Understorey environment and vegetation response after partial cutting and site preparation in Pinus strobus L. stands

Understorey vegetation response to thinning, site preparation and underplan ting was investigated in three natural, 110-year-old eastern white pine (Pi nus sti-obits L.) stands. The study was arranged in a split plot, randomize d block design with four replicates, and included three thinning and four s ite preparation treatments. Early competition response, natural and planted white pine seedling growth and nutrient uptake were monitored. Light (PAR) , soil moisture and temperature were assessed during the first two growing seasons. Environmental conditions varied with treatment. With increased thi nning, overall the diversity of tree species decreased and shrub species in creased, although this will change with time. PAR was the most crucial for successful seedling growth. At 50% PAR, seedling biomass of both natural an d planted seedlings no longer appeared limited directly by light, and site preparation and brush control treatments resulted in further increased grow th and improved seedling nutrition. (C) 2001 Elsevier Science B.V. All righ ts reserved.