Conservation Arboriculture

Conservation arboriculture is neat.  It seems their are two main ideas behind conservation arboriculture.  The first, trees (especially urban trees) are of themselves complex ecosystems.  There are obvious and not so obvious examples of this.  Obvious examples are the vertebrates (ie. squirrels and birds) that use trees as their home and food source.  Then there are the not so obvious examples, like the invertebrates and fungi species that only a few may appreciate.  The bark alone can be home to arthropods, lichen, and fungi.   Taking an ecosystem view of a tree forces us as arborists to think of tree management differently.  For example, there are dozens of insect and fungi species that rely upon the dead wood in trees for survival, dead wood that an arborist would traditionally recommend for removal.  Conservation arboricultures teaches us their is an intrinsic value to these forms of life living in the tree.

The other idea behind conservation arboriculture, there is intrinsic value to very old trees.  Trees that we consider, due to structure or health issues, candidates for removal.  Some would call these ancient trees, and in places like the United Kingdom there are organizations dedicated to identifying and preserving these trees.  In my opinion the term 'ancient' is relative.  An ancient white oak may be 600 years old, while an ancient aspen may be 70 years old, but to me the idea is the same.  Older trees have a story to tell us, and the older they are, and the more perceived defects they have, the more likely they are to be the home of a variety of life.

As mentioned earlier conservation arboriculture challenges our tree management strategies.  Our first priority is always safety, but our question becomes how can we manage the perceived risk of our ancient urban/suburban trees while maintaining there vitality as a thriving multifaceted ecosystem?  In some cases it may be easy.  Moving a target or erecting a fence to keep people away from the fall zone.  In other cases it may be making the call on questionable reduction cuts, and leaving pieces of dead or dying branches in the tree that would normally be removed.  Would it be crazy to make reduction cuts on an already dead limb to reduce its chance of failure?  And still on our not so ancient trees, maybe we step back and let some deadwood build up or leave some smaller pieces in there.

This approach may not be for everybody, or every tree, but is an important idea to consider as we learn more about the trees we cherish.  Below is a link to an article written by Neville Fay which was run in Arborist News.  It is a real interesting read.
http://www.treeworks.co.uk/downloads/CONSERVATION_ARBORICULTURELearning_Review4-16-06-2011.pdf

The Angel Oak of Charleston, SC

Structural Root Decay: Another Reason to not be a Fan of High Nitrogen Fertilization

While browsing through Fungal Strategies of Wood Decay in Trees by Schwartze, Engels, and Mattheck, I came across an interesting piece of information.  The authors state decay progresses faster in wood with higher concentrations of nitrogen (N).  They then imply a correlation between high N fertilization and increased amount N in structural roots.  If these hold true applying fertilizers high in N, like many commercial tree and lawn companies, will actually speed up wood degradation by fungal decay agents and increase the risk of tree failure.

Now in cases where known root decay is present but not at the point where removal is considered necessary, some tree managers will recommend tree fertilization in an attempt to out grow, or at least stay pace with, the decay.  If the proper fertilizer analysis is not recommended we may actually be speeding up the decay process.  Custom fertilizing based upon the results of a soil sample is really the best practice when specific tree health goals are priority.

Mmmm nitrogen.

Lint Bug: The Aphid Wolf

Have you ever seen a lint bug?  Up until a few months ago I thought they were inconsequential, but cute,  little insects living on tree trunks.  I never really thought about what they ate, or their role in the ecosystem.

While doing research for another assignment I came across an article about lint bugs, and found they are brown lacewing larva.  As many of us know, green lace wing larva are voracious predators of many arthropod plant pests, and so are the larva of their brown winged cousins.  One web-site even referred to them as Aphid Wolfs.  They carry debris on their back for camouflage, and interestingly enough, some of that debris is actually body parts from their victims.  I might have a new favorite insect.

That gray pile of debris is a lint bug in a sea of  gloomy scale.

I snagged this close up picture from www.whatsthatbug.com

Red Maples: What a Bummer

By some twist of arboricultural fate I was charged with doing an 800 tree inventory this past week.  About 60% of the trees were.... you guessed it red maples.  Of these not one was with out co-dominate stems combined with some kind of defect.  Be it girdling roots, buried root collar, gloomy scale, or all of thee above.  Lets take a pictorial look at the mayhem.

So many co-dominate stems all coming from the same area on the tree.

A crack in the stem originating from co-dominate stems and leading almost to the ground.

Gloomy scales piled upon gloomy scales feeding upon there victim.

More sever cracks originating from co-dominate stems.

Of course a pictorial account of red maple defects would not be complete with out some impacted stem girdling roots.

Multiple upright branches with associated storm damage.

