Urban Forestry
This is an opportunity for you to
test your tree knowledge!
See if you can answer some of these common questions about trees:
What is the largest tree in the world?
What is the tallest tree in the world?
What is the oldest tree in the world?
How do trees grow?
What do trees eat (or do they actually "eat" at all)?
Can trees feel pain?
Are there male and female trees?
Why are trees important to us?
The World's Largest Tree
 The largest tree in the world (by volume and weight), and the biggest, most massive organism alive today, is called General Sherman, and is a giant sequoia (Sequoiadendron giganteum). It stands in Sequoia National Monument, in the western Sierra Nevada Mountains, California. This tree is 274.9 ft. tall (83.8 meters), has a diameter of 36.5 ft. at the base (11.1 meters), and is estimated to have a volume of 52,500 cubic ft. (1,486.6 cubic meters). In lumberman's terms, this one tree probably contains 630,000 board feet of lumber. (A board foot is 12 in. x 1 in. plank that is one foot long.) Luckily, since this tree is protected, it will never be cut down and we will never know for sure how much wood could be cut from it. It is approximately 2,200 years old, and is apparently still growing vigorously.
Trees of this species are also known as sierra redwood, or simply Big Tree, and are called Wellingtonia in Europe, where it was introduced over 150 years ago. Several specimens in England are already over 100 ft. (30.5 meters) tall. The Morris Arboretum has a few specimens which are only around fifty years old but are already at least 60 ft. (18.3 meters) tall.
In their native California, they are a high sierra tree, growing at mountain elevations between 4,500 and 8,000 feet (1,370 to 2,440 meters) above sea level. The average specimen reaches about 250 ft. (76 meters) at maturity, with a diameter at the base of around 15 ft. (4.6 meters). Although the growth rings are extremely close together, meaning the tree expands only slightly in girth each growing season, adult trees of this species are thought to grow faster than any other tree in the world: In just one year, the average giant sequoia tree gains enough wood to make a sixty-foot tall, three-foot diameter oak tree! The maximum lifespan of this species is thought to be about 3,000 years; that's a LOT of wood. This tree once grew in dense forests, which covered millions of acres. Now only about 2% of these forest stands are left; all the rest have been cut down for their lumber, and all of this logging occurred in the last 150 years.
Click here for photos and more information about the world's largest tree, you can visit the National Park Service's General Sherman Tree web site.
The World's Tallest Tree
 The tallest tree in the world is the Mendocino Redwood, which is a coast redwood (Sequoia sempervirens). It is 367.5 feet tall (112 meters), and it stands at the Montgomery Woods State Reserve near Ukiah, California. Even though the General Sherman tree is the largest tree on Earth, there are plenty of trees that are taller than it. The coast redwoods, which grow near the Pacific Coast in California and Oregon, commonly grow to heights of over 300 feet (91 meters)! This species grows taller than the giant sequoia, but they are more slender and not as massive. The Mendocino Redwood is estimated to be ten centuries old, and the height was measured using a laser in 1998; at this time it had a diameter of 10 feet, 4 inches (3.14 meters).
Coast redwood forests once occupied millions of acres along the Pacific coast between southern Oregon and southern California, but sadly they were heavily logged, and now only about 5% of the original trees are left.
It is worth mentioning that the Mendocino Redwood was not always the tallest tree on earth. In Australia, the mountain ash, a.k.a. Australian eucalyptus (Eucalyptus regnans) commonly reaches heights of 260 feet (80 meters), and is the tallest hardwood (broadleaf) tree in the world. A specimen at Watts River, Victoria, Australia, was originally 492 ft. (150 meters) tall, and is the tallest tree ever measured. It is thought that this species once grew even taller, perhaps up to 500 feet (152 meters) tall!
For photos and more information about the world's tallest tree, you can visit the Sempervirens Fund's facts page on coast redwoods. You can also read a great article about visiting the Mendocino Redwood. (Following these links will take you off of the Morris Arboretum's web site.)
back to the top
The World's Oldest Tree
 National Geographic - "The world's oldest known living tree, a conifer that first took root at the end of the last Ice Age, has been discovered in Sweden
, researchers say. "
The visible portion of the 13-foot-tall (4-meter-tall) "Christmas tree" isn't ancient, but its root system has been growing for 9,550 years, according to a team led by Leif Kullman, professor at Umeå University's department of ecology and environmental science in Sweden.
