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.

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

Plant communities commonly have both host diversity and biotic diseases (Kimmins 1997a; Roy and Kirchner 2000), but to differing degrees. Disease and diversity are classically connected in the literature by the co-evolutionary explanation of sex (Hamilton 1980): recombinations of the host genome may produce disease-resistant genotypes, while preserving or enhancing diversity (Clay and Kover 1996; Kirchner and Roy 2000; Lively 2001).We argue here that this concept of species interaction has to be viewed in the context of both individuals and populations in order to make sense from the evolutionary (Tokeshi 1999) and forest economy viewpoints (Perry and Amaranthus 1997; Perry 1998). The general importance of disease and parasites in the dynamics of plant populations is well recognized (Harper 1977, 1990; Burdon 1987; Dobson and Crawley 1994; Garrett and Mundt 1999), but studies on disease dynamics in natural multi-species plant communities remain rare (Kranz 1990; Burdon 1993; Roy et al. 2000; Thrall and Burdon 2002). Most forest ecosystems have been altered in their patterns and processes by human influences (Glatzel 1991; Edmonds et al. 2000; Wohlgemuth et al. 2002). Also biotic perturbations, including diseases, are increasingly perceived as an intrinsic part of the system (Ehrlich 1994; Schowalter et al. 1997; Spies and Turner 1999). Trees are an obvious structural component of ecosystems (Jones et al. 1997; Rao et al. 1997), but pathogenic and saprotrophic organisms also form an important part of biodiversity and contribute to the holistic functioning of forests (Ingram 1999; Courtecuisse 2001; Siitonen 2001). We refer here only to fungal pathogens of trees and thus do not focus on abiotic disturbances (Hansen and Rotella 1999; see Dhote, Chap. 14, this vol.), or viruses, bacteria, and insects (Haack and Byler 1993; see Jactel et al., Chap. 12, this vol.), although, in many cases, these may be intimately interrelated with fungal pathogenesis (Hatcher 1995; Lundquist 1995; Maloney and Rizzo 2002).

Susceptibility to Fungal Pathogens of Forests Differing in Tree Diversity

What is the potential for replacing monocultures with mixed-species stands to enhance ecosystem services in boreal forests in Fennoscandia?

https://cyberleninka.org/article/n/659149.pdf

Do foliar fungal communities of Norway spruce shift along a tree species diversity gradient in mature European forests

Summary

A scattered wind fall of 50 trees in a 46-year-old stand of Douglas-fir (Pseudotsuga menziesii) revealed Serpula himantioides, Heterobasidion annosum and Calocera viscosa as decay causing fungi. Sixty-four percent of the stumps had visible rot on the stump surface. Mainly, a central brown rot was seen, caused by either S. himantioides or C. viscosa combined with eccentrically placed spots of incipient H. annosum rot. Subsequently, the appearance of fruitbodies disclosed that in total 76% of the wind thrown trees were associated with one or more of the three decay fungi. S. himantioides was present in a surprisingly large number of trees (54%), and the rot column extended up to 2 m into the stem. This investigation represents the first known incidence of S. himantioides and C. viscosa causing root and butt rot in living conifers in Denmark.

Resume

L'observation de cinquante arbres renverses au hasard par le vent dans un peuplement de 46 ans de Douglas (Pseudotsuga menziesii) a permis de detecter la presence de Serpula himantioides, Heterobasidion annosum et de Calocera viscosa comme agents d'alteration du bois. 64% des souches presentaient une pourriture a leur section. Il s'agissait essentiellement d'une pourriture brune centrale causee par S. himantioides ou C. viscosa, avec en peripherie des taches de pourriture discrete aH. annosum. En outre, l'existence de fructifications a permis d’etablir que 76% des chablis etaient affectes par un ou plusieurs de ces trois agents d'alteration. S. himantioidesetait present chez un grand nombre d'arbres (54%) et l'alteration montait jusqu’a deux metres dans le tronc. Ces observations sont le premier cas connu au Danemark de degâts de pourriture de racines et de coer par S. himantioides et C. viscosa chez des coniferes sur pied.

Zusammenfassung

In einem 46 Jahre alten Douglasienbestand (Pseudotsuga menziesii) wurden die Fauleerreger Serpula himantioides, Heterobasidion annosum und Calocera viscosa an vom Wind geworfenen Baumen festgestellt. 64% der Stumpfe wiesen eine auf der Stumpfoberflache sichtbare Faule auf. Es handelte sich dabei in den meisten Fallen um eine durch S. himantioides oder C. viscosa verursachte Braunfaule mit einsetzender H. annosum-Faule an exzentrisch gelegenen Stellen. Die Bildung von Fruchtkorpern zeigte die Prasenz eines oder mehrerer der drei Fauleerreger an 76% der geworfenen Baume. S. himantioides kam an einer erstaunlich hohen Zahl von Baumen vor (54%), und die Faule erreichte eine Hohe von bis zu 2 m im Stamm. Dies ist der erste Bericht uber durch S. himantioides and C. viscosa verursachte Wurzel- und Kernfaulen in lebenden Koniferen in Danemark.

Serpula himantioides, Heterobasidion annosum and Calocera viscosa as butt rot fungi in a Danish Douglas-fir stand

Butt rot of Picea abies in pure and in mixed stands. On comparable soils, stands with Picea abies and P, abies mixed with other tree species were analysed for butt rot. In mixed stands the percentage of butt rot in P. abies was about the same as in pure stands.

R. Siepmann

Papers

Stammfäuleanteile in Fichtenreinbeständen und in Mischbeständen1