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This paper aims to determine the main factors that shape the spatial patterns of alien plant species occurrence across Natura 2000 Special Areas of Conservation (SACs) in Greece, and quantify their influence. A series of spatial analysis techniques for the development of a spatial database of the factors involved, followed by a boosted negative binomial Generalised Additive Model for location scale and shape, were implemented. Native plant species richness, topography and hydrography, human population density, and a spatial preference to the northern-western sites are the key factors that explain the variation in the occurrence of alien plant species. Native plant species richness and human population density have a positive effect on alien plant species presence, while topography aspects, such as elevation and slope, and the distance from the hydrographical network a negative one. All factors are indirectly linked to propagule pressure emphasizing the importance of human activities for the efforts on managing protected areas.

In this study we analysed a novel tree-growth dataset, inferred from annual ring-width measurements, of 7 forest tree species from 12 mountain regions in Greece, in order to identify tree growth - climate relationships. The tree species of interest were: Abies cephalonica, Abies borisii-regis, Picea abies, Pinus nigra, Pinus sylvestris, Fagus sylvatica and Quercus frainetto growing across a gradient of climate conditions with mean annual temperature ranging from 5.7 to 12.6°C and total annual precipitation from 500 to 950mm. In total, 344 tree cores (one per tree) were analysed across a network of 20 study sites. We found that water availability during the summer period (May-August) was a strong predictor of interannual variation in tree growth for all study species. Across species and sites, annual tree growth was positively related to summer season precipitation (PSP). The responsiveness of annual growth to PSP was tightly related to species and site specific measurements of instantaneous photosynthetic water use efficiency (WUE), suggesting that the growth of species with efficient water use is more responsive to variations in precipitation during the dry months of the year. Our findings support the importance of water availability for the growth of mountainous Mediterranean tree species and highlight that future reductions in precipitation are likely to lead to reduced tree-growth under climate change conditions.

Pinus nigra (black pine) is an ecologically and economically important species widely distributed around the Mediterranean Basin. P. nigra ecosystems have recently been affected by high severity fires occurring over the mountainous forest ecosystems of Southern Europe. The aim of this study is to investigate the post-fire regeneration patterns of black pine after a high severity crown fire which occurred on Mt Taygetos in Southern Greece. A network of 18 sites was selected to study black pine natural post-fire regeneration. Regeneration density was higher at the edges of patches that have remained unburned within the periphery of fire (0.406 individuals/m2) as compared to isolated burned areas (0.007 individuals/m2) although a significant between sites heterogeneity was recorded. Boosted regression trees analysis was used to explore the effects of environmental and microhabitat variables on black pine post-fire regeneration. The number of fires a site has experienced had a negative effect on regeneration density, while the presence of recovering ferns had a positive effect. The most important variable related to the black pine post-fire regeneration was distance from unburned patches. The result of the current study substantiates the importance of maintaining fire-resistant stands with large trees that are more likely to survive after a surface fire and which can also serve as seed sources for the recolonization of the burned area after severe crown fires.

The aims of this study were to map and analyze land use/land cover transitions and landscape changes in the Parnitha and Penteli mountains, which surround the Athens metropolitan area of Attica, Greece over a period of 62 years. In order to quantify the changes between land categories through time, we computed the transition matrices for three distinct periods (1945–1960, 1960–1996, and 1996–2007), on the basis of available aerial photographs used to create multi-temporal maps. We identified systematic and stationary transitions with multi-level intensity analysis. Forest areas in Parnitha remained the dominant class of land cover throughout the 62 years studied, while transitional woodlands and shrublands were the main classes involved in LULC transitions. Conversely, in Penteli, transitional woodlands, along with shrublands, dominated the study site. The annual rate of change was faster in the first and third time intervals, compared to the second (1960–1996) time interval, in both study areas. The category level analysis results indicated that in both sites annual crops avoided to gain while discontinuous urban fabric avoided to lose areas. At the transition level of analysis, similarities as well as distinct differences existed between the two areas. In both sites the gaining pattern of permanent crops with respect to annual crops and the gain of forest with respect to transitional woodland/shrublands were stationary across the three time intervals. Overall, we identified more systematic transitions and stationary processes in Penteli. We discussed these LULC changes and associated them with human interference (activity) and other major socio-economic developments that were simultaneously occurring in the area. The different patterns of change of the areas, despite their geographical proximity, throughout the period of analysis imply that site-specific studies are needed in order to comprehensively assess the driving forces and develop models of landscape transformation in Mediterranean areas.

