Effects of tree canopy cover and vegetation management on the establishment and growth of planted American Samoan native hardwood tree seedlings

I tested the effects of an interaction between tree canopy cover and vegetation control method on seedling performance for eight American Samoa tree species. The experiment was a CRD with four vegetation management treatments: mown, mulched, both, and a control.  The study was planted into an existing plantation of the same eight species, which was six-years-old. The canopy cover levels ranged from 0 to nearly 100% and approximately eighty trees of each species were distributed across this gradient. Seedling size was assessed every six months and vegetation treatments were maintained monthly for a period of two years.. Hemishperical canopy photos were used to assess cover and PAR sensors in a ceptometer were used to determine incidental solar radiation. As expected, shade-intolerant species with out canopy cover grew better with vegetation control, but mulching was ineffective compared to treatments involving mowing. In areas with heavy canopy cover, there was no effect of vegetation control treatment due to limited understory vegetation. Regression models for predicting the optimal environment for each suite species (e.g., shade-tolerant, shade-intolerant, and intermediate) will be presented. This project has potential implication for the development of multi-species forest stands which emulate native ones in composition and successional trajectory.