9. Potential effects of global climate change on cool season food legume productivity
Publ. of the Dep. of Production Ecology, P.O.B. 430, 6700 AK Wageningen and Centre for Agrobiological Research, P.O. 14, 6700 AA Wageningen, Netherlands, 1992, 18 pp + Annex
In this paper a feasibility study of effects of climate change on growth and production of faba beans is described.
The increasing presence of atmospheric trace gases such as CO2, CH4 and N2O due mainly to human activity, directly or indirectly, may influence the Earth's climate by transmitting incoming solar radiation, while partly blocking outgoing terrestial black body radiation. The increased "greenhouse" effect may cause temperature rise. This may affect the functioning of various agro-ecosystems in general and faba bean growing more specifically.
Different processes are influenced by various factors that are affected by climate change. CO2-increase affects the stomatal conductance and increases photosynthesis rate and water use efficiency. Temperature rise may increase development rate of the crop, resulting in an adverse effect on crop production. Evaluation of the effects which work in contrary directions with direct qualitative or quantitative methods is difficult. Crop growth simulation models may be used for such an evaluation as the causal relations between rate variables and forcing variables is present in such models. The consequences of CO2-increase and temperature rise may be evaluated with these models.
Climate change may have strong effects on faba bean growing, as this crop is very sensitive to water shortage and has a high yield variability at the present climate.
A simulation study was done with a well tested and validated model for crop growth and production of faba beans.
The used model was a version of SUCROS87, including a water balance.
For three locations differing in climate (Tel Hadya, Syria; Migda, Israel; Wageningen, Netherlands) at least 8 years with detailed weather data were used to simulate the consequences of temperature rise and increase of atmosheric CO2 (based on assessment of the Intergovernmental
Panel on Climate Change IPCC), separately and combined. It appears that temperature rise causes a decrease in seed yield of rain-fed crops in Wageningen and Migda, due to a shortening of the growing season. At Tel Hadya, seed yield of rain-fed crops increases, due to an accelerated start of the reproductive phase and consequently an 'escape' from water shortage later in the season. For fully irrigated crops, temperature rise causes at all locations a decrease in seed yield, most in Migda, and smallest in Tel Hadya. CO2-enrichment causes in all situations an increase in growth and production of faba beans, which compensates the decrease due to temperature rise. The effects are not completely additive at all locations. Yield increases due to CO2-enrichment are much higher than the yield decrease due to temperature rise. In Wageningen, Tel Hadya and Migda the positive net effect of the two considered effects is respectively 12%, 68%, 28% for rain-fed crops and 5%, 16%, 13% for fully irrigated crops, assuming an increase of CO2 concentration to 460 ppm and a temperature increase of 1.7 C. Fully irrigated crops show a remarkably smaller yield variability than rain-fed crops in all these assessments. In rain-fed crops, the variation in yield over the years stays the same or is somewhat reduced due to the reduced sensitivity to water shortage. Thus the net effects on productivity and stability due to the scenarios used for global climate change are at all locations positive. Other effects, such as for example morphological effects may overrule these physiological effects.
Such effects are not taken into account in this study.
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