Response of root systems of northern conifer transplants to flooding

Abstract

The response of root systems of four conifer species (Pinusstrobus, Pinusresinosa, Piceaglauca, and Piceamariana) to saturated soil conditions was examined in growth chamber experiments using 2- to 4-year-old nursery transplants potted into Plexiglas cylinders using a soil-containing mix. None of the conifers appeared adapted to grow roots into flooded soil, with the deepest roots of any species reaching only 10 cm below a water table after allowing time for maximum growth (30 days, 23 °C). Accordingly, anatomical observations of root cross sections indicated that none of the species had a significant internal air-filled pore space. There was a major difference between the pine and spruce genera in the response of aerobically grown roots to flooding. In both spruce species, no root tips survived flooding treatments longer than 1 day, whereas in both pine species, 35% or more tips survived even the longest (7-day) treatment. This difference could not be readily related to differences between these species in drainage preference in the field. Despite the much greater loss of root tips in the spruces, the postdrainage recovery of transpiration, after a depression during flooding, was as rapid in the spruces as in the pines.