6,578 research outputs found

    Impact of soil management on the functional activity of microbial communities associated to cork oak rhizosphere

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    The microbial ecology of cork oak rhizosphere was investigated using the Biolog community level physiological profile (CLPP) that provides a unique metabolic fingerprint helpful for the characterization of complex microbial communities. Microbial populations from the rhizosphere of cork oak plants growing at three different sites within the same area were characterized using CLPP and compared. The sites were distinguished by a different soil management under the tree cover and, in general terms, by a different anthropogenic impact. The comparison of metabolic fingerprints of the different microbial populations showed the existence of a relationship between general microbial activity and functional biodiversity in the rhizosphere and the level of anthropogenic impact. Particularly the presence of grazing animals, soil tillage and fire could be identified as the main factors affecting both the general microbial activity and the structure of microbial populations from cork oak rhizospheres

    Forty-four years of land use changes in a Sardinian cork oak agro-silvopastoral system: a qualitative analysis

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    The island of Sardinia is the biggest producer of natural cork in Italy. In this study, cork oak cover change is investigated in a typical agro-silvopastoral system where the main activities are cereal fodder and wheat cultivation, sheep rearing and cork exploitation. The research method is based on the comparison of two land use maps produced by photo-interpretation of digitised aerial photographs taken in 1954 and 1998, combined with interviews with local farmers, field surveys, and data collected from literature, administrative documentation and decadal censuses (at council level). The results show that the cork oak woodland surface decreased (-29%). It was substituted by other forest, ploughed land, and mixed grassland and shrubland. Apart from the transformation of the cork oak woodland to other forest, other changes have happened probably because of an increase in agricultural and pastoral activities as described by the documental material available for the same area

    An approach to cork oak forest management planning: a case study in southwestern Portugal

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    This paper presents results of research aiming at the development of tools that may enhance cork oak (Quercus suber L.) forest management planning. Specifically, it proposes an hierarchical approach that encompasses the spatial classification of a cork oak forest and the temporal scheduling of cork harvests. The use of both geographical information systems and operations research techniques is addressed. Emphasis is on the achievement of cork even flow objectives. Results from an application to a case study in the Charneca Plioce¬īnica of Ribatejo in southern Portugal encompassing a cork oak forest extending over 4.8 thousand ha are discussed. They suggest that the proposed approach is capable of effective spatial classification of cork oak management units. They further suggest that it may be used to select optimal cork even flow scheduling strategies. Results also show that the proposed approach may lead to a substantial increase in net present value when compared to traditional approaches to cork oak forest management planning

    Landscape dynamics in endangered corkoak woodlands in Southwestern Portugal (1958-2005)

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    Cork oak landscape dynamics were assessed over a 47-year period (1958‚Äď2005) in an endangered region of southwest Portugal using a GIS approach. The area of cork oak woodlands was maintained during this period, but shifts due to land abandonment were evident leading to transformation of cork oak agriculture areas into woodlands and of cork oak woodlands into shrublands (average yearly change rates of 0.6 and 0.1%, respectively). The multi-temporal landscape analyses showed that expansion and regression rates of cork oak forests were similar (15 and 16 ha year-1, respectively). The main factor determining oak woodlands expansion and regression was related to land-use changes, but slope, aspect and soil type were also significant factors. The substitution of agriculture lands and oak woodlands by shrublands has a determining role in periods of disturbance and recovery of these Mediterranean ecosystem

    Oak Persistence in Mediterranean Landscapes: The Combined Role of Management, Topography, and Wildfires

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    Mediterranean ecosystems have been shaped by a history of human and ecological disturbances. Understanding the dynamics of these social-ecological systems requires an understanding of how human and ecological factors interact. In this study, we assess the combined role of management practices and biophysical variables, i.e., wildfire and topography, to explain patterns of tree persistence in a cork oak (Quercus suber L.) landscape of southern Portugal. We used face-to-face interviews with landowners to identify the management practices and the incentives that motivated them. We used aerial photographs and a Geographic Information System (GIS) to classify vegetation patch-type transitions over a period of 45 years (1958-2002) and logistic regression to explain such changes based on management and biophysical factors. The best model explaining vegetation transitions leading to cork oak persistence in the landscape included both biophysical and management variables. Tree persistence was more likely to occur on steeper slopes, in the absence of wildfires, and in the absence of understory management. We identified ecological, ideological, and economical barriers that preclude oak persistence and that are important to consider in implementing efficient environmental policies for adequate conservation and reforestation programs of Mediterranean cork oak landscape

    Incorporating landscape character in cork oak forest expansion in Sardinia: constraint or opportunity?

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    Cork oak (Quercus suber) is a declining woodland species across the island of Sardinia, despite its former economic importance for wine production and its significance for biodiversity. In particular, cork oak forests (COFs) on the island have seen a 29% decrease in the past 45 years. A spatial GIS model was developed to determine suitability for the expansion of cork oak forests on the island. The model uses a set of simple spatial decision rules based on principles of landscape ecology and expert opinion to assign a suitability score for pure cork oak forests to every land use parcel in Sardinia. These rules include the type of existing land parcel, its size, distance to existing cork oak forest, and the area of seminatural habitats in its neighborhood. This was coupled with a map of landscape types to assist with the development of policy for the protection of cork oak forests across Sardinia. The results show that there is an area of 116,785 ha potentially suitable for cork oak forest expansion in Sardinia, with the largest area of potential habitat on granitic mountains. There is a substantial overall agreement (Cohen’s kappa = 0.61) between the suitability map produced and the historical reference map. The model is flexible and can be rerun to reflect changes in policy relating to agri-environmental targets for habitats and species

