Stability of pure even-aged conifer stands in Portugal

The slenderness coefficient of a tree is defined as the ratio of total height (h) to diameter at 1.3 m above ground (d). For the stand level, the slenderness coefficient is calculated using the quadratic mean diameter and the height of the mean tree as (hg/dg). There is well known that a straight relationship exist between the slenderness coefficient of the stands and the risk of stem breakage or tree fall due to abiotic factors such as the wind or snow. When ignoring or neglecting the aspects related to the stands stability, risks of wood production losses caused by storms can be high. Storms of 1982 and 1999 with wind speeds above 100 Km h-1 have particularly damaged extensive forest areas (mainly conifer stands) in the Central European Plain. As the result of learning from these occurrences, the combined effect of hg/dg coefficient and dominant height was found to be a useful and practical criterion for the diagnosis of the stability situation (wind-firmness) of pure even-aged stands of conifer species. Three stability levels have been considered which could be presented in a simple diagram: optimum, moderate and instable. A stand that is let to grow naturally, without intervention, quickly attains the instability level, being more vulnerable to winds of great strength. In Portugal there have been no meaningful episodes of windthrow in conifer stands where the maritime pine (Pinus pinaster Ait.) is the most representative species. Future climate scenarios forecast an increase in the growth potential in some forest sites. Higher dominant heights may increase the risk of tree damage caused by violent storms. In this study, an evaluation of the stability status of Portuguese pure even-aged stands of maritime pine and other conifer species is made, based on data from the national forest inventory (NFI) and using stability diagrams. The analysis is undertaken by territorial units of level II (NUT II) with the support of GIS software. Characteristics of the stands that lay in each stability level are compared and discussed

Modelo para a predição de indicadores de gestão florestal sustentável em povoamentos de pinheiro bravo em Portugal

O Pinheiro bravo (Pinus pinaster Ait.) é a espécie resinosa autóctone mais representativa em Portugal continental. Segundo os resultados da mais recente revisão do Inventário Florestal Nacional (IFN5), a espécie ocupa uma área de 885,000 hectares, representando 27% da área florestal do país. Neste trabalho apresenta-se o resultado do desenvolvimento de um conjunto de ferramentas de modelação para a predição de indicadores de gestão florestal sustentável em povoamentos puros regulares de pinheiro bravo em Portugal. Neste sentido desenvolveu-se um conjunto de sub-modelos, tendo-se iniciado por um sistema de equações para a predição compatível de volume total e volume mercantil adequado a diferentes definições de volume. Foi adotada uma abordagem de integração de funções de perfil do tronco, tendo-se usado dados de análise de tronco. Também com base em dados de análise de tronco, foi desenvolvido um modelo dinâmico para o crescimento dos povoamentos em altura dominante, aplicando a metodologia das equações às diferenças algébricas generalizadas (GADA). Recorrendo a dados contendo medições irregularmente espaçadas no tempo, efetuadas em ensaios de desbastes, foi desenvolvido um modelo de previsão anual da probabilidade de sobrevivência e do crescimento da árvore individual em diâmetro e altura. Avaliou-se também a biomassa e stocks de carbono ao nível da folhada, vegetação no sub-coberto, madeira morta e no solo mineral, em povoamentos regulares de pinheiro bravo. Os dados recolhidos foram juntos a dados já existentes para desenvolver um conjunto de equações para a previsão de stocks de carbono na folhada, vegetação no sub-coberto, madeira morta e no solo mineral, usando variáveis do povoamento, do clima e do solo

Sistema de predição de volumes total e mercantil compatível com diferentes definições de volume

O volume é a variável dendrométrica que mais tem sido utilizada para expressar o quantitativo lenhoso, sendo uma das mais importantes variáveis a obter em qualquer inventário florestal. É frequente, nos inventários florestais nacionais de diferentes países, observar-se a utilização de diferentes definições do volume da árvore individual. Neste trabalho desenvolve-se um sistema compatível de equações para estimar volume total e volumes mercantis, o qual foi concebido de forma a facilitar a conversão e subsequente comparação dos resultados de inventários florestais que utilizem diferentes definições de volume da árvore. O sistema contém também uma função de perfil do tronco que, quando devidamente integrada, garante a compatibilidade entre equações de perfil do tronco, volume total e volume percentual. O sistema apresenta bons resultados quando aplicado a dados de pinheiro bravo em Portugal representativos de todo o país e cobrindo árvores de diferentes dimensões

