Why does partially decomposed organic matter build up in taiga soils?

In the taiga, partially decomposed organic matter builds up primarily because of the region's cold climate, which significantly slows the rate of decomposition.12

Several factors contribute to this accumulation:

• Low Temperatures: Cold soil temperatures limit biological activity, meaning that organic matter breaks down much more slowly than in warmer ecosystems.12
• Acidic Conditions: The conifer litter that covers the forest floor is highly acidic. This acidity further inhibits the organisms responsible for breaking down organic material, resulting in a surface layer of raw, slowly decomposing humus.32
• Permafrost and Drainage: In many areas, permafrost or iron-rich hardpans impede drainage, creating waterlogged, oxygen-poor environments like peat bogs and swamps. These conditions are particularly unfavorable for the microbes that facilitate decomposition, leading to the buildup of organic soils known as histosols.32

Because decomposition is so sluggish, these soils act as a massive reservoir for carbon, storing significant amounts of organic matter that has not yet fully broken down.1