Poster

         Ecology

Effects of leaf litter depth on seed germination of non-native bittersweet Celastrus orbiculatus in a Pennsylvania forest

Presenting Author
Amy Faivre
Description
Celastrus orbiculatus is a non-native, invasive bittersweet in many eastern forests in the United States. It displaces native plant species and changes natural forest habitats by climbing and sometimes girdling trees. Individual C. orbiculatus plants produce many seeds. Thus, one way to reduce the presence of this species in forests is to understand more about the germination of its seeds. Previous studies have shown that depth of leaf litter in forests affects seed germination and early seedling growth. For our study we collected seeds of C. orbiculatus in November 2021 in a forest at Wildlands Conservancy in Emmaus, PA, cold stored them and set up two replicate germination trials in the Cedar Crest College greenhouse. The three conditions were no leaf litter, a low level of leaf litter (1 Mg/ha), and a high level of leaf litter (16 Mg/ha). The number of seedlings germinated was greatest at the early stages of the experiment in the no or low leaf litter treatments, but by the end of the experiment in one trial the differences disappeared and in a second trial, the no litter seeds germinated significantly less (p < 0 .001). In both trials, significantly more seedlings growing in leaf litter than in no leaf litter reached later developmental stages (marked by the presence of two cotyledons) by the end of the experiment. Data for both trials were combined to analyze the over-dried seedlings. In the high leaf litter treatment, the seedlings had significantly longer roots (p < 0 .005), longer hypocotyls (p < 0 .001), and mass of roots (p < 0 .001) than the no and low leaf litter treatments. The leaf litter levels in the forest where the C. orbiculatus seeds had been collected fell between the low and high leaf litter treatments used in this study.  Understanding the effects of leaf litter on seed germination success may help in controlling seedling emergence and future spread of this invasive plant.