    Soil Microbial Biomass And Activity In A Cork Oak Savanna

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    Cork oak savannas are composed by a sparse tree canopy (30-70 trees/ha) and a grassland understory predominantly composed of C3 annuals that survive the hot and dry Mediterranean summers as seeds in the soil. Microbial communities can be more or less efficient at converting organic substrates into microbial biomass carbon depending on the quantity and quality of organic matter inputs. The cork oak savannas have two distinct types of plant litter that can affect soil microbial biomass and activity differently: herbaceous litter and the more recalcitrant woody plant litter resulting from the trees. Spatial variability of soil microbial biomass and activity due to the tree-grassland component of cork oak savannas were evaluated in order to better understand the soil carbon dynamics of these systems.

To quantify changes in soil microbial biomass and activity, measurements were performed in a Cork oak savanna in Southern Portugal. At this site 8 plots were randomly established under mature cork oak trees and paired with 8 open grassland plots. During one year soil cores (0-10 cm) were monthly collected at each site for measuring soil microbial biomass C and other eco-physiology parameters.


Soil microbial biomass carbon (Cmic) and nitrogen (Nmic) were always higher under the tree canopy than in the open grasslands. Organic carbon (Corg) was also higher under the tree canopies. The Cmic/Corg ratio relates to the microbial activity and its potential to mineralize organic substances. The Cmic/Corg ratio was lower under the tree canopies than in the open grasslands. Less microbial biomass was supported per unit of Corg. Basal activity was always higher under the canopy than in the open grassland.

Trees scattered in the savanna function as islands inducing larger soil microbial communities and higher basal activity under the canopies. Lower Cmic/Corg ratio under the tree canopies suggests a more recalcitrant nature of the litter and a decrease in relative availability of organic matter under the trees.

    Climatic impacts on the bacterial community profiles of cork oak soils

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    Climate changes comprise increasing global temperature and water cycle deregulation (precipitation storms and long dry seasons). Many affected ecosystems are located within the Mediterranean basin, where cork oak (Quercus suber L.) is one of the most important forest ecosystems. Despite cork oak tolerance to drought, the decrease of water availability and increase of temperature is causing a serious decline of cork oak populations. In the present work, the bacterial community of cork oak soils was assessed by metabarcoding using Illumina Miseq. Soils from seven independent cork oak forests were collected along a climate gradient. In all forest soils, Proteobacteria and Actinobacteria were the richest and more abundant bacteria. Acidobacteria also presented a high relative abundance, and Chloroflexi was a rich phylum. The soil bacterial community diversity and composition was strongly affected by the climatic region where cork oak resides and specific bacterial taxa were differently affected by precipitation and temperature. Accordingly, cork oak bacterial communities clustered into three distinct groups, related with humid, sub-humid and arid/semi-arid climates. Driest and warmer forests presented more diverse bacterial communities than humid and coolest forests. However, driest climates presented more homogenous bacterial communities among forests than humid climates. Climate (mainly precipitation) revealed to be the strongest driver leading to significant variations of bacterial community profiles. The most impacted bacterial taxa by climatic variables were Proteobacteria, in particular Gammaproteobacteria and Deltaproteobacteria, Chloroflexi, and Firmicutes. Humid forests presented mainly Acidobacteria as good indicators of climate, whereas Actinobacteria members were better indicators for arid forests (mainly Gaiellales and Frankiales). Some indicator species for different climate conditions were members of the bacterial core of cork oak stands (7% of the total bacterial community). Taken together, differentThis work was supported by FEDER through the Operational Competitiveness Program (COMPETE) and by Portuguese national funds through the Foundation for Science and Technology (FCT) within the scope of the project POCI-01-0145-FEDER-028635; FCT/MCTES/PIDDAC (Portugal) under the project (PEst-OE/BIA/UI4046/2014; UID/MULTI/04046/2013) and PhD grant to F.R. (SFRH/BD/86519/2012)

    Regeneration patterns of Quercus suber according to montado management systems

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    Traditional management of montado (dehesa) is an example of integration of sustainable land-use and biodiversity conservation. The whole system sustainability is currently threatened by the intensification of soil tilling to control shrub invasion and promote pastureland, the absence of tree natural regeneration being one of the most outstanding threats. A study to assess effects of management on tree regeneration at early stages was developed in a cork oak montado grazed by cattle, in southern Portugal. We specifically compared the effects of harrowing every 3‚Äď4 years with those of shrub clearing with a shredder every 5‚Äď7 years. We hypothesized that extending shrub maintenance may facilitate cork oak regeneration at early stages in grazed montado. Fenced cork oak paddocks under the same management system for at least the last 40 years were surveyed for cork oak seedling, juvenile and sapling density; shrub cover percentage was also estimated. Recruitment bottleneck was observed after the seedling stage under harrowing, while in shredded areas all stages were well represented and often associated with shrub patches. Overall, the highest cork oak recruitment occurred at intermediate shrub cover (40‚Äď60 %). By maintaining shrub patches and their protective effect against direct radiation and grazing impact, while preventing shrub encroachment, shredding every 7 years seems to create an important temporal window for effective oak regeneration. This management practice might thus be suitable to favour successful tree regeneration in grazed cork oak montado, assuring the persistence of this system
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