Physiological performance and stand dynamics in managed red pine forests with complex stand structures

Ecologists and natural resource managers have developed an increasing awareness of the importance of structural complexity in forests to the conservation of biodiversity and sustainability of ecosystem functions. New forest management practices are being developed in response to this growing appreciation for structural complexity, including novel silvicultural approaches that emulate certain characteristics of natural disturbances to promote more natural patterns of structural development in managed forests. There is, however, a limited understanding of developmental processes in complex stand structures on which to base predictions of stand dynamics following the application of new management practices such as variable retention harvesting. This study examines the physiological performance and growth of seedlings and residual overstory trees following variable retention harvest treatments that produced different patterns of residual overstory structure in a managed Pinus resinosa forest.;Stable isotope and gas exchange data indicate variable retention harvesting increased intrinsic water use efficiency in seedlings by improving light-saturated photosynthetic (Amax) rates with minimal changes in stomatal conductance. Improvements in physiological performance were paralleled by increased seedling size. Variable retention harvesting also increased residual tree growth compared to trees in unharvested control stands. Stand-scale seedling performance and residual tree responses were generally similar regardless of the pattern of overstory retention, suggesting forest managers have considerable flexibility to adopt variable retention systems that meet a variety of needs. Variability in physiological performance within aggregated retention treatments, however, could lead to the development of structurally complex stands.