Mathematical modeling of ecosystem carbon storage capacity under typhoon disturbance in a subtropical evergreen broadleaf forest.

Disturbances have been considered as a main ecological factor shaping terrestrial ecosystem states and dynamics. Particularly the typhoon disturbances, destabilizing coastal forest ecosystem, have been observed to be severer and more frequent in recent years. Consequently, to have a better understanding about the causes of variation of forests and to predict the growing trend of forest ecosystem, we treat typhoon disturbances as Poisson process, with a disturbance interval (λ) and a disturbance severity (s). We attempt to carry out quantitative assessments on the structure, functioning and productivity of forest ecosystem under typhoon disturbance with the derivation solution E[X]=Uτ_E·(λ⁄(λ+sτ₁))+Uτ₁·(λs⁄(λ+sτ₁))·((τ₂+τ₃η)⁄(λ+τ₂)),where E[X] stands for the expectation of ecosystem total carbon, U is ecosystem carbon influx, η is the fraction of carbon transferred to the soil organic matter (SOM) pool from the litter pool, τ_E is ecosystem carbon residence time, and τ₁,τ₂,τ₃ are the residence time of the carbon pool of biomass, litter, SOM, respectively. We focus the study on an intact old-growth subtropical forest in Tiantong mountain (29°48'N, 121°47'E), which is the ideal place for evaluating the influence of typhoons on dynamics of evergreen broadleaf forests (EBFs). Meanwhile, the local observations also help us constrain the estimates of U,τ₁,τ₂,τ₃. According to the analytical solution, we summarize that a) Ecosystem carbon content would decay by power exponent relate to the disturbance severity, but the trend weakens when the disturbance interval increase. b) The magnitude of litterfall increment caused by typhoons is much smaller than that of decrement of biomass with increasing severity. c) Incorporation of the typhoon regime will improve the projection of ecosystem carbon dynamic in the coastal forests in eastern China.