Browsing by Subject "PICEA-ABIES"

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  • White, Joanne C.; Saarinen, Ninni; Wulder, Michael A.; Kankare, Ville; Hermosilla, Txomin; Coops, Nicholas C.; Holopainen, Markus; Hyyppä, Juha; Vastaranta, Mikko (2019)
    Information regarding the nature and rate of forest recovery is required to inform forest management, monitoring, and reporting activities. Delayed establishment or return of forests has implications to harvest rotations and carbon uptake, among others, creating a need for spatially-explicit, large-area, characterizations of forest recovery. Landsat time series (LTS) has been demonstrated as a means to quantitatively relate forest recovery, noting that there are gaps in our understanding of the linkage between spectral measures of forest recovery and manifestations of forest structure and composition. Field plots provide a means to better understand the linkage between forest characteristics and spectral recovery indices. As such, from a large set of existing field plots, we considered the conditions present for the year in which the co-located pixel was considered spectrally recovered using the Years to Recovery (Y2R) metric. Y2R is a long-term metric of spectral recovery that indicates the number of years required for a pixel to return to 80% of its pre-disturbance Normalized Burn Ratio value. Absolute and relative metrics of recovery at 5 years post-disturbance were also considered. We used these three spectral recovery metrics to predict the stand development class assigned by the field crew for 284 seedling plots with an overall accuracy of 73.59%, with advanced seedling stands more accurately discriminated (omission error, OE = 15.74%) than young seedling stands (OE = 49.84%). We then used field-measured attributes (e.g. height, stem density, dominant species) from the seedling plots to classify the plots into three spectral recovery groups, which were defined using the Y2R metric: spectral recovery in (1) 1–5 years, (2) 6–10 years, or (3) 11–15 years. Overall accuracy for spectral recovery groups was 61.06%. Recovery groups 1 and 3 were discriminated with greater accuracy (producer’s and user’s accuracies > 66%) than recovery group 2 (<50%). The top field-measured predictors of spectral recovery were mean height, dominant species, and percentage of stems in the plot that were deciduous. Variability in stand establishment and condition make it challenging to accurately discriminate among recovery rates within 10 years post-harvest. Our results indicate that the long-term metric Y2R relates to forest structure and composition attributes measured in the field and that spectral development post-disturbance corresponds with expectations of structural development, particularly height, for different species, site types, and deciduous abundance. These results confirm the utility of spectral recovery measures derived from LTS data to augment landscape-level assessments of post-disturbance recovery.
  • Vehkaoja, Mia; Nummi, Petri; Rikkinen, Jouko (2017)
    Beavers are ecosystem engineers that modify and maintain a range of special habitat types in boreal forests. They also produce large quantities of deadwood that provide substrate for many lignicolous organisms such as calicioid fungi (Ascomycota). We studied how calicioid diversity differed between boreal riparian forests with and without beaver activity. The results show that calicioid diversity were significantly higher at beaver sites compared to the other two forest site types studied. The large quantity and diverse forms of deadwood produced by beavers clearly promotes calicioid diversity in the boreal landscape. The specific lighting and humidity conditions within beaver wetlands could be the reason why they promote the success of certain calicioid species.
