Temperature extremes: Effect on plant growth and development

The major impact of warmer temperatures was during the reproductive stage of development and in all cases grain yield in maize was significantly reduced by as much as 80?90% from a normal temperature regime. Temperature effects are increased by water deficits and excess soil water demonstrating that understanding the interaction of temperature and water will be needed to develop more effective adaptation strategies to offset the impacts of greater temperature extreme events associated with a changing climate.

The impacts of climate change are most evident in crop productivity because this parameter represents the component of greatest concern to producers, as well as consumers. Changes in the length of the growth cycle are of little consequence as long as the crop yield remains relatively consistent. Yield responses to temperature vary among species based on the crop’s cardinal temperature requirements. Warming temperatures associated with climate change will affect plant growth and development along with crop yield.

However, as air temperatures rise beyond the optimum, instead of falling at a rate commensurate with the temperature increase, crop yield losses accelerate. For example, an analysis by Schlenker and Roberts (2009) indicated yield growth for corn, soybean, and cotton would gradually increase with temperatures up to 29°C to 32°C and then sharply decrease with temperature increases beyond this threshold.

The current evaluations of the impact of changing temperature have focused on the effect of average air temperature changes; however, increases in minimum air temperature may be more significant in their effect on growth and phenology (Hatfield et al., 2011). Minimum air temperatures are more likely to increase under climate change (Knowles et al., 2006). While maximum temperatures are affected by local conditions, especially soil water content and evaporative heat loss as soil water evaporates (Alfaro et al., 2006), minimum air temperatures are affected by mesoscale changes in atmospheric water vapor content. Hence, in areas where changing climate is expected to cause increased rainfall or where irrigation is predominant, large increases of maximum temperatures are less likely to occur than in regions prone to drought. Minimum air temperatures affect nighttime plant respiration rates and can potentially reduce biomass accumulation and crop yield (Hatfield et al., 2011). Welch et al. (2010) found higher minimum temperatures reduced grain yield in rice, while higher maximum temperature raised yields; because the maximum temperature seldom reached the critical optimum temperature for rice. However, under the scenario of future temperatures increases, they found maximum temperatures could decrease yields if they are near the upper threshold limit.

"The more greening you get, the more warming you expect," said Richard Pearson, lead author of the study and a research scientist at the American Museum of Natural History in New York City. The National Science Foundation funded part of the research.

The main driver of the projected warming is that trees and tall shrubs cover the landscape, making it dark, according to Michael Loranty, a study co-author and an assistant professor in the department of geography at Colgate University. Solar radiation is then more easily absorbed in these dark areas, rather than hitting snow and being reflected back into space.