Kari T. Korhonen

Sensitivity of managed boreal forests in Finland to climate change, with implications for adaptive management

This study investigated the sensitivity of managed boreal forests to climate change, with consequent needs to adapt the management to climate change. Model simulations representing the Finnish territory between 60 and 70° N showed that climate change may substantially change the dynamics of managed boreal forests in northern Europe. This is especially probable at the northern and southern edges of this forest zone. In the north, forest growth may increase, but the special features of northern forests may be diminished. In the south, climate change may create a suboptimal environment for Norway spruce. Dominance of Scots pine may increase on less fertile sites currently occupied by Norway spruce. Birches may compete with Scots pine even in these sites and the dominance of birches may increase. These changes may reduce the total forest growth locally but, over the whole of Finland, total forest growth may increase by 44%, with an increase of 82% in the potential cutting drain. The choice of appropriate species and reduced rotation length may sustain the productivity of forest land under climate change.

Occurrence of heterobasidion annosum in pure and mixed spruce stands in Southern Finland

The distribution of different clones (genotypes) ofHeterobasidion annosum was investigated in 34 clear‐cut pure and mixed Norway spruce stands. The proportion of admixed tree species, mostly birch and Scots pine, varied between 0 and 60%. The total area investigated was 35 ha. H. annosum was isolated from 13.1% of the spruces: the S intersterility group from 11.8% and the P intersterility group from 1.3%. Only 0.7% of the pines and apparently none of the broad‐leaved trees had been attacked by H. annosum. The clones of this fungus were generally small: the mean number of spruces infected by one and the same clone was 1.8. The damage caused by H. annosum to spruce was slightly smaller in mixed stands than in pure spruce stands. However, other factors than the present stand composition proved to be much more decisive for the occurrence of H. annosum.

Cytological evidence for somatic diploidization in dikaryotic cells ofArmillariella mellea

Dikaryotic hyphae isolated from basidiocarps ofArmillariella mellea are unstable in aseptic culture and change into monokaryotic hypae. During monokaryotization the nuclei of a dikaryon fuse and fusion nucleus immediately divides resulting in two uninucleate cells, from which the monokaryotic mycelium originates. Similar fusion of two nuclei takes place in matings of compatible singlespore isolates. It is concluded that the resulting monokaryotic mycelium is diploid.

Combining ALS and NFI training data for forest management planning: a case study in Kuortane, Western Finland.

Forest inventories based on airborne laser scanning (ALS) have already become common practice in the Nordic countries. One possibility for improving their cost effectiveness is to use existing field data sets as training data. One alternative in Finland would be the use of National Forest Inventory (NFI) sample plots, which are truncated angle count (relascope) plots. This possibility is tested here by using a training data set based on measurements similar to the Finnish NFI. Tree species-specific stand attributes were predicted by the non-parametric k most similar neighbour (k-MSN) approach, utilising both ALS and aerial photograph data. The stand attributes considered were volume, basal area, stem number, mean age of the tree stock, diameter and height of the basal area median tree, determined separately for Scots pine, Norway spruce and deciduous trees. The results obtained were compared with those obtained when using training data based on observations from fixed area plots with the same centre point location as the NFI plots. The results indicated that the accuracy of the estimates of stand attributes derived by using NFI training data was close to that of the fixed area plot training data but that the NFI sampling scheme and the georeferencing of the plots can cause problems in practical applications.

Population structure of a novel putative mycovirus infecting the conifer root-rot fungus Heterobasidion annosum sensu lato

We describe a novel putative mycovirus infecting the conifer root-rot fungus Heterobasidion annosum sensu lato. This virus, designated as Heterobasidion RNA virus 6 (HetRV6), is taxonomically distant from all previously known viruses of Heterobasidion species, but somewhat related to the Curvularia thermal tolerance virus and the Fusarium graminearum virus 4. Based on a population analysis including 35 virus strains from Heterobasidion abietinum, Heterobasidion parviporum, Heterobasidion annosum sensu stricto and Heterobasidion occidentale, HetRV6 showed a considerable degree of geographical and host-related differentiation. The North American and Eurasian virus populations were clearly separated. In Eurasia, we observed cases of discrepancy between virus and host taxonomy, suggesting interspecies virus transfer. HetRV6 was also successfully transmitted between the three European species H. abietinum, H. annosum and H. parviporum. Based on growth rate tests on agar plates and spruce stem pieces, HetRV6 seemed to be cryptic or slightly mutualistic to its host.

Inventory by Compartments

Inventory by compartments is the method typically used for acquiring data for traditional forest management planning purposes. It is based on the concept of the forest stand, which is traditionally defined as a geographically contiguous parcel of land whose site type and growing stock is homogenous (e.g. Lihtonen 1959 p. 9, Ilvessalo 1965 p. 159, Davis and Johnson 1987 p. 29, Poso 1994 p. 95). In this context, compartment can almost be considered a synonym for forest stand, but a compartment must be also a suitable cutting unit or treatment unit for silvicultural measures and need not necessarily be as homogenous as a forest stand. Detailed forest management plans cannot be produced without compartment-wise estimates of site characteristics and growing stock and without silvicultural treatment proposals for each compartment. The latter must be made within the field inventory, because otherwise the planner has no way of ensuring that in the optimum solution to the forest management planning problem every compartment will be treated silviculturally in a feasible manner. Models describing forests and forestry in forest management planning packages (e.g. MELA, Siitonen et. al. 1996) are merely simplifications of reality. Sampling theory could be used to estimate the sample size needed to attain a certain required level of accuracy in estimates of growing stock, but if the compartments are small the sample sizes become so large that the inventories will be too expensive. In Nordic countries and in Central Europe, where compartments are rather small, a solution to the problem has been found in terms of a subjective method called “inventory by compartments”, which is partially based on visual assessment of the growing stock. Inventory by compartments will be illustrated in this chapter by describing a Finnish application. The area of forestry land in Finland is about 26 million ha, of which 60% is owned by private persons. All the forests owned by the state or by

