala da paisagem e não consideraram as variações na qualidade dos remanescentes. Mamíferos de maior porte são um bom modelo de estudo porque possuem um conjunto de características que os tornam particularmente vulneráveis a várias ameaças antrópicas. Dada a dificuldade de obter dados sobre estas espécies elusivas em escalas espaciais adequadas, entrevistas com moradores locais vêm sendo cada vez mais usadas para acessar a distribuição de mamíferos de maior porte, e podem fornecer informações confiáveis. Através da estimativa da ocorrência de 15 espécies de mamíferos de maior porte por meio de entrevistas com o chefe de 12 unidades domésticas em cada uma de 20 paisagens em uma região de pós-fronteira de 1 milhão ha na Amazônia, investigamos: (i) que tipo de habitat e em qual escala espacial está associado com a ocorrência das espécies, e (ii) os efeitos, a importância relativa e as interações de quatro ameaças antrópicas - cobertura de habitat, fragmentação de habitat, densidade populacional humana e densidade de estrada - sobre a persistência das espécies. Dados de presença/ausência nos arredores de 227 unidades domésticas foram analisados usando modelos lineares generalizados mistos e seleção de modelos baseada no Critério de Informação de Akaike em duas etapas. A persistência das espécies maiores e ameaçadas não foi necessariamente afetada pela qualidade do habitat, mas elas responderam majoritariamente a cobertura de habitat em escalas maiores. A chance de persistência de todas as espécies - mesmo das duas menores, que não responderam à perda de habitat isoladamente - foi afetada por alguma combinação das quatro ameaças antrópicas. Efeitos aditivos entre as ameaças antrópicas foram mais importantes do que as interações entre elas na determinação da ocorrência de mamíferos de maior porte. Enquanto os efeitos da perda de habitat foram mais fortes do que os efeitos da fragmentação de habitat per se, a densidade de estradas foi tão importante quanto à perda de habitat para a ocorrência das espécies. Por último, não houve um padrão claro em termos do grau de ameaça e do tamanho corpóreo por trás da reposta dos mamíferos de maior porte a ameaças antrópicas combinadas. Nosso estudo sugere que áreas protegidas em terras públicas ou privadas na Amazônia devem ser grandes para assegurar a persistência de mamíferos de maior porte, mas podem incluir mosaicos de florestas primárias e secundárias. Os resultados também ressaltam a necessidade de considerar os impactos acumulados de múltiplas ameaças simultaneamente - em especial, as consequências da expansão da malha viária - em planejamentos e manejos, de maneira a evitar subestimar a chance de extinções. Evitar que paisagens na Amazônia se tornem muito desmatadas e alteradas é fundamental, dado que a persistência até mesmo das espécies mais comuns pode ser prejudicada, afetando um dos serviços ecossistêmicos mais importantes para moradores locais - a carne de caça - e potencialmente erodindo o valor que estes atribuem às florestas / The expansion of human activities is associated to a myriad of anthropogenic threats that affect tropical biodiversity, especially habitat loss and fragmentation, the continued human population growth and the expansion of infrastructure, as roads and highways. Although anthropogenic threats are expected to interact and to create mosaics of patches of varying quality, their additive and interaction effects on biodiversity, as well as the extent native species are able to use remnants of distinct quality, have yet been poorly studied. Indeed most studies focused on only one or few threats in isolation, on the patch rather than the landscape scale and did not considered the varying quality of remnants. Large mammals are a good study model as they have a set of traits that make them particularly vulnerable to several anthropogenic threats. Due to the difficulties in gathering data on these elusive species at adequate spatial scales, interviews with local residents have increasingly being used to access their distribution and can provide reliable information. By estimating the occurrence of 15 large mammal species through interviews with the head of 12 households within each of 20 landscapes across a 1-million ha post-frontier region in Amazonia, we investigated: (i) which habitat type at which spatial scale is associated with species occurrence, and (ii) the effects, relative importance and interactions of four anthropogenic threats - habitat cover, habitat fragmentation, human population density and road density - on species persistence. Presence/absence data across the surroundings of 227 households was analyzed using generalized linear mixed-effects models, and a two-step model selection based on Akaike’s Information Criteria. The persistence of larger and endangered species was not necessarily affected by habitat quality, but they responded to habitat cover mostly at larger spatial scales. The chance of persistence of all species - even the two smallest that were not affected by habitat loss alone - was disrupted by some combination of the four anthropogenic threats. Additive effects between anthropogenic threats were more important than their interaction in determining the occurrence of large mammals. While the effects of habitat loss were stronger than the effects of habitat fragmentation per se, road density was as important as habitat loss to species occurrence. Finally, there was no clear pattern in threat status or body size underlying the response of large mammals to combined anthropogenic threats. Our study suggest that protected areas in public or private lands in Amazonia should be large to secure the persistence of large mammals, but may include mosaics of primary and secondary forest. The findings also highlight the need to take into account the accumulated impacts of multiple threats simultaneously - particularly, the consequences of the expansion of the road network - in planning and management, as a way to avoid underestimating the chance of extinctions. Preventing Amazonian landscapes to become heavily deforested and altered is critical, as the persistence of even common species can be impaired, affecting one of the most important ecosystem services provided to local residents - bushmeat - and potentially eroding the value people attribute to forests
13

