The state of the terrestrial biosphere during the Holocene and the Last Glacial Maximum (LGM) was estimated from pollen data bases and steady state simulations in former studies. However, the amount of carbon bound in the terrestrial stocks varied considerably.Here, we narrow down this range of terrestrial carbon at the LGM by a transient simulation study over the last glacial cycle (125 kyr) and try to determine the amplitudes of the possible different driving forces (temperature, atmospheric carbon dioxide partial pressure and sea level).We developed a simple model of the terrestrial biosphere consisting of seven well-mixed boxes.By applying well defined boundary conditions of the total terrestrial carbon stock, average isotopic signature, and net primary production, the range of the terrestrial carbon at LGM can be focused to 1500--1700 PgC, equivalent to a reduction from interglacial times to the LGM of 500--700 PgC. This falls well within the range of former studies (LGM: 1100--1900 PgC) but reduces the range of uncertainty significantly. Simulation results were biased towards higher carbon stocks (+120--150 PgC) if we abstained from our transient modeling approach and analyzed steady states. This disequilibrium effect give us reasons to argue for considering the time-dependent nature of any driving forces, since fast temperature changes in the northern hemisphere, where 2/3 of all land area is situated, did prevent the system from reaching equilibrium.