Application of nearest‐neighbour regression for generalizing sample tree information

Nearest‐neighbour regression was tested for generalizing sample tree information in data from the national forest inventory of Finland. The following variables were found to be good regressors: stem diameter, mean diameter, density and age of growing stock, and plot location. The nearest‐neighbour estimator appears to maintain the natural variation of the variables to be estimated well. Reliable volume and height estimates can be obtained even when using only one nearest neighbour. Increasing the number of neighbours improves the accuracy of estimates.

Species of Heterobasidion host a diverse pool of partitiviruses with global distribution and interspecies transmission

We investigated the geographic occurrence and genetic diversity of partitiviruses among 247 Heterobasidion specimens representing seven species and originating from Europe, Asia, and North America. Based on sequence analysis, partitiviruses were relatively rare, and occurred only in about 5 % of the Heterobasidion isolates analyzed, constituting a minority (about 28 %) of all virus-infected [double-stranded RNA (dsRNA)-positive] isolates. Altogether ten virus strains were characterized in sequence: one complete genome sequence of 3893 bp, six complete RNA-dependent RNA polymerase sequences of 2000-2033 bp, and three partial polymerase sequences. Based on phylogenetic analysis, the virus strains were assigned into three putative partitivirus species: HetRV1 (Heterobasidion RNA virus 1), HetRV4, and HetRV5. Degenerate consensus primers were designed for RT-PCR detection of these virus species. HetRV1 occurred in five different Heterobasidion species, and resembled the previously described Heterobasidion annosum virus (HaV). Highly similar HetRV1 strains with 98 % nucleotide level similarity were found from H. parviporum (member of the H. annosum species complex) and H. australe (member of the H. insulare complex) growing in the same region in Bhutan. This observation suggests recent virus transmission between these taxonomically distant Heterobasidion species in nature. It was also shown that HetRV1 can be transmitted by mycelial contact between the H. annosum and H. insulare complexes. The two other virus species, HetRV4 and HetRV5, were closely related to the Amasya Cherry Disease-associated mycovirus, to Heterobasidion parviporum partitivirus Fr110B, and also to several plant-infecting alphacryptoviruses. These results are in accordance with the view of a close evolutionary relationship between partitiviruses of plants and fungi.

Phylogeny, divergence time estimation, and biogeography of the genus Heterobasidion (Basidiomycota, Russulales)

There have been several investigations into the genus Heterobasidion, however, differentiation of species in these studies have depended on the gene regions analyzed. Reliable defining of species, establishing species divergence times and establishing species biogeographical distributions have been challenging. Here, we used a multilocus phylogenetic approach and maximum parsimony, maximum likehood, and Bayesian analyses to infer the phylogenetic relationships of Heterobasidion species. In addition, we focused on a fungus fossil-based approach and used the largest subunit of RNA polymerase II-the second subunit of RNA polymerase II (RPB1-RPB2) dataset to perform maximum likelihood-based estimation and Bayesian binary analyses, to assess the divergence and biogeographical distributions of Heterobasidion species. The Heterobasidion annousum/H. insulare species complex clusters in three groups in the phylogenetic analyses. Molecular dating suggests that ancestral Heterobasidion species originated in Eurasia during the Early Miocene, followed by dispersal and speciation to other continents during the Middle Miocene and Early Pliocene. Our data are compatible with the previous viewpoint that H. irregulare and H. occidentale colonized North America via different routes, which has been interpreted as Beringian and Thulean North Atlantic vicariance. In addition, we propose that the occurrence of H. araucariae in the southern Hemisphere was probably due to recent human-mediated introductions. Plate tectonics and long-distance dispersal are the most likely factors that influenced Heterobasidion speciation and biogeography.

The relatedness of the Italian F intersterility group of Heterobasidion annosum with the S group, as revealed by RAPD assay

The PCR technique based upon randomly amplified polymorphic DNA (RAPD) markers using 10-mer oligonucleotide primers was used to investigate the phylogenetic relationships among 33 isolates of Heterobasidion annosum belonging to the intersterility groups F and S. The F isolates originated from Italy, the S isolates from the Italian Alps, northern Europe and North America. The presence or absence of some bands was shown to be population-specific. The North American S group and the European S group differed significantly from each other, but within the latter group there were no significant differences between the Italian S and the northern European S populations, with as much similarity within these populations as between them. More DNA polymorphisms appeared within European F and S groups than in the North American S group. The North American S group appeared to be more closely related to the European S group than to the F group. The isolates of the Italian F. population seemed to be most closely related to the Italian S isolates and then, in decreasing order, to the northern European S and North American S isolates. The order of genetic similarity was inversely correlated with the mating frequency in vitro obtained in an earlier study.