The Frequency, Magnitude and Spatial Distribution of Heart Rot in
Dominant Temperate Tree Species in a Forest Dynamics Plot
Abstract
1. The composition, dynamics and health of forest tree communities are
governed by interactions with the abiotic and biotic environment. Fungi
are critical biotic interactors that play and increasingly appreciated
role in forest tree health particularly with respect to mycorrhizal and
pathogenic fungi. Heart rot fungi, while known infect large fractions of
the individuals in managed stands, have been considerably understudied
in tree community ecology. Heart rot has been predicted to form hotspots
in the forest due to crown or bole damage and/or soil moisture gradients
and is expected to vary across species due to life history differences.
2. To address this knowledge gap, we quantified heart rot the incidence,
magnitude and spatial distribution of heart rot in 328 individuals with
diameters greater than or equal to 10 cm across the six most dominant
tree species in a mixed broadleaf temperate forest dynamics plot. 3. The
results show that 71% of individuals display some degree of heart rot
in this natural community. The incidence of heart rot does not
significantly vary across species despite their life history strategy
differences, but one species had significantly more heart rot in
infected individuals. Lastly, heart rot was spatially clustered across
species, but heart rot incidence and magnitude were not related to soil
moisture indicating the importance of crown and bole breakage likely
promoted by severe weather. Summary The present study conducted the
first spatially explicit study of heart rot incidence and magnitude in a
natural forest tree community. We demonstrate that over two thirds of
every large tree in the forest studied have some degree of heart rote
indicating their widespread, but underappreciated, role in tree
communities. We demonstrate that heart rot is non-randomly distributed
in this community and that spatial clustering of heart rot in forests is
most likely due hotspots of individual tree damage and not gradients in
soil moisture.