In the past few decades there is an increasing trend of both fire activity and area burned in many regions of the world. Moreover, there is a worldwide concern regarding the increasing presence of crown fires in forest types that were historically prone to surface fires. Among the recently affected mountainous forest ecosystems are those of Pinus nigra, an ecologically and economically important species that is widely distributed around the Mediterranean Basin. Mount Taygetos, a mountainous landscape in Peloponnese, Greece, that was severely burned in 2007, was selected to carry out the first landscape-scale fire history reconstruction in P. nigra of the eastern Mediterranean. The aims of the study were to investigate whether fire-regime attributes can be reconstructed from fire-scarred trees and also to examine the consistency of fire occurrence and spatial extent through time within the area selected. Partial cross-sections were sampled within the perimeters of the more recent known large fires in the region, those of 2007 and 1998. The overall mean fire interval between 1845 and 2007 was 4.9 years, while for the larger fires this time window was 16.2 years. Even at the individual-sample scale, with the sample mean fire interval equaling 29.5 years, the fire frequency still falls within the range of the ‘‘predictable stand-thinning fire’’ regime. The majority of fire scars recorded were dated to the warm and dry season of summer to fall. During the last 165 years of fire reconstruction, neither fire frequency nor percentage of trees scarred by fires varied significantly. Nevertheless, the size of the area burned as well as the type of fire seem to have changed, with the 2007 event being the most extended crown fire encountered so far. Our study has provided additional evidence that P. nigra is indeed a fire-resistant tree species provided that it is exposed to surface fires, even if they are recurrently occurring. Shifts from this pattern may lead to local extirpation of the species, as in the case of severe and extended crown fires.

This study aims to provide a quantitative framework to model the dynamics of Mediterranean coniferous forests by integrating existing ecological data within a generic mathematical simulator. We developed an individual-based vegetation dynamics model, constrained on long-term field regeneration data, analyses of tree-rings and seed germination experiments. The simulator implements an asymmetric competition algorithm which is based on the location and size of each individual. Growth is parameterized through the analysis of tree-rings from more than thirty individuals of each of the three species of interest. A super-individual approach is implemented to simulate regeneration dynamics, constrained with available regeneration data across time-since-disturbance and light-availability gradients. The study concerns an insular population of an endemic to Greece Mediterranean fir ( Abies cephalonica Loudon) on the island of Cephalonia (Ionian Sea) and two interacting populations of a Mediterranean pine ( Pinus brutia Ten.) and a more temperate-oriented pine ( Pinus nigra Arn. ssp. pallasiana ) on the island of Lesbos (NE Aegean Sea), Greece. The model was validated against plot-level observations in terms of species standing biomass and regeneration vigour and adequately captured regeneration patterns and overall vegetation dynamics in both study sites. The potential effects of changing climatic patterns on the regeneration dynamics of the three species of interest were subsequently explored. With the assumption that a warmer future would probably cause changes in the duration of cold days, we tested how this change would affect the overall dynamics of the study sites, by focusing on the process of cold stratification upon seed germination. Following scenarios of a warmer future and under the current model parameterization, changes in the overall regeneration vigour controlled by a reduction in the amount of cold days, did not alter the overall dynamics in all plant populations studied. No changes were identified in the relative dominance of the interacting pine populations on Lesbos, while the observed reduction in the amount of emerging seedlings of A. cephalonica on Cephalonia did not affect biomass yield at later stages of stand development.

