DOI: 10.5061/dryad.231cm
title: Data from: Roles of pathogens on replacement of tree seedlings in heterogeneous light environments in a temperate forest: a reciprocal seed sowing experiment

description: In forest communities, the Janzen–Connell (J-C) hypothesis proposes that
 species diversity is maintained by non-competitive distance- and/or
 density-dependent seedling mortality caused by host-specific natural
 enemies. However, the effects of pathogen associations from nearby
 conspecifics versus heterospecifics remain unknown in spatially
 heterogeneous light environments. Seeds of hardwood species Cornus
 controversa (Cornus) and Prunus grayana (Prunus) were sown beneath 6–7
 Cornus and Prunus adults in both the forest understory (FU) and in gaps
 (Gap) created by felling all woody vegetation near the focal adults.
 Seedling growth, mortality, killing agents (e.g. pathogens that cause
 damping-off and leaf diseases), and root infection by arbuscular
 mycorrhizal fungi (AMF) were investigated. We found strong habitat effects
 on the expression of soil fungi beneath both tree species. Seedling
 mortality caused by soil-borne damping-off pathogens was greater in FU
 than in Gap, and AMF infection, which enhanced relative seedling growth
 rate, was greater in Gap than in FU. Seedling mortality caused by
 damping-off pathogens did not differ between Cornus and Prunus seedlings
 beneath the adults of conspecific or heterospecific adults in both FU and
 Gap, suggesting little distance-dependence or host preference in the
 fungus. Beneath the adults of Cornus and Prunus, the most prevalent leaf
 diseases were zonate leaf blight and angular leaf spot caused by the
 airborne pathogenic fungi Haradamyces foliicola and Phaeoisariopsis
 pruni-grayanae, respectively. Although these pathogens attacked the
 seedlings of both species, conspecific seedlings (i.e. home) showed more
 severe leaf damage, earlier leaf shedding and/or less defensive behaviour
 (cell wall defence) relative to heterospecific seedlings (i.e. away),
 suggesting negative distance-dependent attack (i.e. host preference) for
 these leaf diseases. As a result, greater seedling mortality was observed
 for conspecific seedlings under both FU and Gap treatments. Synthesis. In
 the temperate forest, the J-C hypothesis is largely mediated through the
 strong negative influence of airborne leaf diseases rather than through
 soil-borne damping-off pathogens. We found that airborne diseases
 demonstrated distance-dependent host preferences, which led to greater
 conspecific seedling damage regardless of environmental light conditions.
description: Bayandala
 dataTable S1. Environmental
 conditions in the forest understory and gaps beneath adults of Cornus
 controversa and Prunus grayana. Table S2. Causes of seedling mortality (%)
 during the 2011 growing season in the forest understory (FU) and gap (Gap)
 beneath C. controversa and P. grayana adults in the reciprocal seed-sowing
 experiment. Table.S3-1. Proportion (%) of leaves damaged by zonate leaf
 blight, number of leaves attached to a seedling, proportion of seedlings
 showing cell wall defence against zonate leaf blight beneath adults of
 Cornus controversa. Table S3-2. Proportion (%) of leaf area damaged by
 angular leaf spot and the number of leaves attached to a seedling for both
 species in the forest understorey (FU) and gaps (Gap) beneath adults of
 Prunus grayana. Table S4. Seedling mass (g), RGR (g g-1 day-1) and percent
 infection of AMF (%) of Cornus controversa and Prunus grayana seedlings
 beneath the adults of each of the two species in forest understory (FU)
 and gaps (GAP)Dryad-raw data
 .xlsx