Environmental ethics challenges in the case of Congo basin deforestation : a theological ethical perspective

Buwani, Didier Ngangani 06 1900 (has links)
Environmental issues such as climate change, deforestation, loss of biodiversity are of concern worldwide. Several conflicts on environmental resources management are raised between governments, multinational companies and the local population. Particularly in developing countries, natural resources management is one of the crises where most experiment takes place. Lack of natural resources management can cause war and contribute to poverty. As is observed in the indigenous population of the Congo Basin. This research project aims to investigate the causes of deforestation in the Congo Basin and the environmental ethics challenges, when the researcher focuses on the policies related to the forest management in the region. A consideration of the ethical aspects is motivated by the fact that indigenous communities depend directly on the forests’ services and resources, and therefore are the most affected by the impact of deforestation. To establish an ethics on the participative approach on forest management could strengthen collaboration between local communities, multinational companies and government. / Philosophy, Practical and Systematic Theology / M. Th. (Theological ethics)
14

Ecological Management of Tropical forests: Implications for climate change and Carbon Fluxes

Djomo Njepang, Adrien 12 November 2010 (has links)
No description available.
15

Preserving trees

Skead, C J (Cuthbert John) 19 May 1959 (has links)
Article written by C. J. Skead to the East London Daily Dispatch (dated 19 May 1959), bringing attention to the deforestation of the Fort Grey forest by Mr C Miles Warren (MP). The article is acompanied by a harndwitten note stating "Mr C Miles Warren, M.P. had the contract for removing the forest and did very well out of it, especially with box-wood!! Hence the letter which would have [illegible] his consumers".
16

The impact of forest degradation on carbon stocks of forests in the Matiwane area of the Transkei, South Africa

