Wood Ash Induced pH Changes Strongly Affect Soil Bacterial Numbers and Community Composition

Area of Science:

• Forestry and soil science
• Microbiology
• Environmental science

Background:

• Wood ash recirculation from energy production enhances soil sustainability by returning nutrients.
• Wood ash application can benefit soils by neutralizing acidity but may perturb ecosystems.
• Impacts of wood ash on soil bacterial communities are not well understood.

Purpose of the Study:

• To investigate the effects of varying wood ash doses on spruce forest soil bacterial communities.
• To correlate bacterial responses with changes in soil pH, electrical conductivity, and nutrient content.

Main Methods:

• Applied wood ash at rates of 0, 5, 22, and 167 t ha^-1 to spruce forest soil.
• Used culture-based methods for enumerating general, Pseudomonas, and spore-forming bacteria.
• Employed 16S rRNA gene amplicon sequencing to analyze bacterial community composition and diversity.

Main Results:

• Wood ash significantly increased soil pH and electrical conductivity, with pH becoming alkaline at high doses.
• Bacterial numbers initially increased with ash application but decreased significantly at the highest dose (167 t ha^-1).
• Community composition shifted, favoring copiotrophic bacteria at moderate doses and a single alkaliphilic genus at high doses; bacterial richness and diversity decreased.

Conclusions:

• Wood ash application profoundly impacts soil bacterial communities, with effects directly linked to altered pH, electrical conductivity, and nutrient addition.
• Moderate wood ash application can stimulate bacterial growth, but high doses lead to community simplification and dominance by specialized alkaliphilic bacteria.
• Understanding these responses is crucial for sustainable forest management and the ecological implications of wood ash recycling.