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).