Measurement and modeling of plant hydraulic conductance and solar radiation transfer processes in fruit tree orchards, with especial reference to sweet cherry.

摘要

Generic crop models such as CropSyst have the advantage that the same model can be used for different crops by changing the values of some key parameters. While CropSyst has shown good results on the simulation of growth and development of horticultural crops, its extension to fruit trees is in its early stages. Thus, the major goal of this study was the characterization and modeling of processes such as plant water transport and canopy radiant interception in fruit trees, a basic step in the development of a generic fruit tree model.; Regarding plant-water relationships, the hydraulic conductance (K) of mature sweet-cherry (Prunus avium L.) 'Bing'/'Gisela RTM 5' was determined from measurements of canopy gas exchange and leaf and stem water potentials. Total K was 60 +/- 6 mmol s-1 MPa-1. The soil-root K was 100 +/- 20 mmol s -1 MPa-1, while the stem-leaf K was 150 +/- 50 mmol s-1 MPa-1. Although a slight trend of hysteresis was observed when plotted transpiration against canopy water potential, the existence of a significant linear relationship suggests that water storage within the trees is not an important component of the cherry trees water balance.; With respect to canopy-radiation interaction, a model of radiation interception by fruit tree orchards was developed and evaluated for six cases involving grapevine, cherry, pear and apple trees at two locations (Pullman and Prosser, WA). The model adequately simulated fractional radiation interception on an hourly time step: mean absolute error, MAE = 10.08%; Willmot index of agreement, D = 0.94. When considered on a daily basis, the performance of the model improved: MAE = 4.47%; D = 0.98. Finally, two previously proposed methods for converting PAR transmittance (tauPAR) to global radiation transmittance (tauSg) and vice versa were evaluated using field data. The first method, based on a fixed ratio of extinction coefficients for PAR and S g, was superior in both hourly and daily comparisons (average relative errors of 7.97% and 2.84%) to the second method (average relative errors of 13.29% and 7.77%), which considers a fixed relationship between tau PAR and tauSg.