The Database of European Forest Insect and Disease Disturbances: DEFID2

[EN] Insect and disease outbreaks in forests are biotic disturbances that can profoundly alter ecosystem dynamics. In many parts of the world, these disturbance regimes are intensifying as the climate changes and shifts the distribution of species and biomes. As a result, key forest ecosystem services, such as carbon sequestration, regulation of water flows, wood production, protection of soils, and the conservation of bio-diversity, could be increasingly compromised. Despite the relevance of these detri-mental effects, there are currently no spatially detailed databases that record insect and disease disturbances on forests at the pan-European scale. Here, we present the new Database of European Forest Insect and Disease Disturbances (DEFID2). It comprises over 650,000 harmonized georeferenced records, mapped as polygons or points, of insects and disease disturbances that occurred between 1963 and 2021 in European forests. The records currently span eight different countries and were acquired through diverse methods (e.g., ground surveys, remote sensing techniques). The records in DEFID2 are described by a set of qualitative attributes, including se-verity and patterns of damage symptoms, agents, host tree species, climate-driven trigger factors, silvicultural practices, and eventual sanitary interventions. They are further complemented with a satellite- based quantitative characterization of the affected forest areas based on Landsat Normalized Burn Ratio time series, and dam-age metrics derived from them using the LandTrendr spectral–temporal segmentation algorithm (including onset, duration, magnitude, and rate of the disturbance), and pos-sible interactions with windthrow and wildfire events. The DEFID2 database is a novel resource for many large-scale applications dealing with biotic disturbances. It offers a unique contribution to design networks of experiments, improve our understanding of ecological processes underlying biotic forest disturbances, monitor their dynamics, and enhance their representation in land-climate models. Further data sharing is en-couraged to extend and improve the DEFID2 database continuously. The database is freely available at https://jeodpp.jrc.ec.europa.eu/ftp/jrc- opend ata/FOREST/DISTURBANCES/DEFID2/SIEC Joint Research Centre; European Commission, Grant/Award Number: 101059498; European Research Council, Grant/Award Number: 101039567; Ministry of Research, Innovation and Digitalization of Romania; LifeWatch— POC project, Grant/Award Number: 327/390003/06-11-202

Community dynamics and transmission within the Phialocephala fortinii s.l. - Acephala applanata species complex

Just about all plants are colonized by fungal endophytes. Dark septate endophytes (DSE) are a diverse group of ascomycetes colonizing roots of a vast number of plants in many different ecosystems. Considering the Northern hemisphere, the majority of DSE belong to the Phialocephala fortinii s.l. - Acephala applanata species complex (PAC), consisting of at least 21 morphologically indistinguishable cryptic species (CSP), to seven of which species rank was formally assigned. CSP are reproductively isolated and so far no teleomorphic form of the fungus has been found, even tough evidence exists that sexual reproduction occurs or has occurred in the past. PAC communities are highly diverse and still little is known about the factors influencing community formation. Even though PAC are highly successful root colonizers, their ecological function is poorly understood. Therefore, community structure and dynamics, competition and possible modes of transmission were investigated within the scope of this thesis. In a first study, spatial and temporal dynamics of a PAC community in an undisturbed Norway spruce (Picea abies) forest, originally assessed in 2004, were reassessed ten years later. The spectrum of species remained virtually the same over this period. In both years, a majority of isolates belonged to Phialocephala turicensis, Phialocephala letzii, Phialocephala europaea, and Phialocephala helvetica and a trend towards fewer species per sampling plot could be observed. Microsatellite analysis revealed that none of the PAC genotypes detected in 2004 were present at the same grid points in 2014. Furthermore, only four of the 22 genotypes detected in 2004 were found again in 2014, indicating recombination. Recognizing that the PAC community is subjected to both spatial and temporal changes, the competitiveness of three P. subalpina strains and two P. fortinii s.s. strains was tested under laboratory conditions in living roots of inoculated Norway spruce saplings. Saplings were first colonized by a “resident” strain (“primary colonizer”) followed by transplantation into a substrate colonized by the “invading” strain (“secondary colonizer”). Power of retention and power of colonization were calculated for each strain. Overall, the strains clearly differed in their ability to colonize roots, as well as in their capability of offering resistance against an invading strain, and also in their power of suppressing an already established “resident” strain within living roots. With the possibility of inoculating Norway spruce saplings, transmission of PAC was tested using three different set-ups in a semi-sterile substrate: (I) without root contact by separating inoculated and non-inoculated saplings with a fine mesh, (II) confrontation of a non-inoculated sapling wrapped in fine mesh with a colonized substrate without contact, and (III) direct root contact between inoculated and non- inoculated spruce. PAC was transmitted most successfully via direct root contact between saplings, followed by saplings confronted with the inoculated substrate. But also contact-less transmission from tree to tree through the semi-sterile soil could be demonstrated for short distances of 0.5 cm. In the last study, transmission of PAC was investigated under more near-natural conditions in mesocosms containing natural Norway spruce regeneration, partly in a climate chamber and partly outside in the forest. The effects of disturbance (clear-cutting and drought) on a resident PAC community along with the ability of an alien PAC strain to invade a well established ecosystem were tested. The overall PAC community structure remained similar, despite successful introduction of the alien strain into the mesocosms. Only A. applanata was found to profit from clear-cutting, while the general PAC presence was significantly reduced. Drought did not have any significant influence on the PAC community. Our results show that the PAC community is subjected to spatial and temporal changes. These changes are, however, comparatively slow. Colonization of unsterile but PAC-free Norway spruce saplings, as well as the competitive strength of PAC were shown to be strain dependent. Together with the demonstration of PAC transmission by root contact and successful integration of an alien PAC strain into well-established communities, these findings are a first step towards understanding the processes shaping PAC assemblages in natural forest ecosystems

