Picea Abies Stumps Research Articles

Initial and long-term fungal diversity and occurrence of Heterobasidion spp. in Norway spruce root fragments remaining in soil after stump extraction

ABSTRACT Stump removal is considered as the most effective method to reduce losses caused by root rot fungi, including Heterobasidion root rot. To evaluate the persistence of Heterobasidion spp. in root fragments left on site after stump removal, and to analyse the ecological impact of stump removal, five permanent sample plots were established in Latvia and samples were taken immediately after stump removal and 6 years later. In total, 1008 roots of 200 Picea abies stumps were measured and sampled immediately after stump removal. In total, Heterobasidion was detected in 0.7% of healthy looking roots, 2.0% of discoloured roots and 21.4% of decayed roots. Six years later, a total of 203 root fragments were collected in stump removal areas, and Heterobasidion was isolated from 1.5% of the collected root pieces. Fungal diversity was higher in root fragments collected in sample plots 6 years after stump removal compared with fungal diversity in roots immediately after stump extraction, and the species were significantly different. In conclusion, stump removal could be used in areas heavily infected by root rot fungi, and this method will likely not have a negative effect on the total amount of saproxylic fungi.

Size matters but is big always better? Effectiveness of urea and Phlebiopsis gigantea as treatment against Heterobasidion on Picea abies stumps of variable size

Heterobasidion is a severe threat to coniferous forests in the northern hemisphere. Accurate forest management is needed to safeguard the economic values at stake. In this paper we investigate the efficacy of stump treatment with urea and Phlebiopsis gigantea as control treatment in Norway spruce against airborne Heterobasidion infections. The aim of this study was to examine the infection frequency, i.e. frequency of stumps infected by airborne spores, and efficacy of the stump treatments after performing precommercial thinning and final felling, representing highly variable stump diameters. Today treatment after these cuttings are not standard practice across the world.From a total of 27 Norway spruce stands in the southern and mid-regions of Sweden, five precommercial thinning stands and five final felling stands with infection frequencies higher than an economical threshold for treatment, 20%, were selected. In these stands, the efficacy of stump treatment using urea and P. gigantea against Heterobasidion spp. was assessed on stumps of variable diameter. Wooden discs from stumps were analyzed for airborne infections of Heterobasidion spp. 7–8 weeks after treatment. To evaluate the efficacy of treatments, we used the following three different measurements; infection frequency (proportion of infected stumps), relative infected stump area and number of Heterobasidion colonies per square dm, which were tested using three different statistical models each represented by an efficacy value. Overall, untreated stumps were infected to a higher extent than treated stumps, and most infections were found in untreated stumps from final fellings. Treatment with P. gigantea was more efficient for larger sized stumps than small. In precommercial thinnings, urea performed better and had higher mean efficacy values (92–94%) compared to P. gigantea (59%-72%). In final fellings there were no significant differences between the treatments, both had high efficacy values (urea 95.5–99.8% vs P. gigantea 90–98%).Our findings point at the need for accurate stump treatment after precommercial thinning and final felling, when infection rates are likely to be high. Urea seems to be more effective than the biological control agent P. gigantea in controlling Heterobasidion infections in stumps created in precommercial thinnings. We therefore recommend to use urea in precommercial thinnings if possible. In final fellings either urea or P. gigantea can be used.

Effects of location of Norway spruce (Picea abies) stumps on their colonisation by insects in the mountains

Abstract Tree stumps provide habitat for insect assemblages, which are influenced by various factors. Among these factors, physical and chemical changes of the stumps, fungi developing in the dead wood and stump size are most often reported. However there is limited information about the abundance of insects in stumps that are located on mountains where there are different microclimatic conditions. The studies pointed at the determination whether the location of Picea abies stumps in mountains at different altitudes above sea level and on mountainsides with different sun exposure has an impact on the frequency of insects colonising them. The study was carried out in the Eastern Sudety Mountains situated in south-western Poland. The stumps were in clearcuts located at the altitudes 600–700 m and 900–1000 m above sea level and on southern and northern mountainsides. The insects were collected from 0.05 m2 of bark from each stump and identified to the family, order or species level. The numbers of insects in the stumps were modelled with the use of the Poisson distribution or the negative binomial distribution and the generalised linear models. Picea abies stumps were colonised by insects from 16 families in 3 orders (Coleoptera, Diptera, Hymenoptera) in which the Coleoptera was most frequently represented by the families Cerambycidae, Curculionidae (with the sub-family Scolytinae). In the stumps located at the elevation of 900–1000 m there were 28% more insects than in the stumps at 600–700 m. The stumps located on mountainsides with northern exposure were colonised more abundantly by Cerambycidae. Numbers of Curculionidae in the stumps were affected by altitude. Most Curculionidae were found in the stumps located at the elevation 900–1000 m above sea level. The interaction of altitude and mountainside exposure showed more insects in the stumps at higher altitude, regardless of the mountainside exposure. The results showed that the total number of insects in the stumps was influenced by their location in mountains.

