Study On Food Web Stability Based On Energy Budget And Dynamic Model

The stability of food web has always been the focus and frontier of ecological research.It plays a key role in the conservation of ecosystem and has attracted widespread attention from researchers.In this thesis,based on the data of real food webs in Somme Bay and Swartkops estuary,a food web dynamic model was constructed.By changing the model parameters,the food web stability and the possible regime shifts were discussed,providing a new idea for the study of food web stability.The main results of this research are described as follows:(1)On the basis of food web dynamic model,the dynamical complexity was analyzed by changing the model parameters to explore the food web stability.The relationships of extinction,living dependence,and species "coupling" and important energy flow paths among species were found in the food web of the Somme Bay.(2)Via decomposing the food web,nine food chains were obtained.The dynamical states of the food web and the food chains were studied and compared,and then the synchronization of these dynamical states was observed.At last the key food subwebs were determined.(3)By changing the gro wth rate parameters of the two producers in the food web of Somme Bay,it was found that complex dynamical behaviors,such as periodic and chaotic oscillation may emerge in the food web,further revealing that the occurrence of chaos always predicts the premonition of species extinction.(4)The variations of food web parameters can lead to the extinction of some species,resulting in the degradation of the original food web into a new subweb.Taking the Somme Bay as a case study,eight degraded food web structures were found and may indicate the occurrence of the regime shift.In this research,by developing the methods of changing the dynamic model parameters and decomposing food chains,the stability and regime shifts of the food webs in the Somme Bay and the Swartkops estuary were investigated based on the analysis of food web dynamical complexity.Moreover,the key food subwebs were extracted and the complex relationships between species as well as the energy flow paths resulting from the interactions between the species in the food webs were revealed.These reseults provided a new perspective on the research of food web complexity.