Continental‐scale plant invasions reshuffle the soil microbiome of blue carbon ecosystems

Abstract

Theory and experiments support that plant invasions largely impact aboveground biodiversity and function. Yet, much less is known on the influence of plant invasions on the structure and function of the soil microbiome of coastal wetlands, one of the largest major reservoirs of biodiversity and carbon on Earth. We studied the continental‐scale invasion of Spartina alterniflora across 2451 km of Chinese coastlines as our model‐system and found that S. alterniflora invasion can largely influence the soil microbiome (across six depths from 0 to 100 cm), compared with the most common microhabitat found before invasion (mudflats, Mud). In detail, S. alterniflora invasion was not only positively associated with bacterial richness but also resulted in important biotic homogenization of bacterial communities, suggesting that plant invasion can lead to important continental scale trade‐offs in the soil microbiome. We found that plant invasion changed the community composition of soil bacterial communities across the soil profile. Moreover, the bacterial communities associated with S. alterniflora invasions where less responsive to climatic changes than those in native Mud microhabitats, suggesting that these new microbial communities might become more dominant under climate change. Plant invasion also resulted in important reductions in the complexity and stability of microbial networks, decoupling the associations between microbes and carbon pools. Taken together, our results indicated that plant invasions can largely influence the microbiome of coastal wetlands at the scale of China, representing the first continental‐scale example on how plant invasions can reshuffle the soil microbiome, with consequences for the myriad of functions that they support.

Specific Plant Mycorrhizal Responses Are Linked to Mycorrhizal Fungal Species Interactions

“…It has been reported that the complexity of microbial networks was related to environmental changes (Fernandez-Gonzalez et al, 2020;Lin et al, 2021;Ma et al, 2021;Qiu et al, 2021;Liu et al, 2022). Specifically, a recent study reported that complex microbial networks were conducive for microbes to adapt to adverse environments, such as drought and invasion (Fu et al, 2022;Gao et al, 2022;Wang et al, 2022). And in our study, the network properties of AMF were also linked with plant responses to inoculation.…”

Moderate salinity improves the availability of soil P by regulating P‐cycling microbial communities in coastal wetlands

“…Analogously, salinity in our study strongly altered the composition of the soil microbial community (β‐diversity) and led to taxonomic changes responsible for P cycling in the wetland soils (Figure 3). This may be because brackish environments, by providing additional resources and niches, contribute to soil microbial diversity by supporting new species not found in freshwater habitats (Gao et al, 2022). Interestingly, we also found that the network complexity and stabilities of the P‐cycling microbial communities were lower in the brackish wetland than in the freshwater wetland (Figure 5).…”

“…On the one hand, wetland salinization strongly affected the physicochemical characteristics of the soil water (Table S3), which can induce a strong selection pressure on soil microbial communities, thereby excluding many microbes from the network (Ratzke et al, 2020). On the other hand, previous studies have reported that high microbial diversity generally implies that rich microbial communities simultaneously compete for the same resources and energy within their habitats, which is accompanied by low network complexity (Farrer et al, 2019;Gao et al, 2022), consistent with the high microbial diversity we observed in the brackish wetland (Figure 2).…”

“…Coastal estuarine wetlands are dynamic ecosystems at the interface of land and sea and play a critical role in maintaining biodiversity and regulating nutrient cycling (Dang et al, 2019). Coastal wetland ecosystems are notably sensitive and vulnerable to global climate change because of their location in intertidal zones (Gao et al, 2022). Recent assessment reports by the Intergovernmental Panel on Climate Change have predicted that the global mean sea level will rise 0.28–1.01 m by 2100 under different scenarios of emissions of greenhouse gases relative to the 1995–2014 level (IPCC, 2021).…”

Factors driving the halophyte rhizosphere bacterial communities in coastal salt marshes

“…A study of global wetlands showed that temperate latitude wetland soils harbored the highest bacterial diversity (Bahram et al, 2022), and it was reported that bacterial community composition was strongly correlated with latitude along the eastern coast of the United States (Blum et al, 2004). Multiple environmental factors including climate, soil properties, and vegetation types can affect the diversity and composition of bacterial communities and thereafter regulate microbial biogeography (Zhou et al, 2016;Gao et al, 2022;Yang L. et al, 2022;. However, after accounting for the host selection effect of halophyte plants (i.e., microbes can be strongly affected by the root exudates of plants in the rhizosphere), it is not clear which is the main driver of microbial biogeography in salt marshes.…”