Climate change

Knowledge of factors that trigger human response to climate change is crucial for effective climate change policy communication. Climate change has been claimed to have low salience as a risk issue because it cannot be directly experienced. Still, personal factors such as strength of belief in local effects of climate change have been shown to correlate strongly with responses to climate change and there is a growing literature on the hypothesis that personal experience of climate change (and/or its effects) explains responses to climate change. Here we provide, using survey data from 845 private forest owners operating in a wide range of bio-climatic as well as economic-social-political structures in a latitudinal gradient across Europe, the first evidence that the personal strength of belief and perception of local effects of climate change, highly significantly explain human responses to climate change. A logistic regression model was fitted to the two variables, estimating expected probabilities ranging from 0.07 (SD +/-0.01) to 0.81 (SD +/-0.03) for self-reported adaptive measures taken. Adding socio-demographic variables improved the fit, estimating expected probabilities ranging from 0.022 (SD +/-0.008) to 0.91 (SD +/-0.02). We conclude that to explain and predict adaptation to climate change, the combination of personal experience and belief must be considered

The influence of Toll-like receptor 4 activation in human CD4 T cell function

Tese de mestrado, Ciências Biofarmacêuticas, Universidade de Lisboa, Faculdade de Farmácia, 2019O sistema imunitário dos mamíferos evoluiu de forma a proteger o hospedeiro e eliminar organismos patogénicos enquanto simultaneamente evita uma resposta imune excessiva perante bactérias e organismos comensais. A disrupção do extraordinário equilíbrio dos mecanismos desta resposta resulta frequentemente em inflamação crónica ou doenças autoimunes. Uma melhor compreensão dos mecanismos que regulam a tolerância do sistema imune é então crucial para desenvolver terapias que permitam o controlo de reação exacerbadas em situações de doença autoimune. Os recetores do tipo Toll (TLRs) detetam padrões moleculares característicos de patógenos e contribuem para a rápida iniciação de uma complexa resposta imunitária. Apesar de terem sido intensivamente estudados pela sua expressão em células do sistema inato, estudos recentes mostram que os linfócitos T também expressam estes TLRs e que a sua expressão pode afetar diretamente as funções da célula. Os linfócitos T são um componente chave do sistema imune adaptativo e respondem à presença de patógenos libertando citoquinas que ditam o desfecho da resposta inflamatória. Em particular, resultados anteriores do nosso grupo demonstraram que as células T CD4 humanas expressam TLR4, o recetor que reconhece lipopolissacarídeos (LPS) provenientes de bactérias. No presente trabalho demonstramos que a ativação do TLR4 tem um impacto direto em células T CD4 humanas, sem a interferência de células do sistema inato. A estimulação crónica destas células com condições não-polarizantes do recetor das células T (TCR), juntamente com LPS, levou a um aumento da ativação, sobrevivência e da proliferação das mesmas. Adicionalmente, a mesma estimulação consegue ajudar a redirecionar as células T auxiliares para que estas expressem menores níveis de interferão gama, e maiores níveis das interleucinas 10 e 17. Além disto, também foram isoladas células T CD4 de amostras de fígado humano que expressavam simultaneamente marcadores de residência no tecido e TLR4. Esta observação preliminar pode indicar que as nossas observações anteriores se alarguem ainda a células que residem no tecido. Os nossos resultados apoiam a ideia de que uma ativação consistente do TLR4 em células T CD4, em resposta a bactérias comensais, levam à redirecção das células produtoras de IL-17 para um fenótipo mais tolerante. Esperamos assim que este projeto abra portas a novos estudos que se foquem no papel da ativação direta do TLR em linfócitos T e na sua contribuição para a tolerância no sistema imune.The mammalian immune system has evolved to provide protection from environmental threats, eliminating pathogenic organisms and toxins whilst avoiding an excessive response in the presence of commensal organisms and bacteria. The disruption of this perfectly balanced mechanism of immune responsiveness often results in chronic inflammation and autoimmune disease. A better comprehension of the mechanisms that regulate immune tolerance is thus crucial to develop therapies that allow us to control exacerbated reactions in autoimmune illness. Toll-like receptors (TLRs) detect conserved microbial patterns and largely contribute to the rapid initiation of the highly complex protective mechanism that is the immune response. Despite having been intensively studied for their expression and role in innate immune cells, recent evidence shows that T lymphocytes also express these receptors and that their expression may directly affect cell function. T lymphocytes are a key component of the adaptive arm of the immune system and respond to pathogen encounters by releasing cytokines that dictate the outcome of the inflammatory response. Particularly, previous data from our group has demonstrated that human CD4+ T cells express TLR4, the molecular sensor of bacterial liposaccharide (LPS). In the present work, we provide evidence that the activation of TLR4 has a direct impact in human CD4+ T cells, without interference from innate immune cells. The chronic stimulation of these cells with non-polarizing TCR stimulation and LPS leads to enhanced activation, survival and proliferation. Furthermore, the same stimulation re-directed helper T cells into expressing lower levels of the pro-inflammatory cytokine interferon-gamma, but it increased the production of interleukin (IL) 17 and the immunoregulatory IL-10. Additionally, we isolated CD4+ T cells from human liver samples that simultaneously expressed markers of tissue residency and TLR4, which may broaden these findings to tissue resident T cells. Our results support the view that a consistent activation of TLR4 in CD4+ T cells in response to commensal bacteria leads to re-direction of IL-17-producing cells to a more tolerogenic phenotype. These findings thus pave the way for new studies that focus on the role of direct TLR signaling in T cells and their contribution to immunotolerance.The studies developed in this thesis were performed at CEDOC-NMS/UNL – Centro de Estudos de Doenças Crónicas, NOVA Medical Schoo

