Root clonal networks in Populus tremuloides and Populus balsamifera; implications in tree physiology and stand dynamics

1 Annie DesRochers, Forest Research Institute - UQAT

2 Francine Tremblay, Forest Research Institute - UQAT

Populus tremuloides and P. balsamifera regenerate mostly by root suckering after major disturbances (fire or harvesting), but nevertheless maintain high levels of clonal diversity, even at small spatial scales. We hypothesized that clonal diversity maintenance could be facilitated by integration of different clones through natural root grafts into trees' communal root system. In order to verify this hypothesis, we induced root suckering in mature aspen stands by harvesting the stems, where clones had been delineated with molecular markers. After a full growing season, clonal identity of the suckers was assessed prior to excavating the entire root systems. Excavation revealed many living roots on trees that had been dead for several years, some of them with no other root connections but grafts to living ramets of different clones. Moreover, these roots from dead stumps all had newly formed suckers growing on them. Acquiring roots of dead trees helped to maintain extensive root systems, which increased chances of clone survival, beyond the death of individual trees. Substantial interconnectivity both within clones and between clones due to inter-clonal grafts results in formation of genetically diverse units affecting interpretations of diverse ecophysiological processes taking place in forests stands. Resource sharing between connected ramets is one of these processes which will be discussed.