Dynamic disequilibrium of the terrestrial carbon cycle under global change.

In this review, we propose a new framework, dynamic disequilibrium of the carbon cycles, to assess future land carbon-sink dynamics. The framework recognizes internal ecosystem processes that drive the carbon cycle toward equilibrium, such as donor pool-dominated transfer; and external forces that create disequilibrium, such as disturbances and global change. Dynamic disequilibrium within one disturbance-recovery episode causes temporal changes in the carbon source and sink at yearly and decadal scales, but has no impacts on longer-term carbon sequestration unless disturbance regimes shift. Such shifts can result in long-term regional carbon loss or gain and be quantified by stochastic statistics for use in prognostic modeling. If the regime shifts result in ecosystem state changes in regions with large carbon reserves at risk, the global carbon cycle might be destabilized.