CA Civ Proc Code Section 323

For the purpose of constituting an adverse possession by any person claiming a title founded upon a written instrument, or a judgment or decree, land is deemed to have been possessed and occupied in the following cases:

1.Where it has been usually cultivated or improved;

2.Where it has been protected by a substantial inclosure;

3.Where, although not inclosed, it has been used for the supply of fuel, or of fencing timber for the purposes of husbandry, or for pasturage, or for the ordinary use of the occupant;

4.Where a known farm or single lot has been partly improved, the portion of such farm or lot that may have been left not cleared, or not inclosed according to the usual course and custom of the adjoining country, shall be deemed to have been occupied for the same length of time as the part improved and cultivated.