RESULTS
The results of Cox PH models for the three-year seedling survival
indicate that the HR of O. semicastrata seedling mortality, i.e.,
the risk of mortality under warming, was significantly less than 1
(p = 0.04, Figure 2a), while warming had no significant effect on
the HR of C. patelliormis seedling mortality (p = 0.56,
Figure 2b). Additionally, the HR of O. semicastrata seedling
mortality significantly decreased with increasing distance from their
parent trees (p = 2e-6, Figure 2a) and with pesticide treatment
(p < 2e-16). In contrast, seedlings of the congeneric
tree species, O. pinnata , and the other focal species, C.
patelliformis , which were planted together under O. semicastrataparent trees (Figure 1b), did not respond to pesticide treatment (Figure
S1). Conversely, the mortality HR of C. patelliormis seedlings
significantly increased with distance from their parent trees (p= 0.01, Figure 2b), while pesticide and warming treatments had no effect
on C. patelliormis seedling mortality (p = 0.45 andp = 0.56, respectively, Figure 2b). Similar results were observed
for its congeneric species (C . hui ) and the other focal
species (O. semicastrata ) (Figure S1), whose seedlings were
planted under the same C. patelliormis parent trees (Figure 1b).
Among the fungal OTUs, 41.76% (4093 out of 9802) were identified to the
genus level, and 96.56% of these (3952 out of 4093) were further
successfully grouped into functional guilds, including plant-pathogenic
fungi (10.65%) and EcM fungi (9.92%). OTU9 (Laccaria sp., an
EcM fungus) was the most abundant fungus, contributing 3.94% of the
sequence numbers to the total fungal OTUs. In total, 421 fungal OTUs
were identified as plant-pathogenic fungi.
Warming significantly decreased the relative abundance of
plant-pathogenic fungi (p < 2e-16, Table 1), but
increased that of EcM fungi (p < 2e-16, Table 2). With
the increasing distance from parent trees, the relative abundances of
plant-pathogenic fungi and ECM fungi decreased (p <
2e-16, Tables 1 and 2). Pesticide treatment decreased the relative
abundance of plant-pathogenic fungi (p < 2e-16, Table
1), but increased the relative abundance of EcM fungi (p = 8e-16,
Table 2), which may be responsible for the decreased seedling mortality
of O. semicastrata at pesticide treatment (p <
2e-16, Figure 2a). However, changes in the relative abundance of
plant-pathogenic fungi and the relative abundance of EcM fungi under
warming and pesticide treatments seemed to have no effect on C.
patelliormis seedling mortality (p = 0.45 and p = 0.56,
respectively; Figure 2b), which might suggest that load levels of
plant-pathogenic and EcM fungi are not critical for seedling survival of
EcM fungi-associated tree species (possibly due to the protection of
Hartig nets against pathogens’ attack on roots).