Trees and their Associates

How often do we think about tree associates when we are working on an individual tree?  The sixteen chapters of the Arborists’ Certification Study guide cover many areas of Arboriculture, but there isn’t a chapter dedicated to tree associates.  The problem here is that we may be preconditioned by our training to think of trees as individual entities, rather than the interconnected organisms they are.

Some tree associates cause us problems (or perhaps, opportunities) as Arborists.  English Ivy, fungal root rots such as laminated root rot and invertebrates such as aphids spring to mind.  What about the beneficial, or symbiotic relationships trees have with other organisms?

We know that trees benefit greatly from fungal associations, and that mycorrhizae in the soil greatly increase the uptake of water and nutrients into trees.  However, it doesn’t stop there. The research of Dr. Suzanne Simard has shown that the mycelial networks carry information, including “threat signals” between trees.  Simard has also shown that symbiotic relationships exist between some tree species such as Douglas fir and paper birch, and that they exchange resources below ground, using the mycelial network as an intermediary.  For more information, watch this TED Talk.

Lichens are also important tree associates, and some species provide distinct benefits to trees.  Lobaria species are nitrogen-fixers, and when they shed from the upper parts of the tree, and fall to the ground, this nitrogen is made available for uptake into tree roots.

The last association I’ll mention is between salmon and trees.  Trees provide shade over streams and rivers, which benefit salmon as they need cooler temperatures to survive and thrive.  Young salmon leave their home streams, and swim to the ocean where they feed and grow much larger. They bring the gift of nitrogen back to those same streams, and that nitrogen is distributed into the forest after they spawn and die by other animals such as bears, ravens, and coyotes.  Historically, there was a correlation between the size of annual ring growth in trees and the size of the salmon run that year. The reduction in salmon populations has greatly affected this association, and its benefits. More details can be found in David Suzuki and Wayne Grady’s excellent book “Tree: A Life Story”, which details the life of a Douglas fir from seed to death.

Friends, I know I’m stretching here, and that my last example doesn’t have as many implications for arboriculture as for traditional forestry.  My argument is that we need to consider that trees don’t exist in a vacuum, even when we seemingly put them in one, such as a small tree-planting lawn between the street and sidewalk.  Their associations with birds, invertebrates, lichens, other epiphytes, and fungus still exist and have implications for the tree itself, and the wider environment.

Some questions we could ask when prescribing a treatment, bidding a job, or working on trees are:

  • How will this affect tree associates, and what are the implications of that?
  • Can I mitigate the impacts to associated organisms?
  • How can I communicate these associations and their implications to the customer?
  • How can my work include tree associates as well as trees?

Asking these questions might help us learn more, increase our scope-of-practice, benefit the customer and the environment, and provide a market opportunity.

signed, Phil.

Some Thoughts on Tree Risk

Early in January, two strong winter storms passed through Snoqualmie, where I work full-time. The second of these storms lasted about 20 hours, and at its peak, winds were 40-45 mph sustained with gusts in the mid 50’s. Beyond cleaning up tree failures and doing follow-up risk assessments, I spent a lot of time talking with scared residents. Many were concerned about the risk that trees pose to their families, and were convinced that swaying trunks were an indication that trees were about to fail.

In storms like these, there is a perceived high risk of trees. The actual risk for people (outside of our industry) is quite low, even during storms. As a juxtaposition to this, the perceived risk of driving a car or being on roads is low, whereas the actual risk is quite high.

Let me backup these assertions. A study by Thomas Schmidlin: “Human fatalities from wind-related tree failures in the United States, 1995–2007” discovered in that period, 407 deaths were caused by trees. By comparison, in the same time period, 416,268 fatalities were recorded on US roads by the National Highway Traffic Safety Administration. In other words, it seems that the average person is 1000 times more likely to die in a traffic accident than by a tree falling on them. However, I don’t think many of us think when we get behind the wheel: “Wow, I’m about to do a really risky thing”.

This is leading me to an ethics-check, and some questions I ask myself, that I’ll ask you too:

1) Do you communicate the benefits of trees, as much as the risks, to clients?

2) Do you have any way to put the risk of trees in perspective for the average person?

3) Are you focused solely on the trees when you risk-assess, or do other considerations creep in and affect your judgement?  Examples: The risk-tolerance of the client, the possibility that you may get paid to remove the tree, your own fear about being wrong in assigning a risk rating.

Culturally, we have accepted the risks that come from driving.  I think it’s part of our job as Arborists to help people understand the risk of trees, in balance with the benefits, and make sure there is a similar cultural acceptance of trees.

Our Extraordinary Chapter

First of all, let me say that it is a great honor to serve all of you. As my term starts, I have been thinking about how extraordinary our Chapter is, even within a global perspective of arboriculture. PNW-ISA is a large chapter with over 2,000 members. Only the Western chapter is larger. We are also unique because we are composed from parts of two countries, the United States and Canada.

We have a rich history of creativity, innovation, and leadership. Our members helped develop important ISA programs. ISA Certified Arborist, TRAQ, and its predecessor TRACE all benefited from our member's hard work. The first Tour-des-Trees was a PNW-ISA endeavor. Members rode 900 miles from Seattle to Oakland, California to sponsor tree research in 1992, and have continued to do so every year since.

I hope you feel that you are part of something special, and that you too can contribute towards the continued growth of our chapter.

We are trying something different this fall. Our brand new class, “After the Storm: A Symposium”, will be available for online remote attendance on December 5th. We hope that Chapter members in remote areas will benefit from this.

Be safe, keep learning, and don’t forget to enjoy the view.

Strong Foundation Today, Future Growth Tomorrow

Hello fellow PNW-ISA members, colleagues and friends.

