MCSE: Below-ground Net Primary Productivity
Sampling Frequency: Every fifth year
In annual crops soil excavations at the time of plant physiological maturity or maximum above-ground biomass are used to index below-ground primary productivity. A 0.5 × 0.5 m area is excavated to 0.5 m, and soil and roots are removed to the laboratory for hydropneumatic elutriation (Smucker et al . 1981). Washed roots are dried at 60 degrees C and weighed.
In perennial plots (trees, alfalfa, native succession), minirhizotron techniques are used to index belowground productivity. Permanently installed minirhizotron tubes are videotaped during the growing season and videotape images analyzed for root turnover at 1.2 cm intervals to a depth of 1.5 m.