Two main opposing forces affect a tree's height; one pushes it upward while the other holds it down. By analyzing the interplay between these forces, a team of biologists led by George Koch of Northern Arizona University calculated the theoretical maximum tree height or the point at which opposing forces balance out and a tree stops growing. This point lies somewhere between 122 and 130 m. On the one hand, the researchers found, trees in forests "desire" to grow as tall as possible to overtake neighboring trees and reach stronger sunlight. On the other hand, gravity makes it more and more difficult to haul water upwards from the roots to the canopy as the tree grows, and leaves thus become smaller near the top. They discovered that despite the moistness of the ground far below, the leaves at the treetops struggle to get enough water, so they are effectively living in a constant drought. The difficulty of getting water so far up into the sky is what ultimately constrains growth, suspects Koch's team. Although giant trees grow in both tropical and temperate regions, they are very restricted geographically and phylogenetically. All the known giant trees occur in mesic climates, but nearly all of them are found in three regions: western North America from California to British Columbia, Southeast Asia and southeastern Australia. The heights of the tallest trees in the world have been the subject of considerable dispute and much exaggeration. Modern verified measurements with laser rangefinders or with tape drop measurements made by tree climbers, have shown that some older tree height measurement methods are often unreliable, sometimes producing exaggerations of 5% to 15% or more above the real height. Historical claims of trees growing to, and even, are now largely disregarded as unreliable, and attributed to human error. The following are the tallest reliably measured specimens from the top species. This table shows only currently standing specimens:
Other tree species above 75m
Historical records of giant tree species:
Corymbia maculata; there is an old reference to a tall tree. Flowering plant is native to eastern Australia.
Allantospermum borneense; tree, to tall. Flowering plant native to Southeastern Asia.
Alstonia pneumatophora; the tallest specimen reported measures. Flowering plant native to Southeastern Asia.
Dryobalanops lanceolata; to tall emergent tree. Flowering plant native to Southeastern Asia.
Eucalyptus denticulata; sometimes to high. Flowering plant native to Southeastern Australia.
Parashorea chinensis; tree up to tall. Flowering plant native to Eastern Asia.
Shorea mujongensis; emergent tree up to tall. Flowering plant native to Southeastern Asia.
Mexican elm ; it commonly grows from 20 to 40 m height and trunks 1 to 2.5 m in diameter at chest height. But in the rainforests of Nature reserveEl Triunfo, Chiapas, southern Mexico, have report a tree high, by other multiple sourses - trees up to, or high with stems up to 6 m in diameter. Flowering plant native to Southern North America.
Taiwania cryptomerioides; reported to heights of up to tall and with a trunk up to diameter above buttressed base. Conifer native to Eastern Asia.
Very tall tree species nearly height:
Ribbon Gum ;. Flowering plant native to Southeastern Australia.
Eucalyptus deglupta; tallest known living tree. Flowering plant native to Southeastern Asia.
