Maintaining mid-tolerant tree species with uneven-aged forest management: 9-year results from a novel group-selection experiment

In forest ecosystems, disturbance intensity affects the ability of species with varying shade tolerances to successfully recruit into the overstory. Small openings (e.g. single treefall) perpetuate shade-tolerant species while larger openings (e.g. those created under group selection and other higher severity disturbances) enhance the abundance of shade-mid-tolerant and -intolerant species. Forty-nine modified group-selection openings in three size classes established during the winter of 2003/04 and 20 single-tree selection sites were re-evaluated in 2012 in order to determine: (1) how the densities of seedlings and saplings changed over time, (2) whether species composition differed between treatments and (3) whether the group-selection openings enhanced recruitment of underrepresented species, especially the mid-tolerant yellow birch (Betula alleghaniensis). Sugar and red maple (Acer saccharum and Acer rubrum) regeneration dominated at all sites and occurred in greater densities in the group-selection openings as compared with the single-tree selection sites. While yellow birch densities increased with opening size, survival and growth were likely inhibited by the drought conditions that have occurred since 2004. Ironwood (Ostrya virginiana) and black cherry (Prunus serotina) also benefited from opening creation. Consequently, while openings enhanced the representation of mid-tolerant species, they did not greatly alter the developmental trajectory of this forest type.