Modern silvoarable agroforestry in Portugal and its potential for CO2 sequestration

Portuguese National Science Foundatio

Contenido de Carbono y Nutrientes en Masas Regulares de Pino Marítimo en Portugal

To comply with the demands of the Kyoto Protocol, industrialized countries must reliably estimate the stored carbon (C) in different pools of forest ecosystems. The main objective of this study was to quantify the biomass, C and nutrients stocks in the forest floor, understory, downed dead wood (DDW) and mineral soil of even-aged maritime pine (Pinus pinaster Ait.) stands from three contrasting regions of Portugal. Assessing the specific contribution of DDW to the C and nutrients stocks and how C concentration in the plant material differs from 0.50, the reference value used in many practical applications, were also objectives of this research. Biomass content of forest floor was determined by a quadrat method. Sampling units of 1 m2 were used for the understory. The line intersection method was adopted for sampling DDW and the mineral soil was sampled at three depths. Concentrations of C and nutrients were obtained by chemical analysis of samples from soil and milled plant material. Biomass and C in the trees were obtained using published equations. Total C stocks ranged between 100.6 Mg ha–1 and 308.6 Mg ha–1. Mineral soil shared up to 70-74% of global stored C, being the main cause of the global C stock differences among regions. Phosphorous and potassium were at low to very low levels in the mineral soil and plant material. The contribution of DDW to the C and nutrients pools was negligible. The percentage of C in the plant material ranged between 52% and 54%.Para cumplir con las exigencias del Protocolo de Kyoto, los países industrializados deben estimar con fiabilidad el carbono (C) almacenado en los diferentes compartimientos de los ecosistemas forestales. El objetivo principal de este estudio fue cuantificar la biomasa, C y contenido de nutrientes, en el suelo del bosque, sotobosque, madera muerta (DDW) y en el suelo mineral de masas regulares de pino marítimo (Pinus pinaster Ait.) en tres regiones contrastantes de Portugal. Otros objetivos fueron, la evaluación de la contribución específica de DDW para el contenido total de C y nutrientes así como averiguar de qué modo la concentración de C en el material vegetal se diferencia del valor 0,50, referencia en muchas aplicaciones prácticas. El contenido en biomasa del suelo forestal se determinó por un método de cuadrícula. Para el sotobosque se utilizaron unidades de muestreo de 1 m2. El método de la línea de intersección se adoptó para el muestreo de DDW y se tomaron muestras a tres profundidades del suelo mineral. Las concentraciones de C y nutrientes se obtuvieron mediante el análisis químico de muestras de suelo y material vegetal molido. Para obtener la biomasa y C en los árboles fueron utilizadas ecuaciones publicadas. El total de las reservas de C oscilaron entre 100,6 Mg ha–1 y 308,6 Mg ha–1. El suelo mineral compartió, hasta el 70-74% del C total almacenado, siendo la principal causa las diferencias significativas de C almacenado entre regiones. Fósforo y potasio se encuentran en reducidas concentraciones en el suelo y en la vegetación. La contribución del DDW para la reserva de C y nutrientes fue despreciable. El porcentaje de C en el material vegetal varió entre 52% y 54%

Allometric equations for predicting mineralomass in high-forest chestnut stands in Portugal

The evaluation of nutrients in biomass tree-components is a process time consuming and expensive, often involving tree felling, not always possible or desirable. Thus, mineralomass prediction equations are an important tool for the quantification of the nutrients exported in management and harvesting activities towards to its replacement and sustainable management as well as to evaluate the effect of other disturbances in the balance of ecosystems. Thus, given the importance of the relationship of biomass and nutrients (mineralomass) for dynamic and sustainable management of chestnut woodlands, aboveground mineralomass was studied in sweet chestnut (Castanea sativa Mill.) high forest stands located in Northern Portugal. Nutrient specific prediction equations that allow estimating the mineralomass (N, P, K, Ca, Mg, S, B and C) above the ground, total and by components: stem-wood, stem-bark, branches, leaves and flowers, based on tree dendrometric variables, DBH (diameter breast height) and total height, were developed. Linear and non-linear regression estimation methods were used. Data analysis is based on information collected in destructive analysis of thirty-four felled trees, distributed by the existing diameter classes (10-65 cm) in three adult chestnut stands. Several linear and nonlinear equations were fitted by the least squares method to select models. A simultaneous fit by SUR method using iterative seemingly unrelated regression (ITSUR) was used for the final selected models. The best fitting models are presented.info:eu-repo/semantics/publishedVersio

