Distribution of fungal foliage and shoot pathogens in a natural Scots pine population in relation to environmental variables

Abstract

The development of fungal diseases within plant populations is simultaneously affected by spatially varying factors, which include environmental variables as well as characteristics of the host population itself. We studied the effects of such variation by investigating the relationships between several environmental factors and the occurrence and abundance of pathogenic fungi (Phacidium infestans L., Gremmeniella abietina (Lagerb.) Morelet, and Lophodermella sulcigena (Rostr.) Höhn) in a naturally regenerated, postfire population of Scots pine (Pinus sylvestris L.) saplings. The fieldwork was carried out in the pristine forest of Kostamuksha Strict Nature Reserve in the Karelian Republic, Russia. The microhabitat as well as the density and height of the saplings were factors that were related to the extent of damage caused by fungal diseases. However, the factors were correlated to the amounts of single pathogen species in different ways. Most obviously, microhabitat was related to the amount of G. abietina, while the amount of P. infestans was positively correlated with the increasing density of the stand. Lophodermella sulcigena was most abundant on tall saplings. Gremmeniella abietina occurred together with the other two fungi less frequently than would be expected from random occurrence, suggesting different ecological requirements or competitive exclusion. Fungal diseases caused considerable mortality and damage in the Scots pine population in question. We suggest that pathogenic fungi affecting shoots and foliage may affect the spatial distribution and regeneration dynamics of natural Scots pine populations.