Geographical Distribution and Long-Term Monitoring of Physokermes hellenicus (Hemiptera: Coccomorpha: Coccidae) on Abies spp. (Pinales: Pinaceae) in Greece

The scale Physokermes hellenicus (Kozár & Gounari) (Hemiptera: Coccidae) has been recently included in the Greek entomofauna as a beneficial honeydew species. However, there are no adequate data about its geographical distribution and degree of infestation. Therefore, a study was conducted to examine these parameters in fifteen mountains of Greece. Furthermore, the monitoring of P. hellenicus infestation was carried out over a six-year period with regard to natural enemies and honeydew presence at three mountains (i.e., Menalon, Parnis and Tymfristos) that are traditional honeybee foraging areas. An extensive geographical distribution of the scale was negatively correlated with the latitude. Over the period of the study, P. hellenicus infestation exhibited a decreasing trend in the three mountains, which was more obvious at Menalon. The abundance of natural enemies of P. hellenicus, their effectiveness on honeydew excretion and the fecundity of P. hellenicus are discussed. The reduction in the honey produced at the Menalon mountain (a protected designation of origin product) could be attributed to the reduced presence of P. hellenicus in the fir forest. Among the other identified arthropods, Dreyfusia nordmannianae Eckstein (Hemiptera: Adelgidae) is reported for the first time infesting Abies cephalonica (Pinales: Pinaceae) in Greece. Furthermore, this species is reported for the first time as a co-parasite with P. hellenicus on A. cephalonica in Greece. Since D. nordmannianae is a serious pest, additional research is needed to determine its status in Greek fir forest ecosystems.

Effect of Seedling Provenance and Site Heterogeneity on Abies cephalonica Performance in a Post-Fire Environment

Reforestation constitutes a challenge in post-fire ecosystem restoration, although there are limitations such as species and genotype selection, planting and management design, and environmental conditions. In the present study, the basic issue is the longevity of Abies cephalonica Loudon—the Greek fir seedlings planted extensively in Parnitha National Park (Central Greece), located near the metropolitan city of Athens, following the large-scale wildfire of 2007. Seedling performance was assessed for a 3-year monitoring period (2013–2015) through the establishment of 8 permanent transects, including 400 seedlings at the burned, reforested sites. According to the long-term reforestation project, two seedling provenances were used: (a) from Mt. Mainalon (South Greece, Vytina provenance) and (b) the local one from Mt. Parnitha. Both provenances showed a relatively successful survival rate reaching, in average, 73.8%, with the first summer after planting being crucial for seedling survival. The overall mean seedling height was 39.2 ± 1.1 cm, with a mean crown diameter of 47.3 ± 1.4 cm in the last monitoring survey. Although Parnitha seedlings seem to perform better in terms of growth, seedling performance in both provenances was affected by reforestation site characteristics, mainly altitude and aspect. Approximately one third of seedlings exhibited damage in their crown architecture (29.8%), while apical bud damage was less extensive (12.2%) in the final field measurement. Data indicate that seedling performance has proved to be quite promising for post-fire restoration, although long-term monitoring data should be considered.

Long-Term Forest Dynamics of Oromediterranean Fir Forests in Greece

The present study illustrates the situation of the genus Abies in the Mediterranean and in Greece, focusing in detail on the oromediterranean forest of the southern Peloponnese, at Mt. Taygetos. The existing pattern of forest dynamics (mosaic cycle) and also the timberline dynamics are presented and explained. Since fir forests are highly susceptible to drought-related impacts (fire and fir dieback: insect outbreaks/ forest pathogens), the analysis of the present situation is put into perspective by looking at the role of direct human influence and the climatic fluctuations of the past, taking into consideration dendrochronological findings and archival climate records. In view of climate warming the question is whether in recent decades the fingerprints of climate change can already be observed in the Greek fir forests. The study concludes that drought periods and climatic extremes have been an essential part of Greek climate for many centuries, causing high natural forest vulnerability. Therefore, fir dieback and fires are not a new phenomenon either – but in recent decades the accumulation of fuel, caused by land abandonment, has increased the danger of large wildfires. Nevertheless, the Greek mountain forests are highly endangered by increases in aridity and/or more frequent climate extremes (heat waves), together with increased risk of wildfires. Recommendations for an active forest management (counteracting expected adverse effects of climate change, by focusing on the establishment of an Abies cephalonica Loudon /Pinus nigra J. F. Arnold mosaic cycle) and further scientific research are provided.

The structure of the needles mesophyll in species of the Pinaceae family with flat leaves

The spatial organization of mesophyll and three-dimensional forms of assimilative cells are considered on the example of 7 species of the Pinaceae family with flattened leaves: Abies cephalonica, A. concolor, A. sibirica, Larix sibirica, Picea omorica, Pseudotsuga menziesii and Tsida canadensis. It was shown that three types of mesophyll cells are distinguished in the flattened needles: palisade, spongy and median. Median cells are appreciable both with well-defined and weak differentiation of assimilative tissue; they can have simple and complex cellular forms.

