Understory clearing in open grazed mediterranean oak forests: assessing the impact on vegetation

Over recent years, rural abandonment and climate change have challenged grazed wooded landscapes in Mediterranean mountain regions. Fire hazard management procedures such as grazing, prescribed burning, or mechanical clearing must be adjusted to the new socioeconomic and environmental situation and according to the context and circumstances of each territory. This study contributes to adjusting vegetation management techniques in response to low grazing pressure by evaluating the combined effect of mechanical clearing and grazing on the structural and floristic dynamics of understory vegetation in the open-grazed Mediterranean oak forests of northern Portugal. To this end, three treatments were established: mechanical clearing with grazing, mechanical clearing without grazing, and grazing without clearing (the control). The floristic inventories were carried out using the point quadrat method, and the structure was evaluated using line transects. Herbaceous biomass was determined by destructive methods. This study shows that mechanical vegetation clearing effectively reduces phytovolume and, thus, fire hazards. However, for its effects to endure, it must be combined with subsequent grazing, which does not always occur. No consistent pattern was found in the floristic dynamics of the shrub-grassland mosaic (species richness and diversity) related to shrub-clearing or grazing over the short term (24 months)his research was funded by the EU SUDOE, grant number SOE2/P5E0804, project OPEN2PRESERVE. This article was also supported by the FCT/MCTES Project CIMO (UIDB/00690/2020).info:eu-repo/semantics/publishedVersio

Landscape changes and carbon sequestration in the Deilão Parish, Northeastern Portugal

Estimaram-se estoques de carbono ao nível da paisagem ao longo dos últimos 48 anos na freguesia de Deilão (4.197 ha), Distrito de Bragança, Nordeste de Portugal, com o objectivo de analisar a dinâmica do carbono sequestrado numa paisagem em transformação. Construíram-se cartas de uso do solo com base em coberturas aerofotográficas de 1958, 1968, 1980, 1992 e 2006. A classificação do uso do solo foi baseada no sistema COS2005 (Instituto Geográfico Português), sendo a estrutura da paisagem descrita por métricas da paisagem. A biomassa viva e a folhada, bem como os estoques de carbono foram estimados com base em equações de biomassa e carbono e em dados de inventários. A freguesia de Deilão apresentava sinais de abandono, com redução da área agrícola e aumento da área florestal. O carbono sequestrado aumentou de 20.572 tC em 1958 para 75.449 tC em 2006, alteração essa que corresponde a um incremento de 267% durante o período de tempo considerado. Corresponde também a uma taxa média anual de sequestro de 0,27 tC/ha/ano à escala da paisagem. As alterações recentes da paisagem na freguesia de Deilão são acompanhadas pelo aumento muito significativo do carbono fixado na paisagem

Landscape change in a mountainous area in Northeastern Portugal: implications for management

In this paper we analyzed changes in landscape composition and structure over the 1958-2005 period in the França parish (Bragança, northeastern Portugal). Agriculture decreased from 22% to 5% of the area of study. Forests and shrublands became the dominant land uses occupying together 73% of the area of study in 2005. Structurally the landscape became more homogeneous. We speculate that the types of change observed and the tendency for their magnification in the near future will have functional effects on this landscape, namely the creation of condition for the occurrence of catastrophic disturbance events such as wildfires

Development of a methodology for the assessment of sweet chestnut orchards dynamics in Northeastern Portugal with remote sensing and geostatistics

