Aspen development on similar soils in Minnesota and British Columbia after compaction and forest floor removal

Abstract

Forest management practices that decrease soil porosity and remove organic matter can reduce site productivity. We evaluated effects of four treatments—merchantable bole harvest (MBH) with three levels of soil compaction (none, light, or heavy), and total woody vegetation harvest plus forest floor removal (FFR)—on fifth-year regeneration and growth of aspen (Populus tremuloides Michx.) growing on soils with similar textures (20–40 cm silt loam over clay loam till) in northern Minnesota (MN) and northeastern British Columbia (BC). Overall mean sucker density was significantly greater in BC than in MN, and mean height was significantly lower. Soil compaction did not affect sucker density in BC, but significantly reduced it in MN, primarily due to late spring treatment. In BC, mean sucker heights generally decreased with level of compaction, but only the differences between non-compacted and the heavy compaction treatments were significant. On the MN plots, sucker heights were reduced significantly by compaction. Treatment responses were similar on both sites: (1) the greatest sucker densities were in the FFR treatment; (2) greatest mean heights were on the non-compacted MBH plots and were significantly greater than those in the FFR treatment; (3) sucker heights generally decreased with level of compaction; and (4) soil compaction decreased the number of suckers that had reached a dbh of 25 mm after five years and will likely delay future stand development and reduce site productivity. Key words: sustainable management, organic matter removal, soil compaction, aspen sucker density, height growth