Terrain shape index: quantifying effect of minor landforms on tree height
In the southern Appalachians, the distribution and growth of trees are highly correlated with local topography, but the relationships have been ditficult to describe quantitatively. A quantitative expression of the geometric shape of the land surface (terrain shape index) is described and correlated with oventory tree heights and site quality. Application of the index in three even-aged stands of yellow-popular (Liriodendron tulipifera L.) on high-quality uniform sites shows that it is highly correlated with total height of trees in a stand, with 9 ranging from 0.45 to 0.74. In comparisons among stands, the index accounted for an average of 51% of the variation in site index. The relationship was validated in two supplementary stands and accounted for about 49% of variation in site index. The terrain shape index was more accurate in predicting tree height than was lateral shape class, a subjective measure of slope shape occasionally used in soil-site studies.