Spatial and temporal dynamics in the Phialocephala fortinii s.l. – Acephala applanata species complex (PAC)

Background and aims Dark septate endophytes of the Phialocephala fortinii s.l. – Acephala applanata species complex (PAC) are abundant root colonizers of woody plants in boreal and temperate forest ecosystems where they form complex communities. Community structure was spatially stable for 3 years in a previous experiment, suggesting PAC’s inability to disperse or mutual inhibition of neighboring PAC genotypes. The aim of this study was to test whether changes in PAC community structure occur at all. Methods The community structure originally determined in 2004 was reassessed in 2014 in a Norway-spruce plantation using microsatellite genotyping. Results Most isolates belonged to Phialocephala turicensis, P. letzii, P. europaea, and P. helvetica in both years. P. uotilensis and Acephala applanata were rare. PAC species were the same at only two grid points in both years. P. europaea was more frequent than P. turicensis in 2004 whereas the situation was opposite in 2014. Only four of the 22 genotypes in 2004 were found in 2014. Interestingly, none of the genotypes was detected at the same grid points in both years. Extended sampling in 2014 led to a significantly higher number of grid points testing positive for the presence of P. turicensis and P. helvetica. Conclusions More than 3 years are required to detect shifts in PAC community structures. The observed shifts suggest that PAC are able to disperse in soil or via root networks, though very slowly.ISSN:0032-079XISSN:1573-503

Ecological factors influencing norway spruce regeneration on nurse logs in a subalpine virgin forest

Regeneration of Picea abies in high-elevation mountain forests often depends on the presence of coarse woody debris (CWD), as logs provide sites with more favorable conditions for spruce regeneration compared to the forest floor. However, there is little quantitative knowledge on the factors that are conducive to or hindering spruce establishment on CWD. We examined spruce regeneration on CWD by sampling 303 plots (50 cm × 50 cm each) on 56 downed logs in a virgin forest in the Swiss Alps. Variables describing microsite conditions were measured, and fungi were isolated from wood samples. To investigate the relationship between the ecological factors and establishment success, two models were fitted with seedling and sapling density as response variables, respectively. Besides log diameter, the models identified different ecological factors as significant for seedling and sapling establishment, i.e., regeneration depends on different factors in different development stages. Seedling density depended on the type of rot, log inclination, and decay stage. Sapling density depended mainly on light availability, cover by bark and moss, the time of tree fall, and the distance between the log surface and the forest floor. A total of 22 polypore fungi were isolated from the wood samples, four of them being threatened species. White- and brown-rot fungi were found in all decay stages. The visual assessment of the type of rot in the field corresponded in only 15% of cases to the type of rot caused by the isolated fungi; hence caution is needed when making field assessments of rot types.ISSN:1999-490

Root contact dominates vegetative transmission of the Phialocephala fortinii s.l. – Acephala applanata species complex (PAC)

The Phialocephala fortinii s.l. – Acephala applanata species complex (PAC) is composed of closely related endophytic ascomycetes colonizing roots of coniferous trees. Their means of dispersal and teleomorphic form are still unknown. Accordingly, we focused on vegetative mycelial spread of PAC i) via root contacts from PAC-inoculated to PAC-free saplings, ii) through semi-sterile soil from PAC-colonized to PAC-free saplings (without contact) and iii) through semi-sterile soil from PAC-colonized substrate to PAC-free saplings (without contact). Five PAC strains were selected for the experiment. All three modes of PAC transmission found support and were confirmed by metabarcoding. However, transmission via root contact was found to be the most successful. Growth of PAC through soil was also observed whereby transmission from PAC-colonized substrate to PAC-free saplings was more frequent than transmission from PAC-colonized to PAC-free saplings. The transmission rates depended on the PAC strain. Overall, we found support for vegetative transmission of PAC via root contact and active mycelial spread through semi-sterile soil.ISSN:1754-5048ISSN:1878-008

