Effect of Image Capture Location In Minirhizotron Tubes On Fine Root Distribution In the Boreal Forest of Saskatchewan.

When conducting fine root studies with minirhizotrons the orientation of image capture inside the tube tends to be from the top of the tube. However, does this location accurately represent fine root biomass or production? The objective of this study was to determine if image collection orientation in the tubes influenced estimates of root biomass and production for boreal species. Two Saskatchewan boreal ecosystems including an aspen (Populus tremuloides) and two jack pine (Pinus banksiana) (mature and 8 year old) stands were selected and tubes were installed in 2002 and images were collected for several years as part of a larger study. For this study, images were collected in June, July and August of 2006 for the right and left side as well as the top of the tube to determine fine root biomass and productivity. In August, selected tubes were manually excavated to observe rooting patterns around the tubes. Fine root production for the top of the tube was significantly different from the other two locations for trembling aspen in July. There were no significant differences in root biomass or productivity between tubes locations for each month for the other two stands. Excavation of tubes showed preferential root growth along tubes in the jack pine forest, especially on the underside of the tube and in aspen stands there was accumulation of organic matter on the underside of the tubes suggesting that tube installation pushed material down the minirhizotron hole or OM moved with water along the length of the tube from the surface during the previous four years of installation. Image collection for these three stands was not impacted by image location in tubes; however, further work should investigate the physical impact of tubes on soil properties and root system development for longer termed studies.