Effects of simulated post-harvest light availability and soil compaction on deciduous forest herbs

To better understand the response of eastern deciduous forest herbs to microenvironmental changes associated with logging, the effects of experimental light and soil compaction treatments were examined in six herbaceous plant species characteristic of varying successional stages. We found severe growth reductions and increased mortality of Osmorhiza claytonii (Michx.) C.B. Clarke, a shade-tolerant forest perennial, when grown in full sun and greater soil compaction. Deeply shaded conditions, similar to those beneath regenerating forests, resulted in reduced growth of early successional species such as Galium aparine L., and Eupatorium rugosum Houtt. Growth of other species such as Geum canadense Jacq., and Elymus hystrix L. appeared to increase in the patchy, intermediate light treatment mimicking mature eastern deciduous forests. Soil compaction caused severe reductions in height and biomass of Eupatorium rugosum and O. claytonii, early- and late-successional species, respectively. While harvested stands experience relatively uniform light environments, canopy gaps and sunflecks in mature eastern deciduous forests create heterogeneous light environments often correlated with recruitment, growth, and diversity of understory herbs. Therefore, management approaches that minimize alteration of forest environments and mimic natural disturbance patterns may be important to the maintenance and regeneration of forest herbs.