Publication

Lianas (woody vines) are a leading concern in urban forest management given their ability to reduce the growth rate and survival of trees. Efforts to control invasive lianas are widespread, yet forests are often reinvaded following management. Changes in soil nutrient availability could help explain why some forests are susceptible to reinvasion. Specifically, invasive lianas could be "drivers" of altered nutrient dynamics that persist in the soil and favor their re-establishment, or they could be "passengers" of conditions created by prior site disturbances. We test these alternative models by analyzing soils across gradients of liana cover and forest disturbance in mature hardwood forests in New York City. Overall, total non-native liana cover was linked to elevated soil pH, reduced labile carbon, and altered net potential nitrification-three conditions indicative of increased soil nutrient availability. However, the effects of lianas varied substantially by species. Non-native lianas had a positive, negative, neutral, or non-linear effect on a single soil variable depending on the species. Aggregation of total non-native liana cover can therefore obscure the direction and magnitude of species-level effects. We also found positive relationships between forest disturbance, non-native liana cover, and soil pH, but we found no relationships between disturbance and net nitrification or labile carbon. These results suggest that non-native lianas are passengers to elevated levels of disturbance and soil pH but drivers of altered carbon and nitrogen dynamics. As such, management efforts aimed at reducing soil nutrient availability and removing invasive lianas may be required to limit reinvasion and promote ecosystem recovery.