Impact of Trichoderma sp. on the Development of Heterobasidion Annosum in Decayed Understory Picea Abies Stumps

Abstract Heterobasidion annosum (Fr.) Bref. s.l. causes significant economic losses in conifer forests. Therefore, to reduce the spread of the infection surfaces of freshly cut conifer, stumps are commonly treated with biological control agents. Trichoderma sp. shows very strong antagonistic effect against H. annosum in vitro, but relatively few field studies have been conducted. Moreover, most of previous studies examined the impact of Trichoderma sp. on H. annosum in healthy conifer stumps. The aim of our work was to evaluate the effect of Trichoderma sp. against H. annosum in already decayed understory spruce stumps. In total, 75 decayed spruce stumps were surveyed. Part of the spruce stumps were left as a control, and the others were treated with one of two Trichoderma isolates (T472 and T945) belonging to two different species: T. viridescens and T. viride. The occurrence of H. annosum was evaluated 3 and 12 months after treatment. The main results were that the area of previously healthy wood occupied by H. annosum was larger in control stumps in comparison with treated stumps, but the differences were not statistically significant.

Effects of the use of biocontrol agent (Phlebiopsis gigantea) on fungal communities on the surface of Picea abies stumps

One of the main objectives of sustainable forestry policies is to phase out, if possible, the use of chemical agents in forestry. The saprotrophic fungus Phlebiopsis gigantea has for several years been used as a biocontrol agent against the pathogen Heterobasidion annosum sensu lato. This pathogen is the major cause of root rot disease in conifers that results in economic losses estimated at 50 million euros to Finnish forestry industry annually. A major problem is that, although the effectiveness of P. gigantea as a bio-control agent has empirically been shown, the long term biological effect of this fungus on conifer trees as well as on other wood microflora has not been empirically proven. We investigated the impact of P. gigantea treatment on stump mycobiota using 454-pyrosequencing approach as this has not done before. Samples from forest sites pre-treated with P. gigantea for 1, 6 and 13years ago were collected, DNA was isolated and the ITS regions were pyrosequenced. Similarly samples were also collected from untreated stumps within the same forest site over the same period of time. A total of 53,117 fungal sequences were generated by 454-pyrosequencing from 18 wood samples. After data cleaning we had 26,127 sequences representing 49% of the original sequences. Possible impact of the treatment on fungal communities in different study sites was analyzed using Principal Component Analysis (PCA). Also diversity indexes and similarity indexes between controls and treated stumps were calculated. Biocontrol P. gigantea represented 0.43% of all fungal sequences and was found only from stumps after one year post-treatment. The pathogen H. annosum s.l. was not observed in this study. Numbers of different OTUs were always higher in the control stumps. However there was no statistical difference noted between treated and non-treated stumps. Based on our results we can conclude that stump treatment should continue as there is no obvious adverse effect on the other stump mycobiota.

Ecological traps and habitat loss, stump extraction and its effects on saproxylic beetles

Stump storage piles created at stump extraction are stored next to the extraction clear-cuts for 2years. These storage piles may become a trap for saproxylic insects (dependent on dead wood) if they attract many breeding individuals, whose offspring are killed at biofuel processing. Stumps in clear-cuts are also an important habitat for many species and these species could be negatively affected by habitat loss when stumps are extracted.In a field study, we therefore estimated the trap effect for the saproxylic beetle fauna in stump storage piles. We also estimated the habitat loss and population decrease that was the result of stump extraction. Beetle density and habitat amounts were estimated in stump storage piles, extraction clear-cuts, and ordinary clear-cuts. In each of eight (six for piles) replicates, beetles were sampled from ten Norway spruce Picea abies stumps, by means of bark sieving, in each habitat (220 stumps in total).Stump extraction reduced the P. abies stump volume by 76%. The concomitant decrease in beetle community abundance was 70%, a decrease from 9109 to 2692 beetles per hectare. A conservative estimate is that between 5.2% and 23.1% of the beetles “produced” at the stump extraction site were killed at stump pile removal. Our results indicated that the stump storage piles were a severe ecological trap for four individual species. However, a lower community density of beetles in stump storage piles compared to surrounding extraction clear-cuts, indicate that stump storage piles did not constitute a community-wide ecological trap.

