7 resultados para quercus suber
em Repositório Científico da Universidade de Évora - Portugal
Resumo:
Forest biomass has been having an increasing importance in the world economy and in the evaluation of the forests development and monitoring. It was identified as a global strategic reserve, due to its applications in bioenergy, bioproduct development and issues related to reducing greenhouse gas emissions. The estimation of above ground biomass is frequently done with allometric functions per species with plot inventory data. An adequate sampling design and intensity for an error threshold is required. The estimation per unit area is done using an extrapolation method. This procedure is labour demanding and costly. The mail goal of this study is the development of allometric functions for the estimation of above ground biomass with ground cover as independent variable, for forest areas of holm aok (Quercus rotundifolia), cork oak (Quercus suber) and umbrella pine (Pinus pinea) in multiple use systems. Ground cover per species was derived from crown horizontal projection obtained by processing high resolution satellite images, orthorectified, geometrically and atmospheric corrected, with multi-resolution segmentation method and object oriented classification. Forest inventory data were used to estimate plot above ground biomass with published allometric functions at tree level. The developed functions were fitted for monospecies stands and for multispecies stands of Quercus rotundifolia and Quercus suber, and Quercus suber and Pinus pinea. The stand composition was considered adding dummy variables to distinguish monospecies from multispecies stands. The models showed a good performance. Noteworthy is that the dummy variables, reflecting the differences between species, originated improvements in the models. Significant differences were found for above ground biomass estimation with the functions with and without the dummy variables. An error threshold of 10% corresponds to stand areas of about 40 ha. This method enables the overall area evaluation, not requiring extrapolation procedures, for the three species, which occur frequently in multispecies stands.
Resumo:
Remote sensing is a promising approach for above ground biomass estimation, as forest parameters can be obtained indirectly. The analysis in space and time is quite straight forward due to the flexibility of the method to determine forest crown parameters with remote sensing. It can be used to evaluate and monitoring for example the development of a forest area in time and the impact of disturbances, such as silvicultural practices or deforestation. The vegetation indices, which condense data in a quantitative numeric manner, have been used to estimate several forest parameters, such as the volume, basal area and above ground biomass. The objective of this study was the development of allometric functions to estimate above ground biomass using vegetation indices as independent variables. The vegetation indices used were the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Simple Ratio (SR) and Soil-Adjusted Vegetation Index (SAVI). QuickBird satellite data, with 0.70 m of spatial resolution, was orthorectified, geometrically and atmospheric corrected, and the digital number were converted to top of atmosphere reflectance (ToA). Forest inventory data and published allometric functions at tree level were used to estimate above ground biomass per plot. Linear functions were fitted for the monospecies and multispecies stands of two evergreen oaks (Quercus suber and Quercus rotundifolia) in multiple use systems, montados. The allometric above ground biomass functions were fitted considering the mean and the median of each vegetation index per grid as independent variable. Species composition as a dummy variable was also considered as an independent variable. The linear functions with better performance are those with mean NDVI or mean SR as independent variable. Noteworthy is that the two better functions for monospecies cork oak stands have median NDVI or median SR as independent variable. When species composition dummy variables are included in the function (with stepwise regression) the best model has median NDVI as independent variable. The vegetation indices with the worse model performance were EVI and SAVI.
