© 2000 Heron Publishing—Victoria, Canada
Forest growth and species distribution in a changing climate
Miko U. F. Kirschbaum (1)
1. CSIRO Forestry and Forest Products, PO Box E4008, Kingston ACT 2604, Australia (Miko.Kirschbaum@ffp.csiro.au) / Received March 24, 1998
Summary
Climate change has many potential effects on plants, some detrimental to growth, others beneficial. Increasing CO2 concentration can increase photosynthetic rates, with the greatest increases likely to be in C3 plants growing in warm dry conditions. Increasing temperature directly affects plant growth through effects on photosynthetic
and respiration rates. However, plants have a considerable ability to adapt to changing conditions and can tolerate extremely
high temperatures, provided that adequate water is available. Increasing temperature may increase vapor pressure deficits
of the air, and thereby increase transpiration rates from most plant canopies. Effects are likely to vary among plant communities,
with forests generally experiencing greater increases in transpiration rates than grasslands. These increases in transpiration
are likely to be reduced by stomatal closure in response to increasing CO2 concentration. In many areas, precipitation will probably increase with global warming; however, these increases may be insufficient
to meet the increased transpirational demand by plant canopies. Increasing temperature is likely to increase soil organic
matter decomposition rates so that nutrients may be more readily mineralized and made available to plants. In highly fertile
systems, this could lead to nutrient losses through leaching.
For different combinations of increases in temperature and CO2 concentration, and for systems primarily affected by water or nutrient limitations, different overall effects on plant productivity
can be expected. Responses will be negative in some circumstances and positive in others, but on the whole, catastrophic changes
to forest growth seem unlikely under most conditions.
In contrast,ecological consequences of climate change are potentially more serious. The distribution of many species tends
to be limited to a narrow range of environmental conditions. Climate conditions over much of a species' current natural range
may therefore become unsuitable, leading to significant decline of forests or of particular species within forests.
Keywords:
CO2, global warming, greenhouse gases, mineralization, photosynthesis, transpiration.