Masting and regeneration dynamics of Abies cephalonica, the Greek endemic silver fir

Masting and regeneration dynamics were investigated in a long-term perspective using Abies cephalonica as a study tree species. Extensive fieldwork was implemented in Parnitha National Park, Greece, following a large-scale wildfire. Annual cone production was monitored for a 5-year period in 130 tagged trees, in 13 plots with 10 individuals each, established both within the unburned part of the forest and in surviving fragments of the burned area. In the most recent masting year, a high percentage (88%) of cone-bearing trees was recorded, along with a sizeable, average cone production (40.8 cones per tree). In the intermediate, non-masting years, the corresponding values ranged from 2% to 55% and 0.08 to 5.9 cones per tree, respectively. The reproduction process is affected by both tree density and regional climatic conditions, in particular temperature during spring of the maturation year and precipitation during spring and summer of the previous year. For the first time according to our knowledge, natural regeneration was recorded for a 4-year period, in 13 permanent transects within the monitoring plots, in relation with a masting event and the additional implications of a preceding wildfire. Highest mean density of seedlings and saplings (11.4 per m2) was observed during the first spring after masting. In the non-masting years, the corresponding value ranged from 2.1 to 2.9 per m2. Seedling survival during their first summer was considerable (30–76%) but stabilized afterwards (1–3 years) at a lower level (10–20%). The particular post-masting seedling flush was followed by an extremely high mortality rate (88.6%) and cannot represent a major recruitment event.

Interannual variability of germination and cone/seed morphometric characteristics in the endemic Grecian fir (Abies cephalonica) over an 8-year-long study

Abies cephalonicacone and seed morphometric characteristics as well as seed germination behaviour were investigated during an 8-year-long diachronic study (2007–2015). The research was carried out in Parnitha National Park, in the part of this Greek endemic, silver fir population that was spared from an unprecedented wildfire (2007). A statistically significant interannual and among-tree variation of cone traits has been identified, except for cone diameter. Cone length is correlated to the number of seeds per cone, while the percentage of empty seeds has been consistently high, with extreme values of 29.3 and 81.8% in a masting (2015) and lean crop (2009) year, respectively. There is also a considerable proportion of dead (including infected) and non-germinated seeds, and the eventual germinable fraction is well below 25% with spikes in masting years (39.4 and 60.9% in 2010 and 2015, respectively). Untreated seeds have been tested at a wide range of constant and alternating temperatures and germination is completed within 4–5 weeks atT≥ 15°C andca15 weeks at 5–10°C. A chilling pretreatment of 4–8 weeks (at 2–4°C) concludes germination at 15–20°C within 2 weeks. A significant white light requirement has been observed for untreated seeds at 15–20°C, while germination was light indifferent at lower or higher temperatures. Data obtained in this study confirm the present, field seed germination during springtime; we may also predict an earlier germination (late autumn to mid-winter) in forest gaps, under the predicted, warmer conditions in the future.

The scale insect Dynaspidiotus abietis (Schrank) on Abies cephalonica (Pinaceae)

Data on phenology and morphology of the scale insect Dynaspidiotus abietis (Schrank) (Hemiptera: Diaspididae), found on fir trees Abies cephalonica (Pinaceae) on mount Taygetos (Peloponnesus - southern Greece), are presented. The species is biparental and oviparous. During this study (June 2004 – August 2006) D. abietis completed one generation per year. It overwintered as mated pre-ovipositing female adult. Ovipositions were recorded from May to July. The majority of the hatches of the crawlers were observed in June. Predated individuals of the scale which were found during the study period were attributed to the presence of the predator Chilocorus bipustulatus (L.) (Coleoptera: Coccinellidae).

Physokermes hemicryphus (Dalman) a fir scale insect useful to apiculture in Greece

Physokermes hemicryphus (Dalman) is an important honeydew producing scale insect useful to apiculture. It lives mainly on Abies cephalonica Loud. and to a lesser degree on Abies borisii regis Mattf. These fir trees exist in most fir forests of Greece. It has one generation per year. Overwintering takes place in the second instar nymph. The female overwinters under the bud scales of the forks of the fir host and the male on the needles. Adults appear in spring and crawlers in July. In August the population consists mainly of first instar nymphs. The second instar nymphs start to appear in August and by late October the whole population is at the second nymphal instar, which is the overwintering one. The insect occurs in the fir forests of Greece every year but its population level fluctuates, due to weather conditions and biological factors (parasites, predators). The coexistence on the same host plant of P. hemicryphus with the scale Eulecanium sericeum (Lindiger) and the aphid Milldams abietinus (Koch) prevents the visit of honeybees to fir trees. On the other hand it favours the augmentation of the P. hemicryphus population. Four parasites were found, from which the Encyrtidae Pseudorhopus testaceus (Razz.) and Microterus lunatus (Dalman), are recorded for the first time in Greek fauna.