def interval_string(intLower, intUpper):
    """ Return string based on upper and lower canopy cover height cutoffs. """
    strLower = str(intLower)
    if intLower:
        strLower = str(intLower).replace('.', 'p')
    strUpper = str(intUpper)
    if intUpper:
        strUpper = str(intUpper).replace('.', 'p')

    return strLower + '-' + strUpper