I would like to start by saying thank you to all of our members, staff and board leadership team for your vision, passion and dedication towards furthering the professional practice of arboriculture not only in our region, but throughout the world. Since joining the Chapter and subsequently serving on the Board of Directors, I am continually impressed by the high quality professionals who serve this Chapter directly and further our mission through your daily work in the industry.

To serve our visionary members, the Board of Directors and staff have focused intently over the last few years on creating a strategic vision for the organization and building an effective board and staff team. These organizational pieces not only build a strong foundation for today, but prepare us for future growth tomorrow.

The Board recently evaluated this past year through the lens of our Strategic Plan and Key Performance Indicators and have some great news to share on all fronts.

  • Membership and revenues continue to grow at a sustainable pace. We are currently at over 2,000 active members.
  • Our number of certification and qualification credential holders continues to increase.
  • The Chapter attained a net profit to be invested in key organizational growth areas. In addition, we have improved our investment strategy to ensure chapter reserves capture sustainable and responsible market growth over time.
  • Our Education Program continues to grow, showing an increase in number of workshops, registration, locations, and an improved diversity of offerings all while showing a net profit that supports continued program and organizational growth.
  • The 2017 Annual Training Conference in Lynnwood met or exceeded our goals for attendance, sponsorship, profit, and attendee satisfaction.

In the theme of celebrating positive organizational performance and future growth, we are excited to see all of you at this year’s Annual Training Conference in partnership with the International Urban Forestry Congress in Vancouver, BC September 30 – October 3. This is an exciting opportunity for us to expand partnerships and broaden horizons both within and beyond our arboriculture industry. We hope to see you at various PNW-ISA events including Tree Academies, the Tree Climbing Championship, and the robust speaker slate during the conference. In addition, please join us at our Annual General Meeting on Wednesday morning to see our annual report, Chapter announcements, and participate in your board officer elections.

Again, thank you to all of our members, staff and board for your vision and leadership in this organization. I have been honored to serve as your President for the past two years and look forward to an exciting future ahead for PNW-ISA. Best wishes to you all and safe travels to Vancouver, BC.

Take care,

Exciting Transitions

Hello fellow PNW ISA members, colleagues and friends. This message to you comes with exciting transitions on the mind of your Chapter board and leadership team.

As you know, last Fall at ATC 2017 in Lynnwood, WA we said goodbye to several of our long-standing chapter leaders who helped produce a culture of friendship and teamwork on our Board that is critical to growing our organization and members. As you well know, change brings with it uncertainty of what the future holds – can we recruit new leaders to fill the voids left behind? What new ideas and opportunities lie ahead with new members on our team?

Following our first board retreat of 2018, I am proud to say that our team is alive and well! Our new board members and staff bring with them new perspectives, enthusiasm and a thirst for innovation. When you combine this renewed vision with the sound mission and strategic direction developed by the board, staff and membership in 2017, great things are soon to come!

It’s exciting to say that 2018 will be a year of renewal and new frontiers for our Chapter. In addition to continuing a high level of service to further arboriculture and educational opportunities for our members, we will see new ways to inform and connect with our membership in order to learn and better serve your needs. Finally, in building on this theme of new frontiers and innovation, we invite you to join us for our Annual Training Conference, which this year is a part of the International Urban Forestry Congress. To learn more visit the Conference website at

Until we speak again, best wishes to you all!

Take care,

In the Spirit of the Holiday Season: Thank You

In the spirit of the holiday season and building from the theme of our recent Annual Training Conference (ATC) in Lynnwood, WA, I would like to dedicate this message to thanking key members of our organization who are critical to our success in adapting to change. Read More "In the Spirit of the Holiday Season: Thank You"

Relationships are Our Foundation of Excellence

Hello fellow PNW-ISA members, colleagues, and friends. As we wrap up a busy and fruitful summer and look forward to fall, it’s time to celebrate another successful year together at our Annual Training Conference (ATC), September 24-27 in Lynnwood, WA. As I reflect back on this past year and look forward to the future, I think about recognizing the valued personal and professional relationships that make our Chapter great. Relationships with colleagues, mentors, and friends are what inspired me to join PNW-ISA and they are the foundation for our Chapter’s excellence in arboriculture and ability to foster a greater appreciation for our region’s trees. Read More "Relationships are Our Foundation of Excellence"

Strategic Planning Retreat Leads to Positive Changes

I’m very happy to welcome all of you to a bright green start to Summer! The result of our long and wet winter and subsequent wet spring has been thriving landscapes and natural areas throughout the Pacific Northwest. I’m proud to say that the majority of these landscapes and trees are fortunate to benefit from the world-class care provided by the arborists, tree care companies, consultants, educators, and federal/state/local urban forestry professionals of the PNW-ISA. Read More "Strategic Planning Retreat Leads to Positive Changes"

Celebrating 2016

Lance DavissonAfter a long, cold and wet winter in the Pacific Northwest, we are sure to welcome a spring complete with full rivers, thriving landscapes, and much needed warmth and sunshine. It’s hard to believe it’s already the beginning of spring 2017, but I’m sure you are all as ready as me to melt that snow and dry out those trails. It’s time to get back to biking and hiking our trails and floating those rivers in this beautiful place we call home.

As I sit down to spend a little time connecting with my fellow colleagues and friends in the Chapter, your Board of Directors has just returned from our winter strategic planning retreat in cool and rainy … and then sunny … Portland, Oregon. Read More "Celebrating 2016"

Thank You and Welcome

Lance_DavissonAs your Chapter President, I would like to start by thanking all of our members for your dedication and passion for furthering the profession of arboriculture in the PNW. It is a true pleasure to serve on your Board of Directors and work together with our staff team to sustain and grow a Chapter that builds excellence in best and safest practices, furthering our industry to a great and prosperous future. Read More "Thank You and Welcome"