does it have to be a flow chart? I always found that biophysical interactions were better described using a venn diagram.
The question you ask is fairly specific. But if you think of the natural processes of each sphere then you should be able to see some interactions form.
Eg: the hydrosphere is all about storages and flows. How do various storages/flows interact with the other spheres (NB: evaporation and precipitation counts as a flow, but it is also an interaction with the atmosphere). When it rains (atmosphere/hydrosphere), this provides water for plants (biosphere - flora and fauna) but can also cause erosion (lithosphere - includes weathering[both physical and chemical] and erosion etc.). Water may also leech nurtrients from the soil as it flows through the soil. This can also impact upon the plants. If plants lack essential nutrients they die and are decomposed (also a biophysical process) to return nutrients to the soil (lithosphere).
The example i gave is a VERY general one and as such may not be suited to your specific case study. Hopefully, however, you might be able to see that it is quite simple to identify biosphysical interactions. Start with one sphere and show how it interacts with the others as it carries out it's characteristic processes. In the next paragraph, choose a different sphere and discuss its interactions.
Hope this helps you somewhat.
good luck.
