Ten years of plant observations at 43 terrestrial US sites link greater invasive-species cover with lower year-to-year stability in total vegetation cover. The association appears in local plots and at a broader spatial scale. Because the peer-reviewed study is observational, it cannot establish that invasive plants alone drove the change; it also examines which components of diversity and timing may contribute.
The US National Ecological Observatory Network supplied plant surveys collected from 2013 through 2022. The data covered 43 terrestrial sites, with 400-square-metre plots containing one-square-metre subplots. Summed plant cover served as a measure of community abundance. This allowed the team to examine annual changes within a local community separately from stability across several local communities.[1]
Greater invasive cover was associated with lower temporal stability locally and at the broader scale. Individual species stability and the extent to which species changed at different times also declined with invasive cover. Such differences can otherwise buffer changes in total cover. For differences in timing between local communities, the study did not find a statistically significant direct link to the area covered by invaders.[1]
Plant traits from the TRY database informed estimates of functional diversity. Lower functional diversity and leaf traits associated with faster resource use emerged as possible indirect pathways. The analysis also considered human pressure, tree cover and survey frequency. Invasive species were not experimentally introduced at the sites. The measured outcome was stability of summed vegetation cover over time, rather than every ecosystem function.[1]