Patterns of Abies cephalonica Loudon seedling recruitment at its westernmost geographical limit (western Greece), were studied by monitoring their emergence, survival, and establishment for up to four years in the microhabitats to which seeds are dispersed. Seedlings were monitored on 200 permanent sampling plots established in 11 different locations covering the entire strictly protected Mount Aenos National Park (Cephalonia). Annual seedling mortality rate was estimated in relation to habitat characteristics as well as to their number of cotyledons. A. cephalonica presented the typical behaviour of a masting species in the number of seedlings produced over the four years of study. Of the habitat characteristics studied, ground cover, elevation, soil depth, slope and canopy openness were the main parameters that classified seedling habitat with respect to their emergence. Seedling survival was higher in years of low seedling production. Seedlings with higher cotyledon numbers exhibited higher survival. Our data indicate that A. cephalonica is characterized by remarkable reproductive plasticity, which is expressed in the number of seedlings produced each year and those surviving with respect to its habitat characteristics. Preserving the species implies preserving its habitat. In this sense, Mount Aenos National Park may be the most important protected area for the endemic fir in view of preserving its integrity through pre-emptive management, in the light of current and future threats.

Despite its relatively small length (650 m), Sekania beach on Zakynthos island (Ionian sea) is the single most important Caretta caretta L. nesting beach in the Mediterranean Sea. The aim of this work was to tackle the possible relationships of sand and vegetation characteristics with the nesting activity of sea turtle C. caretta . The vegetation structure and distribution along the sandy beach was studied with the use of line transect method. Grouping of plant species was revealed through an ordination method. Plant groups were distinguished and mapped. Sand texture, pH, and organic matter were measured on the transects. Nesting activity was also mapped on the beach and hatching success was recorded. It was concluded that where sand salinity is high enough to prevent vegetation development, wet sand is located at a threshold depth for excavating an egg chamber. It seems that well-sorted sand grains favor nesting activity on the beach. The increase of fine sand – from east to west – is proportional with the reduction of nesting density. The data collected for this study are organized in a GIS database, which could be the basis for the establishment of an integrated monitoring system for Sekania beach.

The long-term post-fire development of evergreen sclerophyllous shrub biomass was studied along a chronosequence of Pinus halepensis stands. These shrubs are regarded as the most important component of the understorey vegetation concerning the Mediterranean coniferous forests in question. Eighteen (18) forest stands of different post-fire age were selected for sampling in the Attica region (Central Greece) and the neighbouring island of Evia. Most of the forest stands were re-sampled for two to four consecutive years, depending on their post-fire age, since younger stands change more rapidly, and on the time available for this task. In every stand, the total cover and maximum height of evergreen sclerophyllous shrubs were recorded. Measurements were carried out within three 10x1 m randomly established plots. Each plot was divided into ten (10) 1x1 m quadrats. Thus, there were 30 quadrats per forest stand. Using two published regression equations, with the product of shrub height with the square of cover as the independent variable, the total understorey fuel load (TLOAD) and the “active” fuel load (ALOAD) for fire modelling purposes were calculated. It was shown graphically and through regression analysis that, at least in Central Greece, there are two distinct types of Pinus halepensis forest stands in regard to the understorey vegetation. The first (type 1) is characterized by the dominance of evergreen sclerophyllous shrubs in the understorey, with a shrub cover of 50-80%. In the other (type 2), the cover of such shrubs is much lower, usually

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Summary The annual rhythm of cambial activity is compared in Arbutus unedo and Quercus coccifera, two typical shrubs of the maquis in the Mediterranean-type ecosystem of Greece. The growth activity of the species is more or less focused on the favourable periods. The behaviour of Arbutus unedo revealed stronger correlation with moisture conditions, while that of Quercus coccifera seems to be more restricted in time and less controlled by moisture availability. These results indicate that both species, although growing together have different adaptive strategies to the same climatic conditions.