On the morning of January 31, 2019, the San Mateo County Parks Foundation met with County Arborist Dan Krug at Memorial County Park to send our GoPro up with the tree trimmers as they scaled a Douglas-fir. This was a rare opportunity to be able to share the view from the top of some of the tallest trees in the world. We hope you enjoy the video and our dialogue with Dan Krug. And special thanks to GoPro for sponsoring our camera!
SMCPF: Tell us the story of this tree, how tall it is, what kind and about how old?
Dan Krug: The tree being climbed in this video is a Douglas-fir, which stands 180 feet in height, and has a diameter of nearly 8 feet! Although we cannot know the precise age of this tree without extracting a core or through total tree removal, we can estimate its age based on the tree’s diameter, height, growth habit, surrounding vegetation, and the known age of similarly sized Douglas-fir trees. Considering these factors and possible growth influences, we estimate the tree’s age to be between 400 – 600 years.
SMCPF: Why are we trimming the tree today? Is this a fairly common event?
Dan Krug: San Mateo County Parks conducts routine visual inspection of trees within campgrounds and picnic areas to ensure they are properly managed for public safety in coordination with natural resource values, such as wildlife nesting. This Douglas-fir was identified as needing pruning due to its location within a campground.
The focus of this tree pruning project was to remove large broken and dead limbs in the upper canopy to make it more resilient during high wind storms. Additional weight reduction was also performed by removing select branch tips. Because this Douglas-fir is considered an emergent tree, meaning it is as tall or taller than most of the second-growth redwood in the immediate area, the additional weight reduction helps prevent wind damage and hopefully extends the life span of this mature Douglas-fir.
The Parks Department rolled out a new routine inspection program for camping and picnic areas in 2018, and as a result it is anticipated that more pruning of high value trees will occur over the next several years. This program provides a more systematic approach to how the Department evaluates trees for risk and natural resource and/or wildlife benefit. This Douglas-fir provides aesthetic benefits to park visitors as well as tremendous wildlife benefit. Our goal is to prune trees to extend their lifespan within the park setting.
SMCPF: It was fascinating to learn that all trees have shallow root beds and how the Douglas fir, redwoods and everything in nature competes. Can you tell us some fun facts about these trees that we might not know already?
Dan Krug: The root systems for the majority of tree species is more shallow than most people would believe. The average tree holds the greatest rooting volume within the top 18-36” of soil! Roots primarily develop at this depth for a number of beneficial reasons: It is where soil moisture, nutrients, and oxygen levels are at optimum concentrations for efficient uptake and use. Roots which develop higher in the soil will dry out earlier in the summer and have a greater likelihood of being damaged, and dying during times of drought. Roots which travel into deeper soil horizons will generally grow at slower rates as a result of the lower amounts of nutrients and oxygen available for uptake. However, a great benefit of a deeper root system is the potential for tapping into perennial water sources.
Studies have been conducted which show Douglas-fir roots will generally not grow further from the tree than the edge of its drip line – the reach of its branches and leaves. By comparison, the root systems of an old growth, or large secondary growth coast redwood has the rooting potential to cover an entire acre! The majority of these roots will still be in the upper horizons of soil (18-36”), but will extend from the tree in a vast network with the surrounding redwood forest.
SMCPF: As an Arborist, what is something you wish all park-goers knew about trees? Is there anything we should know to better preserve these trees for generations?
Dan Krug: Trees are living creatures, and like humans can be stressed by environmental influences. Limbs can be damaged or fail due to wind, heavy rainfall, lightning, or in some cases due to direct influences of drought. Just like humans, as trees age additional stress (environmental or human-caused) can result in increased susceptibility to disease or insect pests. In some cases disease will be introduced by insects, similar to West Nile Virus in humans. Whether in residential landscapes, along streets, in parks and especially in open spaces, trees deserve a healthy level of respect. Always be mindful of your surroundings when living or recreating near trees. Look up and be aware of what is above you and be mindful of how your actions may impact root zones. When camping or hiking, be on the lookout for broken or hanging branches. If you see it report it!
Humans are naturally curious about large trees. We often celebrate the majesty of large mature second and old growth trees wishing we could unlock their secrets of longevity and listen to the stories they would whisper. However, if we truly want to preserve these monolithic trees for future generations our means of appreciation will need to be modified. Although one person walking up to a tree and giving it a hug would not create an inordinate amount of impact, consistent and high visitation of the ‘biggest’ and most unique trees comes at a price. Compaction to the soil reduces water infiltration, prevents appropriate air circulation and contributes to the restricted development of new root growth. This means that the most ‘loved’ trees are literally being loved to death. The best way to observe these grand old trees is from a distance. Respect trail signs, fencing and always stay on posted trails to better preserve these trees for future generations to enjoy and marvel.
Dan Krug has been an International Society of Arboriculture certified Arborist for 12 years. As the County Arborist he helps Parks Department staff identify and understand tree physiology, structure and mechanics to determine the best management strategies for all of the Department’s unique tree communities. Not only is he a lover of trees, he has a deep-rooted passion for animals and all natural ecosystems.
San Mateo County Parks Foundation is a non-profit organization dedicated to inspiring people to care for, learn about, and enjoy our parks.