Left unattended since planting, these trees have become a maintenance nightmare.  Young tree pruning and proper planting are paramount, and this tree inventory is a prime argument.  To correctly mend these issues this home owners association will be looking at more than a $50,000 price tag.  Red maples, what a bummer right?

I Like Red Maples

Really I do, and at this time of year as their leaves are turning different shades of red, I can't help but think they are not as bad as many arborists make them out to be. Sure I've been known to role my eyes at thought of planting another 'October Glory,' but in October I wish I had one in my yard.

Red maples in the landscape get a bad wrap. They are produced in the millions by growers, and by the time they make it to retail there are layers of pot bound induced girdling roots, and the root flare is almost hopelessly buried. Lack of young tree pruning and disregard for proper crown structure leave them prone to co-dominate stems, included bark, and branch breakage. But aren't these true of many species by the time they make it in the landscape, and maybe we just notice it more on red maples because there is just that many more of them?

Red maples as a species are incredibly versatile. Native red maples grow through out the Eastern U.S. from low land swamps to rocky hillsides.  They are like a native super tree.  This species is planted in the landscape from Florida to British Columbia. Except for gloomy scale in the South East there are no more pest problems with red maple then with any other landscape tree. And even in the South it isn't uncommon to see a red maple planted to deep in a parking lot, with girdling roots, and covered in gloomy scale, and though not looking good, still surviving.  So take a break from hating on red maples and enjoy some fall color.

Trees Don't want to Die: A Musing

Trees have been around for millions of years, and they have found ways to survive outside in all kinds of conditions. We as humans try to understand why trees die and fail, and how to predict these events. Along the way our industry has come up with 'rules of thumb' to help us predict this. We hear arborists reference numbers like 30%, 33%, or 70% to quantify chances of tree failure or death, but trees break these rules on a daily basis.

There are 'high risk of failure' trees, condemned years ago, still standing today.  These trees have stood through wind and storms which have toppled other trees.  I've seen mature oaks with more than 50% of their trunk circumference damaged from the ground to 20-ft up the stem that are green and vigorous, and which have had enough energy to form callus tissue around the damage.

My view is becoming not, 'we have this much strength loss,' but instead 'we have this much strength left.'  And the same when it comes to the vascular tissue.  We must realize, of course, that some of this will be species, condition, and site dependent.  But, if a tree has 32% of it's root-flare compromised by decay is it a moderate risk of failure, while at 33% it is a high risk of failure?  Or, is what matters the 2 or 3 root flares not damaged are strong enough to support the weight of the tree even if even if all the other flares were compromised? How long will a tree with 50% of the stem girdled maintain a health canopy? 1yr, 5yrs, or 10yrs?  These are the questions I ask myself, because I don't want to remove a tree until it is necessary  and most of my clients feel the same way.

Notice how this tree has fallen completely over, and yet it continues to put out growth maintained by just a small portion of vascular tissue.

Tree Root Failure: A Discussion

Earlier this week an arborist friend and I were discussing root failure.  The discussion revolved around, if roots were severed, which direction would the tree fall.  His argument was the tree would fall towards the severed roots, while my argument was the tree would most likely fall away from the severed roots.  I believe my argument, the tree would most likely fall away from the severed roots is supported by a publication from the University of Georgia Root Strength  & Tree  Anchorage.

Root failure occurs in association with wind load and gravity.  'Beyond the root plate area, root tensile strength becomes more critical to anchorage.'  That is, as the wind blows roots on the wind ward side of the tree, the tension roots, are doing the most work.  Relatively speaking of course.  If these roots should be severed or damaged the tree would fail in on the opposite side of the force, or away from the root damage. Mattheck describes the roots on the tension side of the tree as forming holding knots in the soil.  Again, considering damage to the tension side of the tree will give a hint to where the tree may fall.

In addition to these references, I have also seen trees that are root decayed fall opposite the decay.  Now I could be wrong in my conclusion, but I think I make a pretty good case.  Some other interesting information from the UGA publication:

-'To summarize, a few large diameter and long roots can not provide effective resistance to failure.  It is in the proliferation of smaller roots in consolidation of the root plate which provides anchorage success.  (Stufka & Kodrik 2008)'

- 'Compression strength increases for a short distance from the stem base before declining with length.  Root compressive strength was found to be roughly the same for angiosperms and gymnosperms, but bending strength was found to be much greater in angiosperms. (Stokes & Mattheck 1996)'

-'Anchorage is concentrated in two general locations around a tree base: 1)  close to the stem base on the
leeward side and focused on several large diameter roots; and,  2) farther away from the stem base on the windward side in many, smaller, large surface area, near-surface roots.  (Danjon et.al. 2005)'

-'Windward roots have forces applied which are concentrated approximately 1.5X (one and one-half times) farther away from the stem base than leeward roots.  (Stokes 1999)'