Elias Milios

Structure and regeneration patterns of the Juniperus excelsa Bieb. stands in the central part of the Nestos valley in the northeast of Greece, in the context of anthropogenic disturbances and nurse plant facilitation

In order to analyse the structure and regeneration patterns of the Juniperus excelsa Bieb. stands on the slopes of the Nestos valley, 40 sample plots were established and more than 120 J. excelsa trees and seedlings were cut and collected. The main results of this research indicate that stand structure, species mixture, age structure and stand development patterns were strongly determined by the interaction of anthropogenic disturbances such as grazing and illegal cuttings, and the facilitation of adult J. excelsa trees in the establishment of the J. excelsa seedlings. Their effect was influenced by site quality and J. excelsa together with other species ecology. Under present conditions, almost all J. excelsa seedlings, except for a small number of plants, are found under the facilitation of nurse plants that belong to the same species. It seems that the layer of litter underneath the nurse plants combined with the protection of seedlings against grazing play an important role in the establishment and growth of J. excelsa seedlings.

Analysis of natural Fagus sylvatica L. s.l. regeneration in low elevation stands located in the central part of the Evros region in northeastern Greece: Is sprout origin regeneration significant for species maintenance?

Abstract The aim of this study was (a) to analyse natural Fagus sylvatica L. s.l. regeneration in low elevation stands located in the central part of Evros region in northeastern Greece in relation to factors such as site productivity, type of silvicultural treatment and regeneration origin and (b) to determine whether or not sprout origin regeneration is significant for the maintenance of beech stands. One hundred and twenty plots (3 m × 3 m) were established in areas where thinnings and regeneration fellings had taken place, and in two site productivity regimes. In each plot, the number of beech seedlings, saplings, and stump or root sprouts (regeneration plants) with a height of up to 3 m was counted, and their height measured. Our findings indicate that even though reproduction by seed is the predominant regeneration mechanism in our stands, in the medium productivity sites sprouts represent a significant percentage of the total number of plants. Moreover, sprouting functions as a mechanism of maintenance of beech stands in medium productivity sites. During the regeneration fellings practised in this area, it is advisable to cut the seedlings and saplings of the advanced regeneration in order to supplement the seed-derived plants with seedling sprouts.

Establishment and survival of Pinus brutia Ten. seedlings over the first growing season in abandoned fields in central Cyprus

Abstract The present study was carried out in abandoned fields in central Cyprus. The main objective was to examine the impact of the regeneration environment on the establishment and survival of Pinus brutia seedlings. Sixty-four permanent plots of 16 m2 were randomly established in two distinct sites. Four regeneration environments were recorded: (a) bare soil under the crown of a P. brutia tree, (b) soil under the canopy of a P. brutia tree and low shrubs, (c) bare soil in open areas, and (d) soil under the canopy of low shrubs in open areas. All P. brutia seedlings were classified in categories according to their regeneration environment. In all plots, the density of the P. brutia seedlings was measured in three different seasons (spring, summer, autumn). Soil temperatures were recorded, samples of surface soil were taken and the percentage of soil organic matter was measured. The main conclusions drawn from this research were the following: (1) the mature P. brutia trees and low shrubs facilitate the establishment and especially the survival of P. brutia seedlings, as all seedlings in bare vegetation ground had died by the end of the growing season, and (2) the importance of facilitation increases as abiotic stress rises.

Modelos de índice de sítio para o pinheiro calabrês (Pinus brutia Ten.) na Ilha Thasos Grécia

Um modelo de indice de sitio para o pinheiro calabres ( Pinus brutia Ten.) na ilha Thasos Grecia foi apresentado. O modelo foi ajustado e validado com dados de analises de tronco de 150 arvores, obtidas de 75 parcelas de area fixa provenientes de cinco sitios experimentais. Quatro equacoes de crescimento em altura na forma de diferenca algebrica foram testadas, sendo que a funcao de BAILEY e CLUTTER (1974) foi considerada apropriada devido a sua boa performance tanto com dados de ajuste como os de validacao. Os resultados mostraram erros mais baixos do que 5 % e pouco vies.

Tracheid length – growth relationships of young Pinus brutia grown on reforestation sites

Brutia pine (Pinus brutia Ten.) reforestations have been successfully used for decades in restoration of degraded forest ecosystems in Greece. The future purpose of these reforestations might expand to include wood utilisation. This study provides information on tracheid length of juvenile brutia pine aged 14–22 years grown on good and medium sites in Northeastern Greece. In addition, relationships among ring width, latewood proportion, wood density, and tracheid length were evaluated by using Causal Correlation Analysis. Similar mean tracheid length values were found for good and medium sites. Radial variability of tracheid length was similar on the good and medium sites, showing the typical increase in the juvenile phase. On both site types, latewood proportion showed a strong and positive relationship with wood density. Unexpectedly and only on the good sites, a significant positive relationship was found between ring width and wood density. On the medium sites, tracheid length was negatively related to fast growth and positively to high wood density. Tracheid length on the good sites was correlated only with latewood proportion with a weak positive relationship. The overall results may provide opportunities to better understand the quality of small-dimension timber of brutia pine and to better utilise it.

