The Perfect Pairing: Early Stand Dynamics in Conventional Aspen and Mixedwood Forests in Northern Minnesota, USA

Abstract

In North America, mixedwood management is being increasingly considered by natural resource managers as an alternative to single species management for a variety of ecological, economic, and cultural reasons. In northern Minnesota, USA, natural resource managers are increasingly using treatments to establish mixedwood forests in aspen ( Populus tremuloides Michx , Populus grandientata Michx) dominated ecosystems by planting white spruce ( Picea glauca (Moench). However, little quantitative information is known regarding differences between stand structure and composition in conventional aspen and aspen-white spruce during early stand development. To provide greater clarity for managers, we sampled 40 aspen stands across a chronosequence of 0 – 20 years old in northern Minnesota. Stands received one of two treatments: conventional aspen management (20 stands) or mixedwood management which included planting of white spruce and early release (20 stands). Forest inventory data were collected on seedlings, saplings, overstory trees, and non-tree understory cover. Results found a tradeoff between higher regeneration density in aspen stands, but greater tree diameter growth and structural and compositional diversity in mixedwoods. White spruce-aspen mixedwood systems can provide opportunities for increased ecological services during early stand development without compromising on long-term timber-focused management goals. Study Implications Establishing white spruce-aspen mixedwood forests can be a valuable silvicultural management option for the Lake States region (Michigan, Minnesota, Wisconsin) of the US for managers aiming to transition away from single species systems. Mixedwoods were shown in this study to have higher compositional and structural diversity than monoculture aspen ( Populus spp.) stands, which other studies indicate can lead to additional ecological benefits such as greater climate resilience, diverse habitat for wildlife, resistance to pests, and diversity of important commercial timber products.

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