Biology And Ecology Of Sequoias, Economic Importance
Sequoias are species of coniferous trees in the genus Sequoia, family Taxodiaceae. Sequoias can reach enormous height and girth and can attain an age exceeding 1,000 years. These giant, venerable trees are commonly regarded as botanical wonders.
About 40 species of sequoias are known from the fossil record, which extends to the Cretaceous, about 60 million years ago. At that time, extensive forests dominated by sequoias and related conifers flourished in a warm and wet climatic regime throughout the Northern Hemisphere. Ancient fossil stands of sequoias and other conifers have even been found in the high Arctic of Ellesmere Island and Spitzbergen. This indicates a relatively mild climatic regime in the Arctic in the distant past, compared with the intensely cold and dry conditions that occur there today. Similarly, the famous Petrified Forest located in a desert region of Arizona is dominated by fossilized sequoia trees and their relatives that lived in that area many millions of years ago. Clearly, compared with their present highly restricted distribution, redwoods were abundant and widespread in ancient times.
Only two species of sequoias still survive. Both of these species occur in relatively restricted ranges in northern and central California and southern Oregon. The specific reasons why these species have survived only in these places and not elsewhere are not known. Presumably, the local site conditions and disturbance regime have continued to favor redwoods in these areas and allowed these trees to survive the ecological onslaught of more recently evolved species of conifers and angiosperm trees.
The ancient biomass of ancient species of the redwood family are responsible for some of the deposits of fossil fuels that humans are so quickly using today as a source of energy and for the manufacturing of plastics.