Response of the soil microbial community and soil nutrient bioavailability to biomass harvesting and reserve tree retention in northern Minnesota aspen-dominated forests

Published Date

March 2016, Vol.99:110–117, doi:10.1016/j.apsoil.2015.11.001

Title 

Response of the soil microbial community and soil nutrient bioavailability to biomass harvesting and reserve tree retention in northern Minnesota aspen-dominated forests

• Author 

• Tera E. Lewandowski ^a,,
• Jodi A. Forrester ^a
• David J. Mladenoff ^a
• Anthony W. D’Amato ^b
• Brian J. Palik ^c

• aDepartment of Forest and Wildlife Ecology, University of Wisconsin, Madison, WI 53706, USA
• bThe Rubenstein School of Environmental and Natural Resources, University of Vermont, Burlington, VT 05405, USA
• cU.S. Forest Service Northern Research Station, 1831 Hwy 169 E, Grand Rapids, MN 55744, USA

Received 4 May 2015. Revised 3 November 2015. Accepted 4 November 2015. Available online 28 November 2015.

Highlights

• •
  Evaluated effects of biomass harvests on the soil microbial community and nutrients.
• •
  Harvests increased mycorrhizal fungi and reduced bacterial stress in years 2–3.
• •
  Harvesting increased NH₄ and reduced NO₃ bioavailability during years 1–2.
• •
  Increasing slash retention increased AMF, gram positive and actinomycete abundance.

Abstract

Intensive forest biomass harvesting, or the removal of harvesting slash (woody debris from tree branches and tops) for use as biofuel, has the potential to negatively affect the soil microbial community (SMC) due to loss of carbon and nutrient inputs from the slash, alteration of the soil microclimate, and increased nutrient leaching. These effects could result in lowered forest productivity and threaten the long-term sustainability of forest management. Retaining organic material post-harvest, including greater amounts of harvesting slash and live trees, within harvested areas may ameliorate some negative effects of biomass harvesting on soil processes. We evaluated the effects of biomass harvests with reserve tree and slash retention on the SMC and soil nutrient bioavailability (assessed using plant-root simulator probes) in trembling aspen (Populus tremuloides Michx.) forests in northern Minnesota during the spring and summer, 1–3 years after harvest. Variable biomass removal levels tested include complete removal (whole tree harvest of boles and branches), complete slash retention (bole only harvest), and 20% slash retention (amount suggested by regional biomass harvesting guidelines). Compared to the unharvested control, biomass harvests had no effect on the multivariate SMC composition or microbial biomass, but did result in a 1–4% increase in arbuscular mycorrhizal fungal abundance and reduced bacterial stress two and three years after harvest. Additionally, biomass harvesting increased NH₄ bioavailability during year one, and reduced NO₃ bioavailability during year two when compared to unharvested controls. Among the three biomass harvests with differing levels of slash removal there were few differences in overall SMC composition, microbial biomass, and soil nutrients; however, the abundance of arbuscular mycorrhizal fungi, gram positive and actinomycete bacteria were significantly higher in harvested treatments with more slash retained. These results are specific to single rotation biomass harvesting in aspen stands due to the unique relationships between plants and their associated SMCs, and may not be directly applicable to forest biomass harvesting of other commercial forest tree species, or multiple rotations.

Keywords

• Populus tremuloides
• Reserve tree patches
• Biomass harvest
• Soil microbial community
• Soil nutrient availability
• Slash retention

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• DOCX (204K)

• ⁎ 
  Corresponding author at: Department of Forest and Wildlife Ecology, University of Wisconsin, 1630 Linden Dr., Madison, WI 53706, USA. Fax: +1 608 262 9922.

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