T. Zagas

Root morphology, stem growth and field performance of seedlings of two Mediterranean evergreen oak species raised in different container types

Outplanting container-grown oak seedlings with undesirable shoot and root characteristics result in poor establishment and reduced field growth. The objective of this study was to determine the influence of container type on both above-and below-ground nursery growth and field performance of one-year old tap-rooted seedlings Quercus ilex L. and Quercus coccifera L. The experiment was conducted in an open-air nursery and the seedlings were grown in three container types. At the end of the nursery, growth period seedlings’ shoot height, diameter (5 mm above root collar), shoot and root biomass, root surface area, root volume and total root length were assessed. Then the seedlings were planted in the field and their survival and growth were recorded for two growing seasons after outplanting. The results showed a difference between the Quercus species in the effect of container type. Q. ilex seedlings raised in paper-pot had significantly greater height, diameter, shoot and root biomass and root volume than those raised in the other two container types. Similarly, Q. coccifera seedlings raised in paper-pot, had significantly greater above-and below-ground growth than those raised in the other two container types. Both oak species showed relatively low survival in the field; the mortality was mainly observed the first year after outplanting, especially after the summer dry period. However, 2 years after outplanting, the paper-pot seedlings of the two oak species showed better field performance.

A comparison of root architecture and shoot morphology between naturally regenerated and container-grown seedlings of Quercus ilex

We explored the different mechanisms developed by naturally regenerated seedlings of Quercus ilex L. (Holm oak) under Mediterranean conditions compared to container-seedlings commonly used in plantations. We examined the differences in root architecture (including topology and morphology) and shoot parameters. The results showed that there are many differences in the architecture of the root system as well as in the shoot morphology between the two types of seedlings. The naturally regenerated seedlings were smaller with regard to most of the shoot and root parameters, but they developed a longer taproot, only first order lateral roots, and presented a more herringbone-like root system compared to the container seedlings. Conversely, all types of container seedlings, were larger and had a more extended root system with many orders of lateral roots, while their taproot length was restricted within the container’s depth. The quotient log (α)/ log (μ) for all seedlings, showed a tendency to decrease with plant size. A strict herringbone root system with an elongated taproot may be the optimal root architecture for Quercus ilex L. seedlings in order to survive under Mediterranean conditions.

Dynamics of postfire regeneration of Pinus brutia Ten. in an artificial forest ecosystem of northern Greece

This paper deals with the dynamics of postfire regeneration of Pinus brutia Ten. in an artificial forest ecosystem of North Greece, after a fire in 1982. The following issues are studied: the natural development of P. brutia stands 20 years after the fire, the current stand structure, and the influence of thinning treatment on stand population dynamics and tree growth patterns. The present work summarises and updates data taken during the years 1987–2002. The results show that the postfire regeneration was successful and contributed to the re-establishment of the pre-fire forest not only at the sites of good quality but at the medium quality sites as well. Regarding the postfire development, it is observed that an abundant P. brutia re-establishment is followed by a natural and gradual reduction of tree population caused by the influence of the physical environment during the early postfire years and caused by self-thinning later. The stands have entered the stem exclusion stage and they are growing at a narrow spacing in all cases. The evolution pattern and the stand structure were affected by thinning, which resulted in the improvement of tree quality and growth and accelerated their early fruition, thus contributing to higher ecosystem resilience.

Post-fire regeneration of Pinus halepensis Mill. stands in the Sithonia peninsula, northern Greece

This paper deals with the post-fire regeneration of Pinus halepensis Mill. ecosystems in the Sithonia peninsula in northern Greece. The pre-burning stands consisted of two storeys; the overstorey of the dominant tree species P. halepensis and the understorey of evergreen sclerophyllous shrubs. The wildfire took place in June 1994. Three months after the fire two experimental plots of 0.75 ha each were established on a northeastern and a southwestern facing slope. In each experimental plot different restoration treatments were applied by using P. halepensis reproductive material. The treatments were the following: (i) planting of paper- pot seedlings, (ii) planting of bare-root seedlings, (iii) seeding in patches, (iv) seeding in strips, (v) seeding in strips and lines. The results of these treatments were compared to the control (no treatment applied). The results showed that all applied restoration works accelerated the rate of regeneration, while the best results were obtained by the method of planting paper-pot seedlings.

Spatial limitations in forest biomass harvesting using Geographic Information System and Remote Sensing for an ecological and sustainable bioenergy framework

ABSTRACT As the sustainable forest biomass harvesting process is highly influenced by the terrain, the heterogeneity, and the protection status of the landscape, this study highlights the GIS and Remote Sensing as important scientific tools, assisting in the planning process and integrating the appropriate spatial limitations for an ecological forest biomass extraction in a rational bioenergy utilization framework. This study is focused on the northwest Greece and particularly in the regional unit of Grevena which is part of the Western Macedonia region, the region with the highest unemployment rates in Greece. As the forests in the regional unit of Grevena occupy a significant percentage over half of the regional unit area, the emphasis on the sustainable harvesting and utilization of forest biomass for energy purposes could tackle unemployment rates, enhance the energy autonomy of the remote mountain villages, and reduce the Mediterranean forest fire risk. The spatial data process and the implied spatial limitations unfold a methodology procedure, which is revealing specifically quantified and illustrated results as are emerging progressively the oak forests of the regional unit of Grevena with biomass harvesting capabilities, which do not belong to the Grevena’s protected areas, have accessible slopes and lower diversity index.