Persistence and long-term impact of Rotstop biological control agent on mycodiversity in Picea abies stumps

To prevent infection by the root rot fungi Heterobasidion spp., surfaces of freshly cut Picea abies stumps are sprayed with Rotstop biocontrol agent, which constitutes a spore suspension of a single genotype of the competitive fungus Phlebiopsis gigantea. In Fennoscandia, the agent is applied on 47,000 ha of forestland yearly. The aims of the present work were to estimate the persistence of Rotstop P. gigantea strain and its impact on mycodiversity in 4- to 6-year-old P. abies stumps. Fungal isolation was done from 947 wood samples taken from 130 stumps, 60 of which were Rotstop-treated and 70 were untreated controls. Half of the stumps were 4-year, and another half 6-year-old. 705 fungal strains representing 81 species were isolated. Species richness was lower in Rotstop-treated stumps, both after 4 (by 32%; P = 0.08) and after 6 years (46%; P = 0.01). The majority of species (65–75%) isolated from Rotstop-treated stumps were also found in controls. In 4-year-old Rotstop-treated stumps, the fungal community was dominated by P. gigantea, both in terms of isolated strains and observed fruitbodies. Of P. gigantea isolates, only Rotstop genotypes were found in treated stumps, while control stumps harboured wild strains of the species. In 6-year-old both treated and control stumps, P. gigantea was seldom detected and no fruitbodies were observed. Here, the occurrence of other fungi increased, e.g., Resinicium bicolor, Sistotrema brinkmannii, and Hypholoma capnoides. The pathogen, Heterobasidion spp., was the only basidiomycete with a significantly reduced incidence in Rotstop-treated stumps.

Impact of biological (Rotstop) and chemical (urea) treatments on fungal community structure in freshly cut Picea abies stumps

To control the infections by root rot fungi Heterobasidion spp., surfaces of freshly cut Norway spruce stumps are covered either by a biological (Rotstop; spore suspension of competitive saprotrophic fungus Phlebiopsis gigantea ), or by a chemical (35% aqueous solution of urea) compound. In Fennoscandia, Rotstop and urea are applied, respectively, on 47,000 ha and on 2000 ha of forestland each year. The aim of this work was to assess the impact of biological and chemical control on biodiversity in communities of non-target fungi in freshly cut (7-week-old) stumps. Isolation of fungi to pure culture was accomplished from 402 wood samples taken from 63 stumps, 21 treated with each of the compounds and 21 untreated. The isolations yielded 368 distinct fungal strains representing 47 species. Stump treatment led to decrease of species richness both in Rotstop-treated (by 15%) and in urea-treated (by 19%) stumps. Nevertheless, the stumps subjected to the biological compound were colonized mainly by the same fungi that occurred naturally in untreated stumps (Sorensen similarity indices; S S =0.69; S N =0.68). By contrast, chemical treatment strongly promoted stump colonization by Ascomycetes and Deuteromycetes, led to significant decrease of Zygomycetes, and almost completely eliminated Basidiomycetes (including Heterobasidion spp.). Thus, resemblance to a natural community was low ( S S =0.45; S N =0.34). Rotstop treatment decreased significantly the extent of stump colonization by Heterobasidion spp., and increased that of P. gigantea . All strains of the latter were genetically identical among themselves and to the Rotstop strain. The mechanisms of biological and chemical control, and biodiversity aspects are discussed.

Effects of biological and chemical treatments against Heterobasidion annosum on the microfungal communities of Picea abies stumps

This study describes the effects of biological treatments with Trichoderma harzianum, Hypholoma fasciculare, Phanerochaete velutina, Verticillium bulbillosum and Vuilleminia comedens and chemical treatment with propiconazole against Heterobasidion annosum, on the microfungal communities of Picea abies stumps in a forest in the Alps of northwestern Italy. Immediately after felling, 20 healthy stumps per treatment were sprayed with the treatment preparations and their surface was protected with an autologous wood disk. The controls were 20 untreated stumps covered with an autologous wood disk. Another 20 untreated stumps were left without a wood disk to evaluate disk effects on the naturally occurring mycoflora. The microfungal populations were evaluated after one yr on 27 shavings from each stump. Fifty-seven fungal taxa were isolated, and most were Deuteromycetes. The number of species was generally significantly lower in the treatments respect to the control; T. harzianum treatment reduced the most species, V. bulbillosum the least. Multivariate analyses differentiated four groups of treatments: one comprising the treatments with the three lignovorous Basidiomycetes, one comprising the treatments with V. bulbillosum and the control, one comprising the treatment with propiconazole and the untreated stumps without the wood disk, and one composed of the treatment with T. harzianum only. These findings provide evidence that the pattern of fungal colonization of Picea abies stumps is influenced, sometimes greatly, by the treatments examined. T. harzianum and V. bulbillosum had the greatest and the least effect, respectively, on the naturally occurring mycocenoses.

Effects of Biological and Chemical Treatments against Heterobasidion annosum on the Microfungal Communities of Picea abies Stumps

This study describes the effects of biological treatments with Trichoderma harzianum, Hypholoma fasciculare, Phanerochaete velutina, Verticillium bulbillosum and Vuilleminia comedens and chemical t...