Loading...
5 results
Search Results
Now showing 1 - 5 of 5
- Combined disaggregation of agricultural land uses, livestock numbers and crops' production: an entropy approachPublication . Xavier, António; Freitas, Maria de Belém; De Sousa Fragoso, R. M.This paper presents several combined agricultural data disaggregation models in order to recover the farms' land uses, the livestock numbers and main crops' productions. The proposed approach estimates incomplete information at disaggregated level through entropy, using an information prior, and generating information for a combined calculation use of data in the estimation of other variables. The models were applied to the region of Algarve, to some rural pilot areas (Salir-Ameixial-Cachopo and Alcoutim) for livestock data, since this data in some Algarve's inland areas is needed for a European forest fire prevention project, and to the agrarian zones in a more complex framework. The results are promising. They were validated, in cross reference to real data, having proven to be valid and reliable. The total error was small and a considerable level of information heterogeneity was recovered. The total error was about 27,9% for the counties' land uses and 21% for the agrarian zones, and for the livestock it was also acceptable. The level of heterogeneity recovered was always higher than 50%, revealing some improvements regarding previous studies.
- A desagregação espacial de dados agrícolas: aplicação de uma abordagem baseada na máxima entropia ao concelho de Castelo de VidePublication . Xavier, António; Martins, Maria de Belém; Fragoso, Rui Manuel de SousaThe purpose of this dissertation is to complement the lack of data related to the forest and agricultural occupation and the livestocks in Castelo de Vide. To solve the research problem a model of data disaggregation was developed, taking the utmost of previous information available in earlier studies. The proposed model was based on the ideas of generalized maximum entropy (GME) and minimum generalized crossed entropy (MGCE), in order to obtain a series of disaggregated data related to the forest and agricultural occupation, considering two levels of disaggregation and following two steps: 1) the creation of a basis at the aggregated level (Markov transition matrixes, estimated by the maximum entropy); 2) data disaggregation, based on the previous established basis. The model also involves two application variants: simultaneous disaggregation of data as well as a direct one (to solve the problems that might appear in the previous one and maximize the recovered information). Moreover, a model based on these principles is proposed to the disaggregation of the livestock data. The model is applied to the disaggregation of data in the municipality of Castelo de Vide. The results obtained in the process of direct disaggregation of the forest and agricultural occupation and livestock have shown to be reliable. They have been validated in the year of 1999, submitted to experts? opinions, to other sources of information and compared to the results of other methodologies. The analysis of the results showed that the forest and agricultural occupation of Alto Alentejo and Castelo de Vide after 1999 tend to be more homogeneous, with a strong domain of permanent pastures, and there is a shortage of certain livestocks (sheep and goats). The several CAP changes have had effects in Alto Alentejo and Castelo de Vide, since they have contributed to a larger extensification of the practice of agriculture and to the decline of traditional productions.
- Um modelo bioeconómico para a gestão sustentável das florestas mediterrâneasPublication . Xavier, António; Freitas, Maria de Belém; Fragoso, Rui Manuel de Sousa; Panagopoulos, ThomasAs florestas mediterrâneas contêm uma diversidade vegetal, animal e biológica considerável e são relevantes para a vida das populações locais, contudo estão sujeitas a vários riscos, um dos quais é o risco de incêndios florestais. Para potenciar e valorizar as florestas mediterrâneas e as áreas agrícolas que se situam junto a elas, é necessário uma solução de gestão integrada que as valorize e maximize os benefícios que delas retiramos. Assim, de forma a atingir este objetivo, desenvolveu-se um modelo de programação matemática que integra as perspetivas biológica, ambiental e económica na gestão das áreas agrícolas e florestais, considerando todas as atividades existentes no território. O modelo de gestão integrado considera as características das unidades biofísicas que compõem o território objeto de estudo, as tecnologias de produção, conservação de bens agro-florestais e as preferências dos gestores para delinear uma estratégia eficiente com vista a desenvolver um plano de gestão sustentável da floresta. É um modelo de programação matemática estocástica discreta de equilíbrio estático em que se pretende contribuir para melhorar a situação dos diferentes proprietários, dotando os gestores de instrumentos que lhes permitam tomar decisões fundamentadas e consistentes com os vários fatores de natureza económica, ambiental e social. Para além do modelo de gestão proposto, foram desenvolvidos dois modelos auxiliares são complementares ao modelo de gestão e que permitem o aperfeiçoamento dos resultados: 1) modelo auxiliar de definição de preferências de gestão; 2) modelo de localização que permite fazer a redistribuição dos resultados do plano de gestão para o nível da parcela. A abordagem metodológica proposta foi aplicada numa Zona de Intervenção Florestal (ZIF) piloto situada no interior da Região do Algarve: a ZIF Arade-Alte/ S. B. Messines. Os resultados demonstram que a abordagem metodológica proposta permitiu definir um plano de gestão completo calculando a melhor situação de compromisso para critérios chave na gestão florestal. Complementarmente, foi possível obter resultados com um enorme detalhe nas diferentes parcelas de terrenos, sendo provado que esta abordagem é uma ferramenta útil para o gestor.
- Integration of fire risk in a sustainable forest management modelPublication . Costa Freitas, Maria de Belem; Xavier, Antonio; Fragoso, RuiIn Mediterranean areas, forest fires are a considerable risk most years. The seasonality of the climate with a dry summer, high temperatures and low rainfall (which implies increased flammability of materials) is one of the main factors in the ignition and progression of fires. This factor conjugated with more favourable biophysical conditions (e.g., high slopes, aspect) leads to easy propagation and the increasingly destructive power of such phenomena. To prevent and reduce the consequences of forest fires, it is necessary to simulate and forecast the territory use and management, not only focused on forest areas, but also on all land uses and agricultural activities that may coexist there, considering the probability of fire occurrence. The objective of this paper is to present a methodological approach to address the integration of fire risk in integrated Mediterranean forest management models. The methodological approach considers simultaneously the climatic conditions through different times of the year (more or less favourable to forest fire damage) and structural conditions addressed to land uses, aspect, slope, roads and demographic density. The methodological approach was implemented in a management area located in the Algarve, in southern Portugal. The results for the Algarve region showed that the proposed approach is very useful for managers, since it allowed the calculation of fire susceptibility, vulnerability and fire damage, according to several climatic scenarios. It also allowed the incorporation of different paths regarding different fire risk conditions and the minimization of risk due to fire damage through different management responses.
- An integrated decision support system for the Mediterranean forestsPublication . Costa Freitas, M. B.; Xavier, António; Fragoso, R.Mediterranean forests contain a relevant biological diversity and are relevant for local economy. However, they are subject to various risks, particularly the risk of forest fires. This turns the critical decisions of forest managers, affecting both the long-term future of the forest and daily activities, to be difficult. To simulate decisions, and help managers and policy makers, a decision support system, which integrates the biological, environmental and economic management perspectives of agricultural and forest areas, was developed and considers the activities existing in the territory. The decision support system considers the characteristics of the biophysical units that comprise the territorial study area, production technologies and conservation of agro-forestry goods and preferences of managers or stakeholders. The proposed approach was applied in a pilot Forest Intervention Zone (FIZ) located within the Algarve region inner land. The results show that the decision support system proposed is an important tool for managing the territory and for implementing the manager's decisions. (C) 2015 Elsevier Ltd. All rights reserved.