Marianthi Tsakaldimi

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.

Seed and cone diversity and seed germination of Pinus pinea in Strofylia Site of the Natura 2000 Network

Variation in cone size, seed number per cone, seed potential, seed efficiency, seed morphology and seed germination behavior of Pinus pinea and its relation to stand conditions was analyzed. Data were collected from P. pinea forest in Strofylia, southern Greece, a forest that belongs to the Natura 2000 European network and the RAMSAR convention and is characterized by the absence of regeneration for many decades. The pine stands found in the area were distinguished into five categories according to a previous study and our observations, regarding stand age, canopy cover and the degree of stress by human pressure. The categories are: (I) young artificial, (II) closed-mature, (III) open-mature, (IV) over-mature stands and (V) highly degraded stands. Cones were collected from all stand types and their morphological characteristics as well as their seed production were measured. Seeds were extracted from the collected cones, measured and their germination behavior was tested. The findings showed that the over-mature and the high degraded stands and to a lesser extent, the closed-mature stands, produced significantly smaller cones with a lower seed potential, a lower number of filled seeds per cone, a greater number of not fully developed seeds and reduced seed morphological characteristics than the young and open-mature stands. However, the seed germination behavior of fully developed seeds was only slightly affected by the stand type.

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.

Effect of light conditions and salinity on germination behaviour and early growth of umbrella pine (Pinus pinea L.) seed

Summary Pinus pinea L. (umbrella pine) is a tree species distributed around the Mediterranean basin. The ecological, landscape, recreational and soil conservation uses of P. pinea, and its aesthetic value, make this species important for landscape planning and multipurpose forestry. In this study, seeds of P. pinea were collected from the two principal forests where the species is found in Greece (the Strofylia Forest, southern Greece, and the Sithonia Peninsula, northern Greece), in order to examine the effects of light conditions and soil salinity, two important environmental factors, on seed germination behaviour and early growth. The effect of light alone on seed germination was ascertained under different light regimes; while, to investigate the effect of salinity, seeds maintained in continuous light were watered with varying concentrations of NaCl and, after germination, the early growth of seedlings was monitored. The findings showed that the percentage germination of P. pinea seed is high and does not depend on light or dark conditions, while salinity markedly inhibited seed germination at NaCl concentrations of 0.05 M and above. Seedlings raised under saline conditions (0.02 M NaCl) were significantly smaller than those of the controls, especially in their below-ground structures.

A synthesis of results on wastes as potting media substitutes for the production of native plant species

The three major functions of a potting medium for plant production is to provide support, to retain water and nutrients, and to allow oxygen diffusion to the roots. A potting medium should meet the requirements of practical plant production such as: to be available and ready at all times, easy to handle, lightweight and to produce uniform plant growth. Constituents such as natural soil, peat, sand, perlite and vermiculite are commonly used as substrates for container plant production. Nevertheless, these materials might be fully or partially replaced by various organic or inorganic wastes, thus achieving environmental and economic benefits. This study presents a synthesis of results extracted from many trials on waste materials as potting media substitutes for the seedlings production of the following native plant species: Pinus halepensis, Quercus ilex, Quercus macropleis and Ceratonia siliqua. The studied waste materials were either organic or inorganic components including: spoils of peridotite, raw rice hulls, coconut fiber and kenaf (the ground stem of the plant H. cannabinus L). The experimental potting media tested were: peat:perlite (3:1), a common medium used for seedling production, peat:spoils of peridotite (3:1), peat:rice hulls (3:1), peat:rice hulls (1:1), peat:coconut fiber (1:1), kenaf (100%) and kenaf:peat:rice hulls (3:1:1). The main physical (water retention characteristics, bulk density, particle density, total porosity) and chemical (N, K, Ca, Mg, soluble P, exchangeable cations, pH and loss on ignition) properties of each potting medium were measured. For each plant species the following seedling quality parameters were assessed: morphological characteristics (shoot height, root collar diameter), shoot and root biomass, Dickson’s quality index and shoot and root nutrient concentrations. Then seedlings were planted in the field and their survival and growth was monitored. The feasibility of replacing peat or perlite with various waste materials as well as their effect on seedling quality and field performance are discussed.

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.