2.2 Seasonal growth

Contrasting seasonal growth responses to elevated CO2 and temperature in certain species suggests that pasture management may change in the future.

The grazing season may be prolonged, but whole-season productivity may become more variable than today. This is shown by studies of perennial ryegrass where, in spring, increased leaf extension occurred in elevated CO2 whilst in summer it was reduced. In high temperature it was reduced in both seasons.

In elevated CO2 × temperature, leaf extension increased in spring, whilst in summer it decreased. Many organisms are near their tolerance limits and some may not be able to persist under hotter conditions. Higher temperatures in arid regions with cold winters may mean spring growth occurs earlier. Water reserves gained during the winter may, in some cases, be depleted earlier.

2 The effect of elevated CO2 and climatic extremes on plant growth

2.3 Climate change and agriculture