The sweet chestnut productive area in Portugal has augmented in the last decades due to EU and Portuguese government funding schemes and favorable international market for the chestnut fruit. Farmers have been encouraged to replace traditional crops by chestnut plantations. A rising demand for sweet chestnut (Castanea sativa) in Portugal and elsewhere in the world has led to more intensive management practices in order to increase nut production. This intensification has contributed to the decline of sweet chestnut orchards as a result of the widespread of ink disease (Phytophthora cinnamomi) and chestnut blight (Cryphonectria parasitica) which have caused important losses in chestnut production as well as limited the establishment of new planted areas. The balance between mortality and the establishment of new plantations is difficult to quantify based on field observations only because often new plantations are placed where chestnut mortality occurred. However, changes in chestnut orchards are registered in remotely sensed data collected over time that can be used to reconstruct regional and local history of this and other land use classes. Time Series Analysis (TSA) and Geostatistical analyses can be combined with analogical conventional aerial photographs (CAP) and modern digital orthophotographs using photogrammetric techniques and Geographical Information Systems (GIS). In this work we developed a methodology integrating the tools above to estimate chestnut decline for the last twenty years (1986-2006) in the Trás-os-Montes region (Northeastern Portugal). We used aerial photography from 1986, 1995, and 2006 to map chestnut occupation and to quantify tree damage according to a categorical scale at the tree level within fixed sample plots. Decline surfaces were created by Kriging interpolation in a GIS based on the spherical model which provided the lowest Mean Absolute Errors by an iterative process in the variography analysis. The results showed an expansion of total chestnut orchards in the study area from 1742 ha (14.3% of the area) in 1986 to 2562 ha (21.1%) in 2006 although chestnut mortality affected 1061 ha during the same period. More importantly, the results of the methodology developed here, showed the distribution and configuration of turnover areas and their spatial relationship with the degree of chestnut decline which can support the decision making process relative to sweet chestnut plantations establishment and management

Temporal analysis of sweet chestnut decline in northeastern Portugal using geostatistical tools

The rising demand for sweet chestnut (Castanea sativa) in Portugal and elsewhere in Europe has led to more intensive management practices to increase nut production. This intensification has potentially increased the widespread of ink and chestnut blight diseases, causing decline in sweet chestnut orchards health and production and limiting the establishment of new planted areas. In this study we estimated chestnut decline along the last twenty years (1986 to 2006) in the northern part of Portugal using 1986, 1995 and 2006 aerial photography to quantify the damage at the tree level within fixed sample plots according to a categorical scale. Mean damage and damage variance in each date, however, were not significantly different. Geostatistical analyses indicated, however, changes in the spatial distribution of damaged and undamaged areas over time. The spread of decline in the region of study was estimated using Kriging based on the spherical model. During the examined period we observed spread of chestnut decline and increasing damage levels in regions where damage is systematically high. The chestnut productive surface in the region has increased in the last twenty years because new plantations exceeded mortality areas. The spatial analyses applied here have made clearer the relations between the spread of chestnut decline and geographical variables

Potential greenhouse gas emissions mitigation through increased grazing pressure: a case study in North Portugal

Wildfires have been an important process affecting forests and rangelands worldwide. In the Mediterranean region, wildfires burn about half a million hectares of forest and scrubland every year. Fuel loads are the main factor controlling fire risk and its propagation. The reduction of fuel loads by grazing could help to decrease the spread and intensity of wildfires in this region. This study aims to assess the contribution of sheep grazing on fuel load management and their role to the mitigation of wildfire greenhouse gas (GHG) emissions. The methodological approach is based on a simulation of the grazing pressure required to reduce a given quantity of fuel, under the assumption that if it is not consumed, it becomes fuel. Following, a simulation model was designed to estimate the total GHG emissions prevented through grazing, by reducing the risk of fire. These emissions were estimated based on the Intergovernmental Panel on Climate Change (IPCC) framework. The accumulated fuels were estimated to be 3126.65 kg dry matter (DM) ha-1 and the biomass potentially consumed by sheep was 1416.03 kg DM ha-1 yr-1, corresponding to 45.29% of accumulated fuel loads. Our findings suggest a value of 3.88 sheep ha-1 day-1 as the ideal to reduce 4833.63 kg CO2eq ha-1 yr-1 of emissions, distributed between CO2 (-2221.76 kg CO2eq ha-1 yr-1; 45.96%), NOx (-1873.41 kg CO2eq ha-1 yr-1; 38.76%), CO (-454.55 kg CO2eq ha-1 yr-1; 9.40%), CH4 (-186.35 kg CO2eq ha-1 yr-1; 3.86%) and N2O (-97.56 kg CO2eq ha-1 yr-1; 2%). The results of this study also underline that livestock can help to mitigate climate change in areas prone to wildfires.We acknowledge partial funding for this research from the European Regional Development Fund (ERDF) through the INTERREG SUDOE Programme (SOE2/P5/E0804:Open2Preserve).info:eu-repo/semantics/publishedVersio

