Nursery and site preparation interaction research in the United States

Researchers in the United States have generally taken a "segregated'' appro ach to regeneration research. As a result, trials involving nursery treatme nts are usually separated from trials involving site preparation treatments . Researchers have concentrated on just the main treatment effects. Little effort has been placed on examining potential interactions between nursery and site preparation treatments. Only a few nursery by site preparation (Nx SP) studies have been established. The profession has generally assumed tha t gains from nursery and site preparation treatments are simply additive, o r that the relative gains from nursery treatments would be insignificant wh en compared to intensive site preparation treatments. Both of these assumpt ions may be incorrect. This review examines some of the NxSP interaction trials that have been est ablished in the United States during the last half of the 20th century. We predict that as rotation ages for plantations decrease, the need for NxSP i nteraction trials will increase. NxSP interaction studies will be required if researchers wish to include both nursery and site preparation treatments in their early establishment models. To date, only a few establishment mod els have been developed in the United States.