First-year growth and development of common reed (Phragmites australis) in a long-term common garden study

Background/Question/Methods

Common reed (Phragmites australis(Cav.) Trin. ex Steud.) is one of the most widely distributed flowering plants in the US with native and non-native lineages overlapping across regions. The non-native or introduced lineage is dominant along the Atlantic Coast and in the Great Lakes area. In western North America, the introduced lineage is increasing in specific habitats (e.g., desert seeps and springs, riparian areas, and marshes), but native populations are still common in the Southwest and Pacific Northwest. The impacts of the introduced lineage include loss of habitat, reduced plant diversity, altered biogeochemical cycles, and impediment of surface water flow. It is unclear if these impacts will be sustained under changing climates, especially extreme drought events. A large-scale common garden study has been initiated to address this topic using mesocosms with plants collected from across the US. The objective during the first year of this long-term study was to quantify growth and development (e.g., average and maximum stem height, number of stems and stolons, plant growth structure, leaf coloring, and above-/below-ground biomass) of common reed grown from seed.

Results/Conclusions

By the end of the first year, native common reed from California reached a maximum stem height of 152 cm, which was greatest of any of the lineages. Two natives from Michigan and California and an introduced from Wisconsin produced 17-25 grams plant^-1 of biomass, which was the most of any of the nine lineages. The Michigan and Wisconsin plants also had the most stolons. Total number of stems was 45 and 36 plant^-1 for the Wisconsin introduced and California native, respectively, but only the native stems tended to remain near the main clump. With the exception of Michigan, the introduced lineages from Wisconsin, Indiana, and South Dakota had more stems outside the main clump than the natives.  The native lineage from Wisconsin had the highest number of medium-sized roots. This and other detailed information collected in the first year and succeeding years will provide insight into the growth and development of common reed in response to fluctuating environmental conditions and help in forecasting its spread and distribution, particularly in the southwest, Midwest and Great Lakes regions of the US.