Herrick Endowed Chair of Plant Biology Kent State University KENT, Ohio, United States
Background/Question/Methods Woody plant encroachment into grasslands is a global phenomenon that alters ecosystem composition and function. Eastern redcedar (Juniperus virginiana) is a native tree that has drastically expanded its range in North America. At the landscape scale, altered grazing and fire regimes are the primary factors facilitating the expansion of redcedar. However, at a smaller spatial scale, we wished to determine whether plant-plant scale mechanisms could also facilitate the initial establishment of redcedar in prairies. We also asked if legacy effects of redcedar encroachment could favor regeneration of redcedars following removal of stands. In a series of greenhouse experiments using redcedar and four common prairie grasses, we tested whether redcedar generated beneficial plant-soil feedbacks. In the first experiment individual grasses were grown in live and sterilized greenhouse-conditioned redcedar soils. In the second experiment, under treatments consisting of live and sterile field redcedar-soils and varying levels of redcedar root matter, growth of four grass species was monitored.
Results/Conclusions Individual grass growth in redcedar-conditioned soils was suppressed for two of the four study species. In the second experiment, redcedar soil had a negative feedback on the growth of two grass species, which resulted in a suppression of growth and changes in dominance within the community. Feedbacks from redcedar-conditioned soils could create favorable conditions for the establishment of redcedar seedlings. We found negative feedbacks on grasses in live and sterile redcedar soils. A possible mechanism for this negative feedback could be an allelopathic chemical coming from redcedars. The soil legacies created by redcedars inhibited the growth of certain grasses, which could alter community composition and favor the re-establishment of redcedars following treatment.