Online Event
September 01-03, 2022 | Online Event
GPMB 2022

Twenty-year change in the presence of Celastrus orbiculatus, an invasive liana, in a U.S. eastern hardwood forest following hurricane disturbance

Erik C Berg, Speaker at Plant Science Conferences 2022
University of Montana, United States
Title : Twenty-year change in the presence of Celastrus orbiculatus, an invasive liana, in a U.S. eastern hardwood forest following hurricane disturbance


Celastrus orbiculatus (Asiatic bittersweet), an exotic and invasive liana, has proven to be an aggressive competitor of native forest vegetation in the Eastern United States. Bittersweet vines climb, choke, deform and sometimes kill standing native trees. Land management treatments, including prescribed fire, livestock grazing, herbicide application and cutting, have failed to effectively control the spread of bittersweet. Bittersweet is highly shade tolerant and can reside and remain senescent in densely shaded forest stands for several years. After canopy disturbance bittersweet can quickly capitalize on newly available light and grow and expand rapidly in presence. To date, researchers have demonstrated bittersweet’s high shade tolerance and have found the species generally prefers mesic over xeric and sub-xeric sites. However, land managers lack knowledge of bittersweet’s long-term spread following forest disturbance. To answer these information needs, we investigated bittersweet’s presence (yes-no, dichotomous response) through multilevel repeated measures logistic models, as a function of available light (imputed by hemispherical photography), soil moisture and location in and around forest gaps over 20 years following Hurricane Opal (impacted forests in October 1995) in mixed hardwood forests of the southeastern U.S. We found bittersweet to be highly shade tolerant, with individual plants surviving in less than three percent of full sunlight. As previously reported, we found bittersweet presence to be substantially greater in mesic and sub-mesic compared to xeric and sub-xeric sites (aliased by a macro-scale topographic index) and also greater in concave topographic microsites (aliased by a micro-scale index) with higher available soil moisture. Bittersweet presence was greater within gaps compared to the adjacent unaffected forest, and was also greater west and south of gap centers- microsites that typically receive less sunlight and have higher available soil moisture than other locations. This study yielded a novel finding- bittersweet presence was greater in sample quadrats which contained wind-created woody debris. We attribute this finding to bittersweet spreading from vines anchored on wind-felled woody debris to microsites on the forest floor. The probability of bittersweet being present within and outside of wind-created gaps increased rapidly for approximately the first 15 years after hurricane disturbance, presence probability then leveled-off through 20 years post-disturbance.

Audience takeaway notes:

  • Forest managers can use this information to predict the spread of bittersweet and tailor silvicultural prescriptions to minimize the spread of this invasive liana.
  • Research findings emphasize the importance of long-term research.
  • This research project incorporated both macro and micro scale topographic indices as prediction model covariates of available soil moisture. These metrics can be readily measured by land managers without direct measurements of available soil moisture.


Erik Berg has served as a research forester for the University of Montana for the past 11 years, studying flows of wood from forest through finished products. His work includes predicting post-logging forest residues and investigating remedies for sampling non-response. Prior to his current assignment he served as a wildland fire research leader, technology transfer specialist, forest ecology researcher, silviculturist and timber management specialist throughout a 35 year career. Dr. Berg received a bachelor’s degree from the University of Idaho, master’s degrees from the University of Idaho and Washington State University and a PhD in forest ecology from Clemson University.