Publication

Information from horizontal quantum sensor arrays and data on forest structure was used to measure photosynthetically active radiation (PAR). Forest sites with stands of similar age and land-use history were blocked into three valley, three mid-slope, and three ridge topographic positions. Analysis of forest structure and light measurements demonstrate: (1) canopy height and leaf area index decreased on progressing from valley to ridge; (2) total understory radiation increases on progressing from the valley to ridge; (3) sunflecks contribute a disproportionate amount of photosynthetic photon flux (PPF) on sunny days (40-80%) with number and duration of sunfleck periods increasing from valley to ridge. (C) 2003 Elsevier Science B.V. All rights reserved.