Discussion
Revealing the spatiotemporal pattern of microbial communities is a
fundamental topic in ecology, which have been explored extensively in
microbial ecology over the last two decades (Chu et al., 2020).
Furthermore, the significant effect of the seasonal change in regulating
the alpha diversity of soil bacteria and fungi was found at the regional
scale (Hainan) in our previous study (Wei et al., 2022b). Still very few
studies have mapped the temporal and spatial distribution changes of
microbial communities of the soil–plant continuum. Here we explored the
spatiotemporal of soil–plant continuum fungal community in the rubber
tree across different niches and regions, doing so can help to clarify
the drivers of space and seasonal change upon microbial community
variations. Our findings provide robust empirical evidence that the
spatiotemporal variation of fungal diversity in rubber tree was mainly
shaped by seasonal change, but only spatial impacts significantly
altered microbial beta diversity.
Our results demonstrate that the alpha diversity of soil–plant
continuum fungal community is highly dependent on seasonal changes,
which is in line with previous studies that have observed significant
seasonal variations in microbial diversity (Fournier et al., 2020; Lan
et al., 2018; Rasche et al., 2011; Xiang et al., 2021; Zhang et al.,
2020). In our study, we provide evidence suggesting that climatic
factors play a crucial role in mediating the seasonal variation of
fungal alpha diversity. Climatic factors have been identified as the
best predictors of soil fungal richness and community composition at a
global scale (Bahram et al., 2018; Tedersoo et al., 2014). Importantly,
our study further extends this earlier observations at the soil–plant
continuum and now provides widespread evidence that climatic factors
mediating the alpha diversity of plant microbiome. Among the
environmental variables, we found that temperature and precipitation
were the dominant predictor for fungal richness, which has also been
found in numerous previous studies (Bahram et al., 2018;
Delgado-Baquerizo et al., 2017; Fierer, 2017; Hiiesalu et al., 2017; Liu
et al., 2020; Tedersoo et al., 2014). Notably, the alpha diversity are
sensitive to temperature and precipitation, displaying an unimodal
pattern in most compartments, except for the leaf endosphere and root
endosphere which showed a linear pattern. Given that temperature and
precipitation are generally higher during the rainy season and higher in
Hainan compared to Banna, this further supports the observed unimodal
pattern in most compartments. Thus, it is not surprising to find that
the contrasted seasonal change pattern in Hainan and Banna. Furthermore,
we observed a stronger seasonal effect compared to a geographical
location effect on some environmental predictors. Specifically, leaf
physicochemical factors such as water content (WC) and climatic factors
such as temperature and precipitation were primarily influenced by
seasonal changes, contributing to the mechanisms driving microbial
seasonal variations.
In contrast, we provide solid evidence that the beta diversity of
soil–plant continuum only showed a geographical variation pattern. This
aligns with previous studies that have shown spatial factors to be more
important in shaping soil microbial communities across large spatial
scales (Fierer and Jackson, 2006; Lauber et al., 2013; Wei et al.,
2022b; Zhang et al., 2020). The effect of site location was far more
influential than the seasonal change in regulating the communities of
both soil bacteria and fungi at the regional scale (only in Hainan) in
our previous study (Wei et al., 2022b). Given that biogeographic
patterns variation of community similarity indicates the influence of
historical factors (Ma et al., 2017; Martiny et al., 2006), compare to
our previous studies (research in Hainan soil samples) (Wei et al.,
2022b), the stronger geographical variation pattern suggests that the
pronounced impact of historical event on fungal community structure in
soil–plant continuum of rubber tree. For fungal beta diversity, leaf
phosphorus (P) and soil available potassium (AK) were the most important
factors in leaf and soil samples, respectively. Besides, major taxa
belonging to Dothideomycetes and Eurotiomycetes in leaf samples,
according to their life strategies, which have been assigned as
copiotrophic fungi, this might explain why leaf samples responded to
altered leaf nutrients (e.g., leaf P), which have already been
demonstrated (Evans et al., 2014; Ho et al., 2017; Li et al., 2021;
Placella et al., 2012). It is worth noting that leaf P and AK which is a
highly localized variable, were evidently stronger affected by sampling
sites. In all, we found a stronger geographic location effect than
seasonal effect upon fungal beta diversity estimates. Furthermore,
geographic factors contributed a larger proportion of variation relative
to edaphic and climatic factors to the beta diversity of rubber leaf
than soils that of soil–plant continuum, indicating a stronger effect
of stochastic processes in driving the beta diversity of rubber leaf.
These results was also confirmed by the VPA models and Mantel test, and
are also consistent with previous observations (Lan et al., 2022).