PAR absorption and its relation to above-ground dry matter production of Sitka spruce.
Abstract
For 6 Sitka spruce (Picea sitchensis) plots with various thinning (no thinning or half trees and one-third of basal area removed) and fertilizer (control, 200 kg/ha of N as urea or 100 kg/ha of P as rock phosphate) treatments in central Scotland, annual above-ground biomass production over 4 yr was proportional to annual amounts of PAR absorbed, irrespective of treatments. Quotients of above-ground dry matter produced and PAR absorbed were 0.43 g/mol for N-fertilized plots and 0.33 g/mol for the other plots. For Sitka spruce, annual photosynthetic efficiency was estimated to be about 3% using a physiological process-based model (MAESTRO), and the upper limit of biomass production in Scotland was estimated to be 36 t/ha.