Mangwale, Kagiso January 2011 (has links)
This study focused on assessing the condition and creating a carbon inventory of forests in the Matiwane area of the Transkei. This entailed the use of aerial photography in tracing forest cover change from 1942 to 2007 coupled with ground-truthing to assess whether the forests have in any way endured degradation over the years with a potential reduction in carbon stocks as a result. This study revealed both the loss and gain of biomass in the area with a general trend of forests being continuously converted to agricultural fields resulting in reduced forest area, stem density, tree density and carbon loss in different pools of the forests, reflecting that these forests are degraded. The conversion has resulted in the reduction in the number of species from a mean of 11±0.57 species/200m² in intact forests to 1±0.23species/200m² plot in degraded forests. It was also revealed that approximately 5.2 % (791 hectares) of 15 352 hectares of forest area was lost as a result of the conversion of forest land to agricultural fields from 1942 to 2007 with 99 % of the clearing occurring in the last 33 years (1974-2007) and of which 60 % ( 4 77 hectares) occurred from 1995 to 2007, indicating that forest degradation in these forests is on the increase. The assessment also revealed some areas that were nonforest in 1942 that have accumulated woody biomass (BAA), composed mainly of Acacia sp accounting for 51.18 MgC.ha⁻¹ (Megagrams of carbon per hectare) and total carbon stocks of 0.02 TgC (Teragrams of carbon). The degradation of these forests induced a reduction in carbon stocks from 311.68±23.69 MgC.ha⁻¹ (to a soil depth 0-50 cm) in intact forest to 73.46±12.34 MgC.ha⁻¹ in degraded forests. The total carbon stocks in the degraded forests were approximated at 0.06 TgC and the BAA areas 0.02 TgC with 4.7 TgC in intact forests. The degradation of these forests has resulted in the net carbon loss of 0.19 TgC between 1942 and 2007 but 4.76 TgC is still locked in these forests. The large difference in carbon stocks between intact and degraded forests indicated the need to reduce the degradation of these forests to prevent further carbon loss and reduction of the carbon sequestration potential of these forests.
17

Múltiplas ameaças e um mosaico de manchas de habitat de diferentes qualidades: a persistência de mamíferos de maior porte em uma região de pós-fronteira na Amazônia / Multiple threats and a mosaic of habitat patches of varying quality: the persistence of large mammals across a post-frontier Amazonian region

