ISHS Acta Horticulturae 276: II International Symposium on Computer Modelling in Fruit Research and Orchard Management
A CARBON BALANCE MODEL FOR THE KIWIFRUIT VINE |
| Authors: | J.G. Buwalda, E.F. Walton, G.S. Smith |
| Abstract:
A model has been developed to describe quantitatively carbon acquisition and utilisation for the kiwifruit vine during the growing season. The model enables the assessment of 1) the influence of canopy form and growth on carbon acquisition (photosynthesis), and 2) the influence of environment and crop management on carbon partitioning and utilisation for maintenance and growth. The model program, written in TURBO PASCAL, allows the user to alter a range of input parameters and compute a daily whole-vine carbon balance, using hourly incident solar radiation and temperature data. Net canopy photosynthesis is modelled according to incident solar radiation, light attenuation through the canopy, and the total leaf area density. The seasonal pattern of growth of component organs of the vine has a large influence on the balance of carbon demand and supply. The model includes a pool of carbon reserves, which may augment daily carbon acquisition by photosynthesis. The depletion of carbon reserves during canopy expansion in spring, when photosynthesis is limited strongly by the leaf area density, is illustrated. Carbon partitioning within the vine depends on supply and demand. When the supply exceeds demand, carbon is partitioned to satisfy the demands of each organ. When demand exceeds supply, maintenance (respiration) demands are met first, and any remaining carbon is then used for growth, according to a partitioning priority of the component organs. Partitioning co-efficients, computed at each time-step, are dependent on the potential relative growth rate of each organ. If the carbon available is insufficient to meet even the maintenance respiration demands of the vine, a fraction of the biomass is shed. The model allows the impact of variations in environmental and management factors to be considered. This is illustrated by examining the effect of leaf area density on photosynthesis and net carbon gain, and the interaction between photosynthetically active radiation and leaf area density for daily carbon gain. Sensitivity analysis can also be used to identify the relative importance of various factors for the overall carbon balance. For example, altering the quantum yield has relatively little effect on the nature of the response of canopy photosynthesis to radiation. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
