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Local Scale
Trees and soils can gain and lose carbon through different processes, shown in the diagram below. On balance, forests accumulate carbon in aboveground, belowground and soil pools over time. Soil carbon pools in forest lands and croplands can increase or decrease depending on inputs from plant-fixed carbon in leaves, stems and roots; human-related inputs (e.g., fertilizer); and type of management practice (e.g., conventional vs. conservation tillage).
Processes that affect agricultural soil carbon can also affect emissions of nitrous oxide (N2O) and methane (CH4), which are more potent greenhouse gases than CO2 on a per molecule basis.
In forests, carbon can be sequestered over decades or even centuries, until mature ecosystems reach a stage of carbon saturation; however, natural decay and disturbances such as fire or harvesting can release carbon back into the atmosphere as CO2. In agricultural soils, carbon can be sequestered for 15 years or longer, depending not only on the type of soil but also on the type, continuity and length of management practice.
Carbon from forests can also be stored in wood products like furniture
and housing lumber for years to decades. Thereafter, the carbon in wood
products may decay and be released as CO2 back to the atmosphere.
