What's the difference between below and belowground?

Below

Definition:

(prep.) Under, or lower in place; beneath not so high; as, below the moon; below the knee.
(prep.) Inferior to in rank, excellence, dignity, value, amount, price, etc.; lower in quality.
(prep.) Unworthy of; unbefitting; beneath.
(adv.) In a lower place, with respect to any object; in a lower room; beneath.
(adv.) On the earth, as opposed to the heavens.
(adv.) In hell, or the regions of the dead.
(adv.) In court or tribunal of inferior jurisdiction; as, at the trial below.
(adv.) In some part or page following.