The applicability of a color acetate film for estimating photosynthetic photon flux density in a forest understory

摘要

The suitability of a color acetate film for estimating photosynthetic photon flux density (PPFD) in a forest understory was examined. The fading ratio of the film (F), the total PPFD (PPFDtotal) to which the film was exposed, and the average daily maximum temperature during exposure (T) were obtained from measurements at multiple sampling points throughout an entire year within a natural secondary forest (n = 42). The ranges of the recorded values were as follows: F 35%–99%, PPFDtotal 1.4–28.3 mol m−2, and T 6°–32°C. PPFDtotal was regressed by F and T with a high r 2 (=0.94; P < 0.0001): PPFDtotal = (100 − F)/(1.085 + 0.051 T). The absolute error (|estimated PPFDtotal − measured PPFDtotal|) averaged 1.3 mol m−2 with a maximum of 5.7 mol m−2, indicating a good fit. These results indicated broad applicability of the film, both spatially and temporally, for estimating forest understory PPFD.