  • Metsämuuronen, Sari; Sirén, Heli (2019)
    Phenolics and extracted phenolic compounds of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) show antibacterial activity against several bacteria. The majority of phenolic compounds are stilbenes, flavonoids, proanthocyanidins, phenolic acids, and lignans that are biosynthesized in the wood through the phenylpropanoid pathway. In Scots pine (P. sylvestris), the most abundant phenolic and antibacterial compounds are pinosylvin-type stilbenes and flavonol- and dihydroflavonol-type flavonoids, such as kaempferol, quercetin, and taxifolin and their derivatives. In Norway spruce (P. abies) on the other hand, the main stilbene is resveratrol and the major flavonoids are quercetin and myricetin. In general, when the results from the literature regarding the activities of flavonoid glycosides and their aglycones against a total of twenty-one microorganisms are summarized, it was found that phenolic glycosides are less active than the corresponding aglycones, although a number of exceptions are also known. The aglycones in plants respond to various kinds of biotic stress. Synergistic effects between aglycones and their glycosides have been observed. Minimum inhibition concentrations of below 10 mg L−1 against bacteria have been reported for gallic acid, apigenin, and several methylated and acylated flavonols present in these industrially important trees. In general, the phenolic compounds are more active against Gram-positive bacteria, but apigenin is reported to exhibit strong activity against Gram-negative bacteria. The present review lists some of the biosynthesis pathways for the antibacterial phenolic metabolites found in Scots pine (P. sylvestris) and Norway spruce (P. abies). The antimicrobial activity of the compounds is collected and compared to gather information about the most effective secondary metabolites.
  • Lintunen, Anna; Lindfors, Lauri; Kolari, Pasi; Juurola, Eija; Nikinmaa, Eero; Hölttä, Tuomo (2014)
  • Kovalchuk, Andriy; Zeng, Zhen; Ghimire, Rajendra P.; Kivimäenpää, Minna; Raffaello, Tommaso; Liu, Mengxia; Mukrimin, Mukrimin; Kasanen, Risto Aarne Olavi; Sun, Hui; Julkunen-Tiitto, Riitta; Holopainen, Jarmo K.; Asiegbu, Frederick Obioma (2019)
    BackgroundRoot and butt rot of conifer trees caused by fungi belonging to the Heterobasidion annosum species complex is one of the most economically important fungal diseases in commercial conifer plantations throughout the Northern hemisphere. We investigated the interactions between Heterobasidion fungi and their host by conducting dual RNA-seq and chemical analysis on Norway spruce trees naturally infected by Heterobasidion spp. We analyzed host and pathogen transcriptome and phenolic and terpenoid contents of the spruce trees.ResultsPresented results emphasize the role of the phenylpropanoid and flavonoid pathways in the chemical defense of Norway spruce trees. Accumulation of lignans was observed in trees displaying symptoms of wood decay. A number of candidate genes with a predicted role in the higher level regulation of spruce defense responses were identified. Our data indicate a possible role of abscisic acid (ABA) signaling in the spruce defense against Heterobasidion infection. Fungal transcripts corresponding to genes encoding carbohydrate- and lignin-degrading enzymes, secondary metabolism genes and effector-like genes were expressed during the host colonization.ConclusionsOur results provide additional insight into defense strategies employed by Norway spruce trees against Heterobasidion infection. The potential applications of the identified candidate genes as markers for higher resistance against root and butt rot deserve further evaluation.
  • Saine, Sonja; Aakala, Tuomas; Purhonen, Jenna; Launis, Annina; Tuovila, Hanna; Kosonen, Timo; Halme, Panu (2018)
    Human-induced fragmentation affects forest continuity, i.e. availability of a suitable habitat for the target species over a time period. The dependence of wood-inhabiting fungi on landscape level continuity has been well demonstrated, but the importance of local continuity has remained controversial. In this study, we explored the effects of local forest continuity (microhabitat and stand level) on the diversity of wood-inhabiting fungi on standing dead trunks of Scots pine (Paws sylvestris L.). We studied species richness and community composition of decomposers and Micarea lichens on 70 trunks in 14 forests in central Finland that differed in their state of continuity. We used dendrochronological methods to assess the detailed history of each study trunk, i.e. the microhabitat continuity. The stand continuity was estimated as dead wood diversity and past management intensity (number of stumps). We recorded 107 species (91 decomposers, 16 Micarea lichens), with a total of 510 occurrences. Using generalized linear mixed models, we found that none of the variables explained decomposer species richness, but that Micarea species richness was positively dependent on the time since tree death. Dead wood diversity was the most important variable determining the composition of decomposer communities. For Micarea lichens, the community composition was best explained by the combined effect of years from death, site and dead wood diversity. However, these effects were rather tentative. The results are in line with those of previous studies suggesting the restricted significance of local forest continuity for wood-inhabiting fungi. However, standing dead pines that have been available continuously over long periods seem to be important for species-rich communities of Micarea lichens. Rare specialists (e.g. on veteran trees) may be more sensitive to local continuity, and should be at the center of future research.
