The effects of progressive root removal prior to planting on shoot and root growth of Betula pendula Roth

Root loss during transplanting of bare rooted nursery stock is thought to limit water uptake during establishment. An initial investigation into the effects on growth under well watered conditions of progressive removal of root material from dormant trees of Betula pendula Roth. was set up in spring 1994. Trees with roots ≤ 1 mm removed (40% removal by mass) and with roots ≤ 5 mm removed (84% removal by mass) were compared to controls. Some limited measurements of water relations were also made. Shoot and root growth were increasingly limited by progressive root removal. Root regrowth was apparently proportional to the amount of old root material left behind after transplanting. In addition, the most severe treatment (roots ≤ 5 mm were removed) limited root growth in favour of shoot growth. Direct measurements of water relations proved to be difficult and inconclusive, however, increases in stem diameter, an indirect measurement of changes in water relations, indicated that progressive root removal subtly increased water stress in the trees. Alternative hypotheses for the observed of changes in growth based on limitations in sugar physiology and hormone imbalance are also discussed.