Paula Elias Moraes 21 September 2016 (has links)
A expansão das atividades humanas está associada a várias ameaças antrópicas que afetam a biodiversidade tropical, especialmente a perda e fragmentação de habitat, o continuado crescimento populacional humano e a expansão de infraestrutura, como estradas e rodovias. Embora seja esperado que as ameaças antrópicas interajam e criem mosaicos de manchas de habitat de diferentes qualidades, há ainda poucos estudos sobre os efeitos aditivos e interativos de diferentes ameaças sobre a biodiversidade ou sobre a capacidade de espécies nativas de usar remanescentes de diferentes qualidades. De fato, a maioria dos estudos focaram em apenas uma ou poucas ameaças isoladas, na escala do fragmento em vez da escala da paisagem e não consideraram as variações na qualidade dos remanescentes. Mamíferos de maior porte são um bom modelo de estudo porque possuem um conjunto de características que os tornam particularmente vulneráveis a várias ameaças antrópicas. Dada a dificuldade de obter dados sobre estas espécies elusivas em escalas espaciais adequadas, entrevistas com moradores locais vêm sendo cada vez mais usadas para acessar a distribuição de mamíferos de maior porte, e podem fornecer informações confiáveis. Através da estimativa da ocorrência de 15 espécies de mamíferos de maior porte por meio de entrevistas com o chefe de 12 unidades domésticas em cada uma de 20 paisagens em uma região de pós-fronteira de 1 milhão ha na Amazônia, investigamos: (i) que tipo de habitat e em qual escala espacial está associado com a ocorrência das espécies, e (ii) os efeitos, a importância relativa e as interações de quatro ameaças antrópicas - cobertura de habitat, fragmentação de habitat, densidade populacional humana e densidade de estrada - sobre a persistência das espécies. Dados de presença/ausência nos arredores de 227 unidades domésticas foram analisados usando modelos lineares generalizados mistos e seleção de modelos baseada no Critério de Informação de Akaike em duas etapas. A persistência das espécies maiores e ameaçadas não foi necessariamente afetada pela qualidade do habitat, mas elas responderam majoritariamente a cobertura de habitat em escalas maiores. A chance de persistência de todas as espécies - mesmo das duas menores, que não responderam à perda de habitat isoladamente - foi afetada por alguma combinação das quatro ameaças antrópicas. Efeitos aditivos entre as ameaças antrópicas foram mais importantes do que as interações entre elas na determinação da ocorrência de mamíferos de maior porte. Enquanto os efeitos da perda de habitat foram mais fortes do que os efeitos da fragmentação de habitat per se, a densidade de estradas foi tão importante quanto à perda de habitat para a ocorrência das espécies. Por último, não houve um padrão claro em termos do grau de ameaça e do tamanho corpóreo por trás da reposta dos mamíferos de maior porte a ameaças antrópicas combinadas. Nosso estudo sugere que áreas protegidas em terras públicas ou privadas na Amazônia devem ser grandes para assegurar a persistência de mamíferos de maior porte, mas podem incluir mosaicos de florestas primárias e secundárias. Os resultados também ressaltam a necessidade de considerar os impactos acumulados de múltiplas ameaças simultaneamente - em especial, as consequências da expansão da malha viária - em planejamentos e manejos, de maneira a evitar subestimar a chance de extinções. Evitar que paisagens na Amazônia se tornem muito desmatadas e alteradas é fundamental, dado que a persistência até mesmo das espécies mais comuns pode ser prejudicada, afetando um dos serviços ecossistêmicos mais importantes para moradores locais - a carne de caça - e potencialmente erodindo o valor que estes atribuem às florestas / The expansion of human activities is associated to a myriad of anthropogenic threats that affect tropical biodiversity, especially habitat loss and fragmentation, the continued human population growth and the expansion of infrastructure, as roads and highways. Although anthropogenic threats are expected to interact and to create mosaics of patches of varying quality, their additive and interaction effects on biodiversity, as well as the extent native species are able to use remnants of distinct quality, have yet been poorly studied. Indeed most studies focused on only one or few threats in isolation, on the patch rather than the landscape scale and did not considered the varying quality of remnants. Large mammals are a good study model as they have a set of traits that make them particularly vulnerable to several anthropogenic threats. Due to the difficulties in gathering data on these elusive species at adequate spatial scales, interviews with local residents have increasingly being used to access their distribution and can provide reliable information. By estimating the occurrence of 15 large mammal species through interviews with the head of 12 households within each of 20 landscapes across a 1-million ha post-frontier region in Amazonia, we investigated: (i) which habitat type at which spatial scale is associated with species occurrence, and (ii) the effects, relative importance and interactions of four anthropogenic threats - habitat cover, habitat fragmentation, human population density and road density - on species persistence. Presence/absence data across the surroundings of 227 households was analyzed using generalized linear mixed-effects models, and a two-step model selection based on Akaike’s Information Criteria. The persistence of larger and endangered species was not necessarily affected by habitat quality, but they responded to habitat cover mostly at larger spatial scales. The chance of persistence of all species - even the two smallest that were not affected by habitat loss alone - was disrupted by some combination of the four anthropogenic threats. Additive effects between anthropogenic threats were more important than their interaction in determining the occurrence of large mammals. While the effects of habitat loss were stronger than the effects of habitat fragmentation per se, road density was as important as habitat loss to species occurrence. Finally, there was no clear pattern in threat status or body size underlying the response of large mammals to combined anthropogenic threats. Our study suggest that protected areas in public or private lands in Amazonia should be large to secure the persistence of large mammals, but may include mosaics of primary and secondary forest. The findings also highlight the need to take into account the accumulated impacts of multiple threats simultaneously - particularly, the consequences of the expansion of the road network - in planning and management, as a way to avoid underestimating the chance of extinctions. Preventing Amazonian landscapes to become heavily deforested and altered is critical, as the persistence of even common species can be impaired, affecting one of the most important ecosystem services provided to local residents - bushmeat - and potentially eroding the value people attribute to forests
18

The application of a landscape diversity index using remote sensing and geographical information systems to identify degradation patterns in the Great Fish River Valley, Eastern Cape Province, South Africa