  • Linnakoski, Riikka; Sugano, Junko; Junttila, Samuli; Pulkkinen, Pertti; Asiegbu, Fred O.; Forbes, Kristian M. (2017)
    Norway spruce is one of the most important commercial forestry species in Europe, and is commonly infected by the bark beetle-vectored necrotrophic fungus, Endoconidiophora polonica. Spruce trees display a restricted capacity to respond to environmental perturbations, and we hypothesized that water limitation will increase disease severity in this pathosystem. To test this prediction, 737 seedlings were randomized to high (W+) or low (W-) water availability treatment groups, and experimentally inoculated with one of three E. polonica strains or mock-inoculated. Seedling mortality was monitored throughout an annual growing season, and total seedling growth and lesion length indices were measured at the experiment conclusion. Seedling growth was greater in the W+ than W- treatment group, demonstrating limitation due to water availability. For seedlings infected with two of the fungal strains, no differences in disease severity occurred in response to water availability. For the third fungal strain, however, greater disease severity (mortality and lesion lengths) occurred in W- than W+ seedlings. While the co-circulation in nature of multiple E. polonica strains of varying virulence is known, this is the first experimental evidence that water availability can alter strain-specific disease severity.
  • Mukrimin, Mukrimin; Conrad, Anna O.; Kovalchuk, Andriy; Julkunen-Tiitto, Riitta; Bonello, Pierluigi; Asiegbu, Fred O. (2019)
    Conifer trees, including Norway spruce, are threatened by fungi of the Heterobasidion annosum species complex, which severely affect timber quality and cause economic losses to forest owners. The timely detection of infected trees is complicated, as the pathogen resides within the heartwood and sapwood of infected trees. The presence of the disease and the extent of the wood decay often becomes evident only after tree felling. Fourier-transform infrared (FT-IR) spectroscopy is a potential method for non-destructive sample analysis that may be useful for identifying infected trees in this pathosystem. We performed FT-IR analysis of 18 phloem, 18 xylem, and 18 needle samples from asymptomatic and symptomatic Norway spruce trees. FT-IR spectra from 1066 – 912 cm−1 could be used to distinguish phloem, xylem, and needle tissue extracts. FT-IR spectra collected from xylem and needle extracts could also be used to discriminate between asymptomatic and symptomatic trees using spectral bands from 1657 – 994 cm−1 and 1104 – 994 cm−1, respectively. A partial least squares regression model predicted the concentration of condensed tannins, a defense-related compound, in phloem of asymptomatic and symptomatic trees. This work is the first to show that FT-IR spectroscopy can be used for the identification of Norway spruce trees naturally infected with Heterobasidion spp.
  • Mukrimin, Mukrimin; Kovalchuk, Andriy; Neves, Leandro G.; Jaber, Emad H. A.; Haapanen, Matti; Kirst, Matias; Asiegbu, Fred O. (2018)
    Root and butt rot caused by members of the Heterobasidion annosum species complex is the most economically important disease of conifer trees in boreal forests. Wood decay in the infected trees dramatically decreases their value and causes considerable losses to forest owners. Trees vary in their susceptibility to Heterobasidion infection, but the genetic determinants underlying the variation in the susceptibility are not well-understood. We performed the identification of Norway spruce genes associated with the resistance to Heterobasidion parviporum infection using genome-wide exon-capture approach. Sixty-four clonal Norway spruce lines were phenotyped, and their responses to H. parviporum inoculation were determined by lesion length measurements. Afterwards, the spruce lines were genotyped by targeted resequencing and identification of genetic variants (SNPs). Genome-wide association analysis identified 10 SNPs located within 8 genes as significantly associated with the larger necrotic lesions in response to H. parviporum inoculation. The genetic variants identified in our analysis are potential marker candidates for future screening programs aiming at the differentiation of disease-susceptible and resistant trees.
