def naslund_heightcurve(d, species, p=None):
    """
    Computes tree height from dbh using Näslund -equation parameterized by
    Siipilehto & Kangas, 2015 Metsätalouden Aikakausikirja
    Args:
        d - DBH, diameter at breast height (cm)
        species - 'pine', 'spruce', 'birch'
    Returns:
        z - scalar or array of tree heights (m)
    """
    para = {'pine': [2.0, 1.181, 0.247], 'spruce': [3.0, 1.703, 0.327], 'birch': [2.0, 1.014, 0.238]}
    if p is None:    
        p = para[species]
    
    z = 1.3 + d**p[0] / ( p[1] + p[2]*d)**p[0]

    return z