How are water content and matric potential related?
The answer can be found in the text Miller & Gardiner (p. 117, Figure 4-5). At saturation, the water potential is zero. Lowering the water content to field capacity, to the wilting point 1 and, finally, to oven-dry creates a negative water potential 1. At water contents above field capacity capillary forces 1 (which draw water into small pores) and gravity forces both affect the water potential, but below field capacity gravity has little effect and capillary forces (the matric potential 1) is dominant. See Miller & Gardiner (pp. 112-113).