Tanser, Frank Courteney January 1997 (has links)
Using a range of satellite-derived indices I describe. monitor and predict vegetation conditions that exist in the Great Fish River Valley, Eastern Cape. The heterogeneous nature of the area necessitates that the mapping of vegetation classes be accomplished using a combination of a supervised approach, an unsupervised approach and the use of a Moving Standard Deviation Index (MSDI). Nine vegetation classes are identified and mapped at an accuracy of 84%. The vegetation classes are strongly related to land-use and the communal areas demonstrate a reduction in palatable species and a shift towards dominance by a single species. Nature reserves and commercial rangeland are by contrast dominated by good condition vegetation types. The Modified Soil Adjusted Vegetation Index (MSA VI) is used to map the vegetation production in the study area. The influence of soil reflectance is reduced using this index. The MSA VI proves to be a good predictor of vegetation condition in the higher rainfall areas but not in the more semi-arid regions. The MSA VI has a significant relationship to rainfall but no absolute relationship to biomass. However, a stratification approach (on the basis of vegetation type) reveals that the MSA VI exhibits relationships to biomass in vegetation types occurring in the higher rainfall areas and consisting of a large cover of shrubs. A technique based on an index which describes landscape spatial variability is presented to assist in the interpretation of landscape condition. The research outlines a method for degradation assessment which overcomes many of the problems associated with cost and repeatability. Indices that attempt to provide a correlation with net primary productivity, e.g. NDVI, do not consider changes in the quality of net primary productivity. Landscape variability represents a measure of ecosystem change in the landscape that underlies the degradation process. The hypothesis is that healthy/undisturbed/stable landscapes tend to be less variable and homogenous than their degraded heterogenous counterparts. The Moving Standard Deviation Index (MSDI) is calculated by performing a 3 x 3 moving standard deviation window across Landsat Thematic Mapper (TM) band 3. The result is a sensitive indicator of landscape condition which is not affected by moisture availability and vegetation type. The MSDI shows a significant negative relationship to NDVI confirming its relationship to condition. The cross-classification of MSDI with NDVI allows the identification of invasive woody weeds which exhibit strong photosynthetic signals and would therefore be categorised as good condition using NDVI. Other ecosystems are investigated to determine the relationship between NDVI and MSDI. Where increase in NDVI is disturbance-induced (such as the Kalahari Desert) the relationship is positive. Where high NDVI values are indicative of good condition rangeland (such as the Fish River Valley) the relationship is negative. The MSDI therefore always exhibits a significant positive relationship to degradation irrespective of the relationship of NDVI to condition in the ecosystem.
19

Do Forest Commons Contribute to International Environmental Initiatives? A Socio-Ecological Analysis of Nepalese Forest Commons in view of REDD+

Luintel, Harisharan 26 July 2016 (has links)
Forests in developing countries have the potential to contribute to global efforts to mitigate climate change, promote biodiversity and support the livelihoods of rural, local people. Approximately one-fourth of such forests are under the control of local communities, which primarily manage forests for subsistence and to meet their livelihood needs. The trend of bottom-up community control is increasing through the adoption of decentralization reforms over the last 40 years. In contrast, the United Nations has introduced the top-down program, Reducing Emissions from Deforestation and Forest Degradation (REDD+) for the conservation and enhancement of forest carbon and the sustainable management of forest in developing countries. REDD+ incentivizes forest-managing communities to sequester carbon and reduce emissions. REDD+ has created hope for managing forests to mitigate climate change and has created fear that the new initiative may not be effective and may not ensure continuing forest-managing community benefits. However, little research has been conducted to answer these concerns. By taking nationally representative data from Nepalese community-managed forests (“forest commons"), I bring insights into whether and how these forests can contribute to REDD+ initiatives, particularly as they relate to carbon sequestration, biodiversity, equity in benefit sharing and collective action. My results indicated the highly variable carbon and biodiversity in the forest plots across the country, depicting the availability of space for additional growth in carbon storage and biodiversity conservation. My results also reflect the complex and varied relationships of carbon with different indices of biodiversity at the national level, across geographic and topographic regions, and in forests with varying canopy covers. Weak positive relationships between carbon sequestration and biodiversity conservation indicate the possibility of synergies between carbon-forestry and biodiversity conservation. I also found that the formal community forestry program (CFP) has clearly positive impacts on biodiversity conservation and household-level equity in benefit sharing and a negative impact on carbon sequestration at the national level. However, disaggregated results of impacts of CFP on biodiversity, carbon and equity across geography, topography, forest quality and social groups display mixed results i.e., either positive or negative or neutral. I also identified that different drivers of collective action have different (i.e., positive, neutral, and negative) associations with carbon sequestration, which either supports or challenges established knowledge. In aggregate, my research indicates the potential of contribution by forest commons, and specially the CFP, to global environmental initiatives such as REDD+. It suggests that targeted, dedicated policies and programs to increase carbon sequestration, biodiversity conservation and foster equity and collective actions are critical. In addition, my results also contribute to the growing literature on socio-ecological implications of forest commons that demonstrated the need of interdisciplinary research to understand human-nature relationships in the changing context.
20