Deadwood volume assessment in Calabrian pine (Pinus brutia Ten.) peri-urban forests: Comparison between two sampling methods

ABSTRACT In the Sustainable Forest Management, deadwood is a fundamental substrate for numerous species, and a key factor in carbon and nutrient cycles. The main aim of the paper is to estimate the amount of deadwood in two Calabrian pine forests (Monte Morello in Italy; Xanthi in Greece) characterized by different stand conditions and management practices. The second aim is to compare two different sampling methods to estimate the volume of lying deadwood: the fixed-area sampling (FAS) method and the line intersect sampling (LIS) method. The results show that the Monte Morello peri-urban forest is characterized by a high quantity of deadwood (75.1 m3 ha−1) divided in 80% of lying deadwood, 18% of standing dead trees, and 2% of stumps. The Xanthi peri-urban forest is characterized by a total amount of deadwood of 9.21 m3 ha−1 divided in 34% of lying deadwood, 18% of standing dead trees and 48% of stumps. The mean volume of lying deadwood in Monte Morello estimated using the FAS is 59.91 m3 ha−1, while using the LIS the mean volume is 64.9 m3 ha−1. In the Xanthi, the mean volume of lying deadwood is 3.11 m3 ha−1 using FAS and 5.49 m3 ha−1 using LIS.

DIAMETER AT BREAST HEIGHT ESTIMATED FROM STUMPS IN Quercus frainetto IN THE REGION OF EVROS IN NORTHEASTERN GREECE

For foresters, it is sometimes required to estimate the diameter at breast height of tree that has been cut, though it is often only the stump that is available as an indicator of size, after illegal logging and quick removal of the cut trees from the forest. In this study, equations for predicting the diameter at breast height, were fit specifically for Quercus frainetto in the region of Evros in northeastern Greece. The selected equations (quadratic model) were, where is the estimated diameter at breast height d (cm), and dst is the measured diameter at stump height (cm); for pure stands (R2 = 0.94); for mixed stands (R2 = 0.92); for the whole forest (R2 = 0.94).

Treatments for seed germination improvement in Prunus azorica, Frangula azorica and Morella faya, three native species of Azores Islands

Abstract The aim of this study was to determine the best treatment to maximize seed germination of three native species of the Azores islands (Prunus azorica, Frangula azorica and Morella faya). In all three species the effect of gibberellic acid (GA3) application and cold stratification on seed germination under controlled conditions (light and temperature) was investigated. In particular, seeds of all three species were treated with 500 and 1000 mg L–1 GA3 for 24 hours and were subsequently cold stratified at 3–5°C for 0, 1 and 2 months. In addition, seeds from each species were only cold stratified for 0, 1 and 2 months and also seeds with the endocarp (stones) of P. azorica only were subjected to outdoor stratification from 1 October 2014 up to 28 February 2015. Untreated seeds of all three species exhibited a very low germination percentage, indicating that the seeds of all three species were dormant. For all three species, the germination of seeds untreated with GA3 significantly increased as the cold stratification period increased whereas GA3 application was more effective in improving germination in P. azorica and F. azorica than M. faya seeds. Furthermore, stones of P. azorica that were subjected to outdoor stratification and then transferred to germinate under controlled standard conditions exhibited high and rapid germination.

Site index curves for the golden oak species (Quercus alnifolia)

SUMMARY The golden oak (Quercus alnifolia) is the most ecologically important endemic species of Cyprus; therefore, the development of site index curves for classification of golden oak trees to site qualities will be useful for the rational management and monitoring of natural habitats of the golden oak. The objective of this work was to develop site index curves for the golden oak species. From areas of natural spread of golden oak in Cyprus, sixty dominant trees were selected randomly and cut; for each sampled tree a stem analysis was conducted. Forty-two linear and non-linear regression models were tested for fit-to-height/age data; and from these, the most suitable was chosen for the development of a guide curve. Afterwards, a set of anamorphic site indices was created based on this curve. The selected height/age model was: 2 2 ˆ 29.576 5.315 0.091 t h tt = ++ . At the base age of 40 years, the selected model estimated a height of 4 m (SI4). Using the selected model as the guide curve for the development of anamorphic site index curves, we drew two more curves: SI3 (at the age of 40 years the estimated tree height is 3 m) and SI5 (at the age of 40 years the estimated tree height is 5 m).

Short-term effects of thinning on soil CO2, N2O and CH4 fluxes in Mediterranean forest ecosystems

In Mediterranean ecosystems an increasing demand for in situ trace gas exchange data is emerging to enhance the adaptation and mitigation strategies under forest degradation. Field-chamber green-house gas fluxes and site characteristics were analysed in two Mediterranean peri-urban pine forests showing degradation symptoms. We examined the effect of different thinning interventions on soil CO2, CH4 and N2O fluxes, addressing the relationships with the environmental variables and C and N contents along forest floor-soil layers. Soil temperature resulted as the main driving variable for CO2 efflux and CH4 uptake. Soil moisture content and organic matter availability affected CO2 emission patterns in the two sites. N2O fluxes showed a positive correlation with soil moisture under wetter climatic conditions only. GHG fluxes showed significant correlations with C and N content of both forest floor and mineral soil, especially in the deepest layers, suggesting that it should be considered, together with environmental variables when accounting GHG fluxes in degraded forests. Short-term effects of thinning on CO2 emissions were dependent on disturbance induced by logging operations and organic matter inputs. After thinning CH4 uptake increased significantly under selective treatment, independently from specific site-induced effects. N2O fluxes were characterized by low emissions in both sites and were not affected by treatments. Soil CO2 efflux was the largest component of global warming potential (GWP) from both sites (11,553 kg ha-1 y-1 on average). Although it has a large global warming potential, N2O contribution to GWP was about 131 kg CO2eq ha-1 y-1. The contribution of CH4-CO2 equivalent to total GWP showed a clear and significant CH4 sink behaviour under selective treatment (36 kg ha-1 y-1 on average). However, in the short-term both thinning approaches produced a weak effect on total GWP.