Prediction of annual tree growth and survival for thinned and unthinned even-aged maritime pine stands in Portugal from data with different time measurement intervals

The Portuguese national forest strategy published in 2006 divided the Portuguese forest territory into three main functions: wood production, multifunctional systems and protected areas. Wood production is mostly related with pure even-aged stands of two species, the maritime pine (Pinus pinaster Ait.) and the blue gum (Eucalyptus globulus Labill.). Sustainable forest management of these productive areas requires adequate prediction of stocks and growth. To face the challenge of fast changing scenarios, growth models need to provide adequate predictions in a wide range of time intervals. Individual-tree growth and yield models are especially useful for management planning, because they are capable of simulating a wide variety of management activities, particularly thinning. They often describe annual changes in growth and survival of individual-tree providing detailed information about stand structure and composition. Available data sets for fitting individual-tree models frequently have measurement intervals greater than 1 year and many times these intervals are irregularly spaced. Also thinning can occur between measurements. This causes difficulty when modelling annual tree growth and survival. An annual individual-tree growth and survival model is developed for pure even-aged stands of maritime pine in Portugal, using data with irregularly spaced measurement time intervals and considering thinning effects. The central components of the model are the equation for diameter growth, the equation for height growth and a survival function. Variable growth and survival rates are assumed in the modelling approach. The model is distance-independent and will be useful for intensively managed areas of pure even-aged stands of maritime pine in Portugal

Investigating factors that affect willingness to pay an analysis on freemium social media apps

While social media has grown in popularity and usage in recent years, little is known about users' willingness to pay for the premium version of them. In this study, we investigate how consumers' perceived value is associated with their intention to use freemium services and to purchase premium content. We employ data gathered through an online survey (N=200) among the users of freemium social media networks, like LinkedIn, YouTube, Reddit and Flickr and tested 15 different hypotheses, using PLS-SEM. Firstly, we find support for the security hypothesis proposed in this study, indicating that if users value the security component of the freemium social media, they will have a higher intention to use the service overall. Secondly, the higher quality of the freemium service leads to higher usage intentions, which further leads to higher purchase intentions. Thirdly, the price value of freemium services shows to have a negative association with the intention to purchase premium content. Fourthly, social platform community is found to positively affect premium purchases. Lastly, we find support for the usage frequency hypothesis proposed in this study, indicating that if a user establishes a habit of using a social media, he will eventually decide to buy the premium version. The current study's findings contribute to the uniqueness of the freemium business model, implying that increasing perceived value of the freemium service, improving security, or increasing usage frequency can all contribute to and subtract from future profitability via increased retention on the one hand and reduced monetization on the other.Embora as redes sociais tenham crescido em popularidade e utilização nos últimos anos, pouco se sabe sobre a vontade dos utilizadores de pagar pela versão premium das mesmas. Neste estudo, investigamos como o valor percebido pelos consumidores está associado à sua intenção de utilizar os serviços freemium e de adquirir conteúdos premium. Investigamos os dados recolhidos através de um inquérito online (N=200) e testamos 15 hipóteses diferentes, utilizando PLS-SEM. Em primeiro lugar, encontrámos suporte para a hipótese de Segurança proposta neste estudo, indicando que os utilizadores que valorizam a componente de segurança nas redes sociais freemium terão uma maior intenção de utilizar o serviço. Em segundo lugar, a maior qualidade da rede social leva a maiores intenções de utilização, o que leva a maiores intenções de compra. Em terceiro lugar, o valor do preço dos serviços freemium mostra ter uma associação negativa com a intenção de compra de conteúdos premium. Em quarto lugar, observámos que a comunidade social afeta positivamente as compra da versão premium. Finalmente, encontrámos apoio para a hipótese de frequência de utilização proposta neste estudo, indicando que se um utilizador estabelecer o hábito de utilizar uma rede social freemium, acabará por decidir comprar a versão premium. As conclusões do presente estudo realçam a singularidade do modelo de negócio freemium, implicando que o aumento do valor percebido do serviço, a melhoria da segurança, ou o aumento da frequência de utilização podem contribuir ou subtrair da rentabilidade futura através do aumento da retenção ou da redução da monetização