Thekla Tsitsoni

Conditions determining natural regeneration after wildfires in the Pinus halepensis (Miller, 1768) forests of Kassandra Peninsula (North Greece)

Abstract Post-fire natural regeneration in Aleppo pine (Pinus halepensis) forests of Kassandra Peninsula (North Greece) was studied. The Kassandra Peninsula is characterized by a Mediterranean-type climate with a mild sub-humid winter and a long xerothermic period. Sampling was done on 74 plots in four different areas of the peninsula. The total mean regeneration indices were satisfactory in mature stands and varied between 0.60 and 14.26; they had their lowest values at the upper position and increased descending the hillside, showing statistically significant differences. The slope was also found to be an important factor determining natural regeneration, which was best in areas with a slope of 0–50%. A recurrence of fire in one of the areas studied, 4 years after the first fire, proved to be destructive for the natural regeneration.

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.

Post-Fire Management of Serotinous Pine Forests

The current chapter describes the ecological context and post-fire management practices for the most important and fire-prone coniferous tree species in the Mediterranean Basin, the serotinous pine trees. The state of art about evolution, habitat and adaptive strategies of Pinus halepensis Mill, Pinus brutia Ten. and Pinus pinaster Aiton are included. The management of burned areas, from emergency to long-term actions, are included but also the influence of climate change and the changing fire dynamics are discussed. To illustrate it, we included some case studies for the serotinous pine species in both Eastern and Western Mediterranean Basin.

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.

The effects of vegetation on reducing traffic noise from a city ring road

This study was designed to investigate the reduction of road noise by vegetation along the ring road of Thessaloniki. Road noise was measured at two sites, one through a belt of trees and the other on a grass-covered ground. A total of 245 measurements were taken from each site over a two-month period and expressed as differences in LAeq. Also measurements of the number of vehicles per minute, the type of vehicles and analytic description of vegetation were taken at both sites. The results showed higher noise reductions through the belt of trees than over the grass-covered ground. According to the results of this research the largest reduction, 6 dB, was seen in the Pinus brutia belt of trees, 60 m away from the road. This noise reduction is considered satisfactory due to the tree belts extending on both sides of the ring road.

STREET TREE HEALTH ASSESSMENT SYSTEM: A TOOL FOR STUDY OF URBAN GREENERY

This study deals with the recording of tree health and the evaluation of the greenery ratio, with a view to increase it, in three representative street trees in Thessaloniki city, North Greece. The three street trees are representative because of the species composition and the health of the trees on one hand and the flow of traffic on the other hand. The three street trees investigated in this study are located along three central roads of Thessaloniki city, namely Nikis Avenue, Egnatia Street and Karamanli Avenue. The study also includes the formulation of proposals in order to make some improvement in the choice of suitable species so as to increase the amount of greenery in the city. The results show that the most important problems related to tree health in the three streets are the leaves being attacked by insects and fungi as well as dry and broken branches of the crown. The majority of trees have moderate health. The greenery ratio in the three street trees is evaluated by the greenery’s surface and volume indicators, which are calculated depending not only on the number of trees but also on the surface and volume of their crowns. Finally, a linear model for the greenery’s volume indicator is estimated which depends on tree height, crown length and crown projection on the ground.

Seed treatments to break dormancy and stimulate germination in Cercis siliquastrum L. and Carpinus orientalis Mill.

The aim of this study was to investigate the methods that increase the germination of the native species Cercis siliquastrum and Carpinus orientalis, whose seeds exhibit dormancy. Seeds of C. siliquastrum were collected from a natural habitat and an urban environment, and seeds from both origins were given 6 different dormancy-breaking treatments. Seeds of C. orientalis were collected from an urban environment and were given 5 different dormancy-breaking treatments. For C. siliquastrum seeds, the treatment that gave the best final germination was the combination of acid scarification for 30 min and immersion in 500 ppm gibberellin (GA3) (52% for the seeds from the urban environment and 62.5% for the seeds from the natural habitat germinated). For C. orientalis seeds, the results showed that, the most effective treatment was moist-cold stratification for 12 weeks which resulted in 84% germination.