Vegetation Composition Determines Microbial Activities in a Boreal Forest Soil

Area of Science:

• Forest ecology
• Soil science
• Microbial ecology

Background:

• Reindeer grazing significantly alters Fennoscandian dry Scots pine forest ecosystems.
• Understanding the relationship between vegetation composition, soil properties, and microbial activity is crucial for forest health.

Purpose of the Study:

• To investigate the correlation between site productivity, vegetation composition, and microbial activities in reindeer-grazed forests.
• To assess the impact of grazing intensity on Scots pine fine roots and soil microbial functions.

Main Methods:

• Non-metric multidimensional scaling (NMDS) was used to analyze relationships between vegetation, soil microbial community, fine roots, soil nutrients, and tree growth.
• Key variables measured included basal respiration (Bas), metabolic quotient (qCO2), microbial biomass (Cmic), fungal biomass, and fine root parameters.

Main Results:

• Basal respiration and metabolic quotient increased towards ungrazed, lichen-dominated sites, linked to high fine root production and slow litter decomposition.
• Soil nutrients, tree growth, and humus layer thickness increased towards bryophyte-dominated sites, indicating higher substrate availability and decomposition.
• Grazed sites exhibited lower respiration and metabolic quotient, potentially due to reduced carbon input and microclimatic changes.

Conclusions:

• Fine root exudates are a primary driver of microbial activity in nutrient-poor, lichen-dominated pine forests.
• Easily decomposable substrates and higher nutrient concentrations support microbial activity in bryophyte-dominated sites.
• Reindeer grazing influences soil microbial communities and functions through altered vegetation and microclimate.