Sheep grazing patterns for better land management: adjusting GPS tracking protocol

Small ruminant livestock systems in northeast Portugal are an extensive activity based on daily grazing paths across the landscape. The flocks use multiple patches of multiple land cover types in different ways throughout the year. Shepherd and flock interactions determine the resting and feeding spots utilized by sheep and goats according to the biotic and abiotic conditions. Information about the herding home range is central to managing the land use and vegetation cover and optimizing sheep and goats' productivity in traditional systems. This study's main objective is to contribute to calibrate a shepherding GPS protocol to monitor sheep flocks based on fieldwork in Vimieiro (Mirandela) on a protected area of the European Natura 2000 network. We answer two farmers' and breeders' requests for using GPS collars to monitor the landscape usage by sheep: (1) How closely do collared sheep remain within the flock? (2) How do the collars perform on different logging frequencies to estimate patch occupancy? We analyzed the grazing paths based on three collars' 5-minute GPS positions from winter to summer solstices. We investigated the differences in extent, duration, and frequency data of each collar throughout the season change based on spatial regressions. Results show no significant differences among the three collars ranges. It also indicates that positions collected every 15 and 30 minutes could be adequate. It means that a flock monitoring low cost can be generalized, providing accurate information to manage the pastoral territory and increase the small ruminant's productivity.info:eu-repo/semantics/publishedVersio

Carbon mapping in Portugal forest and agroforestry systems using direct remote sensing and combine assign approaches

Reducing Emissions from Deforestation and Forest Degradation (REDD and REDD+) recommend specific approaches for quantifying and spatializing ecosystem services (ES). In the context of climate change, REDD recommends the mapping of carbon stocks and its sequestration by vegetation cover to implement more appropriate environmental management practices and policies against global warming. Forest carbon mapping is a current and important environmental tool for a better land management as successful implementation of climate change mitigation (Saatchi et al., 2011). This study presents the mapping of carbon sequestration using two different approaches.info:eu-repo/semantics/publishedVersio

Fotografias aéreas de 35,70 mm ou digitais na monitorização da doença da tinta do castanheiro

A monitorização da dispersão da doença da tinta do castanheiro (Castanea sativa), requer metodologias de avaliação de baixo custo. A Fotografia Aérea de Pequeno Formato (FAPF) é uma possibilidade válida por facilmente se poder escolher a melhor escala e sensibilidade das películas. Neste estudo utilizaram-se vários subsistemas de FAPF. Adaptaram-se as câmaras numa plataforma retráctil e ao avião Cessna 172, obtendo-se FAPF à mesma altitude no sistema digital, em películas policromadas (70 mm) e em infravermelho colorido (IVP) de 35 mm de povoamentos do Norte de Portugal. As imagens aéreas foram comparadas relativamente à descriminação de classes de estrago de castanheiros observados no campo. Os custos do equipamento, obtenção de imagens e de fotointerpretação, foram também determinados. Concluiu-se que as imagens policromadas podem ser usadas na avaliação dos estragos mas nas de IVP detecta-se melhor o início do declínio, sobretudo se sujeitas a algoritmos de processamento digital. As fotos de 70 mm superam as restantes pela maior área de terreno para o mesmo tamanho do pixel. Tendo custo inicial mais elevado este é rentabilizado a longo prazo, pelo menor custo na fotointerpretação e melhor estabilidade dos voos maior altitude