This study is the beginning of the first long-term study on cork oak irrigation under field conditions, with a structural-functional approach. Cork oaks are currently facing disturbances affecting ...cork quality and quantity, jeopardizing the future of the economic sector. There is a need for new production techniques that maximize cork oak growth and vitality. In this study, irrigation was implemented in a new intensive cork oak plantations to test the best irrigation volume. The long-term goal is to improve tree growth with minimum water requirements. A 6 ha intensive plantation was installed in Coruche, Portugal. The experimental plot consisted of a subsurface drip fertigation system, buried 40 cm deep; with five independent irrigation treatments. It was tested four irrigation volumes during the dry period—21 weeks in the summer of 2016—ranging from 1.88 mm to 5.62 mm a week. Information on meteorological conditions, soil moisture profile and leaf stomatal conductance were gathered periodically and dendrometric measurements were performed before and after the treatments. Cork oaks’ structural and functional parameters were associated with irrigation volume Response to irrigation showed an inflection point in treatment 2, corresponding to a water supply of 3.12 mm per week: below the inflection point, stomatal conductance was reduced by 15% and relative diameter growth at the base was reduced by 10%. Stomatal conductance also showed a positive relationship with soil moisture below the irrigation tubes and with plants’ stem diameter. In conclusion, irrigation supply during the period of water stress improved function and structure of cork oaks seedlings under field conditions. These results suggest that irrigation can be a viable alternative to improve cork oak growth in afforestation and reforestation.
Soil compaction promoted either by inadequate management (pressure of livestock and machinery) or by soil natural conditions (podzolisation) can influence the growth of cork oak seedlings. We ...hypothesized that compaction could be related with the lack of natural regeneration and decline on cork oak stands. In this paper, we evaluated the response of cork oak seedlings growth in terms of area and biomass production for above and belowground parts at different compaction depths tested for a sandy-loam soil. This study was done in a greenhouse, with germinated seedlings. Three treatments were applied. One no-compaction treatment (control, C0) and two with a soil compacted layer at 60 cm (C1) and 30 cm depth (C2). The level of compacted layer was 1.37 MPa of mechanical resistance. Results show that tap root length is negatively affected by compaction at 60 and 30 cm depth. Below and aboveground biomass are affected by compaction at 30 cm depth. In addition, the leaf area results demonstrate that compaction is a sensitive factor for this parameter. In this 1-year stage, plants spend more energy in roots production. Due to soil formation and bad management of cork oak stands, soil compaction at depth could be a cause for the observed lack of natural regeneration, affecting the growth at earlier stages and probably for the decline of cork oak populations.
Widespread events of cork oak mortality are disturbing the system and jeopardizing cork production. This research combined techniques to analyze in detail these events on a small scale. To understand ...the dynamics of cork oak mortality and the factors associated with it, a diachronic study was performed in two farms located in Évora, Portugal. The case studies were two nearby farms suffering from tree dieback since 2000. Aerial images of the area, taken in 2004 and 2012, were processed with GIS in order to detect dead trees and to calculate tree crown cover. Slope and aspect were obtained through cartographic and topographic maps. The intersection of those maps resulted in polygons with unique values for those characteristics. Mortality index and tree crown cover were calculated for each one of them. Maps of the kernel density of tree mortality were generated to select key spots for pests and diseases field survey. Detection of soil pathogens was performed using baiting method and molecular analyses. The analysis showed that both farms had the same predisposing and inciting factors associated with tree decline, such as the soilborne Phytophthora cinnamomi, sunlight exposure or soil disking. However, the relative importance of each factor varied among farms. As a result, the dieback processes also differed, despite their similarity regarding mortality intensity. The diachronic approach associated with field survey resulted in a better comprehension of the tree dieback on a small scale and proved its usefulness in future decision-making regarding tree mortality mitigation.
Widespread events of cork oak mortality are disturbing the system and jeopardizing cork production. This research combined techniques to analyze in detail these events on a small scale. To understand ...the dynamics of cork oak mortality and the factors associated with it, a diachronic study was performed in two farms located in Évora, Portugal. The case studies were two nearby farms suffering from tree dieback since 2000. Aerial images of the area, taken in 2004 and 2012, were processed with GIS in order to detect dead trees and to calculate tree crown cover. Slope and aspect were obtained through cartographic and topographic maps. The intersection of those maps resulted in polygons with unique values for those characteristics. Mortality index and tree crown cover were calculated for each one of them. Maps of the kernel density of tree mortality were generated to select key spots for pests and diseases field survey. Detection of soil pathogens was performed using baiting method and molecular analyses. The analysis showed that both farms had the same predisposing and inciting factors associated with tree decline, such as the soilborne Phytophthora cinnamomi, sunlight exposure or soil disking. However, the relative importance of each factor varied among farms. As a result, the dieback processes also differed, despite their similarity regarding mortality intensity. The diachronic approach associated with field survey resulted in a better comprehension of the tree dieback on a small scale and proved its usefulness in future decision-making regarding tree mortality mitigation.
The last decades have witnessed the decline and sudden death of the cork oak (Quercus suber L.) in Montado. The complexity of this production system management has lead to a large set of solutions ...which have been absent by scientific based research findings (such as those related with the cork oak root system) deriving mainly from empirical knowledge application. The present integrated research approach permits a better understanding of the production system vulnerabilities that can result in management modification proposals which will be useful in a near future. To contribute to a more realistic and integrated forest management and planning, a study relying on a morphological evaluation of cork oak root system in a Cambissoil soil, using a 3D digitizing method was performed. Cork oak showed a dimorphic root system with a relative high quantity of sinkers distributed all over the soil profile, one root subsystem at a superficial level until 40 cm depth and another at a deeper level, around 1.20 m depth. Tree biomass allocation was similarly distributed between aerial and root systems. Previously, a study on methodologies for roots excavation - profile washing with water and excavation through high pressure air jet – was carried out. Results showed that for sandy soils the most suitable method is the excavation by high pressure air jet. Both methods showed to be inadequate for clayed soils. Following the evidence that soil compaction could be an important factor for root growth, a study was conducted, in a greenhouse, with cork oak seedlings. Results showed that tap root length and total root biomass (coarse and fine roots) are negatively affected by soil compaction in depth. In regard to the low survival rate of cork oaks regeneration that has been observed in Montado, another complementary study was conducted in a greenhouse where fertilisation, inoculation with mycorrhizal fungi and aminoacids supply were tested. It was concluded that seedlings subjected to fertilisation and inoculation had a more equilibrated growth between shoot and root components. It is expected that the research developed in the present thesis can provide an essential tool for future forest planning and management and for the natural and artificial regeneration processes in cork oak stands, ensuring the maintenance of the typical Montado landscape.
The fine roots are considered the key organs for plant survival, growth and productivity. Measurement of fine roots variables is easily and conveniently achieved by means of digital image. The ...descriptive variables like root area, surface, total length and diameter distribution may be obtained from the image. Analysis of digital image consists from several steps, each of them represents potential source of the error. In this article we want to evaluate the automatic thresholding and its impact on principal variables obtainable from digital scans of the fine roots. We compare 16 different thresholding methods and compare them with the human processed binary images of roots of cork oak (Quercus suber L.). We found some of the thresholding methods perform significantly better than others in the estimation of total projected area however the length estimation error points out a little different order of accuracy
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