Modelling the coexistence gain and interactions of populations in Taxodium ascendens-intercrop systems

Coexistence gain and interaction of populations were studied using 9 years' data from field experiments of Taxodium ascendens-intercrop systems in Lixiahe; Jiangsu Province, China. A model framework was developed to describe the coexistence gain and interaction of populations in T. ascendens-intercrop systems. The coexistence gain defined by the present study suggests that a deliberately designed agroforestry system is expected to obtain the coexistence gain by exploiting the positive interaction and by sharing the available resources. Facilitation and resource sharing were identified as main contributions to the advantage of species combination in agroforestry. The model of population interactions developed in the present study was compared with the GA-model and the LV-model. This new model was accepted for describing the interaction of populations in T. ascendens-intercrop systems because it explained a high proportion of variance of experimental data and was able to simulate the biomass dynamics, well fitted to the observed data in most of intercropping types. Moreover this model can take the GA-model as a special case when psi = 1.0 and the LV-model as a special case when theta = 1.0 and psi = 1.0, providing a flexibility for describing different patterns (linear or nonlinear) of intra-and inter-specific interactions. The coefficients (e.g. psi and alpha) in the model demonstrated interesting implications which could be used to determine the ecological combination of multi-species. (C) 1998 Elsevier Science B.V. All rights reserved.