  • Lopez, Jose Gutierrez; Tor-Ngern, Pantana; Oren, Ram; Kozii, Nataliia; Laudon, Hjalmar; Hasselquist, Niles J. (2021)
    Trees in northern latitude ecosystems are projected to experience increasing drought stress as a result of rising air temperatures and changes in precipitation patterns in northern latitude ecosystems. However, most drought-related studies on high-latitude boreal forests (>50 degrees N) have been conducted in North America, with few studies quantifying the response in European and Eurasian boreal forests. Here, we tested how daily whole-tree transpiration (Q, Liters day(-1)) and Q normalized for mean daytime vapor pressure deficit (Q(DZ), Liters day(-1) kPa(-1)) were affected by the historic 2018 drought in Europe. More specifically, we examined how tree species, size, and topographic position affected drought response in high-latitude mature boreal forest trees. We monitored 30 Pinus sylvestris (pine) and 30 Picea abies (spruce) trees distributed across a topographic gradient in northern Sweden. In general, pine showed a greater Q(DZ) control compared to spruce during periods of severe drought (standardized precipitation-evapotranspiration index: SPEI <-1.5), suggesting that the latter are more sensitive to drought. Overall, Q(DZ) reductions (using non-drought Q(DZ) as reference) were less pronounced in larger trees during severe drought, but there was a species-specific pattern: Q(DZ) reductions were greater in pine trees at high elevations and greater in spruce trees at lower elevations. Despite lower Q(DZ) during severe drought, drought spells were interspersed with small precipitation events and overcast conditions, and Q(DZ) returned to pre-drought conditions relatively quickly. This study highlights unique species-specific responses to drought, which are additionally driven by a codependent interaction among tree size, relative topographic position, and unique regional climate conditions.
  • Stivrins, Normunds; Aakala, Tuomas; Ilvonen, Liisa; Pasanen, Leena; Kuuluvainen, Timo; Vasander, Harri; Galka, Mariusz; Disbrey, Helena R.; Liepins, Janis; Holmstrom, Lasse; Seppa, Heikki (2019)
    Fire is a major disturbance agent in the boreal forest, influencing many current and future ecosystem conditions and services. Surprisingly few studies have attempted to improve the accuracy of fire-event reconstructions even though the estimates of the occurrence of past fires may be biased, influencing the reliability of the models employing those data (e.g. C stock, cycle). This study aimed to demonstrate how three types of fire proxies - fire scars from tree rings, sedimentary charcoal and, for the first time in this context, fungal spores of Neurospora - can be integrated to achieve a better understanding of past fire dynamics. By studying charcoal and Neurospora from sediment cores from forest hollows, and the fire scars from tree rings in their surroundings in the southern Fennoscandian and western Russian boreal forest, we produced composite fire-event data sets and fire-event frequencies, and estimated fire return intervals. Our estimates show that the fire return interval varied between 126 and 237 years during the last 11,000 years. The highest fire frequency during the 18th-19th century can be associated with the anthropogenic influence. Importantly, statistical tests revealed a positive relationship between other fire event indicators and Neurospora occurrence allowing us to pinpoint past fire events at times when the sedimentary charcoal was absent, but Neurospora were abundant. We demonstrated how fire proxies with different temporal resolution can be linked, providing potential improvements in the reliability of fire history reconstructions from multiple proxies.
