What is the symbiotic relationship between poison ivy and willow oak?

The relationship between poison ivy and willow oak can be described as commensalism. Poison ivy often grows in the understory of willow oaks, benefiting from the shade and support provided by the larger tree without harming it. The willow oak remains unaffected by the presence of poison ivy, which allows the vine to thrive in a suitable environment while the oak continues its growth unimpeded.