The role of microtopography and substrate in survival and growth of Atlantic white-cedar seedlings

The decline of Atlantic white-cedar (AWC) throughout its range has motivated researchers to investigate the requirements for seedling recruitment. In this study, field experiments were conducted to determine the underlying factors explaining AWC recruitment at Brown Mill Pond in Rye, New Hampshire. The experiments tested whether substrate type and elevation relative to the water table influenced AWC seedling survival or growth. Seedlings transplanted to different elevations above the water table (17-22 and 35-40 cm) and different substrates (moss-litter and tussock sedge) were monitored over two growing seasons (2001 and 2002) and changes in seedling height, branch number, stem diameter, and above ground biomass were quantified. In order to describe potentially important physical conditions associated with each treatment, we measured the following environmental variables within each experimental treatment: soil pH, soil redox potential, soil temperature, air temperature, and soil moisture. In contrast to expectations based on AWC seedlings' differential distribution among substrate types, the field experiments indicated substrate type did not influence seedling survival or growth. The experiments showed that elevation relative to the water table, however, influenced AWC seedling performance, indicating that moisture was the primary limiting factor in the natural regeneration of AWC at this site.