Essential oil content of Rhododendron tomentosum responds strongly to manipulation of ecosystem resources in Arctic Alaska

Abstract

The essential oils of the widely distributed boreal/Arctic dwarf shrub, Rhododendron tomentosum ssp. subarcticum (Harmaja) G.D. Wallace, have important ecological, cultural, medicinal, and commercial roles. To understand the relationship between resource limitation and essential oil content of this species we measured the amount and diversity of terpenes from shoots of plants exposed to a 14-year ecosystem resource manipulation experiment in Arctic Alaska. Treatments tested interactive effects of nitrogen (N) and phosphorus (P) addition, warming and N + P fertilization, and shading and N + P fertilization. The controls and NP fertilization had the highest essential oil content, whereas shading and P addition had less than 20% of the control content. Warming reduced essential oil content to <65% of that of the controls. Essential oil components varied greatly among the treatments, with significant differences in the expression of specific essential oil components. Large changes in plant community composition and ecosystem structure in response to treatments likely played a large role in the response of R. tomentosum. Our data suggest that resource changes in response to climate warming and its secondary effects on light and nutrient availability have the potential to change the profiles of essential oils in R. tomentosum, with important ecological and cultural impacts.

Chemical Composition and Antiplasmodial Activity of the Essential Oil of Rhododendron subarcticum Leaves from Nunavik, Québec, Canada

“…In this last study, the composition of L. palustre ssp. decumbens also included some monoterpenes and monoterpenoids, including high proportions of cymene …”

“…subarcticum essential oil, has never been reported in L. palustre ssp. decumbens , , although we did find a low quantity of germacrone and myrcene in our essential oil extract. Another compound, p -cymene, is quite abundant, although not the most dominant.…”

“…decumbens also included some monoterpenes and monoterpenoids, including high proportions of cymene. 29 …”

“…decumbens also included some monoterpenes and monoterpenoids, including high proportions of cymene. 29 On the other hand, R. tomentosum has been much studied in Europe and Asia. A review of the available scientific literature on the essential oils of the former L. palustre L. reveals no less than 10 different chemotypes from various countries, excluding data from R. subarcticum or synonyms.…”

The International Tundra Experiment (ITEX): 30 years of research on tundra ecosystems

“…A unique study of warming, fertilization, and shading effects on the essential oil content of the evergreen shrub Rhododendron tomentosum showed that the highest oil concentrations were found in unmanipulated control plants and in those fertilized by a combination of N and P, whereas shading and addition of P resulted in the lowest concentrations. Warming also decreased the oil content by about 65% (Baldwin and Oberbauer 2022). The responses in essential oil content by R. tomentosum were also affected by the changes in the plant community after 14 years of treatments, especially the increase in shrub growth.…”