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By urbanforestryassociates, Jun 6 2016 09:34PM

We got a new toy recently at UFA. Our Resistograph was getting a little outdated, so we decided it was time to upgrade our hardware and boy are we glad we did. If you're like most, you have never heard of a Resistograph, but it's basically our way of getting an idea of what's going on inside your tree. In the previous model, a thin drill bit entered the tree, driven by a Boshe cordless drill and the resistance on the torque of the bit was graphed on a long sheet of paper. When it encountered a hollow decay cavity inside the tree, the resistance dropped off and we could get an idea of how thick the wall of sound wood was. It was a good tool and aided quite a bit in our assessments, but the new model is really next level stuff.


First off, it's all digital. This lets us more precisely control the speed of the drill and keep more precise records. More importantly, it reads both feed resistance as well as torque. Don't let me lose you here, it's not that bad. The torque reading is what we had on the previous model and is just the resistance on the bit as it turns. This typically increases as we move through the tree as the hole gets clogged with sawdust and that can lead to possibly missing a cavity.


The feed resistance is what really sets the new model apart. This is how hard it is for the bit to move forward into the tree. Neither reading is a perfect indicator of decay, as there are specific conditions that can fool each one, but working together, we can get a much better picture of internal conditions. Specifically, the feed allows us to pickup pre-decay. This can tell us that a wall of wood that shows as 5" thick according to the torque reading is actually only 2" of sound wood and 3" of wood with pre-decay, which does not have any significant structural strength. This is a considerable difference and can make the difference between a safe tree and one that needs to be removed before it falls.


Hopefully your tree won't need our fancy new tool. But if it does, you'll be glad we have it.

By urbanforestryassociates, Nov 20 2015 04:25PM

We were recently subcontracted out to assist in the assessment of fire damaged trees on approximately 140 miles of County road in the Middletown area following the devastating Valley Fire. We are still hard at work supporting this tragic effort. As sad as it is for us to sign the death sentence for tree after tree, it has to be done. Ideally, we could leave all but the very worst of these trees for several years to see how they recover, but we don't set the schedule, the risk to the public would be too great and by then the FEMA money for the project would be gone. So for now, we do the best we can with the information we have, which can be misleading without a closer look.


Many of the trees marked for removal over the past few days have shown prolific sprout growth in their canopies, but this is far from a sure indicator the tree will recover to be a safe and healthy tree next to the road. We had to dig a little deeper into the trees, literally, to examine the cambium layer under the bark. This is the living, growing layer that protects the trees' heart and sapwood from pests and decay. If this area was killed by the heat of the fire over enough of the circumference around the base of the tree, that area will decay and the tree will become structurally compromised. The cambium is frequently killed even though it isn't physically burned but it will change from a fleshy, pink color, to a dry, pinkish brown. The removal of these types of trees, with bases "girdled" by fire damage but will healthy canopies that anger citizens. No one involved in the decision to removed these trees benefits from it. Quite the contrary.


Once a cell dies, it cannot come back to life. Likewise, once an area of cambium becomes scorched, it will remain dead and the wood beneath will begin to decay. For the majority of the trees, we also found early decay in the sapwood just inside the cambium in these scorched areas. The tree may still live with the fire damage, but that is only one factor that plays into the larger question of whether or not to keep the tree.

Driving North into MIddletown
Driving North into MIddletown
Deceiving Valley Oak to be Removed
Deceiving Valley Oak to be Removed
Early Decay in Sapwood
Early Decay in Sapwood
Living Cambium
Living Cambium
Dead Cambium
Dead Cambium
Flatheaded Borer in a Grey Pine
Flatheaded Borer in a Grey Pine
Urchin Gall Activity in a Blue Oak
Urchin Gall Activity in a Blue Oak
Valley Oak Regeneration
Valley Oak Regeneration
Burned Out Stump and Root Holes
Burned Out Stump and Root Holes
Burner Bus
Burner Bus

By urbanforestryassociates, Aug 31 2015 06:57PM

In a word, probably.


California's native coast redwood is an incredible species. It is the tallest in the world and the genus dates back to the Jurassic. Historically, Sequoias used to enjoy a much larger range that encompassed the majority of the northern hemisphere. Today, they are limited to northern coastal California and southern Oregon. This is due to the species' heavy dependence on water. Not just water, but a lot of water. You may be familiar with the romantic notion of tall, ancient redwoods sipping the fog from the sky in Humbolt County. Even if you are unfamiliar with this remarkable trait, you are undoubtedly aware that it rains a lot in the Pacific Northwest. Despite people knowing where these trees come from and what it is like there, they rarely translate that to what they need to provide for the tree in their front yard.


Generally, our clients are surprised to hear that their mature tree could require some supplemental irrigation, but if your redwood is peppered with brown foliage throughout the canopy, it is thirsty. So, does that mean you need to install spray emitters in the canopy to simulate fog? Not quite (although some misguided though well-intentioned people AND ARBORISTS do it). While it does appear to be true that they can harvest fog and rain through foliar absorption, it is not quite to the extent many believe and not exactly necessary.


There is a figure floating around the internet and many publications on redwoods that a mature tree can use up to 500 gallons of water on a hot summer day (picture those small swimming pools you can buy at Costco). So far, I have been unable to find a source but it is not as unrealistic a number as it might seem. There are studies showing large rainforest trees using upwards of 300 gallons, so 500 certainly seems possible. Regardless, this is not to say they need 500 gallons or even that they would want it, just that a huge, old tree could use that much if it were available.


Redwoods are bad at controlling water loss from their leaves (transpiration). It has been found that they commonly loose water during the night at a rate 20% of the maximum they might loose on a hot summer day! That might be a tough concept to get your head around, but it means they are loosing water through their leaves around the clock if there is low humidity. And that's where the fog really comes in to play. The high humidity of the fog found along the coast slows, stops and even reverses (to a limited extent) the water loss in the canopy.


So, would a lot of fog help your tree? Probably.


Should you artificially fog your trees? No.


If your tree is showing some brown foliage during the summer and it is not currently getting any water, give it some. Yes, we are in a drought and yes, water bills can be expensive but the average American uses between 80 and 100 gallons every day and water in Marin is not usually more than $0.01/gallon depending on your usage. Removing a mature redwood can cost as much as $10,000.


So skip a couple of flushes a day, buy a soaker hose, and protect your trees from the drought.

By urbanforestryassociates, Aug 14 2015 05:25PM

The upcoming el Niño seems to be all anyone can talk about in California lately and with good reason. With each passing day, weather forecasters seem to be getting more and more worked up about exactly how severe it could be, with the latest article dubbing it a potential "Godzilla El Niño". Follow the link for a really cool animation comparing it to the el Niño of '97 that is pretty alarming.


As with all things, we have to look at the el Niño in terms of what it means for the trees. Winter is always our busiest time for Tree Risk Assessments, even in mild winters. We are anticipating a calendar packed with One-Hour Inspections as well as emergency risk assessments following tree failures come December. Just think of all those trees that didn't fail during the past few mild winters.


An ounce of prevention is worth a pound of cure. If you are worried about your trees, please don't wait until the winds are howling, the ground is saturated and we (and the tree work companies) are slammed with work to give us a call. Not that we mind going out in the rain. If we were afraid of a little weather, we'd be in the wrong business.

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