Armillaria species distribution and site relationships in Pinus- and Tsuga-dominated forests in Massachusetts

Abstract

The primary objective of this study was to determine the composition of Armillaria species in northeastern North American Pinus - and Tsuga -dominated forests. This was accomplished by sampling 32 plots at eight sites within pitch pine ( Pinus rigida Mill.), eastern white pine ( Pinus strobus L.), eastern white pine – mixed oak, and eastern hemlock ( Tsuga canadensis (L.) Carr.) forests. In total, 320 isolates were collected from 19 host tree species, with 207 of 320 (65%) of all isolations coming from Pinus and Tsuga. Armillaria solidipes Peck was the most abundant species, making up 188 of 320 (59%) of all isolations, which included 39 isolations from hardwoods. Meanwhile, Armillaria mellea (Vahl) P. Kumm. was collected a total of 27 times from eastern white and pitch pine. These two Armillaria species co-occurred at five of the eight sites sampled. Chi-square analyses showed that incidence of Armillaria species were significantly different by forest type. Pitch pine forests had a higher incidence of A. solidipes (p < 0.001), eastern white pine forests had a higher incidence of A. mellea (p = 0.001), and eastern hemlock forests had a higher incidence of Armillaria gallica Marxm. & Romagn. (p = 0.002) compared with expected values. The distribution of A. solidipes varied significantly by soil drainage and soil type, with a higher incidence on excessively drained (p < 0.001) and loamy sand (p < 0.001) soils.