State-of-the-Art in quantifying fire disturbance and ecosystem carbon cycle

The magnitude and location of carbon sources and sinks in the terrestrial biosphere are far from certain.This uncertainty is partly due to the lack of our understanding of how natural and human disturbances affect the terrestrial carbon cycle.Fire disturbance has been identified as one of the most important factors that control ecosystem processes and hence the carbon cycle.In this paper,we have reviewed the state-of-the-art in quantifying fire disturbance and ecosystem carbon cycle,which covers four critical issues as follows:(1) fire-induced immediate carbon emission,(2) postfire change in Net Primary Production(NPP),(3) postfire change in soil respiration,and(4) modeling carbon dynamics in terrestrial ecosystems associated with fire disturbance.The Seiler Crutzen's model and its variety have widely been used for the estimation of fire-induced immediate carbon emission.These emission models usually compose of four variables: burned area,consumed biomass,carbon density and consuming efficiency.To determine the four variables is essential for accurately estimating fire-induced carbon emission.In the past two decades,great deals of efforts have been made to estimate burned area by using satellite data and to determine consuming efficiency by using field experiment.Large uncertainty still exists in estimating both consumed biomass and carbon density.NPP and soil respiration are two components that determine carbon source and sink in terrestrial ecosystems.Fire disturbance could influence NPP through altering physical environment as well as ecosystem structure.On the one hand,fire-induced change in the age structure of ecosystems could lead to a large deduction in NPP.On the other hand,NPP could progressively increase as ecosystem develops from young to mature.Fire disturbance may also alter soil respiration through influencing biological,physical and chemical properties of soils.The challenge we face is also how to manage fires which aim at reducing carbon emission and enhancing the ability of carbon sequestration by ecosystems.How to balance fire suppression and prescribed fire becomes a topic that interests to policy-makers and managers.Computer models have been used for scenario analyses that evaluate potential impact of different fire management practices on carbon storage in terrestrial ecosystems.From both scientific and management perspectives,therefore,it is essential to incorporate fire disturbance into ecosystem models.Recently,such models have been developed to address fire-ecosystem complex interactions.Most of these models,however,lack confidence in predicting changes in ecosystem structure and function after fire disturbance.Further advance in understanding fire-induced carbon dynamics at a large scale will clearly rely on the intensive interactions among field experiment,remote sensing and modeling.