Mixed Responses to Woody Encroachment in Icelandic Herbaceous Plant Morphology and Phenology

Climate change and afforestation efforts are promoting tree growth into traditionally treeless locations in Iceland. This study examined this woody encroachment’s effect on the phenology and morophology of eight plants (Agrostis aequivalvis, Equisetum pratense, Equisetum arvense, Alchemilla alpina, Ranunculus acris, Lupinus nootkatensis, Anthriscus sylvestris, and Taraxacum sp.) in Kjarnaskógur forest, Akureyri, Iceland. An initial transplantation experiment testing trees’ effect on A. aequivalvis, E. pratense, R. acris, and A. sylvestris failed due to plant death. A subsequent observational study examined trees’ effect on E. pratense, A. alpina, R. acris, L. nootkatensis, A. sylvestris, and Taraxacum by observing morphological characteristics (leaf size, plant height, leaf number) in individuals (between 56 and 200 per species) within and outside of wooded environments. Some species grew larger leaves and experienced growth delays in a wooded environment, suggesting adaptation to competition. Other species grew smaller leaves in a wooded environment, suggesting outcompetition by trees. This suggests that the expansion of trees in Iceland will create morphological and phenological changes in herbaceous plants, possibly having ramifications throughout Icelandic ecosystems