Complex sentence: Due to the nature imagery associated with the Green Knight, scholars have seen the ceremony as possibly deriving from his famous beheading in the "Gawain" poem, the quane removal being symbolic of the loss of the knight's head.
Split into simpler sentences: Due to the nature imagery associated with the Green Knight, scholars have seen the ceremony as possibly deriving from his famous beheading in the "Gawain" poem. In this case, the quayne removal is symbolic of the loss of the knight's head.