This week we welcome our own Katherine Duchesneau.
Mycorrhizal disturbance as an invasion mechanism in Alliaria petiolata: Community and functional composition of soil microbial communities in the field
The dynamic interactions between below-ground and above-ground communities continuously shape the composition of terrestrial communities. Microorganisms in soil communities perform many ecological functions within an ecosystem, such as decomposition, nitrogen fixation, and pathogens. Microbes with different functions respond differently to environmental changes, which in turn can affect community composition and ecosystem function. Most studies of soil microbial function focus on individual components of soil ecosystems, overlooking the collective role of a network of soil microbial functions. Alliaria petiolata is an invasive plant from Europe that has been the subject of dozens of laboratory and greenhouse experiments, many of which demonstrate a reduction in arbuscular mycorrhizal fungi (AMF) germination. However, it is less clear how the entire native soil biota responds to A. petiolata under natural field conditions, where edaphic characteristics and interacting soil microbes can alter A. petiolata exudates and affect AMF performance. Additionally, the effect of A. petiolata on non-mycorrhizal fungi and bacteria remains to be determined. I analyzed the taxonomy and function of whole soil communities using High Throughput Sequencing (HTS) of ITS and 16S genes, paired with root health measurement of native plants co-occurring with A. petiolata. Contrary to several lab and greenhouse experiments, I found that AMF communities did not differ significantly in the presence of A. petiolata. Instead, survey plots containing A. petiolata had more fungal decomposers and pathogens, with a significant decrease in the root health of co-occurring native plants. Additionally, changes in ectomycorrhizal species composition and a reduction in nitrogen-fixing bacteria were significantly associated with A. petiolata invasion, suggesting A. petiolata causes an increase in available nitrogen. This work demonstrates the value of characterizing soil microbial communities in situ in order to understand how ecosystems respond to anthropogenic change.