Transfer of mass and energy in a cassava community (Manihot esculenta Crantz cv. Cubana). 2. CO2 exchange in a savanna climate | Transfer of mass and energy in a cassava community (Manihot esculenta Crantz cv. Cubana). 2. CO2 [carbon dioxide] exchange in a savanna climate
1983
San Jose, J.J. | Berrade, F.
The energy balance approach was applied to calculate the CO2 flux above and within a cassava community, growing during a savanna wet season. Data of the response of CO2 exchange to diurnal changes in the savanna environment were integrated to a growth analysis of the cassava crop. The carbon budget of the entire community was calculated at different development stages. Results indicate that CO2 uptake in cassava appears to follow a linear net radiation response curve, dependent on crop age. The maximum net CO2 uptake decreased from 0.195 MJ m−2 day−1 at maximum leaf area development (August) to 0.028 MJ m−1 day-1 2 months later. These rates represent 41 and 19 per cent gross assimilation. Data of energy conversion efficiency show that at a maximum leaf area development, the crop fixed 2.2 and 0.9 per cent Rt as gross (εg) and net photosynthesis (εn) respectively. As the season proceeded,εn decreased to 0.1, whereas εg decreased to 0.7, which indicates that dry matter lost by respiration is one of the determining factors in the seasonal trend of efficiency changes. The comparison of growth characteristics calculated for cv. Cubana, growing during consecutive years in the same experimental site, indicate that yearly variability in dry matter accumulation is due to the wide range of environmental conditions present during the savanna wet season. Operational factors acting depressively on the cassava carbon budget and affecting dry matter production were also analysed.
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