Systems ecology is sufficiently developed today to offer a consistent theory about ecosystem function due to the contributions from a number of system ecologists during the last forty to fifty years. During the last five years, additional important contributions to systems ecology have been published in "Ecological Modelling" in the areas of hierarchy  theory, landscape processes, and thermodynamic indicators. For example, research showed that hierarchcal organization has an important damping effect in the higher levels  on disturbances occurring in the lower levels and that the damping effect increases with increasing bodiversity; this result is consistent with experimental and model results. A first attempt has been made to integrate hierarchical and network theory on the levels of ecosystems/landscpes using model experiments. The model experiments point toward an expansion of the Ecological Law of Thermodynamics (ELT) to ecosystems developing on the landscape, where it previous was shown valid for populations fitting in an ecosystem.  Regarding thermodynamic indicators of ecological organization, flow transfers were used to quantify the usable work energy, including the work energy of information, in ecological  networks. In particular, this new approach included the cycling of information, which is changed by tansfers of work energy due to different values of the donors and the receptors.  These changes, however, distribute to all the components of the network. The cardinal network hypothees proposed by B. Patten have been expanded (published in this issue of  Ecological Modelling) and it has been shown that both the maximization of power (the flows of useful work energy) and the maximization of the storage of usable work energy including  that of information in ecosystems' networks are valid and complementary. This result represents a first integration of the Maximum Power Hypothesis and the Ecological Law of  Thermodynamics with Network Theory, and it is presumed that a complete integration of all three theories, hierarchical, network and thermodynamic, could be expected in the coming years.