Abstract
Tree growth and competition with other vegetation are strongly affected by leaf area, which can be modified by livestock browsing in silvopastoral systems. We studied the relationship of leaf area to stem diameter and sapwood area of koa (Acacia koa), a valuable hardwood tree species native to Hawaii. Because browsing alters allometric relationships, we compared harvest data with two non-destructive optical techniques (LAI-2000 canopy analyzer and photographic estimation of projected crown area). Destructive harvests of 30 trees showed that leaf area was equally well correlated with the diameter at breast height (dbh) or sapwood area of trees ranging from 2 to 16 cm in diameter, 1.3 m above ground level. Both optical techniques correlated with the leaf areas obtained by destructive analysis, but the photographic estimation of projected crown area provided more reliable estimates than the canopy analyzer. The photographic method based on projected crown area provided reliable estimates of leaf area removal within the browse zone (less than 2 m height). this method provides a simple, low-cost means of obtaining non-destructive estimates of changes in leaf area in isolated trees.
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Grace, K.T., Fownes, J.H. Leaf area allometry and evaluation of non-destructive estimates of total leaf area and loss by browsing in a silvopastoral system. Agroforestry Systems 40, 139–147 (1998). https://doi.org/10.1023/A:1006064103080
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DOI: https://doi.org/10.1023/A:1006064103080