FD3-1: Changes in post-disturbance tree recruitment alter successional trajectories of species composition and ecosystem processes.

 

            We will experimentally alter the species composition of tree seedlings that establish after disturbance. In each of two recent burns (one wet =Survey Line Fire, one dry=FROSTFIRE), we will establish plots planted with seedlings of each major native tree species (black and white spruce, alder, aspen, birch, poplar, larch) and two exotic species that have been used extensively in forestry trials (lodgepole pine and Siberian Larch). We will establish three blocks of ten plots each and assign plots randomly to tree species within each block (randomized block design). We will collect seed locally in summer 2004. Seedlings of each species will be grown in the greenhouse for 6 months (winter 2004-05) in standard forestry Conetainers, then planted out at 1 m spacing in 10 x 10 m plots (3 replicate plots per tree species per site for a total of 300 trees per site). We will monitor seedling survival and height annually for 6 years, then every three years. Organic matter depth and soil moisture, measured in 4 points per plot, will be used as covariates to explain patterns of seedling success. The plot will be the unit of replication. Seedlings that colonize naturally will be weeded from all except the control (unplanted) plots. We intend to maintain these plots indefinitely, so we can follow the ecosystem consequences of alternative successional trajectories in terms of species composition, herbivory, and biogeochemistry.

In addition, we will continue monitoring floodplain plots in which alder and white spruce were planted and maintained (or excluded) for 15 years (see artificial communities under long-term experiments)