Resumo:
Como corolário de vários estudos geobotânicos realizados, no sudoeste Ibérico, no âmbito do seminário internacional Gestão e Conservação da Biodiversidade VIII, apresentou-se uma conferência sobre as principais séries de vegetação prioritárias para a conservação no centro e sul de Portugal continental. Assim, neste trabalho, após uma breve introdução apresenta-se uma súmula da caracterização biofísica deste território e um conjunto de séries singulares destas superfícies. Assim, selecionaram-se as séries de vegetação potencial climatófilas, edafoxerófilas e edafo-higrófilas que possuem, do ponto de vista corológico ou florístico, maior originalidade. Dentro destas, com elevado valor conservacionista, destacam-se quatro séries de sobreirais de Quercus suber, seis carvalhais de folha marcescente (três de Quercus broteroi, uma de Quercus canariensis, uma de Quercus marianaica e uma de Quercus pyrenaica), seis de zimbrais (quatro de Juniperus turbinata, uma de Juniperus navicularis e uma de Juniperus oxycedrus subsp. lagunae), um carrascal arbóreo (Quercus rivasmartinezii), um zambujal (Olea europaea var. sylvestris), um salgueiral (Salix salviifolia subsp. australis) e duas comunidades arborescentes de cursos de água torrenciais (Nerium oleander e Flueggea tinctoria). Porém, algumas destas séries encerram o seu volar, particularmente nas suas etapas seriais, essencialmente devido à presença de plantas endémicas e/ou com estatuto de proteção legal. Neste sentido, salienta-se ainda ao nível da série, a sinecologia, a sincorologia e a sinestrutura. Contudo, a revisão da dinâmica serial e os trabalhos de campo efectuados recentemente, permitiram a identificação de uma nova associação vegetal descrita no presente trabalho, no âmbito das séries de Aro neglecti-Querco suberis sigmetum. Finalmente expõem-se alguns dados relativos ao estado de conservação das etapas seriais mais próximas do clímax, apresentando-se sugestões que visam a recuperação e valorização destes habitats boscosos, tendo em vista a criação e consolidação de uma estratégia nacional de conservação.
Resumo:
Cork oak tree (Quercus suber L.), in Portugal, is considered the national tree and have special demands and legal protection when dealing with silviculture management (pruning, debarking, thinning). Being a species of slow growth, cork oak transplanting procedures can be a valuable asset either from the economic or ecological rationales to relocate trees, re-populate areas affected by high tree mortality, increase tree density to control erosion on montado ecosystems or landscape design. This study focuses the impacts and physiological responses of ten juvenile rain fed cork oak trees (with diameter at breast height between 6 and 16cm), when subjected to transplant operations. The work was conducted in a cork oak woodland experimental plot at the campus of the University of Évora (SW Portugal), during the year of 2015. Tree’s transplants were performed with a truck-mounted hydraulic spade transplanter coupled with a proposed methodology to maximize tree survival rates, addressing techniques to limit canopy transpiration and to improve root systems prior to transplant. Tree ecophysiological indicators (sap flow, leaf water potentials and stomatal conductance) were monitored comprising the periods before and after transplant operations, and water stress avoidance practices were established to promote post-transplant tree status recovery, including irrigation to match average daily accumulated sap flow. Transplant operations were considered successful when the tree's water uptake inferred from sap flow exhibited a high correlation with solar radiation and returned to its undisturbed or pre-transplant water potential gradients in the following 2 to 3 weeks. The post-transplant tree nourishment follow up included permanent sap flow measurements and identified the time elapsed after transplantation from which the tree recovers its normal transpiration thresholds and response. Our results suggest that by following the proposed methodology the sampled cork oak trees exhibited a transplant success rate of 90%.
Resumo:
The effects of climate change can result in dramatic consequences in specific ecosystems such as montados that are seriously threatened by the absence of cork and holm oak (Quercus suber and Q. rotundifolia) natural regeneration. Shrubs of the genus Cistus, which are among the most important elements of encroached montados, seem to promote soil rehabilitation and enhance oak regeneration (Simões et al. 2009). In this context, we compared the life strategies and evaluated the potential ability of Cistus species to adapt to the increasing drought expected for the Mediterranean region, and thus their role on the sustainability of cork oak montados.
