Old-growth redwood vs. second-growth redwood

When you visit the park, you may see the terms "old-growth" and "second-growth" being used in reference to the trees. Here is a little explanation of these terms along with an exploration of a science that deals with tree rings.

When you see lumber or other cut wood, you can look at the growth rings to tell how old the tree was. Each year, the tree lays down a new layer, or growth ring. The lighter colored wood is the spring growth and the darker wood of each ring is the summer growth. Drier climate produces slower growth and a denser wood during part of the year. These are the dark rings. One year's growth includes a light ring and a dark ring. If you count backward from the outer rings, you can tell the age of the tree. For this, it helps to know the year the tree fell. But you can tell how old a piece of wood is by counting the rings, even without knowing when it fell. Knowing when it fell will simply allow you to tell when it began growing. Counting the rings on old-growth wood is difficult because they are so densely packed together. Take a look at the photos below of old-growth wood. In the first, there were 50 years of growth between the two red markers on the ruler. That was 50 years of growth in ˝ inch!

old growth tree rings - photo by Kim A. Cabrera

In the next sample, there were 205 years of growth in 6Ľ inches. The tiny black tic marks on the left mark off 25 years each. The oldest known tree (stump) in the park is 2,200 years. This is the only one for which the growth ring count has been confirmed. Growth rate can vary due to changing conditions such as water, nutrients, and sunlight.

The scientific name for the coast redwood is Sequoia sempervirens. Sequoia was the Cherokee who invented the Cherokee alphabet. Sempervirens means "ever-living." This name fits the coast redwood well. One of the survival strategies of these trees is the ability to sprout from bud tissue called burl. If a tree falls, is logged, or the trunk is damaged, the burl can be triggered to start sprouting new growth. In this way, redwoods are able to reproduce and survive severe damage. The sprouts use the root system of the parent tree and are genetically identical. Who's to say that they are not the same tree? For example, a tree that is 2,000 years old falls in a windstorm. Not long after it falls, a sprout grows from its roots and lives another 2,000 years. Some would argue that the tree was a total of 4,000 years old. Now you know why redwoods earned the name "ever-living." Often, the stumps in old logged-over areas are ringed by smaller trees that grew from the roots of the parent tree. These rings are called "fairy rings."

To determine the age of a tree as large as a redwood, a cross section is required. Smaller trees can be sampled using a tool called an increment borer. This is a long tube that is drilled into the trunk of the tree to remove a sample core. The core must go through the center of the tree to get an accurate count of the rings. Counting the wide rings of a second-growth tree is easier than counting those of an old-growth tree. Sampling redwoods with an increment borer is difficult, if not impossible, due to the tremendous friction of drilling into something so large. So, the way to determine the age of a redwood is to get a cross section (or a wedge) and polish it up by sanding it to a very smooth surface. Only then are the tiny growth rings visible. Sometimes they are packed so closely together that a microscope is necessary to see them. The samples on this page were sanded with 200 grit sandpaper to make the rings visible. Even then, some of the finer ones are difficult to see.

If you look closely at the growth rings, you can tell which years had adequate rainfall and which years were drought years. Other events, such as forest fires, are often recorded in growth rings. If the tree survives the fire, it will continue to grow a new ring each year. Eventually, fire scars heal over. Once a scar has healed over, there is sometimes no sign of it on the outside of the tree. It is often not until the tree falls or is cut down that a cross section is cut and the fire scar is revealed.

Scientists can tell a lot about a tree's life by reading the growth rings. By dating the fire scars, the fire history of an area can be determined. The extent of each fire can be determined by sampling various trees in an area until you find the ones on the boundaries of the fire that were undamaged. This can be done without cutting down or killing the tree. In many areas, Native Americans stripped bark off trees to gather the sweeter cambium layer. The cambium of some trees was used as food. Reading tree rings can be a fascinating study. The study is called dendrochronology. Dendrochronologists learn about the climate in the region, the fire history and even the cultural history - all from reading tree rings.

So, what is second-growth wood? Second-growth usually denotes trees that grew in an area following logging or other disturbance that removed the old trees. The growth rings in second-growth trees are spaced much further apart. Second-growth redwoods often grow very fast. The trees in Burlington Campground were logged about 80 years ago. The second-growth trees there are now almost 200 feet tall. Given ideal conditions of water, sunlight, and nutrients, a redwood can grow as much as six feet or more a year! Because they grow so tall so fast, the growth rings are wide and spaced far apart.

This web site provided by Humboldt Redwoods Interpretive Association

You can help support the work of the H.R.I.A. (Humboldt Redwoods Interpretive Association) by becoming a member. Funds raised through memberships, endowments, and donations enable H.R.I.A. to develop displays, purchase equipment, sponsor research, publish interpretive literature, and also to fund the expansion of the Humboldt Redwoods State Park Visitor Center and its quality exhibits. A critical element in the success of the Association is its membership and endowment program. Individuals and families throughout the country have long supported the Association.