Initial Evidence for Simultaneous, Bi-Directional Sap Flow in Roots of Interconnected Aspen Ramets (Populus tremuloides)
Approximately 40% of the world’s currently known plant species exhibit some form of clonality. Yet, little is known about the extent of clonal integration (e.g. the sharing and translocation of resources among ramets), especially in woody species. Aspen (Populus tremuloides Michx.), a widespread clonal tree species of high ecological value and conservation concern, is an excellent model species to study clonal integration. We used sap flow sensors on the root system of aspen located in the Fraser Experimental Forest (Colorado) to quantify water fluxes, assess directionality of flow and assess responses to a root severing experiment. Our results indicate simultaneous, bi-directional flow in roots with 3–4 times more flow in one direction. Flow towards ramets that were subjected to severing of roots (except the measured root) decreased considerably, and an increase in root flow ‘down the line’ towards connected, untreated ramets suggests complex interactions within the root system. Our results are intriguing and provide a first account of directionality of flow and distribution of water in an interconnected root system of a clonal tree species. Based on these findings, we formulate a set of further research questions and discuss methodology and experiments to test them.
Bretfeld, M., Franklin, S.B. & Hubbard, R.M. Folia Geobot. (2017). Initial evidence for simultaneous, bi-directional sap flow in roots in interconnected aspen ramets (Populus tremuloides). Folia Geobotanica 52: 345. https://doi.org/10.1007/s12224-017-9285-0