Our magnificent forests of today are linked to those first early forests. Perhaps a hundred generations of trees separate the low elevation fire-regenerated forests of the Interior from those first colonizing individuals. On the coast there may be even fewer generations of some long-lived species because of the greater time between major disturbances. This molecule contains the codes for growth, development and reproduction. Variations in its structure provide the wealth of genetic variation that we find in almost all living things.
Genetic variation is critical to the ability of organisms to accommodate changes in the environment.
Geological history tells of many major and minor fluctuations in climate, even since the last glaciation. Cool summers were prevalent from 800 to 600 years ago, followed by a period of warm, dry summers until about a 100 years ago. Now we are in another warming trend. These fluctuations in climate mean that the offspring of long-lived trees often establish in very different environments than did their parents. As well, trees grow in a wide range of ecosystems and must accommodate daily, seasonal, and longer-term variations in environment.