Figure legends
Figure
1 . Abundance of nematode trophic groups as affected by N treatments and
soil depth. Treatment and soil depth from two-way ANOVA are provided in
each subpanel. Within each depth, different lowercase letters indicate
significant differences of means (P < 0.05) under a LSD
test among N treatments. Bars indicate standard errors of means
(n = 3).
Figure
2. The diversity of soil nematodes as affected by N treatments and soil
depth. Treatment and soil depth from two-way ANOVA are provided in each
subpanel. Different uppercase letters indicate significant differences
of means (P < 0.05) under a LSD test among soil depths.
Bars indicate standard errors of means (n = 3).
Figure 3. Ecological indices of soil nematodes as affected by N
treatments and soil depth. Treatment and soil depth from two-way ANOVA
are provided in each subpanel. Within each depth, different lowercase
letters indicate significant differences of means (P <
0.05) under a LSD test among N treatments. Bars indicate standard errors
of means (n = 3).
Figure 4. The co-occurrence networks of nematode genera
under
different N treatments (a) and the robustness of nematode genera
networks under different treatments (b). The size of each node indicates
the proportion of total nematode abundance represented by the indicated
genus. BF: bacterial-feeding nematodes; FF: fungal-feeding nematodes;
PF: plant-feeding nematodes; OP: omnivorous-predatory nematodes.
Figure 5. Structural equation model (SEM) examining the direct
and indirect effects of N addition on nematode trophic groups (a) and
the standardized total effects
(direct plus indirect effects) of each nematode trophic group derived
from the SEM (b-e). Black and red
lines indicate positive and negative effects, respectively. Line
thickness in SEM indicates the strength of significant path coefficient
and gray lines present the non-significant paths. Values associated with
arrows are standardized path coefficients. r 2values linked with response variables indicate the proportion of
variation explained by relationships with other variables. PCT: the
first component of TC, TN and TP determined by principal component
analysis; PCA: the first component of AP,
NO3+-N and
NH4+-N determined by principal
component analysis; FF: fungal-feeding nematodes; BF: bacterial-feeding
nematodes; PF: plant-feeding nematodes; OP: omnivorous-predatory
nematodes. ***P < 0.001, **P < 0.01,
*P < 0.05, n = 36.