  • Honkaniemi, Juha; Ojansuu, Risto; Kasanen, Risto; Heliövaara, Kari (2018)
    Interaction of disturbance agents may cause cascading effects in forests. The three most important disturbance agents of Norway spruce (Picea abies) in northern Europe are Heterobasidion root rot, wind and the European spruce bark beetle (Ips typographus). In this study, we present a mechanistic individual agent based model to simulate the dynamics of the bark beetle and integrate it in the simulation framework WINDROT to further study the interactive dynamics of root rot, wind and bark beetles. We carried out model performance analysis concluding that the model is sensitive to the parameters of optimal bark thickness for reproduction. Stand level interaction between wind and bark beetle disturbances was also evaluated against field data. The stand level simulations show the interaction between the disturbance agents; the root rot increases wind disturbance and bark beetles benefit from wind fallen trees. No direct interaction was found in the simulation study between the root rot and bark beetles. Further experimental research and large scale simulation studies are needed to better understand the underlying mechanisms in the interaction between the disturbance agents.
  • Paljakka, Teemu; Rissanen, Kaisa; Vanhatalo, Anni; Salmon, Yann; Jyske, Tuula; Prisle, Nonne L.; Linnakoski, Riikka; Lin, Jack J.; Laakso, Tapio; Kasanen, Risto; Back, Jaana; Holtta, Teemu (2020)
    Increased abiotic stress along with increasing temperatures, dry periods and forest disturbances may favor biotic stressors such as simultaneous invasion of bark beetle and ophiostomatoid fungi. It is not fully understood how tree desiccation is associated with colonization of sapwood by fungi. A decrease in xylem sap surface tension (sigma(xylem)) as a result of infection has been hypothesized to cause xylem embolism by lowering the threshold for air-seeding at the pits between conduits and disruptions in tree water transport. However, this hypothesis has not yet been tested. We investigated tree water relations by measuring the stem xylem hydraulic conductivity (K-stem), sigma(xylem), stem relative water content (RWCstem), and water potential (psi(stem)), and canopy conductance (g(canopy)), as well as the compound composition in xylem sap in Norway spruce (Picea abies) saplings. We conducted our measurements at the later stage ofEndoconidiophora polonicainfection when visible symptoms had occurred in xylem. Saplings of two clones (44 trees altogether) were allocated to treatments of inoculated, wounded control and intact control trees in a greenhouse. The saplings were destructively sampled every second week during summer 2016. sigma(xylem), K(stem)and RWC(stem)decreased following the inoculation, which may indicate that decreased sigma(xylem)resulted in increased embolism. g(canopy)did not differ between treatments indicating that stomata responded to psi(stem)rather than to embolism formation. Concentrations of quinic acid, myo-inositol, sucrose and alkylphenol increased in the xylem sap of inoculated trees. Myo-inositol concentrations also correlated negatively with sigma(xylem)and K-stem. Our study is a preliminary investigation of the role of sigma(xylem)inE. polonicainfected trees based on previous hypotheses. The results suggest thatE. polonicainfection can lead to a simultaneous decrease in xylem sap surface tension and a decline in tree hydraulic conductivity, thus hampering tree water transport.
  • Jyske, Tuula; Kuroda, Katsushi; Kerio, Susanna; Pranovich, Andrey; Linnakoski, Riikka; Hayashi, Noriko; Aoki, Dan; Fukushima, Kazuhiko (2020)
    To understand the positional and temporal defense mechanisms of coniferous tree bark at the tissue and cellular levels, the phloem topochemistry and structural properties were examined after artificially induced bark defense reactions. Wounding and fungal inoculation withEndoconidiophora polonicaof spruce bark were carried out, and phloem tissues were frequently collected to follow the temporal and spatial progress of chemical and structural responses. The changes in (+)-catechin, (-)-epicatechin, stilbene glucoside, and resin acid distribution, and accumulation patterns within the phloem, were mapped using time-of-flight secondary ion mass spectrometry (cryo-ToF-SIMS), alongside detailed structural (LM, TEM, SEM) and quantitative chemical microanalyses of the tissues. Our results show that axial phloem parenchyma cells of Norway spruce contain (+)-catechins, the amount of which locally increases in response to fungal inoculation. The preformed, constitutive distribution and accumulation patterns of (+)-catechins closely follow those of stilbene glucosides. Phloem phenolics are not translocated but form a layered defense barrier with oleoresin compounds in response to pathogen attack. Our results suggest that axial phloem parenchyma cells are the primary location for (+)-catechin storage and synthesis in Norway spruce phloem. Chemical mapping of bark defensive metabolites by cryo-ToF-SIMS, in addition to structural and chemical microanalyses of the defense reactions, can provide novel information on the local amplitudes and localizations of chemical and structural defense mechanisms and pathogen-host interactions of trees.
