Plant, insect, and soil microbial communities vary across brome invasion
gradients in northern mixed-grass prairies
Abstract
Species interactions shape native plant communities, influencing both
composition and ecosystem processes, with invasion by non-native species
threatening these dynamic relationships, native species, and function.
The consequences of invasive plants in particular may stretch across
taxa to impact plant, insect, and soil microbial communities directly
and indirectly, with consequences for ecological functioning. In
northern mixed-grass prairies, invasion by two annual brome grasses,
Bromus arvensis and B. tectorum, negatively impacts rangeland plants;
however, the simultaneous effects on insects and soil microbes (bacteria
and archaea), and the implications for ecological function, have
received less attention. Here, using observational field studies
conducted at two mixed-grass prairie sites in Montana and Wyoming, we
assessed the relationships between plants, insects, and soil microbes
across gradients of invasion by B. arvensis and B. tectorum. Overall, we
found differences in plant and insect communities and functional groups
with increasing invasion abundance for both brome species. However,
associations between invasion and the soil microbial community were
species specific, as we only saw these relationships under B. tectorum
invasion, implying B. tectorum may have more substantial consequences
for rangeland management. While invasion by annual bromes may cause
changes in certain plant and insect functional groups, such as C4
perennial grasses and certain insect herbivores, soil microbial
functional groups may be less impacted, especially under B. arvensis
invasion. This work sheds light on the need to explore changes in
natural communities across taxa and to all invasive species, as
ecosystem effects are likely to be contingent upon both.