| Popis: |
The seasonal development of a bracken canopy was measured over 7 years between 1980 and 1992. The object of the investigation was to relate the cumulative development of green above-ground biomass to cumulative absorbed photosynthetically active radiation (APAR). During the vegetative phase, APARwas described by an empirical expression (Monski and Saeki, Japanese Journal of Botany14: 22–32, 1953) relating APARto frond area, with a canopy extinction coefficient of 0.6. Values of above-ground biomass were linearly related to cumulative APAR, and the averaged radiation use efficiency (RUE) was 2.77 g MJ − 1, although there was variation from year to year. For above-ground carbon biomass, the average RUE was found to be 1.24 g C MJ − 1. The fraction of absorbed PARfAPAR was also shown to be non-linearly related to, and predictable from, a simple spectral reflectance ratio, RVI, by the relationship fAPAR = 0.0472 (±0.0017)RVI. Remote sensing RVI during the period of vegetative growth, either from satellite corrected data or from field spectroscopy, and its conversion toAPAR , will enable bracken biomass to be estimated directly and non-destructively using the RUE found here. |