Discovered in 2004, the lone Norway spruce—of the species traditionally used to decorate European homes during Christmas—represents the planet's longest-lived identified plant, Kullman said.
The researchers found the shrubby mountain survivor at an altitude of 2,985 feet (910 meters) in Dalarna Province.
The tree's incredible longevity is largely due to its ability to clone itself, Kullman said.
The spruce's stems or trunks have a lifespan of around 600 years, "but as soon as a stem dies, a new one emerges from the same root stock," Kullman explained. "So the tree has a very long life expectancy."
Click here for the rest of the article
________
 The previosly known oldest tree in the world is the called the Methuselah Tree and it is a Great Basin bristlecone pine (Pinus aristata var. longaeva, also called simply Pinus longaeva). This wind-blasted, gnarled tree is 4,767 years old, and is located in California's White Mountains. Careful study of growth rings from a core sample yielded the tree's age. There are dozens of other trees in the same general area which are almost as old. There are several trees in Patriarch Grove at the Ancient Bristlecone Pine Forest, but scientists have not actually publicized the exact identity of Methuselah, in an effort to protect it. Most of the bristlecone pine trees of this high-altitude grove, which is over 8,000 feet above sea level, are actually quite small and stunted, and appear to be just barely alive.
For photos and more information about the world's oldest tree, you can visit an excellent web site devoted to the bristlecone pines. There is also a PBS web site about Methuselah, and a National Park Service page on the tree. (Following these links will take you off of the Morris Arboretum's web site.)
back to the top
How Trees Grow
 Trees grow upwards and outwards, adding new wood each year, expanding in volume. They add new tissue at the tips of their branches, which is called primary, or extension growth. They also expand outwards, adding another annual ring to the entire outer layer of the tree, which is called secondary, or annual growth. Once a branch appears somewhere, let's say ten feet above the ground, it stays there; it does not get carried up the tree as the tree grows, because that is not how trees grow (this is a popular misconception).
The typical tree starts as a seed, then devotes all of its energy to growing larger each year and protecting itself from its natural enemies. Some trees in a forest setting have to try to grow as tall as possible, as quickly as possible, because they must compete with other trees for valuable sunlight . When a tree reaches maturity, it starts flowering and producing seeds or fruit. A mature tree is not necessarily a full-sized tree, and different species of tree mature at different rates, in different conditions. Some trees, such as oaks, take several decades to mature, while others, such as some of the maples, can mature in only a few years. Similarly, some trees grow extremely slowly and live for a long time (centuries, even millenia), while others grow extremely rapidly and die after only a few decades. Plants are modular organisms, which makes them different from most of the animals. They can suffer extreme injury and still survive by adding new tissue (see "Do trees feel pain?"). If a tree is split in half or has its top chopped off, it can survive; most animals can not keep living after such an extreme injury. The rate at which a tree can grow also depends strongly on the conditions it experiences, such as the quality of the soil it grows in, the amount of sunlight and water it gets, and the temperature and altitude.
Trees can reproduce in a few other ways, besides simply sprouting from a seed. Some trees create clones of themselves by growing new stems from their roots. In this manner, one original tree can form a whole forest of trees; all of them are genetically identical clones, since they originated from one seed. Other trees can resprout after they fall over or after they have been cut down, because the roots store enough energy to grow new leaves. Still others can reproduce by layering, which is when a plant grows roots down from where a branch contacts the ground; if the part of the tree connecting the original roots to then new roots is severed or dies, there are two independent trees where before there was one! By cloning, resprouting, or layering, a tree could be potentially immortal!
Photo from Fun With Science: Trees and Leaves,
Rosie Harlow and Gareth Morgan, Warwick Press, 1991
Trees Eat... Sort Of
 Trees do not "eat" in the same sense that animals do. Although you can buy "plant food" and often people "feed" a tree's roots, there are not little hungry mouths underground, gulping down food for the tree. (There are some truly carnivorous plants, but they are a different story, and thankfully none of those is even close to tree-sized anyway, so we won't discuss them here...) Instead of chewing and swallowing food like we do, a tree absorbs the nutrients and water that it needs from the soil, though its roots. Then, using carbon dioxide from the air, and the raw materials it has drawn from the soil, it harnesses the energy of sunlight to create food for itself in its leaves! The process of making food by using sunlight is called photosynthesis, and all trees, as well as all other green plants, do it.
Photo from Fun With Science: Trees and Leaves,
Rosie Harlow and Gareth Morgan, Warwick Press, 1991
|
