Conservation of Energy for systems involves thermal energy exchanges. Surface tension arises from hydrogen bonding between water molecules.
Pores can host gases, solutions, and microbiota.
The belowground atmosphere is distinct from the aboveground atmosphere by being typically richer in water vapor, carbon dioxide and other trace gases, and poorer in oxygen. This mixture of air and water within the pore volume leads to many air-water interfaces which create negative hydrostatic pressures and contribute to the matric potential.