Harvest impacts to stand development and soil properties across soil textures: 25-year response of the aspen Lake States LTSP installations

In addition to long-standing concerns about sustaining forest productivity, maintaining forest ecosystems under changing conditions and emerging threats has become increasingly important when planning forest management. With the aim of understanding effects of management on both productivity and recovery, we quantified the 25-year impact of varying degrees of organic matter (OM) removal and soil compaction on above-ground biomass, soil carbon and nutrients, soil bulk density, and stand development in aspen-dominated forests in the upper Lake States region of the US. Treatment impacts were assessed at three different sites with comparable overstory composition, but with varying soil texture, site quality, and climate. Across all sites, soil C and N generally decreased with increasing OM removal, and bulk density increased with increasing compaction; 25year observations indicate recovery of bulk density at the surface (0-10 cm) but not at deeper portions of the soil profile. At the most productive site (loamy soils) with favorable initial soil porosity, severe compaction decreased mean aboveground biomass (-46%), particularly of trees (-73%). Biomass at 25 years did not differ among organic matter removal treatments (e.g. stem-only harvest), but a greater increase in soil C occurred with stem-only harvest relative to whole-tree harvest plus forest floor removal. In contrast, at a less productive site with sandy soils poorly buffered to nutrient and C removals, whole-tree harvest reduced biomass by 25% (tree biomass declined 35%) relative to stem-only harvest while compaction treatments did not differ in effects on biomass production, soil C or soil N. On clay soils, compaction treatments did not significantly impact biomass production, but whole-tree harvest plus forest floor removal reduced tree biomass by 47% relative to whole-tree harvest alone. Assessment of mean relative density indicates canopy closure has not yet occurred at the least productive site (clay soils) or the more severely disturbed stands at the intermediate site (sandy soils), suggesting the possibility for treatment impacts not yet discernible to become more pronounced as stands develop and nutrient uptake continues in the future. Our results align with concepts of soil quality and texture-specific limitations to growth, underlying a need to understand key soil limitations when considering forest management impacts to aboveground structure and productivity.

Automated summary

Our study shows that the impact of management on forest productivity and recovery is influenced by factors such as soil texture, quality, and climate. Different management treatments had varying effects on above-ground biomass, soil carbon and nutrients, soil bulk density, and stand development in aspen-dominated forests. Understanding soil limitations is crucial when considering forest management impacts.