Old-Growth: What it Means and Why it Matters
What Is The Definition Of An Old-growth Redwood Tree?
The term “old-growth” generally describes larger trees, usually at least 3.3 feet in diameter and over 200 feet tall, with certain features that only develop in older trees such as plate-like bark, larger branches, broken tops, platforms, dead tops, basal hollows carved out by fire, and reiterated crowns—meaning trunks off of trunks. Features like these, that typically take a coast redwood 200 years or more to develop, support many species and contribute to the tree’s resilience to fire, drought, and climate change.
Conversely, from a conservation standpoint, age alone is not always the best indicator of old-growth status. Although a redwood can live to be 2,000 years old, some may say 200 years old qualifies as “old-growth” status, however its possible for a redwood to live 200 years old without developing old-growth characteristics if it doesn’t have optimal conditions to reach its full potential. For example, a redwood tree in a city park may live to be 200 years old without developing old-growth characteristics like size because it does not have space to spread its roots 100 feet from its base, or it lacks neighboring redwoods roots to provide anchoring and nutrients, or fog is absent, and water cannot meet a redwood’s highest reaches.
photo by Ian Bornarth
What Is A Redwood Grove?
A redwood grove is a small grouping of redwood trees close together. Although there isn’t a specific minimum number of trees to qualify as a grove, it’s generally considered to be more than three trees and much smaller than a forest. Redwood trees often naturally occur in groves because redwoods sprout much more effectively from roots and basal burls than from their shockingly small cones. Circles of redwood—called “fairy rings” or “family circles”—are common sights in redwood forests and are formed by a following generation of trees that sprung from the roots of the parent tree. When grouped together, coast redwoods are at their most resilient and most capable of reaching their greatest heights and achieving old -growth features. Their roots are relatively shallow but can spread as wide as 100 feet from their trunk, intertwining with the roots of other redwoods to help anchor one another down in storms and share nutrients when needed. And according to newer research, this interconnectivity allows redwoods to communicate with each other and to share resources.
Another common term for a tree group is a “stand”. Stands are groups of trees of the same species, composition like the complexity of branches and canopies, size, and density. At Sempervirens Fund, we prioritize protecting stands of at least 10-acres in size to help maximize forest health and habitat for plants and wildlife. Groves are like small stands, but bunched together in closer proximity.
photo by T. Danh
What Is An Old-growth Redwood Grove?
An old-growth redwood grove is a small grouping of mature coast redwood trees with old-growth characteristics such as plate-like bark, larger branches, and reiterated tops or multiple trunks. An old-growth redwood grove is highly valued in conservation because the trees have developed individual characteristics that make them resilient and provide habitat for many other species, as well as having the support of the other redwoods around them sheltering, anchoring, and nurturing one another when needed. Not only do old-growth groves help one another thrive, combined they also provide exponentially greater habitat for plant and wildlife species.
What Are Second-growth Forests?
Many of the forests in the Santa Cruz mountains are second-growth forests. Second-growth refers to trees that grow back after they were cut down. In the late 1800’s and early 1900’s aggressive clear cutting took thousands of acres of redwood forests in the Santa Cruz mountains but enough time has passed that many resilient trees have regrown and started to recover since then. With proper land management and stewardship techniques, second-growth forests can regain invaluable old-growth characteristics—possibly in as soon as fifty to seventy-five years.
What Is An Old-growth Forest?
Old-growth forests are generally considered to be large groups of trees that have not been disturbed by human intervention like logging. An old-growth forest actually has trees of all ages–from saplings to giants–which are created over lengthy periods of time, from natural disturbance and recovery. At Sempervirens Fund, an old-growth forest is defined as an uneven-aged forest dominated by large, old trees that show signs of age and injury, like large branches, broken-tops, and damaged branches, and that contain these elements: a multi-layered canopy, large snags, and large downed trees.
Complex structure features like these are important in both individual trees and forest-wide. Diversity in tree ages creates a diversity of habitat conditions with multi-layered plant communities which provide food sources for animals and promote fog drip collection. Broken tops, fire scars, basal hollows (goose pens), large, reiterated limbs, and reiterated crowns all provide habitat for plants and animals. Even dead trees are integral in the forest. Large standing dead trees called snags are critical for wildlife like nesting owls and other birds. Large, downed trees, known as “large woody debris” or "coarse woody debris,” are shelter for amphibians, small mammals, reptiles, and invertebrates, and their slow decay on the forest floor releases important nutrients into the ecosystem. Some dead trees end up in streambeds, where they help improve water quality and provide habitat for amphibians and fish like endangered coho salmon to lay eggs. Diversity in tree ages and complex structures that can only develop over long periods of time contribute to increased species richness and abundance in old-growth forests.
Thanks to supporters like you, more than 8,000 acres of old-growth forests have been protected in the Santa Cruz mountains since Sempervirens Fund was founded in 1900. Today, there are still about 1,000 acres of unprotected old-growth forest in the Santa Cruz mountains. Together with supporters and partners we continue to protect and restore the redwood forests of the Santa Cruz mountains to become the old-growth forests of tomorrow for people and wildlife to enjoy for generations to come.
To read more about what makes redwoods magnificent, see our Redwood Facts and History page.
photo by Ian Bornarth.