  • Raatevaara, Antti; Korpunen, Heikki; Mäkinen, Harri; Uusitalo, Jori (2020)
    In cut-to-length logging, the harvester operator adjusts the bucking in accordance with visible defects on processed stems. Some of the defects, such as a sweep on the bottom of the stem, decrease the yield and quality of sawn products and are difficult for the operator to notice. Detecting the defects with improved sensors would support the operator in his qualitative decision-making and increase value recovery of logging. Predicting the maximum bow height of the bottom log in Norway spruce (Picea abies (L.) Karst.) with log end face image and stem taper was investigated with two modelling approaches. A total of 101 stems were selected from five clear-cut stands in southern Finland. The stems were crosscut and taper measured, and the butt ends of the bottom logs were photographed. The stem diameter, out-of-roundness, and pith eccentricity were measured from the images while the max. bow height was measured by a 3D log scanner at a sawmill. The bottom logs with an eccentric pith had higher max. bow height. In addition, a highly conical bottom part of the stem was more common on the bottom logs with a large max. bow height. Applying both log end face image and stem taper measurements gave the best model fit and detection accuracy (76%) for bottom logs with a large max. bow height. The results indicate that the log end face image and stem taper measurements can be utilised to aid harvester operator in deciding an optimised length for logs according to the bow height.
  • Uimari, Anne; Heliövaara, Kari; Tuba, Katalin; Poteri, Marja; Vuorinen, Martti (2018)
    Several young damaged Norway spruce stands in eastern and central Finland were observed from 2013 to 2016. The damage included trees with heavy resin flow, necrotic foliage, stem and branch cankers and dead trees. Pest identification resulted in the tortricid moth Cydia pactolana whose occurrence was always associated with the presence of the ascomycete pathogen Neonectria fuckeliana. Both the insect and the disease contributed to the extent of the damage, but it is not possible to say in which order they had attacked the trees. Apparently, changed climate has affected the increased occurrence of both the fungus and the moth. However, the characteristics of the insect-fungus interaction and the factors contributing to the coincidences are unknown. Emerging coexistence or potential symbiosis of the two damaging agents is a serious threat for Norway spruce cultivation. Understanding the biology of this fungus-insect interaction is important for controlling them.
  • Jokinen, Janne J.; Sipponen, Arno (2016)
    Significance: The treatment of chronic wounds results in an enormous drain on healthcare resources in terms of workload, costs, frustration, and impaired quality of life, and it presents a clinical challenge for physicians worldwide. Effective local treatment of a chronic wound has an important role, particularly in patients who arebecause of their poor general condition, diminished life expectancy, or unacceptable operative riskoutside of surgical treatment. Recent Advances: Since 2002, our multidisciplinary research group has investigated the properties of Norway spruce (Picea abies) resin in wound healing and its therapeutic applications in wound care. Resin is a complex mixture of resin acids (e.g., abietic, neoabietic, dehydroabietic, pimaric, isopimaric, levopimaric, sandrakopimaric, and palustric acids) and lignans (e.g., pino-, larici-, matairesinol, and p-hydroxycinnamic acid) having substantial antimicrobial, wound-healing, and skin regeneration enhancing properties. Critical Issues: The cornerstone in successful wound care is an efficient causal treatment of the underlying co-morbidities, for example, diabetes, malnutrition, vascular- or certain systemic diseases. However, definitive diagnosis and specific therapy of a chronic wound is often difficult, because the etiology is practically always multi-factorial, and in the chronic phase, confounding factors such as infections invariably impede wound healing. Future Directions: To study the exact molecular mechanism of actions by which resin promotes cellular regeneration and epithelialization during the wound-healing process. To investigate potential antimicrobial properties of resin against the most ominous multidrug-resistant beta-lactamase (including carbapenemases and metallo--lactamases) producing bacteria, and to individualize those pharmacologically active compounds which are responsible for the antimicrobial activity of resin.
