Impacts of Celastrus-primed soil on common native and invasive woodland species

Abstract

Invasive plant species have been shown to alter soil environments resulting in changes in soil chemistry, biota, and nutrient cycling. Few studies have focused on how soil changes affect co-occurring native species or plants of different growth forms. This study, located in Connecticut, USA, focused on the soil effects of the liana, Celastrus orbiculatus (oriental bittersweet), a prominent invader of eastern North America, using two different approaches. In a litter addition experiment, addition of C. orbiculatus leaf litter to uninvaded field soils showed an increase in soil nutrients, pH, and nitrogen mineralization over 2 years across a range of soil and forest community types. In a complimentary common garden-pot experiment, a suite of common, ecologically similar, native and invasive lianas and shrubs were grown in soils primed with C. orbiculatus. Invaded soil was compared to uninvaded field and control potting soils. The change in soil attributes was not significantly different when grown with native or invasive plants; however, soils grown with lianas had a greater decrease in nutrients than those grown with shrubs. Although soils from locations with C. orbiculatus were higher in nutrients than uninvaded soils, plant growth, as measured in root:shoot, root and stem biomass, relative growth rate of volume, and final biomass were not different in invaded and uninvaded soils for either lianas or shrubs. However, lianas had similar growth patterns in nutrient-sparse potting soil, while shrubs growing in potting soil had lower growth. Thus, negative impacts of invaded soils on plant growth are not universal, and the plant community may show a varied response to C. orbiculatus-primed soils depending on the level of resource competition.