New Harvard Forest Publications: Ragweed's Past & Future In New England

Kristina Stinson and Ed Faison took the lead on two Harvard Forest publications demonstrating that climate change increases the presence and abundance of ragweed (Ambrosia artemisiifolia) and its pollen. K. Stinson and F. Bazzaz tested whether elevated CO2 would benefit the growth and reproductive output of small plants over larger ones by growing experimental stands of competing ragweed individuals in climate-controlled open top chambers shown in photo. They found that CO2-induced growth gains of smaller plants enhanced the relative reproductive output of small plants relative to larger plants. Thus, enhanced reproduction is expected and more individuals are likely to reproduce in future populations of this allergenic weed. Harvard Forest's MFS student Brian DeGasperis and Summer Program sudents Jimmy Tran and Jen Petzold assisted with this project.

Stinson, K. A., Bazzaz, F. A 2006. CO2-enrichment reduces reproductive dominance in competing stands of Ambrosia artemisiifolia (common ragweed). Oecologia 146: 155-163. 

In a forthcoming paper in the journal Ecology, researchers E.K. Faison, D.R. Foster, W.W. Oswald, B.C.S. Hansen, and E. Doughty investigated the environmental drivers behind abundant ragweed pollen in sediments of four southern New England lakes 10,000-8000 years ago. They found strong evidence that high levels of ragweed pollen were associated with warmer, drier conditions. This conclusion is corroborated by independent lake level and climate reconstructions. Together, these results have implications for future ragweed distribution and abundance, and suggest that more ragweed pollen could accompany rising temperature and CO2 levels in New England.

E.K. Faison, D.R. Foster, W.W. Oswald, B.C.S. Hansen, and E. Doughty. 2006. Early Holocene Openlands in Southern New England. Ecology, 87(10), 2006, pp. 2537–2547.