Study reveals key drivers of carbon storage in boreal forests

Boreal forests, often referred to as the "taiga," are vast ecosystems that stretch across the northern hemisphere, storing 25% and 40% of the global terrestrial carbon in their soils. However, the amount of carbon stored in these soils can vary greatly due to a complex interplay of factors such as vegetation composition, hydrotopography, and soil properties. A recent study published in Forest Ecosystems by researchers from the Norwegian University of Life Sciences and the Norwegian Institute of Bioeconomy Research provides new insights into the factors influencing carbon storage in boreal forests, particularly focusing on the roles of forest type, fire history, and soil properties.

The researchers collected soil samples from 595 plots across the study regions and compared the organic layer carbon and charcoal carbon stocks in two regions of south-central Norway (Trillemarka and Varaldskogen). Structural equation modeling (SEM) was employed to explore the interplay between vegetation composition, hydrotopography, and soil properties.

The study found that pine forests had consistently larger organic layer carbon stocks than spruce forests. Charcoal carbon stocks, however, varied more across forest types and regions. In Trillemarka, pine forests had higher charcoal carbon stocks than spruce forests, while in Varaldskogen, both forest types had similar charcoal carbon stocks. The researchers also discovered that both organic layer carbon and charcoal carbon stocks increased with higher fire frequencies over the past 600 years.

Several key drivers of carbon storage were identified. Vegetation composition, terrain slope, and soil moisture were found to be the most important factors influencing organic layer carbon stocks. Charcoal carbon stocks were primarily controlled by the depth of the organic layer. Microtopography also played a significant role, with depressions in the forest floor accumulating more charcoal carbon than well-drained areas.

The findings of this study have significant implications for forest management and climate change mitigation strategies. By understanding the factors that influence carbon storage, forest managers can make more informed decisions to enhance carbon sequestration and storage in boreal forests.

The study also underscores the importance of considering local conditions and forest history when developing management practices. Dr. Vilde L. Haukenes adds, "Boreal forests are highly variable, and what works in one region may not be effective in another. This emphasizes the need for more localized forest management strategies." The organic soil and charcoal carbon stocks are likely context-dependent, and it is hard to draw definite conclusions about any general relationships between the organic soil pool and the charcoal soil pool, as the study concludes.

This research was funded by the Norwegian University of Life Sciences (NMBU) and a strategic institutional research program at the Norwegian Institute of Bioeconomy Research (NIBIO).