Print PageQuaking aspen (Populus tremuloides Michx.) stands provide a variety of crucial ecosystem services and high biodiversity. In the western United States, aspen stands have been declining due to a decrease in wildfire and an increase in browsing. Additionally, in recent years a new phenomenon dubbed “Sudden Aspen Decline” has hastened this trend. Aspen produce mainly vegetatively by suckering from the parent root system. Clonal integration (the sharing of water, nutrients, and carbon resources via roots) determines the number and survivorship of new individuals. Knowledge about the effects of clonal integration on sucker development and responses to environmental factors will help developing aspen management strategies, especially in respect to the current mountain pine beetle epidemic and related changes to the ecosystem. To quantify clonal integration, we measured proximal and distal root sap-flow of two individuals in summer 2009, and for periods of time throughout the growing season of 2010 (leaf-out to shedding). In August of 2010, we removed 50% of the leaves from one individual and 75% of leaves from the other to mimic herbivory. Sensors were also reversed to measure bi-directional flow. We hypothesized that flow is mainly uni-directional and decreases following stress, such as herbivory.
Results/Conclusions
Root sap flow in aspen showed a strong diurnal pattern with similar patterns between replicate samples. As hypothesized, flow was mostly uni-directional with up to 4 to 8 times more proximal flow than distal flow, suggesting that most resources are allocated from mother ramet to daughter ramet. In both years, distal flow peaked between 800 to 1100 g/hr, and proximal flow between 100 and 300 g/hr. The de-leafing experiment resulted in little change in root sap flow, opposite our hypothesis, but a definite decrease in stem sap flow. This suggests that transpiration of one individual is not the major driver for rootflow. We propose future research to include the effects of light incidence on sap flow by shading ramets, or by removing competing vegetation (as it is naturally occurring due to the mountain pine beetle epidemic).