Effects of forest fragmentation on biomass in tropical forests / Efeitos da fragmentação florestal na biomassa em florestas tropicais

Melito, Melina Oliveira 16 December 2016 (has links)
In spite tropical forests are the most important terrestrial global carbon sinks due to carbon storage in aboveground biomass, it is also the primary target of deforestation. The conversion of Tropical forests into anthropogenic areas might disrupt biological flux and also lead to severe microclimatic changes at forest edges. These combined effects can trigger profound changes in plant composition through both high mortality of fragmentation-sensitive species and proliferation of disturbed-adapted species which will ultimately impacts carbon storage. Thus, our main objective in this study was understand the role of human-induced disturbances in modulate the dimension of biomass loss at tropical forests. We applied a systematic literature review searching for empirical evidences that edge effects can drive biomass loss in tropical forests (Chapter 2). Our findings highlighted the gap of knowledge about the pattern and process related to biomass loss in tropical forests. To strengthen this understanding, we formulated a conceptual model linking landscape structure and patch-level attributes to severity of edge effects affecting aboveground biomass. Our model hypothesizes that habitat amount, isolation, time since edge creation, and the synergism between edge distance, patch size, and matrix type are the main drivers of biomass loss in anthropogenic tropical forests. We thus used a large plant dataset (18 503 trees ≥ 10 cm dbh) from 146 sites distributed across four Mexican and four Brazilian rainforest regions to test our conceptual model predictions, specifically the influence of forest cover, site isolation, edge distance, patch size and type of matrix on biomass (Chapter 3). We observed that carbon-rich sites presented species that are typical of old-growth forests (shade-tolerant, large-seeded, zoocoric) contrasting to carbon-poor sites composed by disturbed-adapted species (pioneer occupying the understory). Large shade-tolerant trees (≥ 40 cm dbh) were impacted severely by the combination of forest loss and edge effects. Edge distance, patch size, and the amount of open-matrix strongly influence small shade-tolerant trees (≤ 20 cm dbh). Although our results do not fully corroborate the initial predictions of the conceptual model, they support the idea that landscape composition interact with patch structure and ultimately impacts biomass stocks in fragmented tropical forests. Finally, we further investigated if the disturbance level of the region influences plant-structure responses to forest loss (Chapter 4). Biomass, but not plant density, was affected by forest loss in regions with intermediate disturbance levels, i.e. regions showing a combination of moderate deforestation (20-40% of remaining forest cover) disturbed during the past 30-60 years, high defaunation but harboring relictual populations of large-mammals, and areas mostly composed by heterogeneous matrices. In general, our findings highlight that both landscape composition and patch structure are the main drivers of biomass loss in Neotropical forests, and that the landscape context must be considered to obtain more reliable estimations of carbon emissions due to forest degradation. Landscape planning (e.g. restoration of forest cover) should be included in conservation strategies in order to sustain carbon storage. Moreover, we advocate that conservation initiatives will be less costly and more effective if implemented in areas under intermediate disturbance levels / Apesar das florestas tropicais serem a mais importante fonte mundial de carbono da porção terrestre do globo devido ao armazenamento de carbono na biomassa acima do solo, elas são também o alvo primário do desmatamento. A conversão das florestas