How do old-growth temperate rainforests store large amounts of carbon?

Old-growth temperate rainforests are highly effective at storing carbon due to their significant biomass and complex ecosystem structure. Their capacity to sequester carbon is driven by several key factors:1

• Photosynthesis: Like all green plants, trees in these forests absorb carbon dioxide from the atmosphere to fuel photosynthesis, converting it into organic compounds that build their tissues.23
• High Biomass Accumulation: These forests contain an enormous quantity of living and fallen trees, mosses, and other plants. Because of their maturity, old-growth trees in temperate rainforests can produce even more biomass than those in tropical rainforests, allowing them to hold more than 900 metric tons of carbon per hectare.12
• Complex Stand Structure: Old-growth forests feature multiple canopy layers and a forest floor rich in deadwood and woody debris. This complexity supports a diverse range of organisms, including fungi, which contribute to the total carbon stored within the forest's biomass and soil.12

By maintaining these vast reservoirs, old-growth temperate rainforests provide a critical ecosystem service in regulating the global carbon cycle.2