Resumo:
The world distribution of cork oak Quercus suber and holm oak Q. rotundifolia is basically restricted to the western Mediterranean basin. These two evergreen oaks are the base of the Portuguese montado and the Spanish dehesa. This thesis aims to analyse how bird communities of the montado are influenced by management practices. We used different approaches to study this relationship, and to evaluate which features are responsible for species distribution in different typologies of montado. First, we reviewed the concept of montado in order to better understand the system and to set thresholds on what can be considered as montado. Afterwards, we studied the elements that promote higher species diversity and individual species, or group of species, that can act as indicators of High Nature Value for montados. Finally, we evaluated how the bird communities are structured, and the influence of the main management actions (e.g. cattle and cork exploitation) on those communities; Resumo: A distribuição mundial do sobreiro Quercus suber e da azinheira Quercus rotundifolia é praticamente restrita à bacia do Mediterrâneo. Estas duas espécies de carvalhos são a base dos montados em Portugal e das dehesas em Espanha. No âmbito desta tese analisamos como as comunidades de aves do montado são influenciadas pela gestão florestal. Para este efeito usámos diferentes abordagens e avaliámos quais as características do montado responsáveis pela distribuição das espécies ao longo das suas diferentes tipologias. Fizemos uma revisão do conceito de montado e proposemos uma definição para o sistema, englobando a sua multifuncionalidade. Estudámos os elementos singulares que promovem a diversidade de aves e que podem ser simultaneamente indicadores de áreas de Alto Valor Natural (HNV). Por fim, avaliámos qual a influência da gestão (p. ex. pastoreio e descortiçamento) na estruturação das comunidades de aves.
Resumo:
En estudios anteriores propusimos un nuevo método para el estudio del género Quercus (Musarella et al., 2013), baseado en la dimensión fractal (DF). En este trabajo analizamos la DF del género Quercus en el sur de Italia, para ello utilizamos hojas de árboles pertenecientes a Q. robur subsp. brutia, Q. cerris, Q. congesta, Q. crenata, Q. ilex, Q. suber, Q. virginiana. De cada árbol se toman hojas de cada uno de los puntos cardinales para complejiada de la estructura morfológica de las hojas. Este análisis extrae información sobre los caracteres fenotípicos de las hojas utilizadas, tales como el número y morfologia de los nervios, ángulos nervios secundarios con principal, contorno de hojas, aspecto reticulado de la hoja etc. En nuestro análisis, no se han detectado diferencias significativas entre la DF en cada una de la orientaciones y la DF global para cada una de las especies. En este trabajo corroboramos estudios anteriores realizados por los autores, en los que se proponía una DF < 1,6 para Quercus esclerófilos y DF entre dos especies sea cero o su cociente sea uno, el grado de parentesco entre las dos especies es del 100%; DFA - DFB = 0; DFA/DFB = 1, la especie Ay B son iguales; por ello cuanto menor es la diferencia o bien cuanto más se acerque el cociente a 1, mayor es la semejanza entre las especies. Si este cociente tiene un valor alejado de 1 como ocurre entre vfvi/vfsu>2, las especies Q. virginiana y Q. suber están muy distantes entre sí. Además, la realización del Test de Rango Múltiple, que es un procedimiento de comparación para determinar cuáles medias son significativamente diferentes unas de otras, confirma los resultados obtenidos de la forma anteriormente expuesta. Conto et al. (2007) ponen de manifiesto el origen hibridógeno de Q. crenata, y según el análisis molecular existe una mayor similitud genética entre Q. crenata y Q. cerris, que entre Q. crenata y Q. suber. Los DF de Q. crenata 1,868; Q. cerris 1,677 y Q. suber 0,932; siendo DFQsu 0,745 y DFQsu = 1,8, lo que significa que existe gran diferencia fenotípica (genética) entre los parentales, se presenta una mayor semejanza entre Q. crenata y Q. cerris que entre Q. crenata y Q. suber, ya que la diferencia DFQcr-DFQce = 0,191 y DFQcr/DFQce = 1,1, por lo que tienen un fuerte grado de semejanza, mientras que DFQcr-DFQsu = 0,936 y DFQcr/DFQsu > 2, lo que pone de manifiesto las fuertes diferencias fenotípicas entre el híbrido y el parental.