Tropicais em áreas antropogênicas pode interromper o fluxo biológico e também levar a severas mudanças microclimáticas na borda dos fragmentos. A combinação desses efeitos pode engatilhar profundas mudanças na composição da vegetação através tanto da mortalidade de espécies sensíveis à fragmentação como também pela proliferação de espécies adaptadas distúrbios, com impactos finais nos estoques de carbono. Assim, o maior objetivo desse estudo foi compreender o papel dos distúrbios induzidos pelo homem na modulação da dimensão da perda de biomassa em florestas Tropicais. Nós aplicamos uma revisão sistemática da literatura procurando por evidências empíricas de que o efeito de borda pode levar a perda de biomassa em florestas tropicais (Capítulo 2). Nossos resultados destacam a lacuna de conhecimento entre padrões e processos relacionados à perda de biomassa em florestas Tropicais. Para fortalecer esse conhecimento, nós formulamos um modelo conceitual conectando estrutura da paisagem e atributos na escala do fragmento à severidade do efeito de borda, e assim afetando a biomassa acima do solo. Nosso modelo hipotetiza que a quantidade de hábitat, o isolamento, o tempo desde a formação da borda e o sinergismo entre tamanho do fragmento, distância da borda e tipo de matriz são os principais condutores de perda de biomassa em florestas Tropicais antropogênicas. Utilizando um grande banco de dados (18 503 árvores ≥ 10 cm dap) provenientes de 146 locais distribuídos em quatro regiões de floresta úmida no México e quatro no Brasil, nós então testamos as predições do nosso modelo conceitual. Especificamente, a influência da cobertura florestal, isolamento, distância da borda, tamanho do fragmento e tipo de matriz sobre a biomassa (Capítulo 3). Nós observamos que áreas com muito carbono apresentaram espécies típicas de florestas maduras (tolerantes ao sombreamento, zoocóricas, com sementes grandes) contrastando com áreas com pouco carbono compostas por espécies adaptadas à distúrbio (pioneiras ocupando o sub-bosque). Árvores grandes tolerantes ao sombreamento (≥ 40 cm dap) foram impactadas severamente pela combinação de perda de cobertura florestal e efeitos de borda. Distância da borda, tamanho do fragmento e a extensão da área de matriz aberta influenciaram fortemente as árvores pequenas tolerantes a sombreamento (≤ 20 cm dap). Apesar dos nossos resultados não corroborarem completamente as predições iniciais do nosso modelo conceitual, eles dão suporte à ideia de que a composição da paisagem interage com a estrutura do fragmento com impactos finais nos estoques de biomassa em florestas Neotropicais. Por fim, nós investigamos se o nível de distúrbio da região pode influenciar nas respostas da estrutura da vegetação à perda de cobertura florestal. Biomassa, mas não a densidade de indivíduos, foi afetada pela perda de cobertura florestal em regiões com nível intermediário de distúrbio, i.e. regiões apresentando uma combinação de níveis moderados de desmatamento (20-40% de cobertura florestal remanescente) em que a perturbação ocorreu ao longo dos últimos 30-60 anos, com alto grau de defaunação mas ainda abrigando populações relictuais de grandes mamíferos e, em sua maioria, compostos por uma matriz heterogênea. Em geral, nossos resultados destacaram que tanto a composição da paisagem como a estrutura do fragmento são os principais condutores de perda de biomassa em florestas Neotropicais e que o contexto da paisagem deve ser considerado para se obter estimativas mais confiáveis de emissão de carbono devido à degradação florestal. O planejamento da paisagem (e.g. restauração da cobertura florestal) deve ser incluído em estratégias de conservação em ordem de sustentar o armazenamento de carbono. Além disso, nós defendemos que iniciativas de conservação serão menos custosas e mais efetivas se implementadas em áreas sob níveis intermediários de distúrbio

Page generated in 0.1558 seconds