Taxonomic and functional characteristics of communities
Based on the fuzzy-weighted species composition, the grassland
communities were classified into five groups, which form a functional
gradient from groups G1 to G5 (Figure 2). At one end group G1 comprises
communities with high LDMC, LA and predominantly C4species, whereas at the other end group G5 represents communities with
high SLA, leaf N and predominantly C3. Most of the
variation across communities is related to the leaf economic spectrum,
represented in the PCA ordination. The first principal component
explained 94.97% (P-value < 0.0001) of the variation and was
positively correlated to SLA, leaf N and predominance of
C3 species in the communities, and negatively correlated
to LDMC and LA. The second principal component explained only 2.91%
(P-value = 0.001) and was positively correlated with high SLA, and leaf
N, while negatively correlated with LDMC, LA and C3species.
The correlations between biodiversity descriptors varied across
community functional groups (Figure 3). The correlations between species
richness with species diversity, and between species diversity with FR
were positive for all community groups. For G1 and G5 communities, all
relationships were positive, however, they were stronger for G1. For G2
communities, the correlations between species richness were negative
with both FR and functional response diversity. Moreover, species
diversity and functional response diversity were also negatively
correlated. Regarding G3 and G4 communities, the correlations between
functional response diversity were negative for both, species diversity
and FR.
In general, anomalous climatic events triggered more positive than
negative effects of biodiversity on both communities’ resistance and
resilience, and their estimated effects varied across community groups
and climatic events (Figures 4, 5, S2, and Tables S1 and S2).
Biodiversity effects on
resistance
We found analogous taxonomic
components effects on communities’ resistance. Such as a gradient in the
effects of species richness and species diversity on the resistance of
the communities under all anomalous events, ranging from strong and
positive in group G1 to weaker and negative in group G5 (Figure 4a-b).
Species diversity (Gini-Simpson) effects on resistance were positive in
G2 and G3 communities under both extreme dry and wet events, while in G4
and G5, its effects were negative under both moderate and extreme wet
events (Figure 4b).
Regarding the functional components of biodiversity, we also found
similar effects on communities’ resistance. For instance, both
functional redundancy and functional response diversity effects on the
resistance of G1 communities were strong and positive under all
anomalous events, whereas variable and weaker in the other community
groups (Figure 4c-d). In addition, functional redundancy effects were
positive in G3 and G5 under extreme dry anomalous events, while under
extreme wet they were positive in communities G2 and negative in G4
(Figure 4c). The effect of functional response diversity was negative
for G2, G3 and G4 communities under extreme dry anomalous events (Figure
4d), yet under moderate dry events, it was positive in G3 and G5 (Figure
4d).