Investigating Host Preference of Root Endophytes of Three European Tree Species, with a Focus on Members of the Phialocephala fortinii—Acephala applanata Species Complex (PAC)

Host preference of root endophytes of the three European tree species of Norway spruce (Picea abies), common ash (Fraxinus excelsior), and sycamore maple (Acer pseudoplatanus) were investigated in two forest stands near Zurich, Switzerland. The focus was placed on members of the Phialocephala fortinii s.l. (sensu lato)—Acephala applanata species complex (PAC), as well as other dark septate endopyhtes (DSE). PAC species were identified based on 13 microsatellite loci. Eleven PAC species were found, with Phialocephala helvetica, P. europaea being the most frequent. All but cryptic species 12 (CSP12) preferred Norway spruce as a host. Though very rare in general, CSP12 was most frequently isolated from maple roots. Regarding the abundant PAC species, P. helvetica and P. europaea, the preference of spruce as a host was least pronounced in P. europaea, as it was also often isolated from ash and maple. It is the first record of PAC found on common ash (Fraxinus excelsior). Cadophora orchidicola, a close relative of PAC, has frequently been isolated from ash. Various species of the Nectriaceae (Cylindrocarpon spp.) have often been isolated, particularly from maple roots. By comparison, Pezicula spp. (Cryptosporiopsis spp.) was found to be abundant on all three hosts. Phomopsis phaseoli exhibits a clear preference for spruce

Ecological Factors Influencing Norway Spruce Regeneration on Nurse Logs in a Subalpine Virgin Forest

Regeneration of Picea abies in high-elevation mountain forests often depends on the presence of coarse woody debris (CWD), as logs provide sites with more favorable conditions for spruce regeneration compared to the forest floor. However, there is little quantitative knowledge on the factors that are conducive to or hindering spruce establishment on CWD. We examined spruce regeneration on CWD by sampling 303 plots (50 cm × 50 cm each) on 56 downed logs in a virgin forest in the Swiss Alps. Variables describing microsite conditions were measured, and fungi were isolated from wood samples. To investigate the relationship between the ecological factors and establishment success, two models were fitted with seedling and sapling density as response variables, respectively. Besides log diameter, the models identified different ecological factors as significant for seedling and sapling establishment, i.e., regeneration depends on different factors in different development stages. Seedling density depended on the type of rot, log inclination, and decay stage. Sapling density depended mainly on light availability, cover by bark and moss, the time of tree fall, and the distance between the log surface and the forest floor. A total of 22 polypore fungi were isolated from the wood samples, four of them being threatened species. White- and brown-rot fungi were found in all decay stages. The visual assessment of the type of rot in the field corresponded in only 15% of cases to the type of rot caused by the isolated fungi; hence caution is needed when making field assessments of rot types

Inactivation of viruses and bacteria on strawberries using a levulinic acid plus sodium dodecyl sulfate based sanitizer, taking sensorial and chemical food safety aspects into account

The efficacy of levulinic acid (LVA) in combination with sodium dodecyl sulfate (SDS) in removal of foodbome viruses, enteric bacterial pathogens and their surrogates on fresh strawberries was investigated. Inoculated strawberries were treated with potable water, sodium hypochlorite solution (50 ppm), 0.5% LVA plus 0.5% SDS solution, and 5% LVA plus 2% SDS solution respectively for 2 min, followed by spray-rinsing with potable water. Water washing removed at least 1.0-log of the tested viral and bacterial strains from the strawberries' surfaces. The 50 ppm chlorine wash induced 3.4, 1.5 and 2.1-log reductions for hepatitis A virus (HAV), murine norovirus-1 (MNV-1) and MS2 bacteriophage, respectively. In comparison, the tested bacterial strains showed uniform reductions around 1.6-log CFU/ml. The 0.5% LVA plus 0.5% SDS wash induced 2.7, 1.4 and 2.4-log reductions for HAV, MNV-1 and MS2, which were comparable with the reductions induced by chlorine (P > 0.05). For bacteria, over 2.0-log reductions were obtained for Enterococcus faeciurn, Listeria monocytogenes and Salmonella, while Escherichia coli 0157:H7 and Escherichia coli P1 showed reductions of 1.9 and 1.8-log CFU/ml. Higher concentration of LVA plus SDS showed no significantly higher reductions (P > 0.05). Sensory tests of washed strawberries and chemical residue analysis of LVA on strawberries after washing were also performed. In conclusion, this study demonstrates good performance of 0.5% LVA plus 0.5% SDS to reduce the levels of enteric pathogens if present on strawberries without altering taste and introducing chemical safety issues