  • Näsi, Roope; Honkavaara, Eija; Blomqvist, Minna; Lyytikäinen-Saarenmaa, Päivi Marja Emilia; Hakala, Teemu; Viljanen, Niko; Kantola, Tuula Anneli; Holopainen, Markus Edvard (2018)
    Climate-related extended outbreaks and range shifts of destructive bark beetle species pose a serious threat to urban boreal forests in North America and Fennoscandia. Recent developments in low-cost remote sensing technologies offer an attractive means for early detection and management of environmental change. They are of great interest to the actors responsible for monitoring and managing forest health. The objective of this investigation was to develop, assess, and compare automated remote sensing procedures based on novel, low-cost hyperspectral imaging technology for the identification of bark beetle infestations at the individual tree level in urban forests. A hyperspectral camera based on a tunable Fabry-Perot interferometer was operated from a small, unmanned airborne vehicle (UAV) platform and a small Cessna-type aircraft platform. This study compared aspects of using UAV datasets with a spatial extent of a few hectares (ha) and a ground sample distance (GSD) of 10-12 cm to the aircraft data covering areas of several km(2) and having a GSD of 50 cm. An empirical assessment of the automated identification of mature Norway spruce (Picea abies L. Karst.) trees suffering from infestation (representing different colonization phases) by the European spruce bark beetle (Ips typographus L.) was carried out in the urban forests of Lahti, a city in southern Finland. Individual spruces were classified as healthy, infested, or dead. For the entire test area, the best aircraft data results for overall accuracy were 79% (Cohen's kappa: 0.54) when using three crown color classes (green as healthy, yellow as infested, and gray as dead). For two color classes (healthy, dead) in the same area, the best overall accuracy was 93% (kappa: 0.77). The finer resolution UAV dataset provided better results, with an overall accuracy of 81% (kappa: 0.70), compared to the aircraft results of 73% (kappa: 0.56) in a smaller sub-area. The results showed that novel, low-cost remote sensing technologies based on individual tree analysis and calibrated remote sensing imagery offer great potential for affordable and timely assessments of the health condition of vulnerable urban forests.
  • Linnakoski, Riikka Marjaana; Mahilainen, Saila; Harrington, Alison; Vanhanen, Henri; Eriksson, Miikka; Mehtätalo, Lauri; Pappinen, Ari; Wingfield, Michael J. (2016)
    The ophiostomatoid fungi (Microascales and Ophiostomatales, Ascomycota) are common associates of Ips typographus, and include tree pathogens and species responsible for blue-stain of timber. Fungal assemblages associated with I. typographus have varied considerably between studies but few investigations have attempted to explain this variation. For this reason, we assessed the overall cultivable fungal diversity associated with I. typographus in a storm-felled spruce forest in south-eastern Finland. Fungi were isolated from the individually collected beetles as well as their phoretic mites in spring, summer and autumn, including different life stages of the beetle (hibernation, dispersal flight and first generation). The internal transcribed spacer (ITS) gene region was used to identify the fungi. A total of 32 operational taxonomic units (OTUs) were found and these resided in four fungal phyla/subphyla (24 Ascomycota, 2 Basidiomycota, 5 Mucoromycotina, 1 Mortierellomycotina) in association with adult bark beetles. Ophiostomatoid species were the most commonly detected fungal associates. A generalized linear model analysis showed a clear association between fungal communities and season, indicating seasonal succession among I. typographus-associated fungi. The season of sampling appears to be an important factor that has resulted in inconsistencies between results in previous studies. Many of these fungi were also found on phoretic mites and their presence or absence could have influenced variation in patterns of association.